Third Molars

Question 1

At what age to third molars usually erupt?

Answer 1

18-24yrs, but highly variable

Question 2

What percentage of the population have one or more third molars missing?

Answer 2

About 25%

Question 3

What nerves may be at risk in surgical extraction of third molars?

Answer 3

1 - Lingual
2 - Inferior Alveolar
3 - Mylohyoid
4 - Long buccal

Question 4

In what area is the lingual nerve close to the mandible and what is the approximate distance?

Answer 4

27mm length in the retromolar region, at 0-3.5mm away from lingual plate

Question 5

What SIGN guideline relates to removal of third molars?

Answer 5

SIGN 43

Question 6

What is the definition of an “unerupted tooth”?

Answer 6

A tooth lying within the jaws, entirely covered by soft tissue and partly or completely covered by bone.

Question 7

What is the definition of a “partially erupted tooth”?

Answer 7

A tooth that has failed to erupt fully into a normal position. The term implies that the tooth is partly visible or in communication with the oral cavity.

Question 8

What is the definition of an “impacted tooth”?

Answer 8

A tooth that is prevented from erupting into a normal functional position. This may be due to a lack of space, obstruction by another tooth, or an abnormal eruption path.

Question 9

Removal of uneruptd or partially erupted third molars is NOT advisable…?

Answer 9

1 - In patients whose third molars would be judged to erupt successfully and have a functional role in the dentition.
2 - In patients whose medical condition renders removal an unacceptable risk to the overall health of the patient, or where benefit is outweighed by the risk
3 - In patients with deeply impacted third molars where there is no evidence of pertinent local or systemic pathology.
4 - In patients where the risk of surgical complications is judged to be too high or fracture of an atrophic mandible may occur.
5 - Where the removal of one third molar is planned under LA, simultaneous extraction of asymptomatic conralateral teeth should not normally be done .

Question 10

Removal of unerupted or partially erupted third molars IS advisable…?

Answer 10

1 - In patients who are experiencing or have experienced significant infection associated with third molars
2 - In patients with predisposing factors whose lifestyle or occupation precludes ready access to dental care.
3 - In patients with a medical condition where the risk of retention outweighs the risk of extraction of third molars.
4 - In patients who have agreed to tooth transplant, orthognathic surgery or other relevant surgical procedure.
5 - Where an GA is to be given for the removal of one third molar, consideration should be given to the removal of others where the risk of retention and further XGA outweigh the risk of removal.

Question 11

There are strong indications for removal of third molars when…?

Answer 11

1 - There have been one or more episodes of infection such as pericoronitis, cellulitis, abscess formation or untreatable pulpal/periapical pathology.
2 - There is caries in the third molar that is unlikely to be usefully restored or there is caries in the 7 that cannot be successfully restored with the 8 in place.
3 - There is periodontal disease associated with the third molar or its relationship to the 7.
4 - In cases of dentigerous cyst formation or other related oral pathology.
5 - In cases of external resorption of the third molar or second molar where this would appear to be caused by the third molar.