Significant shear bond strength improvements of a resin-modified glass ionomer cement with a resin coating.

Previous evidence has suggested that resin-modified glass ionomer cements (RMGICs) may be sensitive to temperature and moisture changes for the first 24 hours after photopolymerization. To test the hypothesis that a resin coating placed over the surface of an RMGIC restoration would decrease the susceptibility to moisture and temperature conditions, 44 RMGIC samples were prepared in inverted-cone recesses drilled in epoxy resin plates. After abrasion of all samples with 800-grit silicon carbide paper to simulate a diamond bur finish on the surface, a coat of highly filled resin was applied to the experimental group (n = 22) and cured according to the manufacturer's instructions. The plates were thermocycled 500 times between 5°C and 55°C and then maintained at 37°C with 95% humidity. The thermocycled samples were bonded to a second epoxy resin plate filled with RMGIC and subjected to shear bond strength testing. The resin-coated group had a significantly greater mean shear bond strength than the control group (P < 0.05). The resin coating also appeared to affect the mode of failure by significantly increasing the number of mixed failures (P < 0.05). The results suggest that a resin coating protects RMGIC from moisture- and temperature-induced damage and increases shear bond strength.

Eruption sequence of the permanent maxillary canine: a radiographic review.

This study evaluated the eruption sequence of the permanent maxillary canine in patients to determine if it follows the previously established normal pattern: first premolar, second premolar, and canine. A total of 363 panoramic radiographs of patients 7-12 years of age were evaluated; in 261 (72%) of the patients, the permanent canine erupted after the first and second premolars. Based on the results obtained in this study, the eruption sequence of the permanent maxillary canine followed the historical normal pattern for the majority of patients in this population. The difference in eruption sequence for males versus females was not significant.

Distance from source and fluoride concentrations in municipal water supply.

AIM: The purpose of this study was to evaluate the concentrations of fluoride in community water at the point of source, compared to the concentration delivered to various locations within the Las Vegas Valley, to determine if the levels of fluoride change over distance. METHODS: Ten samples per week over an 8-week period were taken from four locations, totaling 320 samples. The first location included the water treatment facility where fluoride is added to the municipal water to bring the concentrations to the desired amount. The other locations included three residences at an increasing distance from the source of fluoridation. The 320 samples were submitted for fluoride analysis. Repeated-measure anova was used to compare the means between the four data points. RESULTS: The fluoride concentration data for the four test locations ranged from 0.73 to 0.89 mg/L. Mauchly's test of sphericity revealed no significant difference in the fluoride concentrations in Las Vegas from the point of source to distant locations. CONCLUSIONS: The analysis of the collected data revealed that there was no statistical difference in the fluoride concentration in the Las Vegas municipal water supply from the source to the remote locations, and that distance does not affect fluoride concentration in the Las Vegas Valley municipal water supply.