The effect of sealant application and sealant loss on caries-like lesion formation in vitro.

The effect of sealant placement and sealant loss on caries-like lesion formation was studied using an artificial caries technique and polarized light microscopy. The results indicate that lesion formation does not occur subjacent to an intact sealant. Even enamel which had lost is sealant was found to be caries-free. It is concluded that resin tags may be responsible for the ability of sealants to resist a carieslike attack. With the introduction of the acid-etch technique, it became possible to reduce greatly the occurrence of pit and fissure caries ’-3 and to improve the marginal integrity of composite resin restorations. 4-6 Retention of resin materials is due to penetration of resin tags into the porosities created by acid-etching sound enamel. 79 These tags may penetrate the enamel to a depth of 50 to 60 micrometersY .9 Although the caries reduction potential of sealants and sealant retention rates have been shown, many practitioners still express concern regarding the effect sealant placement has on the caries susceptibility of both unsealed etched enamel and enamel which has lost its sealant. 1° The placement of sealant or a bonding agent dramatically reduces the solubility of enamel in organic acids. 8.1’,’2 The solubility rate of sealed enamel has been shown to be reduced greatly when compared with solubility rates for sound enamel. Acid-etched enamel has a higher solubility rate than sound enamel. However, following an exposure period of one to four days to whole saliva, the solubility rate for acid-etched enamel was found to be similar to that for sound enamel. The effect of sealant loss on enamel solubility has been studied/n vitro by abrading away the sealant until no material is detected by visual and tactile examination.’.~2The solubility rate of the enamel which has "lost" its sealant was shown to be less than that for sound enamel. It was suggested that sealant tags were retained in the abraded enamel and these tags were responsible for the increased resistance to acid dissolution when compared with sound enamel. Furthermore, it has been postulated that resin tags may provide protection against carious lesion formation.S, TM The purpose of this study is to evaluate the effect of sealant placement and sealant loss on the formation of caries-like lesions/n vitro. Methods and Materials A total of 20 extracted, caries-free molar and premolar teeth were used in this study. The specimens were cleaned thoroughly with fluoride-free prophylaxis’ paste using a slowspeed handpiece. Mesiodistal cavities were prepared on buccal and lingual surfaces of the teeth using cross-cut fissure burs in a highspeed handpiece. The buccal cavities were the test sites, the lingual cavities serving as controls. The cavities were rectangular shaped with rounded internal line angles. The cavity depths were 1.0 mm or less with the cavity walls and floors placed in enamel. An acid-resistant varnish was applied to each tooth leaving the cavity and a 1 mm rim of sound enamel surrounding the cavity exposed. The cavity and the exposed sound enamel were treated with the etching solution provided by the manufacturer for 60 seconds. The specimens were washed with water for 30 seconds and air dried for 30 seconds. Sealant a was then placed in the cavity preparation. The cavity margins were sealed, resulting in featheredged margins. In order to determine the effects of sealant loss on caries-like lesion formation, the sealant was removed from five sealed cavities using a cross-cut fissure bur in a highspeed handpiece. Following sealant removal, the cavities were examined using a dental explorer and a stereo-zoom binocular microscope to make certain that no sealant was presaDelton-Johnson and Johnson Co., East Windsor, NJ. PEDIATRIC DENTISTRY: Volume 4, Number 2 1 1 1 ent. The specimens were then placed in an acidified geletin gel brought to pH 4.0 by the addition of lactic acid. This artificial caries system creates carieslike lesions in enamel which are indistinguishable from naturally occurring carious lesions. ’3 After an appropriate exposure period, the specimens were sectioned through tlie test regions and ground sections were prepared for polarized light examination. Ground sectiorLs were examined by polarized light microscopy following imbibition in water. Two zones of enamel caries may be seen in water, the negatively birefringent surface zone and the positively birefringent body of the lesion. Each cavity provided two test sites, the cervical cavity margin and the occlusal cavi.ty margin. If the sealant was ineffective at preYenting lesion formation, lesions would be present beneath the sealant along the enamel surface, the cavity wall and the cavity floor.