The Journal of Adhesive Dentistry, 01/2007

Purpose: The purpose of this prospective randomized controlled clinical study was to evaluate the clinical performance of a "mild" two-step self-etching adhesive, Clearfil SE, in Class V restorations after 5 years of clinical functioning. Materials and Methods: Twenty-nine patients received two or four restorations following two randomly assigned experimental protocols: (1) a mild self-etching adhesive (Clearfil SE, Kuraray) was applied following manufacturer's instructions on both enamel and dentin (C-SE non-etch); (2) similar application of Clearfil SE, but including prior selective acid-etching of the enamel cavity margins with 40% phosphoric acid (C-SE etch). Clearfil AP-X (Kuraray) was used as the restorative composite for all 100 restorations. The clinical effectiveness was recorded in terms of retention, marginal integrity, marginal discoloration, caries recurrence, postoperative sensitivity, and preservation of tooth vitality after 5 years of clinical service. The hypothesis tested was that selective acid etching of enamel with phosphoric acid improved retention, marginal integrity, and clinical microleakage of Class V restorations. Results: Only one restoration of the C-SE non-etch group was lost at the 5-year recall. All other restorations were clinically acceptable. Marginal integrity deteriorated with time in both groups. The number of restorations with defect-free margins was significantly lower in the C-SE non-etch group (p = 0.0043). This latter group presented significantly more small incisal marginal defects on the enamel side (p = 0.0169). Superficial marginal discoloration increased in both groups, but was more pronounced in the C-SE non-etch group and was related to the higher frequency of small incisal marginal defects. Conclusion: The clinical effectiveness of the two-step self-etching adhesive Clearfil SE remained excellent after 5 years of clinical service. Additional etching of the enamel cavity margins resulted in an improved marginal adaptation on the enamel side; however, this was not critical for the overall clinical performance of the restorations. Keywords: adhesives, clinical trial, cervical lesions, composite restoration.

Purpose: To measure in vitro the cuspal deflection produced by polymerization shrinkage and occlusal loading in mesio-occlusal (MO) and mesio-occlusal-distal (MOD) bonded composite restorations. Materials and Methods: Twenty first premolars were studied, attaching a small crystal ball to each cusp vertex as a reference point for intercuspal distance measurements. MO cavities were made in ten premolars and MOD cavities in the other ten. Cavities were then restored with Syntac Single adhesive and Tetric Ceram composite in two increments. A precision micrometer was used to measure intercuspal distances in unaltered teeth (baseline distance), unaltered teeth under 150 N load, restored teeth at 5 min after restoration completion, and restored teeth under 150 N load. Results: In the two study groups, both polymerization shrinkage and application of 150 N load produced a statistically significant change in intercuspal distance compared with baseline measurement. The cuspal deflection produced by 150 N load was statistically similar between unaltered and restored teeth, although polymerization shrinkage acted as a preload in the latter case (starting point was not baseline condition). The cuspal deflection produced by polymerization shrinkage and occlusal load was significantly greater in MOD than in MO restorations. Conclusion: The cuspal deflection produced by composite polymerization shrinkage and occlusal loading is significantly greater in MOD vs MO composite restorations. Keywords: occlusal loading, cuspal flexure, cuspal deflection, cusp movement, polymerization shrinkage.

Purpose: To investigate the effect of different light-curing units and adhesive systems on the bonding of leucite ceramic to dentin. Materials and Methods: Flat dentin surfaces were ground occlusally on human molars (n = 60). Hot-pressed ceramic blocks of IPS Empress (Ivoclar-Vivadent) were fabricated, air-particle abraded, and cleaned in distilled water. Following acid etching and silane treatment of ceramic, bonding procedures were performed. The teeth were divided into two groups according to the type of the adhesive system: (1) total-etch: etchant (Etch 37) and adhesive (One Step Plus); (2) self-etching: self-priming etchant (Tyrian SPE) and adhesiveOne Step Plus) (n = 30). Ceramic blocks were bonded to the dentin surfaces with dual-polymerizing resin luting cement (Duolink). For polymerization, the QTH (Blue Swan Digital, Dentanet) was used in soft-up and high-power mode, the LED (Elipar Freelight 2, 3M Espe) in exponential and standard mode, and the PAC (PlasmaStar, SP-2000, Monitex) in normal and ramp-curing mode (n = 5). Following storage in distilled water for 24 h, the samples were thermocycled for 6000 cycles. The bonded specimens were serially sectioned and trimmed to hourglass shapes with approximately 1.6 ± 0.16 mm2 cross-sectional areas, then tested with the microtensile tester at a rate of 1 mm/min. Fracture surfaces (were analyzed with SEM. The data were analyzed with three-way analysis of variance (ANOVA). Results: ANOVA revealed that adhesive systems (p 0.001) and light-curing units (p = 0.015) had a significant effect on bond strength values. Bond strength means (± SD) in MPa were as follows: total-etch system: QTH/soft-up mode = 16.2 (5.4); QTH/high power mode = 15 (5.4); LED/standard mode = 12.1 (3.3); LED/exponential mode = 15 (5); PAC/normal mode = 19.3 (7); PAC/ramp-curing mode = 19.6 (7.4). Self-etching system: QTH/soft-up mode = 9.9 (2.1); QTH/high-power mode = 12.5 (4.3); LED/standard mode = 8.6 (2); LED/exponential mode = 13 (3.8); PAC/normal mode = 13.1 (3.9); PAC/ramp-curing mode = 8.9 (2.2). Conclusion: Results indicated that the conventional total-etch system provided more reliable bonding compared to the self-etching system. The PAC light-curing unit together with the total-etch adhesive system showed the highest mean µ-TBS values with either normal mode or ramp-curing mode. Keywords: microtensile bond strength, leucite ceramic, light-curing units, adhesive systems.

Purpose: To compare the 24-h microtensile bond strength of a microfilled hybrid composite to the same material after mechanical and/or chemical treatment and assess the effect of oxygen inhibition on the composite-composite bond. Materials and Methods: Forty composite cylinders of Gradia Direct Anterior (GC) were prepared and stored 24 h prior to the following surface treatments: 50-µm aluminum oxide air abrasion and 37% phosphoric acid etching (group 1); hydrochloric acid and 6.9% hydrofluoric acid etching (group 2); diamond bur roughening and 37% phosphoric acid etching (group 3); diamond bur roughening (group 4). In all groups, Prime & Bond NT (Dentsply De Trey) was applied and light cured in air or under a nitrogen atmosphere, prior to layering a buildup of the repairing resin composite. Microtensile bond strength measurements were performed. Data were statistically analyzed with two-way ANOVA and Tukey's test (α = 0.05). Results: The curing atmosphere did not significantly influence the interfacial strength (p 0.05). Surface treatment significantly affected the composite-composite bond (p > 0.05). Air abrasion, regardless of curing atmosphere, resulted in the strongest bond (p 0.05). The other treatments were comparable. Conclusion: Air abrasion and the application of a bonding agent offer satisfactory bond strengths for composite repair. The oxygen inhibition layer on a light-cured adhesive is not crucial to the success of the 24-h composite-composite bond. Keywords: composite repair, surface treatment, oxygen-inhibited layer, microtensile bond strength.

Purpose: To determine effects of light curing of self-etching adhesives under ambient air or nitrogen on inhibition depths, enamel and dentin bond strengths, and marginal adaptation in dentin cavities. Materials and Methods: The adhesives investigated were: AQ Bond (AQB, Sun Medical; Kyoto, Japan), iBond (IBO, Heraeus Kulzer; Hanau, Germany), One-Up Bond F II (OUB, Tokuyama; Tokyo, Japan), and Prompt L-Pop (PLP, 3M/ESPE; Seefeld, Germany). Inhibition layer thickness (ILT) was microscopically measured on 3 disk-shaped specimens each. Shear bond strengths (SBS) on enamel and dentin (n = 8) were determined after 10 min and 24 h water storage of bonded composite specimens (Venus, Heraeus Kulzer). The marginal adaptation of bonded Venus restorations in cylindrical dentin cavities was microscopically evaluated after 10 min of specimen storage (n = 8) in water. The data were statistically analyzed using parametric and nonparametric ANOVA and post-hoc tests at p 0.05. Results: Adhesive curing under air revealed significant ILT (µm) differences: IBO (4) AQB (8) PLP (12) OUB (23). Upon curing in nitrogen atmosphere, no inhibition occurred with AQB, IBO, and PLP, and 3 µm for OUB. SBSs on enamel after 10 min or 24 h did not differ according to curing atmospheres (p > 0.05). On dentin, SBSs were higher after curing under N2 (p 0.05). Irrespective of the curing atmosphere, marginal adaptation was good for AQB and IBO and poor for PLP; OUB revealed significantly smaller gaps under N2 than under air curing. Conclusion: Oxygen inhibition of the four self-etching adhesives investigated had no or only moderate effects on bonding efficacy to enamel and dentin. Keywords: self-etching adhesives, oxygen inhibition, enamel-dentin bonding, cavity marginal adaptation.

Purpose: In this in-vitro study, microleakage of all-ceramic crowns was evaluated at enamel and dentin margins. Materials and Methods: Forty maxillary central incisors were randomly divided into 4 groups (n = 10). While buccal and palatal margins were placed on enamel, mesial and distal margins were placed below the cementoenamel junction. In groups 1 to 3, IPS Empress 2 crowns were luted with Variolink 2/Syntac Classic (group 1), Bifix DC/Solobond Plus (group 2) and Calibra/Prime & Bond NT combinations (group 3), respectively. In the control group (group 4), porcelain-fused-to-metal crowns were luted with a zinc-phosphate cement. All specimens were subjected to 5000 thermocycles (at 5°C to 55°C; 30-s dwell time). After immersion in India ink for 48 h at 37°C, the specimens were sectioned both buccolingually and mesiodistally. Each section was evaluated for microleakage under a stereomicroscope at 24X magnification. Results: According to the Krukal-Wallis test, in all groups, there were significant differences in microleakage at the enamel margins (p = 0.001). Nevertheless, the margins finished in dentin showed no significant differences (p = 0.163). According to the Mann-Whitney U-test, statistically significant differences were observed in microleakage between groups 1 and 3 (p = 0.049), groups 1 and 4 (p = 0.001), groups 2 and 4 (p = 0.002), and between groups 3 and 4 (p = 0.045) at the enamel margin. In group 1, significantly greater microleakage was observed at the dentin margin compared to the enamel margin (p = 0.007). Conclusion: The adhesive luting technique demonstrated an excellent ability to minimize microleakage of all-ceramic crowns at the enamel margins. Water-based dentin bonding systems showed less microleakage than the water-free acetone-based dentin bonding system at the enamel margin. Keywords: microleakage, adhesive luting, all-ceramic crown, dentin bonding, enamel bonding.

Purpose: The present study aimed to compare the fracture resistance and failure patterns of endodontically treated premolars with MOD preparations restored using different material combinations. The null hypothesis postulated that there was no association between the fracture resistance of endodontically treated premolars and the resin composite materials or the post-and-core system used to build up the restorations. Materials and Methods: Eighty single-rooted maxillary premolars were used. After endodontic treatment and preparation of MOD preparations, 8 groups of 10 samples each were created, using the following material combinations: group 1 (control), flowable and microhybrid resin composites; group 2, flowable A; group 3, flowable B; group 4, microhybrid resin A; group 5, microhybrid resin B; group 6, flowable B + microhybrid resin B; group 7, flowable A + microhybrid resin A + post A; group 8, flowable B + microhybrid resin B + post B. Mechanical static fracture tests were performed loading the specimens till fracture. Results: The mean failure loads (N) were 502 (control), 470 (group 7), 445 (group 8), 441 (group 6), 405 (group 5), 364 (group 4), 317 (group 2), and 302 (group 3). Statistically significant differences were found between groups 1 vs 2, 1 vs 3, and 3 vs 7 (p 0.05). Conclusion: The fracture resistance of endodontically treated premolars with MOD preparations was enhanced by the use of the sandwich technique. The samples restored with posts predominantly showed restorable fractures, while teeth restored without posts mostly displayed unrestorable failures. Keywords: composite, post, fracture resistance.

Purpose: This paired-tooth randomized controlled prospective clinical study compared the clinical performance of three composite resins in Class III cavities after 12 months. Materials and Methods: Three materials were evaluated: a microfilled composite resin (Durafill VS), a hybrid composite resin (Filtek Z250), and a nanofilled composite resin (Filtek Supreme). Thirty-eight patients having at least three Class III restorations were enrolled in this study. A total of 114 restorations were placed by two calibrated operators according to the manufacturers' instructions. The adhesive system (Clearfil SE Bond) was either applied according to manufacturer's instructions (CSE non-etch) or enamel margins were first etched with phosphoric acid (CSE etch). One week later, the restorations were finished and polished. Two other independent examiners evaluated the restorations at baseline according to the USPHS criteria and USPHS modified criteria for the items color match and surface appearance. The restoration location was taken into consideration during the analysis of each item. A nonparametric analysis of variance (Friedman test) and the Wilcoxon test were used for statistical analysis (α = 0.05). Results: The restoration location did not influence the evaluated items. Filtek Z250 showed the best color match at baseline, and after 6 and 12 months. No significant difference in the item surface appearance was detected at baseline; however, after 6 and 12 months, Filtek Z250 showed the worst performance on this item. No significant difference was found between CSE non-etch and CSE etch groups. Conclusion: The hybrid composite resin showed an excellent immediate and 12-month color match, which was superior to the nanofilled and microfilled composites tested. On the other hand, the nanofilled and microfilled composites showed the best surface appearance after 12 months. Additional etching of the enamel cavity margins did not influence the clinical performance of the adhesive Clearfil SE Bond. Keywords: composite resin, baseline evaluation, class III cavities, nanofilled composite resin, microfilled composite resin, hybrid composite resin, self-etching adhesive.

Purpose: An accepted principle in restorative dentistry states that restorations should be placed with the best marginal quality possible to avoid postoperative sensitivity, marginal discoloration, and secondary caries. Different laboratory methods claim to predict the clinical performance of restorative materials, for example, tests of bond strength and microleakage and gap analysis. The purpose of this review was twofold: (1) find studies that correlated the results of bond strength tests with either microleakage or gap analysis for the same materials, and (2) find studies that correlated the results of microleakage and/or gaps with the clinical parameters for the same materials. Furthermore, influencing factors on the results of the laboratory tests were reviewed and assessed. Materials and Methods: For the first question, searches for studies were conducted in the MEDLINE database and IADR/AADR abtracts online with specific search and inclusion criteria. The outcome for each study was assessed on the basis of the statistical test applied in the study, and finally the number of studies with or without correlation was compiled. For the second question, results of the quantitative marginal analysis of Class V restorations published by the University of Zürich with the same test protocol and prospective clinical trials were searched that investigated the same materials for at least 2 years in Class V cavities. Pearson correlation coefficients were calculated for pooled data of materials and clinical outcome parameters such as retention loss, marginal discoloration, marginal integrity, and secondary caries. For the correlation of dye penetration and clinical outcome, studies on Class V restorations published by the same research institute were searched in MEDLINE that examined the same adhesive systems as the selected clinical trials. Results: For the correlation bond strength/microleakage, 30 studies were included into the review, and for the correlation bond strength/gap analysis 18 studies. For both topics, about 80% of the studies revealed that there was no correlation between the two methods. For the correlation quantitative marginal analysis/clinical outcome, data were compared to the clinical outcome of 11 selected clinical studies. In only 2 out of the 11 studies (18%) did the clinical outcome match the prognosis based on the laboratory tests; the remaining studies did not show any correlation. When pooling data on 20 adhesive systems, no correlation was found between the percentage of continuous margin of restorations placed in extracted premolars and the percentage of teeth that showed no retention loss in clinical studies, no discoloured margins, acceptable margins, or absence of secondary caries. With regard to the correlation of dye penetration and clinical studies, no sufficient number of studies was found that matched the inclusion criteria. However, literature data suggest that there is no correlation between microleakage data as measured in the laboratory and clinical parameters. Conclusion: The results of bond strength tests did not correlate with laboratory tests that evaluated the marginal seal of restorations such as microleakage or gap analysis. The quantitative marginal analysis of Class V fillings in the laboratory was unable to predict the performance of the same materials in vivo. Therefore, microleakage tests or the quantitative marginal analysis should be abandoned and research should focus on laboratory tests that are validated with regard to their ability to satisfactorily predict the clinical performance of restorative materials. Keywords: marginal quality, bond strength, microleakage, marginal gap, clinical relevance, Class V.

Purpose: In vitro testing of dental materials is daily routine for the preclinical investigation of restoratives. Although clinical trials remain the ultimate instrument, preclinical screenings are still important. However, it is still not fully understood whether clinical performance is predictable in the lab. The aim of this paper is to combine known facts and recent results to answer the question concerning in vitro predictability of clinical marginal integrity and related outcome. Materials and Methods: (a) The literature in the field from 1990-2005 was analyzed regarding marginal integrity in vitro and in vivo, especially in frequently cited papers. (b) Five different adhesives, a 4-step etch-and-rinse adhesive (Syntac), a 3-step etch-and-rinse adhesive (OptiBond FL), a 2-step etch-and-rinse adhesive (Single Bond), a 2-step self-etching adhesive (Clearfil SE Bond), and a 1-step self-etching adhesive (Xeno III) were used for bonding of a resin composite (Tetric Ceram) in Class I cavities (n = 8 in vitro and n = 8 in vivo). In vitro, the restorations were thermomechanically loaded (TML; 100,000 with 50 N and 2500 cycles of 5°C/55°C) according to a previously published protocol. Replicas of restorations were analyzed initially and after TML (in vitro) and two years of clinical service (respectively). Results: (a) Marginal integrity is reliably predictable in laboratory in vitro studies by simulating clinical circumstances. However, marginal analyses of direct restorations in vitro still suffer from not being able to determine a lower boderline, ie, actually worse in vitro results may still result in acceptable restorations in vivo. (b) The in vitro-in vivo comparison revealed significantly better marginal adaptation in (enamel) margins when etch-and-rinse adhesives were used for bonding. After 2 years of clinical service, restorations bonded with self-etching adhesives did not clinically fail but exhibited significantly more marginal gaps. Conclusion: Clinical behavior of restoration margins is predictable. However, marginal adaptation is only one among several important aspects in restorative dentistry, ie, clinical outcome is not predictable from marginal integrity alone. Keywords: marginal integrity, gap, etch-and-rinse, self-etching, adhesives, resin composites.

Abstract: The question "Does initial marginal quality of composite restorations have any affect on clinical longevity?" is posed and evidence presented to attempt to provide an answer. This paper examines the literature on what is known regarding the rates and causes of failure of restorations, clinical evaluation of restoration outcomes and marginal quality, the relationship between marginal quality and secondary caries, and the relationship of polymerization shrinkage and clinical failures. The most frequently reported cause for restoration replacement is secondary caries. The evidence that poor marginal quality promotes or is the primary cause for secondary caries is limited and indicates that any direct relationship is unlikely. There is evidence that secondary caries is related to the bacterial composition of marginal plaque, and that this and oral hygiene are the primary factors in disease initiation. Evidence also exists that dentists vary in their diagnoses of secondary caries and that except in the presence of frank secondary caries, it is not possible to diagnose secondary caries with high sensitivity and specificity based on visual and tactile examination of restoration margins. Marginal gaps created by polymerization shrinkage do not appear to increase the risk for secondary caries, but can lead to marginal staining. Initial marginal quality should not affect longevity, as it does not necessarily increase the risk of secondary caries. However, poor marginal quality is, in fact, likely to decrease clinical longevity due to the misdiagnosis of secondary caries. Keywords: dental, restoration, margin, clinical.

Abstract: About 35 years ago, Ryge provided a practical approach to the evaluation of the clinical performance of restorative materials. This systematic approach was soon universally accepted. While that methodology has served us well, a large number of scientific methodologies and more detailed questions have arisen that require more rigor. Current restorative materials have vastly improved clinical performance, and any changes over time are not easily detected by the limited sensitivity of the Ryge criteria in short-term clinical investigations. However, the clinical evaluation of restorations not only involves the restorative material per se but also different operative techniques. For instance, a composite resin may show good longevity data when applied in conventional cavities but not in modified operative approaches. Insensitivity, combined with the continually evolving and nonstandard investigator modifications of the categories, scales, and reporting methods, has created a body of literature that is extremely difficult to interpret meaningfully. In many cases, the insensitivity of the original Ryge methods leads to misinterpretation as good clinical performance. While there are many good features of the original system, it is now time to move on to a more contemporary one. The current review approaches this challenge in two ways: (1) a proposal for a modern clinical testing protocol for controlled clinical trials, and (2) an in-depth discussion of relevant clinical evaluation parameters, providing 84 references that are primarily related to issues or problems for clinical research trials. Together, these two parts offer a standard for the clinical testing of restorative materials/procedures and provide significant guidance for research teams in the design and conduct of contemporary clinical trials. Part 1 of the review considers the recruitment of subjects, restorations per subject, clinical events, validity versus bias, legal and regulatory aspects, rationales for clinical trial designs, guidelines for design, randomization, number of subjects, characteristics of participants, clinical assessment, standards and calibration, categories for assessment, criteria for evaluation, and supplemental documentation. Part 2 of the review considers categories of assessment for esthetic evaluation, functional assessment, biological responses to restorative materials, and statistical analysis of results. The overall review represents a considerable effort to include a range of clinical research interests over the past years. As part of the recognition of the importance of these suggestions, the review is being published simultaneously in identical form in both the Journal of Adhesive Dentistry and Clinical Oral Investigations. Additionally, an extended abstract will be published in the International Dental Journal, giving a link to the web full version. This should help to introduce these considerations more quickly to the scientific community.