[Evaluation of palatal bone thickness in adults with normal occlusion for orthodontic miniscrews placement].

OBJECTIVE: To investigate the palatal bone thickness in adult with normal occlusion.

METHODS: The cone beam computerized tomography records of 32 adults with normal occlusion (16 males and 16 females), mean age (30.1 ± 6.5) years, were used to measure the bone thickness at midpalatal area and the right and left palatal sides. Coronal slices at 3 mm intervals were generated. Slice 1 was the coronal slice through the posterior border to the incisive foramen, while Slice 7 was the coronal slice 18 mm away from the incisive foramen. At each coronal slice, the midpalatal sites were Site M and the sites on the exterior margin of the hard palatal were Site D. Four equally divided parts on the line linking Site M to Site D were named Site A, B, C from the interior to the exterior respectively. Palatal bone thickness were measured at these sites.

RESULTS: Significant differences were noted from Slice 1 to Slice 7, the bone thickness of palate tended to decrease from the front to the back. The thickest site at hard palatal was 12.6 mm, locating at Site D of Slice 1, while the thinnest site was 2.7 mm, locating at Site B of Slice 7. The palatal bone thickness ranged from 10.5 mm (maximum) to 5.8 mm (minimum) at Slice 2 and Slice 3. No statistical significance was found between the left and right sides (P > 0.05).

CONCLUSIONS: The favorable sites for miniscrew placement were the anterior region of the hard palate in adult. The length of miniscrew ranged from 5 mm to 10 mm can be placed from 6 mm posterior to the incisive foramen.