There appears to be a need for a reliable method for quantification of tooth colour and analysis of shade. Therefore, the primary objective of this study was to show the applicability of graphic software in colour analysis and secondly to investigate the reliability of commercial shade guides produced by the same manufacturer, using this digital technique. After confirming the reliability and reproducibility of the digital method by using self-assessed coloured images, three shade guides of the same manufacturer were photographed in daylight and in studio environments with a digital camera and saved in tagged image file format (TIFF) format. Colour analysis of each photograph was performed using the Adobe Photoshop 4.0 graphic program. Luminosity, and red, green, blue (L and RGB) values of each shade tab of each shade guide were measured and the data were subjected to statistical analysis using the repeated measure Anova test. The L and RGB values of the images taken in daylight differed significantly from those of the images taken in studio environment (P < 0.05). In both environments, the luminosity and red values of the shade tabs were significantly different from each other (P < 0.05). It was concluded that, when the environmental conditions were kept constant, the Adobe Photoshop 4.0 colour analysis program could be used to analyse the colour of images. On the other hand, the results revealed that the accuracy of shade tabs widely being used in colour matching should be readdressed.
Colour determination may be precisely performed with spectrophotometers, however this technique is time consuming and requires special devices. The aim of this study was to determine the correlation between the colour measurements performed on three shade guides of the same manufacturer, obtained with digital and spectrophotometric analyses. Sixty shade tabs of three shade guides were analysed to determine the L*, a*, b* values with a spectrophotometer. The same shade tabs were also imaged with a digital camera, and same colour parameters were determined on the digital images with the software. Three measurements for each shade tab were made with both methods. Statistical differences between the results of two methods were determined using anova (alpha = 0.05). Additionally, presence of any correlation between two methods within each guide was investigated by using correlation analysis. It was observed that the a* and b* values obtained by digital method were correlated with those of the spectrophotometer. Spectrophotometric analysis revealed no disparities among the L* measurements of the shade tabs of three shade guides (P > 0.05), but significant differences were observed between the L* values of the shade tabs with digital analysis method (P = 0.000). The digital method formed more subgroups than the spectrophotometer. For a* and b* values, both methods revealed significant differences among the shade tabs (P < 0.05). Additionally, both analyses revealed that colour characteristics of the first shade guide was different than the other two. The results obtained by digital method were correlated with those of the spectrophotometer, especially for a* and b* values.
Although some new-generation CAD/CAM and provisional restoration materials display slight cytotoxicity values, the results are still within the reliable range, and they can safely be used in clinical conditions.
STATEMENT OF PROBLEM Surface-finishing protocols have a mechanical impact on ceramic surfaces that could eventually affect surface topography and light scattering. An optimum protocol is needed to avoid damaging the optical properties of ceramics. PURPOSE The purpose of this study was to determine the effects of different surface-finishing protocols on the surface roughness, color change, and translucency of ceramic and metal ceramic restorations. MATERIAL AND METHODS Standardized disk-shaped specimens (1.5 × 10 mm, n=128) were fabricated from 3 different ceramic core materials (aluminum oxide [Al2O3]-AL, zirconium oxide [ZrO2]-ZR, lithium disilicate [Li2Si2O5]-LIT), veneered (V) with dentin ceramics (n=32 per group), and placed in the following groups: ALV, ZRV, and LITV. The metal ceramic group acted as the control (n=32). Four different surface-finishing methods were tested. Airborne-particle abrasion with 50 m Al2O3, polishing with adjustment kit, polishing with adjustment kit plus diamond polishing paste, and autoglazing (n=8 subgroup) were applied on the veneering ceramics. The specimens were analyzed with a profilometer for surface roughness, and color change and translucency were measured with a clinical spectrophotometer. Statistical analyses were performed with 1-way ANOVA and the Tukey honest significant difference tests (=.05). RESULTS Specimens treated with the airborne particle abrasion method showed significantly higher mean profilometer for surface roughness values in all groups (P<.05). The polishing with adjustment kit and autoglazing methods revealed statistically similar surface roughness values in all groups (P>.05). With the diamond polishing paste method, lower surface roughness values were achieved in the ZRV and metal ceramic groups acted as the control groups. Different surface-finishing methods affected the color change of the ceramic systems, except for ZRV. Surface-finishing protocols significantly affected the translucency values of the ALV, LITV, and metal ceramic groups (P<.05). CONCLUSIONS No single surface-finishing protocol can be recommended to obtain the smoothest surface and the least color change without affecting translucency for the ceramics tested. The airborne-particle abrasion protocol created rougher surfaces and decreased translucency, and color change in zirconia was not affected by the finishing protocols. Purpose. The purpose of this study was to determine the effects of different surface finishing protocols on the surface roughness, color change and translucency of all-ceramic and metalceramic restorations. Materials and methods.Standardized disc-shaped specimens (1.5 mm x 10 mm, N=128)were fabricated using three different all-ceramic core materials (Al 2 O 3 -AL, ZrO 2 -ZR, Li 2 Si 2 O 5 -LIT) materials and veneered (V) with dentin ceramics (n=32 per group) constituting the following groups: ALV, ZRV, LITV. Metal-ceramic group acted as the control (MC) (n=32). Four different surface finishing methods were tested: Air-borne particle abrasion (AB) with 5...
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