Tooth-Cleaning, EnamelPreparation, and ToothSurfaceTreatmentPrior to SealantPlacement

Most of the manufacturers’ instructions for the use of fissuresealantsrecommendcarefulcleaning of the pits and fissuresbeforeacidetching. A studyreported that there is in fact no difference in sealantretentionbetweentoothbrush and handpieceprophylaxis at two to fiveyearfollow-ups [53].

Somemanufacturers’ instructionsstate that the use of fluoridebeforesealantplacement is contraindicatedas it decreasesenamelsolubility in acid and thusinhibitsproperetching of the enamel. However, Warren et al. compared the sealantretention of two sealantmaterialsbefore and afterfluoridetreatment over an 18-monthperiod. Theyreported a significantlygreaterretention on fluoridatedteethwhen LRBS wasused and no significantdifference in retentionwhen ARBS wasused. This suggested that sealantretentionmay not be impaired by fluorideapplicationimmediatelyprior to sealantplacement [54]. Similarly, anotherstudyreported that the use of fluoride-containingprophylaxispaste or anyfluoridetreatmentbeforesealantapplicationdoes not adverselyaffect the sealant’sbonding to enamel [55]. One more studyalsoevaluatedsealantretentionwhentreating the enamel with a topicalfluoridegelbeforeacidetchingclinically and in-vitro. It wasfound that therewas no statisticallysignificantdifferencebetween the retentionrate of the sealantappliedaftertoothsurfacetreatment with topicalfluoride and the controlgroup that did not receiveanyfluoridetreatmentprior to the sealantapplication [56]. Furthermore, manystudieshaveinvestigated different methods of mechanicalpreparation of the fissures, suchas air abrasion, eliminatingfissures with a dentalbur, and sandblasting, prior to the sealantplacement. Interestingly, it wasfound that fissureeradication is not necessary. Enameloplasty, using any of the above-mentionedtechniques, removes the enamellayeroverlying the dentin at the bottom of the fissure, making the tooth more susceptible to caries if the sealant is lost [20,57]. There is conflicting and limitedevidenceregarding the benefits of using a bur for fissurecleaning or for the purpose of increasingretention, prior to sealantplacement [32,58].

Isolation

Adequatemoistureisolationduringresinsealantplacement is the mostcriticalstep in sealantapplication. If the etchedenamelgetsexposed to salivaryproteins for aslittleas 0.5 s, it can be contaminated [36]. If this occurs, re-etching is required. The use of a rubberdam is the idealway to achieveoptimummoisturecontrol. The use of cottonrolls and a salivaejector is also a validoption [59]. The use of moisturecontrolsystems, suchas the Isolite® system (InnerliteIncorporation, Santa Barbara, CA, USA) provides less time for the procedure and offerscomparablesealantretentionrates to cottonrollisolation or the use of a rubberdam [60].

A systematic review hassuggested that four-handeddelivery, compared to two-handeddelivery, increasessealantretention by 9% whenotherfactors, suchas the surfacecleaningmethod, werecontrolled [61]. The use of the four-handedtechniquefacilitatessealantplacement and is alsoassociated with improvedretention [32].

AcidEtching and Rinsing

The phosphoricacidconcentration that wasoriginallyused for etching by Buonocore in 1955 was 85%, but it wasthenreduced in hisearlyclinicalstudies to 50% [18]. Nowadays, 35% and 37% are the commonlyusedconcentrations. Acid-etching times havealsobeenreduced from 60 s down to 20 s [62].

Earlyrecommendations for primaryteethenameletching time were double the accepted time for permanentenamel, namely, 120 s for primaryenamel and 60 s for permanentenamel. The early in vitrostudiesshowed that 120 s are necessary for an adequateetchingpattern in primaryteethenamel to eliminate the identification of prismlessenamel. This findingwasfound not to be clinicallysignificant for sealantretention, asdemonstrated by Simonsen et al. in 1978. Hisstudyincluded 56 childrenbetween the ages of 3–8 years with 373 deciduous first and secondmolars that weresealed and examinedsixmonthspost-application; 178 teethwereetched for 60 s and 195 teethwereetched for 120 s. The retentionrate for the 60 s etchedteethwas 100%, and for the 120 s etchedteeth, it was 99% [8,23]. Moreover, the shorteretching time decreases the chance of salivacontamination, particularly in pre-cooperativechildren.

An in-vitrostudyevaluated the etchingdepth and bondingstrength of 130 exfoliatedprimaryteethafter the following four different etching times: 15, 30, 60, and 120 s. Despite the greaterincrease in depthafter 120 s etching time, the meanbondstrengthsobtained for the fouretching times were not significantly different [63]. Anotherstudyshowed that the length of etching time haslittleeffect on sealantretention. No significantdifference in fissuresealants’ retention on primary or permanentmolarswasfoundafter a one-year follow-up with different etching times of 15, 30, 45, and 60 s [64].

A rinsing time of 30 s and drying the tooth for 15 s should be sufficient to remove all acidetchantresidues and achieve the characteristicchalkywhiteenamelfrostyappearance [20,22].

BondingAgents

The idea of using a bondingagentunder the sealantcame from Feigal et al. in 1993 whentheyusedhydrophilicbondingmaterials to aid the bondstrengthwhen the sealant is applied in a moist environment [65].

Therehavealreadybeeneightgenerations of bondingagents [66,67,68], the latest and eighth one beingintroduced in 2010. It is characterized by the incorporation of nano-fillersinto the adhesivecomposition to improve the mechanicalproperties of the adhesivesystem. However, the mostrecenttype in adhesivedentistry is called the universal adhesive or the multi-modeadhesive. It was first introduced in 2011. This kind of adhesivesystem can be usedas an etch and rinseadhesive, a self-etchadhesive or to do self-etch on dentin and etch-and-rinse on enamel; this particulartechnique is calledselectiveenameletching. Itscompositiondiffers from the otheradhesivesystems that allowchemical and micromechanicalbonding [67]. Severalstudiesevaluated the use of a bondingagentbeforesealantapplication. A randomizedcontrolledtrialcomparedfourthgeneration (three-step-etch-and-rinse) and fifthgeneration (two-step-etch-and-rinse) adhesiveswhenusedundersealants. Theyfound that the two-stepadhesivesreduced the risk of sealantloss by half (Hazardratio = 0.53) whenapplied on occlusalsurfaces. On the otherhand, the three-stepadhesiveshad a detrimentaleffect on the sealantretentionrate, which can be explained by the composition of the adhesive, as it is water-based, and waterhas a deleteriouseffect on sealantbonding. The two-stepadhesive is acetone- or ethanol-based, whichmay be more effective in bonding to etchedenamel [69].

With regard to self-etchadhesives, a recentclinicaltrialevaluated the sealantretentionrate and cariespreventiveefficacy over a three-yearperiod. Theycomparedthreeadhesivegenerations, namely, fourthgeneration (three-step-etch-and-rinse), fifthgeneration (two-step-etch-and-rinse), and sixthgeneration (one-step, two-component-self-etch) with the conventionaltechnique, which is etching with no adhesiveapplicationas a control. Therewas a significantdifferencebetween the retentionrates of sealantscombined with the variousadhesivesystemsused (p < 0.05). The highestretentionrates of sealants on the first permanentmolars at a 36-monthrecallwerecombined with the fourth and fifthgenerationadhesivesystems and were 80.01% and 74.27%, respectively. In contrast, the lowestretentionrateswerecombined with the sixthgenerationadhesivesystem (42.84%) and with the conventionalacid-etchtechnique (62.86%). Theyalsofound that the fissurecariesincidencerate in first permanentmolars that hadbeensealedafter using the sixthgenerationadhesivesystemwas 34.28%, whichwassignificantlyhigherthanwhenotheradhesivesystemshadbeenused [70]. This was in agreement with a previouslypublishedstudy that reported a significantlybetterretentionrate with the etch-and-rinseadhesivesystem (fifthgeneration) compared to the self-etchadhesivesystem (sixthgeneration) at a 12-month follow-up [71]. Anotherstudy, on the otherhand, evaluated the retentionrate of fissuresealants in primarymolars using a sixthgeneration (one-step, two-component-self-etch) adhesivecompared to the conventionalphosphoricacid-etchingtechnique with no bondingagentapplication. Theyfound no statisticallysignificantdifference in sealantretention in the two groupsafter a one-year follow-up period [72].

A recentsystematic review compared the retentionrate of sealants, combined with self-etchadhesivesystems(sixth or seventhgeneration), with that of etch-and-rinseadhesivesystems (fourth and fifthgenerations). Fivestudieswereinvolved: threestudiesshowed that etch-and-rinseadhesivesystemshadsignificantlybetterretentionthanself-etchadhesivesystems. The other two includedstudiesshowed no significantdifferencebetween the two adhesivesystems. Feigal and Quelhas in 2003, for example, reportedsimilarretentionrates of 61% at 24 months. However, the sample in this studywassmall (18 molarsonly) [73]. The systematic review concluded that the retention of occlusalfissuresealants is higherwhenapplied with the etch-and-rinseadhesivesystemthan with the self-etchadhesivesystem [74].

Finally, a recentsystematic review by Bagherian et al. evaluated the fissuresealantretentionrate with or without the use of an adhesivesystem and alsocompared the retentionrate of sealantswhen using etch-and-rinseadhesivesystems (fourth or fifthgenerations) versus the rateachievedwhenself-etchingadhesivesystems (sixth or seventhgenerations) wereused. Theyfound that the adhesivesystemhas a positiveeffect on the retention of the fissuresealant. The adhesivecomponentsmayincrease the penetrationintoenamelporosities and thusincreasebondstrength. It wasalsofound that etch-and-rinseadhesivesystems are superior to self-etchadhesivesystems in terms of sealantretention [75]. However, in a recent, randomizedcontrolledtrial, Khare et al. evaluated the integrity of fissuresealants by comparing the use of fifth, seventh, or Universal bondingsystems with a no bondingprotocol at 3-, 6- and 12-monthfollow-ups. At the 12-month follow-up, fifthgenerationbonding and universal bondingprotocolsperformedbetterthanseventhgeneration or no-bondingprotocols, but the differencebetween the groupswas not statisticallysignificant [76].

In summary, the above-mentionedstudiesindicated that the use of adhesivesystemsprior to fissuresealantapplicationhad a positiveeffect on increasingpenetration and improving the retentionrate. It alsoappears that the use of bonding-agents that involve a separateacid-etchingstep (fourth and fifthgenerations) providesbettersealantretentionthanself-etchingadhesives (sixth and seventhgenerations). Etch- and-rinseadhesivesystemsproducebetterpenetration of the enamelsurfacethanself-etchadhesivesystems, and this mayresult in a betterbondstrength.

An evidence-based 2008 report from the American Dental Association and the American Academy of PediatricDentistry supports the use of adhesivesystemsbeforesealantapplication for bettersealantretention [32,58].