Mechanical properties, fracture resistance, and fatigue limits of short fiber reinforced dental composite resin

Statement of problem. Cycling masticatory loads decrease the strength of particulate filler composites (PFCs) and initiate the failure process by fatigue. The life expectancy of a composite resin restoration under stress remains difficult to predict. Purpose. The purpose of this study was to determine the fracture resistance and the compressive fatigue limits (CFL) of anterior crown restorations made of a short-fiber reinforced composite resin (SFC), to investigate selected mechanical properties of the material following standard test methods, and to observe their correlation with the CFL. Material and methods. Specimens (n=10) were fabricated either from SFC (everX Posterior, GC Corp) or PFC (G-aenial anterior, GC Corp). The properties investigated were flexural strength (FS), compression strength (CS), diametral-tensile strength (DTS), and single-edge-notched-bend fracture toughness (FT) following ISO standards. Fracture resistance was determined by static load (n=10) and the CFL at 10 000 cycles was determined using a staircase approach (n=20), both on anterior composite resin crowns. The results were analyzed with 1-way ANOVA (alpha=.05) or 2-way ANOVA (alpha=.05) followed by a Tukey B post hoc test and the Pearson-correlation analysis. Results. The SFC crowns had higher fracture resistance (954 +/- 121 N) than the PFC crowns (415 +/- 75 N) (P<.001) and higher CFL (267 +/- 23 N) than the PFC crowns (135 +/- 64 N) (P<.001). SFC revealed also higher FT (2.6 +/- 0.6 MPa.m(1/2)) than the PFC (1.0 +/- 0.2 MPa.m(1/2)) (F=69.313, P<.001). A significant correlation was observed only between the FT and the CFL (r(2)=0.899; P<.001). Conclusions. SFC crowns showed good performance under static and fatigue loading. FT was the only in vitro test method that filtered as a clinically relevant parameter.