Third molar impaction FOR ORTHODONTIST by almuzian

1. 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 relatedto 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 ofimpaction
1. Localcauses
A. Lack of spacedue to large teeth or under-development mandible.
B. Excessive density of the bone or the soft tissues.
C. Ectopic position
2. systemic causes

2.  Acquired diseases: anaemia and endocranial dysfunction
 Developmental diseases: clediocranial dystosis and cleft palate.
Types of third molar impaction
According to the availability of space betweenthe distal surface of the
secondmolar 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 secondmolar:
 Vertical Impaction:
 Horizontal impaction:

3.  Mesio-angular impaction
 Disto-angular impaction:
 Inverted impaction:
Problems may be causedby impacted third molars:
(RobinsonPD 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 incisorcrowding & Third molar debate:
Studies relating third molars to crowding :( Jensenstudy (1960)
Richardsonand 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.

4.  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 correlationbetweenthird molars and crowding
(Ades at al., (1990)Harradine et al., (1998)
 Ades at al., (1990)
4 study groups all a minimum of 10 years postretention (Washington group)
1. Absent 8s
2. Impacted 8s
3. Erupted and functional
4. Extracted at least 10 years before postretention 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.

5. 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-indicationfor 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.
NationalInstitute of Dental Researchin 1979 andAmerican Associationof
Oral and MaxillofacialSurgeryin 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

6. 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.
Managementof Unerupted and Impacted Third Molarteeth – SIGN
Guidelines
There are three levels of recommendation.
A. Removalof 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. Removalof Ue and Impacted Third Molars advisable when:
1. Signify Infection assoc
2. occupation or lifestyle prevents access to dental care
3. med. Condition

7. 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;

8.  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.