Abstract: Objective To analyze the labial bone dehiscence, fenestration and root resorption of upper incisors in adult skeletal Class II Division 1 patients with different periodontal phenotypes. Methods 24 cases of skeletal Class II Division 1 adult patients were included in the study. Gingival thickness of upper incisor was measured quantitatively and noninvasively by overlapping CBCT and digital model data before orthodontic treatment. According to the gingival thickness of the upper incisors, patients were divided into thin PP group (gingival thickness < 1.5mm) and thick PP group (gingival thickness ≥ 1.5mm). CBCT was used to measure the occurrence and progress of fenestration, dehiscence and root resorption before and after treatment. Results The incidence of dehiscence and fenestration on upper incisor of all included patients was 31.2% and 18.8% respectively before treatment and increased to 75% and 20.8% after treatment. The distance between the crest of labial alveolar ridge to the cemento-enamal junction (LA-CEJ) was 3.19 ± 0.43mm in the thin PP group, which was significantly higher than that in the thick PP group (2.16 ± 0.11mm), but there was no significant correlation between LA-CEJ and gingival thickness (r = -0.1108, P = 0.6146). There was a positive correlation between root resorption and gingival thickness (r = 0.4223, P = 0.0447). The root resorption in the thick PP group (2.24 ± 1.24mm) was significantly higher than that in the thin PP group (1.08 ± 0.73mm). Conclusions The labial alveolar bone dehiscence, fenestration and root resorption of upper incisors were aggravated after tooth extraction orthodontic treatment. The risk of vertical alveolar bone resorption is increased in the thin PP group, and the risk of bone fenestration and root resorption is increased in the thick PP group.

Key words: Periodontal Phenotype (PP), Orthodontic Treatment, Dehiscence, Fenestration, Root Resorption