Initial curing characteristics of composite cements under ceramic restorations

Objectives: To assess the degree of conversion (DC) of dual-curing composite cements when cured through ceramic-veneered zirconia disks.
Methods: The cements investigated were G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake) and ResiCEM (Shofu). Portions of mixed cement were placed on the ATR crystal of a Fourier Transform Infrared Spectroscope (FTIR; iS50, Thermo Scientific) and squeezed to a ±100-µm film thickness using a microscopy cover glass with two other cover glasses positioned aside the composite portion and employed as spacer. DC (%) of the composite cements applied in self-curing mode was measured in the dark at 37°C. Following the dual-curing mode, the cements were light-cured directly (positive control) or through a ceramic-veneered highly translucent zirconia disk (0.5-mm thick zirconia [Katana HT; Kuraray Noritake] with a 1.0-mm thick veneering ceramic [Cerabien ZR, Kuraray Noritake]) for 40 sec using two light-curing units (G-Light Prima 2, GC; Pen-Cure, Morita). Per experimental group, 5 test were conducted (n=5). For both curing modes, FTIR spectra of the composite-cement films were acquired to determine DC every min up to 30 min after placement. DC of the composite cements measured at 30 min was statistically compared using 1-way and 3-way ANOVA (α=0.05), respectively.
Results: For the self-curing mode, DC at 30 min of Panavia V5 (54.4±0.8%) was significantly higher than that of G-CEM LinkForce (47.0±2.8%) and ResiCem (41.6±1.7%). For the dual-curing mode, Panavia V5 revealed a significantly higher DC at 30 min (56.0±0.6%) than the two other composite cements (G-CEM LinkForce: 48.9±1.1%; ResiCem: 48.3±1.9%). When the composite cements were light-cured through the zirconia disk, DC at 30 min dropped significantly for ResiCEM, while not for Panavia V5 and G-CEM LinkForce.
Conclusions: Panavia V5 resulted in the highest DC when applied following both the dual- and self-curing mode. Ceramic-veneered zirconia-based restorations may affect DC of some composite cements.