Glass IonomerSealant Materials

Conventionalglassionomer (GI) materialhasalsobeenusedaspit and fissuresealants. It bondschemically to enamel and dentinthrough an acid-basereactionbetween an aqueous-basedpolyacrylicacidsolution and fluoroaluminosilicateglasspowder [28]. GI sealants can be classifiedintolowviscosity and highviscositytypes. It is important to recognize that most of the studies on GI sealantsusedold-generation, low-viscosity GI, suchas Fuji III GI sealant that haspoorphysicalproperties. It hasnowbeenreplaced with a latergeneration, suchas Fuji Triage (VII) (GC, Tokyo, Japan), that hasbetterphysicalproperties and is designed to release a higheramount of fluoride [29]. High viscosityglassionomercement (HVGIC), suchasKetacMolarEasymix (3M ESPE, Seefeld, Germany) and Fuji IX (GC, Tokyo, Japan), hasbeenused in studies following atraumaticrestorativetreatmentapproach (ART). The ART conceptconsists of two components, namely, ART sealant and ART restoration. ART sealant is the preventivecomponent that includes the application of HVGIC on vulnerablepits and fissures using the finger-presstechnique [30].

Whenresin is incorporated with glassionomer, it is called a resin-modifiedglassionomer (RMGI). It hasalsobeenusedas a pit and fissuresealantmaterial. The settingreaction of this type of sealant is initiated by the photoactivation of the resincomponent, followed by the acid-basedreaction for the ionomercomponent. Itsresincomponenthasimproveditsphysicalcharacteristics, compared to conventional GI [22]. In fact, whencompared to conventional GI, RMGI has less sensitivity to water and a longerworking-time [28].

In general, the main advantage of a glassionomercement-basedsealant is the continuousfluoriderelease and the fluoriderechargingability. Itspreventiveeffectmayevenlastafter the visibleloss of the sealantmaterialassomeparts of the sealantmayremaindeep in the fissures. It is moisture-friendly and easier to place and is not vulnerable to moisture, compared to the hydrophobicresin-basedsealants [22]. It can be usedas a transitionalsealantwhenresin-basedsealantscannot be useddue to difficultmoisturecontrol in, for example, partiallyeruptedpermanentteeth, especiallywhen the operculum is covering the distalpart of the occlusalsurface [31]. GI sealant can also be useful in deeplyfissured, primarymolars that are difficult to isolatedue to a child’spre-cooperativebehavior [20]. It is considered a provisionalsealant and has to be replaced with a resin-basedsealantwhenbetterisolation is possible [32].

Polyacid-ModifiedResinBasedSealants

Polyacid-modified, resin-based composite material, which is alsoreferred to ascompomer, hasbeenusedas a fissuresealant. It combines the advantageousproperties of a visiblelightpolymerizedresin-basedsealant with the fluoridereleasingproperty of the GI sealant. A polyacid-modifiedresin-basedsealanthas a betteradhesionproperty to enamel and dentin and is also less water-soluble, compared to GI sealantmaterial [33], and less technique-sensitive, compared to resin-basedsealants.

Different Sealant Materials and CariesPrevention

Sealant vs. No Sealant

The role of fissuresealants in cariesprevention is well established in the literature. There is also a moderatequality of evidence that sealantsreduce the incidence of caries by 76% on sound occlusalsurfaces, compared to the non-use of sealantsduring the two to threeyear follow-up period [28].

A recent update of a Cochrane review evaluated the cariespreventiveeffect of sealants in children and adolescents, compared with a no sealantcontrolgroup. Thirtyeighttrials with a total of 7924 participants, agedbetween 5 and 16 years old, wereincluded. Fifteentrialscomparedresin-basedsealantswhenapplied to the first permanentmolars with no sealant and showed a moderatequality of evidence that resinsealantsreducedcariesincrement by between 11 percent and 51 percent in a two year follow-up period. If cariesincrementwas 40 percent in controlteethsurfaces, the application of sealantreduced the cariesincrement to 6.25 percent. At longer follow-up periods of 48 to 54 months, the cariespreventiveeffect of sealantswasretainedbut the quality of evidencewaslow [34]. This is in agreement with the results of the previouslypublished review [35].

Whencomparing the cariespreventiveeffect of glass-ionomerbasedsealants with the use of no sealant, no conclusioncould be drawn on whether GI sealantpreventedcaries, compared to no sealant, at a two year follow-up, due to the verylowquality of evidence [34,36].

Sealant vs. FluorideVarnish

Severalpublishedstudiescomparedpit and fissuresealants’ effectiveness to that of fluoridevarnish in cariesprevention on occlusalsurfaces. A recent update of a Cochrane review concluded that there is only a lowquality of evidence that pit and fissuresealantshave a superioroutcome, whencompared to fluoridevarnishapplication, in the prevention of occlusalcaries. This conclusion is similar to that found in the previous review in 2010 [37]. Two out of threestudiesincluded in the last updated review showed a significantlybetterperformance of sealants, compared to fluoridevarnish, while the thirdstudyreported that the benefits of sealantwere not statisticallysignificant, compared to fluoridevarnish. Two of the includedstudieswereassessedashaving a highoverallrisk of bias and the thirdashaving an unclearoverallrisk of bias [38]. The recentevidence-basedguidelines of the American Dental Association (ADA), in collaboration with the American Academy of PediatricDentistry (AAPD), recommend the use of sealants in preference to no sealant or fluoridevarnish, although the quality of evidence for this recommendationwasfound to be low [5,28]. In fact, this runscounter to the results from a recentrandomizedclinicaltrial that compared the clinicaleffectiveness for cariesprevention of fluoridevarnish and fissuresealants at a threeyear follow-up among a 6 to 7 years old population. Afterthreeyears of follow-up, 17.5% of the fluoridevarnishgroup and 19.6% of the fissuresealantgroupdevelopedcaries in theirdentin. The differencebetween the two groupswas not statisticallysignificant [39].