In-vitro pulp chamber temperature rise during composite resin polymerization with various light-curing sources.

OBJECTIVES

The purpose of this in vitro study was to measure the pulp chamber temperature increase induced during composite resin polymerization with various visible light-curing units.

METHODS

A Class II cavity was prepared in an extracted molar tooth, leaving a dentin layer 1 mm thick between pulp chamber and proximal cavity wall. A 2 mm composite resin layer was applied to the proximal box and light-cured with the selected curing units: Heliolux II (H; 320 mW/cm2), QHL 75 (Q; 505 mW/cm2), Astralis 5 (A; 515 mW/cm2), Optilux 500 (O; 670 mW/cm2), Elipar Highlight (EH; 730 mW/cm2), ADT 1000 PAC (P; 1196 mW/cm2). Light-curing took place for 40 s (H, A, Q, O, EH), 5 and 10 s (P). Measurement of pulp chamber temperature changes (starting temperature: 37.0 +/- 0.1 degrees C) during polymerization was performed with a K-type thermocouple positioned at the pulp-dentin junction. Mean values were calculated from 10 measurements with each light-curing unit. ANOVA and Dunnett t-test were used for statistical analyses.

RESULTS

Maximum temperature changes varied significantly depending on the light-curing unit used: 2.9 +/- 0.3 degrees C (H), 4.7 +/- 0.5 degrees C (A), 5.4 +/- 0.3 degrees C (P, 5 s), 5.6 +/- 0.4 degrees C (Q), 6.1 +/- 0.2 degrees C (EH, 2-step mode: 100 mW/cm2 over 10 s, 730 mW/cm2 over 30 s), 6.9 +/- 0.4 degrees C (EH), 7.3 +/- 0.3 degrees C (O), 7.8 +/- 0.9 degrees C (P, 10 s).

SIGNIFICANCE

It is concluded that light-polymerization with curing units characterized by high energy output (A,EH,O,P,Q) causes significantly higher pulp chamber temperature changes as compared to the conventional curing light (H). Therefore, clinicians should be aware of the potential thermal hazard to the pulp which might result from visible-light curing of composite resins.