Tilted versus axially placed dental implants: A meta-analysis

Abstract
Objectives
The purpose of the present review was to test the null hypothesis of no difference in the implant failure rate, marginal bone loss, and postoperative infection for patients being rehabilitated by tilted or by axially placed dental implants, against the alternative hypothesis of a difference.

Methods
An electronic search without time or language restrictions was undertaken in July 2014. Eligibility criteria included clinical human studies, either randomised or not, interventional or observational. The estimates of an intervention were expressed in risk ratio (RR) and mean difference (MD) in millimetres.

Results
The search strategy resulted in 44 publications. A total of 5029 dental implants were tilted (82 failures; 1.63%), and 5732 implants were axially placed (104 failures; 1.81%). The difference between the procedures did not significantly affect the implant failure rates (P = 0.40), with a RR of 1.14 (95% CI 0.84–1.56). A statistically significant difference was found for implant failures when studies evaluating implants inserted in maxillae only were pooled (RR 1.70, 95% CI 1.05–2.74; P = 0.03), the same not happening for the mandible (RR 0.77, 95% CI 0.39–1.52; P = 0.45). There were no apparent significant effects of tilted dental implants on the occurrence of marginal bone loss (MD 0.03, 95% CI −0.03 to 0.08; P = 0.32). Due to lack of satisfactory information, meta-analysis for the outcome ‘postoperative infection’ was not performed.

Conclusions
It is suggested that the differences in angulation of dental implants might not affect the implant survival or the marginal bone loss. The reliability and validity of the data collected and the potential for biases and confounding factors are some of the shortcomings of the present study.

Clinical significance
The question whether tilted implants are more at risk for failure than axially placed implants has received increasing attention in the last years. As the philosophies of treatment alter over time, a periodic review of the different concepts is necessary to refine techniques and eliminate unnecessary procedures. This would form a basis for optimum treatment.