Out of 726 orthopantomograms (OPTs) collected between 2015 and 2021, 81 met the inclusion criteria and were categorized into two groups: a control group (38 subjects with erupted third molars) and an experimental group (43 subjects with impacted or partially impacted third molars).
Sixteen parameters were measured—including 11 linear, 4 angular, and 1 ratio—by a trained observer.
Key findings include
★ Control group exhibited
✔ Larger retromolar space (1.52 ± 0.63 cm vs. 1.14 ± 0.60 cm; p = 0.007)
✔ Greater impaction angle
✔ Higher retromolar area-to-third-molar ratio (1.09 ± 0.40 vs. 0.81 ± 0.44; p = 0.004)
★ Experimental group showed a deeper sigmoid notch depth compared to controls (p = 0.030).
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Correlation analyses revealed
★ Moderate negative correlations between anterior ramus notch depth and retromolar space.
★ Strong positive correlation between retromolar area-to‑molar ratio and retromolar space (p 0.001).
★ In controls: moderate positive correlations between retromolar space and both coronoid length and third molar width.
★ In impacted cases: moderate positive correlations between retromolar space and both the condyle–coronoid angle and the inclination of lower posterior teeth.
Gender‑based findings
★ Males in the control group had significantly larger retromolar spaces, impaction angles, and retromolar area ratios than their impacted-group counterparts.
★ Females in the experimental group exhibited a longer coronoid process compared to female controls.
Conclusion
The study suggests that specific panoramic measurements—especially retromolar space, angular orientation, and mandibular structural ratios—may serve as early indicators of lower third molar impaction.
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