Isolation is the most critical issue in the proper placement of sealants. If the surface of the etched tooth is contaminated by saliva, the resin material will not adhere because the remineralization process begins as soon as saliva touches the etched surface. Sealant loss and immediate failure of retention are most often linked to moisture or salivary contamination. A rubber dam is the ideal method for tooth isolation for sealants, but it is not always possible or appropriate for young children. Cotton rolls, dry field pads, dry field kits, and single tooth isolation are all used with success. New materials are being studied that are moisture-tolerant, further investigations are underway (Figure 9 illustrates acceptable isolation methods).
If using a glass-ionomer product, isolation is not necessary as these products are not sensitive to moisture contamination.