Abstract
Objective. This study aimed to investigate the effects of (i) a high-irradiance (3s) light-curing protocol versus (ii) two standard-irradiance (10s) protocols on 2D temperature maps during intra-dental photo-irradiation within a molar cavity restored with either Ultra-Rapid Photo-Polymerized Bulk Fill (URPBF) composites or a pre-heated thermo-viscous bulk-fill composite, compared to a standard bulk-fill resin-based-composite (RBC). The specific objectives included visual assessment of the temperature maps and quantitative assessment of several temperature/time plots at four different locations.
Methods. A caries-free lower first molar cavity served as a natural tooth mold. Resin composites were placed without intermediary adhesive. Two URPBF composites (PFill; PFlow) and one pre-heated thermo-viscous bulk-fill composite (Viscalor: VC) were compared to a contemporary bulk-fill composite (One Bulk Fill:OBF). Two LED-LCU devices were used: Bluephase PowerCure (PC) and Elipar S10 (S10), with three light-irradiation protocols (PC-3s, PC-10s and S10-10s). 2D temperature maps over the entire coronal area were recorded for 120 s during and after irradiation using a thermal imaging camera. Changes at four different levels were selected from the data sets: (0, 2 and 4 mm from the cavity top and at 1 mm below the dentin cavity floor). The maximum temperature attained (T-max), the mean temperature rise (Delta T), the time (s) to reach maximum temperature and the integrated areas (degrees C s) under the temperature/time (T/t) plots were identified. Data were analysed via three-way ANOVA, One-way ANOVA, independent t-tests and Tukey post-hoc tests (p < 0.05).
Results. All RBCs showed qualitatively similar temperature-time profiles. PFlow reached T-max in the shortest time. PC-3s (3000 mW/cm(2)) generated comparable Delta T to S10-10s, except with PFill, where Delta T was greater. Despite the same irradiance (1200 mW/cm(2)), Elipar S10 led to higher T-max and Delta T compared to PC-10s. The highest T-max and Delta T were observed at the 2 mm level, and the lowest were at 1 mm depth into the underlying dentin.
Significance. Coronal 2D temperature maps showed rises largely confined within the bulkfill RBC materials, with maxima at 2 mm rather than 4 mm depth indicating some extent of thermal insulation for the underlying dentin and pulp. RBCs polymerized via different irradiation protocols showed similar temperature changes. With the PC-3s protocol - also with pre-heated VC - minimal temperature rises at 1 mm within dentin suggest their clinical safety when sufficient remaining dentin thickness is present. (C) 2021 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.