Fluoridated Orthodontic Adhesives' Effect on Enamel Fluoride Content and Demineralization

Abstract

Orthodontists are concerned about the high incidence of demineralization and decalcification around appliances. The orthodontic appliances diminish the self-cleansing mechanisms of the oral cavity, and in essence, act as traps for plaque and other debris that often lead to decalcification of the surrounding enamel. Fluoride containing dental restorative cements have been shown to reduce the incidence of secondary caries. The purpose of this study was to compare two fluoride containing orthodontic resin adhesives (a commercial, Phase II F, and an Experimental Adhesive) with a commercial nonfluoridated resin adhesive (Phase II). The resins were compared with respect to fluoride release in water over a 30 day period, hardness, and their effects on enamel fluoride content and enamel demineralization. Resin discs were made from the two fluoridated adhesives and placed in glass distilled water. Fluoride ion concentrations of the water were measured daily, and the accumulated concentrations were calculated for 30 days. Hardness discs were constructed from each adhesive, and Knoop hardness was measured after one hour, one day and one week. Finally, orthodontic brackets were bonded to bovine enamel discs, and two weeks after cementation of the brackets, the specimens were demineralized, and the adjacent enamel was biopsied for fluoride content. Those same specimens were sectioned longitudinally through the bracket and then stained with Rhodamin B. Areas of demineralization extending 500 μm from the bracket edge were measured by a confocal microscope. Depth of demineralization was measured at 250 μm intervals up to 1000 μm.

The Experimental Adhesive released fluoride at a significantly higher rate over 30 days than did Phase 11 F. None of the three materials demonstrated any dramatic change in hardness after one week in water. Enamel exposed to the Experimental Adhesive had the highest fluoride content followed by that associated with Phase II F. The lowest fluoride content was found in the nonfluoridated Phase 11 adhesive. The extent of enamel demineralization, in area and depth, was inversely related to the fluoride pattern, although these differences were not statistically significant. A definite trend was noted for increased fluoride content and decreased demineralization of enamel due to increased fluoride released by the Experimental Adhesive.