The Change of Alveolar Bone Thickness on Mandibular Central Incisors of Skeletal Class II Patients After Orthodontic Treatment Using Cone-Beam Computed Tomography.

Objective: To test the null hypothesis that orthodontic tooth movement does not create dehiscences and the sagittal width dimension of alveolar bone is maintained. Materials and Methods: In 60 skeletal class II patients, CBCT images at pre- (T1) and post-orthodontic treatment (T2) were obtained and the presence of dehiscences was recorded. Based on the presence of dehiscences at T1 and T2, the patients were divided into four groups. The alveolar bone thickness at the level of 2 (CEJ2), 5 (CEJ5), 10 (CEJ10), and 15 (CEJ15) mm from the cementoenamel junction (CEJ) was measured on CBCT images in cross section along the long axis on the central incisors. CBCT-synthesized lateral cephalometric images were analyzed. Statistical analysis and the Pearson correlation analyses were utilized at a pResults: CBCT imaging showed that 27.1% of the mandibular central incisors had dehiscences at T1. With pre-existing dehiscence, the incidence of dehiscence increased to 50% at T2. Patients that developed dehiscences after orthodontic treatment showed the highest percentage of alveolar bone loss (-23.7% at CEJ2, -19.9% at CEJ5 at T2). In the group where patients developed dehiscences after orthodontic treatment, there was statistically significant mean increase of L1-NB (3.1mm) and IMPA (9.8°) (pConclusions: When camouflaging skeletal Class II patients, the limits of mandibular anterior incisor forward movement might be less than previously thought. In order to prevent the development of inadvertent dehiscences during the orthodontic treatment, careful diagnosis with CBCT images is recommended. Furthermore, when excessive protrusion and/or proclination is planned, additional treatment modalities such as orthognathic surgery, tooth extraction, and partial corticotomy with bone grafting should be considered