Effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network material.

OBJECTIVES: To evaluate the effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network (PICN) material. METHODS: Specimens of 0.5, 1.0, 1.5 mm thicknesses were obtained by sectioning VITA ENAMIC® multiColor (E-MC) High Translucent CAD-CAM blocks (1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT). Spectral reflectance and color coordinates were measured on white and black backgrounds using a spectroradiometer, CIE D65 illuminant and CIE 45°/0° geometry. CIEDE2000 color and translucency differences (ΔE00 and ΔTP00 ) between thicknesses and adjacent layers were evaluated using their respective 50:50% perceptibility and acceptability thresholds (PT00 and AT00 ). RESULTS: In general, ΔE00 between thicknesses for all shades and layers were above AT00 in general. Chroma decreased from cervical to incisal layers with statistically significant differences (p < 0.05), and ΔE00 between sequential layers were above PT00 , for all shades and thicknesses. TP00 decreased from 0.5 to 1.5 mm and increased from cervical to incisal layers for all shades with statically significant translucency differences (p < 0.05). In general, for all thicknesses, TPT00 < ΔTP00 < TAT00 for sequential layers. CONCLUSIONS: The gradient in color and translucency of E-MC PICN material was influenced by the thickness of the CAD-CAM block. In addition, color and TP transition values between the layers depends on the thickness and shade. CLINICAL SIGNIFICANCE: The effect of thickness must be taken into account by dental technicians and dentists when CAD-CAM multicolor PICN materials are used.

Correction: Photographic-Based Optical Evaluation of Tissues and Biomaterials Used for Corneal Surface Repair: A New Easy-Applied Method.

[This corrects the article DOI: 10.1371/journal.pone.0142099.].

Investigating a novel nanostructured fibrin-agarose biomaterial for human cornea tissue engineering: rheological properties.

In this work, the rheological properties of the biomaterial fibrin with different agarose concentrations, used for the generation of a bioengineered human corneal stroma by tissue engineering, before and after using a nanostructuring technique, were analyzed. The transparency of these artificial human stromas was also investigated. The temporal evaluation of the properties of these biomaterials is essential for the design of functional biological human corneal replacements. The nanostructuring technique used for the generation of nanostructured corneal constructs (NCCs) had a major influence on the rheological properties of the fibrin-agarose corneal equivalents. For an oscillatory shear stress of 1 Hz, well in the order of the natural oscillations of the human cornea, the NCCs had viscoelasticity values higher than those of non-nanostructured corneal constructs (N-NCCs), but similar to those of an ex vivo native cornea. The model that most resembled the rheological behavior of the native cornea was a fibrin-0.1% agarose concentration nanostructured construct. In addition, this artificial cornea model displayed optimal levels of transparency, similar to the native tissue. All these properties indicate that the fibrin-0.1% agarose concentration nanostructured construct might serve as an adequate candidate for the generation of an artificial complete cornea, not only for transplanting use but also for conducting pharmaceutical testing and biomedical research.

Generation of bioengineered corneas with decellularized xenografts and human keratocytes.

PURPOSE: Decellularization of animal corneas is a promising method for the development of artificial human corneas by tissue engineering. In this study, two different decellularization protocols were evaluated to determine which one is able to best preserve the histologic structure, composition, and optical behavior of decellularized porcine corneas. Then, these corneas were recellularized with human keratocytes to obtain a partial human corneal substitute. METHODS: Two different decellularization protocols were applied, using NaCl and SDS, to determine which one is able to best preserve the histologic structure, composition, and optical behavior of the decellularized corneas. Then, those decellularized corneas that showed the most appropriate results were recellularized with human keratocytes and evaluated at the histologic, biochemical, and optical levels for use in regenerative medicine. RESULTS: The results showed that 1.5 M NaCl treatment of porcine corneas is able to generate an acellular corneal stroma with adequate histologic and optical properties and that human keratocytes are able to penetrate and spread within this scaffold with proper levels of cell differentiation. In contrast, 0.1% SDS treatment of porcine corneas resulted in high levels of fibril disorganization and poor optical behavior of these corneas. CONCLUSIONS: In conclusion, the authors suggest that the decellularization of animal corneas with 1.5 M NaCl represents a useful method for the development of human bioengineered corneas with therapeutic potential.

UV absorbance of a bioengineered corneal stroma substitute in the 240-400 nm range.

PURPOSE: To determine the UV absorbance of a bioengineered human corneal stroma construct based on fibrin and fibrin-agarose scaffolds in the 240-400 nm range. METHODS: Three types of artificial substitutes of the human corneal stroma were developed by tissue engineering using fibrin and fibrin with 0.1% and 0.2% agarose scaffolds with human keratocytes immersed within. After 28 days of culture, the UV absorbance of each sample was determined using a spectrophotometer. The thickness of corneal stroma samples was determined by light microscope. RESULTS: For all the 3 types of corneal stroma substitutes studied, the range of the UV absorbance values was similar to that of the native human corneal stroma, although the fibrin with 0.1% agarose stroma substitute had the best UV filtering properties. The higher UV absorbance of the artificial substitute of the human corneal stroma was in the UV-B and -A ranges, suggesting that these artificial tissues could have potential clinical usefulness and proper UV light-absorption capabilities. CONCLUSION: Our data suggest that the bioengineered human corneal substitute of fibrin with 0.1% agarose is an effective absorber of harmful UV radiation and could therefore be potentially useful.

Prevalence of refractive errors in school-age children in Morocco.

BACKGROUND: The prevalence of refractive errors in school-age children in Morocco was assessed. METHODS: A total of 545 children (300 boys and 245 girls, between 6 and 16 years of age) attending school were examined to assess their refractive errors in a field study in Morocco (North Africa). The examination included autorefraction under cycloplegia and visual acuity, stereopsis and anterior corneal-radius measurements . RESULTS: We found a low prevalence of myopia (< or =-0.5 D SE [spherical equivalent] in at least one eye), i.e. only 6.1%. The prevalence of hyperopia (> or =2.0 D SE in at least one eye) was 18.3%. Astigmatism (< or =-0.75 D of cylinder in at least one eye) was found in 23.5% of these children. The low prevalence of large refractive errors makes visual acuity in these children very good. In general, the corneal radii did not significantly vary with age. There were no significant differences between the distribution of refractive errors in these children according to gender but there were with respect to age. CONCLUSIONS: There was a low prevalence of myopia in these African children, astigmatism being the most frequent refractive error. The mean refractive errors found were low, and therefore visual acuity was high in these children.