Long-term biological complications of dental implants placed either in pristine or in augmented sites: A systematic review and meta-analysis

Aim: To investigate and compare the prevalence of biological complications and failure of implants placed in pristine vs. augmented sites after a mean observation period of at least 10 years. Materials and methods: The focused question "In patients with osseointegrated dental implants, are there differences in biological complications and implant failure at implants placed in pristine vs. augmented sites?" was addressed using the Population, Exposure, Comparison and Outcome criteria. Electronic and manual searches supplemented by the screening of the grey literature were carried out. A case definition of peri-implant mucositis and peri-implantitis had to be specified. The binary random-effects method was chosen to conduct meta-analyses. Results are presented as Forest plots with weighted mean values and 95% confidence intervals (CI). The I-2 statistic test was applied to quantify heterogeneity. The Newcastle-Ottawa Scale and the parameters provided in the Cochrane Center and CONSORT statement were used for quality assessment. The results are reported according to the PRISMA guidelines. Results: No randomized clinical trial (RCT) comparing the outcomes of implants placed in pristine vs. augmented sites was identified. Five case-series studies, one case-control study, one cross-sectional study and one RCT were eligible for qualitative and quantitative analyses. No statistically significant differences (p >.05) were observed between implants placed in pristine vs. augmented sites for any outcome variables both at patient and at implant levels, respectively. High heterogeneity concerning patient sampling, case definitions of biological complications and eligibility criteria was observed. Conclusion: The studies included in the present systematic review did not directly address the focused questions. Hence, the outcomes of the meta-analysis should be interpreted with caution due to high variability with respect to study design.