Marginal Adaptation of Compomer Ciass V Restorations in Vitro Uwe BlunckVJean-François Roulet^ Purpose: The purpose of this in vitro study was to determine the marginal adaptation of different adhe- sives, including recently developed self-etching phmers, in combination with compomers in Class V cavi- ties. Materiais and Methods: In 80 extracted human teeth, divided into 10 groups ot 8, Class V cavities were prepared (ca. 4 mm high, 3 mm wide, and 1.5 mm deep) with one half ofthe margin iength in dentin. The one-bottie adhesiues Prime & Bond 2.1, Syntac SC, and Espe OSB, and the seif-etching primers Rasant F 2000 and Prompt L'Pop were used in combination with compomers. Before and after thermocycling (TC), repiicas were taken and a quantitative margin anaiysis using the SEM was performed at a magnifica- tion of 200x using defined criteria. Resuits: The statistical analysis using Kruskal-Wallis and Bonferroni tests showed a significantly (p < 0.05) better marginal adaptation in enamei and dentin for the self-etching primers, and when the one-bottle ad- hesives were used in combination with the total-etch technique. Conciusion: Self-etching primers improve the marginal adaptation of oompomer restorations in enamei. } AOhesive Dent 1999,1:143-151 Submitter] for pubiication: 16.02.99; accepted for publication: 23.02.99 S ihce glass-ionomer cements were introduced in 1969, they have been continuously modified. While glass-ionomer materials harden by an acid- base reaction,22 the resin-modified glass iono- mers^^ include an additional polymerization reac- tion. This results in more favorable working charac- teristics, such as prolonged application time, and improved properties, such as reduced sensitivity to early water contamination. The more recently devel- oped "compomers" are polyacid-modified resin composites,i8 and were introduced to the dental profession as a restorative material which com- ' Professor Associate, Dept of Operative Dentisfry. Preventive Den- tistry, ana Endodontics, School of Dental Medicine, Hurnbolót Uni- versity Berlin (Charité), Germany. " Professor, Dept. of Operative Dentistry, Preventive Dentistry, and Endodontics, School of Dental Medicine, Humtiolút University Berlin (Charité), Germany Repiint requests; Dr. Uwe BluncK Dspt. of Operative Dentistry, Pre- ventive Dentistry, and Endodontics, School of Dental Medicine, Hum- boldt University Berlin (Charité), Augustenburger Piatz 1, D-13353 Berlin, Germany. E-mail: ubtLinck®charite.de bines the advantages of glass-ionomer cements (fluoride release) and composite resins (wear resis- tance and better esthetics). These materials consist of polyacid-modified dimethacrylate monomers re- inforced with ion-leaching glass particles similar to those in glass ionomers. Since they contain no water, the setting reaction can only take place as a polymerization reaction as in composite resins. Un- like glass ionomers, compomers cannot establish a bond to tooth structure by themselves, and there- fore have to be placed in combination with an adhe- sive system.^'^ The kinetics of polymerization and the lower Young's modulus of elasticity of compomers'^'^^ are the reason for reduced polymerization shrinkage stress during the setting reaction of compomers. Therefore, in comparison to composite resins, only reduoed forces interfere with the bonding capacity of the adhesive to enamel and dentin when com- pomers are used. Several ¡n vivo studies have shown that the application of one-bottle adhesives without acid-etching enamel and dentin is effective Voi 1, No 2 . 1 9 9 9 143
Transcript
Marginal Adaptation of Compomer Ciass VRestorations in Vitro
Uwe BlunckVJean-François Roulet^
Purpose: The purpose of this in vitro study was to determine the marginal adaptation of different adhe-sives, including recently developed self-etching phmers, in combination with compomers in Class V cavi-ties.
Materiais and Methods: In 80 extracted human teeth, divided into 10 groups ot 8, Class V cavities wereprepared (ca. 4 mm high, 3 mm wide, and 1.5 mm deep) with one half ofthe margin iength in dentin. Theone-bottie adhesiues Prime & Bond 2.1, Syntac SC, and Espe OSB, and the seif-etching primers RasantF 2000 and Prompt L'Pop were used in combination with compomers. Before and after thermocycling(TC), repiicas were taken and a quantitative margin anaiysis using the SEM was performed at a magnifica-tion of 200x using defined criteria.
Resuits: The statistical analysis using Kruskal-Wallis and Bonferroni tests showed a significantly (p < 0.05)better marginal adaptation in enamei and dentin for the self-etching primers, and when the one-bottle ad-hesives were used in combination with the total-etch technique.
Conciusion: Self-etching primers improve the marginal adaptation of oompomer restorations in enamei.
} AOhesive Dent 1999,1:143-151 Submitter] for pubiication: 16.02.99; accepted for publication: 23.02.99
Sihce glass-ionomer cements were introduced in1969, they have been continuously modified.
While glass-ionomer materials harden by an acid-base reaction,22 the resin-modified glass iono-mers^^ include an additional polymerization reac-tion. This results in more favorable working charac-teristics, such as prolonged application time, andimproved properties, such as reduced sensitivity toearly water contamination. The more recently devel-oped "compomers" are polyacid-modified resincomposites,i8 and were introduced to the dentalprofession as a restorative material which com-
' Professor Associate, Dept of Operative Dentisfry. Preventive Den-tistry, ana Endodontics, School of Dental Medicine, Hurnbolót Uni-versity Berlin (Charité), Germany.
" Professor, Dept. of Operative Dentistry, Preventive Dentistry, andEndodontics, School of Dental Medicine, Humtiolút UniversityBerlin (Charité), Germany
Repiint requests; Dr. Uwe BluncK Dspt. of Operative Dentistry, Pre-ventive Dentistry, and Endodontics, School of Dental Medicine, Hum-boldt University Berlin (Charité), Augustenburger Piatz 1, D-13353Berlin, Germany. E-mail: ubtLinck®charite.de
bines the advantages of glass-ionomer cements(fluoride release) and composite resins (wear resis-tance and better esthetics). These materials consistof polyacid-modified dimethacrylate monomers re-inforced with ion-leaching glass particles similar tothose in glass ionomers. Since they contain nowater, the setting reaction can only take place as apolymerization reaction as in composite resins. Un-like glass ionomers, compomers cannot establish abond to tooth structure by themselves, and there-fore have to be placed in combination with an adhe-sive system.^'^
The kinetics of polymerization and the lowerYoung's modulus of elasticity of compomers'^'^^ arethe reason for reduced polymerization shrinkagestress during the setting reaction of compomers.Therefore, in comparison to composite resins, onlyreduoed forces interfere with the bonding capacityof the adhesive to enamel and dentin when com-pomers are used. Several ¡n vivo studies haveshown that the application of one-bottle adhesiveswithout acid-etching enamel and dentin is effective
Voi 1, No 2 . 1 9 9 9 143
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Tabie i List of evaiuated adhesive/ restorative materiai combinations
Gtou
1
2
3
4
5
6
7
8
g
10
Dentin adhesive
Rasant
Prime & Bond 2.1
Ptime&Bcnd 2.1
Syntac SC
ESPE OSB
Prompt L" Pop
Prompt L'Pop
Primes Bond 2.1-1- total-etch tech.
Prime & Bond 2.1+ total-etch teoh.
ESPE EBS
* total-etch tech.
Batch Number
CM002
# 9805000697
2001-05
# 98050006972001-05
Compomer
F 2000
Dyract AP
Dyract
# 926758: 1999-12 Compoglass F
#002 /1998-07
#001:07/98
# 001:07/98
« 98050006972001-05
# 98050006972001-05
#159/1998-07
Hytac
H/tac
Dyract AP
Dyract AP
Dytact
Hytac
Batch Number
CMOOl
# 98030001132000-02
# 97100011262000-06
# 909420: 2000-07
#004/1998-11
# FW 00444721999-10
# 98030001132000-02
# 98030001132000-02
# 97100011262000-06
#004/1998-11
Tabie 2 Criteria for the marginai examination in the SEiVI at a magnifi-cation of 200 X
Margin quality Defihition
1 Margin not or hardly visibie, no ot slight marginal irreguiatities; no gap
2 No gap but sevete marginai irregularities
3 Gap visibie (hairline crack up to 2 um): no marginal irregularities
4 Severe gap (more than 2 pm); slight and sevete marginal irregularities
Tlie term "margiral irregularities" means: porosities, marginal restotstion fracture, bulge ir tiie restora-
in providing acceptable marginal adaptatJoti ofoompomer restorations.2."̂ .i5,i6,20 However, it hasbeen proven in vitro that etching the enamel signifi-cantly increases the shear bond strength of com-pomers.^'^Û'I^'^" New developments of adhesivesystems which combine the abilities to conditionand prime both enamei and dentin in one liquidseem to further simpiify the application technique,
Simpiified appiication—ie, without acid-etchingthe cavity walls first—is one important advantage ofcompomers over ccmposite resins.
The purpose of this in vitro study was to deter-mine the marginal adaptation of different adhe-sives inciuding recently developed self-etchingprimers in combination with compomers in Class Vcavities.
IVIATERIALS AND IVIETHODS
For this study, 80 extracted caries-free human max-illary incisors were stored in a 0.1 % thymol solu-
144 TheJournal of Adhesive Dentistry
tien. The teeth were numbered from 1 to SO andrandomiy assigned to 10 groups. The Ciass V cavi-ties were prepared with a diamond bur (No. 837KR,314; Gebr. Brasseler GmbH, Lemgo, Germany)at high speed (80,000 rpm) using water spray as acoolant. The ovai preparation was approximately1.5 mm deep, 3.0 mm wide, and 4,0 mm high, Haifofthe preparation was situated apical to the ce-mento-enamel junct ion. The margins in enameiwere finished (No. 8838/314/012; Gebr. BrasselerGmbH) without beveling, and the cavosurfaoe mar-gins in dentin were prepared to a 90" angle.
The cavities were filled with compomer in combi-nation with different adhesives (Table 1), In threegroups, enamel and dentin were etched prior to theappiication of the adhesive. The adhesive systems(Table 1] were applied according to the manufac-turer's instructions. The oompomers were placed intwo increments starting at the cervicai margins.Each increment was light oured (Heliolux GT, Viva-dent Dentai GmbH, Eiiwangen, Germany) for 60 s.
After polishing (Sof-Lex Pop-on No, 1981 SF/F/M3M Medica GmbH, Borken, Germany), the teethwere stored in water for 21 days and then thermo-cycled for 2000 cycies between +5°C and +55°C,Before and after the thermocyciing procedure, im-pressions were taken with a poiyvinyl siioxaneimpression material (Silagum light body; DMG,Hamburg, Germany), Repiicas were produced bycasting the impressions with an epoxy resin (Sty-cast 1266 Part A + B; Emerson and Cumming,Westeric, Belgium) and gold-sputtering the surface(SCD030; Balzers Union, Baizers, Liechtenstein).
The margins of the restorations were examinedand quantified with a scanning eiectron microscope(AMRAY 1810, Bedford, MA, USA) ata magnificationof 200x using defined criteria (Tabie 2), The teethwere evaluated in numerical sequence, in order toprevent disclosing their group assignment to the ex-aminer. The marginal quality criteria were summa-rized as percent of the total margin iength, givenseparately for enamei and dentin in each cavity.The statisticai analysis was performed with theKruskal-Wallis test and Bonferroni adjustment usingthe SPSS statistical software.
RESULTS
The results (Table 3) are summarized for the mar-ginal quaiities "continuous margin" and 'marginaiopenings" in Figures 1 to 4 as boxpiots, giving the
. Blunck/Roulet
percent of the entire margin length in dentin orenamei after thermocyciing.
The "continuous margin" results in dentin afterthermocyciing show the highest percentages for thegroups using Rasant/ F2000 and Prompt L 'Pop/Dyract AP (Fig 1), The median vaiues of 100% forthese two groups were significantly higher thanthose of the group using Prime & Bond 2,1 / Dyractand ESPE OSB / Hytac, The total-etch technique in-creased the percent of continuous margins in den-tin significantly when Prime & Bond 2,1 was used incombination with Dyract. The proportion of mar-ginal openings corresponds to these resuits. Thegroups using Rasant or Prompt L'Pop, as weil asthose groups in which the totai-etch technique wasaiso used, showed the icwest proportion of mar-ginai openings (Fig 2), Again, acid-etching thedentin improved the marginal adaptation, as shownby a significantly smaller proportion of gaps in thegroups using Prime & Bond 2,1,
The resuits regarding the marginal adaptation inenamel show better margins (Fig 3) for the groupsusing either the acid-etching technique or the seif-etching primer systems Rasant or Prompt L'Pop.Only when Prompt L'Pop was used in combinationwith Dyract AP the proportion of "continuous mar-gins" was statisticaiiy significantly (p < 0.05) higherin comparison to the group using Hytac as a resto-rative material. However, this ccuid not be found forthe proportion of "marginai openings" (Fig 4),where no statisticaiiy significant difference could befound. In aii groups using Prime & Bond 2.1, SyntacSC, and ESPE OSB without enamel etching, mar-ginal openings were much more frequent.
DISCUSSION
The method this study empioyed to evaiuate the ef-ficiency of dentin adhesives has been used suc-cessfully for years,^-^'^'^^ The sampies were storedin water for 3 weeks in order to avoid changing themarginai adaptation due to water sorption by therestorative materiai during thermocyciing. Compos-ite resins, resin-modified giass ionomers, and poly-acid-modified composite resins show the highestamount of water sorption within the first 14 days,2iAfter this time, the effect of water sorption on mar-ginal adaptation should be minimized. The thermalstress to which the fiiiings were exposed leads todebonding at the interface whenever the dentinbond strength is too low to withstand poiymeriza-
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Table 3 Results (median and mean) for the different groups tested inthe margin analysis of enamel and dentin
bond strength is too low to withstand poiymeriza-tion stress and/or thermocyoling, it was not the in-tent of this study to investigate tiie effect oflong-term water storage on the hydroiysis of the ad-hesives.
The results cieariy show the effectiveness of theconditioning primers in achieving better marginaiadaptations. Several investigations came to theconclusion that etching the enamel can signifi-cantiy improve the margina! adaptation of com-pomers to enamel,3.9.io.ii.ii It was found that
etching the enamel increases the shear bondstrength of Prime & Bond 2,1 and Syntac SC incombination with the corresponding compomer. Inclinical studies, however, there was no statisticallysignificant difference amongthe evaiuated marginsin enamel in Class V cavities.2.'.i5,i6,20 practition-ers ocoasionaily find stained margins in enamelwith compomer restorations. The reason is therather rough interface at the margins whenever theenamei margins are not acid-etched.
Vol 1, No 2.1999 147
Blunck/Roulet
Rasant / F2000
Prompt LP / Dyract AP
Prompt LP / Hytac
P&B 2.1 + TAT / Dyract AP
ESPE EBS + TAT/Hytac
P&B 2.1 + TAT / Dyract
Syntac SC / Compoglass
P&B 2.1 / Dyract AP
ESPE OBS / Hytac
P&B 2.1 / Dyract
Fig 1 Amount of "continuous margin " in percent of the entire margin iength in dentin in Class V cavities after thermocyciing(n = 8¡ (o = outliers). Results of groups oonnected by vertical bar are not significantly (p > .05) different. TAT = total-etch technique.
Fig 2 Amount of "marginal openings" in percertt of entire margin length in dentin in Ciass V cavities atter thermocycling (h(0 = outiiersl. Results of groups connected by vertical bar are not significantly (p > .05) different. TAT = totai-etch technique.
148 The Journal of Adhesive Dentistry
Blutiok/Roulet
Prompt LP / Dyract AP
Rasant/F2000
P&B 2.1+TAT/Dyract
ESPE EBS + TAT/Hytac
P&B 2.1 + TAT/Dyract AP
Prompt LP / Hytac
P&B 2.1 / Dyract AP
P&B 2.1 / Dyract
Syntac SC / Compoglass
ESPE OBS/Hytac
20 40 60 80 100%
Fig 3 Amount cf continuous margin" in percent of entire matgin length in enamel in Ciass V cavities after thermocycling (n •(0 = outliers). Results of groups connected by vertical bar are not significantly (p > ,05] different. TAT = total-etch technique.
Prompt LP / Hytac
ESPE EBS + TAT/Hytac
Rasant/F2000
Prompt LP / Dyract AP
P&B 2.1 + TAT / Dyract
P&B 2.1 + TAT/Dyract AP
P&B 2.1 / Dyract AP
P&B 2.1 / Dyract
Syntac SC / Compoglass
ESPE OBS / Hytac
100%
Fig 4 Amount of "marginal openings" in percent of entire margin length m enamel in Class V cavities after thetmocycling (n(0 = outliers¡. Results of groups connected by vesical bar are not significantly (p > .05) different TAT = total-etch techhique.
Vol 1, No 2 , 1 9 9 9149
Fig 5 Margin in enamel of a Class V cavity restored withHytac (SEM, 200X],
Fig 6 Margin in enamel of a Class V cavity restored withDyract AP {SEM, 200X).
Fig 7 Enamel surface after pretreatment with Prompt L 'Popfor 30 s and nnsed with water (SEM, 2000X),
Other studies showed an increase of marginaiopenings at the cervical margins in dentih afteracid-etching the enamei a lone. i ' It was hypothe-sized that the improved bonding to enamei afteretching can puil the material from the weaker bond-ing areas in dentin. In the present study, there waseven a statisticaiiy significant increase of the pro-portion of "continuous margin" when Dyract wasapplied in combination with Prime & Bond 2,1 aftertotai etching. As in an in vivo study,^^ no effect onthe marginal sealing in dentin could be found whenthe enamei was etched aiong with the dentin. Itseems that conditioning the dentin with phosphoricacid improves the bond strength of Prime & Bond2,1, Therefore, whenever the enamel margins are tobe etched, the dentinai cavity wails should be in-cluded as weil.
There is some controversy about the conclusionsfrom the studies evaiuatihg the effect of previousetchingof the cavity walls to improve the margins ofcompomer restorations in enamel. Some autiiorseven recommend using the adhesive systems incombination with compomers only after condition-ing the enamel with aoid.^'^ This, however, is con-trary to the concept behind compomer use. Theywere intended to be a material which could be han-dled as easily as giass ionomers, which meanswithout an adhesive system, and still have the bet-ter properties of a composite resin, such as es-thetic appearance and wear resistance. The use ofa compomer in daiiy practice would be inappropri-ate if the same time-consuming adhesive techniquehad to be performed as for composite resin restora-tions,
Dyraot's monomer system and particle size wereimproved by the manufacturer, yielding Dyract AP,which has a smoother surface. This is the reasonfor the statisticaiiy significantly smaller proportionof "continuous margin" in enamei for the groupusing Prompt L'Pop combined with Hytac in com-parison to Dyract AP, as shown in Figures 5 and 6,
There was no difference between these grcupsregarding marginal openings. This means that theamount of marginai irreguiarities was higher, caus-ed by the rough materiai (see Fig 5),
On the other hand, the conditioning primers, eg,Rasant and Prompt L'Pop, were as effective asPrime & Bond 2.1 in combination with the total-etchtechnique. The acidic primers seem to increase thebond strength to enamel. After rinsing the appliedprimer Prompt L'Pop with water, the SEM shows an
150 The Journal of Adhesive Dentistry
Blunck/Roulet
enamel surface etching pattern (Fig 7) with irregu-larities which facilitate micromechanicai retention.
These favorable results for the acidic primersRasant and Prompt L'Pop must be confirmed inclinical studies. However, the lower polymerizationshrinkage stress of the compomer in combinationwith a self-etching primer seems to improve themarginal adaptation of compomers in enamel with-out extending the adhesive procedure.
CONCLUSION
From this in vitro investigation, it can be concludedthat the seif-etching primers achieve marginaiadaptation of compomer restorations in enamelwhich are comparabie to those of one-bottle adhe-sives after acid-etching the cavity walls. Furtherclinical studies have to investigate whether such atime-saving technique can provide iong-term suc-cess.
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