Bi-axial flexural strength of dual-polymerizing agents cemented to human dentin after photo-activation with different light-curing systems

ABSTRACT

This study aimed to assess the bi-axial flexural strength of two dual-polymerizing resin luting agents cemented to human dentin when photo-activated with different light-curing units. Two dual-cured resin cements choice [CH] and Variolink II [VL] were tested. Hybrid composite resin [Z-250] discs [12 +/- 1.5 mm] were fabricated. Three types of light-curing units were used halogen-curing unit [QTH], light-emitting diode [LED] and plasma arc [PAC]. Sixty dentin discs of 0.5 mm thickness were prepared from extracted human teeth. A circular mold [2.5 mm in height and 12 mm diameter] was utilized to create supporting structure for dentin, resin cement complex. The resin luting cement [0.5 mm] was placed on the previously prepared dentin discs and covered with the prefabricated composite discs. Photo-activation of cements was performed for 40 s with QTH and LED units and for 3 s with PAC. The specimens were divided into 12 groups [20 specimens for each light source]. Six groups were kept in distilled water for 24 h and the rest were stored for 6 weeks. Bi-axial flexural strength was determined using Instron machine. The data was analyzed using two-way ANOVA and Tukey test for comparison. The findings indicated that the bi-axial flexural strength values for both cements CH and VL were higher for 24 h over 6 weeks but not statistically significant when cured with QTH. Meanwhile, when LED light was used for photo-activation the cements, the flexural strength values reported were statistically higher of 24 h over 6 weeks storage at P=0.4E However, PAC light did not record any statistically significant difference between two duration for the CH cement although when used for polymerization of VL the reported value for 6 weeks were statistically significantly higher value than 24 h duration at P=0.002. When high immediate flexural strength is preferred in clinical situation photo-activation the cements with LED reported the greatest value