Effect of output intensity of light curing unit on coronal tooth discoloration induced by silicate calcium-based materials: an ex vivo study

Objective: Clinicians have various curing options due to new light-cure devices with different intensities. The present study aimed to evaluate the effect of two light-curing intensities (1,200 mW/cm² vs. 3,000 mW/cm²) on coronal discoloration induced by two calcium silicate-based cements (OrthoMTA and RetroMTA) in an endodontically treated bovine tooth model. Materials and Methods: Forty single-rooted bovine incisors were prepared, and their canals were filled with blood-soaked foam to the cemento-enamel junction. The samples were randomly divided into four groups (n = 10 per group) based on the cement used (OrthoMTA or RetroMTA) and the subsequent light-curing intensity. For all groups, a 2-mm layer of the assigned cement was placed. This was covered by 1 mm of resin-modified glass ionomer (RMGI), a bonding agent, and 2 mm of composite. In two groups, all light-curing steps (RMGI, bonding agent, composite) were performed at 1,200 mW/cm². In the other two groups, curing was performed at 3,000 mW/cm². All samples underwent 5,000 cycles of thermocycling. Color was assessed with a spectrophotometer immediately after composite placement and after aging. Color change (ΔE) and lightness change (ΔL) were calculated. Results: All groups exhibited ΔE values exceeding the clinically acceptable threshold (ΔE > 3.3) and demonstrated a decrease in ΔL after aging. Statistical analysis (two-way ANOVA, α = 0.05) revealed no significant difference in ΔE or ΔL between samples cured with high-intensity (3,000 mW/cm²) or low-intensity (1,200 mW/cm²) light, regardless of the cement type used (p > 0.05). Conclusions: Within the limitations of this study, the same amount of energy produced by high- or low-intensity light-cures (1,200 or 3,000 mW/cm²), when delivering the same total energy, did not result in a statistically significant difference in coronal discoloration caused by OrthoMTA or RetroMTA.