Biological and technical complications of tilted implants in comparison with straight implants supporting fixed dental prostheses. A systematic review and meta-analysis

Objectives: To evaluate the implant failure, marginal bone loss (MBL), and other biological or technical complications of restorations supported by tilted and straight implants after at least 3 years in function.

Methods: Electronic and manual searches were performed in MEDLINE, Embase, Web of Science, and OpenGrey to identify clinical studies published up to December 2017. After duplicate study selection and data extraction, the risk of bias was assessed with the ROBINS-I tool. Random-effects meta-analyses of relative risks (RRs) or mean differences (MD) and their 95% confidence intervals (CIs) were performed, followed by subgroup/sensitivity analyses and application of the GRADE approach.

Results: A total of 17 nonrandomized studies (eight prospective/nine retrospective) were included. The number of implants of the overall systematic review was 7,568 implants placed in 1,849 patients supporting either full-arch or partial implant prostheses. No difference in the failure of tilted and straight implants was seen (eight studies; 4,436 implants; RR = 0.95; 95% CI = 0.70 to 1.28; p = 0.74), with the quality of evidence being very low due to bias and imprecision. Likewise, no difference in MBL was seen between tilted and straight implants (16 studies; 5,293 implants; MD = 0.03 mm; 95% CI = -0.03 to 0.10 mm; p = 0.32), with the quality of evidence being very low due to bias and inconsistency. Contradictory results regarding implant survival were found from prospective and retrospective studies, which could indicate bias from the latter.

Conclusions: Within the limitations of the present systematic review, no effect of implant inclination on implant survival or peri-implant bone loss was found.