Korean J Dent Mater.  2020 Sep;47(3):119-130. 10.14815/kjdm.2020.47.3.119.

Real time measurement of the transmittance change of composite during light curing

Affiliations
  • 1Department of Conservative Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
  • 2One-stop Specialty Center, Seoul National University Dental Hospital, Seoul, Korea
  • 3Department of Dental Biomaterials Science, School of Dentistry, Seoul National University, Seoul, Korea

Abstract

The purpose of this study was to measure the transmittance change of composites during light curing in real time according to different shades and thicknesses. An instrument using pulse width modulation-curing light was developed to measure the transmittance of composites in real time. A micro-hybrid composite, Filtek Z250, was used for %transmittance measurement with five different shades (A1, A2, A3, A3.5, A4) and 4 different thicknesses (0.16, 0.5, 1.0, 1.5 mm). The maximum value of d(%Transmittance)/dt and peak time were used to observe polymerization kinetics. Attenuation coefficient was also compared between pre and post cured specimens. The transmittance increased in all specimens after polymerization. A2 showed the highest and A1 showed the lowest transmittance in both pre and post curing. The transmittance change and maximum rate of change were highest in A2 and lowest in A3.5, and the peak time, which ranged in 3.10 to 4.07, was not significantly different among shades. As the specimen became thinner, both the transmittance and rate of change increased, and the peak time was maximum at 1.5 mm thickness. The absolute value of attenuation coefficient decreased after polymerization in all specimens. In conclusion, the transmittance of composite increased after polymerization. Each shade showed different transmittance value for both pre and post curing state, and thinner specimen showed higher transmittance value. Polymerization kinetics could also be observed through the rate of transmittance change over time.

Keyword

Attenuation coefficient; Composites; Light curing; Polymerization kinetics; Transmittance
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