Influence of in-office whitening on the color matching and surface characteristics of single-shade resin composites.

OBJECTIVE: The color matching of single-shade resin composites after in-office whitening was investigated. MATERIALS AND METHODS: Four single-shade resin composites were used. A total of 35% hydrogen peroxide was used as the whitening agent. The resin composite was placed in a cavity of an artificially discolored bovine tooth. The color differences between the restoration and surrounding enamel before and after whitening were determined based on ΔE*ab, ΔE00, and ΔWID. The color stability, surface roughness (Sa), and surface gloss (GU) of the resin composite alone were also evaluated. Statistical analyses were performed using repeated-measures analysis of variance with the Tukey-Kramer test. RESULTS: Based on the 50:50% of perceptibility and acceptability thresholds of ΔE*ab and ΔE00, none of the resin composite restorations were clinically acceptable before or after whitening. Regarding ΔWID, although all resin composites showed "acceptable match" in the baseline, they showed "mismatch" after the third session of whitening. Most of the resin composites alone were stable in color against whitening. CONCLUSIONS: Although the single-shade resin composites failed to achieve the expected color matching on discolored teeth either before or after the whitening, the impact of the whitening on the color of the resin composite alone may be negligible.

Effect of ion-releasing filler-containing gel application on dentin remineralization using optical coherent tomography.

PURPOSE: To examine the effects of an ion-releasing filler-containing gel on the remineralization of dentin using optical coherence tomography (OCT). METHODS: Dentin slabs of bovine teeth were sliced and shaped into a rectangular form. Specimens were treated with undersaturated 0.1 M lactic acid buffer solution (pH 4.75) for 10 minutes and then placed in artificial saliva (pH 7.0). This procedure was repeated three times a day for 28 days. The dentin remineralization effects of a fluoride/S-PRG filler-containing gel (PRG) and a 38% SDF solution (SDF) on dentin slabs of bovine teeth were compared. After treatment, the dentin slabs were immersed in a 0.1 M lactic acid buffer solution and then placed in artificial saliva. This procedure was repeated three times a day for 28 days. OCT imaging was conducted on the selected location of the dentin surface. The peak intensity and width at 1/e² were recorded in each of the six areas on the sample and averaged. Each group had a sample size of 10. Knoop hardness number (KHN) measurements and scanning electron microscopy (SEM) observations were also conducted. The data for each group were subjected to a one-way repeated-measures ANOVA and Tukey tests (α= 0.05). The samples were also observed using SEM. RESULTS: The peak signal intensities of SDF and PRG decreased on day 7 and then slightly increased during the experimental period for the one-off application groups and then decreased for frequent-time application groups. Although the width at 1/e² in the untreated specimens decreased over the test period, SDF and PRG for the one-off application groups exhibited an increase in widths on day 7 followed by a slight decrease, whereas it increased for the frequent-time application groups. The average KHN of the dentin samples exhibited the same tendency as the width at 1/e². Closure of the dentin tubules and crystal precipitation were detected on the surface of both SDF and PRG groups. CLINICAL SIGNIFICANCE: S-PRG filler-containing gel might have the ability to prevent dentin demineralization and could be useful for the prevention of hard-to-access lesions. This material achieved remineralization of the demineralized root dentin and had the same remineralization ability as SDF in vitro.

Surface moisture influence on etch-and-rinse universal adhesive bonding.

PURPOSE: To evaluate whether surface moisture would influence the bonding effectiveness of universal adhesives in etch-and-rinse mode. METHODS: All-Bond Universal (AB), G-Premio Bond (GP) Prime&Bond Active (PB) and Scotchbond Universal Adhesive (SU) were evaluated. Shear bond strengths after 24 hours and 10,000 thermal cycles of universal adhesives to moist and dry enamel and dentin in etch-and-rinse mode were determined. Scanning electron microscopy observations of the adhesive interfaces were conducted. RESULTS: The bond durability of universal adhesive to dentin in etch-and-rinse mode was influenced by the surface moisture, unlike bond durability to enamel. The bond durability of AB and GP, but not PB and SU, to dentin in etch-and-rinse mode was different depending on the surface moisture. Surface moisture did not influence the thicknesses of the adhesive or hybrid layer of resin-dentin interfaces, but the length of resin tags in the moist group was longer than in the dry group. CLINICAL SIGNIFICANCE: Some universal adhesives, with the addition of specific components and optimization of water content, can achieve stable bonds regardless of surface moisture, but the surface moisture of dentin, although not enamel, is still a significant factor for universal adhesive bonding in etch-and rinse mode.

Evaluation of the effect of a glass ionomer cement containing fluoro-zinc-silicate glass on dentin remineralization using the ultrasonic pulse-echo method.

The purpose of this study was to investigate the protective effect of a glass ionomer cement (GIC) consisting of fluoro-zinc-silicate glass on the demineralization of bovine dentin using the ultrasonic pulse-echo method. The findings were compared with those obtained using a conventional GIC. Slabs of dentin from bovine teeth were sliced, shaped into a rectangular form, and immersed in 0.5 M ethylenediaminetetraacetic acid solution at 25ºC for 6 days, followed by storage in distilled water for 3 days. After demineralization, they were immersed in artificial saliva with and without the GIC specimens. The propagation times of the longitudinal ultrasonic waves in the samples were measured. The ultrasonic velocities of the fluoro-zinc-silicate glass-containing GICs were significantly increased 2-3 days after the start of the experiment and showed an upward trend thereafter. These findings indicate that the GICs containing fluoro-zinc-silicate glass might exhibit the potential to promote remineralization in the dentin.

Interrelation among the handling, mechanical, and wear properties of the newly developed flowable resin composites.

OBJECTIVES: This study investigates the handling, mechanical, and wear properties of the newly developed flowable resin composites and elucidate the interrelations among the tested parameters. METHODS: Six flowable and two conventional resin composites are used. Five measurements are performed per resin composite to obtain the average inorganic filler content. Ten specimens per material are used to obtain the flexural strength, flexural modulus, and resilience. For sliding impact wear testing, twelve specimens are prepared. Noncontact profilometer and confocal laser scanning microscopy are used to determine the maximum facet depth and volume loss. Extrusion force and thread formation are used to measure the handling properties of the flowable resin composites. Six measurements are performed per flowable resin composite. Data evaluation is performed using analysis of variance and Tukey's honestly significant difference test at an α-level of 0.05. The correlation between the tested parameters is verified using the Pearson product-moment correlation coefficient. RESULTS: A subset of flowable resin composites exhibits higher flexural properties and wear resistance as compared to the conventional resin composites. The handling properties of the flowable resin composites are material dependent. CONCLUSION: While the resilience parameters exhibit an extremely strong and statistically significant correlation with the wear parameters, the handling properties exhibit no interrelation with the remaining parameters. SIGNIFICANCE: While the handling properties of the newly developed flowable resin composites did not correlate with the mechanical and wear properties, some new flowable resin composites have the potential for use in high-stress bearing areas, such as posterior lesions, because of the enhanced mechanical properties and wear resistance.