The Journal of Adhesive Dentistry, 05/2008

Purpose: To investigate the influence of uremia on the shear bond strength (SBS) of composite resin to enamel and dentin substrates with assessment of the micromorphological pattern of etched enamel and dentin surfaces using atomic force microscopy (AFM). Materials and Methods: A total of 44 natural molars was collected from healthy individuals (n = 22 molars) and uremic patients (n = 22 molars). Each set of teeth was then divided into 2 equal subsets (n = 11 molars) relative to the bonding substrate to be tested. In each subset, the surfaces of 7 molars were flattened and polished up to 2000-grit roughness using wet silicon carbide (SiC) abrasive papers. A three-step adhesive was used to bond Tetric Ceram composite buildups to the prepared tooth surfaces. All specimens were thermocycled before they were stressed in shear using a universal testing machine. Fractured specimens were stereomicroscopically examined to detect the mode of bond failure. In the remaining 4 molars, enamel and dentin specimens were prepared for AFM examination to assess the micromorphological patterns of acid-etched surfaces. Results: The mean bond strength values in MPa to enamel (22.40 ± 4.30) and dentin (17.97 ± 4.65) of teeth of healthy individuals were significantly different (p 0.001) from those to enamel (12.40 ± 2.81) and dentin (7.83 ± 2.05) of teeth of uremic patients. Most of the tested enamel specimens showed a mixed type of bond failure, but the adhesive type was predominant with dentin specimens. AFM examinations revealed a shallow etching pattern for uremic enamel and dentin specimens compared to those of healthy individuals. The mean roughness average (Ra) values after etching of healthy enamel (238.0 ± 4.65) and dentin (267.0 ± 4.79) were significantly different (p 0.001) from those to etched uremic enamel (111.0 ± 5.24) and dentin (143.0 ± 2.16). Conclusion: Uremia adversely affects bonding of composite resin to enamel and dentin and confers an altered micromorphological etching pattern. Keywords: uremia, resin composite, shear bond strength, enamel and dentin, acid-etch pattern

Purpose: This study evaluated the marginal quality of differently bonded direct resin composite restorations in enamel and dentin, before and after thermomechanical loading (TML). Special attention was focussed on the performance of selective enamel etching, etch-and-rinse, and self-etching adhesives. Materials and Methods: Eighty MO cavities with proximal margins beneath the cementoenamel junction were prepared in extracted human third molars. Direct resin composite restorations (Tetric EvoCeram, n = 8) were placed with 4-step selective enamel etching (Syntac SE), 4-step etch-and-rinse (Syntac ER), 2-step etch-and-rinse (XP Bond, Scotchbond 1 XT/Single Bond Plus), 2-step self-etching (AdheSE, Clearfil SE Bond), 2-step self-etching with selective enamel etching (AdheSE SE, Clearfil SE Bond SE), and 2-step self-etching with etch-and-rinse (AdheSE TE, Clearfil SE Bond TE). Marginal gaps were analyzed using epoxy resin replicas under a scanning electron microscope at 200X magnification. Results: Initially, high percentages of gap-free margins were identified for all adhesives. After TML, the results were as follows: A) Enamel margins: When phosphoric acid was used on enamel, results were constantly higher (~90%) compared with two-step self-etchin adhesives (~70%; p 0.05). B) Dentin margins: No statistical differences were found when etch-and-rinse and selective etch approaches were compared (59% to 64%; p > 0.05). When self-etching adhesives were used as per manufacturers' directions, dentin margins exhibited the best marginal quality (74% to 82%; p 0.05). When self-etching adhesives were used under etch-and-rinse conditions, marginal quality in dentin was significantly reduced to 35% to 42% (p 0.05). Conclusion: Enamel bonding was generally more effective with phosphoric-acid etching. Enamel bonding performance of 2-step self-etching adhesives was improved when phosphoric acid was applied on enamel selectively. Keywords: marginal integrity, gap, etch-and-rinse, self-etch, selective etch

Purpose: To evaluate acid-etching effects prior to the application of self-etching primer and the effect of different primer application techniques on dentin shear bond strength (SBS). Materials and Methods: Forty human third molar cervical regions were used in this study. The teeth were randomly divided into four groups (n = 10) of different tooth surface conditions: group A: Clearfil Protect Primer applied gently (inactive) + Clearfil Protect Bond; group B: 38% phosphoric acid for 15 s, rinsed 15 s, and dried 15 s + Clearfil Protect Primer applied gently (inactive) + Clearfil Protect Bond; group C: Clearfil Protect Primer applied with agitation by microapplicator brush (active) + Clearfil Protect Bond; group D: 38% phosphoric acid for 15 s, rinsed 15 s, and dried 15 s + Clearfil Protect Primer applied with agitation by microapplicator brush (active) + Clearfil Protect Bond. The SBS test was performed with a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with one-way ANOVA and Tukey HSD tests. Results: The mean SBS values (MPa) and standard deviations are as follows: group A: 36.0 ± 8.3; group B: 24.0 ± 3.9; group C: 35.0 ± 3.3; group D: 30.6 ± 6.7. Conclusion: Acid etching decreased the SBS of the self-etching bonding system to dentin. Active primer application increased the SBS only in acid-etched groups. Keywords: self-etching primer, acid etching, application procedure, shear bond strength

Purpose: The purpose of this study was to evaluate the cohesive strength of the composite using different resinous monomers to lubricate instruments used in the Restorative Dental Modeling Insertion Technique (RDMIT). Materials and Methods: The composite specimens were made by using a prefabricated Teflon device. Different resinous monomers were used at the interface to lubricate the instruments, for a total of 72 specimens divided into 6 groups: 1. control group, no resinous monomer was used; 2. Composite Wetting Resin; 3. C & B Liquid; 4. Scotchbond Multi-Purpose Adhesive; 4. Adper Single Bond Adhesive; 6. Prime & Bond NT. Specimens were submitted to the circular area tensile test to evaluate the cohesive strength at the composite interfaces. Data were analyzed using ANOVA and Tukey's test (α = 0.05). Results: ANOVA showed a value of p 0.0001, which indicated that there were significant differences among the groups. The means (SD) for the different groups were: Adper Single Bond Adhesive: 26 (12) a; control group: 28 (3) ab; Prime & Bond NT: 32 (12) ab; Composite Wetting Resin: 36 (9) abc; C&B Liquid: 38 (7) bc; Scotchbond Multi-Purpose Adhesive: 46 (10) c. Groups denoted with the same letters were not significantly different. Only Scotchbond Multi-Purpose Adhesive, used for direct restorations, had a statistically significantly higher bond strength than the control group, Adper Single Bond Adhesive, and Prime & Bond NT. Adper Single Bond with Adhesive showed a statistically significantly lower mean value than C & B Liquid. Conclusion: The results of this study indicate that the resinous monomers used for lubricating the instruments in the RDMIT did not alter the mechanical properties of the composite, and therefore did not reduce the cohesive bond strength at the composite interfaces. Keywords: resinous monomer, composite resin, cohesive strength

Purpose: The aim of this study was to evaluate in vitro the influence of retainer design on the strength of two-unit cantilever resin-bonded glass fiber-reinforced composite (FRC) fixed dental prostheses (FDP). Materials and Methods: Four retainer designs were tested: a proximal box, a step-box, a dual wing, and a step-box-wing. Of each design on 8 human mandibular molars, FRC-FDPs of a premolar size were produced. The FRC framework was made of resin impregnated unidirectional glass fibers (Estenia C&B EG Fiber, Kuraray) and veneered with hybrid resin composite (Estenia C&B, Kuraray). Panavia F 2.0 (Kuraray) was used as resin luting cement. FRC-FDPs were loaded to failure in a universal testing machine. One-way ANOVA and Tukey's post-hoc test were used to evaluate the data. The four designs were analyzed with finite element analysis (FEA) to reveal the stress distribution within the tooth/restoration complex. Results: Significantly lower fracture strengths were observed with inlay-retained FDPs (proximal box: 300 ± 65 N; stepbox: 309 ± 37 N) compared to wing-retained FDPs (p 0.05) (step-box-wing: 662 ± 99 N; dual wing: 697 ± 67 N). Proximal- box-, step-box-, and step-box-wing-retained FDPs mainly failed with catastrophic cusp fracture (proximal box 100%, step-box 100%, and step-box-wing 75%), while dual-wing-retained FDPs mainly failed at the adhesive interface and/or due to pontic failure (75%). FEA showed more favorable stress distributions within the tooth/restoration complex for dual wing retainers. Conclusion: A dual-wing retainer is the optimal design for replacement of a single premolar by means of a two-unit cantilever FRC-FDPs. Keywords: fiber-reinforced composite, cantilever, fixed dental prosthesis, static fracture strength, finite element analysis

Purpose: The aim of this study was to evaluate stress distribution in anterior adhesive fixed dental prostheses (FDP) and at the tooth/framework interface. Metal (M-FDP) and glass fiber-reinforced composite (FRC-FDP) frameworks were compared. Materials and Methods: The design of the FDP consisted of retainers on a maxillary central incisor and canine with a pontic of a lateral incisor. Two different framework materials were compared: isotropic Au-Pd alloy and anisotropic continuous unidirectional E-glass FRC. Veneers in both cases were made of isotropic veneering hybrid composite. A 3- dimensional finite element model of a 3-unit FDP loaded with 154 N (at a 45-degree angle to the incisal edge of the pontic) was used to analyze stress distribution in the FDP and at the adhesive interface. A finite element analysis was used in calculation of the maximum principal stress and displacement. Results: The maximum displacement of FRC-FDP was higher than that of M-FDP. Stress concentrations were located equally in the connectors and at the occluding contact points in both framework types. Maximum principal stress of FRC-FDP was lower than that of M-FDP. Stress analysis further indicated that the maximum stress in the luting cement interface of FRC-FDP was located at the middle part of the retainers, whereas in the M-FDP, the maximum stress was located at the marginal edge of the retainers. Conclusion: The FE model revealed differences in displacement and stress distribution between metal and FRC frameworks of FDP. The general observation was that FRC-FDP provided more even stress distribution from the occluding contact point to the cement interface than did M-FDP. Keywords: adhesive fixed dental prostheses, fiber reinforced composites, cement interface, finite element analysis, hybrid composite, prosthetic dentistry

Purpose: To examine the effect of different adhesive luting systems on the shear bond strength of all-ceramic restorations to dentin surfaces. Materials and Methods: Forty-eight all-ceramic disks (2 x 3 mm; IPS e.max Press) were fabricated. Forty-eight noncarious extracted human molars were divided into 4 groups. In groups 1 to 4, IPS e.max Press disks were luted with Variolink 2/Excite DSC (etch-and-rinse), Clearfil Esthetic Cement/Clearfil Protect Bond (antibacterial and self-etching), Multilink/Multilink Primer (self-etching), or Multilink Sprint (self-adhesive). All specimens were subjected to 5000 thermocycles (5°C to 55°C, 30-s dwell time). Shear bond strengths were tested using a universal testing machine until failure. The analysis of the fractured dentin surfaces was performed using an optical microscope at 10X and 1000X magnification; the images were analyzed with an image analyzer. Data were analyzed with one-way ANOVA and Tukey's test at a significance level of p 0.05. Results: Mean shear bond strength data of the groups in MPa were: Variolink 2/Excite DSC: 25.89 ± 3.71; Clearfil Esthetic Cement/Clearfil Protect Bond: 17.21 ± 2.71; Multilink/Multilink Primer: 11.6 ± 3.51; Multilink Sprint: 10.4 ± 3.15. According to the one-way ANOVA, there were significant differences in shear bond strength (p 0.001). According to Tukey's test, statistically significant differences were observed in shear bond strength between groups 1 and 2 (p 0.001), groups 1 and 3 (p 0.001), groups 1 and 4 (p 0.001), groups 2 and 3 (p = 0.003), and groups 2 and 4 (p 0.001). Conclusion: The etch-and-rinse dentin bonding system produced higher bond strengths of all-ceramics to dentin surfaces than did the self-etching bonding systems and self-adhesive luting system. Keywords: shear bond, self-adhesive, dentin bonding, all-ceramic

Purpose: To evaluate the effect of long-term water storage on the microleakage of a fissure sealant applied with or without different bonding agents. Materials and Methods: Extracted human third molars were randomly assigned into 8 groups (n = 24/each). The occlusal surfaces were sealed with a fluoride fissure sealant material (Helioseal F) after one of the following pretreatments: 1. phosphoric acid etching only; 2. phosphoric acid etching + Single Bond; 3. phosphoric acid etching + Prime & Bond NT; 4. Clearfil SE Bond; 5. FL Bond; 6. One Up Bond F; 7. Prompt L-Pop; 8. Mac Bond II. All specimens were thermocycled (1000X), after which half of them (n = 96) were stored in distilled water for 48 h (group A), and the remaining half (n = 96) for 48 months (group B). The specimens were immersed in 0.5% basic fuchsin solution, sectioned, and digitally photographed. Microleakage was evaluated quantitatively using an open-source image analysis toolkit (ImageJ), and the data were analyzed statistically. Results: Four-year water storage significantly increased the amount of leakage in all test groups (p 0.001). In both the absence and presence of water aging, the etch-and-rinse adhesives yielded the lowest microleakage scores (p 0.001). In the 48-h group, the following ranking was achieved in terms microleakage values: phosphoric acid + Prime & Bond NT = phosphoric acid + Single Bond Prompt L-Pop = phosphoric acid etching only FL Bond Clearfil SE Bond Mac Bond II = One Up Bond F. In the 48-month group, the ranking changed as follows: phosphoric acid + Prime & Bond NT = phosphoric acid + Single Bond Prompt L-Pop = FL Bond Clearfil SE Bond = Mac Bond II = One Up Bond F phosphoric acid etching only. Conclusion: Long-term water storage significantly increased the microleakage of Helioseal F applied alone and with a bonding agent. Regardless of the storage term, the use of etch-and-rinse adhesives resulted in significantly less microleakage compared to that achieved with self-etching adhesives or acid etching alone. The sealants placed without a prior bonding agent showed the greatest amount of leakage after four years. Keywords: microleakage, quantitative, etch-and-rinse adhesives, self-etching adhesives, fissure sealants

Purpose: To propose an experimental model for assessing the interfacial strength between post and luting agent under clinically relevant conditions of post space diameter and cement layer thickness. Materials and Methods: DentinPost (Komet, DP) and GC (GC) glass fiber posts were tested. A sample of 22 posts per type was randomly subdivided into two equal groups based on the material for cementation: Panavia F 2.0 (Kuraray, PF) and MultiCore Flow (Ivoclar Vivadent, MF). Within each group, 2 subgroups were defined depending on the procedure for specimen preparation. In subgroup A (NO-M), the resin cement was incrementally stratified around a post centered within a plastic matrix until the latter was filled. In subgroup B (M), first a mold of resin cement with an artificial post space was created. Then, using the same cement, the post was luted into the dowel space. Microtensile beams were cut and loaded to measure post/cement interfacial strengths. For statistical analysis of the data, Kruskall-Wallis ANOVA was applied, followed by Dunn's Multiple Range test (p 0.05). Results: Bond strengths in MPa were (median; 25th-75th percentile): DP/PF/M 4.5; 3.1-7.4; DP/PF/NO-M 9.2; 5.8- 12.4; DP/MF/M 14.2; 10.2-20-6; DP/MF/NO-M 16.5; 13.1-21.7; GC/PF/M 7.6; 3.3-11.7; GC/PF/NO-M 7.8; 5.1-11-9; GC/MF/M 16.7; 14.3-3-22; GC/MF/NO-M 20.4; 15.6-24. Irrespective of post type and of specimen preparation procedure, with or without mold, significantly higher bond strengths were measured for MF. On both post types, both cements achieved similar interfacial strengths regardless of the C-factor. Conclusion: The influence of a clinically relevant C-factor on the adhesion of resin cements to glass fiber posts was not statistically significant. Keywords: C-factor, fiber post, resin cement, microtensile

Purpose: This controlled clinical trial aimed to evaluate IPS Empress inlays and onlays over 12 years. The null hypothesis was that different luting resins would have no influence on clinical outcome. Materials and Methods: In the course of a prospective clinical long-term trial, 96 ceramic inlays and onlays were placed in 34 patients using one adhesive (Syntac) and four different luting composites (Tetric, Variolink Low, Variolink Ultra, Dual Cement). Recalls were carried out by two calibrated investigators using modified USPHS codes and criteria at baseline, 1, 2, 4, 6, 8, and 12 years. Results: Fifteen of the 96 restorations had to be replaced (failure rate 16%; Kaplan-Meier); 12 of them suffered bulk fractures. After twelve years of clinical service, significantly more bulk fractures were found when light-curing composite was used for luting (p 0.05). Fractures were noticed between 3 and 4 years of clinical service and later after 11 to 12 years; aside from those times, no single fracture occurred. Secondary caries was not observed. Conclusion: IPS Empress inlays and onlays exhibited satisfactory clinical outcomes over a 12-year clinical period. Restorations luted with dual-cured resin composites revealed significantly fewer bulk fractures. Keywords: ceramics, resin composites, luting, dual-curing, dentin bonding, clinical trial

Purpose: The purpose of this study was to compare the clinical performance of a polyacid modified resin composite and a nanocomposite applied with an antibacterial adhesive system over a period of 2 years in noncarious Class V lesions. Materials and Methods: Twenty-four patients with at least two noncarious cervical lesions were enrolled in the study. The teeth were restored with a polyacid modified resin composite (Dyract eXtra, Dentsply DeTrey) or a nanocomposite (Filtek Supreme, 3M/ESPE). Fifty restorations of each material were placed with no marginal bevels and no mechanical retentions using an antibacterial self-etching adhesive system (Clearfil Protect Bond, Kuraray). All lesions were evaluated at baseline, 6, 12, and 24 months periods using the USPHS criteria for color match, marginal discoloration, marginal adaptation, caries formation, anatomic form, postoperative sensitivity, surface roughness, and retention. The changes across the four time points were assessed using Friedman and Wilcoxon Signed Ranks tests. The two restorative materials were compared in the same recall period for each of the criteria using chi-square test (p = 0.05). Results: Dyract eXtra restorations exhibited a significantly better color match than Filtek Supreme restorations; however, all restorations in both groups were clinically acceptable. Filtek Supreme's retention rate (100%) was found to be significantly better than that of Dyract eXtra (96%). Two Dyract eXtra restorations were completely lost while one was partially fractured (p = 0.05). Significant differences were observed in marginal adaptation and color match of Filtek Supreme restorations and marginal discoloration of Dyract eXtra and Filtek Supreme restorations between the baseline and the 2-year scores (p = 0.05). Conclusion: Both restorative materials showed acceptable clinical performance in Class V noncarious lesions after 2 years of clinical service. Keywords: nanocomposite, polyacid modified resin composite, clinical trial, antibacterial adhesive, MDPB