Adhesive Type, Application Mode and Composite Preheating Influence Temperature Changes Across Different Dentin Thicknesses.

Objectives: To evaluate the effect of universal adhesive type/mode and bulk-fill composite preheating on temperature changes (ΔTs) across two different dentin thicknesses.

Methods: Eighty dentin discs (2mm thickness) were randomly divided into 8 groups (n=10) based on adhesive type (All Bond Universal-ABU or Scotchbond Universal Plus- SBUP), adhesive mode (self-etching-SE, or etch-and-rinse-ER), and composite preheating (non-preheated, or preheated). K-type thermocouple wire was used to record ΔTs during adhesive light-curing (ΔT1), composite application (ΔT2), and composite lightcuring (ΔT3). After recording of ΔTs, 2mm dentin discs were reduced to 1mm thickness, and experiment was repeated. Statistical analysis was performed using ANOVA/Tukey tests (α = 0.05).

Results: Dentin thickness significantly affected ΔTs (P⟨.001), with 1mm thickness showing significant increase. Neither composite preheating, nor adhesive type/ mode significantly affected temperature changes (P⟩0.05). Both ABU/SE and SBUP/ER in preheated composite groups showed no significant difference (P⟩0.05) between 2mm (2.81±0.85°C and 1.51±0.89°C, respectively) and 1mm thicknesses (3.52±0.46°C and 2.38±0.94°C, respectively) in ΔT2. ΔT3 was significantly higher than ΔT1 and ΔT2 regardless of the dentin thickness (P⟨0.05).

Conclusion: Composite light-curing increased temperature beyond the limit that pulp can withstand, regardless of dentin thickness.

Clinical relevance: Preheated bulk-fill composite is safe for restoring deep cavities, but caution is needed during light curing.