Position of the mental foramen on panoramic radiographs and its relation to the horizontal course of the mandibular canal: a computed tomographic analysis.
OBJECTIVE
The purposes of this study were (1) to investigate the bucco-lingual course of the mandibular canal in the bony structure and (2) to figure out the relationship between the position of mental foramen on panoramic radiographs and the horizontal course of the mandibular canal.


METHODS
A database of panoramic radiography and spiral computed tomography (CT) scans was searched and 100 subjects were selected based on the criteria. Mental foramina were classified into four groups according to its antero-posterior position. Three measurements were made on each slice of coronal CT scans at three different points: (1) apex of second premolar; (2) median point of two root apexes of first molar; and (3) median point of two root apexes of second molar. The bucco-lingual ratios were calculated to access the relative bucco-lingual position of the mandibular canal.


RESULTS
The distribution of subjects according to the type of mental foramen was: (1) type 3, 67%; (2) type 2, 26%; (3) type 4, 5%; and (4) type 1, 2%. The overall horizontal course of the mandibular canal was relatively constant from the second molar to first molar, whereas much significant directional change was found on the remaining course. Between types 2 and 3, no statistically significant differences were found at the level of the second molar and first molar (P = 0.461 and 0.965, respectively). Only below the second premolar, significant differences were found (P = 0.001).


CONCLUSIONS
Based on the findings of our computed tomographic image analysis, the position of mental foramen on panoramic radiographs was affected by its horizontal course of inferior alveolar nerve. The significant horizontal direction change of the course was found after the canal passing below the mandibular first molar regardless of the antero-posterior position of mental foramen.
Department of Dentistry, School of Dentistry, Seoul National University, Seoul, Korea.
Jung-Hoon
JH
Pyun
Young-Jun
YJ
Lim
Myung-Joo
MJ
Kim
Sug-Joon
SJ
Ahn
Jin
J
Kim
D000328:Adult; D000368:Aged; D001641:Bicuspid / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008340:Mandibular Nerve / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008875:Middle Aged; D008963:Molar / Q000000981:diagnostic imaging; D011862:Radiography, Panoramic / Q000295:instrumentation / Q000379:methods*; D036542:Tomography, Spiral Computed / Q000379:methods*; D019227:Tooth Apex / Q000000981:diagnostic imaging; D014963:X-Ray Intensifying Screens; D055815:Young Adult