Resin-modified glass ionomer cement and self-cured resin composite luted ceramic inlays. A 5-year clinical evaluation

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1 Dental Materials 19 (2003) Resin-modified glass ionomer cement and self-cured resin composite luted ceramic inlays. A 5-year clinical evaluation Jan W.V. van Dijken* Department of Odontology, Dental School Umeå, Umeå University, Umea , Sweden Received 5 March 2002; received in revised form 27 August 2002; accepted 16 October 2002 Abstract Objective. This study evaluated IPS Empress ceramic inlays luted with two chemical-cured luting agents, a resin-modified glass ionomer cement (Fuji Plus (F)) and a resin composite (RC) (Panavia 21 (P)). Methods. Seventy-nine ceramic inlays were placed in Class II cavities in 29 patients. At least two inlays were placed in each patient to compare the luting techniques intra-individually. In each patient half of the inlays were luted with F and the other half with P. The inlays were evaluated clinically, according to modified USPHS criteria (van Dijken, 1986), at baseline, after 6 months, and yearly during 5 years. Results. At 5 years, 71 inlays were evaluated. Two small partial fractures were observed at 3 years (1P, 1F). One inlay showed recurrent root caries at 4 years (P). Four inlays, two in each group showed non-acceptable color match (2P, 2F). Small defects were observed in 4 inlays (2P, 2F). A slight ditching of the cement margins was observed in both luting groups but did not seem to increase during the second half of the evaluation. No significant difference in durability was observed between the two luting agents. Significance. IPS Empress inlays luted with the chemical-cured RC and the resin-modified glass ionomer cement functioned satisfactory during the 5 years follow-up Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. Keywords: Cement; Clinical; Composite; Glass ionomer; Luting; Resin 1. Introduction Ceramic inlays have been used extensively during the last decade as an esthetic alternative in posterior teeth. They may be sintered, milled, pressed or cast [1]. Limited information is available on the longevity of many of the systems [1]. Earlier evaluations of fired ceramic inlays luted with phosphate, glass ionomer cement or light-cured resin composite (RC) cement showed that these cements were not acceptable in clinical practice. Feldsphatic inlays luted with conventional glass ionomer cements demonstrated very soon a high failure rate due to insufficient retention of the cement to the ceramic material [2]. Dual-cured RCs have, therefore, been used during recent years in conjunction with the adhesive placement of ceramic inlays. However, several laboratory studies showed the inability of their chemicalcure to compensate for absence of visible light activation [3 6]. To ensure complete polymerization in the whole * Tel.: þ ; fax: þ address: jan.van.dijken@odont.umu.se (J.W.V. van Dijken). cement layer, chemical or self-cured luting agents have been proposed [7,8]. Due to a slower hardening reaction chemical-cured luting agents have the advantage of reduced polymerization shrinkage stress, which results in better marginal adaptation [9 11]. The absence of the long lightcuring times used to polymerize the dual-cured cements avoids also the rise of pulp temperature and decrease the risk for post-operative sensitivity [12 15]. The main reason for failure of fired ceramic inlays reported was fracture of the ceramic [1,16]. A new injection molded, leucite-reinforced ceramic material has been reported to undergo less shrinkage, show less porosity and be less brittle than conventional feldsphatic ceramics. The use of a resin-modified glass ionomer cement (RMGIC) to lute these ceramic inlays, should result in a reliable mechanical bond, fluoride release, and simplifies the complicated multi-step luting procedure of the RC cements used in combination with three step bonding systems. The aim of this in vivo study was to evaluate IPS Empress ceramic inlaysluted with a resin-modified glass ionomer cement and to compare it intra-individually with a chemical-cured RC /03/$ - see front matter 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi: /s (03)

2 J.W.V. van Dijken / Dental Materials 19 (2003) Materials and methods Twenty-nine patients, nine men and 20 women (mean age: 45.5 year, range 22 68), regularly visiting the Dental School of Umeå participated in the study. Each patient required at least two Class II inlays of approximately the same size, and placed in the same type of tooth. Seventynine pressed ceramic inlays (IPS Empress, Vivadent, Schaan, Liechtenstein) were placed in Class II cavities in 53 premolar and 26 molar teeth. The method of production, luting and evaluation has been described in the previously published 2 year evaluation of the inlays (16). At the luting appointment, the operation field was isolated with cotton rolls and a conventional saliva suction device before try-in of the inlays. In each patient, one of each pair of the inlays was luted with a RMGIC (Fuji Plus, GC Dental Industrial Corp., Tokyo, Japan; F). The other was luted with a selfcured RC luting agent in combination with its self-etching primer (Panavia 21, Kurary Co., Ltd, Osaka, Japan; P). Resin-modified glass ionomer cement luting. After the initial try-in one of the inlays, contaminated during the tryin, was cleaned and re-etched with 9.5% buffered hydrofluoric acid (HF) for 3 s and treated with silane coupling agent. The cavity was rinsed with water, and dried gently with compressed air and then conditioned with Fuji Plus conditioner for 20 s, rinsed with water and gently dried. The desired amounts of powder and liquid were mixed rapidly for 20 s on a paper mixing pad. The internal surface of the restoration and the cavity bonding surface was coated with a thin layer of cement. After insertion and immediately removal of excess cement, the luting agent was allowed to harden for 4 min. The margins were protected with an unfilled light-cured resin. RC luting. After try-in, the second inlay was also cleaned with HF for 3 s, rinsed with water and coated with a silane solution for at least 2 min. The preparation was conditioned during 60 s with the self-etching primer of the system (Panavia ED Primer, Kurary). Clearfil New Bond (Kurary) was applied on the inside of the inlay. Equal amounts of the catalyst and universal pastes of the luting agent (Panavia 21) were mixed for 20 s and a thin, even film, was applied to the pretreated adherend surfaces of the porcelain. The restoration was held under slight pressure for about 1 min, excess cement was carefully removed and Oxyguard II (Kurary) was applied to cover all margins of the inlay. After 3 min the Oxyguard was rinsed off with water spray and excess cement was removed. Occlusion and articulation were corrected after placement. The inlays were then finished with finishing diamonds of different grits and polishing stones. The inlays were evaluated after finishing, 6 months and yearly during 5 years. The evaluations were done independently by two investigators at the baseline, 6, 12 and 24 months evaluations. At the following annual evaluations by the author and at randomly chosen regular occasions by two investigators, with a slight modification of the United Public Dental Health System (USPHS) criteria [2,16]. Disagreement was resolved by consensus. The characteristics of the inlays were described by descriptive statistics using frequency distributions of the scores. The durability of the two luting techniques was compared intra-individually by comparing the overall quality of the inlays, expressed by the variables evaluated, and tested using Friedman s two-way analysis of variance test [17]. The null hypothesis, that there was no difference in durability for the luting techniques, was accepted at the 5% level. 3. Results All the patients, except for three with eight inlays, were evaluated at the 5 year recall. Two inlays (1P, 1F) were considered as non-acceptable due to small partial fractures of the ceramic between 2 and 3 years recall (1P, 1F). The fractured ceramic part of the P-luted inlay was reluted after HF-etch of the ceramic parts, and the second fractured F- luted inlay was repaired with flowable composite. Both repairs were still in place at the 5 year recall. Four inlays showed small defects, two with small ceramic chip fractures of the marginal ridge (1P, 1F), one with a small crack in the buccal part of an onlay (F) and one inlay showed a deep marginal proximal gap (P). No treatment was necessary for the inlays with small chip fractures. As a preventive measure the crack was covered with RC material after etching of the ceramic with HF acid. The submargination was filled with RC (Table 1). The frequencies of the scores of the evaluated variables, anatomical form, marginal adaptation, color match, marginal discoloration and surface roughness are shown in Table 2. One inlay (P) showed root caries contiguous to the inlay. In another case root caries was observed cervical but not in contact with the inlay. Four inlays showed a score three color match, one due to amalgam discoloration of the tooth and the other three because of abrasion of the colored surface layer. After removal of excess of the low viscosity RC cement, directly after insertion, the cervical margins of five inlays exhibited underfilled margins due to premature removal of the low-viscosity cement. All inlay margins were repaired with RC. In three patients post-operative symptoms were observed, which disappeared for one patient after 2 weeks and for the second after about 5 months. For the third patient there were still symptoms after 1 year during occlusal loading. This inlay tooth showed already sensitivity symptoms before luting, and endodontic treatment due to periapical pathosis was necessary after 1 year. The intraindividual ranking of the inlays with the Friedman s twoway analysis of variance test showed no significant difference between the two groups ðp, 0:05Þ:

3 672 J.W.V. van Dijken / Dental Materials 19 (2003) Table 1 Slightly modified USPHS criteria [2,16] Category Score Criteria Acceptable Unacceptable Anatomical form 0 The restoration is continuous with tooth anatomy 1 Slightly under- or over-contoured restoration; marginal ridges slightly undercontoured; contact slightly open (may be self-correcting); occlusal height reduced locally 2 Restoration is undercontoured, dentin or base exposed; contact is faulty, not self-correcting; occlusal height reduced; occlusion affected 3 Restoration is missing partially or totally; fracture of tooth structure; shows traumatic occlusion; restoration causes pain in tooth or adjacent tissue Marginal adaptation 0 Restoration is continuous with existing anatomic form, explorer does not catch 1 Explorer catches, no crevice is visible into which explorer will penetrate 2 Crevice at margin, enamel exposed 3 Obvious crevice at margin, dentin or base exposed 4 Restoration mobile, fractured or missing Color match 0 Excellent color match 1 Good color match 2 Slight mismatch in color, shade or translucency 3 Obvious mismatch, outside the normal range 4 Gross mismatch Marginal discoloration 0 No discoloration evident 1 Slight staining, can be polished away 2 Obvious staining cannot be polished away 3 Gross staining Surface roughness 0 Smooth surface 1 Slightly rough or pitted 2 Rough, cannot be refinished 3 Surface deeply pitted, irregular grooves Caries 0 No evidence of caries contiguous with the margin of the restoration 1 Caries is evident contiguous with the margin of the restoration 4. Discussion A wide range of cumulative failure frequencies have been observed for ceramic inlays/onlays due to differences in luting agents, ceramic properties, operator skills and patient selection [1,2,16]. The use of conventional GIC as luting agent for feldsphatic inlays resulted in relative high failure rates of 15 and 26% after 2 and 6 years, respectively [2]. The main reason for failure was partial fracture or total loss of the inlays caused by an adhesive bond failure at the ceramic cement interface. A 2 year follow up of 25 GIC luted Dicor inlays showed a 8% failure rate [18]. However, Zuellig-Singer and Bryant [19] investigating 35 Cerec inlays luted with RC or GIC cement found no significant differences between the cements during 3 years. Luting with a light-cured RC cement resulted in an 80% failure rate after 40 months [20]. The use of dual-cured RCs to lute feldspathic ceramic inlays promised an improved durability, but the results varied widely in different clinical evaluations [1]. The main reason for failure was fracture of the ceramic [1,16]. A disadvantage of the fired ceramic materials was the degree of microporosities and inhomogeneities between the ceramic particles. A more homogeneous ceramic was obtained by using precerammed ingots, as in this study, which reduced crack formation. Recent studies of this ceramic showed improved longevity with low failure rates of Empress inlays luted with dual-cured RC cements [16]. The polymerization of the dual cements depends, among other things, on exposure time and the intensity of the light source. It has been reported that dual RC luting agents were not sufficiently polymerized under thick and/or opaque ceramic restorations, due to the fact that a too low or no light intensity will reach the luting agents [3 6]. The use of alternative luting techniques with chemical-cured luting agents has, therefore, been proposed to ensure a complete polymerization in the cement layer [1,21]. These cements have a short working time but show less polymerization stress as a result of a slower hardening time, which can also optimize the interfacial adaptation and decrease postoperative sensitivity. A lower fracture frequency was shown by Sjögren et al. for with a self-cured luting RC cemented Cerec inlays compared to a dual-cured one [21]. In a 2 year follow-up of 130 Empress inlays and onlays, Studer et al. [22,23] used three dual-cured RC cements and

4 J.W.V. van Dijken / Dental Materials 19 (2003) Table 2 Distributions of the scores (%) for the two inlay groups at baseline and 5 years Acceptable Not acceptable Fuji Plus, Baseline Fuji Plus, 5 year Panavia 21, Baseline Panavia 21, 5 year Anatomical form Marginal adaptation Color match Marginal discoloration Surface roughness No: number evaluated restorations. the chemical-cured Panavia. They reported a 2.3% failure rate after 2 and 4 years and 5.5% after 6 years, but did not indicate for which of the luting agents. Thoneman et al. [8] showed in vitro good marginal integrity of ceramic inlays bonded to dentin with certain RMGIC. They concluded that RMGIC might be an alternative to dentin bonding agents. Anecdotal reports linked the cement to post-cementation fractures but no clinical controlled study has confirmed this relation. Cracking of all-ceramic crowns has been reported in vitro when RMGIC cements were used as luting agents [24]. It was concluded that the water sorption of the cements resulted in an expansion sufficient to fracture the ceramic restoration. Crowns luted with Advance cement fractured (Caulk/Dentsply Inc., Milford, Del, USA). The authors stated that Advance cement could not be classified as a RMGIC. In the material polyacids had been replaced with polymerizable monomers or prepolymers that did not support an acid base reaction and the material should, therefore, not be defined as a glass ionomer cement. This material has been withdrawn from the market. As shown in our study, the luting with the two chemical-cured luting agents showed a good durability. The RMGIC showed an improved adhesion to the etched ceramic inlays compared to the earlier described conventional GIC [2]. After 5 years there was one small partial fracture for the RMGIC luted inlays and another one in the Panavia 21 group. The two test groups showed an equal durability, which was far better than the results found in a earlier clinical study for conventional feldsphatic ceramic inlays luted with a dualcured RC [2]. In a recently published study, the durability of restorations with extensive dentin/enamel-bonded posterior partial and complete ceramic coverages of the IPS Empress was investigated [25]. Also the effect of luting with a dualcured and a self-cured luting agent was studied. Of the 182 ceramics, 13 (7.1%) were assessed as non-acceptable after a mean observation period of 4.9 year (range year). No significant differences in failure rate were seen between the two luting agents or between the three dentin bonding agents used. 5. Conclusions It can be concluded that the two chemical-cured luting agents studied showed a good durability and no statistical differences in the clinical performance of the two luting cements were observed at 5 years. The result reported was observed for Empress inlays only and no conclusions can be made for the use of the luting agents to cement full crowns. Acknowledgements This study was partly supported by the County Council of Västerbotten and the Swedish Dental Association.

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