SOME SEALANTS SEAL - A SCANNING ELECTRON-MICROSCOPY (SEM) INVESTIGATION

White spot lesions of enamel around orthodontic brackets as a result o f demineralization have been well documented in the orthodontic litera ture. Various methods of treatment have been attempted to reduce or el iminate this danger. The purpose of this study was to evaluate, by mea ns 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, etche d with 37% phosphoric acid for 1 minute, and washed under running wate r 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, d irectly bonded; light activated Transbond was used in group D, directl y bonded brackets. After washing in alcohol for 20 seconds, all teeth were dried, and sectioned longitudinally, through the middle of the br acket. All were subjected to 5% hydrochloric acid for 30 seconds and t hen washed under running water for 30 seconds. After drying and sputte r coating, the teeth were viewed under scanning electron microscopy. G roups A and D showed a sealant layer surrounding the brackets and cove ring the buccal enamel. Groups B and C showed total absence of a cured sealant layer around the brackets or surrounding enamel. It can be co ncluded that some bonding methods (indirect) promote sealant polymeriz ation around the brackets (groups A and D), whereas other methods (dir ect) may not attain this benefit (groups B and C).