Estudo de propriedades físico-químicas e mecânicas de resinas compostas pré-aquecidas

Abstract

The interest of using composite resins as cements for indirect restorations has been growing over time, through the reduction in viscosity achieved by preheating. However, there are few studies comparing preheated resins with resin cements. Therefore, the purpose of this study was to evaluate the effect of preheating on physical-chemical and mechanical properties of composite resins for cementing dissilicate of lithium ceramic restorations (IPS e.max Press, Ivoclar Viva) through laboratory tests. The composite resins were heated to 69°C in a dental heating device (HotSet - Technolife) before light curing. In Chapter I, two preheated composite resins, microhybrid (Filtek Z250 - 3M ESPE) and nanohybrid (Filtek Z350XT- 3M ESPE) were used, in comparison with two resin cements, dual (RelyX ARC-3M ESPE) and light cured (RelyX Veneer - 3M ESPE). Degree of conversion by Fourier transform infrared spectroscopy (FTIR), flexural strength, elastic modulus, fracture toughness, sorption and solubility, flow, color stability and microshear bond strength were performed. In Chapter II, three preheated resins were used: microhybrid (Filtek Z100 – MESPE), regular consistency bulk-fill (Opus APS – FGM) and thermoviscous bulk-fill (Viscalor – VOCO), compared to a flowable bulk-fill (Opus APS Flow - FGM) and a light-curing resin cement (RelyX Veneer - 3M ESPE). The following tests were performed: degree of conversion by Fourier transformed infrared spectroscopy (FTIR), film thickness, color stability and microshear bond strength. The statistical analyses were performed by ANOVA and post-hoc Holm-Sidak tests (α=0,05). In Chapter I, the results showed no effect of preheating on degree of conversion, flexural strength, fracture toughness, solubility or enamel-bond strength (p>0,05), but increased sorption and reduced ceramic-bond strength (p<0,05). The flow of resins increased after heating, but it was inferior to resin cements (p<0,05). Color stability was more affected in preheated composite resins than in resin cements. In Chapter II, Opus showed a higher degree of conversion compared to Z100 and Viscalor resins (p<0,05), similarly to flowable resin. The film thickness of preheated resins was higher compared to flowable resin and resin cement (p<0,001). In enamel, the bond strength of Viscalor resin was superior to Veneer cement (p<0,001). In ceramics, the bond strength of preheated resins was higher than resin cement (p<0,05). Color stability was significantly influenced by the factor time (p<0,05), but there was no difference between materials (p>0,05). After water storage, all materials showed color alteration over time. It was concluded that preheating resulted in little or no benefit to the properties tested compared to flowable resin and resin cements. Thus, resin cements seem to be the best option for cementing indirect restorations.