Could Tack-Curing Influence Margin Continuity and Conversion Degree of a Universal Dual-Curing Cement?

Proper polymerization protocol is crucial for the long-term success of full-ceramic crown restorations. This study investigates the margin continuity and degree of conversion (DC) of a universal dual-curing cement under full-ceramic crowns subjected to different polymerization protocols and thermal aging. Intact human upper central incisors and canines were prepared for crowns, digitally designed, and milled from reinforced lithium silicate (Celtra Duo, Dentsply). Crowns were cemented using a universal dual-curing cement (G-Cem One, GC) with two polymerization protocols: (G1) microbrush excess removal, 1 min waiting, and 20 s light curing per side; (G2) 5 s tack curing per side, excess removal with a scaler, and 20 s light curing. Marginal adaptation was assessed using micro-computed tomography, and DC was evaluated with Raman spectroscopy before and after artificial thermal aging (10,000 cycles between 5 °C and 55 °C). Statistical comparisons were performed with significance set at < 0.05. Results showed significantly poorer marginal adaptation in the tack-curing group, with no post-aging differences between groups. Baseline DC was high in all samples, with no protocol-dependent variations; nevertheless, aging increased DC in G1. These findings highlight the importance of selecting an appropriate polymerization protocol to ensure optimal marginal adaptation and polymerization efficiency.