Background: The purpose of the present study was to investigate the short-term effects of microthread location on peri-implant marginal bone levels. Methods: Two types of implants, one with microthreads placed at the implant top (group A) and the other with microthreads placed 0.5 mmbelow the implant top (group B), were placed adjacent to each other in the partially edentulous areas of 20 patients. In total, 40 implants were placed. Bone loss around each implant was analyzed after 1 year of functional loading, and gingival parameters (modified plaque index and modified sulcus bleeding index) of the peri-implant soft tissue were evaluated. Bone losses after loading and gingival parameters were compared using the paired t test. Results: The average bone loss was 0.16 (SD: 0.19)mmin group A and 0.30 (SD: 0.22) mm in group B after 1-year of functional loading. The paired t test revealed a significant difference in crestal bone loss between groups A and B in individual patients (P = 0.004). No significant differences were found between the two groups for the gingival parameters. Conclusions: Less peri-implant bone loss was observed around implants with microthreads placed at the implant top (group A) compared to those in which microthreads were placed below the top (group B). These results indicated that the microthreads acted to stabilize the peri-implant marginal bone, and their locations played an important role in the stabilization process. J Periodontol 2009;80:1937-1944.
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