Influence of Pre-Heating Regular Resin Composites and Flowable Composites on Luting Ceramic Veneers with Different Thicknesses

Abstract

The aim of this study was to evaluate of pre-heating, filler contents and ceramic thickness on film thickness, microshear bond strength, degree of conversion and color change on ceramic veneers. Two experimental composites were prepared (Bis-GMA/UDMA/BisEMA/ TEGDMA), with different amounts of filler (65% or 50%wt) simulating a conventional and a flowable composite. The flowable (F) was used at room temperature and, the conventional either at room temperature (C) or pre-heated (CPH). Disk-shaped ceramics with different thickness (0.4 mm, 0.8 mm, 1.5 mm) were prepared. The film thickness was evaluated according to the ISO 4049 (n=10). The microshear bond strength (n=10) was evaluated in enamel using tubing specimens light-cured through the ceramic veneer. The degree of conversion was evaluated using Raman spectroscopy. The color change of the ceramic restorations (n=10) was evaluated by spectrophotometry. The results were submitted to 2-way ANOVA and Tukey’s post hoc test (a=5%). For the film thickness 1-way ANOVA was used (a=5%). The C presented the thicker film thickness; the CPH produced a similar film thickness in comparison to the F. All composites showed similar microshear bond strength. The degree of conversion of the F was higher than the C and CPH. The degree of conversion of the composites photo-activated through a 0.4 mm was higher than the composites photo-activated through thicker ceramics. The C showed the highest color change, while the CPH showed similar color change to the F. In conclusion, pre-heated conventional composites seem to be a potential alternative to lute ceramic veneers such as the flowable composites.

Effect of Preheating Cycles on Microshear Bond Strength of Nanohybrid Resin Composite Luted to CAD/CAM Ceramic

“…In the present study it was observed that the prewarming of nanohybrid resin composite reduced its film thickness to be similar to the film thickness of resin cement, and it is well known that film thickness is an important factor when luting indirect restorations because thick film thickness leads to marginal misfit, allows great amount of resin material to be polymerized with great volumetric shrinkage and so high susceptibility of failure. (7) In accordance to the observations of this study, Sampaio et al (22) found that the thinner film thickness was formed by the pre-heated conventional composite, probably that occurred because temperature increased agitation of molecules and allowed mass plasticization of unpolymerized material. Moreover preheating provides a lute with a smaller coefficient of thermal expansion, with less polymerization shrinkage and with greater wear resistance at restoration margins compared to conventional resin luting cement.…”

“…Each ceramic plate was embedded in a wax block prior to surface treatment, in order to facilitate handling and fixation during micro-shear testing. Plates surfaces were treated with 9.5 % porcelain acid etch 7 for 60 seconds then washed for 180 seconds with air/water spray and finally dried with hot air blower in order to insure complete removal of the acid.…”

Influence of thickness and translucency of lithium disilicate ceramic on degree of conversion of resinous materials

“…Metal-free ceramic restorations such as veneers, inlays, onlays, and crowns have been routinely used in clinical practice ( 1 , 2 ), mainly due to its good optical, physical, chemical, and biological properties ( 3 , 4 ). However, success of these restorations is highly dependent of an effective adhesion between ceramic, resin cement, and dental tissues ( 5 - 8 ).…”

“…Resin cement is usually the choice for bonding metal-free indirect esthetic restorations ( 3 , 4 , 8 , 9 ) and its polymerization modes can be divided in chemical, physical (light curing), and dual, which combines the desirable properties from physical and chemical activation ( 4 , 6 , 10 , 11 ). Dual system has been developed to compensate the polymerization deficiencies in attenuated light or its absence, enabling its indication in different clinical situations, resulting in superior properties compared to chemically activated cements ( 6 , 12 ).…”

“…In order to minimize this problem, amine free resin cements have been recently introduced in market to promote the esthetic longevity of indirect restorations ( 13 , 14 ). Flowable composite can also be used ( 8 ), but these systems have physical activation only, and it is estimated that the light irradiance emitted by light curing unit that reaches the cement is reduced when it passes through the ceramic, reducing the degree of conversion (DC) and consequently the mechanical properties of material, which may affect the durability of indirect restorations ( 6 , 11 , 13 , 15 , 16 ). This event is dependent on light intensity, curing unit, ceramic thickness, opacity, among others ( 5 , 9 , 13 , 15 , 17 ).…”