The Journal of Adhesive Dentistry, 01/2005

Purpose: To investigate the influence of the acid-base reaction between acidic monomers and amines on the polymerization behavior of self-etching, self-curing adhesives, determine the effect of the application mode on the shear bond strength and morphology, and elucidate the adhesion performance of such systems by shear bond strength measurements. Materials and Methods: The amine redox-initiator system N,N-di(2-hydroxyethyl)p-toluene (DEPT)/dibenzoyl peroxide (BPO) was selected to investigate the influence of the amine-base reaction on polymerization behavior. The pKa value of DEPT hydrochloride was measured by titration with NaOH. The influence of the pH value and DEPT concentration on the polymerization rate of methacrylates was investigated by exotherm time measurements. Three different application protocols of Multilink Primer (Ivoclar Vivadent) and Panavia 21 ED-Primer (Kuraray) were tested, 15 s passive vs 15 s agitation vs 60 s passive in combination with the corresponding resin luting material. The effects of these three application protocols were evaluated and monitored by both shear bond strength tests and SEM characterization of the surface morphology. The adhesion potential of these self-etching, self-curing luting systems was compared on enamel and dentin both directly after application and after 24 h. Results: The pKa of DEPT-HCl is 4.45. The polymerization rate of the DEPT-containing, self-etching, self-curing adhesive system is highly influenced by both the amine concentration and the pH value. In the case of Multilink, agitation of the primer mixture for 15 s, especially on dentin, resulted in a higher bond strength and a more pronounced removal of the smear layer. Multilink resulted in statistically higher bond strengths (p 0.05) than Panavia 21 for both the enamel and dentin directly after application and for the dentin after 24 h. Conclusion: Radical polymerization initiators used in self-curing systems are strongly adversely affected by acidic monomers incorporated in self-etching adhesives. However, if there is a good adjustment of these components and effects of adhesive application are taken in account, high bond strengths can be achieved. Keywords: self-etching adhesive, self-curing initiator, acidic monomers, amine protonation, pKa value, shear bond strength

Purpose: First, to elucidate the cause of the appearance of "white lines" in Class V restorations as seen under the light microscope and their enhancement when using a fluorescent microscope (FM); second, to compare the results of the FM quantitative marginal analysis to those of the SEM quantitative marginal analysis. Materials and Methods: Thirty-two standardized Class V fillings, with half of the preparation in dentin and half in enamel, were placed in 16 human caries-free premolars on the buccal and lingual surface using 4 adhesive systems (Clearfil SE, Syntac, 2 experimental self-etching adhesives) and the composite Tetric Ceram. All teeth were connected to a device containing horse serum to simulate dentinal fluid and subjected to thermomechanical loading (1,200,000 cycles at 49 N, 3000 cycles at 5°C/55°C). The restoration margins of 24 fillings were directly evaluated with FM - after the fabrication of replicas - and with SEM. Eight filllings were used to elucidate the cause of the fluorescent signal, by examining them with FM and different filters under dry and moist conditions, and also with dark field microscopy and CLSM. Further, two Class V fillings with the same composite but without the fluorescent substances were made and evaluated. Selected specimens were cut in the bucco-oral direction to analyze the restorative interface on section replicas with SEM. To detect differences between FM and SEM, the Wilcoxon test was performed (p 0.05). To evaluate the degree of agreement between the two evaluation methods, a linear regression analysis was performed and the Spearman correlation coeffcient was calculated. Results: The evaluation of Class V restorative margins by SEM, dark field microscopy, and CLSM revealed that the phenomenon seems to be an optical effect caused by the debonding of the composite from the underlying substrate creating another refractive environment when air penetrates into the gap. The effect depends on the geometry of the cavity design, the absence of moisture, and the use of a fluorescent composite material. The light source that produced the best visible results covered both ultraviolet and the blue part of white light (350 to 460 nm), producing light green lines and green areas. Those green or white areas as seen with the light microscope were related to gaps in the interface between tooth substance and composite. With the exception of one of the experimental self-etching adhesives, the mean percentage of continuous margin of the 4 groups showed no statistically signifcant dfference for the two test methods. Linear regression analysis revealed a good correlation between the two test methods for dentin margins and a moderate correlation for enamel margins. Conclusion: Fluorescence microscopy seems to be a useful tool for evaluating dentinal and enamel margins of Class V restorations in vitro. Keywords: restoration margin, fluorescence microscopy, SEM, autofluorescence, white lines

Purpose: To evaluate the influence of direct high-dose gaseous ozone application (2100 ppm) on dentin and enamel shear bond strength. Materials and Methods: Ten bovine enamel and dentin samples per group were pretreated as follows: (I) ozone application (Healozone, KaVo) for 60 s alone or (II) with subsequent application of a fluoride- and xylitol-containing antioxidant (liquid reductant), (III) light-activated bleaching with 35% hydrogen peroxide for 5 min serving as negative control (Hi-Lite, Shofu), and (IV) untreated enamel and dentin (positive control). Specimens were bonded with a functional 3-step adhesive system (Syntac Classic, Ivoclar Vivadent) and restored with a composite (Tetric Ceram, Ivoclar Vivadent) according to the Ultradent method. After storage in water at 37°C for 24 h, shear bond strength was measured using a Zwick universal testing machine. Data were analyzed using ANOVA and Scheffe's post hoc analysis. Results: In concordance with the existing literature, bleaching resulted in significantly decreased bond strength (p 0.05) on enamel specimens. No decrease in shear bond strength was detected for ozone-pretreated specimens compared to untreated controls. Conclusion: Despite a possible retention of surface and subsurface oxide-related substances during high-dose ozone application, shear bond strength was not impaired. Thus, adhesive restoration placement should be possible immediately after ozone application for cavity disinfection. Keywords: dental material, ozone, enamel, dentin, shear bond strength, in vitro

Purpose: This in vitro study evaluated the wall-to-wall adaptation of a new self-adhesive resin-based cement (RelyX Unicem) in comparison with that of other cements when luting gold and porcelain inlays in standardized Class II cavities in extracted teeth. Materials and Methods: In each experimental group (n = 10), a different combination of inlay and luting material was tested. Group 1: Porcelain Empress II (EII) and RelyX Unicem (U); group 2: EII and resin-based cement Variolink II in combination with primer and bonding Excite DSC; group 3: gold inlays (G) and U; group 4: G and Harvard zinc-oxy-phosphate cement; group 4: G and glass-ionomer cement Fuji Cem. After storage and thermocycling, microleakage testing was carried out and dye penetration was examined at the occlusal and cervical margins of each inlay. The differences in microleakage score were tested for statistical significance first comparing all groups, then pooling the groups for inlay material (Kruskal-Wallis nonparametric ANOVA and Mann-Whitney U test, p 0.05). SEM observations of the tooth/cement/restoration interfaces were also made in each group. Results: Harvard cement had the highest microleakage. The sealing ability exhibited by RelyX Unicem was satisfactory with both gold and porcelain inlays, and comparable to that of Fuji Cem and Variolink II. Conclusion: RelyX Unicem achieved an adequate seal on both enamel and dentin when used to lute in vitro gold and porcelain inlays. Keywords: inlay, microleakage, self-adhesive resin cement

Purpose: This paper aims to examine varied surface treatments combined with adhesive bonding to ascertain the highest bond strength of the composite resin repair. Materials and Methods: A total of 100 specimens was made using an increment technique. The prepared specimens were aged for 20 days in 37° ± 2°C water and then kept for 24 h at room temperature. The samples were separated into 5 groups of 20, and each group then received a different surface treatment (control group, phosphoric acid, diamond bur, air abrasion, silane primer combined with a diamond bur treatment). The effect of each surface treatment on the bond strength was determined by a shear bond test. Results: Specimens that received surface treatment with a diamond bur exhibited higher shear bond strengths than any of the other repaired groups (p 0.05). Those treated with air abrasion had the second highest shear bond strengths, but without a statistically significant difference when compared to the control group (p > 0.05). Specimens treated with phosphoric acid showed virtually no difference compared to the specimens of the control group (p > 0.05). Conclusion: Statistical analysis revealed that surface treatment with a diamond bur results in higher shear bond strength than other tested methods. Keywords: bond strength, composite resin, dental materials, restoration repair, surface treatment, dentin bonding agents

Purpose: This study tested the null hypothesis that different treatments of saliva-contaminated substrate would not affect microgap formation at the dentin walls of bonded restorations. Materials and Methods: Forty freshly extracted human molars received standardized Class V preparations on buccal and lingual surfaces. The specimens were assigned to four experimental groups (n = 20): [G1] no contamination (control group), [G2] saliva contamination (10 s) after etching followed by 5 s air stream; [G3] saliva contamination after etching and rinsed for 10 s; and [G4] re-etching for 10 s after saliva contamination. All specimens were restored with a one-bottle adhesive (Single Bond, 3M ESPE) and microhybrid composite resin (Filtek Z250, 3M ESPE) according to the manufacturer's instructions. The specimens were thermocycled, sectioned through the center of the restoration, and then processed for SEM. Microgaps were measured at the axial wall at 1500X magnification. The data were submitted to Kruskal-Wallis nonparametric statistical analysis at p 0.05. Results: The data revealed that different groups resulted in a statistically significant difference (p 0.01) in gap formation. Air drying [G2] and rinsing [G3] the saliva-contaminated dentin resulted in similar microgap values (p > 0.05). However, re-etching the dentin after saliva contamination [G4] increased microgap formation (p 0.05) when compared with the groups G1 and G2. Although air drying and rinsing produced results comparable to noncontaminated dentin, the presence of microgaps was not completely eliminated. Conclusion: Contaminated saliva did not prevent hybrid layer formation; however, it did reduce the adaptation of the restorative material to bonded surfaces. Keywords: saliva, contamination, adhesive microgap

Purpose: To test the hypothesis that simpler-to-use dentin adhesives (7th-generation adhesives) perform better when used by inexperienced operators than do the more complex 4th-generation adhesives. Materials and Methods: Six operators with no previous experience regarding dental adhesives, three residents in pediatric dentistry, and three experienced dentists used one 4th-generation dentin adhesive (MA) and two 7th-generation adhesives (MB and MC). With each adhesive, each operator performed 6 bondings to enamel and 6 bondings to dentin. After 24 h of storage in water at 37°C, the shear bond strength was determined. Results: The pooled results showed that the bond strength to dentin was higher (p 0.05) than that to enamel (dentin mean value = 14.0 MPa, SD = 9.1 MPa; enamel mean value = 11.9 MPa, SD = 7.1 MPa), and that adhesive MA performed better (p 0.05) than adhesives MB and MC (inexperienced operators = 16.2 ± 10.9 MPa, residents in pedodontics = 12.0 ± 6.8 MPa, and experienced operators = 10.7 ± 4.8 MPa). Of the two 7th-generation adhesives, one performed better on enamel than on dentin, while the other 7th-generation adhesive performed better on dentin than on enamel. Regarding operators, there were large individual variations. The inexperienced bonders performed as well as the residents (p > 0.05), while the experienced operators performed best (p 0.05). Conclusion: In general, the tested 4th-generation adhesive performed better than the 7th-generation adhesives. Even inexperienced operators performed better with the more difficult-to-use 4th-generation adhesives than with the 7th-generation adhesives. Dentin adhesion was stronger than enamel adhesion. Keywords: technique sensitivity, iBond, Scotchbond MP, Prompt-L-Pop

Purpose: To evaluate the retention of restorations placed in non-undercut, noncarious cervical lesions using One-Up Bond F and Palfique Estelite resin composite. Materials and Methods: Fifty-one non-undercut, noncarious cervical lesions were restored with One-Up Bond F and Palfique Estelite in 15 patients (mean age 57.7 years). Teeth were cleaned with pumice and water and restored following the manufacturer's instructions. Restorations were evaluated at 6 months, 1 and 2 years for presence or absence, and for the degree of marginal staining using standardized colour photographs for comparison. Results: At 1 year, 42 restorations were evaluated, and all were intact. Slight marginal staining was observed in three restorations. At 2 years, 37 restorations were evaluated from 11 patients, and all were intact. Marginal staining was observed around nine restorations. ANOVA for marginal staining showed a significant increase of staining at both the enamel and cervical margins over the 2 years of the study. No caries was detected in association with any restoration. Conclusion: Although a number of restorations could not be evaluated, the retention of 100% at 2 years showed very good promise for the treatment of noncarious cervical lesions. The marginal staining was limited to a small number of patients. Keywords: clinical study, noncarious cervical lesion, dentin bonding

This article, focused around case presentations, follows the natural progression/exploration of a single idea about dealing with the Class II (approximal lesion) composite restoration. The gradual development of this idea and the integration of a concept from one case to the next may have certain educational value. Hopefully it will show the potential for further experimentation and inspire a fresh mentality in using and handling the main line of conservative restorative materials today, ie, resin composites. Keywords: composite resin, Class II restoration, polymerization contraction, direct treatment, shell