What question did this study set out to answer?

This study evaluates how different types of resin composites, increment thickness, and light intensity affect temperature rise during photopolymerization.

May 17, 2026Open Access

Thermal Behavior of Dental Composites During Photopolymerization: Effect of Material Type, Increment Thickness, and Light Intensity

Key Points

This study evaluates how different types of resin composites, increment thickness, and light intensity affect temperature rise during photopolymerization.
In vitro experimental study with a factorial design
Temperature measured at the center of increments using a type K thermocouple
Four-way ANOVA was used to analyze data, with α = 0.05
Temperature increase ranged from 3.24 °C to 18.18 °C across groups (p < 0.05)
Flowable composites led to the highest temperature rise (p < 0.001)
4.0 mm increments produced greater increases than 2.0 mm (p = 0.008)

Abstract

Heat generated during photopolymerization of resin-based composites from both the exothermic reaction of the material and the irradiance of light-curing units poses a risk to pulp vitality, especially in deep restorations. This study aimed to evaluate temperature variation (ΔT) during the photopolymerization of different resin composites, considering material type, shade, increment thickness, and light-curing unit output. An in vitro experimental study with a factorial design was conducted. Specimens were prepared using 2.0 mm and 4.0 mm increments from conventional (nanohybrid), bulk-fill, and flowable resin composites in different shades (BW, A1, A3, A4, and XB) and different light-curing unit output (100% and 50% battery charge). ΔT was measured using a type K thermocouple (Omega Engineering, Norwalk, CT, USA) positioned at the center of each increment. Data were analyzed using four-way analysis of variance (ANOVA) (α = 0.05). All groups demonstrated a statistically significant temperature increase (p < 0.05), with ΔT values ranging from 3.24 °C to 18.18 °C. Composite type significantly influenced ΔT (p < 0.001), with flowable composites showing the highest temperature rise, followed by bulk-fill and conventional composites. Increment thickness also had a significant effect (p = 0.008), with 4.0 mm increments producing greater temperature increases. Shade significantly affected ΔT (p < 0.001), with the XB shade exhibiting the highest values. Additionally, higher light-curing output (100%) resulted in significantly greater temperature increases compared to 50% output (p < 0.001). Photopolymerization temperature rise is influenced by multiple interacting factors. The combination of flowable composites, darker shades, thicker increments, and higher curing output may increase thermal risk. These findings should be considered when optimizing clinical protocols to minimize potential pulpal damage.

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