Peri-implant bone regeneration in pigs

Purpose: To review the current literature to answer the focused question: in the experimental pig model (population), which types of peri-implant bone defects (exposure) have been used evaluate different modes of therapy and what is their capacity for spontaneous healing and regeneration (outcome)?

Methods: Following PRISMA guidelines, electronic databases were searched for studies reporting peri-implant bone defects in the maxillae or mandibles of pigs. Those studies which reported a control group of untreated defects with assessment of spontaneous regeneration [new bone area (BA)] and/or re-osseointegration [new bone-to-implant contact (BIC)] via quantitative radiography or histomorphometry were included in a random effects meta-analysis for the outcomes BA and BIC.

Results: Overall, 21 studies, mostly performed in the mandibles of minipigs, were included. Most studies reported 'acute' intrabony (circumferential and/or dehiscence; n = 12) or supra-alveolar defects (horizontal; n = 4). Five studies attempted to induce 'chronic' peri-implantitis lesions using ligatures with conflicting results. Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 48.07% BIC (30.14-66%) and 64.31% BA (42.71-85.91%) in intrabony defects, and 52.09% BIC (41.83-62.35%) and 28.62% BA (12.97-44.28%) in supra-alveolar defects. Heterogeneity in the meta-analysis was high (I² > 90%).

Conclusion: Current evidence for peri-implant bone regeneration in pigs is mainly based on acute intrabony defects, which demonstrate a high capacity for spontaneous regeneration and re-osseointegration. The evidence for chronic peri-implantitis is limited and does not clearly indicate a spontaneous progression of the disease in this animal model.