Anatomy of impacted lower third molars evaluated by computerized tomography: is there an indication for 3-dimensional imaging?
OBJECTIVE
Surgical removal of impacted third molar is one of the most frequent procedures in oral surgery. Today 3-dimensional (3D) imaging is occasionally used. The aim of this study was to describe and estimate the frequencies of anatomic variations of lower third molars in patients with panoramic findings at high risk for inferior alveolar nerve (IAN) injury.


METHODS
The investigators designed and implemented a retrospective cases series study with a study population composed of patients presenting with an impacted lower third molar with projection of the tooth over the full width of the IAN in panoramic radiograph and, therefore, 3D imaging before a planned surgical removal. Spatial relationship to the IAN, type of angulation, root configuration and maturation were primary study variables. Descriptive statistics were computed for all variables.


RESULTS
A total of 707 wisdom teeth in 472 patients (54% female, 46% male) were evaluated. A close relationship to the IAN was seen in 69.7%, and in 45.1% the diameter of the mandibular canal was reduced. In 52.8% the IAN was vestibular and in 37.3% lingual to the roots; there were 9.9% with an inter- or intraroot course. Most teeth had 1 or 2 roots (86.7%), but 13.3% had ≥3 roots. Mesial angulation was the main type (40.2%), followed by vertical (29%), horizontal (13.9%), distal (10.2%), and transverse (6.8%) positions.


CONCLUSIONS
Based on the range of variations in the course of the nerve and the number of roots the authors recommend 3D imaging before surgical removal of a lower third molar that shows signs of a close relationship to the IAN.
Lübbers
Heinz-Theo
HT
Clinic for Craniomaxillofacial Surgery, University Hospital of Zurich, Zurich, Switzerland. t.luebbers@gmail.com
Matthews
Felix
F
Damerau
Georg
G
Kruse
Astrid L
AL
Obwegeser
Joachim A
JA
Grätz
Klaus W
KW
Eyrich
Gerold K
GK
D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data*; D008297:Male; D008334:Mandible; D008340:Mandibular Nerve / Q000000981:diagnostic imaging*; D008964:Molar, Third / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014081:Tooth Extraction; D014095:Tooth, Impacted / Q000000981:diagnostic imaging* / Q000473:pathology; D061221:Trigeminal Nerve Injuries