Abstract
Objectives: During the light-curing process of composite restoration, excessive heat can be produced, which can potentially lead to pulp necrosis (death). In this study, we aimed, based on the Finite Element Method (FEM), to assess the risk of pulp damage during the light-curing process by investigating the influence of light-curing devices, under various irradiation regimes, on the temperature increase at the pulp-dentin junction, during a one-layer or multi-layered deep composite restoration. Methods: A Three-dimensional finite element method model of typical geometry and material properties, as commonly reported in the literature, was employed in COMSOL Multiphysics simulations in order to determine the temperature increase in the pulp. Various combinations of light intensities, durations, and irradiation regimes were investigated for the two cases, of shallow and deep multi-layered composite restoration. Results: Results of light-curing composite resins within enamel; indicate that the temperature rise during the curing process was within the safety margins. Results of light-curing composite resin restorations closer to the pulp with thin remaining dentin, indicate a temperature increase that could be sufficient to cause thermal injury in the pulp. Modulating the light output marginally, reduced the temperature rise while reducing the intensity and increasing the curing duration which was consistently more effective in this respect. Conclusion: The results clearly demonstrate that with currently adopted standard procedures, there exists a risk of thermal injury during multi-layered composite restorations with thin remaining dentin; it is thus important to establish appropriate curing regimes that would lead to minimal temperature increase during deep composite restorations and hence reduce the risk of thermal injury to the pulp.
Highlights
Light-cured composite resins have been widely used and have been the standard of dental composites since the beginning of the 21st century [1]
488 The Open Dentistry Journal, 2021, Volume 15 thermal stimulus was administrated using a different variation of intensity and duration than the previous study, a temperature increase of approximately 11.2°C did not cause any irreversible damage to the pulp tissue
We investigate the effects that light-curing units (LCUs) of various light outputs have on the temperature increase at the Pulp-Dentine Junction (PDJ) during a one-layer of composite resin restoration, representing shallow cavity, and multilayered composite curing, representing deep restoration closer to the pulp with thin remaining dentin, using a Finite Element Method (FEM) model to simulate the temperature rise, in order to assess the risk of pulp thermal injury during the light-curing process
Summary
Light-cured composite resins have been widely used and have been the standard of dental composites since the beginning of the 21st century [1]. It was found that a temperature increase of 5.5°C in the pulp caused approximately 15% of the cases, irreversible damage to the pulp tissue, while a rise of 11.1°C caused about 60% of the cases, irreparable damage to the pulp tissue. 488 The Open Dentistry Journal, 2021, Volume 15 thermal stimulus was administrated using a different variation of intensity and duration than the previous study, a temperature increase of approximately 11.2°C did not cause any irreversible damage to the pulp tissue. An essential factor for the temperature threshold beyond which pulp tissue is injured, was not taken into consideration in the previous two studies is the residual dentin thickness: this can be small at the spot where the light-curing process is being carried out, not offering sufficient shielding to the pulp tissue [5]. Thermal damage is not limited to the pulp tissue alone; a high-temperature increase on the outer root surface can result in damage to the alveolar bone, the root cementum, and the periodontal ligament [6, 7]
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