PubMed · 10610194
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J O'Keefe. 1999. Breaking down old barriers.. https://pubmed.ncbi.nlm.nih.gov/10610194/
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OBJECTIVES: This study was to investigate the effect of saliva used as storage liquid and the length of storage effect on surface hardnesses of Fuji IX (GP) (FIX), Dyract (DR), Z-100 and Estio LC (ELC). METHODS: The materials were mixed according to the manufacturers' instructions and immersed in distilled water or human parotid saliva. Vickers hardness number (HVN) was measured 1, 7, 20 and 40 days after the materials were mixed. HVN was calculated from the indentation diameter after 100 or 300g loading on their surface for 15s. The two methods of characterization used in this work were X-ray photoelectron spectroscopy (XPS) for surface chemical composition and electron probe microanalysis (EPMA) for depth profile analysis. RESULTS: Only in FIX, did HVN increase with time at both storage conditions, distilled water and saliva. The increase rate of the value was higher when stored in saliva than distilled water. After 40 days storage in saliva, the HVN value of FIX increased by 39%. The increase for storage in saliva for DR was 22%, ELC 16%, and Z100 3%, compared to 1 day storage in distilled water. Ca and P peaks caused by saliva were detected by XPS and EPMA analysis, but these peaks did not exist in either composite resin or polyacid-modified composite resin by EPMA analysis. SIGNIFICANCE: Saliva has the remarkable effect of increasing surface hardness of Fuji IX (GP).
This study measured the dimensional changes due to hygroscopic expansion that occur in five commercially available compomer restorative materials using a computer-controlled laser micrometer. The materials tested were; [C] = Compoglass-F (Vivadent); [D] = Dyract AP (Dentsply DeTrey); [E] = Elan (Kerr); [F] = F2000 (3M); [H] = Hytac (Espe). Twelve discs of each test material were prepared, 10 mm diameter x 1 mm thickness. All specimens were kept dry for 48 h during polymerisation. Two control specimens of each group were kept in a desiccating chamber; five specimens in deionized water at 37 degrees C and five specimens in artificial saliva (Salivace, Penn) at 37 degrees C. The diameter of each disc was measured automatically across 200 points by rotation through the laser beam. These measurements, together with weight measurements, were carried out at intervals over a 2 month period. At 2 months, the mean % changes in volume after water immersion were: [C] = 2.45% (SD = 0.10); [D] = 1.50% (SD = 0.12); [E] = 1.53% (SD = 0.09); [F] = 1.69% (SD = 0.12); [H] = 1.44% (SD = 0.18). Specimens immersed in artificial saliva showed expansion rates identical to those immersed in water with the exception of material [H] at 1.73% (SD = 0.02) (p = 0.01). All specimens immersed in saliva showed a greater weight gain than those in water. The time taken to reach 90% of the final expansion varied from 7 days [F] to 50 days [H].
The purpose of this study was to compare the fluoride release and direct tensile strength at 24 h, 1 month, and 3 months of two conventional glass-ionomers, two visible light-cured resin-modified glass-ionomers, a polyacid resin composite and two resin composites. The results were statistically analysed using ANOVA and Fisher's PLSD at alpha=0.05. The data on fluoride release indicated that the immersion period (24 h, 1 month, and 3 months) significantly influenced the cumulative amount of fluoride released (P < 0.001). The direct tensile strengths after 1 month of storage were significantly higher than those after 24 h or 3 months of storage (P < 0.001). Thus, the cements and resins were not weakened by the loss of fluoride. Conventional glass-ionomer cement showed the lowest direct tensile strength. Resin-modified glass-ionomer behaved in between the resin composites and conventional glass-ionomers in terms of all three testing times, however, the polyacid resin composites most closely resembled the resin composites. The polyacid resin composites had greatly enhanced direct tensile strength, however, this material also reduced the fluoride availability.