Abstract
Lower third molars (M3M) are the most frequent impacted teeth. The aim of this study was to evaluate the correlation between M3M position and gonial angle. A retrospective cross-sectional study was conducted. The study population included patients with unilateral or bilateral M3M and underwent Cone Beam Computed Tomography. A morphometric analysis of the mandible was performed after three-dimensional reconstruction, recording gonial angle (GA), ramus high, ramus width, ramus divergency, and retromolar space. GA was the primary predictor variable. The primary outcome variable was the position of M3M analyzed in sagittal, axial, and coronal planes. Descriptive, bivariate, and multiple regression statistics were performed (p < 0.05). Study sample included 172 patients (mean age: 26.3 ± 4.6 years); 266 M3Ms were analyzed. The average GA was 122.6° ± 4.8°. A reduced GA value was significantly associated with a deeply impacted M3M in the ramus. With a progressive decrease of GA, M3M assumed a more horizontal position closer to the mandibular canal (p < 0.05). A lower GA showed a reduced retromolar space with more complex impacted M3M (p < 0.05). The results confirm a statistically significant correlation between GA and the position of M3M. Higher incidence of impacted M3M was related to a reduction of the GA value.
Highlights
The specific aim of the study was to correlate the gonial angle to the position of M3M in relation to the (1) second molar (M2M), (2) mandibular ramus, (3) alveolar crest, (4) inferior alveolar nerve (IAN), (5) buccal or lingual wall, and
The distance between the mandibular ramus and the M2M (7-R) showed a significant correlation with Juodzbalys and Daugela score (JD) (β = −0.7; CI: −0.9, −0.4; p < 0.0001): the JD score increased with decreasing 7-R. This retrospective study aimed to perform a morphometric analysis of the mandible after a 3D reconstruction of Cone Beam computed tomography (CBCT) scans in order to evaluate the correlation between mandibular morphology and the lower third molar position
The retromolar space was significantly smaller in the group with impacted M3M and it was associated with lateral asymmetry of M3M in both groups
Summary
Winter and Pell-Gregory implemented two different classification models, assessing the position of the M3M on panoramic radiograph [6,7]. Despite these classification systems being easy and intuitive, they are missing in providing some fundamental information to the surgeon because they are based on two-dimensional (2D) exams [8,9]. For this reason, a significative update was introduced by Stacchi and colleagues, estimating the difficulty of the third molar surgery after analyzing
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