Occlusal wear of four pit and fissure sealants over two years.

Four different commercially available sealants were placed in caries-free permanent premolars and molars for a total of 381 teeth in 53 young participants. The volumetric loss of sealant material was evaluated over a two-year period using a tooth replica technique previously published. The pattern of progressive sealant loss was similar for all materials and for molars and premolars. Approximately 50% of the applied sealant volume was lost after one month, which was the first sampling interval. Subsequent loss occurred at a reduced rate. At the end of two years, the overall mean sealant loss was approximately 75%. There were no consistent statistically significant differences between materials regarding volumetric loss when expressed as a percentage of applied sealant volume. The introduction of pit and fissure sealants in occlusal caries prevention initially was received with enthusiasm by the dental profession. However, widespread use of sealants in clinical practice never materialized, ~ partly because of early conflicting results regarding their physicochemical and retentive properties, and partly because of behavioral and social factors. A comprehensive survey by Gift et al. in 1974 showed that more than 62% of U.S. dentists did not utilize fissure sealants in their private dental practices. 2 Recent studies have indicated that fissure sealant utilization remains at a low level. 3s One concern of the practicing dentist regarding sealants is their clinical longevity. Bulk loss of sealant due to inadequate retention to the surface enamel is a result of imperfect enamel preparation and material manipulation. Data regarding the clinical wear characteristics of various sealant formulations is sparse. It is known that wear is the result of a combination of factors including fracture and loss of filler particles, loss of resin matrix, failure of the matrix through cracking, and exposure of entrapped bubbles of air, but there is little laboratory or clinical data to identify what components of the resin impact favorably on its wear characteristics. 6 Laboratory data from abrasion wear studies, or from investigations into possible relationships between certain physical and chemical characteristics and wear in vitro 723 have been inconclusive and highly dependent on test methods used. 16,24,25 Some initial wear of the sealant is desirable, as it helps reestablish proper occlusion. Concerns have been raised regarding possible deleterious effects on the TMJ apparatus from the increase in vertical dimensions due to sealants but there are no reports in the literature of untoward side effects. The most commonly used method in evaluating the clinical performance of pit and fissure sealants is visual-tactile examination, whereby the sealant is recorded as intact, partially lost, or completely lost. However, these methods are subjective and not discriminate enough to evaluate differences in wear resistance among different sealant materials. Photometric 26 and scanning electron microscopy27 of tooth replica models also have been employed. While these two methods are useful aids in determining the extent and location of sealant coverage after a period of clinical use, neither allows quantification of sealant loss. The volumetric assessment method used in this study has been described in a previous report. 28 Using a tooth replica technique, the progressive volumetric loss of sealant material can be determined objectively and accurately. This technique has been shown to be sufficiently sensitive to discern minor differences in wear resistance among sealants. 29 PEDIATRIC DENTISTRY: March 1985/Vol. 7 No. 1 23 Methods and Materials Fifty-three study subjects, (29 females, 24 males) were selected from 12to 16-year-old patients seeking comprehensive dental care in the Department of General Dentistry at Eastman Dental Center. All unrestored, caries-.free, first and second permanent molars, maxillary first and second premolars, and mandibular second premolars were sealed. Four commercially available sealants were used, each representing a compositional variation of the prevailing sealant type, which is based on the Bis-GMA monomer. The sealant types and their physicochemical characteristics are presented in Table 1. The final study group available for evaluation at the end of the twoyear study period consisted of 381 teeth, after elimination of unusable postsealant copings. The unusable copings resulted from technical problems related to the silver plating technique and occurred on a random basis. Since meaningful results were found with the remaining teeth, it was not considered worthwhile to remake silver copings. The distribution of the final study san:~ple by material and tooth type is presented in Table 2. All sealant applications were performed by one of the authors (OEJ) according to the manufacturers’ suggestions. Care was taken not to carry any sealant material over the height of the cusp inclines. Treatments were assigned to subjects on a random basis. Each patient received the same sealant material in all quadrants. The use of different sealant materials in the same mouth, while appealing from a theoretical point of view, was rejected, since it was felt that if filled and unfilled sealants are placed opposite each other in the upper and lower jaws, or if one side receives a filled sealant and the other an unfilled sealant, interpretation of the initial wear patterns could be distorted because the different sealants may have different wear characteristics. Furthermore, attempting to achieve complete randomization of the four sealants in the four quadrants within the study group would increase the complexity of the study design, and loss of subjects seriously would have affected the integrity of the randomization. Measurement of the volume of sealant applied and subsequent sealant loss was done according to the technique described by Handelman et al. ~s with two exceptions. Reprosil a vinyl polysioloxane was used as the impression material and Epoxydentb epoxy resin was used to fabricate tooth replica dies. Tooth replica dies were fabricated from full-arch impressions taken prior to and again immediately after sealant placement, and at each recall visit. The immediate postsealant impression was taken after thoroughly removing the unpolymerized resin with an alcohol gauze. Silver copings were made by electroplating the immediate postsealant tooth replica die. Then copings partly were embedded in an acrylic block to ease handling. The volume of applied sealant material and subsequent volumetric sealant loss was determined by placing each die in the silver coping made from the immediate postsealant die and weighing the impression material that filled the void between the die and its respective coping. To ensure that a reproducible force was exerted on each die and coping, the assembly was placed in a modified C clamp partly embedded in stone (Fig 1). The screw of the C clamp was turned clockwise in contact with the center of the tooth replica die until the spring-supported acrylic disc was level with the stone. After the impression material had set completely, the excess material was removed with the aid of a scalpel. The tooth replica die was removed and the remaining material was weighed. Three measurements were obtained for each tooth replica die at each measuring point. Since the specific gravity of Reprosil ® was 1.0, 1 mg of impression material was equivalent to I mm3 of volume. The volumetric assessment was repeated twice for each The L.D. Caulk Co., Milford, DE. Oxy Dental Products, Inc., Hillside, NJ. TABLE 1. Bis-GMA Type Sealants Used in the Study Filler Brand Name Incorporated Delton ® No