Restorative

Glass-ionomer cements in John W. Nicholson. PhD*/Theodore P Croll. DDS**

Abstract This anide reviews ihe eurreni sUiHis aiitijiirure prospeclsfor -ionomer malerials. Tliese muieriuls are of ¡wo eheuiicai lypes: ihe older, selfhardeiiing cemeiils. which sei by an uviil-base iieiiii-alLalioii reaeHon to give relalively bri/rle luaierials: and ¡he newer, re.sin-modified cemeiU.s. which se¡partly hy polymerizaiion and panly by neinraUzaiioii. Compared with ¡he self-hardening cements, ¡he lauer materials have improved esthetics, improved resistance to moisture, and greater toughness. Both types qfgla.s.s-ionomer cement bond well ¡o enatnel and and release a clinically useful amount of fluoride. Thev have been used in a variety of applications: as liners or bases, for luting of stainless steel eroiins. for Class V restorations in permanent teeth, and for Class 11 and Class HI restorations in primar}- teeth. The resin-modißcd glass-ionomers are particularly promising for these latter uses, ahhough it is too early to be sure whether ¡heir long-term dnrabilHy is sufficient. Self-hardening glass-ionomer materials are likely to retain specific niches of clinical applicaHon. including in their metal- reinforced and cermet-containing fortns. (Quintessence Int }997;2S:705-7¡4.)

Ë^linical relevance Introduction In recent years, there has been considerable confusion IKS review of the glass-ionomer genre updates the about what type of material should be called a atist about glass-ionomer and polyacid-modified glass-ionomer cement. Strictly, the term should be sin materials, describes their chemistry' and poten- applied only to a material that involves a significant \. and advises the dinician about methods and acid-base reaction as part of its setting reaction, where jionale for their use in restorative and prosthetic the acid is a water-soluble and the base is a islry. special glass.' Other materials, for example those that some manufacturers have marketed as "light-cured glass-ionomers." are essentially resin composites, although they do contain the fluoroaluminosilicate glass of a conventional glass ionomer material. How- ever, these materials lack the characteristic good adhesion of glass ionomer cements, tend to release little fiuoride. and undergo polymerization contrac- tion on setting. ad. Departmem of Dental Biomaterials Science. King's Denial itLlute, Universily of London. London. England A further source of confusion has been the develop- pvate Practice, Pédiatrie Dentjstrj', Doylesloivn. Pennsylvania; ment of materials that set by polymerization but are lical Professor. Departmem ol Pédiatrie Dentistry. University of based on resins modified to include acid functional nsylvania. School ofDental Medieine; Clinical Professor, Cranio- groups on them and also contain basic . These fial Growth and Development (Pcdiatrie Dentiitry), University of as, Health Science Center at Hojston (Dental Branch); Adjunc- materials, such as Dyract (Dentsply), Compoglass ! Assistant Professor, Department of Pédiatrie Dentistry. Univer- (Ivoclar), and Hytac (ESPE), show interesting proper- ( of Iowa. Coliege of Dentistry. ties, and are promising as restoratives, but are ceriainly |lrequEsts; Dr J. W. Nicholson. Dental Biomaterials Department, not glass-ionomer materials. The term compomerh^.^ •Dental Institute. Caldecot Road, London SES9RW, United . E-mail: j. nie hols [email protected]. been applied to them by the manufacturers, but this

11/1997 705 Nicholson/Croll

term has already been incorrectly applied by clinicians greater than the value at 24 hours. The ratio of bound to glass-ionomer-resin hybrid materials that sel sub- to unbound water increases, this being defined as the stantially by an acid-base reaction.--' The term poly- ratio of water that may be removed by chemical acid-iiioüißfd resin coiiiposiie has been recommended desiccation ( eg. by storage for 24 hours over silica gel lor these materials, ' although Ihe word aimpoiner is a at elevated temperature) to water that is retained in the useftil everyday name. Those glass-ionomer malerials cement during this treatment. Finally, translucency that are modified by Che inclusion of resin, generally lo also changes, gradually becoming greater and more make them partly photocurable, are recommended to like natural material as the cement ages.^ be called resin-inodified glass-ionomer materials, the Tlie seiting reactions in glass-ionomer materials are term used here. as follows:

1. Decomposition of the glass under the influence of Se If-h arden ing glass-ionomer materials the aqueous polyacid. leading to the release of Ca^* and Al'* ions. The latter are probably released in Glass-ioQomer materials in their original, self-hardening the form of complex oxyanions containing several form, became available in the last quarter of the 20th aluminum atoms.'* a structure that reflects the form century. They belong to the class of material known as they have occupied within the glass prior to acid acid-base cemeiiis,* and their setting involves neutrali- attack.^ zation of acid groups on a waler-soluble polymer whh a powdered, solid base. The base is a special calcium 2. Rapid reaction of the Cn'* ions with ihe polyacid aluminosilicate glass that also contains tluoride, an chains, followed by slower reaction of Al^"* species important feature, because it causes the cement to gradually released from the anionic complex. This release clinically useful amounts of this ion and thereby reaction displaces water from some of the hydration to prevent the development of secondary caries around sites'" and to some ionic crosslinkitig of the restorations.- The glasses act as bases in the sense that polyacid chains; both effects to insolubiliza- they are proton-acceptors, even though they are not tion of the polymer and stiffening of the material. soluble in water. 3. Gradual hydration of the inorganic fragments As the cements set, water becomes incorporated released in step I, to yield a matrix of increasing into the material, and there is no phase separation. In strength, greater resistance to desiccation, and fact, water has been identified as having a number of improved translucency."'- roles: (!) it is the solvent for the setting reaction, because, without it. the polymeric acid would be Improvements in the strength and durability of unable to exhibit its full properties as an acid. (2) il glass-ionomer cements have been sought by such is one of the reaction products. (3) it acts as both means as the inclusion of finely divided or coordinating species to the metal ions released from of a silver-cermet formed from the glass plus silver ina the glass and as hydrating species at well-defined sites fusion process. Fibers have also been used lo reinforce around the polyanion, and finally (4) it may act as a experimental cements.'-* plasticizer and reduce the rigidity of the bulk poly- A disadvantage of glass-ionomers is that they are meric structure.*' sensitive to moisture in the early stages following , A number of factors are known to influence the placement.^ This may result in either the washing out speed of the setting reaction and the Tmal strength of of reacting ions from the immature cement by saliva or, the cement. These include the mass of the in patients who tend to breathe through the mouth, in , polyacid concentration of the acid solution, the desiccation and arrest of the setting reaction. Both, powder-liquid ratio, and the presence of chelating effects are undesirable, and. to overcome the problems,._ agents, such as (+) - tartaric acid,' which reduces the dentists are advised to cover freshly placed cemenl setting time and increases the compressive strength of with an impervious layer of varnish, petroleum jelly, . the cement once set. or liquid resin bonding agent. ^. Glass-ionomer cements undergo gradual maturation Glass-ionomers are able to form true adhesive processes that are pooriy understood. For example, in bonds to dentin and enamel^ and for this reason have, cements prepared from polyiacrylic acid), compressive found a wider range of applications than other dentai strength gradually rises over the first 3 months or so of cements. These uses are considered in more detail later ;, the cement"s life to a maximum value some magnitude in this article. .

706 Quintessence International Volume 28, Number Nie hol son/Groll

Resin-modified glass-ionomer materials without a lining or a base.-^ -'' although moderate These materials, the majority of which are cured by inflammatory responses in the have been re- visible light, are hybrids that involve the incorporation ported in some human studies,-'-** of polymerizable components into an acid-base glass- The use of certain glass-ionomers extracoronaily, ionomer cement. They were first described in the late however, as luting cements, has been shown to be 1980s.'"* The use of visible light to cure these materials, associated with pulpal hypersensitivity.'^ -"" The par- at least as far as the initial development of structure is ticular cements that cause this are the so-called concerned, limits the depth of individual layers of anhydrous cements, which are formulated by mixing cement that can be used, because of limitations in the glass and polymer powders and activated by the extent to which light can penetrate these materials. addition of the appropriate amount of water. The Typically, this depth is of the order of 2 to 3 mm. a reason that these cements cause pulpal sensitivity was feature which restricts the use of these materials to initially thought to be due to the slow dissolution ofthe certain areas, such as cavity lining or incisai edges. polyacid, which was assumed to maintain the local pH Resin-modified glass-ionomer materials consist ofa at low levels for longer than in conventionally formu- complex mixnire of components,'-' including poly( acrylic lated glass ionomers," However, a study of pH change acid) or a graft-copolymer of poiy(acrylic) in which a in setting cements showed that the anhydrous cements photocurabie side chain has been added; photocurable underwent a slightly more rapid neutralization than monomers, such as hydroxyethyl methacrylate (HEMA); conventional ones and that their setting profile was calcium aluminosilicate glass: and water. These materials almost the same as that of anhydrous polycarbox- set by a number of competing reactions and have ylate. - - No pulpal sensitivity has ever been reported for complex structures. There is evidence of slight swelling this latter material. It thus seems likely that pH is not ofthe cured cement in aqueous media,"^ but. to date, the cause ofthe reported sensitivity. there is only one account of this leading to a Biologic studies have shown that different glass- catastrophic clinical failure, when a tooth filled with an ionomers differ in their ability to develop and sustain a inappropriately formulated material thai underwent marginal seal that excludes bacteria from the region phase separation prior to use was split by the osmotic close to the pulp,-'-'""'^ Moreover, beneath certain pressure in a HEMA-rich cement. '^ In general, how- glass-ionomer restorations, including experimental ever, clinical indications for their use has been crowns luted with this material, bacteria have been promising, and good adaptation"* and adhesion,''' found in an active state of metabolism. Moderate acceptable fluoride release.-" and excellent esthetics,"'-" pulpal infiammation has always been associated with have been reported. The data available to date on them,-'-'"'-'' It thus seems that glass-ionomers are not long-term durability and esthetics will be discussed directly responsible for this adverse pulpal reaction, later in this article. but certain brands, by not forming an adequate seal, are responsible indirectly, because bacteria can be ad- mitted to cause the adverse biologic effects. fiiocompatibillty „•Ji¡J Biocompaiibi/Hyis defined as the ability ofa material to -jjftis perform with an appropriate host response in a Clinical applications ijiJiS specific application.-^ It is thus distinct from inertness. Original glass-ionomer restorative cements did not ^0 which would imply no response from the host. More- receive widespread acceptance by dentists in the early 0'$ over, biocompatibility is not a single phenomenon, but and mid 1980s, particularly in the LJnited States. These ir&t' ^'^^'' ^^ ^ collection of processes involving different materials had low wear resistance, fractured easily, and ,li,fi but interdependent mechanisms of interaction be- required unusuai handling by the dentist to avoid ^^•, Iween a material and the tissue. It is also specific to a overhydration or desiccation during the extended ' ;j particular application and location in the body, initial hardening time. Regardless ofthe benefits of ' Glass-ionomer cements are generally biocompatible fluoride ion release and uptake by adjacent enamel and ¿with oral tissues and. as restorative materials, result in dentin, chemical bonding, and favorable thermal ",.

Quintessence Intprnatinnai \in -'•-•• '1997 707 Nicholson/Croll

Fig 1 Sliver (mesial fossa) and silver-cermet Fjg 2 "interim" silver-cermet restoration of maxillary firsi resloralions oí a primary second molar, 8.5 years after molar, 9 years after placement. placement.

Glass-ionomcr luting cements, however, were more originally as liner/base materials feg. Baseline VLC, successful. They are used for cementing stainless steel Dcntsply/Caulk; Vitrebond, 3M Dental), they are now crowns for primary teeth, precision casi crowns and available as restorative cemenis. Current commercial fixed prostheses for permanent teeth, space main- materials for this latter application include Fuji II LC tainers. and single orlhodontic bands. Dentists treat- (GO, Photac-Fil (ESPE), and Vitremer Tri-Cure ing caries-prone patients are particularly pleased with ( 3M Dental ), all of which have been useful for Class II a luting cement that has leachable fluoride ions and andClassV restorations in primary (Figs 3a to 3c) and associated preventive dentistry implications. Glass- permanent (Figs 4a and 4b) teeth. For Class ! ionomer luting cements of all types have become quite restorations of primarj' molars intended to last more popular, and their use continues to increase. than 3 years, initial clinical observation is that Vitrenier Introduction of the glass-ionomer-silver-cermet, Tri-Cure appears to have the besi durability. One Ketac-Silver (ESPE), in 19S4 gave dentists an attrac- author (TPC) has now had more than 5 years' tive alternative to silver amalgam for Class I restoration experience using these materials for the repair of of primary' teeth.•"'"•^'' Although fracture strengths primary teeth and confidently states that the resiti- remained too low for the material to replace cusps or modified glass-ionomer cements will become a main- marginal ridges. Ketac-Silvcr made a large impact on stay restorative material for pédiatrie dentistry'*'"^" restorative dentistry for children (Fig 1 ). A surprising (Fig 5). development was that Class I silver-cermet restora- Having been found to be satisfactory in the primary tions, originally placed for "interim" use in permanent dentition, resin-modified glass-ionomers are now being teeth,""'have routinely lasted for 10 years or more (Fig used to restore permanent teeth-'-' (Figs 4, 6, and 7). 2). Ketiic-Silver has also been used for "lunneP res- However, brand selection and material handling are torations."""'^ other restorations using unconventional important (Fig 8). VitremerTri-Cure restorative cement, preparations conserving of tooth structure,"'''"'"' as an mixed at high powder-liquid ratio so that all of the endodontic filling materiai. and to serve as a core powder is wetted during mixing, appears to perform buildup material prior to complete- preparation. the best on the occiusal surfaces of permanent teeth. More recently ihe profession has seen the develop- This may be the result of the high powder-liquid ratio, ment of resin-modified glass-ionomer materials. These or it may be that Vitremer Tri Cure has better wear combine advantages of glass-ionomer systems and resistance, is less soluble, or both. All three brands of visible light-polymerized resin technology and are a resin-modified glass-ionomer material perform well in significant development in restorative dentistry. The Class III and Class V restorations, in many cases set cement has the main advantages of conventional holding up well for more than 4 years in permanent glass-ionomers, ie. fluoride release and adhesion to leeth. dentin and enamel, but also improved fracture re- The use of self-hardening resin-modified glass- sistance and better wear characteristics. Introduced ionomer luting cements is growing rapidly. These

708 Quintessence International Volume 28, Number Nicholson/Croll

Fig 3a Sixteen-month-old cfiild with severe lingual caries Fig 3b Caries debnded wilh an inverted cone bur, used in of the maxillary primary incisors. a slow-speed handpiece.

Fig 3c Resin-modified glass-ionomer restorations, 26 Fig 4a Sensitive decalcitication/carious lesion asso- months after placement. ciated with poor oral hygiene during orlhodontic

Fig 4b Resin-modified glass-ionomer cement restoration. Fig 5 Four-year postoperative view ct primary second ; 1 yearpostoperatiuely. molar (mesio-occlusohngual) restoration; primary first molar (disto-occlusal) restoration. (Vitremer Tri-Cure Resforative Cement).

Quinte 709 Nicholson/Croll

Fig 6a Occlusal and occlusolingual carious lesions ot ihe Fig 6b Initial outline form cut with water-cooled high- maxillary permanenl first molar in a caries-prone child. speed bur, followed by complete debrjdement ot carious substance

Fig 6c VJtremer Tri-Cure Restorative Cement mixed with Fig 6d Excess cement purposely left over the cavo- high powder-liquid ratio and syringe injected into the cavity surface margins acts as an adhesive sealant preparation.

Fig 6e Enamel and cemenf surfaces, etched, rinsed, Fig 6f Resforation 17 months after placement. dried, and coated with unfilled resin sealant.

710 Quintessence International Volume 28, Number Nicholson/Croll

Fig 7 Class I resJn-moditied glass-ionomer restoration 34 Fig 8 Failure ot a Class I resin-modified glass-ionomer months after placement restoration as a result of incorporation of air bubbles during syringing, degradation of the material, and, perhaps, brand of maferial.

Fig 9 Excess resin-mod i tied glass-ionomer luling cemenl Fig 10 Resin-modified glass-ionomer luting cement used exuding at the margins during placemeni of a stainless steel for a band and soldered wire loop space mainfainer crown

materials are not light-activated but contain the pédiatrie dentistry, these luting cements are becoming necessary monomers to undergo polymerization, to- the material of choice for stainless steel crowns {Fig gether with initiators of the same type as used in 9). space maintainers (Fig 10), and individual orth- cold-cure acrylics, eg. bcnzoyi peroxide and amine odontic bands. Band cementation can also be carried accelerator. The commercial materials of this type are out with light-curable resin-modified glass-ionomer Advance (Dentsply/Caulk), Fuji Pius (GC; originally cements where the radiant light is transmitted through called Fuji Duet) and Vitremer Luting ( 3M Dental ).^' the tooth to bring about the polymerization part of the These cements are easily handled, cause no significant curing process."" postcementation sensitivity when luted to dentinal surfaces, and have significant fluoride release and high «impressive and fracture strengths. A report pub- iished in February 1996 confirmed these observalions The future and predicted that the resin-modified glass-ionomer What does the future hoid for the clinical use of 'uling cement wiil soon dominate the market for glass-ionomer systems? Clearly, the new resin-modified routine crown and fixed prosthetic ce menta tion. •^"' In malerials will have a major role to play. Although it is

Quintessence Inipmalii 711 Nicholson/Crall

too early to be sure ofthe long-term durability and compressive strength, radiopacity, and excellent clini- reliability of these materials, some predictions can be cal wear.^' Materials ofthis type currently on the market made. If they prove to have adequate wear resistance include Miracle Mix (GC) and Hi-Dense (Shofti). and fracture strengths so that a Class II restoration in a Also wilhin the dental field, se If-hardening glass- primary molar can survive for 6 to ÍÍ years, they will ionomers have been used in bone contact applications. replace silver amalgam for the treatment of such teeth. In particular, this has involved their use in augmenta- The logic of this becomes even more compelling tion ofthe alveolar ridge in edentulous patients.^^'^^ considering that resin composite can be used in Such studies have shown thai glass-ionomer materials cosmetically prominent teeth and stainless steel crown form intimate bioactive bonds with bone cells and restorations are available for severely involved primary become fully integrated into the bone. It is an excellent molars and canine teeth. The history of glass-ionomer- material for this application and performs better than, silver-cermet restorations over the past 10 years also for example, hydroxyapatite, which has been used to lends credence to predictions of an optimistic future date for this purpose. Self-harden ing glass-ionomers for resin-modified glass-ionomer materials, given their have also been used in maxillofacial and craniofacial better physical properties and handling characteristics. reconstruction surgery.''"''' The technique involves the Resin-modified glass-ionomer luling cements give fabrication of custom-made preset implants, cured every indication of becoming the materials of choice outside the body to develop their full mechanical for cementation of stainless steel crowns, space strength, and then cemented into place with a self- maintainers, and individual orthodontic bands. This curing glass-ionomer cement. The material has excel- could also be true for cementation of precision cast lent biocompatibility, and early applications of this crowns and fixed prostheses to prepared permanent technique have been encouraging. teeth. Although more long-term data are needed concerning resin-modified glass-ionomers, they show remarkable promise for materials at such an early stage Conclusion in their development. Overall, glass-ionomer cements, both self-hardened With all this development on the resin-modified and resin-modified, are important materials for modem glass-ionomers, it might be tempting to conclude that clinical dentistry and will remain so for years to come. the original self-hardening glass-ionomer cements are The development of rcsin-modifled materials has obsolete. However, this is far from the case. These opened up new dimensions in restorative dentistry, materials, too, are undergoing exciting developments while the development of metal-reinforced and rapid- of their own. For example, new restorative-grade setting self-hardening cements has enhanced the materials have been launched recently, such as Ketac- properties and extended the usefulness of the well- Molar (ESPE) and Euji IX( GC), which set only by a established original materials. Glass-ionomers of all conventional neutralization reaction but have proper- types continue to combine fiuoride release, adhesion, ties that rival or exceed those of the resin-modilied good marginal seal, and reasonable esthetics.^^ No systems. Setting is rapid, early moisture sensitivity is material is perfect, but. with the current level of considerably reduced, and solubility in oral fiuids is intensive research on glass-ionomers. the deficiencies very low.-"**" These results have been obtained by that exist seem certain to be eliminated, or at least altering the particle size and particle size distribution reduced, resulting in an ever-improving range of ofthe glass powder, so that setting occurs more rapidly materials ofthis type. than in the older formulations. These developments seem likely to be of particular importance in Third World countries, where there is an alarming growth in the incidence of dental caries but where, because supplies of electricity are sparse or nonexistent, sophisticated dental facilities, such as power hand- References pieces and dental curing lamps, cannot be relied on.^^ 1. McLean JW, Nicholson JW, Wilson AD. Suggested nomendalurefol" glass.ionomer cements and related malerials |eili[orial|. Quinles- Another subgroup ofthe self-hardening systems is sencelnl I994;15:S87-SS9. 2. Mjor I. Marketing vs responsibility, and more I letterl. Quintessence that involving the inclusion of silver metal particles Int 1995:26:665-666, (as opposed to silver fused with glass as a cermet), a 3. Walson TF, Bartlctt DW! Adhesive systems, composites, dentine strategy that gives cements of good properties, ie. high bonding agents and glass-ionomers. Br Dent J 1994; 176:227-231.

712 Quintessence International Volume 28, Number ti/1997 Nicholson/Croll

4. Wilson AD. Nk-holsoii JW. Acitl-Basc Cemtnli; Their Biamedic.ii ChrisicnsenG Glassionomerasa lutingmalcrial. J Am Dent Assoc and [ndiistrial AppliciUions. Ciimbridse, Siiglaiitl: C'anihrid¡;i; 1990:120:62-69, Univeraily Press. 199,1. Johnson GH, Powell LV, Dcroven TV: Evaluation iind control of 5. Swaitï ML, Phillips RW, C\aik H E. Long-lenii Hiioride relejse l"rom post cementation pulpal sensitivity, J Am Denl Assoc 1993-124 39- glass icinomer t-emems. J Denl Res l984i6,l:15S-IhO 46.

6. Nicholson JW. Polyeleclrolslü niiiLerials: Reflceliunh iin a hijitily Smith DC, Rtise ND, Acidity of glass ionomer cements during chacged (opjc. Chem Soc Rev I994;2J:53-5IÍ. setting and its relation to puip sensitivity, J Am Dent Assoc l9S6;ll2:654-657. 7. Wilson AD, McLean JW. Glas5.|nnomer Cornent. Chicago: QiJint- essence, t988. Wassou EA, Nicholson JW. Change in pH during setting of 8. Wasson EA, NicholsiinJW. A sludy of the relationsliip bemeen Ihc polyelectrolyte detital cements. J Dent I993;21:122-126, setting chemistry Jiid properties of modified glass polyalkenoiite Tobias RS, Plant CG, Rippin JW, Browne RM. Pulpal response ti> an cemenis. Br Polym J I99O;23; 179-ISÍ. anhydrous glass-ionomer luting cement, Endod Dent Traumatol 9. Hill RG, Wilson AD. Some structural aspects of g lasse 5 used in ionomer cements. Glass Technol I98S;?9:15O-1SS. 34. PameijerCH, Stanley HR.Biocompatibilityofa glass ionomer luting agent in primates. Part I. AmJ Dent l9!i8;h7l-75, 10. Ikegami A. ImaiN. Preeipilalion of polyeleclrolyles by sails. J Polym Sei t962;56:l3.1-15i. 35 Plant CG, Tobias RS, Rippin .rW, Brooks JW, Browne RM. A study of the relationship among pulpal response, mierobial leakage and it. MalsuyaS, Maeda T, Ohta M. IR and NMR analyses of hardening particle heterogeneity in a glass-ionomer base material. Dent Mater and maturation ofglass ionomer cement J Dem Res 1996;75:192II- 1927, McLean JW, Gasser O. Glass-cermet cements. Quintessence lut 12. WasEon E.^, Nicholson JW. New aspecls of the setting of glass- [985:i6:333-34.î. Lononier cements. J Dem Res 199J;72:481-48,1. MeLeanJW, Gasser O. Powdered dental material and process for the 13 OldHeld CWB, Ellis B. Fibrous reinforeemenl of glass.ionomer preparation thereof. US patent 4,527,979, 1985. cements. Clin Mater 1993;7;."il.l-J22. Croll TP, Phillips RW. Glass ionomer-siiver cermet restorations for H. Miira SB Eut Patent applieation. Ü.i:."!|20A2, 1989; Antonucci primarj'teeth. Quintessence int 1985; 17:607-615. JM, MeKjnneyJE. StansburyJW. US Patent application. 160,856. 19ÜS. Croll TP, Phillips RW, Six years' ciperience with glass-ionomer- silver cermet Quintessence Int 1991:22:783-793, t5. Anstice HM. Recent developments in restorative dental materials. Chem Ind (London) 1994;899-9U2. Croll TP, iCillian CM. G lass-ionomer-siiver cermet interim Class i restorations for perniiinent teeth. Quintessence Int iy92:2J:731-73J. 16. AnstieeHM. Nicholson JW, Studies on the structure of ligbt-cured glass ionomer eements. J Mater Sei Mater Med 1992;."t:447-45l, Knight GM. The use of adhesive matenals in conservative restora- tion of selected posterior teeth. Aunt Dent J 1984:29:324-331, 17. Nicholson JW, Anstice HM, Light eurable glass-iunomer cemenib for dentistr>'. Trends Polym Sei l994;2:272-275. Hunt PR, A modiried Class i i cavity preparation for glass-ionomer restorative materials. Quintessence int I9S4; 15:1011-1018. 18. Waison TF. A confocal microscopic study of some factors afiecLing the adaptation of a light-cured glass ionomer to tooth tissue J Dent Baratieri LN, et al. The tunnel preparation and restoration. In: Res 1990:69:15.11-1538. Baratieri, et al (eds), Advaneed Operative Dentistry, ed 2. Sao Paulo: Quintessence. 1993:295-312. 19. Mitra SB. Adhesion to dentin and physical properties of a light-cured glass ionomer liner/base. J Dent Res 1991;7O:72-74. Mount GJ. An Atlas of G lass-ionomer Cements, ed 2. London: Martin Dunitz, 1994:99-122. 20. Forss H. Release of fluoride and other elements from light cured glass-ionomers in neutral and acidic conditions. J Dent Res Hunt PR. Micro conservative restorations fur approximal carious t993;72:l257-1262, lesion:i, J Am Dent Assoc 1990:120:37-40

11. Croli TP, Killian CM. Restoration of Class It carious lesions in Croli TP Lateral access Ciass Ii restoration using res in-mod i Fied primaiy molars using light-hardening glass-ionomer-re s in cements. glass-ionomer nr silver-cermet cement. Quintessence int 1995: Quintessence [nt l99J;24:56l-369. 26:121-126 32, Croll TP, Light-hardened Class I glass-ionomer-resin cement Croll TP, Killian CM Visible i ig ht-hardened g lass-ionomer-resin restoration of a permanent molar. Quintessence Int I993;24:iO9- cement restorations for primary teeth: New developments. Quintes- 113, sence Int 1992:23:679-682.

23, Williams DF. DeH in Biomatcrials, Amslerda Croll TP, Killian CM, Glass-ionomer-resin restoration of primary 1987. molars with adjacent Class ii tarious lesions Quintessence int 34, Plant CO. Knibbs PJ, Tobias RS, Britton AS, Rippin JW. Pulpai 1992:24 723-717. response loa glass-ionomer luting cement. Br Dent J (988:165:54- Croii TP, iiillian CM, Hclpin ML, A restoraU\e dentistry renais- 58. sance for children: Light-hardened glass ionomer/resin cement, J 25. McLean JW.Aiternatives to amalgam. Br Dent J iyS4:i57:432-4."tJ. Dent Child 1993,60 89-94.

26. Feilon DA. Cox CF, Odom M, Kanoy BE. Pulpal response to Croll TP. Restorative dentistry for preschool children. Dem Clin chemically cured and expérimentai light-eured glass-ionomer cavity Nonh Am 1995:.19:737-770. Lners. J Pmsthet Dent 1991;65:7O4-7I2. Croll TP, Kilhan CM. Class i and Class ii Ugh [.hardened glass -' Cooper i R. The response of the human dental pulp to glas 5-iono mer lonomer/resin restorations. Compend Contin Educ Dent 1993; 14-908-918. cements. Int Endod J 1980.13:76-88, Croll TP, Cavanaugh RR. Vitremer cement for Class i restoration of Í8, Plani CG, Broï^ne RM, Knibbi PJ, Bntton AS, Sorahen T. Piilpal permanent teeth. Pract Periodont Acsthet Dent 1994:6:25-34. effects of glass ionomer cements, int Endod J i984;17:5l-59.

713 Njcholscn/Croll

5.1. Glass ionDmec-resin cements (G[-R). Clin Rts Assot Newsletter SK, Bronk IM, Craig GT. Lamb DJ. Initial in vivo evaluation of 1995:191 Mar);l-2. glass-ionoiner ccmcnls for use as alveolar bone substitutes. Clin Maler 1991 ;7:295-.!nn. 54. Cemenl for fixed prosthodomiL-s-upJjIc '96. Clin Res ASSUL Newslellcr l996;20(Feb); I-?. 59. Brijuk IM. Craig GT, Lamb DJ. In viLro inleraetions between pri- mary bone organ culiures. glass-lonomtr cemenis and hydroxyapatile/ 55. Croll TP, Helpin ML. Space mainlainer cemcnlalion using IL|3|U- LritaluLum phosphate ceramius. Biomalerials I99t;l2:l79-INfi. hardenecl glass in no me r/resin reslomtivc cemenl J Denl Cliilil M). Helm!. J. Geyer G. kinomcr based bone subsliliite in otologic 56. Moiinl GJ. Glass ionomcr cemenls and future research. Am J Dcnl surgery, tjr Arch Olorbinolaryngol l993i25O:25J-256. 61. Geyer G. Hetms J. Reconilruclion of Ihe posterior audilory canal 57. Wasson EA. Metal reinforced gtass-ionomer cemeni: A review üf wall and oblileraticn of ihe maslojd cavity using glass-ionomer prcip^nies ;ind L-linicül jse. Clin M;iler 199.1; I !• lit I-190 temenl. Transplants and Implants in Olology I49hl U165-I70. D

Coming in January 1998

Q] CONTINUING EDUCATION

Beginning in 1998, Ql subscribers can earn 4 hours of CE credit per issue—or up to 48 hours per year!

It's easy:

1. Read the four articles in each issue designated as CE resources. 2. Answer the 16 questions (4 per article) on the answer sheet provided. 1^. Return the answer sheet to Quintessence with a $10 processing fee.

A certificate for 4 hours of CE credit will be sent to those who score at least 75%.

Credit is awarded by Baylor College of Deniistry—The Texas A&M University System. Baylor College of Dentistry is an ADA CERP Recognized Provider, is designated as a nationally approved sponsor by tbe Academy of General Dentistry, and has received provisional accreditation as a continuing education provider by the Accreditation Council for Continuing Dental Education.

714 Quintessence International Volume 28, Number 11/199'