Abstract
The aim of this research was to compare the pulp temperature (PT) rise induced by four light-emitting diode light-curing units (LED LCUs) (Bluephase 20i, Demi Ultra, SPEC 3, and Valo) in different curing modes. Immediately after extraction, the pulp chamber of 11 premolars was accessed from the palatal cervical third of the crown for insertion of fiber Bragg grating (FBG) sensors for temperature measurement and kept in a 37.0° water bath. The teeth were then submitted to a random sequence of curing modes with four irradiations at 30 s intervals. Care was taken to ensure complete pulp temperature reset between curing modes. The curing modes were classified as high-energy (above 80 J/cm2) or low-energy (below 40 J/cm2) according to the total energy density delivered. Statistical analysis was performed with repeated ANOVA measures and Pearson’s correlation for the association between energy density and temperature variation. The significance level was set to 0.05. All curing units promoted a statistically significant PT rise (p < 0.01). After four emissions, the PT rise was higher than 5.0 °C for the high-energy curing modes. The low-energy modes induced approximately a 2.5 °C rise. A strong positive correlation was found between energy density and PT increase (R = 0.715; p = 0.01). Exposure of intact premolars to LED LCUs induced significant and cumulative PT rise. Curing modes emitting high energy densities produced higher PT variations. Radiant exposure was positively correlated to PT variation.
Highlights
A large number of current daily clinical procedures can cause pulp temperature (PT)rise, with subsequent development of symptoms like hyperalgesia, dentinal hypersensitivity, and spontaneous pain typical of acute pulpitis due to pulp heating and trauma [1,2]
Tooth exposure to light-curing units (LCUs) is one of the routine conditions in restorative dentistry most highly associated with PT increase, which can widely vary from 1.5 ◦ C to 23.2 ◦ C, probably depending on the differential experimental settings in different studies [7,10]
This is corroborated by other studies that indicate that the heat generated from the LCU has much more impact than the heat from the exothermic reaction of the composite resin itself
Summary
A large number of current daily clinical procedures can cause pulp temperature (PT)rise, with subsequent development of symptoms like hyperalgesia, dentinal hypersensitivity, and spontaneous pain typical of acute pulpitis due to pulp heating and trauma [1,2]. In addition to the heat produced by the LCU, the polymerization of the composite induces an exothermic reaction that has been discussed as a cause of tissue damage. The possibility of pulpal damage caused by temperature rise should be considered when using light-cured bulk-fill materials in very deep cavities. In this clinical situation, it is suggested to avoid placing a large amount of composite as a first layer [11,12,13]. Notwithstanding, composite resin increments added to a restoration act as insulators rather than heat generators from an exothermic reaction. The energy density delivered by the LCU plays the most important role in intra-pulpal temperature rise [5,14,15,16]
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