Quantitative cone-beam computed tomography assessment of anterior loop safety margins using canine-guided osteotomy designs for chin bone harvesting.

BACKGROUND

/purpose: Chin bone harvesting is a common intraoral grafting procedure but carries a risk of neurosensory complications involving the mental foramen (MF), anterior loop (AL), and mandibular incisive canal (MIC). Present study quantitatively evaluated whether the mandibular canine can serve as a safer and more reproducible landmark for chin bone harvesting.

MATERIALS AND

METHODS

Cone-beam computed tomography (CBCT) scans from 40 adults were analyzed. The mandibular canine distal angle (CDA) and canine long axis (CLA) were used as reference lines. Measurements included AL-MF length, distances from the CLA to the MF and AL, interMF distance (IntMF), interAL distance (IntAL), interCLA distance (IntCLA), and the vertical relationship between the canine apex and the MIC. Sex- and side-based comparisons were performed, and correlations with age and variables were assessed. Probability modeling estimated the likelihood of AL or MIC encounter under various osteotomy scenarios.

RESULTS

The mean AL-MF length was 1.76 ± 0.96 mm, with no significant sex or side differences. Canine-referenced measurements showed consistent horizontal safety margins, maintaining ≥2 mm from the AL in all cases. At 3 mm posterior to the CLA, the probability of avoiding AL injury exceeded 96.25%. Vertically, the MIC was often close to the canine apex, and deeper osteotomies increased risk. ANB angle demonstrated significant positive correlations with CLA-MF, CLA-AL, IntMF, and IntAL.

CONCLUSION

The mandibular canine is a reliable landmark for horizontal osteotomy planning. This approach improves reproducibility and may reduce nerve exposure. Conservative depth control and cortical-only harvesting are recommended to minimize MIC-related complications.