Polymerisation in Hybrid Ceramics:Effect of Thickness and Cement Type

Objectives: This study aimed to evaluate the degree of conversion (DC) of dual-cure resin cements, flowable composites, and bulk-fill composites used in the cementation of hybrid ceramic CAD-CAM blocks with varying thicknesses.
Methods: Hybrid ceramic CAD-CAM blocks(Cerasmart,GC) with thicknesses of 1,5 mm,2 mm, and 2,5 mm were fabricated. Three cements types-dual-cure resin cements (Estecem II Plus,Tokuyama),flowable composite (Estelite Universal Flow,Tokuyama), and bulk-fill composite (Estelite Bulk-fill Flow, Tokuyama) – were polymerised in a custom setup to prepera 64 cement samples (n=7 per group). Samples were stored in the dark at 37 °C for 24 hours, and their DC was measured using the Shapiro-Wilks test and analysed with two-way ANOVA and Bonferroni post hoc tests (p<0,05).
Results: Block thickness significantly influenced the DC of the cement (p<0,001). For 1,5 mm and 2 mm blocks, flowable composite cements showed higher DC compared to dual-cure and bulk-fill composites (p>0,05). For 2,5 mm blocks, dual-cure cement achieved the highest DC, and flowable composites showed the lowest.
Conclusions: The DC of cements varied depending on block thickness and material type. For blocks ≤2 mm thick, flowable and bulk-fill resin composites can be alternatives to dual-cure cement.Bulk-fill composites demostrated potential for use in 2,5 mm restorations due to their polymerisation capability in deeper regions.However, further studies are needed to explore material-specific differences.