Effects of critical thermal cycling on the flexural strength of resin composites

Abstract

We compared flexural strength (FS) infour resin composites before and after three protocols for thermal cycling aging. Four resin composites were evaluated: Enamel Plus Hri, Gradia Direct Posterior, Grandioso, and Grandioso Flow. Sixty specimens (2 × 2 × 25 mm) were fabricated using a split metallic mold and light-cured for 30 s. The specimens were then randomly divided into four groups and tested using one of the following thermal cycling procedures: 1) storage in deionized water for 24 h (control group), 2) 15,000 cycles, 3) 30,000 cycles, and 4) 45,000 cycles. Each thermal cycling procedure was conducted between 5°C and 55°C, with a dwell time of 30 s. All specimens were subjected to a three-point bending test, to determine FS (0.5 mm/min). "Material" and "thermal aging" were significantly associated with FS (P < 0.001). A statistically significant interaction between the two factors was also detected (P < 0.001). In the non-aged groups, nanohybrid composites had the highest FS. FS significantly decreased after thermal cycling protocols in all composites tested.

Effect of Airborne Particle Abrasion on Microtensile Bond Strength of Total-Etch Adhesives to Human Dentin

“…Artificial aging, performed using critical thermal cycles, could have influenced the mean values of microtensile bond strength registered, as confirmed by literature [ 25 , 26 ]. Although thermal cycling is one of the most widely aging method used, there is an apparent lack of a standardized protocol [ 25 ].…”

“…Following adhesive application, four increments of resin composite (Herculite XRW Ultra-A2 Dentin; Kerr Corporation) of about 1 mm were built up and individually light activated for 40 seconds (Bluephase C8, Ivoclar Vivadent AG) on each specimen. After restorative procedures described above, specimens were stored in distilled water at 37°C for 24 h and then underwent 30,000 thermal cycles in deionized water from 5°C to 55°C, with a 30-second dwelling time and 5-second transfer between temperature baths (LTC100; LAM technologies Electronic Equipment, Firenze, Italy) [ 25 , 26 ].…”

Effect of Bleaching and Thermocycling on Resin-Enamel Bond Strength

“…Therefore, in the current study we examined composite materials differing in matrix and filler composition, including a nanofilled composite, methacrylate-based (Z350), and microfilled hybrid composite, silorane-based (P90). Although filler volume of resin composites may have important role in mechanical properties, but the complex chemical composition of composites (matrix, filler size, distribution, and filler-resin coupling) is responsible for the different performance characteristics of these materials [ 23 ]. Degradation of composite resins in the oral environment is attributed to the resin matrix, filler particles, and hydrolytic instability of the silane coupling agent at the polymer-silica interface [ 24 ].…”

The Effect of Thermocycling and Surface Treatments on the Surface Roughness and Microhardness of Three Heat-Pressed Ceramics Systems

“…In the research field, commonly used bath temperatures of 5 • C and 55 • C for testing dental materials. Ten thousand cycles are approximately the equivalent to a year in the oral environment, based on the idea that dental restorations are subjected to 20 changes of temperature per day [31][32][33][34][35][36][37][38][39][40][41]. This study investigated the effect of thermocycling and different surface treatments (polishing and glazing) on the microstructure, surface roughness, and microhardness of three types of heat-pressed glass-ceramic.…”