[Characteristics of the alveolar bone defects evaluated by cone-beam CT in periodontitis patients with orthodontic treatment history of Angle class Ⅱ malocclusion].

To evaluate the levels of alveolar bone defects by using cone-beam CT in periodontitis patients with history of orthodontic treatment and to find the special tooth positions, sites and periodontitis stages of alveolar bone defects, so as to provide reference for the formulation of clinical personalized diagnosis and treatment plans. Thirty patients who were diagnosed as Angle class Ⅱ malocclusion, treated by using labial fixed orthodontic appliances and also diagnosed as periodontitis (orthodontic group) were recuited from January 2009 to June 2019 at the School and Hospital of Stomatology, China Medical University in the present study. They were aged (27.0±5.4) years old (ranged 18-41 years old). Another 60 periodontitis patients without a history of orthodontic treatment matched according to age, gender and severity of periodontitis were selected as control group (non-orthodontic group). They were aged (26.7±5.2) years old (ranged 18-41 years old). Cone-beam CT images were used to measure the heights of the alveolar bone defects at each tooth position of the patients. The difference in the heights of the alveolar bone defects between the orthodontic group and the non-orthodontic group at the same position of the maxillary and mandibular alveolar bones were compared. The specificities of the defect heights in different positions of the maxillary and mandibular alveolar bones and different sites of the same tooth position were analyzed among orthodontic group. The specificities of the different tooth positions of the maxillary and mandibular alveolar bones of the different periodontitis stages among orthodontic group were compared. The heights of the alveolar bone defects in the maxillary canine area and molar area, the mandibular incisor area, the canine area and the premolar area in the orthodontic group were higher than that in the non-orthodontic group, and the differences were statistically significant (<0.05). In orthodontic group, the most severe teeth in the maxillary and mandibular alveolar bone defects were the canine areas [(3.75±1.00), (3.83±1.10) mm]. Secondly, the more severe tooth positions of the maxillary alveolar bone height defects were the molar area [(3.67±0.84) mm] and the incisor area [(3.39±0.83) mm] and the more severe tooth positions of the mandibular alveolar bone defects were the incisor area [(3.73±1.42) mm] and the molar area [(3.54±0.81) mm]. The height of the alveolar bone defect in the mandibular incisor area was greater than that in the maxillary (<0.05). The bone defect in the maxillary molar area was severer than that of the mandibular area (<0.05). The alveolar bone defects in the buccal and lingual sides were mostly larger than that of the mesial and distal sides both in maxillary and mandibular positions except for the maxillary incisor area(<0.05). The most severe alveolar bone defect position changed with the periodontitis stage. The most severe tooth position of the maxillary in stage Ⅰ periodontitis was in the molar area [(3.26±0.63) mm], whereas the incisor area was the most severe tooth of the mandible [(3.14±1.04) mm]. In addition, among maxillary incisor area, canine area, premolar area, molar area, the most severe alveolar bone defect height was the canine area in stage Ⅱ, Ⅲ, Ⅳ mandibular (<0.05). In periodontitis patients with a history of orthodontic treatment, the height of the alveolar bone defect was specific to the tooth positions and sites. With the periodontitis stage changing, the most severe defect position changed in both maxillary and mandibular alveolar bones. It is recommended to pay more attention to the alteration of alveolar bone in periodontitis patients with a history of orthodontic treatment and give timely targeted treatment plans.