Vitamin D-conjugated gold nanoparticles as functional carriers to enhancing osteogenic differentiation.

In an aging society, bone disorders such as osteopenia, osteoporosis, and degenerative arthritis cause serious public health problems. In order to solve these problems, researchers continue to develop therapeutic agents, increase the efficacy of developed therapeutic agents, and reduce side effects. Gold nanoparticles (GNPs) are widely used in tissue engineering applications as biosensors, drug delivery carriers, and bioactive materials. Their special surface property enables easy conjugation with ligands including functional groups such as thiols, phosphines, and amines. This creates an attractive advantage to GNPs for use in the bone tissue engineering field. However, GNPs alone are limited in their biological effects. In this study, we used thiol-PEG-vitamin D (SPVD) to conjugate vitamin D, an essential nutrient critical for maintaining normal skeletal homeostasis, to GNPs. To characterize vitamin D-conjugated GNPs (VGNPs), field emission transmission electron microscopy, energy dispersive X-ray spectroscopy, dynamic light scattering, and ultraviolet/visible absorption analysis were carried out. The developed VGNPs were well bound through the thiol groups between GNPs and vitamin D, and were fabricated in size of 60 nm. Moreover, to demonstrate VGNPs osteogenic differentiation effect, various assays were carried out through cell viability test, alkaline phosphatase assay, calcium deposition assay, real-time polymerase chain reaction, and immunofluorescence staining. As a result, the fabricated VGNPs were found to effectively enhance osteogenic differentiation of human adipose-derived stem cells (hADSCs) in vitro. Based on these results, VGNPs can be utilized as functional nanomaterials for bone regeneration in the tissue engineering field.

Effects of aging procedures on the molecular, biochemical, morphological, and mechanical properties of vacuum-formed retainers.

The influence of intraoral exposure procedures on the physical characteristics of thermoplastic vacuum-formed retainers (VFRs) is still unclear. The effects of thermoforming and intraoral use on the molecular, chemical, morphological, and mechanical properties of thermoplastic VFRs were investigated. VFRs with a 0.8-mm-thick thermoplastic PETG sheet acquired from 48 patients were investigated with two aging procedures, including vacuum forming and intraoral exposure, for 2-week and 6-month. Eight evaluating sites for thermoplastic VFRs were assessed with seven analytical techniques. LM, SEM, and AFM microscopic findings showed that the surface characteristics increased with increasing in vivo exposure time (a four-fold increase) and varied depending on the sites evaluated (an occlusal surface). Raman and EDX spectroscopic findings showed that aging procedures led to a significant change in the molecular composition of VFRs, leading to a decrease in the composition rate of carbon (C) and the presence of silicon (Si), phosphorus (P), and calcium (Ca). Compressive strength and tensile tests showed that aging procedures led to a significant increase (P<0.01) in ultimate tensile strength, elastic modulus, the stored energy at a 6-mm deflection (u6 mm), and the compressed load at a 3-mm deflection (σ3 mm). Thermoforming led to a smoother surface and no crystallization of PETG sheets. Intraoral exposure accelerated changes in surface morphology, tensile strength, and elastic modulus of VFRs. This change was site-specific and enhanced with an increase in intraoral exposure time. Therefore, thermoforming and in vivo oral exposure procedures led to the molecular, morphological, and mechanical properties of thermoplastic VFRs.

Burn-wound healing effect of gelatin/polyurethane nanofiber scaffold containing silver-sulfadiazine.

Despite the fact that advances of burn treatment have led to reduction in the morbidity caused by burns, burn infection is still a serious problem. In this study, we designed blended synthetic and natural polymers nanofiber scaffolds using polyurethane (PU) and gelatin, which were prepared by an electrospinning method. Silver-sulfadiazine (SSD) was co-mixed to the blended polymer solution for being incorporated into the nanofibers after the electrospinning, followed by examination of burn-wound healing effect. The nanofiber scaffolds containing SSD should not only serve as a substrate for skin regeneration, but may also deliver suitable drugs, within a controlled manner during healing. The SSD release was able to prevent the growth of a wide array of bacteria and accelerate the wound healing by preventing infection. Therefore it could accelerate the burn-wound closure rate. We confirmed that PU/gelatin nanofiber scaffolds containing SSD lead to enhanced regeneration of burn-wounds.

Vitapan 3D-master shade guide showed no fluorescence emission.

OBJECTIVES: To determine the fluorescence property of Vitapan 3D-Master shade guide tabs with a spectrophotometer. MATERIALS AND METHODS: Fluorescence property of 29 shade tabs, in both of original and ground-to-flat forms, was determined by a reflection spectrophotometer. Color difference (ΔE*ab-FL) by the inclusion and exclusion of the UV component of a standard daylight simulator (CIE standard illuminant D65) was calculated to determine the fluorescence color change. Fluorescence peak was expressed as the difference in spectral reflectance values by the UV component. RESULTS AND CONCLUSION: ΔE*ab-FL values were in the range of 0.2 to 2.7 (mean: 1.2 ± 0.6) for the original and 0.5 to 1.6 (mean: 0.9 ± 0.1) for the ground-to-flat tabs, which was significantly different based on paired t-test (p<0.05); however, fluorescence peak was not detected in all the shade tabs. Therefore, fluorescence property of Vitapan 3D-Master shade guide should be modified to have similar fluorescence property of natural teeth and corresponding restorative materials.

Difference in the color stability of direct and indirect resin composites.

UNLABELLED: Indirect resin composites are generally regarded to have better color stability than direct resin composites since they possess higher conversion degree. OBJECTIVE: The present study aimed at comparing the changes in color (ΔE) and color coordinates (ΔL, Δa and Δb) of one direct (Estelite Sigma: 16 shades) and 2 indirect resin composites (BelleGlass NG: 16 shades; Sinfony: 26 shades) after thermocycling. MATERIAL AND METHODS: Resins were packed into a mold and light cured; post-curing was performed on indirect resins. Changes in color and color coordinates of 1-mm-thick specimens were determined after 5,000 cycles of thermocycling on a spectrophotometer. RESULTS: ΔE values were in the range of 0.3 to 1.2 units for direct resins, and 0.3 to 1.5 units for indirect resins, which were clinically acceptable (ΔE<3.3). Based on t-test, ΔE values were not significantly different by the type of resins (p>0.05), while ΔL, Δa and Δb values were significantly different by the type of resins (p<0.05). For indirect resins, ΔE values were influenced by the brand, shade group and shade designation based on three-way ANOVA (p<0.05). CONCLUSION: Direct and indirect resin composites showed similar color stability after 5,000 cycles of thermocycling; however, their changes in the color coordinates were different.

Difference in the color stability of direct and indirect resin composites

Indirect resin composites are generally regarded to have better color stability than direct resin composites since they possess higher conversion degree. OBJECTIVE: The present study aimed at comparing the changes in color (ΔE) and color coordinates (ΔL, Δa and Δb) of one direct (Estelite Sigma: 16 shades) and 2 indirect resin composites (BelleGlass NG: 16 shades; Sinfony: 26 shades) after thermocycling. MATERIAL AND METHODS: Resins were packed into a mold and light cured; post-curing was performed on indirect resins. Changes in color and color coordinates of 1-mm-thick specimens were determined after 5,000 cycles of thermocycling on a spectrophotometer. RESULTS: ΔE values were in the range of 0.3 to 1.2 units for direct resins, and 0.3 to 1.5 units for indirect resins, which were clinically acceptable (ΔE<3.3). Based on t-test, ΔE values were not signifcantly different by the type of resins (p>0.05), while ΔL, Δa and Δb values were signifcantly different by the type of resins (p<0.05). For indirect resins, ΔE values were infuenced by the brand, shade group and shade designation based on three-way ANOVA (p<0.05). CONCLUSION: Direct and indirect resin composites showed similar color stability after 5,000 cycles of thermocycling; however, their changes in the color coordinates were different.

Perceived color shift of a shade guide according to the change of illuminant.

STATEMENT OF PROBLEM: The perceived color of shade guide tabs is influenced by different spectral compositions of different light sources, and this can influence color matching. PURPOSE: The purpose of this study was to determine the amount of perceived shift in color and color coordinates of a shade guide using 3 different light sources: CIE standard illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp). MATERIAL AND METHODS: CIE color coordinates L*, a*, b*, chroma, and the spectral reflectance of shade tabs in a shade guide (Vitapan 3D-Master) were measured by a spectroradiometer under D65, A, and F9 simulators. Perceived color and color coordinate shifts due to the change of illuminant were determined. The influence of the type of light and shade designation of the 26 tabs on the color coordinates was analyzed by a 2-way ANOVA; correlations in the color coordinates between each corresponding pair under the 3 illuminants were determined (α=.05). RESULTS: All of the color coordinates were influenced by the type of illuminant and shade designation of the shade tabs (P<.001); however, each corresponding coordinate pair showed significant correlations under different illuminants (r=0.930 to 0.997, P<.01). Color differences under different illuminants were in the range of 3.1 to 9.1 ΔE units; all of these differences were perceptible (ΔE>2.6). Lightness decreased and chroma increased when the illuminant was changed from the D65 simulator to the A or F9 simulators. CONCLUSIONS: Perceptible shifts in the color of shade guide tabs under different ambient lighting conditions were confirmed by a spectroradiometer; these color shifts were influenced by the type of illuminant used.

Shade compatibility of esthetic restorative materials--A review.

OBJECTIVES: The objectives of this study were to review the shade compatibility of esthetic restorative materials and to provide a visual method to harmonize the color of them. METHODS: Published reports on the color ranges and distributions of shade guides, color differences between restorative materials and the referenced shade guides, and those between the identical shade designated restorative materials were reviewed. RESULTS: Several limitations in shade guides should be considered in color matching such as (1) color ranges and distributions of shade guides are different from those of human teeth, (2) arrangements of shade tabs in shade guides are not ideally logical, and (3) color of marketed esthetic restorative materials and the referenced shade tabs is significantly different. Color coordinates of restorative materials of the identical shade designations vary by the kind and brand of the restorative materials. Color differences between restorative materials and the referenced shade guides and those between the identical shade designated restorative materials are generally higher than perceptible limits. A visual color harmonization method was suggested, and the considerations for the instrumental color harmonization were provided. SIGNIFICANCE: Visual color matching would result in color mismatching by the kind and brand of the restorative materials. The first step to improve the color matching performance would be the harmonization of the color of restorative materials with those of the corresponding shade tabs.

Spectroradiometric and spectrophotometric translucency of ceramic materials.

STATEMENT OF PROBLEM: The spectroradiometer (SR) was introduced as an alternative instrument to the spectrophotometer (SP) for measuring color in dentistry. No published studies were identified on the SR-based translucency of clinically simulated dental ceramics that closely reflect clinical conditions. Furthermore, it is unclear whether there is a correlation between SR- and SP-based translucency values. PURPOSE: The purpose of this study was to compare the translucency parameter (TP) of core, veneer, and layered ceramics determined by an SR, and to determine the correlations in TPs measured by an SR and a reflection SP. MATERIAL AND METHODS: Seven A2 shade core ceramics and corresponding A2 and A3 shade veneer ceramics were fabricated with a layered thickness of 1.5 mm. The color of core, veneer, and A2- and A3-layered ceramics was measured over white and black backgrounds by an SR with 2 measuring apertures of 2.63 and 5.25 mm in diameter, and also by an SP (n=7). TP values were calculated and the differences in SR (5.25)-based TP values of the layered ceramics were analyzed with 2-way ANOVA with the fixed factors of shade designation and type of ceramic core (α=.05). The influence of the brand on the TP values of core, veneer, and A2- and A3-layered ceramics was also analyzed with 1-way ANOVA. Correlation analysis and paired t test were performed for the SR- and SP-based TP values (α=.05). RESULTS: SR (5.25)-based TP values of layered ceramics ranged from 4.4 to 12.5, and were influenced by the type but not by the shade designation. SR-based TP values of core, veneer, and A2- and A3-layered ceramics were influenced by the brand. SR- and SP-based TP values were highly correlated (r=0.982 to 0.987, P<.01), although TP values based on SR measurement were significantly higher (P<.05). CONCLUSIONS: SR measurements showed significantly different translucency for different types of clinically simulated ceramic specimens. TP values measured by the SR and the SP were significantly different but highly correlated.

Lightness, chroma, and hue distributions of a shade guide as measured by a spectroradiometer.

STATEMENT OF PROBLEM: The color attributes of commercially available shade guides have been measured by spectrophotometers (SP), which are designed to measure flat surfaces. However, there is limited information on the color distribution of shade guides as measured by spectroradiometers (SR), which are capable of measuring the color of curved surfaces. PURPOSE: The purpose of this study was to determine the distributions of lightness (CIE L*) and chroma (C*(ab)) step intervals between adjacent shade tabs of a shade guide based on the lightness, chroma, and hue attributes measured by an SR. MATERIAL AND METHODS: Lightness, chroma, hue angle, and CIE a* and b* values of the shade tabs (n=26) from a shade guide (Vitapan 3D-Master) were measured by an SR under daylight conditions. The distributions of the ratios in lightness and chroma of each tab compared with the lowest lightness tab or the lowest chroma tab were determined. The values for each color parameter were analyzed by a 3-way ANOVA with the factors of lightness, chroma, and hue designations of the shade tabs (alpha=.05). RESULTS: The chroma and CIE a* and b* values were influenced by the lightness, chroma, and hue designations of the shade tabs (P<.001); however, the lightness and hue angle were influenced by the lightness and hue designations, but not by the chroma designation. Distributions for the CIE a* and b* values, in each lightness group, corresponded with the chroma designation. However, the intervals in the lightness and chroma scales between adjacent tabs were not uniform. CONCLUSIONS: The intervals in the color parameters between adjacent shade tabs were not uniform based on SR measurements. Therefore, a shade guide in which shade tabs are more equally spaced by the color attributes, based on the values as measured by an SR along with observers' responses with respect to the equality of the intervals, should be devised.

Variation in instrument-based color coordinates of esthetic restorative materials by measurement method-A review.

OBJECTIVES: Optical properties of an object are determined visually or instrumentally. Although instrumental measurement provides objective and quantitative color coordinates, these values vary by the measurement method such as specimen and background conditions, instrument settings and illuminant. The objective of this study was to review the influence of the measurement method on the instrumental color coordinates of esthetic dental restorative materials. METHODS: Published reports on the measurement method dependent color variations of esthetic restorative materials were reviewed. RESULTS: Surface roughness influences the color coordinates differently by the surface roughness range and the measurement geometry. Specimen thickness and the kind of illuminant influence the color coordinates, and the influence of background varied by specimen thickness. Therefore, the specular component excluded (SCE) geometry that reflects the surface condition of specimens is suggested as the correct measurement geometry. Surface roughness, thickness and layering of specimens, and the kind of illuminant should be stipulated in each measurement. There should be a standard for the color and gloss of the background. SIGNIFICANCE: Variables in instrumental color measurements should be stipulated to obtain consistent and comparable color coordinates, and a general guideline for instrumental color measurement of dental materials should be established.

Correlations between spectroradiometric and spectrophotometric colors of all-ceramic materials.

OBJECTIVES: Color coordinates of translucent esthetic materials measured by traditional spectrophotometers (SP) would deviate from those measured by newly introduced spectroradiometers (SR), which might simulate the clinical viewing condition better. This study aimed to determine the correlations in the SP- and SR-based color coordinates and color differences of all-ceramic materials. METHODS: Specimens for seven A2 shade core ceramics (n=7) and corresponding A2 and A3 shades veneer ceramics (n=7) were fabricated in clinically relevant thicknesses (1.5mm after layering). Color of layered specimens was measured according to the CIELAB color scale by a SP and a SR. Color differences (ΔE(ab)(*)) between the reference ceramics and the corresponding layered ceramics were calculated. Correlations between SP- and SR-based color coordinates and color difference values were determined (α=0.05). RESULTS: SR-based color coordinates were significantly different from the SP-based values; however, general shifting trends by the instrument were observed. SP- and SR-based CIE a*, b* and chroma values showed significant correlations (p<0.05); however, the CIE L* values and the color differences with the reference showed no significant correlations (p>0.05). SIGNIFICANCE: The color coordinates representing the hue attribute (CIE a*, b* and chroma) measured by a spectrophotometer and a spectroradiometer showed significant correlations; however, the color coordinates and the color difference values were significantly different by the instrument. Therefore, color coordinates and the color difference values based on different instruments should not be compared directly.

Influence of HEMA content on the mechanical and bonding properties of experimental HEMA-added glass ionomer cements.

The purpose of this study was to determine the influence of incrementally added uncured HEMA in experimental HEMA-added glass ionomer cement (HAGICs) on the mechanical and shear bond strength (SBS) of these materials. Increasing contents of uncured HEMA (10-50 wt.%) were added to a commercial glass ionomer cement liquid (Fuji II, GC, Japan), and the compressive and diametral tensile strengths of the resulting HAGICs were measured. The SBS to non-precious alloy, precious alloy, enamel and dentin was also determined after these surfaces were subjected to either airborne-particle abrasion (Aa) or SiC abrasive paper grinding (Sp). Both strength properties of the HAGICs first increased and then decreased as the HEMA content increased, with a maximum value obtained when the HEMA content was 20% for the compressive strength and 40% for the tensile strength. The SBS was influenced by the HEMA content, the surface treatment, and the type of bonding surface (p<0.05). These results suggest that addition of an appropriate amount of HEMA to glass ionomer cement would increase diametral tensile strength as well as bond strength to alloys and teeth. These results also confirm that the optimal HEMA content ranged from 20 to 40% within the limitations of this experimental condition.

Influence of HEMA content on the mechanical and bonding properties of experimental HEMA-added glass ionomer cements

The purpose of this study was to determine the influence of incrementally added uncured HEMA in experimental HEMA-added glass ionomer cement (HAGICs) on the mechanical and shear bond strength (SBS) of these materials. Increasing contents of uncured HEMA (10-50 wt. percent) were added to a commercial glass ionomer cement liquid (Fuji II, GC, Japan), and the compressive and diametral tensile strengths of the resulting HAGICs were measured. The SBS to non-precious alloy, precious alloy, enamel and dentin was also determined after these surfaces were subjected to either airborne-particle abrasion (Aa) or SiC abrasive paper grinding (Sp). Both strength properties of the HAGICs first increased and then decreased as the HEMA content increased, with a maximum value obtained when the HEMA content was 20 percent for the compressive strength and 40 percent for the tensile strength. The SBS was influenced by the HEMA content, the surface treatment, and the type of bonding surface (p<0.05). These results suggest that addition of an appropriate amount of HEMA to glass ionomer cement would increase diametral tensile strength as well as bond strength to alloys and teeth. These results also confirm that the optimal HEMA content ranged from 20 to 40 percent within the limitations of this experimental condition.