Ultrasonic Measurement of Polymerization Behavior of Dual-Cured Resin Cement

Objectives: The current study monitored the polymerization processes of resin cements using an ultrasonic device, and investigated the influence of the power density of the curing unit, and the application of the self-etching primer, on the polymerization behaviour of dual-cured resin cements.

Methods: The dual-cured resin cements used in this study were Bistite II (Tokuyama Dental), Linkmax (GC), Clearfil Esthetic Cement (Kuraray Medical),Panavia F 2.0 (Kuraray Medical) and ResiCem (Shofu). The propagation time of longitudinal ultrasonic waves was measured by a Pulser-Receiver (MODEL 5900, Panametrics). Resin cements were mixed and inserted into a transparent mould, and specimens were placed on the sample stage, onto which the primer, if used, was also applied. Power densities of 0 (no irradiation), 200 or 600 mW/cm² were used for curing. The transit time through the cement disk was divided by the specimen thickness to obtain the longitudinal sound velocity.Six specimens per group were used for each condition, and Tukey HSD tests were done at a level of 0.05.

Results: When resin cements were light-irradiated, each curve displayed an initial plateau of ~1,500 m/s, which rapidly increased to a second plateau of 2,300–2,900 m/s. The rate of sound velocity increase was retarded when the cements were light-irradiated at lower power densities, and increased when the primer was applied.

Conclusions: The polymerization behaviour of dual-cured resin cements was therefore shown to be affected by the power density of the curing unit and the application of self-etching primer.