The Effect of Crown-to Implant Ratio on the Clinical Outcomes of Dental Implants: A Systematic Review

Purpose: To analyze the effect of crown-to-implant (C/I) ratio over survival rate, marginal bone loss, and prosthetic complications of dental implants. Materials and Methods: Electronic (PubMed [MEDIAE], Embase, and Cochrane Central) and manual searches for clinical trials with a minimum follow-up of 1 year were performed. Clinical and anatomical C/I ratios were obtained. Regression models were created to assess for potential correlation between C/I ratio (anatomical and clinical) and survival rate, marginal bone loss, or prosthetic complications. A subgroup analysis of 6-mm implants and a comparison of C/I ratios of > 1.5 vs <= 1.5 were also performed. The Newcastle-Ottawa Scale and Cochrane Risk of Bias Tool For Randomized Controlled Trials were used to evaluate the risk of bias. Results: An overall moderate risk of bias was assessed among the selected articles. Linear regression analysis did not reveal a significant correlation between anatomical C/1 ratios and survival rate (P = .905), marginal bone loss (P = .33), or prosthetic complications (P = .67). Similarly, no significant correlation to survival rate and marginal bone loss (P = .42, P = .84) was observed in the articles providing the clinical C/I ratios. Conclusion: Increased C/I ratio does not seem to be directly related with increased marginal bone loss and does not represent a biomechanical risk factor for the stability of the prosthesis and for the survival of dental implants.