Fatigue-resistance of teeth restored with FRC: effect of luting cements

Objectives: to evaluate the effect of different strategies for post cementation on the fatigue resistance of bovine teeth restored with glass-FRC. Methods: root canals of 63 single-rooted bovine teeth (16mm-length) were prepared to 9mm using a preparation drill of a double-tapered fiber post system (White Post DC, FGM). Each specimen was embedded in a PVC using acrylic resin up to 3 mm of the most coronal portion of the specimen and was allocated into seven groups (n=9) based on the strategies for cementation: Gr1- ScotchBond Multi Purpose plus (SBMP)+Relyx ARC resin cement; Gr2- Single Bond+Relyx ARC; Gr3- ED-Primer+Panavia F; Gr4- SBMP+AllCem resin cement; Gr5- Relyx ARC; Gr6- Relyx Unicem ionomer resin cement; Gr7- Relyx Luting 2 glass ionomer cement (adhesive technique: Gr1 to Gr4; no-adhesive technique: Gr5 to Gr7). After cementation, the core build-up was standard made with composite resin (Oppalis, FGM). The specimens were stored for 7 days and submitted the mechanical cycling (50N, 8Hz, 37°C). After fatigue testing, a score was given to each specimen, considering the number of fatigue cycles to fracture the specimens: Score 0- fracture between 0 and 350,000 cycles; Score 1- fracture between 350,001 and 700,000 cycles; Score 2- fracture between 700,001 and 1,050,000 cycles; Score 3- fracture between 1,050,001 and 1,400,000 cycles; Score 4- No root-, post-, or core-fracture and no loss of retention of the post. The scores were submitted to the statistic analysis (Kruskal-Wallis, a=.05). Results: the strategy for post cementation did not affect the resistance to fatigue (P=0.8669). The cohesive fracture of the composite core combined with failure at post-composite interface was the main failure. No de-bonding of post-core from canal was observed. Conclusion: the resistance to fatigue does not appear to depend on the strategy for post cementation. Further studies must be conducted.