Abstract: PURPOSE: To observe the effect of bone grafting during the extraction of mandibular third molar on repair of distal alveolar bone defect distal to the second molar. METHODS: The risks of the distal alveolar bone defect in the second molar were estimated after removal of the impacted teeth according to the position of the third molar and second molar before operation. It was divided into three groups: low risk group, medium risk group and high risk group. The medium risk group and high risk group were further divided into bone graft subgroup (group A) and non-bone graft subgroup (group B). There were 36 cases in group A and 45 cases in group B. Postoperative re-examination indicators included subjective perception of the patients, depth of probing and height of alveolar bone in the distal molar of the second molar by X-ray examination. The data were analyzed with SPSS 19.0 software package. RESULTS: Six months after operation, in mediun risk group, 0 cases in group A had subjective feelings of cold and heat stimulation; in group B, the number was 6 cases, the difference was significant (P<; 0.05). Distal periodontal probing depth of the second molar was (2.93±; 0.34) mm in group A and (2.95±; 0.50) mm in group B. There was no significant difference between 2 groups (P=0.931). X-ray examination of the alveolar bone height increment of the second molar Δh: (3.31±; 1.02) mm in group A, (3.10±; 1.72) mm in group B, the difference was not significant (P=0.794). In high risk group, 4 cases in group A had subjective feelings of cold and heat stimulation; in group B, the number was 10 cases,the difference was significant (P<; 0.05). Distal periodontal probing depth of the second molar was (3.08±; 0.37) mm in group A and (3.24±; 0.41) mm in group B. There was no significant difference between 2 groups(P=0.931). X-ray examination of the alveolar bone height increment of the second molar Δh: (5.21±; 1.79) mm in group A, (2.99±; 2.42) mm in group B, the difference was significant (P<; 0.05). CONCLUSIONS: Risk classification of the second molar distal bone defects after extraction of the impacted teeth is essential, which is helpful to determine whether bone grafting is needed during operation. Autologous bone mixed with Bio-Oss artificial bone powder can promote recovery of the alveolar bone height of the second molar, especially in high risk group, and discomfort caused by exposure can be reduced.

Key words: Impacted teeth, Bone graft, Alveolar bone repair