Category: Laboratory Research
Effect of Composite Shade on Temperature Change During Photopolymerization
Chang-Ha Leea* (lch1104@snu.ac.kr) | In-Bog Leea
aSeoul National University, Seoul, Korea
Objective: The aim of this study was to investigate the temperature change during composite photopolymerization according to the composite shades.
Methods: Each 0.37 g of conventional nanocomposite (Filtek Z350XT Universal Restorative in A2 enamel (Z3E), A2 body (Z3B) or A2 dentin (Z3D) shades, 3M, St. Paul, MN, USA) was pressed between two glass slides with a 1-mm-thick spacer. A disc-shaped specimen was prepared and photopolymerized for 20 s with a radiant emittance of 2,100 mW/cm2. The temperature change was measured using a non-contact infrared thermometer for 300 s (n=3). A second light exposure, using the same protocol as the first, was performed on each photopolymerized specimen. The first peak in temperature (ΔTtotal), and the second peak in temperature caused by a light curing unit (ΔTlight) were obtained from the temperature change vs. time curve. The net peak in temperature caused by the curing heat of the composite (ΔTcomposite) was acquired by subtracting the second curve from the first one. The peak time was defined as the time when the ΔTcomposite occurred. The CIE L*, a*, and b* of each specimen were measured using a spectrophotometer without background, and then, with a white or black background, to calculate the translucency parameter (TP).
Results: The ΔTtotal and ΔTlight of Z3D (31.93℃ and 22.07℃) was the highest followed by Z3B (27.74℃ and 17.19℃), while Z3E (23.94℃ and 14.15℃) showed the lowest ΔTtotal and ΔTlight (p<0.05). The peak time of Z3D (4.07 s) was longer than that of Z3B (3.28 s) (p<0.05). The ΔTtotal and ΔTlight increased as L* increased, b* increased, and TP decreased. The ΔTcomposite did not correlate with L*, a*, b*, or TP.
Conclusion: Significant differences in temperature change were observed during the photopolymerization of composites of different shades. The more opaque the composite was, the greater the increase in ΔTtotal and ΔTlight.
Funding/Conflict of Interest: None
Keywords: composite, photopolymerization, shade, temperature change
