Yutaka Shimamura

Enamel bonding of single-step self-etch adhesives: Influence of surface energy characteristics

OBJECTIVES This study examined the surface free energy of enamel treated with the single-step self-etching adhesives Bond Force, Clearfil tri-S Bond and G-Bond. METHODS The labial enamel surfaces of bovine mandibular incisors were wet ground with #180-grit, #600-grit and #2000-grit silicon carbide paper. The adhesives were applied to the ground enamel, and then rinsed with acetone and distilled water. The surface free energies were determined by measuring the contact angles of three test liquids placed on the adhesive-treated enamel. The data for each adhesive system were analyzed using analysis of variance and Tukeys honestly significant difference test. RESULTS The surface free energies of the samples treated with the G-Bond and tri-S Bond adhesives increased as the surface roughness decreased. No significant differences in the surface free energy were found for the samples treated with the Bond Force adhesive regardless of the surface roughness. CONCLUSION The results indicated that the surface free energies and their components of the treated enamel surfaces were different among the adhesive systems used.

Influence of surface treatment of contaminated zirconia on surface free energy and resin cement bonding

Influences of contamination and cleaning methods on the bonding of resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (IPS e.max ZirCAD) specimens were contaminated with saliva and cleaned with tap water (SC) or by application of 37% phosphoric acid (PA), Ivoclean (IC), or additional airborne particle abrasion (AB). Specimens without contamination served as controls. After application of Monobond Plus to the surface of the specimens, resin cement was mixed and inserted into a mold. Surface free energies of the specimens were determined by measuring contact angles. Surface treatment and storage conditions significantly influenced bond strength, while there was no significant interaction between the two factors. Surface free energies of the SC and IC groups were significantly lower than those of the other groups. Additional AB of saliva-contaminated zirconia increased the strength of bonding with the resin cement as well as increased surface free energy.

Change in elastic modulus of bovine dentine with exposure to a calcium hydroxide paste.

OBJECTIVE To determine the effect of calcium hydroxide [Ca(OH)(2)] paste exposure on the elastic modulus of bovine dentine. METHODS Dentine sections (4 mm x 4 mm x 1 mm) were obtained from freshly extracted bovine incisors and placed in dishes containing a 1-mm deep layer of Ca(OH)(2) paste or physiological saline as a control. An ultrasonic device was used to measure the sonic velocities of the longitudinal and shear waves, and the elastic modulus was calculated. Data were examined by analysis of variance followed by the Tukey H.S.D. test in order to compare different storage times. RESULTS Exposure to Ca(OH)(2) paste significantly increased the mean elastic modulus of the dentine from 16.3 to 22.1 GPa. By contrast, the elastic modulus of the control dentine, which was exposed to physiological saline, remained constant. CONCLUSION These results demonstrate that exposure to Ca(OH)(2) paste increases the elastic modulus of dentine, thereby making it more prone to fracture.

pH changes upon mixing of single-step self-etching adhesives with powdered dentin.

PURPOSE Single-step self-etching adhesives have been developed as a bonding material that adheres to the tooth surface. The adhesives contain acidic resin monomers that penetrate the dentin but can be neutralized to stop the reaction. This study aimed to improve understanding of the pH changes that occur when self-etching adhesives are mixed with dentin powder. MATERIALS AND METHODS Dentin disks obtained from extracted bovine incisors were milled and pulverized into a fine powder. The powder was mixed with diluted self-etching adhesives, and pH changes were measured by a solid-state pH sensor connected to a pH meter at various time points after the start of mixing. Data were analyzed by Tukeys Honestly Significant Difference (HSD) test and Dunnetts test at a significance level of 0.05. Precipitates from the adhesive/ dentin powder mixture were observed by scanning electron microscopy (SEM). RESULTS The baseline pH values of the self-etching adhesives ranged from 0.97 to 2.83. After mixing with the dentin powder, the pH values significantly increased, ranging from 6.30 to 7.11 at 180 s after mixing. SEM observation revealed products of the reaction between dentin powder and self-etching adhesive which indicate a chemical reaction between the functional monomer and dentin. CONCLUSION Dentin has a strong modulation effect against the acidity of self-etching adhesives.

Influence of Degradation Conditions on Dentin Bonding Durability of Three Universal Adhesives

OBJECTIVES This study aims to determine dentin bonding durability of universal adhesives using shear bond strength (SBS) tests under various degradation conditions. METHODS G-Premio Bond (GP, GC), Scotchbond Universal (SU, 3M ESPE) and All Bond Universal (AB, Bisco) were compared with conventional two-step self-etch adhesive Clearfil SE Bond (SE, Kuraray Noritake Dental). Bonded specimens were divided into three groups of ten, and SBSs with bovine dentin were determined after the following treatments: 1) Storage in distilled water at 37°C for 24h followed by 3000, 10,000, 20,000 or 30,000 thermal cycles (TC group), 2) Storage in distilled water at 37°C for 3 months, 6 months or 1year (water storage, WS group) and 3) Storage in distilled water at 37°C for 24h (control). RESULTS SE bonded specimens showed significantly higher SBSs than universal adhesives, regardless of TC or storage periods, although AB specimens showed significantly increased SBSs after 30,000 thermal cycles. In comparisons of universal adhesives under control and degradation conditions, SBS was only reduced in SU after 1year of WS. CONCLUSION Following exposure of various adhesive systems to degradation conditions of thermal cycling and long term storage, SBS values of adhesive systems varied primarily with degradation period. CLINICAL SIGNIFICANCE Although universal adhesives have lower SBSs than the two-step self-etch adhesive SE, the present data indicate that the dentin bonding durability of universal adhesives in self-etch mode is sufficient for clinical use.

Influence of air-powder polishing on bond strength and surface-free energy of universal adhesive systems

The influences of air-powder polishing with glycine or sodium bicarbonate powders on shear bond strengths (SBS) and surface-free energies of universal adhesives were examined. Scotchbond Universal Adhesive (SU, 3M ESPE), G-Premio Bond (GP, GC), Adhese Universal (AU, Ivoclar Vivadent), and All-Bond Universal (AB, Bisco) were used in this study. Bovine dentin surfaces were air polished with glycine or sodium bicarbonate powders prior to the bonding procedure, and resin pastes were bonded to the dentin surface using universal adhesives. SBSs were determined after 24-h storage in distilled water at 37°C. Surface-free energy was then determined by measuring contact angles using three test liquids on dentin surfaces. Significantly lower SBSs were observed for dentin that was air-powder polished and surface-free energies were concomitantly lowered. This study indicated that air-powder polishing influences SBSs and surface-free energies. However, glycine powder produced smaller changes in these surface parameters than sodium bicarbonate.