Bone modifications around porous trabecular implants inserted with or without primary stability 2 months after tooth extraction: A 3-year controlled trial

Purpose: Implant primary stability has long been considered a prerequisite for successful osseointegration. However, achieving stability may be difficult when placing implants in wide postextractive bone defects. The purpose of this study was to conduct a clinical and radiographic investigation of bone modifications at porous-structured implants inserted with or without primary stability. Materials and methods: Fifty porous-structured implants were inserted in the posterior sockets of 50 consecutive patients 2 months after tooth extraction, combined with allogeneic bone and a resorbable membrane. The implants were divided into two groups according to insertion torque: spinner (spinning at 35 Ncm, n = 23) and stable (stable at 35 Ncm, n = 27). Implant stability was assessed by resonance frequency analysis from baseline to 6-month function. Follow-up took place 3 years after implant placement. Results: At baseline, the implant stability quotient was undetectable in the spinner group and averaged 75.07 +/- 5.84 in the stable group. At uncovering, the implant stability quotient increased to 71.33 +/- 4.42 and 77.97 +/- 3.30 in the spinner and stable group, respectively (P < 0.001). After 6 months of loading, no between-group difference in implant stability quotient was found (P = 0.13). Marginal bone level changes were similar between groups at all follow-ups, averaging -0.41 +/- 0.77 mm and -0.15 +/- 0.53 mm at 36-month follow-up in the spinner and stable group, respectively (P = 0.35). No implant failed throughout the observation period. Neither biological nor mechanical complications occurred. Conclusion: Implants with a moderately rough surface and a porous-structured body may osseointegrate even without primary stability.