RESUMEN
Objective: To study the morphological pattern of single oblique complex crown fracture and its relative location to periodontal hard tissues from a three-dimensional perspective by using cone-beam CT, which provides a more intuitive and comprehensive understanding for the pathological features and rules of single oblique complex crown fracture. Methods: Primary cone-beam CT images of 56 maxillary permanent anterior teeth with oblique complex crown root fractures were collected from the Department of Integrated Emergency Dental Care, Capital Medical University School of Stomatology during January 2015 to January 2019. Fracture pattern, fracture angle, fracture depth, fracture width, and the relative location of the fracture line to the crest of the adjacent alveolar ridge were retrospectively analyzed. Independent samples t-test was used to compare the differences in angle, depth and width of fractures between sexes and tooth locations, as well as the pre-and post-fracture crown-to-root ratios between different tooth locations. Then the affected teeth were divided into juvenile group (≤18 years), young group (19-34 years) and middle-aged and elderly group (≥35 years). One-way ANOVA was applied to compare the differences in angle, depth and width of fracture between age groups, and Fisher exact test to compare the differences in fracture pattern of the teeth and the relative position of the fracture line to the crest of the adjacent alveolar ridge. Results: There were 35 males and 21 females in 56 patients, aged (28.2±13.2) years. Among the 56 affected teeth, forty-six were maxillary central incisors and 10 were lateral incisors. According to the patients' age and growing stage, they could be divided into the juvenile group (19 cases), the young group (14 cases), and the middle-aged and elderly group (23 cases). Forty-six (82%) affected teeth had an S-shaped fracture pattern, and ten (18%) had a diagonal pattern, in which the fracture angle of the S-shaped fracture line (47.85°±10.02°) was significantly greater than that of the diagonal line (28.30°±8.07°) (P<0.001). The fracture nadir was flush with or below the top of the alveolar crest in 98% (55/56) of cases. The fracture depth was significantly greater in the juvenile group [(1.75±0.73) mm] than in the young group [(1.21±0.68) mm](P=0.042) and in the middle-aged and elderly group [(1.12±0.90) mm] (P=0.001). The width of fractures among 56 patients was (4.75±1.44) mm, which had no statistically significant differences between different age, sex and tooth location groups (P>0.05). There were no statistically significant differences in the crown-to-root ratios after fracture of maxillary central incisors (1.18±0.13) compared to maxillary lateral incisors (1.14±0.20) (t=1.90, P=0.373). Conclusions: The fracture patterns of single oblique complex crown fracture were mainly S-shaped and oblique alignment; the fracture nadir was mostly located within 2.0 mm below the palatal alveolar crest.