The effect of thermocycling on the degree of conversion and mechanical properties of a microhybrid dental resin composite

Abstract

ObjectiveThe purpose of this study was to investigate the degree of conversion (DC) and mechanical properties of a microhybrid Filtek Z250 (3M ESPE) resin composite after aging.MethodThe specimens were fabricated using circular molds to investigate Vickers microhardness (Vickers hardness number [VHN]) and DC, and were prepared according to ISO 4049 for flexural strength testing. The initial DC (%) of discs was recorded using attenuated total reflectance-Fourier transforming infrared spectroscopy. The initial VHN of the specimens was measured using a microhardness tester under a load of 300 g for 15 seconds and the flexural strength test was carried out with a universal testing machine (crosshead speed, 0.5 mm/min). The specimens were then subjected to thermocycling in 5°C and 55°C water baths. Properties were assessed after 1,000–10,000 cycles of thermocycling. The surfaces were evaluated using scanning electron microscopy (SEM). Data were analyzed using 1-way analysis of variance followed by the Tukey honest significant difference post hoc test.ResultsStatistical analysis showed that DC tended to increase up to 4,000 cycles, with no significant changes. VHN and flexural strength values significantly decreased upon thermal cycling when compared to baseline (p < 0.05). However, there was no significant difference between initial and post-thermocycling VHN results at 1,000 cycles. SEM images after aging showed deteriorative changes in the resin composite surfaces.ConclusionsThe Z250 microhybrid resin composite showed reduced surface microhardness and flexural strength and increased DC after thermocycling.

Evaluation of the repair capacities and color stabilities of a resin nanoceramic and hybrid CAD/CAM blocks

“…[13][14][15] Thermocycling is an effective procedure for aging dental materials that affects the physical properties and repair bond strength of the dental materials. 16,17 In an esteemed study, it has been reported that 10,000 thermal cycles can correspond to 1 year. 18 Thermocycling process adversely affects the physicochemical properties and the number of unreacted double bonds decreases on the surface of the composite structure.…”

Influences of Successive Exposure to Bleaching and Fluoride Preparations on the Surface Hardness and Roughness of the Aged Resin Composite Restoratives

“…The micro-hybrid type, at the same time, seemed more resistant to the erosive effect of the APF gel, as such surfaces showed lower roughness values than the other types of tested resin composites. Since the restorative composite degradation appears to depend on the filler size distribution through the number of matrix–filler interfaces, this finding could be referred to the material’s higher volumetric filler loading with different size distributions that allow minimal resin content to be exposed to the erosive acidic environment ( Table 1 ) [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , ...…”

“…To simulate the clinical situation, all specimens were then finished using fine composite finishing diamonds (Brasseler USA Dental, Savannah, GA) and serially polished with 2 Sof-Lex discs (#1982SF and 2382SF, 3M ESPE, St. Paul, MN, USA), each used for for 10 s, under copious air–water cooling. The process of simulated aging was then started by storing all specimens in water at 37 ± 1 °C for 24 h (FUNCTION Line incubator, Thermo Electronic Inc., Lagenselbold, Germany), followed by thermocycling at 5–55 °C for 10,000 cycles with 1 min dwell time (MSCT-1 Thermocyler, São Carlos, SP, Brazil) that almost equivalent to 1 year of aging [ 27 ].…”

“…Subgroup 2 (SG2) specimens were first subjected to thorough air-drying for 60 s before we coated each of their top surfaces with a 0.5–1 mm thick layer of a chemically-activated in-office bleaching gel (Opalescence Boost PF, Ultradent Products Inc, South Jordan, UT, USA) using the recommended syringe tips. The applied bleaching preparation was kept on specimens’ surfaces for 60 min (3 times X 20 min interval) before suctioning the applied gel and washing the composite surfaces with air–water spray for 15 s. The same bleaching procedure was repeated for the same specimens for 2 more times alternated with periods of 5000 thermal cycles each representing 6 m of intra-oral service [ 27 , 28 , 29 ]. Subgroup 3 (SG3) specimens were first subjected to thorough air-drying for 60 s before coating their top surfaces with acidulated phosphate fluoride gel that releases 1.23% fluoride ions (APF gel, Deepak Inc., Miami, FL, USA).…”

Avaliação do efeito da termociclagem nas propriedades ópticas e na rugosidade superficial de duas resinas compostas comerciais

“…Os altos valores iniciais de MV observados em ambos os materiais (ES=80,22 ± 7,08; Z350XT=100,56 ± 1,68) podem estar associados ao tamanho das partículas presentes na composição dos materiais pois ambas são resinas nanoparticuladas, o que lhes confere boas propriedades mecânicas 42 . No entanto, após 2 mil ciclos de envelhecimento térmico, observou-se uma redução acima de 10% na microdureza dos materiais, o que está de acordo com resultados reportados para resinas microhíbridas na literatura 17 .…”