The influence of customization of glass fiber posts on fracture strength and failure pattern: A systematic review and meta-analysis of preclinical ex-vivo studies

To perform a systematic review of the literature focused to evaluate in vitro function of prefabricated fiber posts with and without customization by additional auxillary fiber posts and composite resin on the fracture strength of wide or enlarged canals and the failure pattern. Six databases were used as primary search sources (PubMed, Scopus, LILACS, SciELO, Science Direct, and Web of Science) and three databases (Open Grey, Open Thesis, and OATD) were used to partially capture the “grey literature”. The research included laboratory studies that used human upper anterior teeth aiming to assess the fracture strength and failure pattern of different glass fiber post customizations by additional auxiliary fiber posts or composite resin. The search had no restriction of year, language, and publication status. The risk of bias of the studies was assessed from the criteria established in systematic reviews of laboratory studies. Standardized mean differences were calculated by comparing the mean fracture strengths of customized and non-customized posts. Pooled estimates were calculated by Glass' delta method using the random-effects model. Subtotal estimates were presented according to each type of relining procedure and an overall estimate was described considering all studies combined. The search provided 2291 results, from which six met the eligibility criteria and were included in the qualitative assessment of the review. Only three studies presented a moderate risk of bias. The meta-analysis results showed that the use of auxiliary posts produced higher mean fracture strengths than non-customized posts (SMD = 2.21; 95%CI: 0.74; 3.68), and it was more effective than the use of composite resin to reline the posts. Based on laboratories studies, even though has not been observed any difference to a statistically significant level on fracture strength and failure pattern of the customized and non-customized post, future studies should follow a standardized approach to implementation and reporting of data.