Influence of abutment height on peri-implant marginal bone loss: A systematic review and meta-analysis

Statement of problem. Whether abutment height can influence peri-implant marginal bone loss has not yet been determined. Purpose. The purpose of this systematic review and meta-analysis was to investigate the early and late marginal bone loss around implants with long and short abutment height. Material and Methods. Electronic (PubMed, EMBASE, and Cochrane) and hand literature searches were performed to identify articles published up to May 2018. A random-effects model was used to analyze the weighted mean difference of marginal bone loss between the long and short groups. Potential confounding factors, including implant/abutment connection, healing, and cement- or screw-retained restoration type, were investigated using meta-regression. Results. Fourteen studies fulfilled the inclusion criteria, and 8 were further included in the meta-analysis. Around bone-level implants with a long abutment, marginal bone loss can be reduced significantly in both the early (-0.52 mm; 95% confidence interval [CI]: -0.79 to -0.24; P=.001) and late (-0.53 mm; 95% CI: -1.03 to -0.02; P=.041) period. Among tissue-level implants, however, and compared with the short-abutment group, more bone loss was found during the early stage in the long abutment (weighted mean difference: 0.28 mm; 95% CI: 0.03 to 0.54; P=.031). Meta-regression failed to find any association between confounding factors and early bone loss around bone-level implants. Conclusions. Within the limitation of this systematic review and meta-analysis, abutment height can influence early bone loss around bone-level implants. However, the evidence is insufficient to determine its impact on late bone loss around bone-level implants and early and late bone loss around tissue-level implants.