Microscopic evaluation of the thickness of sealants used in orthodontic bonding

Placement of a resin sealant on the enamel surface prior to orthodontic bracket bonding has been suggested as a means of providing protection against demineralization, particularly at known sites of plaque accumulation. The duration of protection is influenced by resin sealant thickness and distribution. The object of this study was to determine the thickness of polymerized sealant at the vulnerable bracket/resin periphery. Six groups of ten extracted caries-free teeth were bonded with metal brackets using six commercially available bonding materials and their respective sealants. Scanning and light microscopy were used to map sealant distribution and measure sealant thickness at the bracket/resin periphery. Results showed a wide range of sealant thickness, from 0 to 228 micrometers, with considerable intraproduct variation. It was concluded that thin resin films, with their low abrasion resistance, cannot be expected to provide long-standing protection against demineralization.