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Objectives: Materials that can be applied as thin coatings and actively release fluoride or other bioavailable ions for reinforcing dental hard tissue deserve further investigation. In this study we assessed the potential of resin coating materials in protection of underlying and adjacent enamel against demineralization challenge using nanoindentation., Methods: Enamel was coated using Giomer (PRG Barrier Coat, PBC), resin-modified glass-ionomer (Clinpro XT Varnish, CXT), two-step self-etch adhesive (Clearfil SE Protect, SEP) or no coating (control). After 5000 thermal cycles and one-week demineralization challenge, Martens hardness of enamel beneath the coating, uncoated area and intermediate areas was measured using a Berkovich tip under 2mN load up to 200μm depth. Integrated hardness and 10-μm surface zone hardness were compared among groups., Results: Nanoindentation and scanning electron microscopy suggested that all materials effectively prevented demineralization in coated area. Uncoated areas presented different hardness trends; PBC showed a remarkable peak at the surface zone before reaching as low as the control, while CXT showed relatively high hardness values at all depths., Significance: Ion-release from coating materials affects different layers of enamel. Coatings with fluoride-releasing glass fillers contributed to reinforcement of adjacent enamel. Surface prereacted glass filler-containing PBC superficially protected neighboring enamel against demineralization, while resin-modified glass-ionomer with calcium (CXT) improved in-depth protection. Cross-sectional hardness mapping of enamel on a wide range of locations revealed minute differences in its structure., (Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Optical coherence tomography (OCT) is an interferometric imaging technique. This study aimed to employ OCT to evaluate four different resin-based materials including a coating containing glass-ionomer filler and calcium, a giomer, and two fluoride-releasing self-etch resins. The coating and its underlying and adjacent enamel were monitored using swept-source OCT (center wavelength: 1330 nm) at baseline, after 5,000 thermal cycles, and after 1, 4 and 7 days of demineralization (pH 4.5). The coatings showed different thicknesses (60-250 micrometers) and various levels of structural and interfacial integrity. OCT could detect a demineralization inhibition zone adjacent to the edge of the fluoride- and calcium-releasing material. Localized demineralization was occasionally observed under thinner coatings. Protection of susceptible enamel surfaces by thin resin-based bioactive coatings provides protection from demineralization. OCT can be used to non-destructively monitor the integrity of such coatings, as well as enamel changes beneath and adjacent to them.

Objectives: This study investigated class-I cavity floor adaptation by swept-source optical coherence tomography (OCT) in combination with microtensile bond strength (MTBS) using different filling methods., Methods: Two adhesive systems; Tokuyama Bond Force and Tri-S Bond Plus were used in conjunction with a universal composite (Estelite Sigma Quick) placed either incrementally (oblique) or in bulk with or without a flowable composite lining (Palfique Estelite LV). Ten serial B-scan images were obtained throughout each cavity by OCT (center wavelength: 1319nm). In order to evaluate adaptation defined as the cavity floor percentage showing no gap, a significant increase in the signal intensity was considered as gap at the bonded interface of the cavity floor. The same specimens were then cut into beams to measure MTBS at the cavity floor., Results: Two-way ANOVA demonstrated that the interaction of adhesive systems and filling techniques was significantly affecting both adaptation and MTBS (p<0.05). There was a significant correlation between MTBS and adaptation at cavity floor (p<0.05). Cavity floor adaptation and MTBS were improved when incremental filling technique was applied, while the outcome of lining technique was variable., Conclusions: Quantitative assessment by OCT can non-destructively provide information on the performance and effectiveness of dental composites and restoration techniques. There was a moderate correlation between floor adaptation and bond strength in class-I cavities. Incremental application of composite restoration showed the best performance in terms of bond strength and internal adaptation., Clinical Significance: Incremental application of composite restoration was the most advantageous placement technique in terms of bond strength and internal adaptation. The lack of placement pressure with flowable composites may affect their adaptation to all-in-one adhesives; therefore, the outcome of cavity lining by flowable composite was variable., (Copyright © 2012 Elsevier Ltd. All rights reserved.)