Strontium-releasing fluorapatite glass-ceramics: Crystallization behavior, microstructure, and solubility.

The purpose of this work was to investigate the effect of strontium partial replacement for calcium on the crystallization behavior, microstructure and solubility of fluorapatite glass-ceramics. Four glass compositions were prepared with increasing amounts of strontium partially replacing calcium. The crystallization behavior was analyzed by differential scanning calorimetry and X-ray diffraction (XRD). The microstructure was investigated by scanning electron microscopy. The chemical solubility was quantified according to ISO standard 10993-14. The amount of strontium released in solution after incubation in TRIS-HCl or citric acid buffer was measured by atomic absorption spectroscopy. XRD analyses revealed that partially substituted strontium-fluorapatite and strontium-åkermanite crystallized after strontium additions. The lattice cell volume of both phases increased linearly with the amount of strontium in the composition. Strontium additions led to a reduction in crystal size and an increase in crystal number density. The chemical solubility and amount of strontium released in solution increased linearly with the amount of strontium present in the composition in both TRIS-HCl and citric acid buffers. Total amounts of strontium released reached a maximum of 547 ± 80 ppm in TRIS-HCl and 1252 ± 290 ppm in citric acid buffer for the glass composition with the highest amount of strontium. For all strontium-containing compositions, the amount released in TRIS-HCl continued to increase between 70 and 120 h, indicating sustained release rather than burst release. © 2017 Wiley Periodicals, Inc. J Biomater Res Part B: 106B: 1421-1430, 2018.

NaF rinse and dentifrice concentrations on enamel lesion demineralization.

PURPOSE: To compare the in vitro effectiveness of two mouthrinses containing different concentrations of NaF to reduce enamel lesion demineralization. METHODS: Nine extracted caries-free molars were selected and cleaned. The teeth were painted with acid resistant varnish, leaving a 1 mm × 4 mm window exposed. The teeth were cycled in a demineralizing solution at pH 4.5 for a total for 96 hours. The teeth were sectioned longitudinally through the unpainted window using a hard-tissue microtome, producing 96 sections. The sections were measured and photographed under polarized light microscopy using water and Thoulet's 1.47 as imbibing mediums. Six treatment groups were randomly created: (A) water control group, (B) 0.05% rinse group once a day (C) 0.02% rinse group twice a day, (D) 1,500 ppm paste group used twice a day, (E) combination group containing 0.05% rinse once a day, and 1,500 ppm paste twice a day, and (F) combination group containing 0.02% rinse and 1,500 ppm paste twice a day. A 10-day cycling protocol was carried out. All sections were then re-measured and re-photographed. A statistical analysis was performed to detect any differences between pre- and post-treatment groups. RESULTS: There was a statistically significant difference in lesion depth between the water control group and the 1,500 ppm paste group as well as the 0.05% rinse in combination with 1,500 ppm paste group (P= 0.0184). No statistically significant differences were found between the control group and any other groups. A statistically significant difference was found in lesion area between the two rinse groups alone and the 1,500 ppm paste group, as well as the 0.05% rinse in combination with the 1,500 ppm paste group (P= 0.0002). An analysis of the results suggested that both rinse concentrations performed equally well in reducing lesion demineralization when used alone. However, only the 0.05% rinse used in combination with 1,500 ppm paste decreased lesion demineralization as compared to the water control group, and was equally as effective as the 1,500 ppm paste alone. CLINICAL SIGNIFICANCE: Within the limitations of this in vitro study, it was found that a fluoride containing dentifrice (1,500 ppm) and a combination of a fluoride containing dentifrice (1,500 ppm) and a 0.05% (210 ppm) fluoride rinse were more effective at reducing demineralization of enamel lesions than sodium fluoride rinses at concentrations of 0.02% and 0.05% alone or the combination of 0.02% NaF rinse with fluoride toothpaste.

Erosive potentials of brewed teas.

PURPOSE: To measure the pH, titratable acidity, fluoride concentration and erosive potential of brewed teas. METHODS: Bag teas were purchased to represent black, green, citrus, fruity, and floral tea flavors from Tulsi, Bigelow, HyVee, Tazo, and Yogi brands and brewed (1 bag/240 ml) in boiling water for 3 minutes. The pH, titratable acidity, and fluoride concentrations were measured. Following these measurements, a representative tea from each flavor was selected for investigation of erosion potential. Six extracted human molars were randomly assigned to each tea. Teeth were painted with fingernail polish to expose a 1 x 4 mm window and then soaked in tea for a total of 25 hours with teas refreshed every 5 hours. Teeth were then sectioned using a microtome and photographed using a polarized light microscope. Lesion depths (i.e., eroded surfaces) were measured using Image Pro Plus software. Differences in physiochemical properties and lesion depths between beverages were investigated using one-way ANOVA with post-hoc Tukey's HSD test. Relationships among lesion depths and physiochemical properties were evaluated using the Pearson correlation test. RESULTS: pH, titratable acidity and fluoride concentrations differed between tea flavors (P < 0.05) and between brands (P < 0.05). Lesion depths produced by the citrus tea (83.1 +/- 10.3 microm) were greater than those produced by the fruity tea (56.5 +/- 6.1 microm); both teas produced greater depths than black (30.1 +/- 7.4 microm), floral (25.0 +/- 3.2 microm) or green (22.3 +/- 6.3 microm) teas (P < 0.05). pH (r = -0.96; P = 0.009) was inversely and titratable acidity (r = 0.97; P = 0.006) was positively associated with lesion depths.

Fluorescence changes in remineralized and nonremineralized enamel adjacent to glass ionomer ART restorations: an in vitro study.

PURPOSE: The purpose of this study was to evaluate fluorescence changes of remineralized and nonremineralized enamel margins adjacent to glass ionomer restorations during a pH cycling sequence. METHODS: One hundred permanent molar and premolar teeth were placed in a demineralizing solution for 3 days and restored with a glass ionomer restoration (simulating Atraumatic Restorative Treatment [ART]). Half were placed in a remin solution for 7 days to create a remineralization (remin) group. Specimens were randomly divided into 4 groups (N=25): (a) 2 remin groups; and (b) 2 nonremin groups. One half of the remin and nonremin group specimens were treated with a 5,000-ppm sodium fluoride solution during pH cycling with remin fluid and an acidic beverage over 20 days. Fluorescence changes were recorded with quantitative light fluorescence (QLF). Higher fluorescence values indicated less lesion porosity. Statistical comparisons between the groups over the 5 measurement sessions of cycling were performed using repeated measures of analysis of variance with a post-hoc test, paired-sample t test and 2-sample t tests (alpha=0.05). RESULTS: The remin groups experienced significantly less lesion porosity than the nonremin groups. Fluoride groups experienced less lesion porosity than the nonfluoride groups. CONCLUSIONS: A brief period of remineralization and use of a prescription strength fluoridated rinse improved the enamel substrate surrounding glass ionomer restorations, resulting in less lesion porosity.

Effect of 2% plain and fluoridated milk on root surface caries in vitro.

The caries-protective effect of milk and fluoridated milk on enamel has been reported; however, few data are available concerning the role of milk and/or fluoridated milk on root surfaces. The aim of this study was to compare the effect of plain and fluoridated milk on root surface caries. Artificial root surface lesions were created, sectioned and analyzed using polarized light microscopy (PLM) and microradiography (MRG). The sections were covered except for the original surface and assigned to a treatment group. The samples were immersed in 2% plain milk or fluoridated milk for 40 hours and re-evaluated. Changes were measured and mean differences were compared with an unpaired t-test. Both techniques revealed a reduction in lesion depth for each milk group; however, a significantly greater reduction (p<0.05) was observed with the fluoridated milk. These results suggest that fluoridated milk may have a beneficial effect on the remineralization of root surface caries.