6-complex amalgam ( pin retained) restoration
TRANSCRIPT
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Operative dentistry
Dr lobna abo elnasr
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Complex amalgam ( pin retained) restoration
Complex cavity involve more than 2 sufaces + capping of 1
or 2 casps
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Indication:
Controlled restoration in tooth with questionable pulp or periodontal prognosis
Contolled restoration in tooth with acute or sever caries
Definite final restoration
Foundation under fixed restoration
Alternative fo fixed crown and bridges due to high cost
Interim restoration for teeth requie occlusal adjustment
Old age
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Resistance form : box like pepaation + removal of undermined enamel
Retention form: depends on remaining tooth structure pins and slot
more auxillary retention( locks , coves)
What are the goals of contolled restoration
Resistance of tooth against fracture
Protect pulp from oral fluidsControl of caies and plaque
Anatomical contour to protect gingival tissue
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Contraindication:
tooth in esthetic area
patient with occlusal problem
Tooth cannt restoed directly due to anatomical or fuctional consideration
Advantages:
Cheaper than indirect crown
Conservation of time one appointment
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Dis advantages:
dentinal microfracture during pin hole and slot preparation making internal stresses
Microleakage around all types of pins
Decrease strength of amalgam ( tensile strength of amalgam , horizontal stresses of
pins)
Resistance form doesnot protect the tooth from fracture as extracoronal restoration
Penetration and perforation into the pulp and external tooth structure especially with
pinDifficulty in obtaining proper contour especially with lage cavity
NB
Vetical: parallel to long axis
Horizontal : peripendicular to long axis
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Pin etained amalgam estoration:
Definition: any restoration gaining resistance and retention from one or more pins
which cannt be gained from slot , locks, undercuts
Site: large class 2, class 4 on distal surface of upper canine
Tooth preparation:
Initial tooth preparation:
Same as for amalgam when fasciolingual extention of occlusal prepaation exceeds 2
thirds or more of distance between fascial and lingual casp
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Casp capping:
week casp , cavity extend to or more than 2 thirds of distance between casp tip and
central groove
Initially by depth orientation groove 2 mm on
functional casp and 1.5 mm on non
functional casp
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Sharp internal corners rounded decease stress concentration,increase resistance form
resistance form : with flat pulpal and gingival walls
Retention form: slight convergence of fascial and lingual walls fascial and lingual
walls plus fascial and lingual groove
Final tooth preparation:
Removal of caries , old restoration
Calcium hydroxide liner RMGIC liner or base shouldnot extend closer than 1 mm toslot or pin
Coves peripenicular to long axis locks parallel to long axis
Casp reduction decease height of vertical walls so decrease retention
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Pin hole preparation
By using twist drill latch type or depth
limiting drill at low speed ( 300-500) RPM
first make pilote hole with round bur to
localize position of the pin the complete the
hole in one or two thrust( movement)
Apply intermittent pressure
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Drill cant be used for more than 20 holes otherwise it will be dull
dull drill: increase the pressure on handpiece, increase the frictional heat and cracks in
dentin
Location of the pin hole:
How to determine the location of the pinhole:
Knowing the anatomy of tooth and pulp
Radiograph
Piodontal probe
Patient age
Pin should be placed in aeas of greatestbulk of amalgam
pin hole is placed at cevical third or molars
and premolars not closer than 0.5 mm to
DEJ not closer than 1.5 mm from external
surface
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Correct angulation very important to avoid external surface perforation or amalgam
penetration
We can put the drill in gingival cevice and
adjust flat to tooth surface move on occlusal
surface without changing angulation starting
drill parrellel to adjacent external surface
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For better condesation of amalgam , beter clearence we make a recess by depth 0.5
mm in the vetical wall interior to pin by 245 bur for adquate condensation of amalgam
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Ppilote hole is made by ound bur 0.2 mm them complete with the drill to avoid slipping of
the drill ( cawling)
For inadquate depth we use depth limiting
drill on the surface
For retention we can place 2 pins and more
but with rules
pins r placed at different vertical
levels to reduce vertical stresses
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Inter pin distance from 3-5 mm
External perforation occurs in :
ptominent mesial concavity on upper fist molar
midlingual and midfascial of lower first and second molar
midfascial , midmesial and middistal of upper first and second molar
there are critical location ( dont put pin there)
Distal of lower molar
Lingual of ypper molars
Tiltedt teeth
When there is limited interarch space , care must be taken to avoid externalperforation on distal
Rule: one pin for missing axial line angle more pins more retention but pins reduceresistance form so tooth liable more to fracture
For occluso gingival reduction by 2 mm no need for pins
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Disadvantages:
vertical and horizontal stresses formed during insertion leading to dentinal crazing
great danger on pulp
Advantages:
Versatility
Wide range of sizes
Color coding system
Greater retention
Gold plated system so leminate the possibility for corrosion
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Cemented pins:
Depth of the hole 3- 4mm
Pin hole diameter larger than pin diameter
Pins used ae stainless steel may be threaded or serrated
Frictional lock
Diameter of pin hole smaller than pin diameterPins ae tapped in place retained by resiliency of dentin
More retentive than cemented one
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Self threaded pin (TMS)
SELF SHEARING
Titanium o stainless steel
Color coded plastic sleeves
Used in latch type contraangle
Once the pin reach the bottom of the hole shearing is off
STANDARD PIN
Length of the pin is 7 mm
The only pin not applied in the hole by the latch type conta only by hand wrench
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Flattened end to be engaged in hand wrench feeling reaching the
bottom of hole by tactile sense it can be reversed on quater to one half
turn after insertion to full depth to reduce stesses at the apical end of
the pin hole
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Two in one:
2 pins one shorter than the other long one is 9.5 mm
once it each the bottom it shears in half leaving length of the pin extending from dentin
with the other half r emaining in hand wrench
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Contraangle for link series , link plus
hand wrench:
It is moving in clockwise direction and
reversed quarter to half turn in anticlock
wise direction
It is used only for standard
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Adjust ment of length of pin:
Length of the pin in amalgam is 2 mm
Thickness of amalgam from the end of pin is
2 mm
Emoval of excess length of pin by high
speed hand piece
Duing removal of excess tweezethe pin with
TMS bending toolto allow enough thicknessof amalgam occlusogingivallyr stabilize the
pin , high vaccum suction near it to remove
excess
Or by bending
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Size of the pin
color coding systtem, gold larger than silver larger than red larger than pink
Factors affecting selection ofnpin on base of size :
Amount of retention desired
Amount of dentin available to receive pin
For sevely involved posterior tooth use red one to reduce risk of crazing of dentin ,
pilpal penetration, potentional perforation
Silver one used as abackup when pinhole over prepaed for red (wide hole gives silverpin)
Pink pin is too small to give retention
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Silver pin called minim
red pin callen minikin
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How many pins to be used depends on:
Amount of dentin available
Amount of retention required
Amount of lost tooth sttrucure
Size of pin ( silver pin is more retentive
than red one)