Long-term effects on alveolar bone with bone-anchored and tooth-anchored rapid palatal expansion.

INTRODUCTION: The purpose of this study was to evaluate the long-term effects of bone-anchored and tooth-anchored expansion appliances on alveolar bone in vertical and horizontal dimensions, compared with controls, using cone-beam computed tomography. METHODS: We evaluated 180 cone-beam computed tomography scans for 60 patients at 3-time points: T1 (pretreatment), T2 (postexpansion), and T3 (posttreatment), for 3 groups: bone-anchored expansion appliance (BA), tooth-anchored expansion appliance (TA), and controls (T1-T3: BA, 2 years 8 months; TA, 2 years 9 months; control: 2 years 7 months). The intermolar width, molar angulation, palatal width, vertical buccal bone height, buccal bone thickness at the alveolar crest, and root apex were measured in the 3 groups at different time points. RESULTS: In the short term, both BA and TA led to a statistically significant increase in the intermolar width and vertical buccal bone loss after expansion compared with controls. Vertical buccal bone loss was significantly greater in TA than in BA. In addition, TA led to significantly increased molar angulation (buccal tipping) compared with controls at T2. There were no significant differences in the 3 groups in the long term except vertical buccal bone loss, which was significantly greater in TA than controls. A substantial correlation was found between molar angulation and vertical buccal bone loss, and a moderate negative correlation was found between intermolar width and buccal bone thickness at the alveolar crest at T3. CONCLUSIONS: There was no difference in the treatment outcomes between the 3 groups in the long term except vertical buccal bone loss, which was significantly increased in the TA group compared with controls.