Some “sealants” seal—A scanning electron microscopy (SEM) investigation

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White spot lesions of enamel around orthodontic brackets as a result of demineralization have been well documented in the orthodontic literature. Various methods of treatment have been attempted to reduce or eliminate this danger. The purpose of this study was to evaluate, by means of scanning electron microscopy, the polymerization of the sealant layer around orthodontic brackets with direct and indirect methods of bonding. Twenty-four sound human lateral maxillary incisor teeth were collected, cleaned, divided equally into four groups A through D, and stored in 70% ethyl alcohol. Their buccal surfaces were pumiced, etched with 37% phosphoric acid for 1 minute, and washed under running water for 30 seconds. Metal brackets were bonded with the chemically cured BIS-GMA resin, Ortho Concise, as follows: group A, indirectly bonded with coping; group B, indirectly bonded without coping; and group C, directly bonded; light activated Transbond was used in group D, directly bonded brackets. After washing in alcohol for 20 seconds, all teeth were dried, and sectioned longitudinally, through the middle of the bracket. All were subjected to 5% hydrochloric acid for 30 seconds and then washed under running water for 30 seconds. After drying and sputter coating, the teeth were viewed under scanning electron microscopy. Groups A and D showed a sealant layer surrounding the brackets and covering the buccal enamel. Groups B and C showed total absence of a cured sealant layer around the brackets or surrounding enamel. It can be concluded that some bonding methods (indirect) promote sealant polymerization around the brackets (groups A and D), whereas other methods (direct) may not attain this benefit (groups B and C).

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    Placement of a resin sealant on the enamel surface before orthodontic bracket bonding has been suggested as a means of providing sustained and prolonged sealing of the enamel surface, with subsequent protection of the enamel surface against demineralization [16–18]. The benefit of using sealants to resist enamel demineralization is limited by incomplete polymerization of sealants due to oxygen inhibition of polymerization [19–21] and by reduced abrasion resistance in unfilled sealants [22]. A newly developed highly filled, fluoride-releasing, light-cured enamel sealant (Pro-Seal) offers 100% surface polymerization with no surface oxygen–inhibited layer and is proposed to provide adequate mechanical resistance [23].

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a

Registrar, Head of Orthodontic Department

b

Researcher, Oral and Dental Research Institute, University of Stellenbosch.

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