[Three dimensional reconstruction measurement study of palatal contour changes in different bone ages after rapid maxillary expansion].

Objective: To compare dental and skeletal changes after rapid maxillary expansion in patients with different bone ages. Methods: Thirty-seven patients in different growth period were divided into three groups according to cervical vertebral maturation (CVM). There were 13 patients in the growth acceleration group, 13 patients in growth peak group, and 11 patients in growth deceleration group. Cone-beam computed tomography (CBCT) images were segmented and reconstructed using Mimics image processing software to assess the change of palatal morphology before and after treatment. Statistical analysis was carried out using SPSS 17.0 software. Results: After the expansion the posterior teeth and alveolar bone were tilted and the mid-palatal suture was opened in all three groups. The first molar angle in the three groups decreased by 2.66°±1.04°, 3.53°±0.81° and 12.32°±1.64°, respectively and no significant difference was found between the acceleration group and the peak group ( P >0.05), but the changes in the acceleration group and the peak groups were significantly less than that in the deceleration group ( P< 0.05). The palatal angle in the three groups increased by 6.01° ± 2.06°, 4.79° ± 1.31° and 6.73° ± 1.71°, respectively and no significant difference was found between the acceleration group and the deceleration group ( P >0.05), but the changes in the acceleration group and the deceleration group were significantly greater than that in the peak group ( P <0.05). The palatal cemento-enamel junction (CEJ) width, the middle palate width and the mid-palatal suture width in the three groups increased by (7.37 ± 1.31), (6.68 ± 0.72) and (5.13 ± 1.42) mm; (5.72±1.68), (4.82±1.66) and (3.42±1.15) mm; (3.14±0.45), (2.98±0.51) and (0.96±0.83) mm, respectively and no significant difference was found between the acceleration group and the peak group ( P >0.05), but the changes in the acceleration group and the peak group were significantly greater than that in the deceleration group ( P <0.05). Conclusions: The mid-palatal suture could be opened in patients in different CVM period. More skeletal and less dental effects were found in patients in the growth acceleration and peek group than in those in the growth deceleration group and the inclination of the alveolar bone could be avoided to a greater degree in patients in the growth peek group.