[A comparative study on the effects of three types of toothbrushes on the formation of abfraction lesions in teeth]

To compare the differences in formation of abfraction lesions using three different types of toothbrushes, i.e. mechanical electric toothbrush, sonic electric toothbrush, and ordinary manual toothbrush.

Seventy-one subjects were recruited publicly and randomly divided into three groups with 24 subjects in the mechanical electric toothbrush group (experimental group 1 ), another 24 subjects in the sonic electric toothbrush group (experimental group 2), and 23 subjects in the ordinary manual toothbrush group (control group). The observation period was 12-15 months. During the beginning and the end of the experiment, oral digital impressions were obtained by using 3Shape TRIOS 3 intraoral scanning device (Denmark). The two 3D Object (.stl) files obtained were compared and overlapped by using EXO CAD software，and the numerical values of the cervical changes of all canines, first premolars, and second premolars on the labial and buccal sides of the gingival margin after comparison and overlap were measured using 3Shape 3D ViewerTM software.

The cervical defect values of the mechanical electric toothbrush group were significantly higher than those of the sonic electric toothbrush group and the ordinary manual toothbrush group (P＜0.001), and the cervical defect values of the sonic electric toothbrush group were significantly higher than those of the ordinary manual toothbrush group (P＜0.001). There was no significant difference in gender within each group between the mechanical electric toothbrush group and the sonic electric toothbrush group (P＞0.05), while the cervical defect values of the male subjects in the ordinary manual toothbrush group were significantly higher than those of the female subjects (P＜0.001). The cervical defect value of the mechanical electric toothbrush group was significantly higher than that of the conventional manual toothbrush group at 14, 25, 35, 43, 44 and 45 tooth positions among the three groups (P＜0.05). Meanwhile, the cervical defect value of the mechanical electric toothbrush group was significantly higher than that of the sonic electric toothbrush group at 44 tooth position (P＜0.05). There was no significant difference in the defect value among all groups (P＞0.05).

Compared with ordinary manual toothbrushes, mechanical electric toothbrushes and sonic electric toothbrushes are more effective in promoting the formation of abfraction lesions. The teeth in the lower right mandible are more susceptible to abfraction lesions caused by mechanical electric toothbrushes.