Abstract
This study evaluated the Knoop hardness and polymerization depth of a dual-cured resin cement, light-activated at different distances through different thicknesses of composite resin. One bovine incisor was embedded in resin and its buccal surface was flattened. Dentin was covered with PVC film where a mold (0.8-mm-thick and 5 mm diameter) was filled with cement and covered with another PVC film. Light curing (40 s) was carried out through resin discs (2, 3, 4 or 5 mm) with a halogen light positioned 0, 1, 2 or 3 mm from the resin surface. After storage, specimens were sectioned for hardness measurements (top, center, and bottom). Data were subjected to split-plot ANOVA and Tukey's test (alpha=0.05). The increase in resin disc thickness decreased cement hardness. The increase in the distance of the light-curing tip decreased hardness at the top region. Specimens showed the lowest hardness values at the bottom, and the highest at the center. Resin cement hardness was influenced by the thickness of the indirect restoration and by the distance between the light-curing unit tip and the resin cement surface.
Highlights
The success of indirect esthetic restorations depends mainly on the luting agent, which should guarantee an effective bonding between the restoration and the dental substrate, preserving the marginal seal [1]
There was a significant decrease (p
Specimens with indirect light-activation showed lower hardness when compared to the direct light curing groups at the center and bottom of the resin cement layer, regardless of the resin disc thickness
Summary
The success of indirect esthetic restorations depends mainly on the luting agent, which should guarantee an effective bonding between the restoration and the dental substrate, preserving the marginal seal [1]. The choice of the luting agent must rely on the physical and biological properties as well as the handling characteristics of this material associated with the characteristics of the prosthetic restoration [2]. In an attempt to combine the desirable properties of self- and light-activated resin cements, dual-cured cement was developed to allow the clinician to control the polymerization time and for proper polymerization at deep areas where light is strongly attenuated due to the distance from the light-curing unit tip. In some clinical situations, some factors such as light intensity, exposure time, thickness, composition, shade and opacity of the indirect restorative material can affect the amount of energy reaching the cement [3]. Lower degree of conversion is expected from resin cements when the energy is lower than that required for a proper resin cement polymerization, leading to postoperative sensitivity, staining, marginal
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
