The influence of implant diameter on its survival: a meta-analysis based on prospective clinical trials

The use of narrow-diameter implants has been proposed to restore small edentulous spans, thus avoiding extensive bone augmentation procedures and reducing the surgical complexity of implant rehabilitations. Although success rates of narrow-diameter implants have already been analyzed in the literature, to the best of the authors' knowledge, no meta-analysis based on prospective and randomized controlled trials has been performed. The aim of this study is to analyze the survival rates of narrow-diameter implants compared with standard or wide-diameter implants.

An electronic search from three databases and a hand search in implant-related journals of studies published in English before September 1, 2012 were performed. Prospective human clinical studies with at least 10 implants and a follow-up period of 1 year were included in the meta-analysis. Implants were divided into two groups based on their diameters.

The initial search yielded 484 articles, of which 49 were evaluated in full text for eligibility. Finally, 16 studies were chosen and separated into two groups: 1) implants of diameter <3.3 mm (group 1) and 2) implants of diameter ≥3.3 mm (group 2). A meta-analysis performed for groups 1 and 2 showed survival rates of 75% and 87%, respectively.

This meta-analysis showed that narrower implants (<3.3 mm) had significantly lower survival rates compared with wider implants (≥3.3 mm). Other variables, such as type of prosthesis, implant surface, and timing of prosthetic loading, were found to have influenced the implant survival rates.