Objective: To evaluate the root resorption in mandibular incisors after orthdontics treatment of adults with skeletal class ID via CBCT (cone-beam computed tomography (reconstructed images. Methods: The study sample comprised 17 patients with skeletal ClassIII malocclusional who need to undergo orthognathic surgery. CBCT images were taken before the treatment and before the surgery, then CBCT data were reconstructed with Mimics software. On these three-dimensional images, each mandibular incisor were segmented and volumes of each root were calculated. The difference between pre-treatment and post-treatment root volumes were statistically evaluated with a paired-samples t-test. Also, the percentage of root volume loss was compared with each other with one-way analysis. Results: The difference between the pre-treatment and post-treatment root volumes was statistically significant for all roots investigated. ①No statistically significant difference was found for the percentage of root volume loss. Conclusion: Following treatment before orthognathic surgery .significant root volume loss was observed for all investigated mandibular incisors. Grate attention should be paid and active treatment is necessary.%目的:利用CBCT(Cone-Beam CT)三维重建技术评估成人骨性Ⅲ类错(牙合)患者在正颌手术前的正畸治疗中,下切牙唇向移动后的牙根吸收情况.方法:对17名需要进行正颌手术的成人骨性Ⅲ类患者分别在矫治前及正颌手术前对下切牙区进行CBCT扫描,经软件处理进行三维重建,对每个牙根单独成像后分别测量其牙根体积.利用统计学方法比较治疗前后牙根体积量及吸收量百分比的变化.结果:①下切牙在唇向移动后牙根体积显著减小,具有统计学差异；②不同牙位间牙根吸收量百分比比较,无统计学差异.结论:成人骨性Ⅲ类错(牙合)在术前正畸治疗移动下切牙的过程中,下切牙牙根发生了较为明显的吸收.在临床治疗中需要引起足够重视.
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