Objectives: 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.
Materials and methods: 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.
Results: 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.
Conclusions: 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.
Keywords: Bone loss; CBCT; Dehiscences; Periodontal limits; Skeletal Class II.
© 2020 by The EH Angle Education and Research Foundation, Inc.