The retromolar foramen represents a little known anatomical variation in the
posterior mandible of uncertain clinical importance. It has been the subject of limited
study. Findings and conclusions of these studies have been placed under little
Suggested clinical consequences associated with the presence of the retromolar
foramen include local anaesthetic failure, local haemorrhage during surgery,
perineural spread of infectious and invasive pathology, and loss of sensation in the
normal distribution of the buccal nerve due to surgical intervention. Reports of the
possibility of these complications seem to suggest that the retromolar foramen, canal
and its associated neurovascular bundle are structures of great clinical importance.
Case reports seem to have, however, only included reports of loss of gingival and
buccal sensation as a consequence of third molar surgery in the presence of this
anomaly. This study therefore aimed to report the prevalence of the retromolar foramen and
canal in the South African population, describe its course and structure, and produce
a clinical framework in which to approach the presence of the retromolar foramen.
Comparisons between the present and existing studies were made and conclusions
concerning the clinical importance of this structure were drawn.
Inspection of a sample containing 946 mandibles was performed. Of these, 885 were
regarded as suitable for inclusion. These mandibles were inspected for the presence
of a retromolar foramen in which a 1 mm diameter needle could pass through without
resistance. The distance from the last tooth in the arch to the retromolar foramen
was also measured. Fifty of these mandibles were then randomly selected and
scanned using microfocus computed tomography. Seventy mandibles were found to have at least one retromolar foramen (7.9% of the
total sample). No statistically significant differences were found when the presence
of the retromolar foramen was correlated with race, sex or age. The finding that sex
and age played no significant role in the presence of the retromolar foramen is in
agreement with available literature. Detected prevalence seemed to be heavily
influenced by the method used to determine the presence of the retromolar foramen.
The average distance between the second mandibular molar and the retromolar
foramen was 16.83 ± 5.57 mm and the average distance between the third
mandibular molar and the retromolar foramen was 10.47 ± 3.77 mm. These findings
were found to be in agreement with most other reports.
Fifty retromolar canals were selected at random and scanned using microfocus
computed tomography. Analysis revealed four basic patterns. These were type A, a
vertical canal between the inferior alveolar canal and the retromolar area of the
mandible, type B, a curved canal taking a recurrent course between the inferior
alveolar canal and the retromolar area, type C, a canal with an approximately
horizontal path between the inferior alveolar canal and the retromolar area, and the temporal crest canal (TCC, not designated as type D to create a distinction between
it and types A, B and C), a canal terminating on either side of the temporal crest.
Type B was the most common presentation (68% of retromolar canals in the study),
a finding contrary to that of other studies.
The presence of the retromolar neurovascular bundle is of uncertain clinical
importance and requires further anatomical and pharmacological study to determine
its effect on local anaesthetic failure. A model in which the retromolar canal branches
from the inferior alveolar canal does not seem to support a conclusion in which local
anaesthetic failure may be directly attributable the presence of this anatomical
variation alone. Classification of the retromolar canal is of limited clinical use and
may require a revised scheme if clinical application is sought. Complications
associated with the presence of the retromolar foramen are poorly documented and
seem to be of little consequence.