Rosa Pulgar

Color and translucency in silorane-based resin composite compared to universal and nanofilled composites

OBJECTIVES The purpose of this study was to determine the optical properties, color and translucency, of the new silorane-based resin composite and to compare it to universal dimethacrylate-based composites. METHODS Six dimethacrylate-based resin composites and one silorane-based resin composite (all A2 shade) were studied. Color of non-polymerized and polymerized composites was measured against white and black backgrounds using a spectroradiometer. Changes in color (ΔE*(ab)), translucency (ΔTP) and color coordinates (ΔL*, Δa* and Δb*) were calculated for each resin composite. Results were evaluated using a one-way ANOVA, a Tukeys test and a t-test. RESULTS The polymerization-dependent ΔE*(ab) ranged from 4.7 to 9.1, with the smallest difference for the silorane-based resin composite. The color changes of silorane-based composite were due to the changes of coordinates Δa* and Δb*. However, for the dimethacrylate-based composites, the color changes mainly originated by ΔL*and Δb*. The silorane composite exhibited the smallest TP values. Tukeys test confirmed significant statistical differences (p<0.05) between mean TP values of Filtek Silorane and each brand of dimethacrylate-based composites before and after polymerization. CONCLUSIONS The new silorane-based restorative system showed different optical properties compared to clinically successful dimethacrylate composites. The silorane composite exhibited better polymerization-dependent chromatic stability, and a lower translucency compared to other tested products.

Prediction of color change after tooth bleaching using fuzzy logic for Vita Classical shades identification.

Tooth bleaching is becoming increasingly popular among patients and dentists since it is a relatively noninvasive approach for whitening and lightening teeth. Instruments and visual assessment with respect to commercial shade guides are currently used to evaluate tooth color. However, the association between these procedures is imprecise and the degree of color change after tooth bleaching is known to vary substantially between studies; there are currently no objective guidelines to predict the effectiveness of a tooth-bleaching treatment. We propose a new methodology based on fuzzy logic as a natural means of representing the imprecision present when modeling the color change produced by a tooth-bleaching treatment on the basis of a tooths initial chromatic values. This system has the advantage of producing a set of interpretable fuzzy rules that can subsequently be used by scientists and dental practitioners. The fuzzy system obtained has the special characteristic whereby the rule antecedents correspond to prebleaching shades of the well-known Vita commercial shade guide. Additionally, the rule consequents directly correspond with the expected CIELAB postbleaching values for each Vita shade, thanks to a modification of the systems inference structure. Finally, the values of these postbleaching CIELAB coordinates have been associated with Vita shades by evaluating their respective membership functions, thereby approximating which posttreatment Vita shades are to be expected for each prebleaching shade.

Local-global neuro-fuzzy system for color change modelling

Color change modelling is an essential problem in a wide range of colorimetric applications. Specifically, the approximation to the color expected after a physical chemical or natural color is essential in industry and in color science in general. This work proposes a modified neuro-fuzzy approach as a solution for a color change modelling problem. Neuro-fuzzy systems are well known methods for data modelling; their main advantage is their ability to provide an accurate solution from which an interpretable set of rules that can be extracted and used by the scientists. However these models have the problem that the global approximation optimization can lead to a deficient interpretation of the rules extracted from the model. This work proposes a modified neuro-fuzzy model that performs a simultaneous global and local modelling; this property is reached thanks to a special partitioning of the input space in the system. Specifically, the proposed methodology will be applied to a very important problem from the clinical and odontologic point of view as it is the modelling of the tooth color variation after a bleaching process. The availability of tools that help to predict these changes, from the initial chromaticity of the tooth, can solve the problem of lack of information on the expected tooth color after a specific treatment and help the dentist in the decision making on the most appropriate protocol for this treatment and in providing adequate information to the patient.

A Data Mining Approach Based on a Local-Global Fuzzy Modelling for Prediction of Color Change after Tooth Bleaching Using Vita Classical Shades

Tooth bleaching is receiving an increasing interest by patients and dentists since it is a relatively non-invasive approach for whitening and lightening teeth. Instrument designed for tooth color measurements and visual assessment with commercial shade guides are nowadays used to evaluate the tooth color. However, the degree of color change after tooth bleaching varied substantially among studies and currently, there are no objective guidelines to predict the effectiveness of a tooth bleaching treatment. Fuzzy Logic is a well known paradigm for data modelling; their main advantage is their ability to provide an interpretable set of rules that can be later used by the scientists. However these models have the problem that the global approximation optimization can lead to a deficient rule local modelling. This work proposes a modified fuzzy model that performs a simultaneous global and local modelling. This property is reached thanks to a special partitioning of the input space in the fuzzy system. The proposed approach is used to approximate a set of color measurements taken after a bleaching treatment using the pre-bleaching measurements. The system uses as rule antecedents the colorimetric values of the VITA commercial shade guide. The expected post-bleaching colorimetric values are immediately obtained from the local models (rules) of the system thanks to the proposed modified fuzzy model. Additionally, these post-bleaching CIELAB coordinate values have been associated with VITA shades through the evaluation of their respective membership functions, approximating which VITA shades are expected after the treatment for each pre-bleaching VITA shade.

A model for prediction of color change after tooth bleaching based on CIELAB color space

An experimental study aiming to develop a model based on CIELAB color space for prediction of color change after a tooth bleaching procedure is presented. Multivariate linear regression models were obtained to predict the L*, a*, b* and W* post-bleaching values using the pre-bleaching L*, a*and b*values. Moreover, univariate linear regression models were obtained to predict the variation in chroma (C*), hue angle (h°) and W*. The results demonstrated that is possible to estimate color change when using a carbamide peroxide tooth-bleaching system. The models obtained can be applied in clinic to predict the colour change after bleaching.

Color Fuzzy Set Design for dental applications

This work presents a Color Fuzzy Set Design procedure, or similarly a color naming procedure, based on the VITA Classical dental color shade guide, for composite color matching applications in direct restorations in aesthetic dentistry. For that purpose, a psychophysical experience based on a set of visual assessments by a panel of observers was performed, with the objective of identifying the areas of the CIELAB color space which can be associated to each shade of the VITA guide. A number of composite sets from four different manufacturing companies were used in the experiment. This information was processed and a set of nonparametric Fuzzy Sets was obtained for the VITA shades, with the aid of an acceptability dental color threshold taken from previous studies. The designed Fuzzy Set System was applied for the identification of the VITA shade of different dentine and enamel composite samples (bilaminar technique) from two different manufacturing companies, with the subsequent clinical applicability. Results show a high level of accuracy in VITA shade identification of the operated dental samples, when compared with visual assessment performed by experts.