Third molar extraction is among the most commonly performed procedures in oral and maxillofacial surgery, yet lingual cortex complications — perforation of the lingual plate, injury to the lingual nerve, or displacement of the tooth into the lingual pouch — remain a genuine surgical risk. That risk is determined in large part by the thickness of the lingual cortical bone in the third molar region: bone that varies considerably between patients and that cannot be reliably assessed from standard radiographs. Understanding which anatomical characteristics predict a thin lingual cortex would allow the surgeon to anticipate the complication before encountering it.
Mandibular flare — the orientation of the mandibular rami relative to the body, and by extension the overall breadth and geometry of the jaw — is one such characteristic. A mandible that is wider at the condylar level, or more divergent in its rami, has a different biomechanical history from a narrower one, and the bone it produces in the third molar region may differ accordingly. Whether that difference is clinically meaningful was the question that a team of researchers set out to examine.
The study drew on pre-operative CT data from 26 patients who had undergone orthognathic surgery between January 2014 and December 2017. CT datasets were imported and processed using Osteo3d software, which was used to locate anatomical landmarks and derive the measurements of interest. Four mandibular flare parameters were recorded: two angular — the condylion-to-menton angle (Co-Me) and the gonion-to-menton angle (Go-Me) — and two linear, the bigonial width (Go-Go) and the bicondylion width (Co-Co). Lingual cortex thickness was measured at three axial levels in the third molar region: crestal, middle, and apical. Patients were classified into skeletal malocclusion groups — Class I (n=10), Class II (n=11), and Class III (n=5) — and correlations between flare parameters and cortical thickness were analysed within each group.
The angular measurements did not differ significantly across the three groups. The linear measurements told a more differentiated story: bicondylion width was significantly greater in Class III patients than in the other groups (P=0.007), confirming that Class III mandibles are structurally distinct at the condylar level. More clinically relevant were the correlations within groups. Class III patients showed a strong negative correlation between mandibular flare — particularly the linear measurements — and lingual cortex thickness at the middle and apical levels. In a small but representative sample, the pattern was consistent: a wider, more flared mandible in a Class III patient predicted thinner lingual bone.
The clinical implication is straightforward. Surgeons planning third molar extraction in a Class III patient face a structural context in which the lingual cortex is more likely to be attenuated. The measurement of mandibular flare from a pre-operative CT — a routine dataset in orthognathic surgical planning — can serve as a practical indicator of lingual bone availability before the extraction begins. The study adds a quantitative basis to what experienced clinicians have often inferred qualitatively: the shape of the jaw carries information about the bone within it.
Osteo3d Team
Clinical Affairs