ABSTRACT
OBJECTIVES: The aim of this study was to evaluate in vitro the influence of fiber-reinforcement on the fracture strength and fatigue resistance of resin-based composites. METHODS: One hundred rectangular bar-shaped specimens (2 mm x 2 mm x 25 mm) made of resin-based composite were prepared in a stainless steel split-mould: (i) thirty specimens of particulate filler composite (PFC) (Filtek Z100, 3M ESPE, St Paul, MN, USA), (ii) thirty specimens of fiber-reinforced composite (FRC) (Everstick C&B, Sticktech Ltd., Turku, Finland) and (iii) forty specimens of PFC and FRC combined in two longitudinal layers of equal thickness. Each specimen was trimmed into a cylindrical hourglass shape. The fracture strength (cantilever beam test, n=10) and the fatigue resistance (rotating cantilever beam test; staircase method: 10(4) cycles, 1.2 Hz, n=20) were determined. Fracture strength, fatigue resistance and work-of-fracture were calculated. The fracture surfaces of failed specimens were analyzed with SEM. Data was analyzed by logistic regression, one-way ANOVA followed by Tukey's post hoc test and, a Student's t-test. RESULTS: ANOVA revealed that fiber-reinforcement had significant effect (P<0.001) on fracture strength, fatigue resistance, and work-of-fracture. Student's t-test showed significant differences (P<0.001) in fatigue resistance compared to fracture strength. CONCLUSIONS: Within the limitations of this study, the following conclusions can be drawn (i) the fatigue resistance of resin-based composites is lower than their fracture strength and (ii) FRC are more fatigue resistant than PFC or combinations of FRC and PFC.
Subject(s)
Composite Resins/chemistry , Dental Materials/chemistry , Algorithms , Bisphenol A-Glycidyl Methacrylate/chemistry , Dental Stress Analysis/instrumentation , Glass/chemistry , Humans , Materials Testing , Microscopy, Electron, Scanning , Pliability , Polyethylene Glycols/chemistry , Polymethacrylic Acids/chemistry , Polymethyl Methacrylate/chemistry , Rotation , Silanes/chemistry , Silicon Dioxide/chemistry , Stress, Mechanical , Surface Properties , Zirconium/chemistryABSTRACT
PURPOSE: To evaluate the influence of thermal and mechanical load cycling on the microtensile dentin bond strength of two self-etching and one total-etch adhesives. METHODS: The adhesive materials were: a two-step self-etch adhesive (Clearfil SE Bond), a one-step self-etch adhesive (Hybrid Bond), and a total-etch one-step adhesive (Admira Bond). Sixty freshly extracted human third molars were used. In each tooth, a Class I cavity (4 x 4 mm) was prepared in the occlusal surface with the pulpal floor extending about 1 mm into dentin. The teeth were divided into three groups (n=20). Each group was restored with the resin composite Clearfil APX using one of the adhesives. After restoration, 10 teeth in each group were thermocycled between 5 degrees C and 55 degrees C, (dwell time 3 minutes, 5,000 cycles). The same teeth were then mounted in a fatigue loading machine to receive an intermittent load of 125 N at 52 cycles/minute for 4,000 cycles. Subsequently, each tooth was sectioned longitudinally, bucco-lingually and mesio-distally to get rectangular slabs 1-1.2 mm in thickness for the microtensile test. Each slab was then placed in a universal testing machine and tensile load was applied at a cross-head speed of 0.05 mm/minute. RESULTS: Without loading procedures, there was no significant difference in the bond strength of the tested adhesives. In contrast to Admira Bond and Clearfil SE Bond, fatigue loading resulted in a significant reduction of the bond strength for Hybrid Bond when compared to the unloaded restorations.
