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MANDIBULAR THIRD MOLAR IMPACTION

What is Impaction ?

Origin from latin word – impactus

It is the cessation of eruption of a tooth caused by a physical barrier or ectopic positioning of a tooth.

An impacted tooth is one that is erupted, partially erupted or unerupted and will not eventually assume a normal arch relationship with the other teeth and tissues.

Often used erroneously to include unerupted and maloposed teeh

Unerupted tooth-not having perforated oral mucosa, likely to erupt.

Maloposed tooth- a tooth,erupted or unerupted which is in abnormal position in maxilla or mandible

chronologyTooth germ-9 years

Cusp mineralization-2 years later

11 years- -tooth located in anterior border of ramus,occlusal suface facing anteiorly

Crown formation-14 years

Root-50% formed by 16 years

Root formation with open apex -18 years

24 years- 95% of 3rdmolars completed eruption

Theories of impaction (Durbeck)

The Phylogenic theory

The Mendelian theory

The Endocrine theory

The Pathological theory

The Orthodontic theory

The Skeletal theory

Local causes

ObstrucLack of space

Retained deciduous teeth

Premature loss of deciduous teeth

Ectopic position of tooth bud

Obstruction of eruption path

Cyst tumor and supernumery teeth

Infection and trauma

Abnormality of jaw

Dilaceration : abnormal path of eruption of tooth

Due to traumatic forces during the eruption period

Systemic causes

Commonly impacted teeth

In the decreasing order :

Indications for removal

Prevention of pericoronitis

Dental caries or prevention of dental caries

Periodontal disease or its prevention

Prevention of root resorption

Odontogenic cysts & tumours

Pain of unexplained origin

autogenous transplantation to first molar socket

Indications for removal

Fracture of the jaw/tooth in the line of fracture

Prosthetic problems e.g. under prosthesis

Orthodontic relapse/facilitation of orthodontic tooth movement

Tooth interfering with orthognathic and/or reconstructive surgery

Prophylactic removal- Patients with medical or surgical conditions requiring removal of third molar (e.g. organ transplants, alloplastic implants, chemotherapy, radiation therapy)

pericoronitis

is an infection of the soft tissue around the crown of partially impacted tooth and is caused by the normal oral flora.

If the patient experience a mild transient decrease in host defense, pericoronitis may result.

pericoronitis may arise secondary to minor trauma from maxillary third molar.

The soft tissue that covers the occlusal surface of the partially erupted mandibular third molar known as the operculum can be traumatized and become swollen this can be treated by removal of maxillary third molar.

Unrestorable caries: in the 3rd molar or in the 2nd molar which can’t be restored unless 3rd molar is extracted.

Periodontal diseases : Pocket b/w 2nd & 3rd molar not removed beyond 30 years becomes irreversible

Untreated impacted teeth cause bone loss dital to 2nd molar due to pressure effect.

In case of dentigerous cysts or other oral pathology expands the bone results in pathologic fracture.

Atypical pain Avoid confusion with TMJ joint pain or MPDS.

Autologous transplantation: to 1st molar socket when 1st molar removal is indicated.

The presence of a tooth in a fracture line increases the risk of infection especially when the tooth has been displaced/ rendered non-vital.

In case of prosthesis.

Orthodontic reasons – highly debatable topic

Orthodontic surgeries – diminishes the risk of surgical complications in sagittal split osteotomy

Contraindications for removalAdequate space

Partially impacted that can be used as abutment

Medically compromised patients Risk exceeds benefit

Simultaneous extraction of asymptomatic contra lateral teeth not done

Deeply impacted, asymptomatic as damage to adjacent structure may occur

High risk cases surgical complications, fracture of atrophic mandible may occur

Socioeconomic reasons

In case of pericoronitis/infection – wait till the inflammation/ infection is controlled (otherwise dry socket or acute osteomyelitis

Classification of Impacted mandibular third molar

I. Based on nature of overlying tissue impaction

1. soft tissue impaction: due to dense fibrous tissue overlying the teeth. (early loss of primary teeth subsequent masticatory trauma to the ridge fibromatosis )

2. hard tissue impaction: obstruction by the overlying bone. Tooth completely encased in bone. Extensive amount of bone removal & tooth sectioning required.

II. Winter’s Classification

based on the inclination of the impacted 3rd molar to the long axis of the second molar.

Mesioangular : tooth tilted towards 2nd molar in a mesial direction.

Distoangular : distal direction

Horizontal

Vertical

Buccal or lingual :

Transverse : tooth completely impacted in buccolingual direction

SIGNIFICANCE : PATH OF WITHDRAWAL

EASE OF EXTRACTION : MA > DA , B > L

III. Pell and Gregory’s classificationA) Three subclasses based on the relationship

with anterior border of mandible

1. Class I

2. Class II

3.Class III

B) Based on the position of the occlusal plane

1. Position A

2. Position B

3. Position C

C) The third component is similar to winter’s classification

Clinical EvaluationFull medical & dental history, extraoral & intraoral examination.

General examination : presence of systemic disorders & diseases

Assess for irradiation therapy, cytostatic therapy, organ transplantation

Local examination :

Eruption status of impacted tooth

Resorption of 2nd molars

Presence of local infection

Orthodontic consideration

Caries

Periodontal status

Orientation & relation to inferior dental canal

Occlusal relationship

Regional lymph nodes

TMJ function

Surgical Implications

Radiological Assessment

Types :Periapical-necessary to make sound decision for proposed surgery

Lateral-in class III horizontally impacted 3rd molars.

Occlusal-in viewing buccal/lingual impaction

OPG- both jaws seen-anatomy of surrounding structures seen

- position of tooth

War lines

Three imaginary lines :

> White line corresponds to the occlusal plane

>Amber line- represents the bone level

>Red line- indicates the amount of bone that will have to be removed before elevation.

Interpretation of radiograph

Access : determined by the inclination of the external oblique ridge.

Position and depth :orientation, ectopic positions may be seen

WAR LINES :

White line :

vertically impacted- II to occlusal surface

distoangular- o.s. meets the white line in front of 3rd molar

mesioangular-meets behind the 3rd molar

horizontally impacted - _|_ to o.s.

Amber line :

drawn from the surface of the bone on the dital aspect of the 3rd moar to the crest of the interdental septum b/w the 1st and 2nd molars.

Red line : drawn _|_ from amber line to the imaginary point o pplicationofelevator.

Red line

1. Less than 5 mm

2. More than 5 mm

3. 9 mm or more

4. Tooth below the 2nd molar apices

Recommendations

Tooth removed under LA

Under endotracheal intubation

-do-

-do-

Every increase by 1 mm Extraction 3 times difficult

Wharf’s Assessment1. winter’s classification Horizontal

DistonangularMesioangularVertical

2

210

2. Height of the mndible 1-30 mm

31-34mm35-39mm

0

12

3. Angulation of 2nd molar 1-50º

60-69º70-79º80-89º90º

0

1234

4. Root shape Complex

Favorable curvatureUnfavorable curvature

1

23

5. Follicles Normal

Possibly enlargedEnlarged

0

12

6. Path of exit Space available

Distal cusps coveredMesial cusp also coveredBoth covered

0

123

Total 33

Crown of impacted tooth :Bulbous & prominent difficultConical & flat easy

Roots of impacted tooth : Position & root pattern determine point of application and line of withdrawal.Ideal : 2/3rd root formed

Not indicated : 1/3rd root formed ( tooth tends to roll)Difficult :not removed during formative stage, entire root

length developedFusion: fused conical roots more easy to extractCurvature : severely curved/dilacerated >

straight/slightly curvedconvergent<divergent

Width :directly proportional (more bone to be removed)** Root of 2nd molar – if roots of 2nd molar are smaller

than 3rd,care should be taken not to luxate it

Bone texture :varies with age & site Younger ppl cancellous & elastic

Old ppl dense & sclerosed

Therefore bone removal easy in younger ppl

Relationship with the inferior Alveolar nerve

Changes related to tooth root

Changes related to the canal

Surgical management