Analysis of the Effect of Dental Chair Light on the Knoop Hardness of Composite Resin While Light Curing with QTH and LED Light Units

Dental chair lights have been known to rapidly polymerize lightcured composites beyond the point of workability. Often in our dental clinics we are advised to switch off the dental chair light while light curing of dental composites. The purpose of this study was to determine whether the dental chair light causes any effect on the degree of polymerization of light cured composites using the quartz tungsten halogen (QTH) and the light emitting diode (LED) light curing units (LCUs). Filtek Z350 composite samples of 2 × 5 mm were prepared in an acrylic mold. Four groups were made having 20 samples each. In group I and II light curing was done using QTH LCU with and without the dental chair light respectively. Similarly in group III and IV LED LCU was used. Microhardness was measured and compared using Knoop’s hardness Test. Data was submitted to ANOVA and Tukey’s test. Results showed that the average microhardness was significantly higher in group 4 (LED light curing with dental chair light on). Thus, it was concluded that the dental chair light can be left on while using QTH and LED LCU’s during light curing of composite material.