Influence of Light Curing Unit and Ceramic Thickness on Temperature Rise during Resin Cement Photo-activation

Abstract

The aim of this study was to determine the effect of different ceramic thickness on heat generation during resin cement photo-activation by QTH (quartz-tungsten-halogen), LED (light emitting diode), and PAC (plasma arc-curing) LCUs (light curing units). The resin cement used was Rely X ARC (3M-ESPE), and the ceramic was IPS Empress Esthetic (Ivoclar-Vivadent), of which 0.7-, 1.4 -and 2.0-mm thick disks, 0.8 mm in diameter were made. Temperature increase was recorded with a type-K thermocouple connected to a digital thermometer (Iopetherm 46). An acrylic resin base was built to guide the thermocouple and support the 1.0-mm thick dentin disk. A 0.1-mm thick black adhesive paper matrix with a perforation 6 mm in diameter was placed on the dentin to contain the resin cement and support the ceramic disks of different thicknesses. Three LCUs were used: QTH, LED and PAC. Nine groups were formed (n‫)01ס‬ according to the interaction: 3 ceramic thicknesses, 1 resin cement and 3 photo-activation methods. Temperature increase data were submitted to Tukey's test (5%). For all ceramic thicknesses, a statistically significant difference in temperature increase was observed among the LCUs, with the highest mean value for the QTH LCU (pϽ0.05). For all the LCUs, a thickness of 0.7 mm produced the highest temperatures (1.4 and 2.0 mm, pϽ0.05). There was no difference in temperature values between the latter two thicknesses (pϾ0.05). The interaction of higher energy density with smaller ceramic thickness showed higher temperature increase values.

Comparison of Silorane and Methacrylate-Based Composites on the Polymerization Heat Generated with Different Light-Curing Units and Dentin Thicknesses

“…As the light energy input during irradiation of both LCUs was the same for the two composite resins, the substantially different pattern of heat generation observed for Filtek P90 may be related to a different polymerization reaction (Table 4). The temperature increase caused by the composite photoactivation resulted from energy density produced by LCUs (22). The conventional LCU with halogen light (XL 2500) used in this study emitted a 31.2 J/cm 2 energy density , considering that the irradiance was 780 mW/cm 2 during 40 s (energy density (J/cm 2 ) = irradiance (mW/cm 2 ) x exposure time (s)/1000) for continuous light modulation.…”

Effects of different ceramic and dentin thicknesses on the temperature rise during photocuring

“…Previous studies showed that an extensive temperature increase during photocuring would decrease the number of surviving cells and injure pulp tissues. 8,20,27,33,34 This experiment simulated the environment in the pulp chamber, and the starting temperature was set to 37 C in order to observe the mean maximum Table 1 Mean temperature, changes in temperature from the baseline (Dt, C ), and the standard deviations of nine different combinations of dentin and ceramic thicknesses. temperature change in each group and establish a threshold of 5.5 C, (a pulpal temperature of 42.5 C) as a clinical consideration during cementation of ceramic restorations.…”

Efficiency of Dual-Cured Resin Cement Polymerization Induced by High-Intensity LED Curing Units Through Ceramic Material

“…14 Even after the filtration, however, halogen lights deliver several unwanted wavelengths of light that are highly absorbed by dental materials, resulting in the heating of the tooth and resin during the curing process. 15 Other drawbacks include a decline in irradiance over time, a limited curing depth, and a need for a longer exposure period. 13 Recently developed light-emitting diode (LED) lights offer a much narrower emission spectrum (a bandwidth of about 20 nm centered on 470 nm), 16 and the spectrum falls closely within the absorption range of camphorquinone, the most frequently used photoinitiator in resin composites.…”