Ketac Molar for ART. Clinical Research 6/97

Transcription

1 Product Dossier

2 Ketac Molar for ART Clinical Research 6/97 1

3 Contents 1. Preface Introduction Atraumatic Restorative Treatment Clinical procedure with the ART technique History of glass ionomers Motivation Indications Chemical Background General overview Chemical background Product Composition Presentation Constituents Test Results Material properties Physico-technical data Abrasion tests Adhesion tests Marginal behaviour Fluoride release In vivo studies on KETAC MOLAR for ART Multi-centre study in China: Clinical study in South Africa Clinical study in Peking Conclusion Literature Clinical studies with KETAC MOLAR for the ART technique Further literature Clinical Research 12/99

4 1. Preface Espe Dental AG played a major role in developing glass ionomers. Pioneering inventions such as KETAC-SILVER, a glass ionomer cement reinforced with sintered particles of silver (McLean, Gasser) were developed by Espe Dental AG through to market launch in collaboration with well-known universities. The glass ionomers developed in the 1960s and 70s have been successfully used in dentistry for about two decades now. This class of material is characterised by easy handling and self-adhesion, even to untreated dentine. Glass ionomers possess a translucency similar to that of ceramic materials. Its biocompatibility is excellent. It is particularly suitable for conservative dentistry but it is also very successfully used for the cementation of indirect restorations. Quite recently so-called heavy-bodied, "packable" glass ionomer cements were developed which are especially indicated as restorative materials for molars and premolars. One of the best known products in this class of material is KETAC MOLAR. The mechanical properties, which are better than those of conventional glass ionomer cements, and its packable consistency make KETAC MOLAR ideal as a restorative material for primary tooth restorations and in the nonoccluded field for cavity class I restorations. Other fields of indication are semipermanent class II restorations and cavity class V restorations. Since the middle of the 1990s this type of glass ionomer has been increasingly used for the so-called ART technique (Atraumatic Restorative Treatment). Clinical studies on this type of therapy testify to the fact that KETAC MOLAR produces excellent results over a period of at least three years. Clinical Research 12/99 1

5 2. Introduction 2.1 Atraumatic Restorative Treatment The ART technique is a method of treatment with the aid of which caries can be treated at an early stage. The aim of ART is to minimise loss of teeth caused by caries. Only hand instruments are used. The ART technique is applied without the need for electricity and without any other elaborate equipment so it can be used anywhere. The method of treatment was presented by the World Health Organization (WHO) for the first time in Areas of application are particularly countries where it is not possible to ensure that the population has a general supply of electricity and modern dental equipment is not available everywhere. However, the ART technique also offers plenty of scope for use in more developed countries, e.g. in treating the first primary teeth when they appear in infants. Glass ionomers such as KETAC MOLAR FOR ART are ideal for use as an ART restorative material on account of their excellent mechanical properties. No other class of material is characterised by less sensitivity to technique or a higher level of biocompatibility. The ART technique already constitutes a form of therapy which has been scientifically investigated in great detail. Clinical studies in Thailand, Zimbabwe and China have demonstrated that particularly in the deciduous teeth excellent results are achieved. In these studies, even after a wearing period of 3 years retention rates of 90% can be observed in class I cavities. Apart from the clinical success rates, patient satisfaction constitutes a further elementary component contributing to the long-term success of the ART technique. In projects conducted in Zimbabwe and Ghana the acceptance of this type of therapy was surveyed among the children treated. It became evident that between 80% and 90% were satisfied both with the treatment and the restoration. As many as 96% of the patients said they were not afraid of undergoing further treatment. This constitutes the basis for a long-term improvement in dental health. Clinical Research 12/99 2

6 2.2 Clinical procedure with the ART technique For the ART technique only a small number of dental instruments are necessary: Hand excavator to remove the caries Mirror for checking purposes Rubber gloves for the "press finger" technique Cotton swab for removing Ketac Conditioner Plastic spatula for mixing Ketac Molar for ART Rotating instruments, water and electricity are not required but, if they are available, they can be used at any time. Children to be treated can, for example, be examined on a table or on their parents' lap. On account of the highly conservative removal of caries with a hand instrument the use of local anaesthetics is unnecessary in most cases. When the caries has been removed, the cavity is conditioned with KETAC MOLAR FOR ART liquid. The conditioning liquid is applied inside the cavity with a cotton swab and removed again after 10 seconds. Then the cavity is filled with the mixed KETAC MOLAR FOR ART. With the so-called "press finger" technique KETAC MOLAR FOR ART is pressed into the cavity. The final modelling of the restoration is performed with a hand instrument. 2.3 History of glass ionomers The glass ionomers developed by Wilson and Kent in 1969 have become an integral part of every dental surgery. Over the years the glass ionomers have been repeatedly modified and enhanced in order to meet the increasing requirements expected of this class of material. Scientific research into glass ionomers pursued two objectives: on the one hand, the aim was to develop an aesthetically attractive material for anterior teeth restorations. The other aim was to improve the material properties in order to expand the fields of application to include anterior teeth. KETAC MOLAR FOR ART constitutes the logical enhancement of the proven ESPE glass ionomers. Clinical Research 12/99 3

7 Clinical Research 12/99 4

8 KETAC MOLAR FOR ART is a conventional, metal-free glass ionomer which was specially developed as a restorative material for molars and premolars. The improved mechanical properties and the packable consistency were achieved with an optimised size of glass particles. 2.4 Motivation As already mentioned heavy-bodied glass ionomers constitute an extremely promising class of material. Numerous scientific studies indicate that the strength of heavy-bodied glass ionomers in comparison with conventional glass ionomers is in some cases much greater. Particularly the resistance of the heavy-bodied glass ionomers to abrasion has been increased. Improved polishability and radiopacity were further aspects which were taken into account when developing KETAC MOLAR FOR ART. 2.5 Indications After many years of clinical application of KETAC MOLAR, including applications as a restorative material in the ART technique, use of the material can be recommended for the following indications: core build-ups class I restorations semi-permanent class II restorations primary tooth restorations Clinical Research 12/99 5

9 3. Chemical Background 3.1 General overview Heavy-bodied glass ionomers are obtained not only by simply mixing glass powder and a polycarbonic acid. As with conventional glass ionomers, the curing takes place between the polycarbonic acids in the fluid and the reactive fluorocalcium-aluminium-silicate-glass of the glass powder. In contrast with conventional glass ionomers these cements are characterised by a much higher abrasive stability. 3.2 Chemical background The curing of glass ionomers is a complex sequence of chemical reactions in which water plays a major role. Whilst in the first curing phase the presence of water as a solvent is crucial for starting the reaction between the powder and polycarbonic acid, the glass ionomers are extremely sensitive to the ingress of water in the subsequent curing phase. But excess drying should also be avoided. The chemical processes in curing may be divided into different stages. 1) Decomposition of the glass structure: A major requirement for the types of glass used is their solubility in acids. Whilst cross-linked silicates are attacked by virtually no acid, calcium-aluminium-silicate types of glass even react with a relatively weak polycarbonic acid. The reason for this is the aluminium component in the glass. Aluminium is integrated into the cross-linked silicate and ensures that the aluminosilicate acquires a formally negative charge. As a result the glass turns alkaline and can therefore be attacked by inorganic acids, but also by organic ones. These negative charges are compensated for in the glass powder with alkaline ions or alkaline earth ions (see Fig. 1). Clinical Research 12/99 6

10 First stage Acid attac Second stage Glass structure without acid attack [SiO 4 ] Tetrahedron [AlO 4 ] - Tetrahedron Si(OH) 4 Orthosilicic acid Fig. 1: Structure of an aluminosilicate (Illustration: A. D. Wilson, J. W. McLean "Glass Ionomers", published by Quintessenz, 1988, p. 26) In the first step the calcium and sodium ions are replaced by protons. Then, in a second step, all the aluminium-oxygen bonds are broken and orthosilicic acid forms. Clinical Research 12/99 7

11 2) Curing Fig. 2: Formation of the silica gel at the surface of the glass (Ill. A. D. Wilson, J. W McLean, "Glass Ionomers", published by Quintessenz, 1988, p. 45) Acid attack takes place at the surface of the glass particles. It is a heterogeneous reaction between a solid and a liquid. The resulting silicic acid reacts spontaneously with other molecules of silicic acid causing polycondensation to form a silica gel. The ions which were originally firmly integrated into the glass are released and migrate into the aqueous phase of the cement. This effect can be observed, for example, during the release of fluoride ions from the glass ionomers. The cations released react with the anions of the polycarbonic acids to form polycarboxysilates which are insoluble in water. Clinical Research 12/99 8

12 3) Action of the tartaric acid To ensure adequate working time, tartaric acid is used as a complexation reagent for the dissolved metal ions. The complexation during the first setting period causes metal ions to be temporarily withdrawn from cross-linking with the polyanions. This reaction is a reversible process. At the subsequent setting stage the previously complexed metal ions are again available for cross-linking. In this way the setting process can be optimised for a practical procedure. Working time is extended and setting time is reduced ("Snap set"). 4. Product Composition Glass ionomers (polyalkenoate cements) consist of the powder/liquid combination characteristic of dental cements. Conventional glass ionomers use polycarbonic acids. The powder component includes special reactive types of glass. The curing mechanism is an acid-base reaction between these types of glass and the polycarbonic acid from the liquid. 4.1 Presentation KETAC MOLAR FOR ART is a two-component, chemically curing, glass ionomer based restorative material. The product is available both as a capsule version (KETAC MOLAR APLICAP) with its user-friendly direct application feature and as the successful hand-mix version (KETAC MOLAR FOR ART). Clinical Research 12/99 9

13 4.2 Constituents The qualitative composition of the two components of KETAC MOLAR FOR ART is listed in tables 1 and 2. Table 1: Composition of the powder contained in KETAC MOLAR FOR ART Ca, La, Al-fluorosilicate glass Pigments The mean size of glass particles contained in the powder of KETAC MOLAR FOR ART is 2.7 µm. The grain size distribution indicates that 90% of all the particles are smaller than 9 µm and 10% of all the particles are smaller than 1 µm. Table 2: Composition of the liquid contained in KETAC MOLAR for ART Polycarbonic acid Tartaric acid Water The liquid is preserved with benzoic acid. The powder/liquid ratio is 2.9:1 5. Test Results 5.1 Material properties The setting process for glass ionomers already described in the previous chapter causes materials in this class to cure with virtually no contraction. Therefore there Clinical Research 12/99 10

14 are only minimal stresses in the material which can lead to marginal gap formation at the cavity margins. For this reason, when using glass ionomers no additional complex bonding agents have to be applied as is normally necessary with polymerisation products. Consequently there is no need for a high strength of bond to the enamel and dentine, which tends to counteract contraction due to setting. Furthermore, glass ionomers have a coefficient of thermal expansion which is similar to that of the teeth. Additional stress on the adhesive bond between the restorative material and the hard tooth substance caused by large temperature differences thus does not arise. These two material properties ensure that an optimised clinical marginal behaviour of glass ionomers can be achieved without having to specify high bond strength. Another important material property of glass ionomers is resistance to abrasion. When using conventional glass ionomers the abrasion/erosion of the restoration, particularly in the molars and premolars, is a defect which is frequently observed. In the oral cavity, glass ionomers are subject to chemical and mechanical degradation. At the point of contact between the restoration and the tooth the result is formation of "negative ledges". Consequently, for an aesthetically and clinically attractive restoration it is not only the above-mentioned properties which are desirable but also high resistance to abrasion. 5.2 Physico-technical data Internal tests The physical properties of KETAC MOLAR for ART are listed in table 3. The figures are based on specification test procedures issued by the International Standards Organization (ISO) and the German Institute for Standards (DIN). Clinical Research 12/99 11

15 KETAC MOLAR is available both as a capsule version (KETAC MOLAR APLICAP) with its user-friendly direct application feature, and as a tried and tested hand-mix version (KETAC MOLAR for ART). The physico-technical characteristics of KETAC MOLAR APLICAP and KETAC MOLAR for ART are no different from one another on account of the inaccuracy in measurement. Owing to this analogous relationship the capsule version results listed in chapter 5 also apply to the handmix version. Table 3: Mechanical properties of KETAC MOLAR for ART KETAC MOLAR for ART KETAC MOLAR APLICAP Standard Setting time 3:30 (min:sec) 2:15 (min:sec) ISO 9917 Compressive strength 210 MPa 230 MPa ISO 9917 Flexural strength 37 MPa 30 MPa ISO 4049 Surface hardness 420 MPa 450 MPa ISO Radiopacity 250% 270% ISO External tests at universities The flexural strength of glass ionomers constitutes an important criterion in assessing quality. High flexural strength has a major influence on the clinical success of a restoration. Apart from the ISO method already described above for measuring 3-point flexural strength, 4-point flexural strength also represents a valid method for measuring this material property. It is evident that the individual materials tested differ with regard to the mean flexural strength, considerably in some cases. Clinical Research 12/99 12

16 [MPa] Ketac Molar Fuji IX HiDense Fig. 3: 4-point flexural strength of different heavy-bodied glass ionomer cements and Ketac-Fil Plus (unpublished results: Sindel et al., University of Erlangen) 5.3 Abrasion tests The problem of resistance to the oral environment and of durability is of major importance for all dental materials. The long-term success of conventional glass ionomers can be influenced in various ways: by working the glass ionomer restorative material, protecting the restoration against damaging influences in the oral cavity which may cause the material to erode, and by adjusting the mechanical properties of the material. Among the large number of mechanical properties, resistance to abrasion is an important aspect for ensuring that the restoration has a long life. Clinical Research 12/99 13

17 Since conventional glass ionomers can only have inadequate strength relative to abrasion resistance, endeavours were made during development of KETAC MOLAR for ART to achieve a considerable improvement in the mechanical properties by optimising composition. By varying the powder/liquid ratio and the grain size distribution it was possible to achieve higher levels of strength and keep the setting behaviour user-friendly at the same time. The behaviour of KETAC MOLAR (Aplicap) with regard to abrasion and that of the main rival products was determined by means of a 3-media abrasion procedure ("ACTA method") (Fig. 4). It is evident from the results that for all heavy-bodied glass ionomer cements, with the exception of Fuji IX, virtually identical abrasion values can be obtained. [µm] Ketac Molar Fuji IX HiDense Ionofil Molar Fig. 4: 3-media abrasion of heavy-bodied glass ionomers (Lohbauer et al., University of Erlangen) Clinical Research 12/99 14

18 5.4 Adhesion tests A durable bond between the glass ionomer and the hard tooth substances is indispensable to ensure the durability of a restoration. Good marginal adaptation prevents leakages, secondary caries and pulpal irritation. By contrast with the acid etching technique for composites the adhesion of glass ionomers to the hard tooth substances is of a purely chemical nature. Micromechanical retention plays no role whatsoever in the adhesion of glass ionomers. With the proposed adhesive mechanism, complexation of the carboxylate groups from the glass ionomer with the calcium ions from the hydroxyl apatite of enamel and dentine is crucial. Adhesion to the enamel tends to be greater than adhesion to the dentine. The reason for this is that approx. 98% of enamel and only 70% of dentine is made of hydroxyl apatite. In the case of dentine, therefore, a glass ionomer chiefly adheres to the apatite components. There is only minimal or no adhesion whatsoever to the collagen [MPa] Ketac Molar Fuji IX Fig. 5: Shear bond strength of KETAC MOLAR to the enamel (K.-H. Friedl et al., University of Regensburg) Clinical Research 12/99 15

19 5.5 Marginal behaviour As already mentioned, good marginal behaviour is a crucial criterion in assessing the quality of a restorative material. In an in vitro investigation at the Okayama University Dental School the marginal integrity of glass ionomer restorations was examined for KETAC MOLAR and Fuji IX. As soon as the restoration had been placed and again after one day of exposure to water, light microscopy was performed to investigate how wide the gap which had formed was at the widest point. Fig. 6 shows that virtually identical values can be obtained for both products. [µm] Ketac Molar Fuji IX Sofort 1. Tag Fig. 6: Marginal behaviour of KETAC MOLAR (M. Irie, Okayama University) Clinical Research 12/99 16

20 5.6 Fluoride release Glass ionomers are generally characterised by a high release of fluoride. The clinical relevance of this fluoride release has been discussed controversially for many years now. Indications that glass ionomers have a cariostatic effect may, inter alia, be found in a study by Mejàre and Mjör, in which glass ionomers were used as fissure sealants. In none of the cases investigated was secondary caries found, although over a total observation period of 5 years a loss rate of 61% in 6-12 months and a loss rate of 84% in months was established for glass ionomer sealants. By comparison, the rate of caries in the resin sealant control group was 5% over the same period. A three-year study which was performed by Karlzén-Reuterving et al. resulted in a similar picture. Whilst the retention of a resin-reinforced glass ionomer cement was only 27.8% after three years, caries occurred in only 1.4% of the cases. By comparison, the rate of caries for a resin sealant was 4.2%, although 79.2% of the sealants were still present. The authors of that study maintain that the positive effect of the glass ionomers was due to a cariostatic effect of glass ionomer materials. Numerous other authors suggest a connection between the provable fluoride release of glass ionomer cements and their action with regard to caries prevention. Clinical Research 12/99 17

21 4,5 4 3,5 3 [ppm] 2,5 2 1,5 1 0, Woche 2. Woche 3. Woche 4. Woche 5. Woche 6. Woche 7. Woche 8. Woche Fig. 7: Fluoride release of KETAC MOLAR (internal measurements, ESPE Dental AG) Figure 7 shows that KETAC MOLAR continuously releases fluoride ions over a period of two months. 6. In vivo studies on KETAC MOLAR for ART Over the last few years many clinical studies have been performed for KETAC MOLAR for ART. Below there is a summary of some of the results. 6.1 Multi-centre study in China: In a long-term study conducted by Dr. Chris Holmgren and Dr. Edward Lo on deciduous teeth, KETAC MOLAR for ART was used both in small and large class I cavities and as a fissure sealant. All in all, 294 ART restorations and 191 fissure sealants were placed in 140 schoolchildren at 4 different schools. The restorations were checked once a year. For the 3-year investigation the restorations were checked by an independent examiner in accordance with USPHS criteria. The USPHS criteria are internationally recognised clinical quality criteria, according to which restorations are normally assessed in clinical studies. Clinical Research 12/99 18

22 After three years 92% of all the small class I restoration and 77% of all the large class I restorations were classified as clinically successful Class I (small) Class I (large) 20 0 Baseline 1 Year 2 Years 3 Years Fig. 8: Retention rates for various ART restorations (C. Holmgren et al.) Fig. 9: Baseline 1 year Fig. 10: 2 years 3 years Clinical Research 12/99 19

23 Over the entire period of observation 72% of the fissure sealants were partially or entirely present. In only 2% of sealed teeth had secondary caries occurred during the period of observation. Fig. 11: Baseline 3 years 100% 80% 60% 40% Loss Intact/partial loss 20% 0% 3 Monate 1 Jahr 2 Jahre 3 Jahre Sekundär- Karies (3 Jahre) Fig. 12: Retention of fissure sealants (C. Holmgren et al.) The study demonstrated that KETAC MOLAR for ART very effectively helps in treating existing cases of caries and reducing the occurrence of caries when used as a sealant. Furthermore, the acceptance of ART therapy by children being treated is very high. A survey conducted during the study showed that 92% of the children were no longer afraid of a continuation of ART treatment. Clinical Research 12/99 20

24 6.2 Clinical study in South Africa In a controlled "Split Mouth" design study with KETAC MOLAR for ART on deciduous teeth, which was performed by Mickenautsch et al in South Africa, Fuji IX served as the control group. The schoolchildren participating had no access to dental treatment. In total, 1,325 children with an average age of 10.5 years were examined at 16 primary schools. 63.8% of the children had no caries and the mean DMFT value (index resulting from the total of carious, missing and restored teeth) was A total of 163 cavities were treated with KETAC MOLAR for ART and Fuji IX. After one year 108 restorations were subjected to a check-up. Over the observation period of 12 months the proportion of successful KETAC MOLAR for ART restorations was 94%. For the Fuji IX control group the proportion of intact restorations was 93.1%. By comparison with previous data obtained by the team, which was recorded at a time when the population observed still had no access to the ART technique, a significant reduction in tooth extractions was observed both for permanent teeth and deciduous teeth. [%] Molars and premolars (deciduous) Molars and premolars (Permanent) Fig.: 13: Reduction in the number of extractions after using the ART technique (comparative data: ) In the authors' view the ART technique constitutes an attractive form of therapy for treating caries defects in the population described. No statistically significant differences were observed between KETAC MOLAR for ART and the control group. Clinical Research 12/99 21

25 6.3 Clinical study in Peking In a clinical study conducted by Smales, Yip et al. the clinical successes of KETAC MOLAR for ART restorations were compared with those of Fuji IX after an observation period of 12 months. The study also compared the ART technique and the conventional method of treatment with rotary instruments. A total of 149 class I restorations were placed for baseline examination. After 12 months 98 restorations were checked. In the case of KETAC MOLAR for ART one restoration and one fissure sealant were reported to have been lost over the observation period. Despite the loss of the sealant no formation of caries was found on the tooth involved. KETAC MOLAR for ART and Fuji IX produced virtually identical results with regard to clinical success. 7. Conclusion The glass ionomers developed in the 1960s and 1970s cover a wide field of applications. Owing to the low abrasion resistance of conventional glass ionomers heavy-bodied glass ionomers were developed. This class of material manifests a number of positive properties compared with conventional glass ionomers, which make it ideal for a large number of clinical applications, including the ART technique. The ART technique is a method with which caries can be treated at an early stage. The aim of ART is to minimise tooth loss caused by caries. In many laboratory investigations and clinical studies KETAC MOLAR for ART was found to produce excellent results particularly when used with an ART technique. Especially when used as a restorative material for class I cavities or as a fissure sealant, KETAC MOLAR for ART has proved successful all over the world. A study in South Africa demonstrated that when KETAC MOLAR for ART was used the chief aim of the ART technique, namely to minimise tooth loss, was achieved convincingly. Undesirable tooth loss was reduced by over 35% in that study. Clinical Research 12/99 22

26 8. Literature 8.1 Clinical studies with KETAC MOLAR for the ART technique E. C. M. Lo, C.J. Holmgren "Eighteen-month evaluation of ART fillings placed in Chinese preschool children" J. Dent. Res. (IADR Abstract # 2101), S. Mickenautsch, M.J. Rudolph, E. O. Ogunbodede "The impact of the ART approach on the treatment profile in a Mobile Dental System (MDS) in South Africa" Int. Dent. J. 49, , E.C.M. Lo, C.J. Holmgren, H.C. Wan, D.Y. Hu "Provision of Atraumatic Restorative Treatment (ART) in Western China - one year results" J. Dent. Res. (IADR Abstract # 37), W. Gao, D. Peng, R.J. Smales, M.S. Gale Clinical trial of ART technique restorative Gl cements: initial findings" J. Dent. Res. (IADR Abstract # 40), General literature on Ketac Molar U. Lohbauer, M. Pelka, R. Frankenberger, N. Krämer "Influence of Mixing Procedures on Wear Resistance of Glass Ionomer Cements" J. Dent. Res. (IADR Abstract # 988), R. Frankenberger, N. Krämer, A. Graf, A. Petschelt "Zyklische Ermüdung von Glasionomerzementen und Kompomeren" Dtsch. Zahnärztl. Z. 54, , M. Pelka, J. Sindel, A. Petschelt "Lapping Abrasion Behavior of Condensable Glass-ionomers" J. Dent. Res. (IADR Abstract # 2739), M. Irie, T. Yamada, H. Nakai "Marginal Adaptation of High-viscosity Glass lonomers in Enamel Margins" J. Dent. Res. (IADR Abstract # 1452), C.C. France, M.R. Towler, R.W. Billington "Correlation between erosion and stress relaxation in maturing glassionomers" J. Dent. Res. (IADR Abstract # 463), Clinical Research 12/99 23

27 M.C.P. Nunes, D.F.G. Cefaly, L. Tenuta, J.R.P. Lauris, M.F.L. Navarro "Compressive and Diametral Tensile Strength of Two Restorative Glass lonomer Cements" J.J. Dent. Res. (IADR Abstract # 458), K.-P. Stefan "Early solubility of glass ionomer cements" J. Dent. Res. (IADR Abstract # 454), J. Ellacuria, R. Triana, N. Minguez, E. Guinea, F. Soler, F. Garcia-Godoy "Effects of Aging Time on Microhardness of Glass Ionomer Cements" J. Dent. Res. (IADR Abstract # 459), T.F. Watson, M. Naasan, M. Sherriff "Maturation of Glass Ionomer Cements and Shear Bond Strength (SBS) J. Dent. Res. (IADR Abstract # 384) A. Peutzfeldt, F. Garcia-Godoy, E. Asmussen "Surface hardness and wear of glass ionomers and compomers" Am. J. Dent , K.-H. Friedl, G. Schmalz, K.-A. Hiller, A. Gottlieb "Bond Strength of resin modified glass ionomer cements and compomers" J. Dent. Res. (IADR Abstract # 2400), A. Graf, J. Sindel, N. Krämer, A. Petschelt "Wear and Cyclic Fatigue of new Glass Ionomer Cements" J. Dent. Res. (IADR Abstract # 2427), R. Frankenberger, J. Sindel, N. Krämer "Stopfbare Glasionomerzemente - eine neue Amalgamalternative im Milchgebiß?" Quintessenz 47, , Further literature l. Mejàre, I.A. Mjör "Glass ionomer and resin-based fissure sealants: a clinical study" Scand. J. Dent. Res. 98, , G. KarIzén-Reuterving, J.W.V. van Dijken "A three-year follow-up of glass (ionomer cement and resin fissure sealants" Journal of dentistry for children, , Clinical Research 12/99 24