Operative Dentistry Composite resin and glass-ionomer cement: cnrrent status for use in cervical restorations William W. Brackett* / P. Brett Robinson** A review of recent developments in the use of tooth-colored materials for restoration of cervical lesions is presented. White glass-iononter cement restorations in this area cur- rently offer the best prognosis, an improved prognosis for composite resin restorations may result from improved dentinal adhesives and through use of gla.ss-ionomer cement bases or liners. (Qui tit essence Int 1990:21:445-447.) Introducrïon Composite resin or glass-ionomer cement restorations of cervical erosion or caries have considerable cos- metic advantage over metallic restorations. The adhe- sion to tooth structure developed by these materials also allows restoration of cervtcal lesions using little or no cavity preparation. Although resin and glass- ionomer cement materials have long been used for cetrvical restorations, new materials and techniques have been introduced, including use of the two tna- terials in combination. This article will review recent developments in this area. Composite resin Resin-based restorative materials closely match tooth enamel and provide excellent cosmetie results in the cervical area. Through the use of enamel beveling and acid etching, strong micromechanical bonding to en- amel that is highly resistant to leakage can be achieved.''^Such bonding is sufficient to retain the ma- jority of resin restorations in nonretentive cervical cav- ities. A well-recognized disadvantage of traditional Assislant Professor, Restoralive and Prosthelic Dentistry, Ohio State University, College of Dentistry, 305 West 12th Avenue, Cûliitnbus, Ohio 43210. Senior Lecturer, Conservative Dentistry. King's College Hos- pital Dental School, Denmark Hill, London SE5 9RW, England. resin systems is the lack of adhesion to dentin, which increases the risk of leakage and secondary caries along the gingival margin of cervical restorations.'"* In the early 1980s, dentinal bonding agents, based on phosphonate-esters of resin, were introduced. Adhesion to dentin oeeurs through polar interaction between the phosphate groups in these bonding agents and the calcium in the tooih structure. In vitro studies dernonstrate this adhesion,* along with reduced leak- age along dentinal margins.- However, this adhesion apparently deteriorates over time in a wet environ- tnent,^ possibly through hydrolysts ofthe ester hnkage. This observation is generally confirmed by clinical studies using phosphonate-ester dentinal bonding agents in the restoration of nonretenttve erosive le- sions. In the absence of acid etching, these bonding agents provide relatively poor retention of restora- tions, while discoloration along dentinal margins is a frequent observation whether the enamel is etched or not.** New denlinal bonding agents have recently become available. Most of these are based on apphcation to the dentin of a primer containing hydrophilic tnon- omers in aqueous solution with organic acids or al- dehydes, followed by a layer of hydrophilic monomer. An alternative system employs an alurninuni oxalate/ n-phenylglycine pritner. Compared to previous sys- tems, adhesion to dentin with these agents is stronger and less susceptible to deterioration,'' and produces irnproved restoration tnargins in vitro.''"*Clinical data for these systems are generally lacking, but a glutar- aldehyde/hydroxyethylmethacrylate system (Gluma Bond, Bayer Dental) has demonstrated retention of restorations in unetched erosion lesions superior to that achieved by phosphonate-ester systems."'' Regardless of the bonding system etnployed in the nber 6/1990 445
Transcript
Operative Dentistry
Composite resin and glass-ionomer cement: cnrrent status for use incervical restorationsWilliam W. Brackett* / P. Brett Robinson**
A review of recent developments in the use of tooth-colored materials for restoration ofcervical lesions is presented. White glass-iononter cement restorations in this area cur-rently offer the best prognosis, an improved prognosis for composite resin restorationsmay result from improved dentinal adhesives and through use of gla.ss-ionomer cementbases or liners. (Qui tit essence Int 1990:21:445-447.)
Introducrïon
Composite resin or glass-ionomer cement restorationsof cervical erosion or caries have considerable cos-metic advantage over metallic restorations. The adhe-sion to tooth structure developed by these materialsalso allows restoration of cervtcal lesions using littleor no cavity preparation. Although resin and glass-ionomer cement materials have long been used forcetrvical restorations, new materials and techniqueshave been introduced, including use of the two tna-terials in combination. This article will review recentdevelopments in this area.
Composite resin
Resin-based restorative materials closely match toothenamel and provide excellent cosmetie results in thecervical area. Through the use of enamel beveling andacid etching, strong micromechanical bonding to en-amel that is highly resistant to leakage can beachieved.''^Such bonding is sufficient to retain the ma-jority of resin restorations in nonretentive cervical cav-ities. A well-recognized disadvantage of traditional
Assislant Professor, Restoralive and Prosthelic Dentistry, OhioState University, College of Dentistry, 305 West 12th Avenue,Cûliitnbus, Ohio 43210.Senior Lecturer, Conservative Dentistry. King's College Hos-pital Dental School, Denmark Hill, London SE5 9RW, England.
resin systems is the lack of adhesion to dentin, whichincreases the risk of leakage and secondary cariesalong the gingival margin of cervical restorations.'"*
In the early 1980s, dentinal bonding agents, basedon phosphonate-esters of resin, were introduced.Adhesion to dentin oeeurs through polar interactionbetween the phosphate groups in these bonding agentsand the calcium in the tooih structure. In vitro studiesdernonstrate this adhesion,* along with reduced leak-age along dentinal margins.- However, this adhesionapparently deteriorates over time in a wet environ-tnent,̂ possibly through hydrolysts ofthe ester hnkage.
This observation is generally confirmed by clinicalstudies using phosphonate-ester dentinal bondingagents in the restoration of nonretenttve erosive le-sions. In the absence of acid etching, these bondingagents provide relatively poor retention of restora-tions, while discoloration along dentinal margins is afrequent observation whether the enamel is etched ornot.**
New denlinal bonding agents have recently becomeavailable. Most of these are based on apphcation tothe dentin of a primer containing hydrophilic tnon-omers in aqueous solution with organic acids or al-dehydes, followed by a layer of hydrophilic monomer.An alternative system employs an alurninuni oxalate/n-phenylglycine pritner. Compared to previous sys-tems, adhesion to dentin with these agents is strongerand less susceptible to deterioration,'' and producesirnproved restoration tnargins in vitro.''"*Clinical datafor these systems are generally lacking, but a glutar-aldehyde/hydroxyethylmethacrylate system (GlumaBond, Bayer Dental) has demonstrated retention ofrestorations in unetched erosion lesions superior tothat achieved by phosphonate-ester systems."''
Regardless of the bonding system etnployed in the
nber 6/1990 445
Operative Dentistry
restoration of cervical lesions with composite resin,enamel margins should probably be beveled andetched to improve retention. Cliiiicyl sttidies suggestthat the prognosis for retention of resin restorationsin iionunderct]t lesions worsens in Ihe presence ofheavy occlusal stresses, with increasing age of the pa-tient,'-* and when lesions are shallow in axial depth.'"'
Several factors have been demonstrated in viti"O toreduce microleakage of cervical restorations. Fillingcavities by an incremental technique apparently re-duces the deleterious effects of polymerization shrink-age on marginal integrity,'̂ as does the use of resininlays luted with dentinal bonding resin.'*
Delaying the finishing of cervical resin restorationsup to 15 minutes also appears to improve marginalintegrity."as does the use of finishing instruments thatcause minimal damage to resin and to cavity margins.Aluminum oxide disks have been shown to producethe least damage in these areas, followed by ultrafmediamond instruments operated at low rotationalspeeds with water coolant. The use of high rotationalspeeds, carbide burs, or stones appears to damageboth resin material and tooth structure.'^" There isalso evidence that bonding agents should be used withthe resin restorative materials for which they are in-tended.'"
Glass-ionomcr cement
Giass-ionomer cement, introduced to the professionin 1972,-'is tooth-colored and releases fluoride.--Adhe-sion to both enamel and dentin" occurs through polarinteraction between carboxyl groups and tooth struc-ture. These characteristics make the material a viablerestorative materials for nonretentive cervical cavities.
Clinical studies show retention of this material inerosion lesions to be superior to that of resins retainedwith dentinal bonding agents with either etched orunetched enamel."'''"'-'' Retention of glass-ionomercement restorations greater than 90% has heen dem-onstrated after 3 years,-'' while secondary caries hasnot been reported.
While early glass-ionomer cement materials re-quired fmishing at a subsequent appointment, recentmaterials can be finished as soon as 7 minutes aftermixing, according to manufacturer's instructions.Clinical studies supporting these claims are lacking,but the efficacy of finishing one material (Kelac-Fil,ESPE GmbH) 15 minutes after mixing has been doc-umented.-''
Although translucency of these materials has been
continuously improved, and more blindes have beenmade available, current glass-ionomcr cement mate-rials more effectively match dentin than they do en-amel- While most materials must be mixed by hand,Iwo (Ketüc-Fil; Fuji Cap II, GC International) aresupplied in capsules, which are mechanically mixedand become part of an applicator. Other precapsulat-ed materials are expected to become available.
Combined restorations
To compensate for the shortcomings of resins placedin cavities with dentinal margins, a technique has beendescribed in which glass-ionomer cement is placed inthe cavity and etched to allow micromechanical adhe-sion of composite rcsm.-̂ When this technique is em-ployed using a glass-ionomer cement restorative ma-terial, cervical margins may be maintained primarilyas a glass-ionomer cement-dentin interface. Althoughchnical evaluations of such restorations are unavail-able, laboratory studies suggest that the marginal in-tegrity of these layered restoralions is superior to thatof resin restorations,-''
More recently, glass-ionomer lining cements havebecome available for use beneath resin restorations.Because the surface of these materials is roughenedby exposure to air, etching is probably not necessaryfor adhesion of resin."'Laboratory evidence suggeststhat use of these materials does not ehminate micro-leakage of cervical resin restorations.-^ The presenceof a fluoride-releasing liner may reduce the adverseaffects of leakage, although this has not been con-firmed by clinical trials. Because lining cements arerelatively soluble, they should not be used to maintaina restoration margin (McLean JW: Personal com-munication, 1988).
The newest glass-ionomer hning products are ad-mixtures of fluoride-containing glass and light-acti-vated resin. Some of these products are cements thatrequire mixing but acquire early strength through po-lymerization (XR Ionomer, Kerr/Sybron Corp; Vitra-bond, 3M Dental Products Div), while another is asingle-component resin that contains aluminosilicateglass and a phosphonate-ester dentinal bonding sys-lem (TimeLine, LD Caulk Co). These materials offerthe advantage of controlled working time, but chnicaldata on their efficacy are unavailable. Laboratory da-ta suggest that these materials perform similarly toother lining cements beneath cervical resin restora-tions and do not eliminate microleakage {BarkmeierWW: Unpublished data, 1988),
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Clinical considerations
All methods of restoring cervical lesions are highlysusceptible to moisture contamination, because fiuidsdisrupt adhesion. Moisture also inhibits polymeriza-fion and adversely affects the setting reaction of glass-ionomer cement. To exclude contaminants, use of rub-ber dam isolation is indicated. A clinical study inwhieh the rubber dam was not used during restorationof nonretentive cervical lesions found a relatively highincidence of loss and leakage of resin and glass-ionomer cement restorations.-^
Snmmary
Based on clinical data, glass-ionomer cement resto-rations currently offer the lowest incidence of second-ary caries and the best retention in nonundereut cerv-ical cavities. Although more evidence is needed, im-proved dentinal bonding agents and combinationswith glass-ionomer eement probably enhance theprognosis for cervical re.sin restorations. To be suc-cessful, cervical restorations of either material mustbe placed using proper isolation and manipulation.
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