The Journal of Adhesive Dentistry, 03/2010

Purpose: This study was conducted to evaluate the microtensile bond strength of composite resin to dentin with experimental rigid rod polymer (RRP) modified primers. RRP fillers are based on long stiff molecules specifically designed to create long polymers with restricted chain movement. Materials and Methods: Experimental primers were fabricated by dissolving RRP into dichloromethane (DCM) and further mixing it with monomers: ethylene glycol methacrylate phosphate (EGMP), bis[2-(methacryloyloxy)-ethyl]phosphate (BMEP) and 3(methacryloyloxy)propyltrimethoxysilane (MPS). Eight experimental primers were prepared with different proportions for each dentin substrate. A commercial etch-and-rinse adhesive was used as a control. Surfaces of human molar teeth were wet ground occlusally. The experimental primers were applied onto dentin prior to light polymerization of the incremental composite resin build-up. After 48 hours of water storage, teeth were sectioned and tested with the microtensile tester. Fracture surface analysis and contact angle measurements of adhesive resin were performed. Scanning electron micrographs were taken. Results: 3-way ANOVA revealed that all factors, monomer type, solvent-monomer ratio and RRP, had a significant effect (p 0.05) on bond strength. Primer with a combination of MPS and dimethacrylate BMEP revealed higher bond values than a mixture of MPS and monomethacrylate EGMP. Increase of the solvent-monomer ratio and addition of RRP into primers increased the µTBS. Conclusion: The contact angle measurements showed that RRP containing primers enhanced adhesive resin penetration into dentin similar to that of the control primer. Within the limitations of this study, it was concluded that an experimental type of modified RRP-silane-phosphate-acrylate primer was developed with comparable bonding properties to a commercial control. Keywords: adhesion, dentin, primer, rigid rod polymer

Purpose: The aim of this study was to evaluate the Knoop hardness number (KHN) of dentin and the microtensile bond strength (µTBS) at different walls of MOD preparations, and the correlation between µTBS and the KHN of dentin. Materials and Methods: Human molars with MOD preparations were allocated into 3 groups according to the preparation wall (axial, gingival, pulpal). Each tooth was sectioned into halves, resulting in two similar preparation walls: one was used for measuring the KHN of dentin and the other for µTBS testing. Flat surfaces of the respective walls were obtained by cutting away adjacent walls. For the KHN measurement, twelve indentations were performed along the preparation wall (50 g/15 s). For µTBS testing, specimens were distributed into 3 groups according to the adhesive system (Adper Single Bond Plus/SB, Clearfil SE Bond/SE, Adper Prompt/AP). Composite blocks were built over surfaces; specimens were sectioned (3 slabs/wall) and trimmed to an hourglass shape (1 mm2). Results: The KHN of dentin walls was significantly different (ANOVA/Tukey); pulpal wall > axial wall > gingival wall. The effect of preparation walls on µTBS was dependent on the bonding system (2-way ANOVA/Tukey's test). SB had higher bond strength than the other systems at the gingival wall; and higher than SE at the axial wall. At the pulpal wall, SE presented a higher mean compared to AP. A significant negative correlation between µTBS and KHN was observed at the gingival wall. Conclusion: It could be concluded that dentin structure can affect bond strengths, but the impact of the substrate varies according to the type of adhesive system. Keywords: adhesion, dentin, adhesive systems

Purpose: To evaluate the effect of different curing protocols on marginal adaptation of ceramic inlays after thermomechanical loading (TML). Materials and Methods: Forty-eight human molars were randomly divided into 6 groups (n = 8). After Class II cavity preparation (mod), ceramic inlays (Cerec) were fabricated. In groups I to IV, the cavities were conditioned with XP Bond mixed with Self Cure Activator (SCA) and the inlays were placed with the luting composite (LC) Calibra Mix (dual curing). The teeth in groups V and VI were conditioned with XP Bond without SCA and the inlays were placed with Calibra base (only light curing). In groups III, IV and V the adhesive was separately light cured prior to, and in groups II, IV, V and VI, after the inlay insertion. Before and after TML, marginal adaptation was measured using scanning electron microscopy (200X). Continuous margins (% of the total) were compared between groups using analysis of variance (ANOVA). A Bonferroni correction was applied to correct for multiple testing (α 0.005). Results: Light curing after inlay insertion improved marginal adaptation on the occlusal interface between LC and enamel significantly, regardless of the LC's curing mode. Separate light polymerization of XP Bond did not result in superior marginal quality. Investigation of the interface between LC and proximal dentin margins showed improved adaptation by dual curing the adhesive and LC, irrespecive of light application. Conclusion: Light curing after inlay insertion showed improved marginal adaptation. Using dual-curing adhesive and LC, advantages in marginal adaptation between LC and dentin were observed. Keywords: marginal adaptation, curing mode, pre-curing, dentin adhesive, ceramic inlays, insertion, loading

Purpose: To evaluate the bond strength between two fiber posts (FRC Postec and DT Light Post) and different composite resins following different surface treatments of the posts. Materials and Methods: One hundred sixty extracted teeth were divided into sixteen groups (n = 10). After pretreatment of the post surface with (1) no treatment, (2) silanization, (3) sandblasting + silanization or (4) tribochemical coating, the posts were either luted with the resin cements provided by the manufacturers of the post system or with a core buildup material. Push-out tests were performed in a universal testing machine until the post segment was dislodged from the root section. Data were analyzed using ANOVA. Multiple comparisons were performed using Tukey's test. Results: FRC Postec achieved significantly higher bond strengths than DT Light Post (p 0.0001). Cementation with the core buildup material showed significantly higher bond strengths than the resin cement provided by the post manufacturers (p 0.0001). Conclusion: Post type, type of surface treatment and type of resin cement were significant factors for bond strength. Luting with a core buildup material significantly increased the bond strengths. Keywords: fiber post, tribochemical treatment, silane, core buildup resin, push-out bond strength

Purpose: The aim of this study was to evaluate in vitro the influence of fiber reinforcement and luting cement on the static failure load (SFL) and dynamic failure load (DFL) of simulated two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). Materials and Methods: Forty-six particulate filler composite (PFC) beams and 76 fiber-reinforced composite (FRC) beams were prefabricated and subsequently luted (RelyX ARC or Panavia F2.0) onto flat ground bovine enamel. The SFL of the different specimen types was determined with a peel test and the DFL was determined with a rotating cantilever beam fatigue testing device. Results: The PFC specimens showed a significantly lower SFL than the FRC specimens. The luting cement showed a significant effect on the SFL of the PFC specimens, but not with FRC. The DFL of PFC specimens was significantly lower than for FRC specimens. The luting cement showed a significant effect on the DFL of the PFC specimens, but not so with FRC. With both the SFL and the DFL tests all PFC beams fractured, leaving the bonded part on the tooth surface, but FRC beams partially debonded from the tooth surface, leaving fibers connected to the enamel surface to a varying extent. Coincidentally, the uncured fibers turned out to be prone to aging, an effect which has been investigated. Conclusion: Within the limitations of this study, it can be concluded that PFC without fiber reinforcement is not suitable for the fabrication of two-unit cantilever RBFDPs, despite the significant effect of the luting cement, but FRC is suitable. Keywords: fiber-reinforced composite, particulate filler composite, cantilever, failure load, fatigue

Purpose: The purpose of the current study was to evaluate the effects of thione and phosphate functional monomers on bond strength and durability of a methacrylic resin luting agent joined to silver-palladium based alloy and titanium. Materials and Methods: Disk specimens of two different sizes (10 mm and 8 mm in diameter by 2.5 mm thickness) were prepared from silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy and titanium. The specimens were ground with abrasive paper, and divided into four groups based on the following conditions: 1) unprimed control; 2) priming with Alloy Primer (thione and phosphate); 3) priming with Estenia Opaque Primer (phosphate); and 4) priming with VPrimer (thione). The disks were bonded with tri-n-butylborane (TBB)-initiated resin, and shear bond strengths were determined both before and after thermocycling. Results: The Alloy Primer and V-Primer agents containing a triazine dithione monomer (VTD) bonded the Ag-Pd-Cu-Au alloy, whereas the Alloy Primer and Estenia Opaque Primer agents containing a hydrophobic phosphate monomer (MDP) bonded titanium. The reduction in bond strength after 20,000 thermocycles was not remarkable for the two groups (Alloy Primer and Ag-Pd-Cu-Au alloy; V-Primer and Ag-Pd-Cu-Au alloy). Conclusion: The thione monomer was effective in bonding the Ag-Pd-Cu-Au alloy, whereas the phosphate monomer was useful for bonding titanium. The thione did not interfere with the bonding of MDP to titanium, and MDP did not negatively affect bonding of VTD to the Ag-Pd-Cu-Au alloy. The combinations of two thione primers and the Ag-Pd-Cu- Au alloy exhibited the best adhesive performance within the limitations of the current experiment. Keywords: Ag-Pd-Cu-Au alloy, phosphate, thiol, thione, titanium

Purpose: The shear bond strength of an auto-polymerizing poly(methyl methacrylate) denture base resin material to cast titanium and cobalt-chromium alloy treated with six conditioning methods was investigated. Materials and Methods: Disk specimens (10 mm in diameter and 2.5 mm in thickness) were cast from pure titanium and cobalt-chromium alloy. The specimens were wet ground to a final surface finish of 600 grit, air dried, and treated with the following bonding systems: 1) air abraded with 50-70-µm-grain alumina (SAN); 2) air abraded with 50-70-µm-grain alumina + conditioned with Alloy Primer (ALP); 3) air abraded with 50-70-µm-grain alumina + conditioned with AZ Primer (AZP); 4) air abraded with 50-70-µm-grain alumina + conditioned with Estenia Opaque Primer (EOP); 5) air abraded with 50-70-µm-grain alumina + conditioned with Metal Link Primer (MLP), and 6) treated with ROCATEC system (ROC). A denture base material (Palapress Vario) was then applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles. Results: The strengths decreased after thermocycling in all combinations. Among the treatment methods assessed, groups 2 and 4 showed significantly (p 0.05) enhanced shear bond strengths for both metals. In group 4, the strength in MPa (n = 7) after thermocycling for cobalt-chromium alloy was 38.3, which was statistically (p 0.05) higher than that for cast titanium (34.7). Conclusion: Air abrasion followed by the application of two primers containing a hydrophobic phosphate monomer (MDP) effectively improved the strength of the bond of denture base material to cast titanium and cobalt-chromium alloy. Keywords: cobalt-chromium, denture base material, primer, poly(methyl methacrylate), shear bond strength, titanium

Purpose: To compare the effects of quartz-tungsten-halogen (QTH) and light-emitting-diode (LED) curing units on the 3-year clinical performance of a nanofilled composite resin in noncarious cervical lesions. Materials and Methods: Twenty-six patients with at least 2 noncarious cervical lesions were enrolled in the study. A total of 154 restorations were placed: half polymerized with QTH and half polymerized with LED. Single Bond was used as the adhesive and Filtek Supreme was used as the restorative material for all restorations. The restorations were assessed by two different examiners using modified Ryge/USPHS criteria at baseline and at 6, 12, 24, and 36 months. The survival rates were analyzed with the Kaplan-Meier estimator and the Log-Rank test, and the statistical analysis was completed using Pearson's chi-square test (p 0.05). Results: Twenty patients were available for recall after 3 years and 114 restorations were evaluated (recall rate of 74%). The survival rate was 84% for QTH and LED polymerized restorations. There were no statistically significant differences in survival rates between the light-curing units (p > 0.05). No significant differences were observed between QTH and LED polymerized restorations in terms of any of the evaluation criteria at the end of 3 years (p > 0.05). No color change in the restorations was observed and none of them exhibited secondary caries at the end of 3 years. Conclusion: Over the 3-year study period, both curing units, QTH and LED, produced acceptable clinical results in noncarious cervical lesions. Keywords: light-curing unit, composite resin, clinical evaluation

Purpose: This longitudinal randomized controlled clinical trial evaluated direct composite restorations for clinical acceptability as posterior restoratives in single- or multi-surface cavities and provides a survey of the 4-year results. Materials and Methods: Three dentists placed 46 Quixfil (Xeno III) and 50 Tetric Ceram (Syntac Classic) composite restorations in stress-bearing Class I and II cavities in first or second molars (43 adult patients). Clinical evaluation was performed at baseline and after 4 years by 2 other dentists using modified USPHS criteria. At the last recall period, 37 Quixfil and 46 Tetric Ceram restorations were assessed. Results: A total of 89.2% of Quixfil and 97.8% of Tetric Ceram posterior composites were assessed to be clinically excellent or acceptable with predominating alfa scores. Up to the 4-year recall, four Quixfil restorations failed because of bulk fracture, partial tooth fracture (2x) and postoperative symptoms. One Tetric Ceram restoration was lost due to problems with tooth integrity. No significant differences between the two composites could be detected at 4 years for any of the evaluated clinical criteria (p > 0.05). The comparison of restoration performance with time within both groups yielded a significant increase in marginal discoloration and decrease in marginal integrity for both materials. After 4 years, small restorations exhibited significantly less marginal discoloration than large restorations. Conclusion: Clinical assessment of stress-bearing Quixfil and Tetric Ceram posterior composite restorations showed good clinical results with predominantly alfa scores for both materials. Keywords: composite, molars, clinical study, longevity, USPHS criteria