The effect of different fluoride application methods on the remineralization of initial carious lesions

OBJECTIVES: The purpose of this study was to assess the effect of single and combined applications of fluoride on the amount of fluoride release, and the remineralization and physical properties of enamel. MATERIALS AND METHODS: Each of four fluoride varnish and gel products (Fluor Protector, FP, Ivoclar Vivadent; Tooth Mousse Plus, TM, GC; 60 Second Gel, A, Germiphene; CavityShield, CS, 3M ESPE) and two fluoride solutions (2% sodium fluoride, N; 8% tin(ii) fluoride, S) were applied on bovine teeth using single and combined methods (10 per group), and then the amount of fluoride release was measured for 4 wk. The electron probe microanalysis and the Vickers microhardness measurements were conducted to assess the effect of fluoride application on the surface properties of bovine teeth. RESULTS: The amount of fluoride release was higher in combined applications than in single application (p < 0.05). Microhardness values were higher after combined applications of N with FP, TM, and CS than single application of them, and these values were also higher after combined applications of S than single application of A (p < 0.05). Ca and P values were higher in combined applications of N with TM and CS than single application of them (p < 0.05). They were also increased after combined applications of the S with A than after single application (p < 0.05). CONCLUSIONS: Combined applications of fluoride could be used as a basis to design more effective methods of fluoride application to provide enhanced remineralization.

Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential

OBJECTIVE: The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems. MATERIAL AND METHODS: The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF). RESULTS: Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified. CONCLUSION: Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies.

Comparison of effects of fluorine and lanthanum on enamel surface layer of deciduous molars / 实用口腔医学杂志

Objective:To compare effects of APF and APF-La(NO3)3 on enamel surface layer and to probe the mechanism of combined application of APF-La(NO3)3 on deciduous molars. Methods:9 caries-free second lower molars were selected and divided randomly into two groups: APF group (n=4) and APF-La(NO3)3 group (n=5). All teeth were cut into two parts, paralleled to axis of the teeth, along the line connecting mesial buccal and lingual cusps. Mesial parts were experimental group and distal parts were control group. Spot analysis of EPMA was performed to measure concentration of F or/and La in enamel surface layers, and compare changes of concentration of F in enamel surface layers treated with APF solution and changes of concentration of F and La treated with APF-La(NO3)3 solution. Results: ①Concentrations of F in enamel surface layers increased in APF experimental group. ②Concentrations of F and La increased in deciduous teeth enamel surface layers of APF-La(NO3)3 experimental group. ③ Increment of F in cusp of deciduous molar is the same as that of pit in APF experimental group. ④ Increment of F and La in cusp of deciduous molar was the same as that of pit in APF-La(NO3)3 experimental group. Conclusion:Compared with APF, treatment by APF-La(NO3)3 can increase the concentrations of both La and F in enamel surface layer while there is no difference of increment between cusp and pit in each group. The result can provide useful data for prevention of caries in children.