Angle Orthod. 2020 May 1;90(3):330-338. doi: 10.2319/080219-510.1.
To evaluate the presence of dehiscences and changes in alveolar bone height and width in the area of the mandibular central incisors pre- and post-orthodontic treatment.
In 60 skeletal Class II patients, cone-beam computed tomographic (CBCT) images were obtained and the patients were divided into four groups based on the presence of dehiscences at pre- and post-orthodontic treatment. The alveolar bone height and width were measured on CBCT in cross section along the long axis of the teeth. Lateral cephalograms were analyzed.
The changes in L1-NB and IMPA appeared to be correlated with vertical bone loss and dehiscence. Alveolar bone height appeared to follow a segmented relationship with these two variables, with changes below a threshold (L1-NB = 0.71 mm, IMPA = 3.02°) having relatively minimal or no effect on bone loss but with changes beyond the threshold correlated with extensive bone loss. Similarly, increases in L1-NB or IMPA correlated with decreases in alveolar bone width (L1-NB: -0.25 mm/mm, IMPA: -0.07 mm/°) and increased the probability of developing dehiscences, with an estimated 50% probability of vertical bone loss at a L1-NB change of 2.00 mm or, equivalently, an IMPA change of 8.02° was estimated.
When treating skeletal Class II patients, the limits of incisor proclination/protraction are less than previously thought. To prevent undesired periodontal outcomes, careful three-dimensional diagnosis is advisable. Furthermore, when excessive protrusion and/or proclination is planned, additional treatment modalities, including orthognathic surgery, tooth extraction, and corticotomy with bone graft, should be considered.
评估下颌中切牙区正畸治疗前后牙槽骨高度和宽度的骨开裂情况和变化。
对 60 例骨骼 II 类错颌畸形患者进行锥形束 CT（CBCT）检查，并根据正畸治疗前后骨开裂情况将患者分为四组。在牙齿长轴的横截面上，用 CBCT 测量牙槽骨高度和宽度。分析侧位头颅侧位片。
L1-NB 和 IMPA 的变化似乎与垂直骨丢失和骨开裂有关。牙槽骨高度似乎与这两个变量呈分段关系，低于阈值（L1-NB=0.71mm，IMPA=3.02°）的变化对骨丢失影响较小或没有影响，但超过阈值的变化与广泛的骨丢失相关。同样，L1-NB 或 IMPA 的增加与牙槽骨宽度的减少相关（L1-NB：-0.25mm/mm，IMPA：-0.07mm/°），并增加了发生骨开裂的概率，估计 L1-NB 变化 2.00mm 或相当于 IMPA 变化 8.02°时，垂直骨丢失的概率为 50%。
在治疗骨骼 II 类患者时，切牙内倾/前倾的极限比之前认为的要小。为了防止牙周不良后果，建议进行仔细的三维诊断。此外，当计划进行过度突出和/或内倾时，应考虑额外的治疗方式，包括正颌手术、拔牙和骨切开术联合植骨。
