The Journal of Adhesive Dentistry, 04/2008

Purpose: To summarize research conducted on self-adhesive cements and provide information on their properties, based on the results of original scientific full-length papers from peer-reviewed journals listed in PubMed. Materials and Methods: The search was conducted using the term "self-adhesive cement OR (trade names of currently available products)". Results: Only in vitro studies that investigated two commercially available self-adhesive cements have been published so far. The results were summarized into the following categories: adhesion to tooth substrates (enamel, dentin, root dentin), adhesion to restorative materials (endodontic posts, ceramics, titanium abutments), marginal adaptation, microleakage, mechanical properties, biocompatibility, chemical adhesion and fluoride release, and ratings in clinical use. Conclusion: The majority of available literature data is based on studies that investigated one of the self-adhesive cements that are currently available to clinicians. According to the in vitro results, self-adhesive cement adhesion to dentin and various restorative materials is satisfactory and comparable to other multistep resin cements, while adhesion to enamel appears to be a weak link in their bonding properties. Long-term clinical performance of these materials needs to be assessed prior to making a general recommendation for their use. Keywords: self-adhesive cements, review

Purpose: (1) To compare SEM quantitative marginal analysis data with the depth of penetration (DP) of the three most commonly used tracers for microleakage in Class II fillings in vitro; (2) based on the obtained results to calculate the discriminatory power of a sample size of 12. Materials and Methods: Standardized large cavities (mesially 1 mm above the CEJ, distally 1 mm below the CEJ, intercuspal distance 70%) were prepared into 36 extracted caries-free first mandibular molars and filled with Tetric EvoCeram/AdheSE, the resin being applied in horizontal layers 2 mm thick. Each increment was light cured for 20 s (1200 mW/cm2). Finishing was performed with fine diamond burs and disks. All teeth were subjected to occlusal loading (1,200,000 cycles, 49 N/1.7 Hz) and simultaneous thermocycling (3000 cycles at 5°C/55°C). The percentage of continuous margin of the cervical dentin and enamel was evaluated on replicas using SEM. The teeth were subjected to tracer penetration with either 0.5% basic fuchsin (24 h, 37°C), 2% methylene blue (24 h, 37°C) or 50% silver nitrate solution (4 h, 37°C, followed by 8-h exposure to a photodeveloping solution and overnight fluorescent light). The teeth were mesiodistally sectioned twice. The depth of tracer penetration was measured with a stereomicroscope and averaged for each site. Due to data inhomogeneity and abnormal distribution, both SEM and DP data were transformed. Sample size calculations were performed based on standard deviation and statistical error estimates. Results: For the dentin margin, there was an acceptable correlation between SEM data and both fuchsin penetration (Pearson: -0.74, p 0.01) and silver nitrate penetration (Pearson: -0.79, p 0.01), but not between methylene blue and SEM data. For enamel margins, no significant correlation between SEM and DP data was found for the three tracers. There was statistically no significant difference in tracer penetration between the three tracers (Kruskal Wallis, p > 0.05). For all three tracers, statistically significantly higher penetration occurred at the dentin than at the enamel margin (Wilcoxon, p 0.05). A sample size of 12 makes it possible to discriminate between materials only when they differ in tracer penetration in the range of 1 mm for enamel and 2 mm for dentinal margins. Conclusion: Tracer penetration with fuchsin or silver nitrate showed a moderate correlation with SEM quantitative marginal analysis data at dentinal margins, but not at enamel margins. Keywords: microleakage, marginal analysis, restoration, tracer, dentin adhesives

Purpose: 1) To test a new perfusion device able to alternate demineralizing/nondemineralizing solutions, as an acid attack system, and 2) to standardize the dentin demineralization procedure, in order to define the in vitro secondary caries inhibiting potential of different restorative materials. Materials and Methods: A fluoride-containing adhesive/composite resin (group A), an experimental adhesive/composite resin (group B), and a glass-ionomer cement (group C) were used to restore 24 Class II cavities in extracted molars. Optimal conditions to obtain dentin demineralization inside the perfusion device were identified and applied to restored teeth. Dentin demineralization after perfusion was analyzed by microradiography. The output parameters were lesion morphology, dentin mineral volume percentage, and integrated mineral loss (Delta Z, %volume x µm) of the exposed (outer lesions) and marginal (inner lesions or caries inhibition zones, CIZs) dentin. Results: Demineralization increased as follows: group A group B group C. Group A behaved better than group B, probably due to fluoride content, as indicated by Delta-Z values, higher number of CIZs, and few inner lesions. Group C showed a marginal protective effect, demonstrated by the frequent CIZs and Delta-Z positive values. This effect, however, was unable to reduce the high demineralization, probably due to the critical handling characteristics, inducing the worst marginal adaptation. Conclusion: A new dynamic perfusion device was tested and a reproducible procedure was standardized in order to achieve in vitro conditions that could better simulate the pH changes of oral environment. A limited fluoride protective effect was demonstrated by using the perfusion system, whereas a perfect marginal adaptation was shown as a paramount factor to prevent restoration failure. Keywords: perfusion device, secondary caries, dentin, restoration, microradiography

Purpose: To determine the influence of convergence angles and axial planes on shear bond strength between dentin and adhesive composite resin luting cement, and its relation to dentin micromorphology. Materials and Methods: The four axial planes of 60 intact extracted mandibular molars were prepared at either 4 or 20 degrees to the longitudinal tooth axis. A Teflon cylindrical mold (1.6 mm) was filled with Rely X-ARC, bonded to Single Bond treated dentin surface and tested for shear bond strength after 7 days. Three SEM micrographs (5000X magnification) were taken from each surface after removing the bonding layer. The tubule circumference was marked using Adobe Photoshop. Micromorphology parameters were analyzed with the MATLAB program. A Mixed Effect Linear Model and linear regression were performed to analyze the influence of tubule density, tubule area, tubule circumference, and residual dentin thickness on shear bond strength. Results: The shear bond strength was not significantly different between axial planes (p > 0.05), but was significantly higher at 4 degrees than at 20 degrees (p=0.009). A significant positive correlation was found between shear bond strength and tubule area (R = 0.43, p = 0.003) or tubule circumference (R = 0.42, p = 0.003), confirming the importance of resin penetration into the tubules. No correlation was found between shear bond strength and tubule density (R = 0.22, p > 0.05) or residual dentin thickness (R = -0.22, p > 0.05). More round and more elliptic tubule orifices characterized dentin prepared at 4 and 20 degrees, respectively. Conclusion: Regional variations in tubule cross-section appearance can modify the bond strength of adhesive resin luting cements. Keywords: dentin, shear bond strength, micromorphology, convergence angle, tubule orientation

Purpose: To investigate the impact of resin cement luting variables and short-term water storage on the strength of an adhesively luted all-ceramic restorative material. An understanding of the strengthening mechanisms will result in optimisation of operative techniques and materials selection criteria. Materials and Methods: The "fit" surfaces of 480 disk-shaped feldspathic porcelain specimens were alumina air abraded to introduce a clinically relevant surface texture and consistent surface defect population. Thirty specimens randomly allocated to each of 16 groups were coated with silane, unfilled resin or filled resin cement, or a combination. Eight groups were stored either dry or wet for 24 h prior to bi-axial flexure testing (ball-on-ring). Statistical analysis of the flexure strength data involved a three-factor general linear model (p 0.05) prior to a Weibull analysis. Results: Resin coating the porcelain surface resulted in a significant increase in the characteristic stress (σo), and strengthening was dependent on coating type (p 0.001). Silane priming resulted in additional strengthening when preceding filled resin cement coating. Water immersion for 24 h resulted in a strength degradation of both the uncoated control and coated specimens, whereby the magnitude of strength degradation was dependent on coating type (p 0.001). Conclusion: Resin luting of dental ceramics results in significant strengthening likely to impact on clinical performance. The strengthening is dependent on the creation of a resin-ceramic hybrid layer sensitive to cementation variables and clinical placement technique. Short-term water immersion results in a significant degradation of strengthening sensitive to the characteristics of the resin-ceramic hybrid layer. Keywords: silane priming, resin luting, water storage, feldspathic porcelain

Purpose: To compare effects of free-hand and mechanically applied uniform irradiation on tensile bond strength of 4- META/MMA-TBB resin to Er:YAG laser-irradiated dentin using an X-Y moving stage. Materials and Methods: Three different laser conditions were evaluated: 1.0 W, 100 mJ/pulse, 10 pps; 1.0 W, 50 mJ/pulse, 20 pps; 1.0 W, 33 mJ/pulse, 30 pps. Samples of bovine dentin were set on a moving stage and mechanically irradiated with an Er:YAG laser at a scanning speed of 1.0 mm/s or subjected to free-hand irradiation. The lased dentin surfaces were acid conditioned with 10% citric acid/3% ferric chloride for 15 s, rinsed, and dried. The surfaces were bonded to PMMA rods with 4-META/MMA-TBB resin, and mini-dumbbell-shaped bonded specimens were prepared. Tensile bond strength was measured and compared with the results for free-hand irradiated samples obtained under the same conditions in an earlier study. SEM observations of fractured surfaces after tensile bond testing were also performed. Results: A significant difference was found in tensile bond strength among the 3 laser settings in both free-hand and mechanically uniform irradiations. A comparison of free-hand laser irradiation and mechanically performed uniform laser irradiation revealed no significant difference under either laser condition (p > 0.05). SEM observation of the fractured surfaces showed no difference between the two irradiation methods under all laser conditions. Conclusion: No significant difference was found in tensile bond strength between free-hand and mechanically irradiated dentin. Significant differences were found, however, with changes in laser setting in both groups. Keywords: Er:YAG laser, dentin bonding, 4-META/MMA-TBB resin, laser energy, pulse frequency, output energy

Purpose: The aim of this prospective clinical evaluation was to show the long-term clinical behavior of resin-bonded fixed partial dentures (RBFPD) with a retentive, minimally invasive preparation design. Materials and Methods: Since 1985, 232 RBFPDs with a retentive preparation design were placed under controlled clinical conditions. In 2005 and 2006, 84 fixed partial dentures could be re-evaluated. Using Kaplan-Meier analysis, the survival rate was determined. The probability of survival was calculated with several risk factors: location (anterior/posterior, maxilla/mandible), metal alloy of the framework (titanium/CoCr), number of pontics, and number of supporting teeth. Results: A total of 12 failures was observed and resulted in a survival rate of 77% after 10 years. However, only 4 catastrophic failures occurred. In such cases, the restoration was lost, or could not be re-bonded or repaired (survival rate 88% after 10 years). RBFPDs made of a titanium alloy exhibited a statistically significantly higher survival rate than RBFPDs made of a nonprecious CoCr alloy in terms of all failures. Only slight but not statistically significant differences between the covariates maxilla, mandible, anterior/posterior region, number of pontics, and number of abutment teeth were observed. Conclusion: Within the limitations of this study, RBFPDs seem to be a reliable restorative alternative to conventional short-span fixed dental prostheses. Keywords: resin-bonded fixed partial denture (RBFPD), resin-bonded, minimally invasive preparation, survival, clinical study

Purpose: The aim of the present study was to clinically evaluate the effect of two different adhesive / resin composite combinations for luting IPS Empress inlays with a special focus on luting gap wear and marginal adaptation. Materials and Methods: In the course of a controlled prospective clinical split-mouth study, 94 IPS Empress restorations were placed in 31 patients. The inlays were luted with EBS Multi + Compolute (EC; 3M ESPE) or with Syntac + Variolink II low (SV; Ivoclar Vivadent). At baseline and after 0.5, 1, 2, 4, and 8 years, the ceramic restorations were examined according to modified USPHS codes and criteria. Thirty-five selected samples were investigated under an SEM regarding morphological changes; marginal quality analysis was carried out using a stereo light microscope, and luting composite wear was scanned with a profilometer. Results: Eight patients (including 25 restorations) missed the recalls; the recall rate at the last investigation was 72%. After 96 months of clinical service, seven restorations in five patients (six EC, one SV) had to be replaced due to hypersensitivities (n = 5) or inlay fractures (n = 2) resulting in a survival rate of 90%. Over the 8-year period, the restorations revealed no statistically significant differences in terms of surface roughness, color matching, proximal contact, sensitivity, or complaints (p > 0.05, Friedman test). Significant deteriorations were found for marginal integrity (p 0.05). No significant differences were observed for the different luting systems (p = 0.096, Log rank test / Mantel Cox). Marginal analysis revealed no statistical difference among the materials (p > 0.05; Mann-Whitney U-test), however, the scans of the luting gap showed that Compolute was more prone to wear (p 0.05). Conclusion: For luting of ceramic inlays, no difference between the two luting systems was detectable. The overall failure rate after 8 years was 10%. Keywords: glass ceramics, dentin bonding agents, etch-and-rinse, self-etching, clinical trial

Purpose: To evaluate and compare the 2-year clinical performance of an ormocer, a nanohybrid, and a nanofill resin composite with that of a microhybrid composite in restorations of small occlusal cavities made in posterior teeth. Materials and Methods: Thirty-five patients, each with 4 occlusal restorations under occlusion, were enrolled in this study. A total of 140 restorations was placed, 25% for each material: an ormocer-based composite, Admira; a nanohybrid resin composite, Tetric EvoCeram; a nanofill resin composite, Filtek Supreme; and a microhybrid resin composite, Tetric Ceram. Two operators placed all restorations according to the manufacturers' instructions. One week after placement, the restorations were finished/polished and patients were advised to return for follow-up at 6 months, 1 year, and 2 years. All patients attended the 2-year visit where the clinical performance of all restorations was evaluated. Two independent examiners made all evaluations according to the USPHS modified Ryge criteria immediately after placement of restorations and at subsequent recall visits. The changes in the USPHS parameters during the 2-year period were analyzed with the Friedman test. Comparison of the baseline scores with those at the recall visits was made using the Wilcoxon signed rank test. The level of significance was set at p 0.05. Results: All materials showed only minor changes, and no differences were detected between their performance at baseline and after 2 years. Only one ormocer and one microhybrid composite restoration had failed after 2 years. No failure was detected in nanohybrid and nanofill composite restorations. Regarding the clinical performance, there were no statistically significant differences among the materials used (p > 0.05). Conclusion: After 2 years, the ormocer, nanohybrid, and nanofill composites showed acceptable clinical performance similar to that of the microhybrid resin composite. Keywords: ormocer, nanofill composite, nanohybrid composite, clinical evaluation