teeth it is more likely to fail, but should still be placed as early as possible, because
the teeth are more vulnerable to caries at this time.
Modifying the resin to incorporate fluoride is a logical rationale. However, fluoride
release occurs only for a very short time and at a very low level. Many studies over 2-
3-year periods have reported good retention but with a similar caries incidence to
conventional sealant. Since the addition of fluoride to sealant resin does not have any
detrimental effect it could certainly be used, but until the chemistry can be adapted to
readily unlock the fluoride, the anti-cariogenicity cannot be attributed to the fluoride.
Greater release of fluoride can be achieved using glass ionomer (poly-alkenoate).
Such cements have high levels of fluoride available for release but they suffer from
the drawback of poor retention. Even with the very poor retention rates, sealing with
glass ionomer does seem to infer some caries protective effect. This may be due to
both the fluoride released by the glass ionomer and residual material retained in the
bottom of the fissure, invisible to the naked eye.
Hence, glass ionomers, used as sealants can be classed as a fissure sealant but more
realistically as a fluoride depot material. They can be usefully employed to seal
partially erupted molars in high risk children since eruption of the molars takes 12-18
months and during this time they are often very difficult to clean. Once the teeth are
sufficiently erupted the operator may place a resin sealant. They are also useful in
children where there are difficulties with the level of co-operation, as the technique
does not depend on absolute moisture control.
Logically, improvement in glass ionomer technology has occurred and both resin-
modified glass ionomers (RMGI) and compomers have been used as sealants. As yet,
studies of these materials used as fissure sealants while available, show no
improvement over resin-based sealants and so there is nothing to recommend them in
preference to resins.
Filled or unfilled resins?
Retention is better for unfilled resins probably because it penetrates into the fissures
more completely. It also does not need occlusal adjustment as it abrades very rapidly.
If a filled resin is not adjusted there is a perceptible occlusal change, possible
discomfort, and wear of the opposing antagonist tooth.
Coloured or clear material?
Opaque sealants have the advantage of high visibility at recall. It has been found that
identification error for opaque resin was only 1% while for clear resin the
corresponding figure was 23% with the most common error being false identification
of the presence of clear resin on an untreated tooth. The disadvantage of opaque
sealant is that the dentist cannot examine the fissure visually at future recalls (423HFigs.
9.8 and 424H9.9). The choice of an opaque versus a clear sealant is usually one of personal
choice.
Safety issues