Clinical Relevance

 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.

SUMMARY

 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

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