Third molar impaction

Impacted tooth

Tooth blocked from eruption by physical barrier, such as another tooth bone,

soft tissues or pathological lesions. (Bishara 2001)

Germotomy

It is the pre-eruptive removal of the tooth germ (Bergstrom and Jensen 1960).

Crowding

It is the loss of arch perimeter which can be manifested in the arch by closure of

space or teeth slipping their contacts with resultant rotations and/or movement

of teeth (Leroy Vego 1962).

Prevalence related to wisdom tooth Missing 9% to 20% (Bishara SE, 1983).

There are more females than males with congenitally missing third molars. The

ratio is 3:2 (Richardson 1980).

Impacted wisdom was 17%.

Causes of impaction

1. Local causes

A. Lack of space due to large teeth or under-development mandible.

B. Excessive density of the bone or the soft tissues.

C. Ectopic position

2. systemic causes

Acquired diseases: anaemia and endocranial dysfunction

Developmental diseases: clediocranial dystosis and cleft palate.

Types of third molar impaction

According to the availability of space between the distal surface of the

second molar and the anterior border of the ascending ramus of the

mandible:

Class I: the space is sufficient to accommodate the mesiodistal diameter of the

crown of the third molar.

Class II: the space is not sufficient to accommodate for the entire mesiodistal

dimension, i.e. part of the crown of the lower third molar is located within the

ramus.

Class III: there is no space for the third molar to erupt, i.e. the whole crown of

the third molar is located within the ramus.

According to the relative depth of the tooth within the bony mandible:

Position A: the highest part of the tooth is on level with or above the occlusal

plane.

Position B: the highest point of the tooth is below the occlusal plane and above

the cervical margin of the second molar.

Position C: the highest point of the tooth is below the cervical margin of the

second molar.

According to the position of the long axis of the third molar to the long axis

of the second molar:

Vertical Impaction:

Horizontal impaction:

Mesio-angular impaction

Disto-angular impaction:

Inverted impaction:

Problems may be caused by impacted third molars:

(Robinson PD 1994):

Nothing

Pain and swelling from pericoronitis,

periodontal infection

Caries.

Resorption of an adjacent root

Enlargement of a follicular cyst.

Bone loss due to chronic periodontitis.

Lower incisor crowding & Third molar debate:

Studies relating third molars to crowding :( Jensen study (1960)

Richardson and Mills (1990)

Jensen study (1960) They have examined 60 dental students (33 persons with

unilateral third molar aplasia in the maxilla and 30 in the lower. They have

found that in both maxilla and mandible there was a greater degree of crowding

on the side where the third molar was present.

Richardson and Mills (1990) have compared the mesial drift and change in

crowding over a 5-year period in 30 subjects whose lower second molar were

extracted between age 11 and 17 years and 30 subjects whose lower second

molars were not extracted. They have measured the arch length on the dental

casts. They suggested that the presence of a developing third molar can, in some

cases, cause forward movement of buccal teeth with an increase in crowding

and that the extraction of second molar is effective in reducing the incidence of

late lower arch crowding and third molar impaction.

Studies indicating lack of correlation between third molars and crowding

(Ades at al., (1990) Harradine et al., (1998)

Ades at al., (1990)

4 study groups all a minimum of 10 years post retention (Washington group)

1. Absent 8s

2. Impacted 8s

3. Erupted and functional

4. Extracted at least 10 years before post retention records

No significant differences in mandibular growth or LLS crowding between any

of the subgroups.

Harradine et al., (1998)

1. A prospective, randomised controlled clinical trial.

2. Patients randomly allocated into third molar extraction and non-extraction

groups.

3. Found very small decrease in LLS irregularity in patients who had had lower

third molars removed, NOT STATISTICALLY OR CLINICALLY

SIGNIFICANT.

4. CONCLUSION: The removal of third molars in an attempt to reduce the degree

of late lower incisor crowding cannot be justified.

Bishara and Andreasen (1981) have demonstrated some points to describe

the contra-indication for the removal of the third molar in orthodontic

point of view.

The following describe their suggestions:

When the mandibular premolars are either missing or extracted and closure of

space in the lower arch is part of the orthodontic treatment plan where there is

no extractions to be performed in the upper arch, the molar relationship will be

Class III. The maxillary second molar will have little or no occlusal relationship

with the opposing tooth, that is, the mandibular second molar. Preservation and

later, proper alignment of the third molar will allow them to inter-digitate with

the maxillary second molar.

In case with first and second molars were extracted particularly in non-growing

persons with class II malocclusion or open-bite tendencies.

National Institute of Dental Research in 1979 and American Association of

Oral and Maxillofacial Surgery in 1993 recommendation:

1. Crowding of the lower incisors is a multifactorial phenomenon that involves a

decrease in arch length, narrowing of the intercanine dimension, retrusion of the

incisors, and growth changes occurring in adolescence. Therefore, it was agreed

that there is little rationale based on the available evidence for extraction of

third molars solely to minimise present or future crowding of lower anterior

teeth. If adequate room is available for third molar eruption, every effort should

be made to bring these teeth into functional occlusion.

2. It may be advisable in some cases to remove third molars before starting

distalizaton procedure.

3. There is no evidence to suggest that a third molar is needed for the development

of the basal skeletal components of the maxilla and mandible.

4. If extraction of wisdom is indicated, it is preferable not to perform enculation

procedure.

Management of Unerupted and Impacted Third Molar teeth – SIGN

Guidelines

There are three levels of recommendation.

A. Removal of Ue and Impacted Third molars NOT advisable:

1. successfully and functional role in dentition;

2. MH renders removal

3. Risk of surgical complications like unacceptably high risk of fracture atrophic

mandible;

4. Surgical removal of single third molar planned under LA, do not take out

asymptomatic contralateral teeth.

B. Removal of Ue and Impacted Third Molars advisable when:

1. Signify Infection assoc

2. occupation or lifestyle prevents access to dental care

3. med. Condition

4. pts who agreed a tooth transplant procedure/ orthog surgery/ other relev.

Procedure;

5. GA to be admin for removal of at least one third molar.

C. Strong indications for removal:

1. one or more episodes of infection;

2. caries;

3. perio disease;

4. dentig. Cyst.

5. External resorption.

6. Other indications for removal

Autogenous transplantation to 1st molar socket;

Fracture md;

Prior to denture construction or planned implant.

Complications (serious)

1. Fracture of the mandible;

2. Oro-antal communication;

3. Fractured instrument;

4. Nerve damage.

5. Common complications:

haemorrhage;

bruising;

displacement;

wound dehiscence

damage to adjacent teeth

Treatment of impaction

1. Observation

2. Operculectomy/surgical periodontics

3. Coronotomy, Partial excision to avoid damage to the IAN

4. Surgical exposure

5. Surgical reimplantation/transplantation

6. Surgical removal/excision of tooth/teeth

7. In selected cases with co-operation of experienced orthodontic opinion,

Orthodontics prior to surgical treatment to avoid IAN damage remains

incompletely evaluated.