Milk and milk products, such as cheese, have been shown to exhibit anticariogenic properties in human and animal models. CPP-ACP shows an anti-caries effect by suppressing demineralization, enhancing remineralization, or possibly a combination of both. The purpose of this study was to evaluate the effect of CPP-ACP paste on demineralization by observing the treated tooth surface using an FE-SEM. The specimens were prepared by cutting enamel and dentin of bovine teeth into blocks. A few specimens were stored in 0.1 M lactic acid buffer solution for 10 min and then in artificial saliva (negative control). The remaining specimens were stored in a 10 times-diluted solution of CPP-ACP paste or a placebo paste containing no CPP-ACP for 10 min, followed by 10 min immersion in a demineralizing solution (pH = 4.75, Ca) twice a day before storage in artificial saliva. After treatment of the specimens for 3, 7, 21 and 28 days, they were fixed in 2.5% glutaraldehyde in cacodylate buffer solution, dehydrated in ascending grades of tert-butyl alcohol, and then transferred to a critical-point dryer. The surfaces were coated with a thin film of Au in a vacuum evaporator, and were observed under field emission-scanning electron microscopy (FE-SEM). The SEM observations revealed different morphological features brought about by the various storage conditions. Demineralization of the enamel and dentin surfaces was more pronounced with the longer test period in the control and negative control specimens. On the other hand, enamel and dentin specimens treated with CPP-ACP paste revealed slight changes in their morphological features. From the morphological observations of the enamel and dentin surfaces, it could be considered that the CPP-ACP paste might prevent demineralization of the tooth structure.

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.

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There is a need for effective polishing instruments for resin composite restorations with highly polished surfaces. The purpose of this study was to investigate the influence of polishing duration on surface roughness of light-cured resin composites. Four polishing systems, Compomaster (Shofu), Silicone Points C Type (Shofu), Super Snap (Shofu) and Enhance Finishing and Polishing System (Dentsply/Caulk), were used to polish two commercially available resin composites, Clearfil AP-X (Kuraray Medical) and Lite-Fil II A (Shofu). Resin pastes were condensed into molds (10 mm in diameter, 5 mm in depth) and light irradiated for 40 s. Composite surfaces were ground with # 600 SiC paper followed by polishing with an instrument for 30 s, and the surface roughness was measured every 10 s during polishing procedures. The average surface roughnesses (Ra) were determined using a profilometer. Data were analyzed by Tukey HSD test (P = 0.05). After 30 s of polishing, mean Ra values ranged from 0.07 to 0.50 for Clearfil AP-X, and from 0.11 to 0.57 for Lite-Fil II A. Although the time required for polishing was longer, the surface finish produced by multiple-step polishing systems was superior to that obtained with one-step polishing systems.

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The wear and mechanical properties of the flowable resin composites tested suggested improved performance compared with universal resin composites.

The purpose of this study was to determine the enamel bond durability of three universal adhesives in different etching modes through fatigue testing. The three universal adhesives used were Scotchbond Universal, Prime&Bond Elect universal dental adhesive, and All-Bond Universal light-cured dental adhesive. A single-step self-etch adhesive, Clearfil S Bond Plus was used as a control. The shear bond strength (SBS) and shear fatigue strength (SFS) to human enamel were evaluated in total-etch mode and self-etch mode. A stainless steel metal ring with an internal diameter of 2.4 mm was used to bond the resin composite to the flat-ground (4000-grit) tooth surfaces for determination of both SBS and SFS. For each enamel surface treatment, 15 specimens were prepared for SBS and 30 specimens for SFS. The staircase method for fatigue testing was then used to determine the SFS of the resin composite bonded to the enamel using 10-Hz frequencies for 50,000 cycles or until failure occurred. Scanning electron microscopy was used to observe representative debonded specimen surfaces and the resin-enamel interfaces. A two-way analysis of variance and the Tukey post hoc test were used for analysis of the SBS data, whereas a modified t-test with Bonferroni correction was used for the SFS data. All adhesives in total-etch mode showed significantly higher SBS and SFS values than those in self-etch mode. Although All-Bond Universal in self-etch mode showed a significantly lower SBS value than the other adhesives, there was no significant difference in SFS values among the adhesives in this mode. All adhesives showed higher SFS:SBS ratios in total-etch mode than in self-etch mode. With regard to the adhesive systems used in this study, universal adhesives showed higher enamel bond strengths in total-etch mode. Although the influence of different etching modes on the enamel-bonding performance of universal adhesives was found to be dependent on the adhesive material, total-etch mode effectively increased the enamel bond strength and durability, as measured by fatigue testing.