Micromorphology of the fitting surface of failed sealants.

Examination of sealants recovered at their moment of failure offers clues to factors which played a role in failure. The fitting surfaces of 10 failed sealants recovered immech’ately after placement, and 14 winch had failed after several months in the mouth were examined by scanning electron microscopy. Large areas of the fitting surfaces were smooth, with only localized regions showing evidence of contact with etched enamel. Those fitting surfaces exposed to the oral environment showed structures resembling micra organisms. The observations strongly suggest contamination of the etched enamel at the time of sealant placement, therefore emphasizing the importance of proper isolation methods and careful technique. The adjunctive value of pit and fissure sealants in caries prevention is now becoming well established. The results of numerous clinical studies have been compiled and most recently reported by Ripa.~ The protective benefit of sealants is only gained and maintained so long as the resin sealant remains completely intact and bonded in place. Sealants fail and when they do, failure is generally attributed to the conditions under which the sealants were placed, the skill of the operator, and the cooperation of the patient. Specific factors related to bonding at the enamel/sealant interface are also believed to influence the long-term performance of sealants. These include: I1) the type of micromorphological change in the enamel following acid conditioning, {2) contamination of the etched surface with reaction products left through inadequate washing or salivary contact, (3) the rheological properties and handling characteristics of the resin, and (4} the low abrasion or wear resistance of the resin. The sealant technique involves a prophylaxis followed by acid conditioning which renders approximately 30 microns of the outermost enamel more porous. The resin, in monomer form at the time of application, penetrates the porosities as much as 50 microns. ~,a The resin polymerizes and its entrapment in the enamel micropores serves to retain mechanically the bulk of resin located at the enamel surface. The sophisticated physical relationship between the resin and enamel can be demonstrated microscopically. 4.~ When a sealant is dislodged under laboratory conditions it commonly fails at the resin/enamel interface, which is the fitting surface of the resin with the enamel. On microscopic examination, this surface frequently shows morphological characteristics comparable with the topographical features of enamel seen after etching. The fitting surface of the resin may therefore be used as a guide to {1} the extent to which the resin wetted or gained contact with the enamel, and (2) the topographical characteristics