1,721,039 research outputs found
Color match of two different ceramic systems to selected shades of one shade guide
No full textSTATEMENT OF PROBLEM:
There are no consistent indications given by dental manufacturers on how to layer ceramics to achieve a color match to a shade selected from a dental shade guide. The technique for ceramic layering relies primarily on the skill and experience of ceramists and is not easily predictable.
PURPOSE:
The purpose of this study was to evaluate, using a clinical spectrophotometer, the ability to color match shades selected with the 3D-Master shade guide using 2 different ceramic systems.
MATERIAL AND METHODS:
Two ceramic systems were selected for this study, the VITA Omega 900 and VITA VM 13. For both systems, shades 2M3, 3M2, 4M2 of the VITA 3D-Master shade guide were selected. Thirty ceramic discs, 15 mm in diameter, were fabricated with different layer thickness ratios of opaque dentin, dentin, and enamel, maintaining a constant overall thickness. A clinical spectrophotometer (VITA Easyshade) was used for color comparison. The measured ΔE values were statistically analyzed with a 3-way ANOVA and the Tukey HSD test (α=.05).
RESULTS:
The 3-way ANOVA showed that the ceramic system (P<.001), the selected shade (P<.001), and the layering scheme all significantly influenced the ΔE values (P<.001).
CONCLUSIONS:
Both VITA VM 13 and VITA Omega 900 ceramic systems showed a color match with the shades 2M3, 3M2, and 4M2 of the VITA 3D-Master shade guide to be within the limits for clinical acceptability (ΔE≤ 3.3). VM 13 showed a statistically better color match. The layering scheme influenced the definitive color of the restoration.
Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved
Color correspondence of different batches of TriLuxe CAD/CAM ceramic blocks
No full textTriLuxe ceramic blocks for chairside CAD/CAM procedures are color layered to allow natural esthetics, and only require subsequent glazing. The purpose of this study was to compare color repeatability of different batches of TriLuxe blocks. The three commercially available shades (1M2C, 2M2C, 3M2C) of TriLuxe blocks for the Cerec CAD/CAM system were examined. For each of the three colors, three different batches were tested, 5 blocks each. The measurements were made using a spectrophotometer equipped with an integrating sphere using the CIELab* colorimetric system. One-way ANOVA showed that the factor "Production Batch" was not statistically significant. Regarding deltaE, none of the 315 color comparisons (neither within the same shade, nor between specimens of the same batch, nor between specimens from different batches) exceeded the proposed deltaE = 3.3 threshold for clinical acceptability. All the different batches of the different shades of VITA TriLuxe blocks for the Cerec system showed the high degree of color correspondence necessary in industrially prefabricated CAD/CAM blocks
Influence of layering thickness on the color parameters of a ceramic system
No full textOBJECTIVES:
The aim of this study was to establish by means of a spectrophotometer the influence of each layer of a porcelain fused to metal (PFM) ceramic system on the color parameters (Lightness, Chroma and Hue) of the final restoration.
METHODS:
One ceramic system (Vita VM13, Vita Zahnfabrik, Bad Säckingen, Germany) was evaluated. 40 ceramic discs were fabricated with a proprietary steel mold and individually checked after firing with a digital calliper to control the thickness of each layer. 4 different total ceramic thicknesses in 2M3 shade were evaluated. For each thickness 2 different layering patterns were analyzed. The layering thickness range for Base Dentin was 0.25-0.90 mm, for Transpa Dentin 0.35-0.75 mm, for Enamel 0.15-0.50 mm. Easyshade (Vita Zahnfabrik) clinical spectrophotometer was used for color comparison with the reference color data of the selected shade stored into the device.
RESULTS:
One-way ANOVAs showed that the factor 'layering pattern' significantly influenced the DeltaE, DeltaC, DeltaH and DeltaL (p<0.001). Greater thicknesses of Base Dentin resulted in a more Chromatic shade. Conversely, greater thicknesses of Transpa Dentin and Enamel reduced the Chroma of the color. An increase in the Enamel layer thickness resulted in a reduction of the Lightness (Value) and vice-versa.
SIGNIFICANCE:
The variation in thickness of the various layers significantly influenced the final color of the artifact. The variation found should be taken into account in order to obtain the aimed shade, in relationship with the total thickness of the ceramic veneer
Cement opacity and color as influencing factors on the final shade of metal-free ceramic restorations
No full textObjective: To investigate the influence of opacity and color of luting cements on the final shade of metal-free restorations. Materials and Methods: Five resin cement colors in combination with four different thicknesses of CAD/CAM ceramic materials were tested, and a composite substrate was used as dentin color reference (n = 3). Specimen color was measured with a spectrophotometer equipped with an integrating sphere before and after cementation (CIELAB). Cement and ceramic color and opacity (TP) were assessed by measuring the tested ceramic thickness as a 1-mm thick disk for each of the cement shades. The differences in color were evaluated (ΔE00). Data were statistically analyzed by a Two-Way ANOVA followed by the Tukey Test for post-hoc comparison (P <.05) and multiple comparison Pearson's test (P <.05); the acceptability and perceptibility threshold were evaluated. Results: Statistically significant influence was found for factors ceramic thickness and cement shade (P <.001). Perceptible and unacceptable color changes were induced on the final restoration by resin cements (ranging from ΔE00 = 0.69 ± 0.54 to ΔE00 = 5.53 ± 0.46), the correlation between factors became strong (r2 > 0.6) in case of mismatch between color and translucency of cement and ceramic. Only the clear shade in combination with the thickest ceramic, resulted in an imperceptible color change (ΔE00 = 0.69 ± 0.54). Conclusions: The final shade of ceramic restorations can be influenced by resin cements; the magnitude of influence is related to the cement optical properties. Clinical Significance: In order to influence the final shade of a ceramic restoration, a cement more opaque than the restorative material should be used. Conversely, in the case of a fitting shade of the restoration, a cement more translucent than the restoration should be used to avoid undesired changes
Reviewing assessment strategies in European dental schools
Full text linkObjectives: Effectively assessing dental students' knowledge and skills is an important part of their education. Assessment techniques available to teachers, have become more diverse as new technologies are introduced. This study aimed to investigate what dental educators thought about current and future assessment techniques. Methods: This was a mixed method study; quantitative data being collected at an annual dental educators' conference, via on-screen questions requesting: i) demographic information; ii) type of student assessment currently used; iii) impact of Covid-19 on student assessment, and iv) future perceptions of assessment. Questions were posed in real time using the 'Vevox' platform. Descriptive statistical analysis was employed. Qualitative data were collected on 'post-its' and analysed thematically. Results: 101 participants attended the study. 59.1% (n = 60) had >11 years' experience. 64% (n = 55) considered their summative and formative assessments were effective in developing student learning. Few participants reported students' involvement in creating their own assessments (n = 8; 9.75%). 41.68% (n = 36) participants agreed it was a good idea for students to be involved in developing assessments, but only 9.75% (n = 8) reported it was already happening. Qualitative data indicated a reluctance to wholeheartedly embrace technology (including AI) when planning assessments. Most participants were not in favour of Co-creation or the use of some technologies. Conclusions: Participants, reflected on the challenges of adopting a universal assessment approach. Dental educators should be given the institutional support and autonomy to implement the best assessment methods for their students. Most of this cohort of experienced dental educators reported that assessments facilitated student learning. Clinical significance: The role of assessment for dental students is essential as dental educators must ensure that dental students graduate with appropriate knowledge and technical skills to be safe when in general dental practice. The use of various assessment techniques needs to reflect the diversity of skills the students need to demonstrate
Color related to ceramic and zirconia restorations: a review
No full textThe requirement to achieve natural looking restorations is one of the most challenging aspects of dentistry, and the shade matching of dental restorations with the natural dentition is a difficult task due to the complex optical characteristics of natural teeth. Dental porcelain is considered the reference material for prosthetic rehabilitation, but it is not easy to handle and aesthetic excellence is quite difficult to obtain. For these reasons, shade matching with dental porcelain is often considered to be more artistic than scientific. Shade matching is considered unpredictable due to several variables that may influence the final appearance of a restoration. In order to improve this situation, over the last decade new shade guides and instruments have been developed and the aesthetic aspects of dental porcelain have been further investigated. In this review some aspects of color selection and color reproduction have been examined. Color selection has advanced through the development of new shade guides and electronic shade taking devices, although visual assessment has still not been entirely replaced by electronic instruments. Color reproduction with dental porcelain has improved thanks to advances in the performance and knowledge of dental porcelain, but is still not easy to achieve. The difficulties of achieving good aesthetics with PFM restorations and the desire for metal free solutions have resulted in the increased use of zirconia. The unique optical properties of zirconia have introduced new opportunities for achieving superior aesthetics, however further research is required with this material
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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