Evaluation of cohesive strenght between resin composite and characterizing materials

Objective: The objective of this study was to evaluate the cohesive strength between composite and different light curing characterizing materials (LCCM) used in the intrinsic technique. Method: The composite specimens were made by using a prefabricated Teflon device. A layer of LCCMs were used at the interface, totaling 75 specimens divided into 5 groups (n=15): Group 1- no LCCM was used in the Control Group; Group 2 - application of Kolor Plus Pigment White (Kerr) LCCM; Group 3 - Tetric Color Pigment White (Ivoclar/Vivadent) LCCM; Group 4 - Kolor Plus Pigment Brown (Kerr) LCCM; Group 5 - Tetric Color Pigment Black (Ivoclar/Vivadent) LCCM. All materials were used in accordance with the manufacturer's instructions. Specimens were submitted to a tensile test to evaluate the cohesive strength at the composite interface in universal testing machine EMIC DL-200MF. Data were subjected to One-way ANOVA and Tukey's test (á = 5%). Results: ANOVA showed a p-value = 0.0000, indicating that there were significant differences between groups. The mean values in MPa (± standard-deviation) obtained for the groups: G5: 9.1(±4.21)a, G4: 10.4(±4.01)a, G3: 19.1(±5.15)b, G2: 24.5(±3.29)c, G1: 27.9(±2.89)c. The groups accompanied by the same letters presented no statistically significant differences. The groups in which Kolor Plus Pigment Brown and Tetric Color Black LCCM were used had statistically lower levels of cohesive strength values in comparison with the other groups. The Control group and Kolor Plus Pigment white LCCM had statistically higher levels of cohesive strength values when compared with the other groups. Conclusion: The use of LCCM by the intrinsic technique reduced the cohesive strength of restorative composite. Keywords: Composite; Cohesive strength; Light curing characterizing materials.