Influence Of Dental Composite Shade On Surface Hardness

"Objectives: " The aim of this study was to evaluate the relation between composite shade, curing time and surface hardness. "Methods: " Dental Composite used in this study was Amelogen (Ultradent Inc.) with its 5 different shades A1, A2, A3, A3.5 and A4. Total seventy-five (n=75) samples were made with fifteen samples for each shade group (n=15/group). Specimens of 10 mm diameter with 2 mm height were prepared from all 5 shades of composite material at the room temperature.  All specimens were cured with the halogen light curing unit Coltolux 4 model (Coltene/Whaledent Inc., Mahwah, New Jersey, USA) and curing time of 40 second was standardized for all specimens.Barcol Hardness Impressor GYZJ 934-1 was used to measure top and bottom hardness of all 75 specimens of resin composite. Results were statistically analyzed by mixed model ANOVA. "Results:" Result showed that top hardness for all shades were in the range from 75.26 to 75.86.  Statistically significant difference at p < 0.05 was found in bottom hardness of each shade material. Bottom hardness was significantly decreasing from lighter to darker shade of composite. Bottom hardness for different shades of composite material sample in decreasing order were A1 - 61.13, A2 - 56.73, A3 - 35.06, A3.5 - 29.8, and A4- 21.13 "Conclusion: "Study showed that shade of dental composite influence the depth of cure and composite hardness. Darker shades may require more curing time or smaller increments than the lighter shades of composite. Thickness and curing time are critical for complete cure of different shades of composite material.