The influence of crown-to-implant ratio in single crowns on clinical outcomes: A systematic review and meta-analysis

A consensus about the effect of crown-to-implant (C/I) ratio in single crowns regarding the implant survival rate and marginal bone loss (MBL) is lacking. The purpose of this systematic review and meta-analysis was to evaluate the influence of C/I ratio in implant-supported single crowns on clinical outcomes. The search was made in the PubMed/MEDLINE, Scopus, and the Cochrane Library databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria and registered with the International Prospective Register of Systematic Reviews (PROSPERO: CRD42018095711). The focused question was “Does the crown-to-implant ratio influence clinical outcomes for implant-supported single crowns?” Five direct comparative studies were included (C/I ratio ≤1 or >1, or ≤2 or >2), including a total of 262 participants with a mean age of 54.5 years. The meta-analysis comparing C/I ratio between ≤1 or >1 revealed no significant differences (P=.18; risk difference:-0.05; 95% confidence interval: -0.11 to 0.02) in terms of implant survival rate; the same was true for C/I ratio between 1 (0.07 mm [-0.29 to 0.22]);