Abstract: Objective: To investigate effects of alveolar ridge preservation on delayed implantation for patients with different alveolar crest bone defects. Methods: According to the extent of alveolar bone defect before single mandibular posterior tooth extraction, ninety-four patients were divided into two groups: mild group (n=53), 3-5mm alveolar bone defect; moderate and severe group (n=41), >5mm alveolar bone defect. After tooth extraction, each group was further randomly divided into two subgroups: patients with (the trial group) or without (the control group) alveolar ridge preservation. Results: After 6 months, compared to the control groups, the width and height reduction of the alveolar ridge bone in each subgroup was less in the trial groups (P<0.05). Compared with situation before tooth extraction surgery, the gingival recession levels (GRLs) increased in each group, while pocket depth (PD) and attachment loss (AL) decreased. The ratios of 4.1mm and 4.8mm implants in diameter in mild group were respectively accounted for 26.4% and 73.6%, while the ratios were 46.3% and 53.7% in the moderate and severe group. The difference between two groups was statistically significant (χ²=4.029, P=0.045). The difference of distributions of implant length between the mild group and moderate and severe group was also statistically significant (χ²=21.207, P=0.000). Conclusion: The alveolar ridge preservation technique could effectively reduce the alveolar ridge bone loss in the graft area after tooth extraction, which was conducive to delay implantation operation, especially for patients with alveolar ridge bone defect >5mm before tooth extraction.

Key words: Tooth extraction, Alveolar ridge, Bone defects, Alveolar ridge preservation technique, Delayed planting