The Journal of Adhesive Dentistry, 04/2009

Purpose: To compare the shear bond strength of stainless steel brackets bonded with two orthodontic adhesive systems, Transbond XT (3M Unitek) and Orthobond (Morelli Dental Products). Materials and Methods: Forty bovine teeth were randomly divided in two groups of 20 each: group 1 (control): Transbond XT primer + Transbond XT Adhesive paste (3M Unitek); group 2: Orthoprimer (Morelli Dental Products) + Orthobond. In each group all teeth were etched with 37% phosphoric acid, and all products were used according to manufacturers instructions. After 30 min, a universal testing machine was used to apply an occlusal shear force directly to the enamel/bracket interface at a speed of 0.5 mm/min. The groups were compared using Student's t-test. Results: Mean results and standard deviations for the groups were: group 1= 11.22 Mpa (1.68), group 2= 4.88 Mpa (1.18). A significant difference was observed in the bond strengths of the two groups evaluated (p 0.0001). Conclusion: Under the conditions of this study, Orthobond system presented lower shear bond strength when compared to Transbond XT. Keywords: acid etching, bonding, brackets, orthodontics

Purpose: The aim of this in vitro study was to investigate the surface properties and in vitro adhesion of Streptococcus mutans to dental self-etching two-step adhesives using an artificial mouth system. Materials and Methods: Carriers of a denture base resin supplemented with hydroxyapatite were manufactured, polished, and surface treated with various two-step self-etching dental adhesives (Clearfil Protect Bond, Silorane System Adhesive, Adper Scotchbond SE) according to the manufacturers' instructions. For each adhesive, 14 samples were inserted in an artificial mouth system and successively rinsed with mucin solutions (2 h) and Streptococcus mutans NCTC 10449 suspension (4 h). Surface free energy of the specimens was determined before and after mucin coating. The amount of adhered bacteria was quantified using a fluorescent dye (Resazurin/Alamar Blue) for viable cell quantification. Results: Before mucin coating, significant differences in surface free energies were found between the various adhesives, with total surface free energies ranging from 34.26 mJ/m-2 to 42.30 mJ/m-2. Mucin coating clearly levelled surface free energy differences. Significantly lower fluorescence intensities, indicating lower adhesion of Streptococcus mutans, were found for Silorane System Adhesive than for Clearfil Protect Bond and Adper Scotchbond SE, regardless of mucin coating. Discussion: The findings of this in vitro study indicate that the initial adhesion of Streptococcus mutans is lower to Silorane System Adhesive than to Clearfil Protect Bond or Adper Scotchbond SE. Our data correlated with the common thermodynamic approaches explaining streptococcal adherence to solid surfaces.

Purpose: This in vitro study evaluated the amount and distribution of outward fluid flow that occurred when an experimental etch-and-rinse hydrophobic adhesive was applied to ethanol-saturated dentin before and after oxalate pretreatment. Materials and Methods: Measurements of dentin permeability were performed under a constant pulpal pressure of 20 cm H2O in deep and middle dentin. A lucifer yellow solution was placed in the pulp chamber to determine the distribution of the water contamination of the hybrid layers. Results: The distribution of fluorescence in dentin specimens that were not pretreated with oxalate revealed that the dye permeated around the resin tags and filled the hybrid layer. Dentin specimens pretreated with oxalate prior to resin bonding, showed 80% to 83% less (p 0.05) water contamination compared to controls. The dentin permeability results obtained before and after oxalate pretreatment showed that oxalate decreased dentin permeability by 98% (p 0.05) compared to acid-etched controls. This prevented outward fluid movement during bonding, resulting in better resin sealing of dentin due to the formation of a double seal of resin tags over calcium oxalate crystals in the tubules. Conclusion: Outward dentinal fluid flow may contaminate hybrid layers during adhesive bonding procedures. Pretreatment of acid-etched dentin with 3% oxalic acid prior to bonding procedures can prevent outward fluid flow during bonding and water contamination of the hydrophobic hybrid layers. Keywords: water contamination, two-photon confocal microscopy, ethanol-saturated dentin, hydrophobic hybrid layer, dentin permeability

Purpose: To assess the influence of variations in the application technique of self-etching adhesive systems on the adhesive bond strength to enamel. Materials and Methods: One hundred thirty bovine teeth were used and divided into 13 groups. The teeth were embedded in acrylic resin, ground until a flat enamel area was exposed, and polished with 600-grit abrasive paper. The self-etching adhesive systems One Up Bond F, Clearfil SE Bond, Self & Etch were used, and the conventional adhesive Magic Bond and acid etching were used as the control group. One or two layers of the self-etching systems were actively or passively applied. Composite cylinders were made over the bonding area. The samples were submitted to shear bond testing at a speed of 1 mm/min. Statistical analysis of the data was performed using two-way ANOVA, followed by Tukey's test at a 5% level of significance. Results: Significant variations were observed for the factors type of adhesive (p = 0.001, F = 193,3594, df = 3) and application technique (p = 0.001, F = 29,9119, df = 1). No significant interaction was found between the two factors (p = 0.08). The adhesives Clearfil SE Bond and One Up Bond F presented significantly higher adhesive bond strength means than Self & Etch. The active application of two layers resulted in higher bond strength means than the other techniques. Conclusion: The application technique had a significant influence on adhesive bond strength to enamel. Keywords: self-etching adhesives, enamel, bond strength

Purpose: To evaluate the effects of gaseous ozone application on enamel and dentin bond strength produced by two self-etching adhesive systems. Materials and Methods: The shear bond strength test was conducted to assess adhesion on enamel (protocol 1), while the microtensile bond strength test was performed on dentin (protocol 2). Protocol 1: 96 bovine incisors were randomly divided into 4 groups, and enamel surfaces were bonded in accordance with the following treatments: (1E) ozone + Clearfil Protect Bond; (2E) Clearfil Protect Bond (control); (3E) ozone + Xeno III; (4E) Xeno III (control). Ozone gas was applied for 80 s. Shear bond strength was measured with a universal testing machine. Protocol 2: 40 noncarious human molars were selected. Middle/deep dentin was exposed and bonded in accordance with the following treatments: (1D) ozone+Clearfil Protect Bond; (2D) Clearfil Protect Bond (control); (3D) ozone+Xeno III (4D) Xeno III (control). Four-mm-thick buildups were built on the adhesives, then specimens were sectioned in accordance with the nontrimming technique. Specimens were stressed until failure occurred, and failure modes were analyzed. Shear bond and microtensile bond strength data were analyzed using two-way ANOVA and Tukey's post-hoc test. Results: No statistical differences were found between ozone treated specimens and controls, neither on enamel nor on dentin irrespective of the tested adhesive. Clearfil Protect Bond showed higher bond strength to enamel than Xeno III, irrespective of the ozone treatment (p 0.05). Conclusion: The use of ozone gas to disinfect the cavity before placing a restoration had no influence on immediate enamel and dentin bond strength. Keywords: ozone, dental bonding systems, dentin, enamel, bond strength

Purpose: To evaluate the effect of a novel antibacterial and fluoride-releasing adhesive formulation on enamel demineralization under sucrose exposure in situ (simulating high caries risk conditions). Materials and Methods: This crossover, blind study was performed in two phases of 14 days. Volunteers (n = 14) wore an intraoral appliance containing four bovine enamel blocks with cavity preparations restored using self-etching primers/composite resin (Clearfil SE Bond or Clearfil Protect Bond/Clearfil AP-X). The volunteers dropped 20% sucrose solution 8x/day and used fluoridated dentifrice 3x/day. After 14 days, enamel mineral loss was assessed by cross-sectional microhardness (CSMH), and the demineralization areas in enamel adjacent to the restoration were examined by scanning electron microscopy (SEM) and polarizing light microscopy (PLM). The CSMH data were analyzed using ANOVA and Tukey's test (p 0.05). Results: Enamel blocks restored with Clearfil Protect Bond showed higher mineral content (%vol) adjacent to restorations than Clearfil SE Bond only for the first site of microhardness measurement and close to enamel surface (20 µm). SEM and PLM analysis suggested that the Clearfil Protect Bond adhesive promoted less enamel demineralization around restorations. Conclusion: After 14 days of cariogenic challenge, the findings suggested that Clearfil Protect Bond might help to control the demineralization around restorations in cases of high caries risk. Keywords: adhesive systems, enamel, microhardness, microscopy

Purpose: The effect of three different bonding strategies on the shear bond strength of a resin composite to fluorotic enamel surfaces was investigated. Materials and Methods: Thirty-six noncarious extracted human molars with fluorosis and 36 without fluorosis were scraped clean from any remaining tissue, and then were divided into three subgroups according to the tested dentin bonding systems. The resin composite was bonded to the teeth using three different adhesive systems: Peak LC Bond with an etch-and-rinse technique (Ultradent Products), Peak LC Bond with a self-etching technique using Peak SE Primer (Ultradent Products), and Xeno V (Dentsply Caulk) using a one-bottle self-etching technique. Following the photopolymerization of the resin composites, thermocycling was performed 5000 times. Shear bond strengths were tested using the Shimadzu Universal Testing Machine until failure. The analysis of the fractured enamel surfaces was performed using an optical microscope (Nikon ECLIPSE ME 600) at 10X and 1000X magnification, and the images were analyzed with an image analyzer (LUCIA 4.21). The data obtained were analyzed with two-way ANOVA and the Bonferroni test at a significance level of p 0.05. Results: Mean shear bond strengths in MPa of the groups were: Peak LC Bond, self-etching, on fluorotic enamel 13.23 ± 2.58 and on nonfluorotic enamel 17.81 ± 2.90; Peak LC Bond, etch-and-rinse, on fluorotic enamel 16.77 ± 2.32 and on nonfluorotic enamel 21.13 ± 2.74; one-bottle self-etching Xeno V on fluorotic enamel 10.79 ± 2.14 and on nonfluorotic enamel 14.58 ± 2.99. Conclusion: Fluorosis adversely affected the bonding performance of all the bonding systems to enamel. The use of the etch-and-rinse dentin bonding technique produced higher bond strengths of the resin composite tested to fluorotic and nonfluorotic enamel compared to both self-etching techniques. Keywords: fluorosis, resin composites, shear bond strength, enamel bonding

Purpose: The aim of this in vitro study was to evaluate the effect of radiotherapy on the microleakage of three adhesive systems: a one-step self-etching, a two-step self-etching, and an etch-and-rinse system. Materials and Methods: Box-shaped Class V cavity preparations were prepared on the buccal surfaces of 84 extracted human molars. The molars were randomly assigned into 6 groups (n = 14) according to the irradiation and adhesive system as follows: G1, Clearfil S3 Bond (irradiated); G2, Clearfil SE Bond (irradiated); G3, Prime & Bond NT (irradiated); G4, Clearfil S3 Bond (nonirradiated); G5, Clearfil SE Bond (nonirradiated); and G6, Prime & Bond NT (nonirradiated). The cavities were restored with composite resin (Filtek Z 250). After restoration of the samples, a total dose of 60 Gy was delivered in 2 Gy/d fractions for 5 days per week for 6 weeks for the related groups. All specimens were thermocycled for 200 cycles between 5°C and 55°C using a dwell time of 60 s in each bath and then placed in 0.5% basic fuchsin solution for 24 h at room temperature. Specimens were then rinsed and sectioned; the dye penetration at the enamel and dentin margins was examined using a stereomicroscope, and a score of 0 to 3 was assigned. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U-tests. Results: No statistically significant difference existed between the irradiated and nonirradiated groups (p > 0.05). Significant differences in microleakage were observed between enamel and dentin (p 0.01). The microleakage at the dentin margins was greater than at the enamel margins. Prime & Bond NT revealed statistically significantly (p 0.05) higher leakage scores in dentin than did ClearfilS3 Bond and Clearfil SE Bond. Conclusion: Within the limitations of this study, irradiation application did not affect the microleakage of dental adhesive systems. Keywords: dental adhesives, irradiation, radiotherapy, microleakage

Purpose: To test the influence of thermomechanical loading and mode of cleaning the pulp chamber on coronal microleakage of adhesive sealings over root canal fillings. Materials and Methods: Root canals of molars were instrumented to size 60 taper .02 and filled with AH plus (Dentsply DeTrey) and a single gutta-percha cone size 55 taper .02. After removal of residual sealer with an alcoholmoistened foam pellet, different pretreatments were performed: groups 1 and 5: no further pretreatment; groups 2 and 6: use of a water cooled high-speed diamond bur; groups 3 and 7: etch-and-rinse with 37% H3PO4 for 10 s; groups 4 and 8: diamond bur and etching. Then Syntac (Ivoclar Vivadent) and two consecutive layers of Tetric flow (Ivoclar Vivadent) were applied. After placing glass-ionomer cement as a provisional restoration, teeth of groups 5 to 8 were additionally subjected to thermomechanical loading (chewing simulation of 200,000 cycles/50 N) and thermocycling (2880 cycles between 5°C and 55°C). A dye penetration test (methylene blue dye 5%, centrifugation for 3 min at 30 G) was used to evaluate linear dye penetration and dye penetration area. Statistical tests were performed using SPSS Win 12.0 (Kolmogorov-Smirnov test, two-way ANOVA, t-test). Results: Thermomechanical loading (TML) had a negative impact on coronal seal (two-way ANOVA, p 0.001). Among TML groups, group 7 (etch-and-rinse) performed best, exhibiting the least influence of TML. Conclusion: For adhesive sealing of the pulp chamber floor, the etch-and-rinse technique combined with a flowable resin composite showed promising results. Nevertheless, a stabilizing restoration should be placed as soon as possible. Keywords: AH plus, dentin bonding, root canal filling, secondary protective seal, Syntac, Tetric flow, thermomechanical loading

Purpose: To evaluate the effect of three different root canal pretreatments on the retention of prefabricated titanium posts luted in the root canal with one of three resin cements. Materials and Methods: After removal of the clinical crowns of 216 extracted premolars, the root canals were prepared with the ParaPost system (length = 5 mm, diameter = 1.25 mm). The walls of the roots were subjected to either none (control) or one of three pretreatments: etching with citric acid, application of EDTA C, or mechanical roughening with a diamond-coated bur (n = 18 per group). CoJet-treated ParaPost XH posts were luted in the root canals with one of three resin cements: Panavia 2.0 F, Rely X Unicem, or ParaCem. Following water storage at 37°C for 7 days, retention was determined by extraction of the posts. Results: Mechanical roughening of root canal walls resulted in improved retention of posts, irrespective of the type of resin cement. Etching of root canal walls with citric acid resulted in improved retention only when Panavia 2.0 F was used. Depending on the resin cement, application of EDTA C had either no effect or a negative effect. Luting of posts with Panavia 2.0 F resulted in higher retention than did luting with Rely X Unicem or ParaCem. Conclusion: Mechanical roughening of the root canal walls with a diamond-coated bur was the most effective method to improve retention of posts. The use of Panavia 2.0 F resulted in higher retention than did the use of Rely X Unicem or ParaCem. Keywords: dowel, cementation, luting

Purpose: To investigate the effects of an interfacial fiber-reinforced resin-based material (FRRM) application and different light-curing modes on the bond strength of a thermoplastic synthetic polymer-based root canal filling material (Resilon) to a methacrylate-based sealer (Epiphany). Materials and Methods: One hundred Resilon disks were prepared and divided into two experimental groups: 1. application of FRRM (EverStick Net) on the Resilon surface, and 2. Resilon alone (control). Following subsequent application of the Epiphany sealer, the specimens were randomly assigned into 3 subgroups according to the curing method employed: 1. chemical curing, 2. quartz-tungsten-halogen (QTH) light, and 3. light-emitting diode (LED). The latter two groups were further subdivided to test the effects of two different polymerization modes for each light-curing unit. Cured specimens were subjected to shear bond strength testing and the failure modes were examined. The data were analyzed with three-way analysis of variance (ANOVA). Results: Regardless of the curing method tested, application of FRRM at the interface significantly increased the bond strength of Resilon to Epiphany (p 0.001). Bond strength values (MPa) were as follows (mean ± SD): 1. chemical curing with FRRM= 3.0 ± 0.4, without FRRM = 1.2 ± 0.3; 2. QTH: a) standard mode with FRRM = 8.6 ± 0.6, without FRRM = 5.5 ± 0.9; b) ramp mode with FRRM = 8.0 ± 1.0, without FRRM = 5.3 ± 1.4; 3. LED: a) standard mode with FRRM = 8.8 ± 1.1, without FRRM = 5.4 ± 1.0; b) exponential mode with FRRM = 8.5 ± 1.0, without FRRM = 4.6 ± 0.6. Although light curing of specimens significantly increased the bond strength of Resilon to Epiphany (p 0.001), the type of light-curing unit and different curing modes had no significant influence on bond strength (p = 0.852 and p = 0.776, respectively). Conclusion: The highest bond strength values were obtained when the FRRM was used at the interface and the sealer was light cured. Keywords: bond strength, Epiphany, fiber-reinforced resin-based material, light curing modes, Resilon