Animal and Human Studies on Peri-implantitis: A Systematic Review

Objective: Animal experiments have been widely used in dental research, but the validity of translating results from animal research to humans has not been assessed. The aim of this systematic review was to quantitatively compare the results of animal studies to those of human studies on peri-implant infections. Methods: literature search was conducted using Medline, CENTRAL and Lilacs databases (up to May 2008). In addition, bibliographies of systematic reviews on peri-implant diseases were manually searched for additional studies. Non-surgical and surgical treatments of peri-implantitis/mucositis conducted in animal models or human trials were compared. Meta-analysis was conducted to investigate the difference in the reported treatment effect between animal and human studies. Changes in pocket probing depth (PPD) and probing attachment level (PAL) from baseline measurements in each treatment group were used as outcome measures. Multilevel meta-regression analysis was performed to test the difference in the treatment effect between animal and human studies by taking into account the follow-up times and the sample sizes (defined as the number of implants) of each study. Results: Single level fixed effects meta-analysis showed that the weighted average PPD reduction was 1.20mm in human studies and 2.01mm in animal studies, and the weighted average PAL reduction was 1.20mm in human studies and 1.74mm in animal studies. The results from meta-regression analysis demonstrated that the estimated PPD reduction at six-month was 1.4mm for human studies and 2.44mm for animal studies. PAL gain and increase in PAL gain per month were also higher in the animal group. Conclusion: Treatment effects of peri-implantitis therapy reported by animal studies appeared to be larger than those by human studies. Therefore, the results from animal models in the treatment of peri-implantitis infection should be interpreted with caution.