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.

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 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.

Evaluation of the effects of fluoride-releasing varnish on dentin demineralization using optical coherence tomography.

Effects of a fluoride-releasing varnish containing surface reaction-type prereacted glass ionomer (S-PRG) filler on dentin demineralization were examined using optical coherence tomography. Bovine incisors that were sliced and treated with undersaturated 0.1 M lactic acid buffer solution (DE group). A thin film of varnish-containing S-PRG filler was applied before demineralization (PRG group). Control was maintained in artificial saliva. Using optical coherence tomography of selected locations on the dentin surface, peak intensity (dB) and width (µm) at 1/e(2) were obtained and integrated values calculated. Although alterations in integrated values were different in each group, there was a slight but not significant increase in those for the control group and a slight but significant increase for the De group. For the PRG group, integrated values were doubled seven days after experiment initiation, followed by a significant increase. Fluoride-releasing varnish containing S-PRG fillers prevented dentin demineralization as detected by optical coherence tomography.

Optical coherence tomography examination of the effect of S-PRG filler extraction solution on the demineralization of bovine enamel.

The purpose of this study was to determine the effect of PRG filler extraction solution on the demineralization of enamel using optical coherence tomography (OCT). Bovine enamel was treated with lactic acid buffer solution and then placed in artificial saliva (De group). In the second group, specimens were stored in PRG filler extraction solution followed by immersion in lactic acid buffer solution (PRG group). In the control group, specimens were simply stored in artificial saliva. From the OCT image, the peak intensity (dB) and width at (1/e(2)) were obtained, and the integrated value was calculated. The data were analyzed using Tukey-Kramer tests (α=0.05). There was a slight but significant increase in the integrated value observed for the control group, and a slight but significant decrease in the value observed for the De group. For the PRG group, integrated values were doubled after seven days from the start of the experiment.

Influence of tooth-surface hydration conditions on optical coherence-tomography imaging.

OBJECTIVES: This study examined the influence of tooth-surface hydration conditions on optical coherence tomography (OCT) imaging. METHODS: Emitted light was coupled in a single-mode fibre-optic Michelson interferometer, and delivered to a sample and a reference mirror mounted on a linearly translating galvanometer driven by a triangular voltage waveform at a fringe-modulation frequency of 1kHz. Backscattered light from the sample was coupled back to the system, digitised and used to create two-dimensional images together with beam scanning. OCT imaging of the occlusal surfaces of 10 extracted human teeth was performed soon after mounting ('wet' condition), immediately after air blowing for 10s ('air-blow' condition), and at intervals thereafter ('1-min', '5-min' and '10-min' conditions, respectively). RESULTS: For the wet condition, three distinct peaks indicated the water surface, tooth surface and dentino-enamel junction. Backscattered light was detected at levels above noise, possibly causing grainy OCT images. By contrast, two distinct peaks indicating the tooth surface and dentino-enamel junction were observed for the air-blow and 10-min conditions, with greater signal intensities for the latter. The intensity was lower for the air-blow condition than the wet condition. The signal intensities decreased during storage in air at room temperature. CONCLUSION: Tooth-substrate hydration conditions thus appeared to influence time domain-OCT imaging.

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 Tukey's Honestly Significant Difference (HSD) test and Dunnett's 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.

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 Tukey's 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.

Changes in elastic modulus of adhesive and adhesive-infiltrated dentin during storage in water.

The purpose of this study was to determine the elastic modulus of components at the resin-dentin interface with the use of an ultrasound device. Dentin slabs were obtained from freshly extracted bovine incisors shaped into a rectangular form. After demineralization, the dentin specimens were immersed in adhesives and polymerized. Adhesives were also polymerized and trimmed into the same shape as the dentin slabs. The specimens were then immersed in distilled water at 37 degrees C for up to one year. The ultrasound equipment employed in this study was a Pulser-Receiver, transducers and an oscilloscope. By measuring the longitudinal and shear wave sound velocities, the elastic modulus was determined. When the elastic modulus of adhesive resin-infiltrated demineralized dentin was compared with that of adhesives, slightly but significantly lower values were found for adhesives used in a self-etching primer system. On the other hand, a higher elastic modulus was observed for resin-infiltrated dentin than for an adhesive used in an etch and rinse system. The elastic modulus of the resin-infiltrated dentin prepared with the etch and rinse system was affected by long-term storage in distilled water.

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.