Marginal bone loss around bone-level and tissue-level implants: A systematic review and meta-analysis.

PURPOSE: To review the scientific evidence regarding the marginal bone loss around the tissue-level and bone-level implants. METHODS: MEDLINE-PubMed and EMBASE databases were searched for the relevant English articles (up to February 2019) assessing the marginal bone loss (MBL) as the primary outcome. To be selected, studies were supposed to directly mention "tissue-level" and "bone-level" implants or implants with and without a smooth neck. Relevant data were extracted and meta-analysis was performed to evaluate the effect of implant neck design. RESULTS: A total of 19 studies (10 clinical, and 9 RCT studies) were included for qualitative analysis. There was a vast heterogeneity between studies in terms of implant designs and study protocol. Out of 19 articles included, 11 studies reached to a statistically significant difference in MBL between the groups; however, the differences were not found to be clinically relevant. Bone-level implants with platform-switched abutments in most of the cases showed better marginal bone stability compared to tissue-level implants or bone-level implants with matching abutments. Seven RCTs with 12 months follow-up data were selected for meta-analysis (I(2)=93%; heterogeneous), and the results showed less MBL around bone-level implants compared to tissue-level group (WMD=-0.21mm; 95% CI -0.42, 0.00; P=0.06). CONCLUSION: The available data regarding comparison of MBL around bone-level and tissue-level implants are heterogeneous. Bone-level implants with platform switching may better preserve crestal bone.