Ferrule Effect: A Meta-analysis

The aim of this study was to systematically review the literature for laboratory and clinical studies to evaluate the effect of ferrule in restored endodontically treated teeth. The search was conducted in 2 databases (PubMed, Scopus) with no publication year/language limits. From 1,872 potentially eligible studies, 124 studies were selected for full-text analysis, and 37 were included for review, with 32 of those considered in the meta-analysis and 5 considered in the survival analysis. Two reviewers independently selected the studies, extracted the data, and assessed the risk of bias. For laboratory studies, a meta-analysis was performed for the comparison of the fracture resistance of teeth with and without ferrule, and 3 subgroup analyses were conducted for ferrule height, post type, and type of tooth. For clinical studies, the Kaplan-Meier method was used to determine the survival of restorations, with log-rank test used to identify differences between groups ( α = 5%). Teeth without ferrule had a lower fracture resistance ( P < 0.00001), and the higher the height of ferrule, the greater the fracture resistance was, irrespective of the type of post ( P < .000001). Teeth with ferrule had higher clinical longevity ( P = 0.002); however, the presence of a ferrule was related to higher survival only for premolars ( P = 0.05). In conclusion, the presence of a ferrule is responsible for an improvement in the fracture resistance of the restoration in laboratory studies. Yet, other clinical factors besides the ferrule may be associated with survival in molars and anterior teeth and need to be further investigated. Knowledge Transfer Statement: The results of this study can be used by clinicians when deciding which approach to use when planning the restoration of endodontically treated teeth with and without ferrule. Ferrule may lead to higher tooth/restoration survival, while tooth location may influence therapeutic decisions.