Halogen lamp and led activation of resin-modified glass ionomer restorative material. In vitro microhardness after long term storage

AIM: The purpose of this study was to evaluate the activation of resin-modified glass ionomer restorative material (RMGI, Vitremer-3M-ESPE, A3) by halogen lamp (QTH) or light-emitting diode (LED) by Knoop microhardness (KHN) in two storage conditions: 24hrs and 6 months and in two depths (0 and 2 mm). MATERIALS AND METHODS: The specimens were randomly divided into 3 experimental groups (n=10) according to activation form and evaluated in depth after 24h and after 6 months of storage. Activation was performed with QTH for 40s (700 mW/cm2) and for 40 or 20 s with LED (1,200 mW/scm2). After 24 hrs and 6 months of storage at 37°C in relative humidity in lightproof container, the Knoop microhardness test was performed. Statistics Data were analysed by three-way ANOVA and Tukey post-tests (p<0.05). RESULTS: All evaluated factors showed significant differences (p<0.05). After 24 hrs there were no differences within the experimental groups. KHN at 0 mm was significantly higher than 2 mm. After 6 months, there was an increase of microhardness values for all groups, being the ones activated by LED higher than the ones activated by QTH. CONCLUSION: Light-activation with LED positively influenced the KHN for RMGI evaluated after 6 months.

The bonding of glass ionomer cements to caries-affected primary tooth dentin

PURPOSE The purpose of this study was to evaluate the bonding of glass ionomer cements (GICs) to sound and caries-affected dentin by microtensile bond strength (μTBS) and nanoleakage (NL) tests. METHODS Occlusal cavity preparations were made in 36 sound primary molars. Half of the specimens were submitted to a pH-cycling model to create simulated caries-affected dentin. Teeth were randomly restored with one of the three materials: (1) resin-modified GIC with nanoparticles (Ketac N100; KN); (2) resin-modified GIC (Vitremer; VI); and (3) high-viscosity GIC (Ketac Molar Easy Mix; KM). Specimens were tested using a microtensile test (1 mm/minute). One specimen from each tooth was immersed in ammoniacal silver nitrate for 24 hours and revealed after eight hours to assess interfacial NL. The μTBS means were analyzed by 2-way analysis of variance and Tukey's post hoc test. For NL, Kruskal-Wallis and Mann-Whitney tests were used (P<.05). RESULTS No difference was found between sound and caries-affected dentin (P>.05). KM showed the lowest GIC-dentin μTBS values, while VI and KN showed higher values. Infiltration of ammoniacal silver nitrate into the adhesive interface was not affected by sound or caries-affected dentin. CONCLUSION Caries-affected dentin does not jeopardize the bonding of glass ionomer cements to primary tooth dentin.