ABSTRACT
The aim of this study was to measure the degree of conversion [DC] of three types of composite resins [micro-hybrid, nano-hybrid and Ormocer] with different light curing units [LED LCU and QTH LCU] in two depths. Three commercially available dental resin composites were used in this study: [Tetric Ceram, Ivoclar Vivadent, Liechtenstein-A2 shade], [Tetric Evoceram, Ivoclar Vivadent, Liechtenstein-A2 shade], [Ceram X, Dentsply, Germany-M[2] shade]. Specimens were divided into two groups, 5 specimens were photo-activated by QTH unit [Coltolux 75-Colten] and the other five specimens were cured by LED [Demi-Kerr]. Then each specimen was sectioned at the top surface and at 2-mm depth. The DC was measured by FT-IR [Bruker-tensor 27]. The data were analyzed by 3-way ANOVA test. There was significant difference between tested composite resins [P<0.001]. The results of top surfaces were significantly different from those observed at 2-mm depth [P<0.001]. The type of curing unit affected the polymerization of Ceram X resin composite. This study showed a significant difference in the degree of conversion in different thicknesses within three groups of resin composites
Subject(s)
Organically Modified Ceramics , Curing Lights, Dental , Light-Curing of Dental AdhesivesABSTRACT
PURPOSE: Heat of composite polymerization (HP) indicates setting efficacy and temperature increase of composite in clinical procedures. The purpose of this in vitro experimental study was to evaluate the effects of 5 temperatures on HP of two new composites. MATERIALS AND METHODS: From each material (Core Max II [CM] and King Dental [KD]), 5 groups of 5 specimens each were prepared and their total HPs (J/gr) were measured and recorded, at one of the constant temperatures 0degrees C, 15degrees C, 23degrees C, 37degrees C and 60degrees C (2 x 5 x 5 specimens) using a differential scanning calorimetry (DSC) analyzer. The data were analyzed using a two-way ANOVA, a Tukey's test, an independent-samples t-test, and a linear regression analysis (alpha=0.05). RESULTS: No polymerization reactions occurred at 0degrees C; then this temperature was excluded from statistical analyses. The mean HP of the remaining 20 KD specimens was 20.5 +/- 14.9 J/gr, while it was 40.7 +/- 12.9 J/gr for CM. The independent-samples t-test showed that there were significant differences between the HP of the two materials at the temperatures 15degrees C (P=.0001), 23degrees C (P=.0163), 37degrees C (P=.0039), and 60degrees C (P=.0106). Linear regression analysis showed statistically significant correlations between environment temperatures and HP of CM (R2=0.777). CONCLUSION: Using CM is advantageous over conventional composite because of its better polymerization capacity. However due to its high HP, further studies should assess its temperature increase in vivo. Preheating KD is recommended. Refrigerating composites can negatively affect their polymerization potential.