Conical beam CT measurement of alveolar bone structure remodeling in patients with skeletal class III malocclusion after orthodontic-orthognathic treatment
Zhao Qihang1, 2, Lu Xin1, Tong Lei1, Shang Yonghui1, 2, Li Shuai1, 2, Liu Wen1, Zhou Jianhua1, Yuan Rongtao1, Guo Qingyuan1
1Qingdao Hospital of Shandong Rehabilitation University/Stomatological Center of Qingdao Municipal Hospital, Qingdao 266000, Shandong Province, China; 2Dalian Medical University, Dalian 116000, Liaoning Province, China
Abstract: BACKGROUND: Most of the studies on combined orthodontic-orthognathic treatment of skeletal class III malocclusions have focused on the improvement of the patient’s lateral appearance and recovery in the later stages of the treatment, while there are fewer studies observing the microcosmic nature of the alveolar bone remodeling of the lower anterior teeth.
OBJECTIVE: To evaluate the therapeutic effect of lower anterior tooth decompensation and alveolar bone remodeling in patients with skeletal class III malocclusion before and after orthodontic-orthognathic treatment based on oral X-ray lateral films and oral cone-beam CT.
METHODS: From January 2015 to May 2023, 15 patients with skeletal class III malocclusion who underwent orthodontic-orthognathic surgery at Qingdao Hospital of Rehabilitation University were enrolled. All patients underwent lateral cephalography and cone beam computed tomography before and after treatment. Cephalometric measurement items related to the angle and line distance, lip/lingual bone cracking length (d-La/d-Li) and bone cracking/bone fenestration of the lower anterior teeth before and after treatment were measured.
RESULTS AND CONCLUSION: Lateral X-ray films showed that the amount of alveolar bone remodeling after decompensation of the lower anterior teeth showed significant changes compared to before treatment. The root of the tooth moved significantly towards the center of the alveolar bone, and the specific data was closer to normal data, but there were still some differences compared with normal individuals. Based on the cone-beam CT measurement, the bone cracking/bone fenestration length and width of the alveolar bone were improved in almost all the teeth after orthodontic-orthognathic combined treatment, alveolar bone remodeling in some teeth even reached the level of healthy individuals. Before treatment, most patients often experienced bone fenestration/cracking on the lip/lingual side of the lower incisor due to compensatory tooth growth. However, during the preoperative orthodontic stage, decompensation triggered alveolar bone remodeling and significant changes in tooth angle. Preoperative orthodontic treatment caused the upper anterior teeth to retract and the lower anterior teeth to tilt and control the root, but the amount of decompensation before surgery was often insufficient. In the orthognathic surgery stage, the jaw was removed through the positioning guide plate, the maxilla moved forward, and the mandible retreated. During the postoperative orthodontic process, the effect of fine adjustment was better. Although there is a certain degree of recurrence trend in the position of teeth and jawbones, the postoperative orthodontic treatment is closer to the normal value.
Key words: underbite, orthodontic-orthognathic treatment, lower anterior teeth for compensation, bone cracking, bone fenestration