Stage-Dependent Peri-Implant Bone Remodelling Under Occlusal Contact in a Murine Model

INTRODUCTION AND AIMS: Occlusal contact conditions are dynamic during implant healing and maintenance, but peri-implant bone responses may depend on the maturity of the bone-implant interface. This study evaluated stage-dependent peri-implant bone responses to contact-level and loading-change conditions using a rat intraoral implant model. METHODS: Fifty five-week-old male Wistar rats were allocated to 5 groups: 0.5, 1.0 and 1.5 groups, representing transmucosal segment heights of 0.5, 1.0 and 1.5 mm, respectively, and groups with ipsilateral or contralateral loading-change conditions after initial osseointegration (IL and CL, respectively). The 0.5, 1.0 and 1.5 groups were compared as healing-phase loading groups, and the 1.0, IL and CL groups as post-osseointegration loading-change groups. Outcomes included the bone area fraction (BA%), apparent bone-implant contact (BIC%), tartrate-resistant acid phosphatase (TRAP)- and alkaline phosphatase (ALP)-positive areas, and immunofluorescence for connexin 43 (Cx43) and sclerostin. RESULTS: During healing, the 1.5 group showed higher BA% and ALP-positive area than the 0.5 group, but lower BIC% and more pronounced discontinuity at the crestal bone-implant interface. Cx43-positive area was higher in the 1.0 and 1.5 groups than in the 0.5 group, whereas sclerostin-positive area was lowest in the 1.0 group. After osseointegration, the IL and CL groups showed lower BIC% and greater TRAP-positive area than the 1.0 group, without a significant reduction in BA% over 1 week. Sclerostin corrected intensity was higher in the IL and CL groups than in the 1.0 group. CONCLUSION: Within the limitations of this rat model, peri-implant bone responses to occlusal contact-related conditions were stage dependent. Greater or preserved peri-implant bone area did not necessarily indicate continuous bone-implant contact, supporting the concept of bone area-interface decoupling. CLINICAL RELEVANCE: Implant occlusion should be managed as a daily, dynamic condition, with contact control during healing and continued reassessment during maintenance, even when bone levels appear stable.