Influence of Light Irradiation and Temperature on the Polymerization Behavior of Self-adhesive Resin Cements

Abstract

Purpose: Self-adhesive resin cements (SARCs), in which polymerization can be initiated by both chemical and light activation, are used in some clinical applications. SARCs have been marketed to simplify clinical procedures and overcome the technique sensitivity of multiple-step systems. However, their setting behavior in different conditions is not known in terms of light irradiation and temperature of the cement. The purpose of this study was to monitor the influence of light irradiation and temperature on polymerization behavior of SARCs by use of ultrasound measurement. Methods: Three SARCs, Clearfil SA Cement Automix (Kuraray Noritake Dental), RelyX Unicem 2 Automix (3M ESPE) and BeautiCem SA (Shofu) were used. Ultrasound measurements were carried out using a pulser-receiver, transducers and an oscilloscope. The SARCs were mixed, inserted into a transparent mold, and then placed onto a sample stage. Power densities of 0 (no light irradiation), and 600mW/cm² were used for light irradiation, and temperatures were set at 23℃ and 37℃. The transit time through the SARCs was divided by the specimen thickness to obtain the longitudinal ultrasound velocity (V). The mean and standard deviation for the SARCs were subjected to a one-way analysis of variance (ANOVA) and Tukey's Honestly Significant Difference (HSD) test at a significance level of 0.05. Results: The increase rate of V was slower when the SARCs were not light-irradiated, and became faster when irradiated. The increase rate of V had a tendency to retard when the SARCs were stored at lower temperature. Conclusions: From the results of this study, it was indicated that the polymerization behaviour of the SARCs was affected by the light irradiation and temperature of the specimen. Light irradiation with a sufficient power density is necessary to achieve optimal setting reaction, even in materials with a dual-cured setting reaction.