QUANTITATIVE EVALUATION OF FLUORIDE RELEASED FROM ORTHODONTIC ADHESIVES AND THEIR PENETRATION INTO ENAMEL SURFACE

Abstract

Objective : To compare fluoride release from 3 orthodontic adhesives and their penetration into enamel surface. Material and method : A hundred and fifty-six human premolar teeth were randomly assigned to 3 experimental groups and 1 control group (plain tooth without bonding), consisting of 39 teeth per group.The 3 experimental groups were bonded with universal metal bicuspid brackets and adhesive Fuji Ortho LC, Illuminate and Light-Bond respectively. After bonding, all samples were stored in artificial saliva (non-fluoride formula) at 37ºC. The amount of fluoride released from individual adhesive was measured by a fluoride ion-selective electrode connected to an expandable ion analyzer at 1, 3, 7 and 30 days. The artificial saliva was renewed after every fluoride measurement. After 1, 2 and 3 months, 13 teeth of each group were taken and embedded in resin blocks, then sectioned at the center of the brackets. The surfaces of the cross-sections were studied under the scanning electron microscope and the fluoride compositions under the middle of bracket base at 1, 2 and 3 µm below the outer enamel surface were determined by energy-dispersive x-ray microanalysis. The fluoride release was not normally distributed and was analysed with Kruskal-Wallis H test / Mann-Whitney U test. The fluoride penetration was normally distributed and was analysed with One-way ANOVA / Post Hoc multiple comparisons. All statistics were tested at 95% confidence intervals. Result : At 1, 3, 7 and 30 days of the means cumulative fluoride release from the three orthodontic adhesives were statistically significant differences (P< .05). The Illuminate released the most fluoride, followed by the Fuji Ortho LC and Light-Bond. All orthodontic adhesives released the most fluoride in the first day and decreased sharply to almost half in 3 days except Light-Bond that fluoride release after 3 days was non-detectable. The Illuminate released fluoride almost double ofthe Fuji Ortho LC at every observation period. At 1,2 and 3 months, the fluoride penetration was only found from Fuji Ortho LC with no statistically significant differences (P> .05) with times at all levels and the fluoride concentration decreased with depth. Conclusion : All studied Fluoride-releasing orthodontic adhesives showed an initial “burst effect” of fluoride-releasing pattern in the first day and then decreased to the low-level. Illuminate released the most fluoride, followed by Fuji Ortho LC and Light bond. Fluoride penetration found only from Fuji Ortho LC. This adhesive may act as a fluoride reservoir to prevent demineralization of enamel surface during orthodontic treatment with fixed appliances.