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The American Academy o! Pediatric Dentisuv• Volume 1)/ Number 1

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Resistance of occlusal fissures to demineralizationafter loss of glass ionomer sealants in vitroLiisa Seppã, LicOdont, DOdont Helena Forss, LicOdont

Abstract

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Seueniv-one caries-itee huina n occ/ usal físsures were usedfor this study. Tuicniq-tuio físsures were scalcd with a glassionomer sealant (Fuji Iononier Type m® - c-c Dental In-dustrial Corp. Tokyo, [apan), 24 were uiidened with aâiamond bur and sealed with theglass ionomer sealant.and 25

were left unsealed. After one week, ihe sealants were remouedas completely as possible with a probe. Ali fissures weredemineralized for senenweeks. Sections made frOI/1 lhefissures uiere examined unth a potarizing microscope, and thedepths of lhe fissure tesions were nieasured. Tire mean lesiondepths for controle, sealed natural fissures, and sealed wid-ened [issures were 143, 93, and 75 11m, respectively. Astalistically significant difference was noted betuieen thc fwoexperimental graups and the conirol group (no sealant). Theresulls suggest that [issures sealed untlt glass ionomer aremore resistani to demineraíization tltan control fissures, evenafter macroscopic sealant loss. This lIIay be tire result of ti/ecombined effect of fluoríde released by glass ionomcr andresidual material in lhe botiom of the fissures.

Introduction

1 ,

The use of glass ionomer cement as a fissure sealantmaterial has increased in recent years. So far, fewstudies of its efficacy have been reported, and the resultsof these studies have been conflicting. In the study byWilliams and Winter (1981) using glass ionorner fillingcement as a sealant, sealant loss was higher for glassionomer than for resin, but there was no significantdifference in caries incidence between teeth sealed withthese.two materials, McKenna and Grundy (1987) re-ported that the retention of glass ionomer cement was93% after six months. However, studies by Shimokobeet aI. (1986) and Boksman et al. (1987) using a gIassionomer material specialIy designed for fissure sealing,almost a11sealants were Iost within the first six months.

. An interesting finding in the studies by Williams andWinter (1981) andby Shimokobe et al, (1986) was thatgIass ionomer sealants seemed to exert a cariostatic

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effect, even after they had disappeared macroscopi-calIy. Long-tenn retention may not be necessary :: thematerial has anticariogenic properties that increase thecaries resistance of newly erupted fissures. Fluoridereleased from gIass ionomer and taken up by enamel(Forsten 1977; Retief et aI. 1984; Swartz et aI. 1984; Forssand Seppã 1990) may give prolonged protection. On theother hand, in our dinical study, microscopic exami-nation of occlusal surfaces showing partial or totallossof sealants revealed that in most cases, residual material'was observed in the bottom of the fissures (Torppa-Saarinen and Seppã 1990).

In the case of resin sealants, dinicians still debatewhether ar not it is necessary to widen narrow fissuresbefore sealing (Meiers and Jensen 1984). As for glassionomer, McLean and Wilson (1977) found that thefilling cement could not penetrate fissures narrowerthan 100 11m,and recommended widening the fissuresbefore sealing. AIthough a material with smaller par-tide size, such as glass ionomer developed for fissuresealing, seems to penetra te deeper into the fissures '(Mount and Makinson 1978), widening might improveretention of glass ionomer sealants anel provide longerprotection. However, there is no information 011 _'oresistance of widened fissures in the case of sealant loss.

The purpose of the present study was to examinewhether fissures sealed with a glass ionomer cementdesigned for fissure sealing are less susceptible to'demineralization than control fissures, even after thesealant has been removed. Another purpose was tostudy the effect of widening the fissures on resistance to .demineralization after sealant loss.

Materials and MethodsTen human third molars and 30 remolars were used

for t 1e study. Ali fissures were caries free by visualínspection .. After extraction, the teeth were stored in ..40% ethanoI. The crowns were separated from the roots .

PEDIATRICDENTlSTRY:jANUARy/FEBRUARY - VOLUME 13, NUMBER 1 39

.' -and bisected longítud inall y, except for a few premolarswith a very short occlusal fissure. The tooth halves weredivided randornly into three groups. The fissures in thefirst group were left unsealed, The fissures in the secondgroup were cleaned with a rotating brush'and pumice,rinsed carefully, and sealed with glass ionomer sealant(Fuji Ionomer Txpe m® - G-C Dental r nd ustrial Corp.,

, Tokyo, japan) using a small ballpoint instrumento, Mixing was performed according to the manufacturer' s. instructions, When the sealanl had lost ils glossincss, itwas covered with a varnish provided by the manufac-turer. The fissures in the third group were widenedwith a nàrrow, flame-type diamond bur (di'ametera:5mm) _~&._~!_~!~~.i&~:_~p~e~. Carc wns InkL'11not [openetra te 1nto the dentin. The occlusal surfaces were

1 cleaned with pumice, rinsed, and sealed, as in the sec-~;ond group. .: '.'t ~.~·iE~~_.~ample was stored for on~n a test tube;yCohtaining ilistilled water. After that, the sealants were~Jên1ovéd as completely as possible with a sharp probe,1soi.that -no residual material was left in the fissures"macroscopically. Ali tooth surfaces (except for thesfissures) were covered with acid-resistant wax.(Ptepon® - Bayer, Wetzlar, Cermany), The samples'thén Were immersed for seven weeks in 0.1 M lactic acid

~ buffer.ipl-l 4.3 in 5% carboxymetylcelÍ~19_~~t~p~-~-uceartificial fissure l~ons. After deminerallzation, longi-tuomal sechons were cut from the sarnples and thesectíons were ground to approximately 90 11m thick.The -fissure lesions were viewed with a polarizingmiéroscopé (Leitz Diaplan® - Leitz, Wetzlar, Ger-many) and photographed. TIH~depth of the lesion wasassessed frorn the photomicrographs by rneasuring

; . traverses running perpendicular to the enarnel surfaceat six standardized points (Fig. 1), and the means of sixmeasurements were calculated.- , Data were analyzed using one-way analysis of vari-

ance for t1etecting significant differences and Scheffe'smultiple comparison tests for pairwise comparisons.

Results5eventy-one fissures were sectioned successfully.e méan depth of fissure lesions was 142.8 um (50

3.8) in control fissures (N = 25), 92.7 11m(50,6) in sealednatural fissures (N = 22), and 75.1 11m (35.7) in sealed" idened fissures (N= 24, Fig. 2). The differences be-

"eeJl the control and sealed fissures were statistically"gnificant (P < 0.01), whereas the difference between

tural and widened fissures was not significant. Figs- • (see next page) show typicallesions in sealed and

control fissures.iàualsealant material was observed insix natural

~='-L.~ a d in four widened fissures. No lesion waser lhe residual material.

U v!FEBRUARV - VOLUME 1 J, NUMOER 1

Fig 1. A diagram c1escribing lhe measurernent technique. Thearrows show the points at which the measurements of lesiondepth were made.

200E:::l.

I 150f-o,WO 100zOü5W-l 50

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Fig 2. Mean lesion depth, I = contrai, 2 = sealed natural (issures,J = sealed wiclened fissures.

DiscussionThe long-term retention of resin sealants is 60-80%

(Mertz-Fairhurst et al, 1984; Simonsen 1987; Wendt andKoch 1988). Even though the initial retention rate is high(Weintraub 1989), regular contrai of surfaces sealedwith resin sealants is necessary, at least during the firstfew years. For glass ionomer sealants, the retention rateappears to be lower, although long folIow-ups have notbeen reported. However, the present results suggestthat the fissures sealed with a glass ionomer sealant aremore resistant to dernineralization than unsealed Iis-sures, even after the sealant appears to be lost. This maybe the result of the combined effect of the increasedfIuoride levei of the enamel ar pia que, and residual

material in the fissures. Although sectioning of thefissures probably removed most of the residual mate-rial, sometimes it was observed in the bottom of thefissures. This is probably often the case clinically aftervisible sealant loss, as observed in our previous study(Torppa-Saarinen and Seppâ 1990).

"1 The results also suggest that widening fissures doesnot make them more prone to demineralization thannatural fissures, even when the sealant is lost macro-scopically. A tendency to decreased demineralizationin the widened fissures when compared to sealed natu-ral fissures probably resulted from enhanced retention Boksman L, Gratton DR, McClItcheon E, Plotzke OB: Clinical evalu-of residual material, although, because of sectioning, ation of a glass ionorncr cerncnt as a fissure scalant. Quinh.ssencch Int 18:707-9, 1987.

t is could not be confirmed in the present study. Forsten L: Fluoride release from a glass ionomercement. Scand] DentWhen considering the results, one must remember Res 85:503-5, 1977.

that an in vivo experiment does not fully reflect oral Forss H, Seppâ L: Prevention of enamel demineralization adjacent toconditions. It also should be emphasized that although glass ionomer filling materials. Scand J Dent Res 98:173-78, 1990~glass ionomer sealants increased the resistance to MeKenna EF, Grundy GE: Glass iõi10mer eement fissure sealants

applied by opera tive dental auxiliaries retention rate after onedemineralization considerably, lesion formation was year. Aust Dent J 32:200-3,1987.not inhibited completely, Thus, the results do not allow Mcl.ean JW, Wilson AD: The c1inical developrnent of the glassus to conc1ude that resealing of fissures in the case of ionorncr cerncnt. ll, Some clinical applications. Aust Dent jS 1 t I . ith I . 22:120-27,1977. ,ea an oss IS never necessary wi g ass ionomers. Meiers [C, [ensen ME: Managernent of the questionable carious fis-However, glass ionomer may be a good alternative to sure: invasive vs noninvasive techniques. J Am Dent Assoeresin sealants, at least when regular check-ups and 108:64-68,1984.rapid resealing of fissures showing sealant loss are not Mertz-Fairhurst EJ, Fairhurst CW, Williams JE, Della-Giustina VE,possible. Whether the fissures sealed with glass // Brooks JD: A comparative clinical study of two pit and fissure

sealants: 7-year results in Augusta, GA. J Am Dent Assoe 109:252-55,1984.~

fig 3. A typical fissure lesion in a widened fissure sealed withglass ionomer.

fig 4. A typical fissure Iesion in a contraI fissure.

ionomer remain caries resistant for long periods can beassessed only in a long-term clinical study.

We are grateful to Ms Hanna Eskelinen for skillful teehnical assis-tance.

Dr. Seppã is assistant professor and Dr. Forss is an instructor in theDepartment of Preventive Dentistry and Cariology, Faeulty of Den-tistry, University of Kuopio, Finland. Reprint req~est5 shpuld be sentto: Dr. Liisa Seppa. Department of Preventive Dentistry andCariology, Faculty of Dentistry, University of Kuopio, P·.O.B.6, SF-70211, Finland.

PEOIATRIC DENTISTRY: jANUARY/FEBRUARY - VOLUME 13, NUM8ER 1 41

Mount G], Makinson OF: Clínical characteristics of a glass-ionomer'cement. Br Dent J 145:67-71, 1978.

: Re~JefDH, Bradley EL. Dentorr[Ci Switzer P: Enamel and cementum •.,·,t"f' ~~oride uptake from a glass-ionomer cement. Caries Res 18:250-I· ~57}1984 ' .. shtlnbkobe ri,Komntsu H, Knwaknmí S, Hirota K: Clinicnl evaluation" .'.1 'bf'gláss-Ionomer cement used for seala nts. J Dent Res 65:812 (abst rfi .0),1i986. .

::JSim ., e.fi'R]:: Retention and effectiveness of a single application of:,yq: whíte sealant after 10 years. J Am Dent Assoe 115:31-36. 1987.!,:~>Jli ii " ,:;::''')"'1'~--------:-------------'~~;i}llt'Ir!:t:i I ! ~ 1:

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Swartz ML, Phillips RW. Clark HE: Long-term F release from glass,ionomer cements.] Dent Res 63:158-60.1984.

Torppa-Saarinen E, Scppâ L: Short-term retention of glilss-ionomerfissure sealants. Proc Finn Dent Soc 86: 83-88.1990. '

Weintraub ]A: The effectiveness of pit and fissure sealants. J PublicHealth Dent49:317-30, 1989., -

Wetidt L-K, Koeh G: Fissure scalnnt in pcrrnnucnt Ilrs] molars aftcr 10years. S~~DenUJ2:181-85, 1988..

Williams B,Winter GB: Fissure sealants. Further results at 4 years. BrDent J 150:183-87, 1981.

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42 PEf'IATRIC DENTlSTRV: )ANUARV/FEURUARV - VOLUME 13, NUMIlER 1