Stronger than Ever: Multifilament Fiberglass Posts Boost Maxillary Premolar Fracture Resistance

This paper investigates the influence of cavity configuration and post-endodontic restoration on the fracture resistance, failure mode and stress distribution of premolars by using a method of fracture failure test and finite elements analysis (FEA) coupled to Weibull analysis (WA). One hundred premolars were divided into one control group (G(contr)) (n = 10) and three experimental groups, according to the post-endodontic restoration (n = 30), G(1), restored using composite, G(2), restored using single fiber post and G(3), restored using multifilament fiberglass posts (m-FGP) without post-space preparation. Each experimental group was divided into three subgroups according to the type of coronal cavity configuration (n = 10): G(1O), G(2O,) and G(3O) with occlusal (O) cavity configuration; G(1MO), G(2MO), and G(3MO) with mesio-occlusal (MO); and G(1MOD), G(2MOD), and G(3MOD) with mesio-occluso-distal (MOD). After thermomechanical aging, all the specimens were tested under compression load, and failure mode was determined. FEA and WA supplemented destructive tests. Data were statistically analyzed. Irrespective of residual tooth substance, G(1) and G(2) exhibited lower fracture resistance than G(contr) (p < 0.05), whereas G(3) showed no difference compared to G(contr) (p > 0.05). Regarding the type of restoration, no difference was highlighted between G(1O) and G(2O,) G(1MO) and G(2MO,) or G(1MOD) and G(2MOD) (p > 0.05), whereas G(3O,) G(3MO,) and G(3MOD) exhibit higher fracture resistance (p < 0.05) than G(1O) and G(2O), G(1MO) and G(2MO), and G(1MOD) and G(2MOD), respectively. Regarding cavity configuration: in G(1) and G(2,) G(1O) and G(2O) exhibited higher fracture resistance than G(1MOD) and G(2MOD), respectively (p < 0.05). In G(3), there was no difference among G(3O), G(3MO) and G(3MOD) (p > 0.05). No difference was found among the different groups and subgroups regarding the failure mode. After aging, premolars restored with multifilament fiberglass posts demonstrated fracture resistance values comparable to those of an intact tooth, irrespective of the different type of cavity configuration.