Composite Photopolymerization: Temperature Increase According To Light Source and Dentin Thickness - Composite Photopolymerization: Temperature Increase According To Light Source and Dentin Thickness - Open Access Pub

When a composite resin restoration is photopolymerized, a considerable amount of heat can be produced, potentially causing pulpal injury. Objective: Evaluate the influence of the type of light source and remaining dentin thickness on the temperature increase in the pulp chamber while curing composite resin restorations. Material and Methods: Ninety-six tooth fragments obtained from bovine incisors were divided into groups/subgroups (n=12), according to the light source (LED and halogen light) and remaining dentin thickness (3.5, 3, 2, and 1mm). Class I cavities were prepared and restored with a composite resin. A temperature increase was obtained during photopolymerization of the adhesive and each composite increment. Data were analyzed using ANOVA and Fisher’s Test (α=5%). Results: LED promoted higher temperature increments when compared with the halogen light. Temperature levels were the lowest for 3.5mm-thick and the highest for 1mm-thick remaining dentin. Levels registered during the photopolymerization of each composite increment were superior for LED. Conclusions: Both light sources result in temperature increases above 5.5°C. Additionally, the remaining dentin thickness of 1mm promoted the largest temperature increase. DOI10.14302/issn.2473-1005.jdoi-16-1080 Since the introduction of dental composite resin in clinical practice1, improvements have been made to enhance the clinical performance of this restorative material. One example of development in this area is the use of visible light-cured composite resins2. Ultraviolet light was the first light source to be employed to initiate the polymerization reaction of dental composite resins; however, this light source had a direct negative influence on the mechanical properties of composite resins3,4. Quartz-tungsten-halogen (QTH) curing units have been widely used in the polymerization of composite resins with satisfactory results3,5. However, these curing units have some inherent limitations, such as generation of heat and degradation of the halogen bulb, reflector, and filter, all of which reduce the efficiency of the curing unit5, 6, 7. In the 1990s, new polymerization techniques and curing units were introduced in the field of restorative dentistry, such as the use of light emitting diode (LED) curing units8. These units do not require the presence of filters to emit a wavelength in the 400 to 500 nm range, which is required to excite the camphoroquinone photoinitiators9. Therefore, LED units do not emit wavelengths in the infrared spectrum, so their operation requires less energy10, generating