Authors: M Khoroushi *• TM Karvandi 1• R Sadeghi 2 *Maryam Khoroushi, DDS, MS, associate professor, Department of Operative Dentistry and Torabinejad Dental Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran 1- Tayebeh Mansoori Karvandi, DDS, MS, Department of Operative Dentistry and Torabinejad Dental Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran 2-Reza Sadeghi, DDS, graduate, Isfahan University of Medical Sciences, Isfahan, Iran & Oral Health Center No. 2, Isfahan, Iran khoroushi@dnt.mui.ac.ir
Abstract:
Bond strength might improve by delaying the light activation procedure when a cavity conditioner is used for bonding RMGI to enamel. Conversely, delaying the light activation and/or prewarming of RMGI compromises bond strength to dentin and should be avoided. Introduction: Recent research shows that the acid-base reaction and light-activated polymerization in resin-modified glass ionomers (RMGI) compete with and inhibit one another. In addition, extrinsic energy would improve some properties of RMGI. This in vitro study evaluated the effect of prewarming and/or delayed light activation on bond strength of RMGI to tooth structure. Materials and Methods: Ninety-six flat enamel and dentin surfaces of human molars were ground with sequentially finer abrasives to 600-grit silicon carbide paper. Each surface was treated with a cavity conditioner for 10 seconds, rinsed, and gently air-dried (n=12). RMGI was applied to tooth substrates according to the following protocols: group 1) according to manufacturer's instructions; group 2) a delay of two minutes in light activation; group 3) prewarming of the encapsulated material (90 seconds, 40°C); group 4) prewarming plus a delay of two minutes in light activation. After 24 hours of storage at 37°C and 500 rounds of thermocycling, the samples were tested for shear bond strength and analyzed using two-way analysis of variance and Tukey HSD test (α=0.05). Results: Significant differences were observed between study groups (p<0.05). The highest enamel bond strength was recorded in group 2. Regarding dentin groups, the highest bond strength was recorded in group 1. Conclusion: Within the limitations of the present study, delaying light activation might improve bond strength of RMGI to enamel; however, the standard procedure recommended by the manufacturer is the best procedure for bonding of RMGI to dentin. More investigations are necessary.
Source: Operative Dentistry Full text | 
