Transmission of composite polymerization contraction force through a flowable composite and a resin-modified glass ionomer cement

Abstract

The purpose of this study was to evaluate the individual contraction force during polymerization of a composite resin (Z-250), a flowable composite (Filtek Flow, FF) and a resin-modified glass ionomer cement (Vitrebond, VB), and the transmission of Z-250 composite resin polymerization contraction force through different thicknesses of FF and VB. The experiment setup consisted of two identical parallel steel plates connected to a universal testing machine. One was fixed to a transversal base and the other to the equipment's cross head. The evaluated materials were inserted into a 1-mm space between the steel plates or between the inferior steel plate and a previously polymerized layer of an intermediate material (either FF or VB) adhered to the upper steel plate. The composite resin was light-cured with a halogen lamp with light intensity of 500 mW/cm2 for 60 s. A force/time graph was obtained for each sample for up to 120 s. Seven groups of 10 specimens each were evaluated: G1: Z-250; G2: FF; G3: VB; G4: Z-250 through a 0.5-mm layer of FF; G5: Z-250 through a 1-mm layer of FF; G6: Z-250 through a 0.5-mm of VB; G7: Z-250 through a 1-mm layer of VB. They were averaged and compared using one-way ANOVA and Tukey test at a = 0.05. The obtained contraction forces were: G1: 6.3N ± 0.2N; G2: 9.8 ± 0.2N; G3: 1.8 ± 0.2N; G4: 6.8N ± 0.2N; G5: 6.9N ± 0.3N; G6: 4.0N ± 0.4N and G7: 2.8N ± 0.4N. The use of VB as an intermediate layer promoted a significant decrease in polymerization contraction force values of the restorative system, regardless of material thickness. The use of FF as an intermediate layer promoted an increase in polymerization contraction force values with both material thicknesses.

Marginal microleakage of class II composite resin restorations due to restorative techniques

“…So this could encourage the creation of an elastic layer in the cervical margins, just having high polymerization shrinkage, generating high stress at the interface of bonding (10). This is in accordance to Castañeda-Espinosa et al (24), who described that the use of a flowable composite as an intermediate layer (0.5 or 1mm) promoted an increase in shrinkage stress force values. The G3 (pre-cured spheres) had the lowest extent of penetration of the dye when compared with other groups, although this was not statistically significant.…”

The Influence of Elastic Modulus of Base Material on the Marginal Adaptation of Direct Composite Restoration

“…A comparison with results from Group 5 suggested that the IM% did not depend completely on the elastic modulus of the base material. The polymerization shrinkage stress of RMGIC is much lower than that of the composites, 4 and the RMGIC under the composites reduced the level of polymerization shrinkage of the composites. 24 Cuspal deflection was also lower in the MOD cavity when RMGIC was used as a base material than that in the cavity restored with the composite only.…”

“…[1][2][3][4][5] However, this so-called sandwich technique has not been confirmed and some researchers have reported that this technique did not offer any added advantage. [6][7] Opdam and others, 8 in their recent study, indicated that a total-etch restoration with a highly filled hybrid resin composite showed higher clinical survival than a closed-sandwich restoration, and the main reason for failure in the GIC-based composite restorations was a fracture of the composites.…”

Internal adaptation of resin composite restorations with different thicknesses of glass ionomer cement lining

“…It is assumed that adhesion between the resin composite and glass ionomer might be higher than that between GIC and dentin at the pulpal floor. Thus, the stress developed by polymerization contraction of the resin composite to GIC lining tends to disrupt the cement–dentin bond at the pulpal floor, rather than the resin composite–GIC bond …”