conclusion pain analgesic in

.

1

8/5/2021 1

ANALGESIC IN ENDODONTICS

Dr. Neha KothariDepartment Of Conservative Dentistry And Endodontics

Introduction

Origin of pain

Analgesics

NSAIDs

NSAIDs in dentinstry

Opioids

Drug interactions

Analgesic strategy

Conclusion

8/5/2021 2

CONTENTS

Introduction

• Dental pain is one of the main reason for patient to visit Endodontist.

• Management of dental pain with anxiety during or after treatment remains a big challenge.

8/5/2021 3

Introduction

• “An unpleasant sensory and emotional experience associated with acute or potential tissusedamage or described in terms of such damage”. - IASP

8/5/2021 4

Introduction

• Type of pain:-

a. Nociceptive pain-

b. Neuropathic pain –

c. Peripheral sensitization –

d. Central sensitization-

e. Heterotopic pain-

Pain arising from activation of nociceptor

Pain arising as direct consequence of a lesion or disease affecting the somatosensory system

Increased responsiveness and reduced thresholds of nociceptors to stimulations of their receptive

fields.

Increased responsiveness of nociceptive neurons in the central nervous system to their normal or sub

threshold afferent input

Any pain that is felt in an area other than its true source

Referred pain

Central pain

Projected pain8/5/2021 5

Origin of pain

Odontogenic Non odontogenic

Pulp dentin complex

Periradiculartissues

Musculoskeletal pain

Neurovascular pain

Neuropathic pain

Pyschogenicpain

8/5/2021 6

.

2

DENTAL PAIN

“ The skill of the clinican is often judged primarily by their success or failure of pain control” – cohen, pathway of pulp

▪ Toothache is the most common pain entity occurring in facial region.

▪ Dental pain is usually acute in nature.

8/5/2021 7 8/5/2021 11

ANALGESIC• Analgesic is a drug that selectively relieves pain by

acting in the CNS or on peripheral pain mechanisms, without significantly altering consciousness.

• Analgesics relieves pain as symptoms without affecting its cause .

Opioid Non opioid

Antipyretic- analgesic or NSAIDS are commonly employed for dental pain because tissue injury and inflammation due to tooth abscess, caries, etc is the major cause of acute dental pain

8/5/2021 12

NON-NARCOTIC ANALGESICS

• Management of endodontic pain is multifactorial and directed at reducing the peripheral and central components of hyperalgesia through combined endodontic procedures and pharmacotherapy.

• Include – I) NSAIDs

II) Acetaminophen

Analgesic, antipyretic and anti-

inflammatory action

A drug of choice in treating

odontogenicpain

Act primarily on peripheral

pain mechanism

Don’t depress CNS

Don’t produce physical

dependence

Non Steroidal Anti Inflammatory Drugs

8/5/2021 13

CLASSIFICATION

➢A. Nonselective COX inhibitors (traditional NSAIDs) :-

1. Salicylates :- Aspirin

2. Propionic acid derivatives :- Ibuprofen, Naproxen, Ketoprofen ,Flurbiprofen.

3. Anthranilic acid derivative :- Mephenamic acid.

4. Aryl-acetic acid derivative :- Diclofenac, Aceclonfenac.

5. Oxicam derivatives :- Piroxicam , Tenoxicam.

6. Pyrrolo-pyrrole derivatives :- Ketorolac.

8/5/2021 14

7. Indole derivatives :- Indomethacin

8. Pyrazolone derivatives :- Phenylbutazone , Oxyphenbutazone.

➢ B. Preferntial COX-2 inhibitor :-• Nimesulide ,Meloxicam.

➢ C. Selective COX-2 inhibitor :-• Celecoxib, Etoricoxib, Parecoxib

➢ D. Analgesic – antipyretics with poor anti-inflammatory action:-1. Paraminophenol derivative :- Paracetamol .

2. Pyrazolone derivatives :- Metamizol, propiphenzone ..

3. Benzoxazocine derivative :- Nefopam.

8/5/2021 15

.

3

Prostaglandins

Mechansim Of ActionArachidonic Acid

Cyclo oxygenase

COX -1

ConstitutiveInducible

COX-2

Prostaglandins Thromoboxane

Mediate pain , inflammation ,fever

Hemostasis GI Mucosal protection

Non selective NSAIDs

Selective COX-2

Inhibitor

8/5/2021 18 8/5/2021 19

Beneficial Actions Due To PG Synthesis Inhibition

• Analgesia : prevention of pain nerve ending sensitization.

• Anti –pyretic.

• Anti- inflammatory.

• Anti – thrombotic.8/5/2021 20

Features of Non- Selective COX & Selective COX-2 Inhibitors

KD Tripathi 2nd Edition

8/5/2021 21

8/5/2021 22

Non selective COX inhibitors

8/5/2021 23

.

4

Salicylates

1. Aspirin :-• Aspirin is acetylsalicylic acid.

• It is the oldest analgesic- anti-inflammatory drug .

• Mechanism of action :-• Aspirin inhibits COX irreversibly by acetylating

serine residues ; return of COX activity depends on synthesis of fresh enzyme.

✓ Dosage:-

i. Anti inflammatory action – 3-5gm/day or 100 mg/kg/day

ii. Analgesic:- 0.3-0.6 gm (low dose)

8/5/2021 24

uses

Analgesic

Antipyretic

Acute rheumatic

fever

Rheumatoid arthritis

Post myocardial

infarction and post stroke

patients

8/5/2021 25

8/5/2021 26

Anti-inflammatory doses produce syndrome called

salicyalism- dizziness, tinnitus, reversible

impairment of hearing ,mental confusion

Acute salicylate poisoning

8/5/2021 27

More common in children

Serious toxicity seen at serum

salicylate levels > 50mg/dlTreatment :-• External cooling • I.V fluid with Na+,

K+, glucose.• Gastric lavage→

remove absorbed drug

• haemodialysis_→remove absorbed

drug

Contraindications

8/5/2021 28

Delayed or prolonged labour

Aspirin should be stopped 1 week before elective surgery , dental

extraction

Propionic acid derivatives

2. Ibuprofen-

8/5/2021 29

• Considered the prototype of contemporary NSAIDs. • Has a well-documented efficacy and safety profile.

• “mixed COX” inhibitor since it can inhibit both enzymes.

• Enters→ brain, synovial fluid, cross the placenta.

• Largely metabolized in liver by hydroxylation and excreted in urine as well as bile.

• Dose :- 400-600 mg TDS

.

5

8/5/2021 30

Pregnant women

Avoided in peptic ulcer patient

Analgesic and antipyretic.

In soft tissue injuries, tooth extraction , fractures: suppress

swelling and inflammation.

In rheumatoid arthritis, osteoarthritis and musculosketal

disorders.

Interaction Of Ibuprofen

8/5/2021 31

• Inhibit platelet function→ use with anticoagulants avoided.

• Decrease diuretic & antihypertensive action of beta-blockers, furosemide.

• 3. Diclofenac sodium :-

Aryl Acetic Acid Derivatives

8/5/2021 32

Mechanism :-

It inhibits PG synthesis reversibly.

Reduces neutrophils chemotaxis and superoxide production at inflammatory site.

Has good tissue penetrability→concentration in joints and other sites of inflammation it is maintained for longer period extending the therapeutic effect.

Dose -50mg BD ;75 mg i.m

USES

In tooth ache.

In rheumatoid and osteoarthritis.

Post- traumatic & post-operative inflammatory conditions → provide

quick relief of pain and wound edema.

Ankylosing spondylitis

SIDE EFFECTS

Epigastric pain

Nausea

Headache

Dizziness

8/5/2021 33

Oxicam derivatives

• 4. Piroxicam :-

8/5/2021 34

Long acting NSAIDs

Anti inflammmatory , good analagesic-

antipyretic actions.

Mechanism :- reversible inhibitory of COX.

It lowers PG concertationin synovial fluid and

inhibit platelet aggregation→ prolonging

bleeding time.

It inhibits inflammation in diverse ways , either :-

1.Decreases production of IgM rheumatoid factor

2.Reduces leucocyte chemotaxis.

• Doses :- 20 mg BD followed by 20 mg OD.

8/5/2021 35

1.As short term analgesic or as long term anti inflammatory drug in rheumatoid and osteoarthritis.

2. In acute gout.

3.Musculoskeletal injury.

1.Heart burn

2.Nausea

3.Anorexia

.

6

Pyrrolo-Pyrrole Derivatives

• 5. Ketorolac :-

8/5/2021 36

Novel NSAID – potent analgesic and anti inflammatory activity.

In post operative pain – equals efficacy of morphine but is free of opioids side effects .

Mechanism :- inhibits PG synthesis & relieves pain by peripheral mechanism.

Dose :- 10-20mg 6 hourly

Uses :-

1. In postoperative dental and acute muscloskeletal pain.

2. Also for renal colic, migraine , pain due to bony metastasis.

-For short term , moderate pain management :- given orally in dose of 10-20 mg 6 hourly.

-In postoperative dental pain kertolac has been rated superior to aspirin (650mg ) ,paracetamol (600mg ) & equivalent to ibuprofen 400mg .

-Continuous use for more than 5 days is not recommended

8/5/2021 37

Preferntial COX-2 Inhibitors

8/5/2021 38

• 1. Nimesulide :-

Sulfonamide derivatives

Weak inhibitor of PG synthesis

Used as short lasting inflammatory drug in patients with asthma, bronchospasn,

intolerance to aspirin

Dose – 100mg BD

Selective COX-2 Inhibitors:- ( Coxibs)

• Selective COX-2 inhibitor has advantage of inhibiting COX-2 without affecting COX-1 function.

• The introduction of selective inhibitors of COX-2 offered the potential for both analgesic and anti-inflammatory benefits and reduced GI irritation.

• COX-2 levels are increased in inflamed human dental pulp, and a COX-2 inhibitor is analgesic in patients with endodontic pain.

8/5/2021 39

They do not affect COX-1 function, do not inhibit platelet aggregation, but reduce PGI₂ production → exert prothromboticinfluence → enhance CV risk.

• Currently 3 selective COX-2 inhibitor are avaliable in india –

# Celecoxib

# Etoricoxib

# Parecoxib

• Rofecoxib and Valdecoxib have been withdrawn for increasing CV risk.

• Contraindicated – In Patient with history of ischaemic heart disease / hypertension/cardiac failure/ cerebrovascular disease

8/5/2021 40

• Selective COX-2 inhibitor should be used only in patients at high risk of peptic ulcer, perforation or bleeds.

• If selected → administered in the lowest dose for short period of time .

8/5/2021 41

.

7

Analgesic –Antipyretics With

Poor Anti Inflammatory

8/5/2021 42

Para-aminophenol derivatives

1.Paracetamol (acetaminophen ) :-

• One of the most commonly used drugs.

• Analgesic and antipyretic drug.

• Actions :- Central analgesic action →It raises pain threshold , but has weak peripheral anti inflammatory component.

• Normal dose :- safe (> 10g or >150mg/kg -adults)

• Higher dose :- causes liver toxicity→ acute liver failure

8/5/2021 43

• Mechanism :- Poor inhibitor of PG synthesis in peripheral tissues but more active on COX in brain.

• It has negligible ant inflammatory action.

8/5/2021 44

Uses :-

1. Best to be used as antipyretic.

2. As Analgesic for headache, musculoskeletal pain, toothache, → anti inflammatory action not required.

Nsaids In Dentistry➢NSAIDs are the mainstay for management of acute

dental pain.

8/5/2021 47

Mild-to-moderate pain with little inflammation :-paracetamol or low dose ibuprofen given.

Acute but short lasting pain or postextraction:- ketorolac, diclofenacsodum or aspirin given.

Gastric intolerance to NSAIDs :-paracetamolor etoricoxibgiven.

• 4.History of asthma or anaphylactoid reaction to aspirin :- CoX-2 inhibitors.

• 5. Pediatric patients :- Paracetamol, aspirin, ibuprofen.

• 6.Pregnancy :- Paracetamol, aspirin .

• 7.Hypertensive, diabetic ischaemic heart disease , epileptic :- drug interaction can occur with NSAIDs should be considered and physician consultation.

8/5/2021 48 8/5/2021 49

.

8

Drug Interaction with NSAIDs

8/5/2021 50

Diuretics : Diuresis

Beta-blockers : Anti-hypertensive effect

ACE inhibitors : Anti-hypertensive effect

Anticoagulant : Risk Of GI bleed

Alcohol: Risk Of GI bleed

Cyclosporine : Nephrotoxicity

Corticosteroids : Risk Of GI bleed

8/5/2021 51

Thank You

8/5/2021 52 8/5/2021 53

Good Morning !

8/5/2021 54

ANALGESIC IN ENDODONTICS

Part II

OPIOIDANALGESICS

.

9

Introduction • Opium – dark brown, resinous material

obtained from poppy ( Papaver somniferum).

8/5/2021 56

Two type of alkaloid

Phenanthrenederivatives

Morphine‘

Codeine

Thebaine

Benzoisoquinolinederivatives

Papaverine

Nosacapine

History • In 2nd century AD –Galen

introduced tincture of opium.

• Serturner, a pharmacist isolated morphine in 1806 and named it morphine after the Greek god of dreams Morpheus.

8/5/2021 57

Opioid receptors • Opioid exert their actions by interacting with

specific receptors present on neurons in the CNS & periphery tissues.

• Opioid receptors are divided into 3 types :-

• Kappa (κ)

• Delta (δ)

• mu (μ) 8/5/2021 58

μ₁

μ₂

κ₁

κ₃

• Opioids ligands interact with different opioid receptors as agonists, partial agonists or competitive anatagonists.

8/5/2021 59

Opiod Receptor Activation

Response Mu-1 Mu-2 Kappa Delta Sigma

Analgesia

Respiratory depression

Euphoria

Dysphoria

Decrease GI motility

Physical Dependence

Mania, hallucination

Opioid receptor transducer mechanisms

• All opioid receptors are G- protein coupled receptors situated on prejunctional neurons.

• Cause inhibotry modulation.

Decrease release of junctional

Transmitter such as

noradrenaline, dopamine,

GABA, glutamate.

8/5/2021 61

http://opioids.com/images/coleridge.html

.

10

Opioid receptor activation

Reduces intracellular cAMP formation

Opens K+ channels or supress Ca²+ channels

Neuronal hyperpolaization

Reduces availabilty of intracellular Ca²+

decrases neurotansmitte release by CNS and myenteric neurons

8/5/2021 62

Mainly by mu or delta receptors

Mainly by kappa

receptors

Opioids Classification

1. Natural opium :- Morphine

Codeine

2. Semi synthetic :- Diacetylmorphine ( heroin)

Pholcodeine

3. Synthetic Opioids :- Phenylpiperidines

Pentazcine

Methadone

8/5/2021 63

Morphine

8/5/2021 64

Principal alkaloid in opium

Considered as the Prototype Drug

Morphine is rarely prescribed orally because

most of the drug is metabolized in the liver

before reaching the systemic circulation

Freely crosses placenta and can affect the foetus

more than mother.

• It produces relief of pain in a dose that usually does not alter other functions of CNS.

• Indications :-• Moderate dose- relieves continuous , dull pain• High dose- relieves sharp, intermittent pain

caused by trauma

• Dose :- 10-15mg oral/i.m; 2-6 mg i.v; 2-3 mg epidural.

8/5/2021 65

Pharmacological actionsCNS:-

8/5/2021 66

Analgesic

•Strong analgesic- most effective in most kind of acute & chronic pain.

•Suppression of pain perception is selective ,without affecting other sensation or producing proportionate generalized CNS depression ( contrast GA _)

Sedation

•Drowsiness .

•Higher dose can produce sleep and coma.

•No anticonvulsant action.

Mood and subjective effects:-

•Has calming effect, feeling of detachment, lack of initiative, inability to concentrate.

•Patient in pain or anxiety & addictive perceive it as pleasurable

8/5/2021 67

.

11

Codeine

8/5/2021 68

• Methyl –morphine occurs naturally in opium.

• Most commonly used opioid.

• Combined with acetaminophen for oral administration.

• 60 mg of codeine has analgesic strength of 650 mg of acetaminophen or 200 mg of ibuprofen.

NSAIDsCodeine Analgesic activity increases.

Dose :-0.5-1mg/kg 4-6 hourly

Fentanyl• 80 to 100 times more potent than

morphine.

• Peak analgesic effect is reached in 5 minafter IV injection.

• Indications :-

• Used exclusively in Anaesthesia in injectable form.

• Respiratory depression alone as well in combination with Droperidol.

• Transdermal fentanyl→ for management of persistent chronic pain .

8/5/2021 69

DOSE: 100-200 µg i.v (FENT, FENDROP 50µg/ml)

Transdermal patch -25 µg/hr

Pethidine (Meperidine)• Equal analgesic efficacy to morphine & some

properties like Atropine.

• Indications :-

▪ As substitute to morphine .

▪ In pre anesthetic medication.

▪ In asthmatics patients→ causes less histamine release

• DOSE : 50-100 mg i.m/ orally

8/5/2021 70

Tramadol• Centrally acting analgesic .

• Weak agonist of all type of

opioid receptors.

• Indicated :-

▪ Moderate to severe pain.

▪ Short lasting pain due to diagnostic procedures, surgery etc.

▪ Chronic pain including cancer pain

8/5/2021 71

• Dose :- 50-100 oral/ i.m/slow i.v infusion(4-6 hourly).

• Injected i.v 100mg tramadol is equianalgesic to 10 mg i.mmorphine.

8/5/2021 72

Opioid In Dentistry

8/5/2021 73

Opioid analgesics

can be used

NSAIDs are less effective

• Narcotic (opioid) analgesics are extremely effective in reducing acute dental and postoperative pain.

• Hydrocodone, oxycodone, codeine, and occasionally meperidine are the narcotics used to treat dental pain.

.

12

• Gender is another interesting genetic factor associated with altered opioid responsiveness. Several studies have reported that women demonstrate significantly greater analgesia to kappa opioids than men.

8/5/2021 74

Opioid Dosing Regimens For Dental Pain

8/5/2021 75

Codeine should be the first to consider.Next opioid

to consider is

oxycodone

8/5/2021 77

Opioid

Most powerful analgesic

Relieve any type of pain

Act mainly at level of cortex, CNS

Produce addiction

NSAIDs

Mild analgesics

Relieve mild type of pain

Act mainly at levels of thalamus & hypothalamus

No addiction

Combination analgesics

• To enhance the analgesic benefit is to combine two (or more) drugs with different mechanisms of action.

8/5/2021 78

NSAIDs NSAIDs

Opioid Opioid

No pain relief

Opioid NSAIDsIncreased analgesia effect because the drugs act through dissimilar mechanisms

Analgesic Selection

• Acetaminophen-opioid combinations are the drugs of choice for moderate to severe pain when NSAIDs are contraindicated.

8/5/2021 79

Opioids (Codeine 60mg )

Paracetamol (600-650 mg)

Very effective analgesia in post-operative pain patients.

Doxylamine(5mg)

Increases analgesia effect

Flexible Plan

8/5/2021 81

.

13

Analgesic use in pregnancy or lactation

8/5/2021 82

American Geriatrics Society Recommendations for Choosing

Medications

• Use the least invasive route to give medication.

• Start low and go slow.

• Nonsteroidal anti-inflammatory drugs should be used with caution due to side effects.

• Opioid analgesics are effective for relieving moderate to severe pain.

8/5/2021 83

• Combination of an NSAID with acetaminophen provides effective pain control in both

postsurgical and postendodontic patients.

• Pharmacologic therapy is most effective when combined with nonpharmacologic therapy.

8/5/2021 84

Precautions and Drug Interactions

8/5/2021 85

NSAIDs includingthe COX-2-specific

agents

Allergy like reaction such as

urticaria, angioneurotic

edema, bronchial asthma and acute

hypotension

NSAIDs includingthe COX-1-specific

agents

Patients with bleeding disorders, platelet deficiency

and gastrointestinal inflammatory or

ulcerative disease

Conclusion • From a dentists’ perspective, we are able to

choose from a plethora of medications to provide patients with pain relief, but trying to judge the relative efficacy of analgesics is not easy.

• One must remember that the best means of managing pain is to remove the source of pain as quickly as possible.

8/5/2021 86

Refernces• Essentials of medical pharmacology –K.D. Tripathi

• Pathways of the pulp-cohen

• Endodontics –Ingle

• Australian dental journal medication supplement-2005

• AAE; A “3D” Approach for Treating Acute Pain;winter2015

• Current concepts of analgesics in dental pain management; Monika Kaushik, Atul Kaushik; Indian Journal of Dental Education; Volume 5 Number 2, April -June 2012

8/5/2021 87

.

14

• Drug Therapy in Dental Practice: Nonopioid and Opioid Analgesics;Daniel E. Becker, James C. Phero; 52:140–149 2005.

• Evaluation of NSAIDs for treating post-endodontic pain;Asystematic review;Andrea holstein, kenneth m. Hargreaves &richard niederman; 2002, 3, 3–13

8/5/2021 88 8/5/2021 89

Thank you

.

1

1


2

INTRODUCTION

CLASSIFICATION

DEFINITION

TYPES OF DEFECTS

SUMMARY OF CASTING DEFECTS

CONCLUSION

REFERENCES

C

O

N

T

E

N

T

S

Casting is the process by which

a pattern of a restoration is converted to a

replica in dental alloy.

The dental profession has used precision-type castings for the most part of

century.

Using the lost wax technique,

Taggart in 1907 developed a process for

making castings used in

restoration of prepared teeth.

3

Successful casting depends on accuracy &

consistency of technique.

Casting procedure is technique sensitive.

Small variations in investing or

casting can significantly affect the

quality of final restoration.

4

A casting defect is defined as an observable and

unplanned variation of a specification.

Errors in procedure often results in defective casting

, these defects are known as casting defects.

Identity of a particular casting defect is based on upon

specific shape , appearance, location and dimension or

profile of anomaly.

5

According To Philips (COOMBE)

Distortion

Surface roughness

and irregularities

Porosity

Incomplete or missing

detail

Discolouration

6

.

2

Roughness

Nodules

Fins

Incompleteness

Voids or porosity

Marginal discrepancy

Dimensional inaccuracies

7

According to Shillingburg

8

9 10

Any marked distortion of the casting is probably

related to the distortion of wax pattern.

Wax distortion most serious problem that can occur during

forming and removal of pattern from tooth or die.

Factors Affecting Distortion

Configuration of the pattern

Type of wax

Thickness of the wax pattern

11

▪When investment hardens

during manipulation, around it

or

due

expansion.

▪During spruing the pattern because of

the heat transferred to the pattern.

▪ Distortion is highest in thinner

portions of pattern.

12

.

3

as the thickness of the pattern

as setting expansion of the investment

Distortion

Distortion

13 14

Prevention

❖Proper

manipulation of wax

➢Minimal storage of

pattern➢Minimal carving force

& change in temp

➢Avoid occluding air during manipulation

15

➢The surface of a dental casting should be an

accurate reproduction of the surface of the

wax pattern from which it is made.

➢Excessive roughness or irregularities on the

outer surface of the casting necessitate

additional finishing and polishing.

16

• Defined as relatively finely spaced surface imperfections whose

height, width, and direction establish the predominant

surface pattern.

Surface roughness

• Refer to isolated imperfections such as

nodules, that don’t characterize the total

surface area.

Surface irregularities

17

• Improper technique can lead to a

marked increase in surface

roughness as well as to the

formation of surface irregularities.

18

Causes

Air Bubbles/

Voids/

NodulesWater Films

Rapid Heating Rates

Overheating

Prolonged Heating

Under Heating

Composition Of

Investment Casting Pressure

Foreign Bodies

Impact Of Molten Alloy

Temperature

Of Alloy

Liquid/

Powder Ratio

Pattern Position

Carbon Inclusions

.

4

19

➢The surface roughness of the casting is invariably greater

than that of the wax pattern from which it is made.

➢The difference is related to particle size of the investment

and its ability to reproduce the wax pattern in microscopic

detail.

➢Ratio of binder/ quartz influences surface texture (A coarse

silica causes surface roughness.)

20

Surface roughness

High L/P ratio

Excess wetting agent

Premature heating of investment

Prolonged heating or

over heating of the mold

Increased amount of

water

Large number of porositiesin investment

ROUGH CASTING

Excess L/P ratio

Prolonged heating of mold

Disintegration of gypsum bonded

investment

Walls of mold are roughened

Generalized casting roughness may indicate a breakdown

of investment from excessive burnout temperature.

22

Use of Vacuum Investing Technique

Use of wetting agent to reduce surface tension of wax pattern

Air dry the wetting agent as excess water will dilute investment, causing irregularities

Heat the ring for sufficient period of time to remove carbonaceous residue

Prevention

23

Vibrate during & after mixing

The mold should be heated gradually

Water/powder ratio should be accurate.

24

It is due to inadequate amount of molten metal

entering the mould.

The obvious cause is that molten alloy has been

prevented, in some manner, from completely filling

the mold

.

5

Incomplete

melting of

alloy

Incomplete

Dewaxing

Poor

Castability

Blocking

due to pre

solidification

in sprue

Blocking of

sprue due to

loose

investment

particles

Insufficient

Alloy

Too low

casting

force

Causes

26

Manifests in 2 forms

Rounded margins

Partial/No casting

▪ Incomplete wax elimination

during burnout leaving

behind CO that creates

strong reducing

environment.

Produces shiny round

margins

▪ Inadequate casting

pressure.

27

Inadequate

casting

pressure

Partial/No casting

➢Obstructed flow of molten alloy due to blockage of

ingate

➢High viscosity of molten alloy due to

insufficient heating

➢Inadequate casting pressure

➢Insufficient venting of air from mold creating

back pressure preventing filling of mold

28

Prevention

Proper time and temperature utilized during wax

burnout.

Proper casting force applied.

Proper burn out of wax pattern.

29

Casting may acquire certain discolouration due to

incorrect procedure which then becomes difficult to

remove

Carbon inclusions

Copper contamination

Sulphur contamination

Mercury contamination

Wax residues

30

Carbon Inclusions

➢Improperly adjusted torch flame.

➢Carbon containing investment or

crucible.

❖Carbon tends to get absorbed on

surface of alloy causing formation of

visible inclusions

.

6

31 32

Copper Contamination

If casting held by steel tongs and placed in pickling solution

Remnant copper creates galvanic cell

Copper deposition on casting metal

Permanent discoloration

Avoided by:use of steel tongs to hold casting during pickling

33

Sulphur contamination

➢Sulphur content of torch flame causes black casting

➢Prolonged heating of casting : disintegration of

investment & formation of sulphur compounds

Mercury contamination

➢Casting placed close to amalgam dies or

scrap

34

Occurs due to :

Overheating the investment above 7000c

➢Causes it to decompose liberating Sulphur or Sulphur

compounds.

➢They readily combine with the metals in alloy forming

a sulphide film.

➢Gives a dark casting which cannot be cleaned by

pickling.

Black Casting:

35

Solidifica-tion

• Localized shrinkage porosity

• Suck-back porosity

• Micro-porosity

Trapped Gases

• Pinhole porosity

• Gas inclusion

• Subsurface porosity

Residual Air

• Back pressure porosity

36

1. Solidification

Localized shrinkage porosity

▪ Linear contraction of noble metal alloys in changing

from liquid to solid – 1.25%

▪ Therefore continued feeding of molten metal through the

sprue must occur to compensate for casting shrinkage

i.e. shrinkage during solidification.(Insufficient feeding

causes porosity)

▪ It usually occurs if sprue solidifies before casting.

.

7

37

MAINLY OCCURS WHERE

SOLIDIFICATION OCCURS LAST.

38

➢May occur anywhere between dendrites

where last portion of casting solidify, mainly

bulkiest portion of casting, i.e. Sprue Pattern

Junction.

➢Occurs usually near Sprue-casting Junction.

39

✓Attach large reservoir in sprue of thickness more than

thickest portion of the pattern and as close as possible to the

pattern (1mm)

✓Flaring the sprue at the point of

attachment

✓Placing the reservoir close to the wax-pattern

40

Maintaining adequate flow of alloy.

✓Reducing the mold- melt temperature

differential.

Sprue attached at thickest portion and 45°

angulation.

41

Suck-back Porosity

➢Occur in fitting surface of crown near the

area of sprue.

➢Occurs often on occlusoaxial / incisoaxial

line angles that are not well rounded .

➢Even when the sprue is attached

at right angles to pattern.

42

Hot spot

Entering metal impinges on to mold surface at this point and

creates a higher localized mold temperature at this region

known as

“Hot Spot”.

CAUSES

.

8

43

➢By flaring the point of sprue attachment .

Prevention

➢Reducing the mold melt temperature

differential i.e. lowering the casting

temperature by about 300.

44

Micro-porosity

✓Occurs from solidification shrinkage

✓Generally present in fine-grain alloy castings

when solidification is too rapid for the micro

voids to segregate to liquid pool.

✓Premature solidification causes

formation of small, irregular voids.

✓Rapid solidification if the mold or

casting temperature is too low.

45

This defect is not detectable unless casting is

sectioned.

46

2.Trapped Gases

Pin Hole Porosity

➢Many metals dissolve or occlude gases in their

molten state .

➢On solidification of metal absorbed gases are

expelled resulting in pinhole porosities.

47

➢Both copper and silver dissolve O2 in large

amount in liquid state.

➢Molten platinum and palladium have a strong

affinity for hydrogen as well as oxygen.

48

Gas Inclusion

➢Related to entrapment of gas

during solidification.

➢More likely due to gases carried in

or trapped by the molten metal .

➢Characterized by a spherical contour.

Gas inclusion porosities are usually

much larger than pinhole porosity

.

9

49

Gas incorporated during casting procedure due to:

✓Use of poorly adjusted torch flame

✓Use of oxidizing flame.

Prevention

50

If alloy has been used before, these types of porosities

can be minimized by premelting gold alloy on a

graphite crucible or a graphite block and correctly

adjusting and positioning torch flame during melting.

51

➢Caused by simultaneous nucleation of solid grains

and gas bubbles at first moment that the alloy freezes

at mold walls.

Subsurface Porosity

❖Can be minimized by controlling the rate

at which the molten metal enters the mold.

52

3.Residual Air

Back Pressure Porosity

➢ Back pressure affects are caused by an

inability of air or other gases within the

mould to escape, making a way for alloy.

EXPLANATION:

As liquid enters the mould through the sprue,

the air trapped in mould is compressed at

the extremities which can exert back

pressure preventing the alloy liquid to occupy

this region.

53

Note : A casting which has been subjected to back

pressure is rounded at the edges and lacking in

detail.

Rounded edges due

to

back pressure

54

CAUSES OF RESIDUAL AIR

Dense Modern

Investment

Clogging of mold with residual carbon

Increased distance between pattern &

end of casting ring

Inadequate casting &

mould temperature

.

10

55

Prevention

Use of porous investment material

➢Increased distance between pattern &

end of casting ring .

Adequate liquid/powder ratio

56

57 58

59

✓An unsuccessful casting results in considerable

trouble and time.

✓In almost all instances, defects in castings can be

avoided by strict observance of procedures governed by

certain fundamental rules and principles

✓With the present technique, casting failures should be

the exception, not the rule.

➢ Kenneth J. Anusavice. Phillips’ science of Dental

Materials. eleventh edition, Saunders company.

➢ John M. Powers, Ronald L. Sakaguchi. Craig’s

Restorative Dental Materials. Twelfth edition, mosby.

➢ Operative Dentistry Modern theory and practice-Marzouk

➢ Rosensteil, Land, Fuzimoto: Contemporary fixed

prosthodontics:3rd ed.

60

.

11

61

T

H

A

N

K

Y

O

U

.

1

DENTAL COMPOSITE

S

1


2

Introduction

History

Composition

Classification of composites

Properties of composite

3

Types of composites

Recent advances of composite

Finishing and polishing

Sandwich technique

Conclusion

References

INTRODUCTION

• The search for an ideal esthetic material for restoring teeth has resulted in significantly improvements in esthetic materials and techniques.

• Composites and acid etch technique represent two major advances.

• Composite resins are a class of mature and well established restorative materials that have their own indication in anterior and posterior teeth.

4INTRODUCTI

ON

• Dental composites have continued to evolve with the development of smaller particle sizes, better bonding systems, curing refinements and sealing systems.

5

DEFINITION

Composite—

“In materials science, a solid formed from two or more distinct phases (e.g., filler particles dispersed in a polymer matrix) that

have been combined to produce properties superior to or intermediate to those of the individual constituents”

-Philips

6

.

2

DEFINITION

Dental Composite—

“Highly cross-linked polymeric materials reinforced by a dispersion of glass, crystalline or resin filler particles and/or short fibers bound to the matrix by a coupling agents”

7

• Esthetic consideration are primary factors for seeking dental treatment.

• In 1959, Skinner quoted-

“ The esthetic quality of a restoration may be as important to

the mental health of patient as the biological and technical qualities of restoration are to his physical or dental health”

8

HISTORY• In the middle of the 20th century, in 1873 Thomas Fletcher

introduced the first tooth- colored filing materials, silicate cement .

• In the early 1940s, German chemists developed the first acrylic resins, but it was not marketed until the late 1940s because of World War II.

• The first dental acrylic resin product was introduced in 1948 in United States.

9 10

1950s, adhesive dentistry began with acid-etch

technique.

In 1962, Bowen developed a new type of composite material-

bisphenol-A glycidyl dimethacrylate(bis-GMA) , a monomer that forms a

cross-linked matrix

INDICATION OF COMPOSITES

Class I, II, III, IV, V, VI

11

Core buildups Sealants and preventive resin restorationsEsthetic enhancement procedures Veneering metal crowns/bridgePeriodontal splinting Non carious lesions Composite inlays

Contraindications of composites

• Isolation

• Occlusion

• Subgingival area/root surface

• Poor oral hygiene

• High caries index

• Habits (bruxism)

• Operator abilities

12

.

3

ADVANTAGES

1. Esthetic

2. Conservation of tooth structure

3. Less complex when preparing the tooth

4. Insulative,having low thermal conductivity.

5. Used almost universally

6. Bonded to tooth structure

7. Repairable

8. No corrosion

9. No health hazard

10. Cheaper then porcelain

13

DISADVANTAGES

1. Polymerization shrinkage→ leading to gap formation.

2. Technique sensitive

3. Higher coefficient of thermal expansion

4. Difficult, time consuming

5. Increased occlusal wear

6. Low modulus of elasticity

7. Lack of anticariogenic property

8. Staining Costly

14

COMPOSITION

Resin Matrix

Coupling Agent Fillers

15

COMPOSITION

Activator-Initiator system

Pigments

Optical modifiers

Color stabilizers

16

Other Components

17

RESIN MATRIX

“A plastic resin material that forms a continuous phase upon curing and binds the reinforcing filler particles”

-Philips➢ Aromatic or aliphatic dimethacrylate monomers:-• Bis-GMA

• Urethane-dimethacrylate (UDMA)

➢ Diluent monomers• Triethylene glycol dimethacrylate (TEGDMA)

• EGDMA

• HEMA

18

.

4

RESIN MATRIX

19

Form highly cross-linked,Strong, rigid, and durable polymer

structures

• Bis-GMA• UDMA

Polymerization shrinkage → low as 0.9%

Highly viscous and are difficult to blend and manipulate

RESIN MATRIX

20

-Bis-GMA

-UDMA

-TEGDMA

- HEMA

Varying proportions of

diluent monomers are blended for incorporating enough filler

The greater theProportion of these

“diluting” monomers,

the greater thePolymerization

shrinkage and the greater the risk of

eventualleakage in marginal

gaps

RESIN MATRIX

• Alternatives to TEGDMA are-

- Monomethacrylates and

-Acrylates such as –hydroxypropyl methacrylate

-isobornyl acrylate.

-Bicyclic cyclopropyl-acrylates

• Bicyclic cyclopropyl-acrylates undergo a radical ring-opening polymerization under formation of a 1,5-substituted ring-opened unit, and are more reactive.

• Therefore exhibit lower volume shrinkage during their polymerization.

21

FILLER “Inorganic, glass, and/or organic-resin particles that are dispersed in a resin matrix to increase rigidity, strength, and wear resistance, to decrease thermal expansion, due to water sorption, and reduce

polymerization shrinkage”

-Philips

➢ Material used :-

1. Borosilicate “hard glass”,

fused quartz, aluminum silicate, lithium aluminum silicate

Barium and strontium are the

most common elements used in fill

22

FILLER ➢ Filler loading:- from 50 - 86 % by weight

-35 to 71 % by volume

➢ Particle size distribution of filler :-

• Packing fraction for close-packed spherical structures of uniform-size is approximately 74% by volume.

• On insertion of smaller particles among the larger spheres, the void space can be reduced.

23

FILLER ➢ Fillers can provide the following benefits:-1. Reinforcement of the matrix resin resulting in increased hardness and

strength.

2. Reduction in polymerization shrinkage:- Increased filler loading reduces curing shrinkage in proportion to filler volume fraction.

3. Reduction in thermal expansion and contraction:- Increased filler loading decreases the overall coefficient of thermal expansion of the composite because glass and ceramic fillers thermally expand and contract less than do polymers.

4. Reduction in water sorption, softening and staining

5. Improved workability by increasing viscosity:- more filler, the thicker is the paste.

6. Increased radiopacity and diagnostic sensitivity

24

.

5

FILLER Important factors with regard to fillers that determine the properties and clinical application of composite –

• Amount of filler added

• Size of particles and distribution

25

Filler Size

• Determines the surface smoothness.

• Larger particles = rougher surface

• Composites are most often classified by the filler size.

Filler Content

• As the filler content increases, the resin content decreases

• Hardness and abrasion resistance increases

COUPLING AGENTS

“A bonding agent applied to filler particles to ensure chemical

bonding to resin matrix”

-Philips

26

Filler particle

Resin matrix

BOND

COUPLING AGENTS

“A bonding agent applied to filler particles to ensure chemical bonding to

resin matrix”

➢ Types of coupling agent used:-

1. Organosilane such as gamma methacryloxy propyl trimethoxy silane.

2. Titanates

3. Zirconates

➢ Organosilane methacrylate groups form covalent bonds with the resin when it is polymerized, thereby completing the coupling process.

27

COUPLING AGENTS

➢Function of coupling agent:-

1. Bind filler particles to resin.

2. Improved physical and mechanical properties

3. Inhibit leaching by preventing water from penetrating along the filler-resin interface.

28ACTIVATION/INITIATI

ON SYSTEM

• Activator- “Source of energy used to activate an initiator and produce free radicals.”

• Initiator- “A free radical−forming chemical used to start the

polymerization reaction”.

-Philips

➢ Free radicals can be generated by chemical activation or by external energy activation (heat, light, or microwave)

29

CHEMICALLY ACTIVATED (SELF-CURE) RESINS

Chemically activated resins are supplied as two pastes,

1. Benzoyl peroxide initiator

2. An aromatic tertiary amine activator (e.g., N, N-dimethyl-p-toluidine)

30

Amine Benzoyl peroxide

Form free radicals, and addition polymerization is

initiated

.

6


31

➢ Advantages:-

1. Convenience and simplicity: no equipment needed, hazard-free

2. Long-term storage stability

3. Manipulation of working/ setting time by varying proportions

4. Degree of cure equal throughout material if mixed properly

5. Marginal stress buildup during curing is much lower than for photocured resins owing to relatively slower rates of cross-link formation


32

➢Disadvantage :-

1. During mixing it is almost impossible to avoid incorporating air into the mix, thereby forming pores that weaken the structure and trap oxygen, which inhibits polymerization during curing.

2. No control over the working time after the two components have been mixed. Therefore both insertion and contouring must be completed quickly once the resin components are mixed.

3. Aromatic amine accelerators oxidize and turn yellow with time—i.e., color instability.

PHOTO-CHEMICALLY ACTIVATED (LIGHT-CURE) RESINS

“Particle-filled resin consisting of a single paste that becomes polymerized through the use of a photosensitive initiator system (typically camphorquinone and an amine) and a light-source activator (typically visible blue light)”

- Philips

• Supplied as a single paste contained in a lightproof syringe.

• The free radical initiating system, consisting of a photosensitizer and an amine initiator.

33 34

Exposure to light in the blue region

Produces an excited state of the

photosensitizer

Interacts with the amine

Form free radicals that initiate

addition polymerization

PHOTOCHEMICALLY ACTIVATED (LIGHT-CURE) RESINS

• Camphorquinone (CQ) is a commonly used photosensitizer that absorbs blue light with wavelengths between 400 and 500 nm.

• Organic aliphatic amine initiator:- Dimethyl-amino-ethyl methacrylate (DMAEMA)

35


➢Advantages :-1. No mixing needed: thus low porosity, less staining, stronger.

2. No aromatic amine accelerator: thus greatly improved color stability.

3. “Command” setting (upon exposure to an intense blue light). This means that working time is controlled, at will, by the clinician.

4. Small increments of composite can be polymerized at a time allowing the use of multiple shades within a single restoration and accommodating for shrinkage within each increment as opposed to bulk shrinkage.

36

.

7


➢Disadvantages :-

1. Limited cure depth: necessary to build up in layers of about 2 mm.

2. Marginal stress buildup during curing is much higher than in self-cured resins. This is due to faster cross-linking and thus reduced time for chains to slide among themselves and relax interfacial stress build-up due to cure shrinkage.

3. Mildly sensitive to normal room illumination (thus a crust will form when exposed too long to an examination light).

4. Special lamp is needed to photoinitiate curing.

5. Cure is affected by additives such as ultraviolet absorbers for color stabilization, fluorescent dyes for clinical aesthetics, or excessive inhibitor concentration. 37

DUAL-CURED RESINS

“Dental composite that contains both chemically activated and light-activated components to initiate polymerization and

potentially overcome the limitations of either the chemical or light-cure systems when used alone.”

-Philips

• Consist of two light-curable pastes, one containing benzoyl peroxide and the other containing an aromatic tertiary amine accelerator.

• Formulated to set up very slowly when mixed via the self-cure mechanism.

38

DUAL-CURED RESINS

➢Advantage:-1. Assurance of completion of cure throughout, even if photocure is inadequate.

➢Disadvantage:-1. Porosity caused by the required mixing.

2. lessŠcolor stability than with the photocure resins.

3. Air inhibition and porosity.

➢ Indication :-Dual-cure materials are intended for any situation that does not allow sufficient light penetration to produce adequate monomer conversion—example, cementation of bulky ceramic inlays.

39

INHIBITORS:

• Inhibitors are added to the resin to minimize or prevent spontaneous or accidental polymerization of monomers.

• A typical inhibitor is butylated hydroxytoluene (BHT) used in concentration of 0.01 wt%.

• Inhibitors have a strong reactivity potential with free radicals.

40INHIBITORS:

• Inhibitors have two functions:

1. Extend the resin’s storage life

2. Ensure sufficient working time.

41

OPTICAL MODIFIERS

• Dental composites must have visual shading and translucency for a natural appearance.

• Shading is achieved by adding pigments usually metal oxide particles-Titanium dioxide ,Aluminum oxide in minute quantities(0.001-0.007%wt)

• These are added to make the translucency of filler particle similar to the tooth structure.

• Darker shades and greater opacities have a decreased depth of light curing ability.

42

.

8

CLASSIFICATION OF COMPOSITES

43

CLASSIFICATION

➢ SKINNER’S (10th ed) :-

1. Traditional composites (Macrofilled): 8-12µm

2. Small particle filled composite: 1-5µm

3. Microfilled composite: 0.04 – 0.4 µm

4. Hybrid composite : 0.6 – 1 µm

44

CLASSIFICATION ➢ANUSAVICE (11th edition)

45

CLASSIFICATION ➢ANUSAVICE (11th edition)

46

CLASSIFICATION ➢ STURDEVANT

Classification of composites based on the filler particle size

1. Megafill- in this one or two large glass inserts 0.5 to 2 mm in size are placed into composites at points of occlusal contact.

2. Macrofill- particle size range between 10 to 100 µm in diameter

3. Midifill - particle size range between 1 to 10 µm in diameter, also called traditional or conventional composites.

4. Minifill- particle size range between 0.1 to 1 µm in diameter

5. Microfill- particle size range between 0.01 to 0.1 µm

6. Nanofill- particle size range between 0.005 to 0.01 µm

47

CLASSIFICATION ➢Marzouk’s Generation:-

1. First Generation:- consists of macro-ceramic reinforcing phases in an appropriate resin matrix.

• Has highest mechanical properties

• High surface roughness

2. Second generation- consists of colloidal and micro-ceramic phases in a continuous phase

• Exhibit best surface texture

• Have unfavorable properties of strength and cofficient of thermal expansion

48

.

9

3 Third generation:- hybrid composite with combination of macro and micro colloidal particles

• Ratio of 75:25

• Properties compromises between first and second generation

4. Fourth generation:- hybrid type with heat cured, irregularly shaped, highly reinforced composite macro particles with reinforcing phase of micro ceramics.

• Technique sensitive

• Prerequisites for their successful use-

a) Concentration of dispersed micro ceramics must be equal in pre polymerized particles and in polymerizable organic matrix to ensure their uniform distribution

b) Bonding between continuous organic matrix and partially organic complex reinforcing particles should be strong cohesive bond

49

5. Fifth generation:- hybrid system with continuous resin phase with reinforced micro-ceramic and macro, spherical,highly reinforced heat cured compoiste particle.

• Improved workability

• Have good surface texture

6. Sixth generation:- hybrid types, continuous phase is reinforced with a combination of micro-cermaics and agglomerates of sintered micro-ceramics

• Exhibit highest percentage of reinforcing articles

• Exhibit best mechanical properties

• Wear and surface rexture similar to 4th generation

• Exhibit least shrinkage

50

CLASSIFICATION ➢ CRAIG:

1. TYPE I:

i. Class 1 – Macrosized particles – 8-25µ

ii. Class 2 – Mini size particles – 1-8µ

iii. Class 3 – Micro size particles – 0.04-0.2µ

iv. Class 4 – Blend of macro and micro – 0.04-10µ

2. TYPE II

i. Class 1: Macrosized 10-20µ (organic particles in unreinforced resin matrix).

ii. Class 2: Macrosize unreinforced particles 10- 20µ (organic in reinforced resin matrix 0.04- 0.2µ organic)

51

CLASSIFICATION

➢ Based on polymerization method:

• Self-curing

• UV light curing

• Visible light curing

• Dual curing

52

CLASSIFICATION

➢ Matrix Classification System:-

• Bis GMA

• UDMA

• Combination of both

53

CLASSIFICATION

➢ Based on inorganic loading:-

• Heavy filler material :- 75%

• Lightly filler material:- 66%

➢Based on consistency:-

• Light body:- flowable

• Medium body:-homogenous microfills,macrofills, midfills.

• Heavy body:- packable hybrid

54

.

10

PROPERTIES OF RESIN-BASED COMPOSITES

55


1. DEGREE OF CONVERSION (DC):-

“Measure of the percentage of carbon-carbon double bonds that have been converted to single bonds to form a polymeric resin”

• The higher the DC →the better the strength, wear resistance.

• DC within resins does not differ between chemically activated and light-activated composites containing the same monomer formulations as long as adequate light curing.

56


1. DEGREE OF CONVERSION (DC):-

• Conversion of the monomer to a polymer depends on several factors:-

a) Resin composition,

b) Transmission of light through the material,

c) The concentrations of sensitizer, initiator, and inhibitor.

57


2. Toughness :-

• The strength of composites is highly dependent on the ability of the coupling agent to transfer stresses from the weak matrix to the strong filler particles.

58

Cannot absorb

stresses in the matrix

Weakens composite


2. Toughness :-• If the interfacial bond is weaker than the matrix, a process of “crack blunting”

occurs.

59

a void or tear opens up in frontof the advancing crack because of

the stresses that the weakbond experiences

this void is perpendicular to thepropagating crack


3. Water sorption & solubility -:

• Water is absorbed preferentially into the resin component and the water content is therefore increased when resin content is increased. .

• Expansion with uptake of water relieve polymerization stresses.

• Water solubility -0.01 to 0.06 mg/cm2.

• Water sorption is greatly reduced in composites as compared to acyrlicresin due to the Bis –GMA and lower amount of resin .

• Inadequately polymerized resin→ greater water sorption & solubility.

60

.

11


3. Water sorption & solubility :-

• If the stress is greater than the bond strength, the resulting debond is referred to as HYDROLYTIC BREAKDOWN.

• Microfills and flowable have greater water sorption.

61


4. Thermal properties-:

• CTE of composite is approximately three times higher than normal tooth structure.

• This can be reduced by adding more filler content.

• Microfill composites show more cofficient of thermal expansion because of presence of more polymer content.

62


5. Wear (volume loss by abrasion and other mechanisms):-

• Wear rate differences of 10 to 20 μm/year for posterior composites is studied, well this wear rate still amounts to 0.1 to 0.2 mm more than enamel over 10 years.

• Two principal mechanisms of composite wear:-

A. Two-body wear:- based on direct contact of the restoration with an opposing cusp or with adjacent proximal surfaces. It is related to the higher force levels exerted by the opposing cusp or forces transferred to proximal surfaces.

B. Three-body wear:- simulates loss of material in non-contacting areas, most probably owing to contact with food as it is forced across the occlusalsurfaces

63


5. Wear (volume loss by abrasion and other mechanisms):-

• The loss of material caused by direct wear in areas of tooth-to-tooth contact appears to be greater than that of three-body abrasion by food in non-contact areas.

• Composites with smaller filler particles size (1 μm or less), high in concentration, and well bonded to the matrix are the most resistant to wear.

64PROPERTIES OF RESIN-BASED

COMPOSITES

6. Curing shrinkage and shrinkage stress:-

• “Curing shrinkage arises as the monomer is converted to polymer and the free space it occupies reduces.”

• The polymerization shrinkage and resultant stress can be affected by:-

i. Total volume of the composite material,

ii. Type of composite,

iii. Polymerization speed,

iv. Ratio of bonded/nonbonded surfaces or the conguration of the tooth preparation (C-factor).

65

Configuration factor / C factor

• “It is the ratio of bonded surfaces to the unbonded surfaces in a tooth preparation”

• Higher the C-factor, greater is the potential for bond disruption from polymerization effects.

66

.

12

67

Configuration factor / C factor

• Class I restoration with C- factor of 5 ( five bonded surfaces,

one unbonded surface) is at much higher risk of bond

disruption associated with polymerization shrinkage ,

particularly along the pulpal floor

68

Reduction of shrinkage stresses

1. The slower curing rate of chemical activation allows a larger portion of the shrinkage to be compensated by internal flow among the developing polymer chains before extensive cross-linking occurs.

2. Reduction in volume contraction by altering the chemistry and/or composition of the resin system.

69

Reduction of shrinkage stresses

3. Clinical techniques:-

a) Incremental Buildup :-

• A layering technique in which the restoration is built up in increments, curing one layer at a time, effectively reduces polymerization stress by minimizing the C-factor.

• Thinner layers reduce bonded surface area and maximize non-bonded surface area, thus minimizing the associated C-factor.

70Reduction of shrinkage

stresses3. Clinical techniques:-

b) Soft-Start, Ramped Curing, and Delayed Curing:-

• Soft-start technique, whereby curing begins at low light intensity and finishes with high intensity

• It allows for a slow initial rate of polymerization and a high initial level of stress relaxation during the early stages and it ends at the maximum intensity once the gel point has been reached.

71 72

Soft-start

.

13

73 74

Thank You

75

GOOD MORNING TYPES OF

COMPOSITES

76CONVENTIONAL

COMPOSITES

• Also known as – Traditional or macrofilled composites.

• Filler:- finely ground amorphous silica or quartz.

77

CONVENTIONAL COMPOSITES

• The average particle size of conventional composites was approx

8-12 um.

➢ Filler loading:- 70-80% by wt, 60-70% by volume.

➢ Indications:-

• Used in class II and IV restorations.

78

.

14

CONVENTIONAL COMPOSITES

➢ Disadvantages:-

1. Because of the relatively large size and extreme hardness of the filler

particles, conventional composites typically exhibit a rough surface texture.

2. More susceptible to discoloration from extrinsic staining

3. Higher amount of initial wear at occlusal contact areas.

79

MICROFILLED COMPOSITES

• Introduced in the late 1970s as "polishable" composites .

• These materials were designed to replace the rough surface characteristic of conventional composites with a smooth, lustrous surface similar to tooth enamel.

• Filler:- colloidal silica particles, prepolymerized particles comprised of resin and fumed silica

80

81


• Filler size:- 0.04-0.4 um.

• Filler loading:- 35-60% by weight.

➢ Indications:-

1. Aesthetic restoration for anterior teeth.

2. Class III, V restoration.

82


➢ Advantages :-

1. Smooth ,polished surface in the finished restoration

2. Less susceptible to discoloration.

3. Low modulus of elasticity, better protecting the bonding interface.

4. Clinically very wear resistant.

83

MICROFILLED COMPOSITES➢ Disadvantages:-

1. Low tensile strength.

2. Decreased Fracture resistance.

3. Radiolucent

4. Polymerization shrinkage.

5. Physical and mechanical properties are generally inferior to those

of traditional composites- greater water sorption,

- higher coefficient of thermal expansion.

84

.

15

• Diamond burs, rather than fluted tungsten-carbide burs, are recommended for trimming microfilledcomposites so as to minimize the risk of chipping.

85

Scanning electron micrograph of polished surface of a conventional

composite (x300).

Scanning electron micrograph of polished surface of a microfill

composite (x300).

HYBRID COMPOSITES

• In an effort to combine the favorable physical and mechanical

properties characteristic of conventional composites with the

smooth surface typical of the microfill composites, the hybrid

composites were developed.

• Hybrid composites are formulated with mixed filler systems

containing both microfine (0.01 to 0.1 μm) and fine (0.1 to 10

μm) particle fillers

86

HYBRID COMPOSITES

• Filler:- colloidal silica and ground particles of glass containing heavy metals.

• Filler loading:- 75-85% by weight.

• Filler size:- 0.4-1 um.

• Indications :-

1. Restoring incisal edges and small non-contact occlusalcavities.

2. Anterior restorations, including class IV sites.

87

HYBRID COMPOSITES ➢ Advantages :-

1. Smaller microfiller sizes increase the surface area → increases the viscosity.

2. Because of the relatively high content of inorganic fillers, the physical and mechanical characteristics are generally superior to those of conventional composites.

3. The presence of sub-micrometer sized microfiller particles interspersed among the larger particles provides a smooth "patina-like" surface texture in the finished restoration

88

HYBRID COMPOSITES

➢Disadvantages :-

1. Resins lose their high polish over time with the development of a rougher surface, reducing their suitability for esthetically demanding cases.

89

FLOWABLE COMPOSITES • A modification of the small-particle composite and hybrid

composite results in the flowable composites, which have become popular since 1995.

• Resins typically have a lower viscosity through a reduced filler loading, which enables the resin to flow readily, spread uniformly, intimately adapt to a cavity form, and produce the desired dental anatomy.

90

.

16

FLOWABLE COMPOSITES • Filler size :- 0.6-1 um.

• Filler content :- 30-55 % by wt.

➢Indications :-1. Class I,II,III,IV,V restorations

2. Pit-and-fissure sealants

3. Marginal repair materials,

4. Infrequently, as the first increment placed as a liner under hybrid or packable composite.

5. Core build up

91

Because they can flow into small crevice defects along restoration margins, some dentists refer to flowable resins as

“DENTAL CAULK.”

FLOWABLECOMPOSITES

➢Advantages :-

1. Ease of use.

2. Favorable wettability.

3. Less sticky during handling than microfills and hybrids.

➢Disadvantages :-

1. Low strength

2. Exhibit much higher polymerization shrinkage.

3. Higher susceptibility to wear

92

PACKABLE COMPOSITES

• Also known as “Condensable composites.”

• Based on new concept called PRIMM ( polymer rigid inorganic

matrix material).

• Packable composites are designed to be inherently more viscous

to afford a "feel" upon insertion, similar to that of amalgam.

93

PACKABLE COMPOSITES

94

Packable/condensable characteristics are derived from the inclusion of elongated, fibrous filler particles of about

100 μm in length and/or rough-textured surfaces or branched geometries that tend to interlock and resist flow

It causes the uncured resin to be stiff and resistant to slumping yet moldable under the force of

amalgam condensers (“pluggers”).

PACKABLE COMPOSITES

• Packable Composites were development in an attempt to accomplish two goals:

1. Easier restoration of a proximal contact, and

2. Handling properties similar to amalgam.

95

NANO COMPOSITES • Also known as “Nano-composites or Nanohybrid Composites”.

• Sir Richard Feynman in 1959 coined the term like “nano” .

• This discovery was a landmark for advances in dental composites. The introduction of nanotechnology led to the discovery of nano-filler particles.

• Nanofills and nanohybrids are the two different types of more commonly available nano-composites.

96

.

17

NANO COMPOSITES 1. Nanofill composites :-

• These contain nanometer sized particles (1-100nm) throughout the resin matrix.

• Contains high filler load in order to obtain strength and wear resistance similar to that of microhybrid composite resins.

• The nanofill type of composites, are formed by a combination of:

(a) Nanomers, which are nanosized mono-dispersed, non-aggregated silica filler particles in the size range of 20-75nm and

(b) Nanoclusters, which are agglomerations of combination of zirconia-silica and silica nanomeric particles.

97

NANO COMPOSITES 2. Nanohybrids Composites :

• Consists of large particles (0.4-5 microns) with added nanometer sized particles. Thus they are hybrid and not true nanofilledcomposites.

• The surface of nanohybrid becomes gradually dull after a few years of clinical service because of its large size particles.

98

NANO COMPOSITES

• Various commercially available brands of nanocompositesinclude:-

1. Filtek Supreme XTE Universal Restorative (3M ESPE),

2. Premise (Kerr/Sybron, Orange, CA),

3. IPS Empress Direct & Tetric N-Ceram (both Ivoclar Vivadent).

99

RECENT ADVANCEMENT IN

COMPOSITES

100

ANTIBACTERIAL RESIN COMPOSITES

• Composites that offer antibacterial properties are promisingsince several studies have shown that greater amount ofbacteria and plaque accumulate on the surface of resincomposite than on the surface of other restorative material /enamel surface.

• In resin composite materials the addition of an antibacterialcomponent can be achieved through modifications made to thefiller particles or the resin matrix

• Imazato et al 1994 incorporated anon-releasing newlysynthesized monomer MDPB with anti-bacterial properties intoresin composite

101


• The strategies that have provided resin composites possessing antibacterial activity can be divided into two main groups:

1. Released soluble antimicrobial agent or,

2. Stationary non-released antibacterial agent

102

.

18


• A soluble agent is gradually released over time, discharging the antibacterial agent from the bulk of the material.

• Although an antibacterial effect is achieved, the agent’s

release has several disadvantages:

1. An adverse influence on the mechanical properties of the base material,

2. The release of the agent possibly generating a porous structure,

3. Time limited efficacy, and

4. Possible toxicity to the adjacent tissues given that the rate of diffusion can be difficult to monitor

103

ORMOCER• Ormocer is an acronym for “organically modified ceramics”.

• First time introduced in 1998 by Dr Herbert Wolters.

• Ormocer materials contain inorganic-organic co-polymers in addition to the inorganic silanated filler particles.

• Organic, reactive monomers are bound to an inorganic -Si-O-Si-network.

104

105

ORMOCER• Ormocers basically consist of three components – organic and

inorganic portions and the polysiloxanes.

• The proportions of those components can effect the mechanical, thermal and optical qualities of the material:

1. The organic polymers influence the polarity, the ability to cross link, hardness and optical behavior.

2. The glass and ceramic components (inorganic constituents) are responsible for thermal expansion and chemical stability.

3. The polysiloxanes influence the elasticity, interface properties and processing

106

ORMOCER➢ Indicated in-

• All types of restorations, for esthethic veeners, repairing porcelain or acrylic facing.

➢ Contraindicated in –

• Patients with known allergy to methacrylates, phenol, TEGDMA.

➢ Commercial name-

• “Denite” and “Admira,” Voco ;

• “Ceram-X,” Dentsply

107

108

.

19

COMPOMERS• Polyacid Modified Composite Resin is known as COMPOMER.

• As proposed by Krejci (1992), the acronym ‘ compomer” was

created by combing the words composite and glass ionomer.

COMPOSITE + GLASS IONOMER = COMPOMER

109

COMPOMERS• COMPOSITION :-

• Resin matrix: Dimethacrylate monomers with two carboxylic

group present in their structure

• Filler: Reactive silicate glass containing filler

• Photoinitiators and Stabilizers

• There is no water in composition and ion leachable glass is

partially silanized to ensure bonding to matrix

110

COMPOMERS➢ Indication:-

• Pit and fissure sealant

• Restoration of primary teeth

• Liners and bases

• Core build up material

• For class III & V lesions

• Cervical erosion / abrasion

• Repair of defective margins in restorations

• Sealing of root surfaces for over dentures

• Reterograde filling material.

111

COMPOMERS

➢Contraindications:-

• Class IV carious lesions

• Large areas of labial surfaces

• Class II cavities where conventional cavity is prepared

• Lost cusp areas

• Under full crown or PFM crowns.

112

COMPOMERS➢Drawback:-

1. Use of bonding system mandatory

2. Insignificant release of fluoide

3. Lower wear resistant than regular composites.

➢Commercial names of compomers :-

• Compoglass (Vivadent-ivoclar)

• Dyract (Dentsply Caulk,Milford,Delaware)

• F2000 (3M-Espe,St.Paul,Minnesota)

113

GIOMERS

• The name "Giomer" is a hybrid of the words "glass ionomer"

and "composite” .

• Introduced by Shofu Inc. (Kyoto, Japan) in 2000.

• GIOMER is a new group of direct restorative materials and

adhesives that comprises Pre-Reacted Glass-ionomer (PRG)

114

.

20

GIOMERS Indications:• Restorations of Class III, IV and V cavities

• Restorations of Class I cavities and selectively Class II cavities

• Restorations in deciduous teeth

• Base / liner under restorations

• Fissure sealant

• Undercut blockout

• Restorations of fractured porcelain and composites

• Restoration of cervical erosion and root caries

• Repair of fractured incisal edges

• Veneers and posts

• Direct cosmetic repairs

• Pulp capping agent

Example:- BEAUTIFIL( Shofu

115

SMART COMPOSITE

• “Smart” composites are a class of ion-releasing composites.

• Released by Ivoclar in 1998 as Ariston pH control.

• Smart composites contain Amorphous Calcium Phosphate

(ACP), one of the most soluble of the biologically important

calcium phosphates.

• Releases fluoride, hydroxyl and calcium ions as pH drops in

area immediately adjacent to restorative material.

116

SMART COMPOSITE

• Smart composites work based on the developed alkaline glass filler which was designed to reduce secondary caries formation at the margin of a restoration by inhibiting bacterial growth, resulting in reduced demineralization and buffering of acid.

117

SMART COMPOSITE

• Composition :-

• The paste consists of mixture of different types of :-

• Di-methacrylate(20.8 wt %),

• Inorganic fillers Ba,Al and F silicate glass filler (1 μm)

• Ytterbium tri flouride

• Silicon dioxide

• It is filled 80% by weight and 60% by volume.

118

SMART COMPOSITE

• Commercially available as :-

• Smart CEM2 - DENTSPLY

119

CEROMER• Term ceromer stands for ceramic optimized polymer.

• Introduced by Ivoclar Vivadent-Tetric Ceram.

• Ceromers are specific combination of the latest in ceramic filler technology and advanced polymer chemistry which provide enhanced function and esthetic.

120

.

21

CEROMER

• It consist of fine particle ceramic filler which are closely packed

and embedded in advance organic polymer matrix.

• The paste of ceromer contain barium, aluminum fluoride and

silicate glass fillers with silicone dioxide and calcium silicate glass

in di-methacrylate monomer filler contents is 80% by weight.

• The particle size varies from 0.04-3 μm.

121

CEROMER

➢Indications :-

• ClassI and II posterior restorations(stress bearing areas)

• ClassIII and IV anterior restorations

• ClassV restorations ,cervical caries, root erosion,

abfraction, wedge-shaped defects

• Inlays/onlays with extraoral post-tempering

122

BIOACTIVE COMPOSITES• BioACTIVE-RESTORATIVE is a highly esthetic, bioactive

composite that delivers all the advantages of glass ionomers in a

strong, resilient, resin matrix that will not chip or crumble.

• It chemically bonds to teeth, seals against microleakage,

releases more, calcium, phosphate and fluoride and is more

bioactive than glass ionomers, and is more durable and fracture

resistant than composite

123

BIOACTIVE COMPOSITES

• Bioactive formulations :-

• ACP (amorphous calcium phosphate)-2000

• ACP + BIS-GMA /TEGDMA/HEMA with Zirconyl methacrylate

• Fluorinated Bis-GMA analogues

• Liquid crystalline monomers

124

125

BIOACTIVE COMPOSITES

➢ Commercially available as :-• ACTIVA- Bioactive restorative –Pulpdent

➢ Key Features:• Natural esthetics – Highly polishable• Tough, resilient, fracture and wear resistant,

absorbs shock• Releases and recharges calcium, phosphate and

fluoride• Chemically bonds – Seals against microleakage• No sensitivity• Moisture tolerant – Simplified technique

126

https://image.slidesharecdn.com/trendsincompositedentistry-171101181343/95/recent-advances-in-composite-dentistry-39-638.jpg?cb=1509560597

.

22

SILORANE:

127

• The name of this material class

refers to its chemical composition

from Siloxanes and Oxirans.

• Introduced by Guggenburger and

Weinmann in 2000.

• It comprised of ring-opening

monomers that provide for low

polymerization shrinkage.

SILORANE:• Siloranes are polymerized by a cationic reaction in contrast to

methaycrylates, which crosslink via radicals.

• The photoinitiator system is based on three components: light absorbing camphor chinon, an electron donor (eg amine) and an idonium salt.

128

SILORANE:➢ Advantages:-1. Have lower shrinkage

2. Longer resistance to fading and

3. Less marginal discoloration.

➢ Indication:-• Class I

• Class II

• May be used together with glass ionomer cements or resin-modified glass ionomer cements, as cavity liners or bases.

129

STIMULI RESPONSIVE COMPOSITE

• Stimuli-responsive materials possess properties that may be considerably changed in a controlled fashion by external stimuli.

• Such stimuli may be for example changes of temperature, mechanical stress, pH, moisture, or electric or magnetic fields .

130

SELF HEALING COMPOSITE

• Self-repairing or self-healing synthetic materials are reported

showing some similarities to resin-based dental material; it was

the epoxy resin composite

• If a crack occurs in the epoxy composite material, some of the

microcapsules are destroyed near the crack and release the

resin.

• The resin subsequently fills the crack and reacts with a Grubbs

catalyst dispersed in the epoxy composite, resulting in a

polymerization of the resin and repair of the crack

131

FIBRE REINFORCED COMPOSITE

• Conventional dental composite (white fillings) and glass fibres

are combined to give the same level of strength and flexibility.

• The fibers are typically long thin strands of glass fibre that are

aligned as meshes or strips depending on their requirement

• The main advantage of these fibre reinforced composite was

they can be used in both direct and indirect restorations

132

.

23

133

GINGIVAL MASKING COMPOSITES

• Gingiva direct resin composites are fluoride-releasing, bioactive, nano-hybrid composite.

• Available in five Gingiva shades which can be blended with each other, help to create true-to-nature soft tissue areas characterized by great depth and invisible transitions to the tooth

134


• Indications:-

1. Cervical area

2. Wedge-shaped defects

3. Exposed cervical areas

4. Aesthetic correction of gingival recession

5. Primary splinting

6. Ability to mask exposed crown margins to improve aesthetic.

135


136

GRADIA – GC America Beautifill II PINK– Shofu

AMARIS gingiva– VoCo

COLOURED LIGHT-CURING COMPOMER

• Color light-cured material with effect of spangles.

• Based on the compomer technology.

• Available in eight attractive colors with glitter effect

137

COLOURED LIGHT-CURING COMPOMER

➢ Advantages:-

• Easy and quick application from Caps

• Outstanding polishability

• Parents can more easily motivate children to see the dentist

• Children overcome their anxiety

➢ Commercially available as:-

• Twinky star -VoCo

138

.

24

139

Thank you

140

Good Morning

DENTAL COMPOSITE

SPART-III

141

RECENT

ADVANCES OF

DENTAL

COMPOSITES

142

Omnichroma• Single shade of composite.

• Its uniformly sized supra-nano spherical fillers (260nm spherical SiO2-ZrO2) allow OMNICHROMA to match every one of the 16 VITA classical shades.

143

MRP: $99.99

Omnichroma• Single shade of composite.

• Its uniformly sized supra-nano spherical fillers (260nm spherical SiO2-ZrO2) allow OMNICHROMA to match every one of the 16 VITA classical shades.

144

.

25

Omnichroma➢How it works:-

• Most composites depend on the chemical color of the dyes and pigments added to the resin material to emulate certain shades of human teeth.

• OMNICHROMA’s Smart Chromatic Technology is the first use of structural color in composite dentistry as the main color mechanism.

• As ambient light passes through the spherical fillers in OMNICHROMA, they generate red to yellow structural color, the natural colors found in all human teeth.

145

Omnichroma➢How it works:-

• The red-to-yellow color combines with the reflected color of the surrounding tooth to create a seamless match.

• This technology eliminates the need for pigments or dyes, and the result is an unprecedented color-matching ability combined with excellent mechanical properties and high polishability

146

147

Omnichroma• Advantages :-

1. Universal use.

2. Shade matches both before and after bleaching

3. High polishability

4. Highest wear resistance

5. High compressive strength

148

SANDWICH

TECHNIQUE

149

SANDWICH TECHNIQUE

• Developed by McLean.

• Also known as “ laminate” or “bilayer technique”.

150

.

26

SANDWICH TECHNIQUE

“The sandwich of glass ionomer cement, dental adhesive and composite resin is an effective technique that optimally combines the desirable properties of the restorative materials.”

• In the sandwich technique, the GI is placed as a liner or base, followed by placement of a resin composite to provide an aesthetic restoration of the remaining cavity.

151

152

Sandwich Technique

Open technique

Close technique

SANDWICH TECHNIQUE• In the open technique, the GI is used to replace the dentin and

also fill the cervical part of the box, which results in a part of the GI being exposed to the oral environment.

• Use the “open sandwich” technique when there is no remaining

enamel at the gingival margin.

153

SANDWICH TECHNIQUE

• In the closed technique, the dentin is covered by the GI, which is in turn completely covered by the overlaying composite.

• Use the “closed sandwich” technique when there is remaining

enamel at the gingival margin.

154

SANDWICH TECHNIQUE

➢ Indications:

• Class I, Class II, Class III and Class V lesions

• Deep posterior restorations

• Extensive, bulky posterior restorations

• Posterior restorations with sub-gingival interproximal preparations that are difficult to isolate or where no enamel remains.

155

SANDWICH TECHNIQUE

➢Clinical benefits:

• Reduced post-operative sensitivity

• Pulpal protection from irritation

• Fluoride release over time

• Helps in prevention of demineralization

• Rapid placement and curing of a single bulk layer

• Aesthetics

• Radiopacity

156

.

27

Insertion of composites • Different designs of increment placement:-

1. Three increment design:-

• one flat increment at gingival & occlusal wall & two oblique increments both at proximal box occlusal box.

• 1st increment thinner than 1.00mm.

157

Insertion of composites 2. Horizontal layering design:-

• Small increments placed horizontally one above the other, starting from gingival wall to occlusal wall.

• The horizontal placement technique utilizes composite resin layers, each <2.0 mm thick.

158

Insertion of composites 3. Oblique layering technique:-

• The oblique technique is accomplished by placing a series of wedge-shaped composite increments.

• Each increment is photocured twice, first through the cavity walls and then from the occlusal surface, to direct the vectors of polymerization toward the adhesive surface

159

Insertion of composites 4. Vertical layering technique:-

• Place small increments in vertical pattern starting from one wall, i.e., buccal or lingual and carried to another wall.

• Start polymerization from behind the wall, i.e., if buccal increment is placed on the lingual wall, it is cured from outside of the lingual wall.

160

This reduces gap at gingival wall which is formed due to polymerization shrinkage, hence

postoperative sensitivity and secondary caries

Insertion of composites 5. Stratified layering technique:-

• The stratified layering technique was schemed and oriented to the development of functional and anatomic restoration applying the “esthetic”

composite resin restorative materials that include shades of dentin and enamel as well as various translucencies and intensive colors.

• It involves placing dentin shades of composite resin with a higher chroma in the middle of the preparation and placing a lower chroma resin close to the cusp walls.

• The enamel layer is placed following the contours established by the dentin layers and it varies in thickness depending on the desired effect.

161

Insertion of composites 6. Centripetal buildup technique:-• This technique offers a number of advantages when composite resin

posterior restorations are indicated.

• This technique employs thin metal matrix bands and wooden wedges eliminating the need for transparent matrix bands.

162

.

28

Insertion of composites 6. Centripetal buildup technique:-• An important benefit of the procedure is offered by the centripetal buildup

steps first by creating a very thin proximal layer .

• Once the second step of the procedure is completed and peripheral composite envelope is created, the cavity is managed as a simple Class I cavity.

• The centripetal buildup technique is very conservative with preservation of sound tooth structure; it is not time-consuming and it is easy to implement.

163

Insertion of composites 7. Successive cusp buildup technique:-• Here, individual cusps are restored one at a time up to the level of

the occlusal enamel.

• Small sloping increments are applied to each corner of the cavity in turn and manipulation is kept to a minimum, to avoid folding voids into the material.

164

Insertion of composites 8. Three-site technique:-• This is a layering technique that is associated with the use of a clear matrix

and reflective wedges.

• First, the curing light is directed through the matrix and wedges in the attempt to guide the polymerization vectors toward the gingival margin thus preventing any gap formation.

• Then, wedge-shaped composite increments are placed.

165

BIOCOMPATIBILITY OF COMPOSITES

• The biocompatibility of restorative materials usually relate to the effects on the pulp from two aspects:

1. The inherent chemical toxicity of the material and

2. The marginal leakage of oral fluids.

166


• Various components may be released from resin composite restorations into the oral environment.

• According to a national survey of adverse reactions to dental materials in the UK, dental resins are the main cause of adverse reactions in dental technicians, and more than 12% of adverse reactions in patients are related to resin-based dental materials.

167


• Unpolymerized monomers can be leached into saliva and cause adverse reactions .

• Inadequately cured composite materials at the floor of a cavity can serve as a reservoir of diffusible components that can induce long-term pulp inflammation.

• Adequately polymerized composites are relatively biocompatible because they exhibit minimal solubility, and unreacted species are leached in very small quantities.

168

The inherent chemical toxicity of the material

.

29


• According to some studies, it is suggested that formaldehyde, which is a by-product of polymerization, may be responsible for oral lickenoid reactions.

169


• The marginal leakage might allow bacterial ingrowth, and these microorganisms may cause secondary caries or pulp reactions.

• Marginal leakage also leads to accumulate of substrate leading to interfacial staining

• Therefore, the restorative procedure must be designed to minimize polymerization shrinkage and marginal leakage.

170

The marginal leakage of oral fluids


• Bis–GMA/TEGDMA-based composite resins and 4-META/MMA-based resin cements show better biocompatibility compared to 2-hydroxy-ethyl-methacrylate (HEMA) containing resin modified glass ionomer.

• Calcium hydroxide containing products are the materials of choice to be placed in direct contact with the pulp, prior to placement of restorative resins.

171


• There are some reports about the estrogenicity of bisphenol A, a precursor of bis-GMA.

• Bisphenol A was first shown to be estrogenic in 1938, using ovariectomized rats by (Dodds and Lawson, 1938) and then by the other researchers.

172

Bisphenol A Toxicity


• BPA and other endocrine-disrupting chemicals (EDCs) have been shown to cause reproductive anomalies, especially in the developmental stages of fetal wildlife.

• BPA has recently also been shown to exhibit antiandrogenicactivities, which may prove to be detrimental in organ development.

173

Bisphenol A Toxicity

FINISHING OF COMPOSITES

• Optimal finishing and polishing of resin-based composites is a very important step in the completion of a restoration.

• Residual surface roughness can encourage bacterial growth, which can lead to a myriad of problems including secondary caries, gingival inflammation, and surface staining.

174

.

30


• To examine the effect of several significant factors on the finish and polish of a composite restoration:

1. Environment,

2. Delayed versus immediate finish,

3. The types of materials, and

4. Surface coating and sealing.

175


• Environment involves whether the process of finishing and polishing should be performed in a wet or dry field in the mouth.

• Finishing in a dry field with the finishing equipment mounted on a slow-speed handpiece allows for better visualization of the restoration margins.

176

1. Environment


• Studies have shown that a dry polishing technique results in an increase in marginal leakage, possibly because of heat production, which can disturb the marginal sealing ability of the adhesive resins.

• The clinician should finish the restoration in an environment where the margins are clearly discernible and where minimal heat is generated.

177

1. Environment


• Elapsed time may also have an effect on surface characteristics and resistance to leakage that develops.

• Studies have shown that delayed finishing can actually increase marginal leakage and has no effect on surface characteristics compared with immediate finishing.

178

2. Elapsed time between curing of the composite and finishing and polishing


• Almost all composite restorations should be finished and polished shortly after placement during the same appointment, although the finishing should be delayed for approximately 15 minutes after curing.

179

2. Elapsed time between curing of the composite and finishing and polishing


• A variety of materials and devices can be used to finish and polish composite restorations.

• Coarse to ultrafine aluminum oxide discs can be applied to areas with difficult access around the proximal surfaces or in embrasures.

• Tungsten carbide burs or fine diamond tips can be used to adjust occlusal surfaces and blend the composite to the surfaces of the teeth.

180

3. Types of materials and devices

.

31


• An important step in finishing and polishing is the application of a bonding agent or a surface sealer.

181

4. Surface coating and sealing


• Contouring the composite restoration requires skill and knowledge.

• Usually a slight excess of material is present that must be removed to provide final contour and smooth finish.

• Coarse diamond instruments used for removing gross excess.

• Twelve bladed finishing burs or special fine diamond finishing instruments can be used.

182


• Difference between finishing of Microfill composites and Hybrid composites :-

183

Microfill composites

• It posses a surface luster similar to that of tooth enamel.

• Difficult to detect finished margins.

• Contain less inorganic filler→finishing burs tends to clog and need periodic debridement

Hybrid composites

• Exhibit an opaque appearance during dry finishing.

• Preparation margin easily distinguishable.

CONCLUSION• Composites have acquired a prominent place among

the filling materials employed in direct techniques.

• Their considerable aesthetic possibilities give rise to a variety of therapeutic indications, which continue to grow as a result of the great versatility of the presentations offered.

184

CONCLUSION

• Nonetheless, it should not be forgotten that they are highly technique-sensitive, hence the need to control certain aspects: correct indication, good isolation, choice of the right composite for each situation, use of a good procedure for bonding to the dental tissues and proper curing are essential if satisfactory clinical results are to be achieved.

185

REFERENCES• Art and Science of operative dentistry; Sturdevant.

• Science of Dental Material;Philips

• Textbook of operative dentistry; Vimal k Sikri

• Textbook of operative dentistry; Marzouk

• Craig RG: chemistry,composition and properties of composite reins.

• Recent Advances in Composite – A Review P.Benly et al /J. Pharm. Sci. & Res. Vol. 8(8), 2016, 881-883

186

.

32

REFERENCES• Trends in restorative composites research: what is in the future?

Mariel Soeiro MAAS, Yvette ALANIA, et al. Braz. Oral Res. 2017;31(suppl):e55.

• Murray PE,et al; bacterial microleakage and pulp inflammation associated with various restorative,Dent Mater,18:470-478.2002

• Incremental techniques in direct composites; Veeramachaneni Chandrasekhar,Laharika Rudrapati,Vijetha Badami;journal of conservative dentistry;vol 20;6;2017;386-391.

187

188

Thank You

.

1

Dentin bonding agents

Dr. Neha KothariDept Of Conservative Dentistry And Endodontics

Outline

2

Introduction1

Enamel Bonding

Adhesive dentistry

Dentin Bonding

Generations of bonding Agent

2

4

3

5

Introduction ▪ The classic concepts of tooth preparation were advocated in the early

1900s but these have changed drastically.

▪ The fundamental objective of all restorations since centuries has been to create adhesion between two dissimilar surfaces:

3

Introduction ▪ This transformation in philosophy has resulted in a more conservative

approach to tooth preparation, with regard to not only the basic concepts of retention form but also the resistance form of the remaining tooth structure.

▪ With the introduction of adhesives, the concept of dentistry has

changed from –

“Extensionfor prevention to PREVENTION OF EXTENSION!!!”

4

The traditional “drill and fill” approach is fading now because of numerous advancements taking place in bonding.

• Bonding techniques allow more conservative tooth preparations, less reliance on macromechanical retention, and less removal of unsupported enamel.

5 6

ADHESIVE DENTISTRY

.

2

Adherend

Definations

Adhesion 2 Adhesive1 3• Adhesion is a process of solid or liquid interaction of one material

(adhesive or adherent) with another (adherend) at a single interface.

- Sturdevant

• The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking forces or both- The American Society for Testing and Materials (specification D 907)

“The substrate to which the adhesive and dentin is applied”

“A viscous fluid that can join two substrates together, resist separation, and transmit loads across the bond”

8

▪ 1949- Oscar Hagger, a Swiss chemist attempted first to develop an adhesive system for bonding acrylic resin to tooth structure, [acidic glycerophosphoric acid dimethacrylate].

▪ 1949 -a commercial product Sevriton was then marketed.

▪ 1955 - Buonocore applied 85% phosphoric acid on enamel for 30 seconds to achieve a simple acid decalcification.

▪ 1962- Bowen introduced Bis-GMA resin based on epoxy molecule.

▪ 1965- Bowen proposed that surface active monomers could facilitate the bonding of resins to teeth by using reactive monomers that could chelate to calcium.

9

▪ 1977- Fusayama et al, introduced etching technique for both enamel and dentin cavity walls, using 40% phosphoric acid.

▪ 1982-Nakabayashi, reported that dentin clearing by citric acid containing ferric chloride followed by Dentin Bonding Agent containing 4-META was effective on bonding. He also introduced the concept of hybrid zone in the dentin.

▪ 1984- Nakabayashi, again showed that formation of resin tags in the dentinal tubules.

10

“

11

Mechanisms of adhesion

• Interlocking of the adhesive with irregularities in the substrateMechanical

• Chemical bonding between the adhesive and adherendAdsorption

• Interlocking between mobile moleculesDiffusion

• An electrical double layer at the interface of a metal with a polymerElectrostatic

12

Chemical bonding to the inorganic component or organic components of tooth

structure.

Penetration of resin and formation of resin tags

within tooth surface

.

3

Factors Affecting Adhesion

1. Wetting:-▪ Wetting is an expression of the attractive forces between molecules of

adhesive and adherent.

▪ Wetting ability of an adhesive depends upon two factors:

• Cleanliness of the adherend :-Cleaner is the surface, greater is the adhesion.

• Surface energy of the adherend: More the surface energy, greater is

adhesion.

13


2. Contact Angle :-▪ Contact angle refers to the angle formed between the surface of a liquid drop

and its adherent surface.

▪ The stronger the attraction of the adhesive for the adherent, the smaller will be the contact angle. The zero contact angle is the best to obtain wetting.

14


3. Surface Energy :-

▪ Generally, harder the surface, higher is the surface energy, higher is the adhesive property of material.

▪ The surface tension of the liquid and the surface energy of the adherend,

ultimately determine the degree of wetting that occurs.

➢ Adhesive: Low surface energy ➢ Adherend: High surface energy

15


3. Surface Contamination :-

▪ Surface Substrate surface should be clean as the contamination prevents the adhesion.

▪ Adhesive should be able to fill the irregularities making the surface smooth allowing proper or intimate contact

16


3. Water:-

▪ Higher is the water content, poorer is the adhesion.

▪ Water can react with both materials by the high polar group and hydrogen bond which can hamper the adhesion.

17

Steps in forming good adhesion

18

.

4

Indication for adhesive restorative technique ✓ Restore Class I, II, III, IV, V, and VI carious or traumatic defects

✓ Change the shape and the color of anterior teeth.

✓ Improve retention for metallic crowns or for porcelain-fused-

to-metal crowns.

✓ Bond all-ceramic restorations

✓ Bond indirect resin-based restorations

✓ Seal pits and fissures

✓ Bond orthodontic brackets

✓ Bond periodontal splints and conservative tooth replacement

prostheses

Indication for adhesive restorative technique ✓ Provide foundations for crowns

✓ Desensitize exposed root surfaces

✓ Seal beneath or bond amalgam restorations to tooth structure.

✓ Impregnate dentin that has been exposed to the oral fluids, making it less

susceptible to caries

✓ Bond fractured fragments of anterior teeth.

✓ Bond prefabricated and cast posts

✓ Seal apical restorations placed during endodontic surgery

21

Enamel Bonding

Enamel Adhesion

22

• Enamel, the hardest tissue in the human body consists of 95% mineralized inorganic substance, hydroxyapatite arranged in a dense crystalline structure with a small amount of protein and water.

• The mineral component (hydroxyapatite) of enamel play a very important role in bonding of enamel.

Enamel Adhesion

▪ A clinician’s ability to bond a restoration to enamel

has influenced changes in cavity preparations, restorative approaches for esthetical corrections, and the treatment of caries .

▪ Michael Buonocore in 1955, envisioned the use of acids to etch enamel for sealing pits and fissure.

24

Enamel Adhesion

25

• He described a clinical technique that used a diluted phosphoric acid to etch the enamel surface to provide retention of unfilled, self-cured acrylic resins.

▪ .

He first treated the enamel surface of an extracted tooth

with 85% phosphoric acid for 30 seconds after which he rinsed it

He then placed a mixed acrylic resin

drop on this surface, allowed it to dry and placed the tooth in

water.

He found that the acid treated tooth adhered to the resin for 160 hours compared to the control group to which the resin held itself for just 6 hours.

.

5

“▪ Buonocore proposed that on chemical treatment of enamel by acid etching enhances its susceptibility to adhesion by difference in surface energy .

▪ In the late 1960's Buonocoreclaimed that it was the formation of resin tags that caused the principal adhesion of resins to the acid etched enamel .

26

• The formation of resin micro tags within the enamel surface is the basis of RESIN-ENAMEL ADHESION.

27

Acid etching

Irregular surface

Increase in surface energy

Resin penetration Resin tags

28

Application of Etchant

Surface before etchant

Clinically, the most important measure of a properly etched

tooth is the frosty white appearance

of the surface.

Irregular surface

after etchant

“ Etching ▪ It is the process of increasing the

surface reactivity by demineralizing the superficial calcium layer and thus creating the enamel tags. These tags are responsible for micromechanical bonding between tooth and restorative resin.

29

Mechanism of etching

30

➢ Etching of enamel produces a number of effects:

1. Cleanses debris from enamel.

2. Produces a complex three-dimensional microtopography

at the enamel surface .

3. Increases the enamel surface area available for bonding.

4. Produces micropores into which there is mechanical

interlocking of the resin.

5. Exposes more reactive surface layer, thus increasing its

wettability.

Etching pattern of Enamel

31

▪ On etching of enamel, the demineralization is selective because of the morphological disposition of the prisms.

▪ The difference of angulation of the prism crystals causes the acid to have higher demineralization potential at certain micro regions.

▪ Depending on the angulation of the prisms, demineralization can be greater at the prism head or at the periphery.

.

6


• TYPE I- dissolution of enamel prism cores only. This is the most commonest type of etching pattern.

• TYPE II- dissolution of prism peripheries only without dissolution ofprism cores.

• TYPE III- less distinct and etching patterns do not relate to prism morphology.

32

Honey comb appearance Cobble stone Mixed pattern

33


Type IV -pattern has a pitted enamel surface• It displayed only a random distribution of depressions with no preferential destruction of either cores or peripheries.

Type V- Has a flat, smooth surface after etching and they lack micro-irregularities for penetration and retention of resins.

34

Steps for Enamel Bonding• Clean and wash the teeth with water. Isolate to prevent any contamination from saliva or gingival crevicular fluid.

▪ Apply acid etchant in the form of liquid or gel for 10 to 15 seconds.

▪ Wash the etchant continuously for 10 to 15 seconds.

▪ Note the appearance of a properly etched surface. It should give a frosty white appearance on drying.

35

Steps for Enamel Bonding▪ Apply bonding agent and low viscosity monomers over the

etched enamel surface.

▪ Generally, enamel bonding agents contain BISGMA or UDMA with TEGDMA which is added to lower the viscosity of the bonding agent.

▪ The bonding agents due to their low viscosity, rapidly wet and penetrate the clean, dried, conditioned enamel into the microspaces forming resin tags.

36

Resin Tags▪ Bonding of Resin to enamel is mainly Micromechanical type.

▪ Two types of resin tags interlock within the etch-pits. “

Macrotags space surrounding the enamel prisms

Microtags result from resin infiltration/polymerization within the tiny etch-pits at the cores of the etched enamel prisms.

▪ Microtags are more important due to their larger number and greater surface area of contact.

37

.

7

Type of Etchant

38

▪ The effect of the etching agent depends on the type and concentration of the acid, time and the manner of its application.

▪ Various type of etchant used are :-

1. Phosphoric Acid – 30% to 40%

2. Citric Acid - 10%

3. Maleic Acid - 10%

4. Oxalic Acid - 1.6 to 3.5 %

5. Tannic Acid

6. Nitric Acid – 2-5%

7. EDTA

Etchant as liquid or gel

39

• Gels provide a greater control and precision in the placement of etching agents .

• Earlier most gel etchants used to contain silica as a thickening agent. But recently available gels employ polymeric thickening agents which have better wetting abilities and rinse off more easily than silica containing gels.

• Polymer gelled acids have lower pH and thus etches deeper. (Perdigao et al 1996)

Etchant as liquid or gel

40

• On smooth surfaces, etching liquids and gels result in similar etch patterns.

• With deep grooves and fissures, a liquid etch is recommended, because it penetrates the irregularities of the occlusal surface.

41

ETCHANT CONCENTRATION

• Buonocore, initially used 85% phosphoric acid for etching.

• Later Silverstone revealed that optimum concentration of phosphoric acid

should range between 30-40% to get a satisfactory adhesion in the enamel.

• Usually 37% phosphoric acid is used for 15 to 30 seconds .

42

ETCHANT CONCENTRATION

• If the concentration is greater than 50 percent for 60 sec, then monocalcium

phosphate monohydrate may get precipitated.→ can be rinsed off.

• At concentrations lower than 30 percent, dicalcium phosphate monohydrate

is precipitated which interferes with adhesion→ cannot be removed .

Etching time

43

• Traditionally time for etching- 60 sec

• But SEM studies have shown same surface roughness in 15 sec •

Similar shear bond strengths & marginal leakage values for 15 &

60 sec have been observed

• Current recommendations- permanent teeth, 15 to 20 sec

• Fluoridated enamel- require more time i.e, 60-90 sec

• Primary teeth- more aprismatic hence require more time

i.e, 45-60 sec

.

8

44

Dentin Bonding

Dentin Adhesion ▪ The classic concepts of operative dentistry were

challenged in the 1980s and 1990s by the introduction of new adhesive techniques, first for enamel and then for dentin.

▪ An important breakthrough in dentin bonding occurred when Fusayama et al (1979) used 37% phosphoric acid to

etch both enamel and dentin.

45

Dentin Adhesion ▪ Nakabayashi et al -1982 revealed that hydrophilic

resins infiltrated a surface layer of collagen fibres in demineralized dentin to form hybrid layer.

▪ It was not until the early 1990’s that dentin etching

gained world –wide acceptance.

46

Challenges in Dentin Bonding

▪ Structure of dentin

▪ Smear layer

▪ Stresses at resin-dentin interface

47

Adhesion to dentin

1. STRUCTURE OF DENTIN▪ Bonding to dentin has been proven more difficult and less reliable and

predictable than to enamel. This is basically because of difference in morphologic, histologic and compositional differences between the two.

▪ The presence of water and organic components lower the surface energy of dentin and make bonding with hydrophobic resins essentially impossible.

48

Dentin can be considered as a complex hydrated composite of four elements:-

A cuff of hypermineralized

dentin calledperitubular

dentin lines thetubules.

A dense network of tubules that

connect the pulp with the

dentinoenameljunction (DEJ) .

The less mineralized

intertubular dentin contains collagen

fibrils with the characteristic

collagen banding.

49

The intertubulardentin is penetrated by submicron channels, forming intertubularanastomoses

.

9

50

▪ Dentin etching is more technique sensitive than enamel etching because of the complexity of the dentin structure.

Dentin is an intrinsically

hydrated tissue, penetrated by a maze of 1- to

0.25-μm-diameter fluid-

filled dentin tubules.

Movement of fluid from the pulp to the DEJ is a result of a slight but constant pulpalpressure.

▪ Acid etching removes hydroxyapatite almost completely from several microns of sound dentin, exposing a microporous network of collagen suspended in water.

51

52

Collagen is one of the important factors in determining the dentin bonding.

Etched enamel must be completely dry to form a strong bond with hydrophobic adhesive resins, etched dentin must be moist to form a hybrid layer.

If insufficient water is present, the collagen network will collapse and produce a relatively impermeable layer that prevents resin infiltration and subsequent hybridization.

If too much water remains, resin infiltration cannot fully replace the water in the collagen network and, consequently, sets the condition for later leakage into those locations

INTERFACIAL GAP

53

2. Smear Layer

▪ Boyde et al (1963) was first to describe the presence of smear layer on the surface of cut enamel.

▪ Whenever dentin is cut or ground with hand or rotary dental instruments residual organic and inorganic components form a “ smear layer” and is about 1 to 5 μm thick (Brannstrom,1982).

▪ 2 types : - 1. Superficial -

▪ 2. Deep smear plugs

54

Smear layer consists of 2 components-

1. Inorganic- tooth structure (dentinal shavings) & some nonspecific inorganic contaminants.

1. Organic-

• Heat coagulated proteins

• Necrotic or viable pulp tissue

• Odontoblastic processes

• Saliva

• Blood cells

• Microorganisms 55

(Czonstkowsky et al.,1990)

.

10

Depth of Smear Layer ▪ Smear layer has an average depth of 1 to 5 µm but in the

dentinal tubules, it may go up to 40 µm.

▪ Depth of Smear Layer Depends on Following Factors :-

1. Dry or wet, cutting of the dentin.

2. Type of instrument used.

56

▪ The adhesive strength of all cements is always 50% greater in superficial dentin.

▪ It reduces the permeability of dentin by about 86% ( pashly et al,1988)

57

The smear layer has both advantages and disadvantages in the bonding process (Yap et al,1994).

➢ Smear layer is apparently responsible for:

1. Physical barrier for bacteria and bacterial products.

2. Restricting the surface area available for diffusion of both small and large molecules.

3. Resistance to fluid movement.

58

Disadvantages of Smear Layer

1. Smear layer acts as an intermediate physical barrier and may interfere with adhesion and prevents resin penetration into dentinal tubules. (Gwinnett, 1984; Rees and Jacobsen, 1990)

2. The presence of smear layer causes possibility for leakage of microorganisms and a source of substrate for bacterial growth.

3. Presence of viable bacteria which may remain in the dentinal tubules and the use of smear layer for sustained growth and activity

4. It reduces the surface energy which compromises surface wetting.

5. Prevents the intimate surface contact between the adhesive and dentin substrate.

▪59

To remove or not to remove

▪ Smear layer removal is a controversy that fluctuates with the various modalities of restorative dentistry.

▪ Bowen, in 1973 said that smear layer interferes with adhesion of restorative materials and served as a focus of bacteria and bacterial toxins and that it should be removed.

▪ Douglas, in 1989 stated that it acts as an effective natural cavity sealer of dentinal tubules and also reduces permeability, making the smear layer a clinical asset.

▪ Pashley in 1989, said that smear layer is effective in restricting dentin permeability60 61

➢Retaining Smear Layer :-

1. Lowers dentin permeability.

2. Provides barrier to bacterial penetration.

3. Prevents decrease in bond strength seen with some bonding systems as deeper dentin is prepared.

4. 4.Greatly lowers the effect of pulpal pressure on bond strength.

.

11

62

➢Removing Smear Layer :-

1. Exposed collagen provides reactive groups.

2. Exposed collagen promotes micromechanical bonding to resin by providing a framework.

3. Elimination of bacteria that may be present in the smear layer.

4. Permeability of dentin increases 4 to 9 fold.

“▪ Therefore optimal bonding can occur by:

A. Removal of smear layer by using etch and rinse adhesives.

B. Incorporation of smear layer into bonding layer by self-etch adhesives

63

Agents for Smear Layer Removal

1.Citric acid: Acid etching dentin for 60 sec with 6% citric acid removed nearly all of the smear layer as well as the surface peritubular dentin of the tubules.

2. Polyacrylic acid: It is used in combination with glass ionomer cement. An application of not more than 5 sec followed by a copious water rinse results in cleaner surface.

3. Chelating agent, EDTA: The use of chelating agents soften the smear layer allowing its successful removal. Although it is not bacteriocidal, but it is considered to be antibacterial to the extent since it eliminates the bacteria contaminated smear layer.

4. Maleic acid: Maleic acid has been in use as acid conditioner in some adhesive systems.

64

Steps for Dentin Adhesion

ETCHING BONDINGPRIMING

65

Conditioning of Dentin▪ Conditioner is usually a weak organic acid (e.g. maleic acid), a low concentration of a stronger inorganic acid (e.g. phosphoric or nitric acid), or a chelating agent (e.g. EDTA).

▪ Main Actions:1. Heavily alters or removes the smear layer2. Demineralizes Intertubular dentin→ exposes longitudinally /

obliquely oriented collagen fibres3. Demineralizes Peritubular dentin→ exposes a circularly

oriented collagen fibril arrangement4. Decreases free surface energy5. Increases surface roughness

66

Conditioning of Dentin

▪ For removal or modification of smear layer, agents used are:-

1. Acids: Commonly used acid for conditioning dentin is 37% phosphoric acid. Other acids used for dentin conditioning are nitric acid, maleic acid, citric acid, oxalic acid and hydrochloric acid.

▪ According to Brajdiey et al and Shellisy et al phosphoric acid has the ability of increasing inter and intra-tubular dentin permeability, by dissolving the inorganic phase of dentin in a range of 3-7 µm.

67

.

12


3. Calcium chelators: These are used to remove and/or modify the smear layer without demineralizing the surface dentin layer. Commonly used chelator is ethylene diaminetetraacetic acid.

4. Lasers: Nd: YAG lasers used at 10-30 pulses per second. The surface is desensitized by occlusion of open and permeable dentinaltubules.

5. Air abrasion: Aluminium oxide particles are used for air abrasion of a particle size of 0.5 microns.

68


▪ Ideal duration is 15-20 seconds.

▪ Increased duration: greater collapse of collagen due todenaturation.

▪ Decreased monomer

▪ Decreased duration: insufficient depth of etching.

69

DURATION OF ETCHING ON DENTIN

Priming of Dentin

▪ “Primers are agents which contain monomers having hydrophilic end with affinity for exposed collagen fibrils and hydrophobic end with affinity for adhesive resin.”

▪ Commonly used primers have HEMA and 4-META monomers, dissolved in organic solvents.

▪ Primers are used to increase the diffusion of resin into moist and demineralized dentin and thus optimal micromechanical bonding.

72

Priming of Dentin ▪ For optimal penetration of primer into

demineralized dentin, it should be applied in multiple coats.

▪ Also it is preferred to keep the dentin surface moist, otherwise collagen fibers get collapsed in dry condition resisting the entry for primer and adhesive resin.

73

74

Moist vs Dry Dentin

Moist vs Dry Dentin▪ Moist dentin was introduced by -Kanca et al in 1992.

▪ When acetone/ alcohol based primers are applied to moist demineralized dentine, the water diffuses from the wet dentine into the acetone, while the acetone diffuses into the demineralized dentine matrix.

▪ This chemical dehydration of the collagen network caused by substitution of water by acetone also increases the modulus ofelasticity

75

.

13

Moist vs Dry Dentin▪ The water is gradually lost as the solvents and resin monomers occupy

the spaces around the collagen fibrils. Therefore, there is much lessshrinkage.

▪ Reasons for better bonding in moist dentin 1. The acetone trails water and improves penetration of the monomers

into the dentin for better micromechanical bonding.

2. Water keeps collagen fibrils from collapsing, thus helping in better

penetration and bonding between resin and dentin.

76

Moist vs Dry Dentin▪ Disadvantages for moist bonding:-

1. Acetone quickly evaporates -should be quickly applied

-ratio of monomer &acetone changes

2. Keeping the cavity walls wet after conditioning is that one cannot

observe the white frosted appearance of enamel that indicates that

it has been properly etched.

77

Moist vs Dry Dentin➢ Dry bonding :-

▪ Refers to the bonding in which the acid etched dentin is dry and uses the adhesive systems that provide water based primers.

▪ Water-based primers are not dependent on moist dentin because of their ability to self-wet a dried dentin surface and thus separating the collapsed collagen fibers.

▪ 35-50% HEMA in water provided the maximum bond strength, water in these primers probably plasticized the stiffened, collapsed collagen network so that it re- expanded and increased its permeability to primer resins

78 79

Moist vs Dry Dentin▪ Moist dentin as it friendly with all primer types, therefore it is advisable

to have moist dentin for resin-dentin bonding.

▪ To get moist dentin after etching → do not dry the dentin with compressed air after rinsing away etchant.

▪ Instead high-volume evacuation is used to remove excess water and then blot the remaining water present on the dentin surface using gauze or cotton to leave dentin optimally moist.

80

Moist vs Dry Dentin

➢ If the dentin surface is made too dry:-

▪ There will be collapse of the collagen fibers and demineralized dentin.

▪ This results in low bond strength because of ineffective penetration of the adhesive into the dentin.

81

.

14

Moist vs Dry Dentin

➢ If the dentin surface is too wet:-

▪ One cannot check for enamel “frosted” etch

appearance.

▪ There is reduction in bond strength because:

▪ 1. Presence of water droplets dilute resin primer and out-compete it for sites in the collagen network which prevents hybridization.

▪ 2. The phase changes occur in the ethanol or acetone based resins.

82 83

Thank you

84

Good Morning Outline

85

Adhesives 1

Generation of dentin bonding agent

Mechanism of adhesive 2

3

“ Substance that promotes adhesion of one substance or material to another.

86

Adhesives Adhesives ▪ Adhesives are either a hydrophobic or a

hydrophilic methacrylate resin that attaches to the

resin-impregnated dentin surface, via the primer,

and to the surface of the composite restorative,

via copolymerization.

87

.

15

Adhesives ▪ Main Actions:

• Combines with the primer’s monomers to form a resin-reinforced hybrid layer (resin-dentin inter-diffusion zone) from 1 to 5 microns thick.

• Forms resin tags to seal the dentin tubules provides methacrylate groups to bond with the subsequently placed resin composite.

• Act as a stress relaxation buffer to relieve polymerization contraction stresses.

88

Ideal requirements of dentin bonding

Phillips and Ryge,1961 :

▪ High bond strength to enamel and dentin .

▪ Provide an immediate bond

▪ Biocompatibility to dental tissue including the pulp.

▪ Minimize microleakage at the margins of the restorations.

▪ Easy to use and minimally technique sensitive.

▪ Good shelf life.89

Mechanism of Bonding Dentin▪ Adhesive molecule has a bifunctional structure:

90

M represents an

unsaturated

methacrylate

groups capable of

copolymerizing

with other

monomers of a

resin cement or

composite.

R is a spacer group that

provides flexibility and

nobility, and thus

enhanced reactivity, for

M group

X is functional group for bonding which bonds to inorganic or organic portion of dentin

Mechanism of Bonding Dentin

Ideally a dentin bonding agent should have both hydrophilic and hydrophobic ends

91

M———————R———————X

Hydrophobic

end bonds to

the

composite

resin

Hydrophilic end displaces the dentinal fluid, to wet the surface.

CLINICAL PRINCIPLES OF DENTIN BONDING

▪ The application of a dentin bonding system

entails four basic steps.

➢ Step 1. An acid is used to demineralize the

dentin surface.

• It also removes the smear layer →creates space

within the collagen network that is roughly

analogous to the microporosities created by

etching enamel.

92

CLINICAL PRINCIPLES OF DENTIN BONDING

➢ Step 2. A dentin primer is placed over the demineralized

surface.

• It penetrates the demineralized collagen to improve

bonding.

➢ Step 3. An unfilled resin (an “adhesive”) is applied and

penetrates the microporosities.

➢ Step 4. The bonding agent is polymerized

93

.

16

94

Evolution of Dentin Bonding

Agent

▪ The development of dental bonding

systems has continued to evolve over the

past 50 years, with variations in

chemistries, mechanisms, number of

bottles, application technique, and

effectiveness.

95

96

No Etch

Total Etch

Self Etch

First generation ▪ 1950- 1970

▪ Based on silane coupling agents

▪ The main adhesive used was bifunctionalGlycerophospheric acid dimethacrylate (GPDM), glycerophosphoric acid dimethacrylate (NPG-GMA)

97

First generation

▪ The first generation bonding systems were published by Buonocore in 1956, who demonstrated that use of glycerophosphoric acid dimethacrylate (NPG-GMA) containing resin would bond to acid etched dentin.

▪ These bonding agents were designed for ionic bonding to hydroxyapatite or for covalent bonding (hydrogen bonding) to collagen.

98

First generation

▪ These products ignored the smear layer.

▪ The mechanism of adhesion was because of deep penetration of the resin tags into the exposed

dentinal tubules after etching and chelating

component which could bond to the calcium

component of dentin.

▪ Since they could chelate with calcium ions of the

tooth structure, they formed stronger bonds with

enamel than dentin.99

.

17

First generation ▪ Bond Strength:- 2-3 Mpa

▪ Disadvantages:

1. Poor clinical results

2. Hydrolysis of GPADMA in oral environment.

3. Difficulty in bulk polymerization.

4. Low bond strength (2.1-2.8 MPa)

5. Hydrophobic resin

6. Instability

• Eg: Cervident ( SS White) ,Cosmic bond100

Second generation

▪ Late 1960’s – early 1970’s

▪ Phosphate ester dentin bonding agents were introduced containing phenyl-P & hydroxyethyl-methacrylate (HEMA).

▪ Mechanism of action:- polar interaction between negatively charged phosphate groups in the resin and positively charged calcium in the smear layer.

101

Second generation ▪ Bonding agents leave the smear layer intact when

used but some of them employed the use of mild

cleansing agents to remove smear layer

▪ Bond strength: 1- 5 Mpa

▪ Examples – Clearfil Bond System (Kuraray ,

Osaka,Japan) ,Scotchbond ( 3M

ESPE,St.paul,Minn) , Prisma Universal Bond

(Dentsply Caulk)

102

Second generation

▪ Three types of second generation products were made available:

1. Etched tubule dentin bonding agents:

▪ Bonding to dentin was attempted by etching the tubules with 25% citric acid and then making use of ethylmethacrylate to mechanically interlock with the etched tubules.

103

Second generation 2. Phosphate ester dentin bonding agents: ▪ Used mild cleanser to modify the smear layer.

▪ These bonding agents used analogs of Bis-GMA with attached phosphate esters.

▪ It showed 10 to 30% increase in bond strength.

3. Polyurethane dentin bonding agents: ▪ Based on the isocyanate group of the polyurethane polymer which

bonds to different groups present in dentin like carboxyl, amino and hydroxyl groups

104

Second generation

▪ Disadvantages :-

1. Low bond strength

2. Hydrolysis of Phosphate – Ca++ bond

3. Bonding not directly to dentin but Smear layer.

105

.

18

Third Generation

▪ 1980’s

▪ Two component primer/adhesive systems were introduced.

▪ Three step systems.

➢ phosphoric acid etching of dentin- Fusayama et al

➢ Followed by application of primer

➢ Application of unfilled resin

106

Third Generation

▪ Mechanism of adhesion :

1. Conditioner removes smear layer and opens up the tubules.

2. Removal of the smear layer is done before bonding

3. Primer - both hydrophilic and hydrophobic groups used –facilitates bonding with the adhesive

107

Third Generation ▪ Primers used contained HEMA and a 10-carbon molecule, known as 10-

MDP(10-methacryloyloxy decyl dihydrogen phosphate).

`

▪ This generation attempted to deal with both the smear layer and dentinal fluid, with following 2 approaches:

i. Smear layer modification to improve its properties.

ii. Remove smear layer without disturbing the smear plugs that occlude dentinal tubules.

108

Third Generation ➢ Advantages:-

1. Higher bond strengths (8 to 15 MPa)

2. Reduced microleakage

3. Form strong bond to both sclerotic and moist dentin

4. Reduced need for retention form in tooth preparation

5. Can be used for porcelain and composite repairs

6. Erosion, abrasion and abfraction lesions can be treated with minimal tooth preparation.

109

Third Generation

➢ Drawbacks of third generation bonding agents:

▪ Decrease in bond strength with time.

▪ Increase in micro-leakage with time

110

Fourth Generation

▪ Mid 1990’s.

▪ Also known as Three step, Total-Etch adhesives.

▪ The complete removal of the smear layer was achieved with fourth generation bonding system.

111

.

19

Fourth Generation ▪ Mechanism of bonding: ▪ Based on the process of hybridization at the interface of the dentin

and the composite resin.

▪ “ Hybridization is the phenomenon of replacement of the hydroxyapatite and the water in the surface dentin by resin”

112

Fourth Generation ➢ Examples are-1. All Bond 2 ( Bisco,Inc)2. Scotchbond Multipurpose (3M ESPE)3. Optibond FL ( Kerr Corporation)

113

Fourth Generation

➢ Composed of:-

114

An acid etching gel

that is rinsed off

A solution of primers that are

reactive hydrophilic monomer in

ethanol,acetone,or water.

A low viscosity

unfilled or filled resin

fluid bonding agent

Fourth Generation

▪ Bond Strength:-13-30MPa

▪ Advantages:-1. Form strong bond to both enamel and dentine.

2. Ability to bond strongly to moist dentin

3. Also used for bonding to substrates – porcelain.

115

Fifth Generation

▪ Mid 1990’s

▪ Also known as “ one step” or “ one- bottle product”.

▪ Combining the primer and adhesive in to one bottle (self-priming adhesive).

116 117

.

20

Fifth Generation

➢ Examples of the self priming adhesives:-

• Adper Single Bond (3M )

• One Step (BISCO)

• Prime and Bond (Dentsply)

• OptiBond Solo ( Kerr)

118

Fifth Generation

▪ Advantages :-

1. High bond strength

2. Easy to use

3. Reduced number of steps

4. Reduced postoperative sensitivity.

▪ Disadvantages:-

1. Lesser bond strength than fourth generation119

120

Fifth generation bonding agent are distinguished from the fourth generation bonding agents by being one-step or one-

bottle products. In these agents the primer and adhesive resin are in one bottle

Sixth generation▪ Late 1990s and early 2000s.

▪ Two bottle system- acidic primer & adhesive.

▪ No additional etchant was required.

▪ They show sufficient bond strength to dentin but poor to enamel.

121

122

Sixth generation1. Self etching primer and adhesive:-

▪ Available in two bottles- primer and adhesive

▪ Primer is applied prior to adhesive

▪ Examples are Clearfil SE bond (Kurary), Adhese (Ivoclar),

Optibond solo plus(Kerr), Nano bond (Pentron) etc

123

.

21

Sixth generation2. Self etching adhesive:-

▪ Available in two bottles- primer and adhesive

▪ Mixture of both the bottles are mixed and applied.

▪ Examples-, Xeno III (Dentsply), Adper prompt L-pop (3

M), Tenure unibond (Dent Mat)

124 Adper prompt L-pop (3 M) ₹18,351125

Sixth generation▪ Most self etching primers are moderately acidic with a pH

that ranges between 1.8 and 2.5.

▪ Mechanism of bonding: these agents as soon as the

▪ decalcification process starts, infilteration of the empty

▪ spaces by dentin bonding agent is initiated

126

Total etch vs self etch

127


128


129

.

22

130

Sixth generation➢ Advantages of self etching primers:

• Comparable adhesion and bond strengths to enamel and dentin.

• Reduce postoperative sensitivity, as it do not remove the smear layer, the tubules remain sealed.

• They etch the dentin less aggressively than total etch products.

• The demineralized dentin is infiltrated by resin during the etching process.

131

Sixth generation➢ Advantages of self etching primers:

• They form relatively thinner hybrid layer than traditional product which results in complete infiltration of the demineralized dentin by the resin monomers. This results in increased bond strength.

• Much faster and simpler technique.

• Less technique sensitive as fewer number of steps are involved.

132

Sixth generation➢ Disadvantages of self etching primers:

• pH is inadequate to etch enamel, hence bond to enamel is weaker as compared to dentin.

• Bond to dentin is 18 to 23 MPa.

• Since they consist of an acidic solution, they cannot be

stored and have to be refreshed.

• May require refrigeration

• High hydrophilicity due to acidic primers

• Promote water sorption

133

Seventh Generation ▪ Early 2000

▪ Simplified the multiple sixth generation materials into a single component(etchant, primer and adhesive) , single bottle system, thus avoiding any mistake in mixing.

▪ Thus, seventh generation adhesives may be characterized as – “no mix self etching adhesives”

134

Seventh Generation ▪ Seventh generation bonding agents also have disinfecting

and desensitizing properties.

▪ They provide the bond strength of 18 to 25 MPa.

▪ Examples -1. iBond (Heraeus kulzer ),2. G bond (GC), 3. Xeno IV(Dentsply) (glass ionomer based), 4. Clearfil S3 (Kurary).

135

.

23

136

Eight Generation▪ Self etching, self-adhering dental composite.

▪ It eliminates 2 step process.

▪ Direct restorative material are incorporated with a

bonding agent into a flowable. With this flowable

dental composite there is no need to bond separately.

137

Eight Generation▪ Example - Vertise Flow(OptiBond)

138

Eight Generation▪ Advantages :-

1. Offers high bond strength, high mechanical strength.

2. Available in nine different shades.

3. Biocompatible and radiopaque.

4. Easy application, the time saving.

139

140 141

.

24

“ ▪ Hybrid layer and hybridization

▪ Classification of dentin bonding agent

▪ Failure of Dentin bonding

▪ Nanofilled bonding agents

▪ New alternative to etching

▪ Other clinical indications for dentin adhesives

▪ Conclusion

▪ References

142

Part III

143

Thank you

145

SlidesCarnival icons are editable shapes.

This means that you can:● Resize them without

losing quality.● Change fill color and

opacity.● Change line color, width

and style.

Isn’t that nice? :)

Examples:

146 147

Newer alternative to etching

.

25

1. Crystal growth on enamel surface

• D. C. Smith and colleagues introduced crystal growth on enamel surface in 1973.

• The technique uses polyacrylic acid with residual sulphateion to condition the teeth, forming crystals of calcium sulphate dihydrate which are chemically bonded to the enamel.

• The polyacrylic acid interacts with the enamel surface to produce ionozed carboxyl groups.

Crystal growth on enamel surface

• Strong ionic bonding between calcium ions at the enamel surface and the carboxyl groups provide mechanical retention for the bonding resins.

• Previous research suggests that the bond strength achieved with the crystal growth technique is between one and two third that achieved with conventional acid etching

- MacPhoe et al, 1985, Farquhar, 1986; Maskeroni et al,1990

• Since crystal bonding produces less bond strengths compared to conventional acid etch, it is not yet considered a practical technique.

2. Laser etching • Mainly CO2, Argon, and Nd:YAG Lasers are used.

• Laser etching is a process of continuous vaporization and micro-explosions due to vaporization of water trapped within the hydroxyapatite matrix. It causes surface roughening and irregularity similar to that of acid etching to a depth of 10 to 20 m.

• Laser etching is painless and does not involve vibration or heat, making it highly attractive for routine use.

2. Laser etching ➢ Enamel and dentin surfaces prepared by Er:YAG laser

etching show extensive subsurface fissuring that is unfavorable to adhesion.

(J Prosthet Dent 2000;84:280-8)

➢ Adhesion to laser-ablated or laser-etched dentin and enamel was inferior to that of conventional rotary preparation and acid etching.

( Dental Materials (2005) 21, 616–62`14)

3. Air Abrasive Technology▪ In 1992 U.S. Food and Drug Administration granted

clearance to air abrasive cavity preparation system.

▪ A high speed stream of purified Aluminium Oxide particles propelled by air-pressure are used.

▪ It can prepare enamel and dentin for bonding, similar to chemical etching.

▪ Lawrell et al, observed that bond strength to air-abrasive treated enamel surfaces similar to the values obtained with acid etching.

4. Self etch adhesive system▪ The enamel bond strengths of the earliest self-etch adhesives were

lower than those associated with adhesives that rely on a separate etching step.

▪ Self-etching adhesive system uses the smear layer as bonding substrate.

▪ Self-etching primers use an acidic primer to demineralize enamel surfaces.

▪ The basic composition of self-etch primers and self etch adhesive systems an aqueous solution of acidic functional monomers, with a pH relatively higher than that of phosphoric acid etchants.

.

26

4. Self etch adhesive system▪ The enamel bond strengths of the earliest self-etch adhesives were

lower than those associated with adhesives that rely on a separate etching step.

▪ Self-etching adhesive system uses the smear layer as bonding substrate.

▪ Self-etching primers use an acidic primer to demineralize enamel surfaces.

▪ The basic composition of self-etch primers and self etch adhesive systems an aqueous solution of acidic functional monomers, with a pH relatively higher than that of phosphoric acid etchants.

conclusion pain analgesic in

Documents