Tricortical versus paramedian bicortical palatal anchorage in maxillary atresia: A CBCT study

Maxillary transverse deficiency limits the choice of safe and stable palatal miniscrew sites. Cone-beam CT (CBCT) mapping of the posterior palatal supra-alveolar insertion site (PPSAIS) may support bicortical/tricortical anchorage planning.

To quantify bone height available for tricortical and posterior bicortical insertion in patients with maxillary atresia using CBCT.

In this observational cross-sectional study, 90 full-head CBCT scans (ages 14-40 years; equal sexes) with maxillary atresia were analyzed. Palatal bone height was measured at paramedian bicortical sites (anterior: second premolars; posterior: first molars) and at PPSAIS trajectories (45°-60°) on both sides using 3D Slicer/NNT. Intra-observer reliability was tested with ICC. Spearman correlations assessed the relationship between insertion angle and tricortical height.

Tricortical PPSAIS heights exceeded bicortical values: means 5.6 mm (right) and 5.8 mm (left). Anterior bicortical heights averaged 3.5 mm; posterior bicortical heights were lowest (2.7-2.8 mm). No significant sex differences were observed for tricortical height. Spearman correlations between insertion angle and tricortical height were weak and non-significant (ρ = 0.12-0.25; all P > 0.05). Comparisons across age groups (14-19, 20-29, 30-40 years) showed no significant differences in transverse discrepancy or bone height at any site (all P > 0.05), indicating stability of palatal anatomy across this age range. Intra-observer reliability was good (ICC = 0.90).

In maxillary atresia, the posterior palatal supra-alveolar region provides sufficient bone for tricortical miniscrew trajectories largely independent of modest angle variation and with no clinically relevant age-related differences in bone height. CBCT-guided planning should prioritize PPSAIS when stable skeletal anchorage is required for expansion.