Effect of Temperatures on Polymerization Stress and Microleakage of Class V Composite Restorations

Abstract

The loss of interfacial integrity was identified as one of the major causes for replacement of resin composite restorations. Preheating procedure has been proven to enhance flowability and adaptation of resin composites and increase their degree of conversion. The purpose of this study was to investigate polymerization contraction stress produced in resin composites after preheating to 37˚C and 60˚C, and measure microleakage of Class V restorations restored with preheated composites. Three resin composites (GC Kalore, Gradia Direct X, Filtek Supreme XT) at room temperature, 37˚C, and 60˚C were investigated. Maximum contraction stress of the composites (n = 5) was evaluated in a modified lowcompliance device. Samples were light-cured for 40 seconds and the maximum force was recorded during 15 minutes. Calculations were done to adjust for the system's compliance and obtain linear shrinkage values of composites. Data were analyzed by Multivariated Analysis of Variance (MANOVA) and Tukey's test for multiple comparisons (α = 0.05). Seventy-two Class V cavities were prepared on the buccal surfaces of extracted premolars and divided into 9 groups. The teeth were restored with composites at 3 temperatures and were thermo-cycled between 5˚C and 55˚C with a one-minute dwell-time for 1000 cycles. The teeth were sealed with wax and nail vanish before placed in 0.5% toluidine blue dye for 24 hours. The teeth were embedded in self-curing resin and sectioned bucco-lingually with a slow-speed diamond saw, providing 3 sections per restoration. Microleakage was rated by two evaluators using a 0-4 ordinal scale at the occlusal and cervical margins under light microscope. Microleakage data were analyzed with Kruskal-Wallis ANOVA and Mann-Whitney U test (α = 0.05). Results indicate that preheating composites to 37˚C and 60˚C significantly increased polymerization contraction stress of composites (p < 0.05). A significantly greater amount of leakage was found at the cervical margins (p < 0.05). For all tested materials, preheating composites to 60˚C resulted in significantly less microleakage at the cervical margin.

The effect of composite resin preheating on marginal adaptation of class II restorations

“…It has been demonstrated that preheating composite resin decreases its viscosity and thickness, increasing its flow and adaptation with the cavity walls ( 5 , 6 ). In addition, preheating increases the polymerization rate and microhardness of composite resin, improving its physicomechanical properties ( 7 ). The effect of heat, due to a preheated composite resin, on the increase in pulpal temperature is minimal (approximately 2°C), which can be tolerated by the pulp.…”

Micro-Leakage of Preheated Composite as a Cementation Material in Indirect Adhesive Restoration (Literature Review)

“…Several studies have been conducted The use of preheating technique on composites as cementation material with a temperature of 60°C led to a significant reduction in microleakage at the cervical margin. 12 This is contrary to the results which show that the greater the temperature, the greater the marginal fit. 12 This study examines the microleakage rate of preheated composites in the use of cementation materials.…”

“…12 This is contrary to the results which show that the greater the temperature, the greater the marginal fit. 12 This study examines the microleakage rate of preheated composites in the use of cementation materials. Microleakage is an important indicator to determine the success of restorative material.…”

“…11 In contrast, Didron et al stated that the use of composites as cementation materials by preheating at 60°C led to a significant reduction in micro-leakage at the cervical margin. 12 According to several studies, there is still a controversy that preheating of the composite resin technique can eliminate the leakage rate of the micro composite during cementation.…”

Microleakage difference between total-etch and self-etch bonding in bulk fill packable composite restoration after carbonic acid immersion

“…Each sample was then assessed by three observers by means of a stereomicroscope (Zeiss® Stremi DV4, Germany) at 15x magnification. The microleakage was then evaluated with a scoring method based on that proposed by Didron et al (2013), 18 namely; 0 = no colour penetration; 1 = colour penetration up to half of the cavity wall; 2 = total colour penetration of the cavity wall; 3 = colour penetration up to half of the axial wall; and 4 = colour penetration more than half of the axial wall ( Figure 1).…”