REVIEW ARTIC AODMR. Coloured Restoration

Transcription

1 REVIEW ARTIC CLE AODMR Shade Selection in Tooth Coloured Restoration Aditya Mitra, Chandrani Adhikari 1 Professor, Department of Conservative Dentistry and Endodontics, Guru Nanak Institute of Dental Sciences and Research; 2 Dental Surgeon, Department of Dentistry, R.G. Kar Medical College and Hospital, Kolkata. Address for Correspondence: Dr. Aditya Mitra, Professor, Department of Conservative Dentistry and Endodontics, Guru Nanak Institute of Dental Sciences and Research. ABSTRACT: The colour and appearance of teeth is a complex phenomenon, depending on many factors such as lighting conditions, translucency, opacity, light scattering, gloss. The human eye and brain influences the overall perception of tooth colour. In this article, we will discuss about the different methods of measurement of colour, technology based shade matching devices, guidelines of selection of shade and laboratory prescriptions. Keywords: Laboratory prescription, Shade guides, Shade matching devices. INTRODUCTION Continuous improvements of dental materials and consequent aesthetic enhancement of direct and indirect restorations require trained practitioner to be able to choose the right shade. However, the choice of shade for future restoration is not simple. Acquiring satisfying morphological, optical and biological form of a restoration is one of the most important goals of esthetic dentistry and dentistry in general. 1,4 Colour is defined as subjectivee perception of the quality of light and colorimetry is a scientific discipline which enables measuring and specifying the colour. 2,4 Basic knowledge about shades is prerequisite to make the right choice. In 1900, American painter and teacher of art Albert Henry Munsell wrote about triand parameters dimensional property of colour such as: hue, chroma and value or lightness. 3 MEASUREMENT OF COLOR Colour determination in dentistry can be divided into two categories: Visual Instrumental. Visual technique A popular system for visual determination of colour is the Munsell colour system, the parameters of which are represented in three dimensions. Value (lightness) is determined first by the selection of a tab that most nearly corresponds with the lightness or darkness of the colour. Value ranges from white to black. Chroma is determined with tabs that are close to the measured value but they are of increasing saturation of colour. Chroma ranges from achromatic or gray to a highly saturated colour. Hue is determined last by matching with colour tabs of the "value" and "chroma" already determined. Hue is measured on a scale from 2.5 to 10 in increments of 2.5 for each of the 10 colour families (red, R; yellow- GY; green, red, YR; yellow, Y; green-yellow, G; blue-green, BG; blue, B; purple-blue, PB; purple, P; red-purple, RP). Paravina evaluated a newly developed visual shade-matching apparatus, Shademat visual+ (SV+). The SV+ apparatus enabled better shade-matching resultss than daylight. Correlated colour temperature of the daylight varied from 4500 to 6800 K, while light intensity varied from 140 to 1000 lux. In SV+ trials, these values were constant at the measuring place: 5000 K and 1400 lux. There is a need for a more scientific and consistent means of shade matching in restorative dentistry. 5 12

2 translucent optical properties of teeth and dental ceramics. 5 Figure 1: Munsell Colour System Instrumental technique In this system, the colour space consists of three coordinates: L*, a* and b*. The L* denotes the lightness coordinate and its value ranges from 0 for perfect black to 100 for perfect white. The a* and b* are the chromaticity coordinates in the red-green axis and yellow-blue axis, respectively. Positive a* values refers to the red colour range and negative values denotes the green colour range. Similarly, positive b* values indicate the yellow colour range while negative values indicate the blue colour range. Instrumental colour analysis has a potential advantage over visual colour determination because instrumental readings are objective, can be quantified and are more rapidly obtained. Spectrophotometers and colorimeters have modifications and these modifications are in an attempt to overcome problems with visual shade matching in dentistry. Photoelectric tristimulus colorimeters have the potential to remove some of the shortcomings of the visual method and have been shown to provide accurate and repeatable measurements; but they are not error-free. In dentistry, the alteration of the results of a colorimetric device can occur as the standardized illuminating light emitted from the device may be scattered, absorbed, transmitted, reflected and even displaced in a sideways direction and these occurs due to the Figure 2: CIELAB system SHADE GUIDES Shade matching tools are called colour standards or shade guides. There are different types of colour standards for dentistry, depending on their purpose and the tissue for which they are intended. Tooth colour standards for oral soft-tissuestandards for facial prostheses-commonly and colour known as dental, gingival and facial shade guides, respectively are possible. Shofu offered the natural colour concept (NCC) on the other hand Vita introduced a 3- dimensional shade guide system (Vita 3D- consists of 208 Master). The NCC system colour blends based on 38 basic shades. The manufacturer purports that these blends are logically arranged in L* a* b* colour space according to Munsell hue, chroma and value. The shade guides and veneering material should be made of the same material in order to avoid the effect of metamerism. The Vita 3D-Master shade guide has a systematic colorimetric distribution of 26 shade tabs within the tooth colour space. Types of shade guide 7 The most popular shade guides currently used for dental shade matching are: - Vita Classic (Vita Zahnfabrik, Bad Sackingen, Germany) - Vitapan 3D-Master (Vita Zahnfabrik, Bad Sackingen, Germany) 13

3 - Chromascop (Ivoclar - Vivadent, Schaan, Liechtenstein) - Custom or specific chroma and value guides Vita Classic Shade Guide: It is a very popular shade guide, using since 1960 s. Tabs of similar hue are grouped into letter groups like: A (hue of red-yellow) - A1, A2, A3, A3.5, A4 B (hue of yellow) - B1, B2, B3, B4 C (hue of gray) - C1, C2, C3, C4 D (hue of red-yellow-gray) - D2, D3, D4 Chroma is designated with numerical values 1, 2, 3 and 4. THE PROBLEM WITH SHADE GUIDES 6 Shade guides have become the standard for selecting shade, although there have been many errors associated with the use of commercial shade guides. Problems that may arise include the following: 1. Finished porcelains do not match the shade guides that they are being compared to. 2. Different batch of porcelain from the same manufacturer may have different shade. 3. The porcelain piece which are used for the restoration are much thinner (1.5mm) than the shade guide tab ( 4-5 mm thick). 4. Shade guides are not always made with fluorescent porcelain, which causes unpredictability in colour matching. 5. It is difficult to predict the final shade after the layering of opaque, dentin and enamel. 6. Guide tabs lack a metal backing when using porcelain-fused to-metal restorations. 7. Shade tabs are condensed differently than the porcelain which used for final restorations. TECHNOLOGY BASED SHADE MATCHING DEVICES - Digital cameras Spectrophotometers Colorimeters. Spot measurement (SM) devices measure a small area on the tooth surface, on the other hand, complete-tooth measurement (CTM) devices measure the entire tooth. For SM devices, the size or diameter of the optical device aperture (generally about 3 mm 2 ) will 14 determine how much of the tooth surface and subsequent shade is measured. Examples of SM technologies are the Shofu ShadeEye- NCC chroma meter system and the Vita EasyShade system. CTM systems measure the entire tooth surface and provide a topographical map of the tooth in one image. Measurement of the complete surface gives the operator more consistent and reproducible information about the tooth structure. (5) DIGITAL CAMERAS Majority of consumer video or digital still cameras acquire red, green and blue image information that is utilized to create a colour image. The Red-Green- Blue (RGB) colour model is an additive model in which red, green and blue lights are added together in various ways to reproduce a broad array of colours. Although Digital cameras are the most fundamental approach to electronic shade taking, but it still requires a certain degree of subjective shade selection with the human eye. 8 The digital camera is extremely efficient and it can be easy used. Digital cameras capture images using charged coupled devices, which contain millions of microscopically small light-sensitive elements. The camera records each of the three colours at each pixel location and this is the most favourable thing about the digital camera. ClearMatch (Smart Technology, Hood River, OR) is a software system which uses highresolution digital images and compares shades over the entire tooth with known reference shades. 9 ShadeScan combine digital colour analysis with colorimetric analysis, while SpectroShade is the only one that combines digital colour imaging with spectrophotometric analysis. 5 SPECTROPHOTOMETERS - A spectrophotometer measures and records the amount of visible radiant energy reflected or transmitted by an object one wavelength at a time for each value, chroma and hue present in the entire visible spectrum. There are two

4 basic optical light settings used in reflectance spectrophotometer instruments: Illumination at 0 degrees and observation at 45 (0/45) or illumination at 45 and observation at 0 (45/0). As limited access is afforded by the oral cavity, only the 45/0 option is suitable for clinical use. When we compare the observations by the human eye, or conventional techniques with the spectrophotometers, it was found that spectrophotometers offered a 33% increase in accuracy and a more objective match in 93.3% of cases. 10 The SpectroShade (MHT Optic Research, Niederhasli, Switzerland) is the spectrophotometer developed for clinical use that combines digital imaging with spectrophotometric analysis. The unit consists of a high-intensity halogen light source that is directed to the tooth through fiber-optic bundles and lenses to uniformly illuminate the field at a 45 angle. The Vita EasyShade is a handheld spectrophotometer for tooth shade matching. The fiber optic tip is approximately 5 mm in diameter (SM technology) and contains nineteen 1 mm diameter fiber-optic fibers. Crystaleye, a new spectrophotometer, is an extremely precise dental colour analysis system, which provides extremely precise colour measurement based on spectral estimation using a LED light source. It combines the benefits of a traditional spectrophotometer with digital photography. With the development of optical and image processing technology, this product allows the practitioner to match tooth shade and colour more accurately and simply compared with the traditional spectrophotometer. 11 COLORIMETERS Colorimeters estimate the tristimulus values and filter light in red, green and blue areas of the visible spectrum. Colorimeters can t record spectral reflectance and in terms of accuracy, colorimeters are less effective than spectrophotometers. The aging of the filters of colorimeters also affect the accuracy ShadeVision (X-Rite, Grandville, MI) is an imaging colorimeter. Filter colorimeters mainly use three or four silicon photodiodes that have spectral correction filters. These filters act as analog function generators that limit spectral characteristics of light striking the detector surface. The scanning devices like spectrophotometers are superior to filter colorimeters because filter colorimeters are not able to match the standard observer functions. Because of their consistent and rapid sensing nature, these devices can be used for quality control. The Shade Eye NCC chroma meter is example of tristimulus colorimeter. The Shade Vision system is a device that combines digital colour image technology with colorimetric filtering technology. Kim-Pusateri S et al (2009) had done a study to evaluate the reliability and accuracy of 4 electronic devices (SpectroShade (spectrophotometer), ShadeVision (digital camera with colorimeter), VITA Easyshade (spectrophotometer), and ShadeScan (digital camera with colorimeter) for determining dental shades. They concluded that reliability percentages 99.0 for the ShadeVision, 96.9 for the SpectroShade, 96.4 for the VITA Easyshade, and 87.4 for the ShadeScan. Accuracy percentages were 92.6 for the VITA Easyshade, 84.8 for the ShadeVision, 80.2 for the SpectroShade, and 66.8 for the ShadeScan. The electronic shade-matching instruments had similarly high reliability, but differed substantially in accuracy. 12 SHADE SELECTION GUIDELINES 6 # The dentist must have a clear knowledge of the basic principles of colour. This allows for accurate shade selection. Munsell described the three dimensions of colour as hue, value and chroma. # Proper shade matching is not a very simple method, it can t be done only by holding the guide tab to the tooth in question. There are several methods which are used for accurate shade matching. They are as follows:

5 1. If patient is wearing bright clothing, he /she should be draped with a neutral coloured cover. 2. Patient should remove lipstick or other make-up. 3. The teeth are cleaned and all stains and debris are removed. 4. Patient's mouth should be at dentist's eye level. 5. The shade should be determined at the beginning of the appointmentt in order to avoid ocular fatigue. 6. Shade comparisons should be performed at five-second intervals so as not to fatigue the cone cells of the retina. 7. Value levels should be obtained by squinting. 8. Shade should be compared under varying conditions (i.e., wet vs. dry lips; retracted lip vs. pulled down lip). 9. The canine should be used as a reference for shade because of the highest chroma of the dominant hue of the teeth." 10. If it is not possible to precisely match shade, select a shade of lower chroma and higher value. 2. The shade tabs should be used in the shade guide rather than on their own in order to significantly increase the accuracy. 3. The incisal edge of the shade tab should be held to the incisal edgee of the tooth; the reflectance reduces afterimages. 4. The mid-buccal of the tooth is used to select the hue. 5. Shade should be evaluated by looking at the tooth from different angles (vectoring) to accommodate for curved translucent surfaces, the anisotropic properties of enamel, and the complex layering of the tooth structure. 6. Shade matching should be done minimum one month after bleaching to allow the enamel to rehydrate and achieve colour stability. CUSTOM SHADE GUIDES 6 The dentist should acquire a custom shade guide to properly start the shade matching process. The custom shade guides are the first step which are taken for better communication with the laboratory. The ceramists metal, porcelain, staining kits, equipment and techniques- all these are parts of custom shade guide. It also have pointers to indicate the exact point to notice during shade selection. A chart along with the guide is also necessary to send to the technician for giving any additional information which will help to understand the particular shade more clearly. The dentist may choose to create a luster tab and send it to the laboratory with the prescription. The technician will then have a visual aid for what he require to fabricate. Figure 3: Technological based shade matching devices; (a) Shadescan; (b) Spectro shade; (c) Vita easy shade; (d) Crystal eye; (e) Shade eye NCC; (f) Shade vision 11. The necks of the shade tabs should be grinded off because they tend to be darker than the rest of the shade tab. ADDITIONAL RECOMMENDATIONS Standardized full-spectrum light source always should be used under appropriate conditions while taking shades. 16 LABORATORY PRESCRIPTIONS 6 Most of the cases, the laboratory work authorizations do not request enough information from the dentist. The reason is - there is not enough space on the prescription to record it. For this reason, it is important to use a laboratory that fully understands the need for shade matching. Each laboratory prescription should contain enough space to record clinical information about each ceramic component of the restoration, e.g.- different shades of porcelain and opaque, and their position on the

6 tooth. In the official permission the dentist should include numerous diagrams of the tooth where he can draw helpful notes like shade, translucency, staining, glaze and surface texture etc. And the dentist should be in contact with the ceramist to ensure that the technician fully understands the requirements of the dentist. Through these methods that the dentist builds a relationship with the technician and the ceramists will usually return the quality that the dentist sends to them. MODELS Along with the laboratory prescription, the technician should have a set of study models to use as a guide. The information regarding occlusion, tooth alignment, position of soft tissue, diastema, surface texture, wear facets etc. can be obtained from preoperative models. A diagnostic wax-up will facilitate in the occlusion and form of the restoration. Shade matching is obviously only part of the task of replicating the natural tooth. PHOTOGRAPHY The macro lens is a valuable device for communication with the laboratory. It has been said that, "The photograph is the cosmetic dentist's radiograph." A magnification of either 1: I or 2: I helps the technician to determine the different properties of the particular tooth like colour, craze lines, stains, surface texture and luster. Multiple pictures at different angles and under different light sources should be taken. The photograph of patient's occlusion should be taken. -A picture of patient s smile also required besides the photograph of the teeth being work on. Because the patient s picture would give the technician regarding his/ her age, complexion, personality, shape of the face and profile. -A photograph at the time of try-in stage is also very useful. If colour adjustments are required, the technician will have a visual aid to help make the proper corrections. Written instructions alone are not always enough information for the technician. They leave a tremendous amount of room for interpretation. COMPUTERS Computers have become a important device for communication between the dentist and laboratory. Cosmetic imaging could replace the photographs. By an intraoral camera, the dentist can take a picture and send it over the Internet to the laboratory. With the elimination of film developing the time and money are also saved. By using these images the ceramist can fabricate proper prosthesis. -The dentist and laboratory can discuss regarding shade matching by sending . The ceramist may offer suggestions to the dentist based on the original images sent over the computer. When telephonic conversation is not possible due to lack of time of dentist, E- mail can be used to communicate with the dentist. -The dentist and ceramist can engage in realtime (15-second delay) consultations by modems and capture boards. This has the potential to allow for making immediate decisions about the restoration and will decrease the number of office visits of the patient. DENTAL LABORATORY PRESCRIP- TION The ideal prescription is a three dimensional representation of the shade-map, from several view points (vectoring). The facial surface is divided into 9-16 distinct zones. The surface texture and luster have an impact on the optical properties of the tooth and should be described. 20 So, at the end of the discussion we can say that some points we should remember during the shade selection for perfect reproduction of the natural looking restoration. 1.Incisal edges of the shade tab should be held at incisal edge of tooth. 2.Tooth should be viewed along its normal axis, using a diffuse light source and dentists eye should be at the level of patient s tooth, 17

7 distance should be 3-6 ft and viewing angle not less than 2⁰. 3.Mid Buccal of the tooth is used to select hue. 4.Shade can be selected by manual method - Vita classic or Vitapan 3D master or by means of shade matching devices like Digital camera, Spectrophotometer, Colourimeter. 5.After bleaching, shade matching should be delayed at least for 1 month to allow enamel to rehydrate and achieve colour stability. 6.Photographs of the tooth is taken at different angulations and stored in computer. 7.Manual instruction is given to laboratory technician. 8. and scan copy of photographs of tooth can be transferred to laboratory. CONCLUSION The comparison between visual and instrumental findings is a very attractive topic as it reveals pros and cons of both methods. Visual colour matching is subjective and influenced by variety of factors. However, this method is not inferior and should not be underrated. Actually, the development of all objective colour measuring devices depends upon the visual response of the standard observer and they are good only if they match that response. Additionally, the numerically smallest DE* value does not necessarily correspond to the best match because of the uneven eye sensitivity to hue, value and chroma differences. Therefore, the answer whether to use visual or instrumental method for color matching in dentistry is: if possible, use both, as they complement each other and can lead towards more predictable esthetic outcome. REFERENCES 1.Bayindir F, Kuo S, Johnston W, Wee A. Coverage error of three conceptually different shade guide systems to vital unrestored dentition. J Prosthet Dent 2007;98: Milićević V. Sistemi boja u stomatologiji. Stom Protet 1998;3: Curd FM, Jasinevicius RT, Graves A, Cox V, Sadan A. Comparison of the shade 18 matching ability of dental students using two light sources. J Prosthet Dent 2006;96: Andjelkovic A et al. Application of Advanced Technologies in Shade Matching A Spectrophotometer. Serbian Dental Journal 2010;57(4). 5.Agrawal VS et al. Color and shade management in esthetic dentistry. 2013;3(3): Shade selection and matching: Dental clinic home pages; Health Mantra. 7.Shammas M et al. Colour and Shade Matching in Dentistry Trends Biomater. Artif Organs 2011;25(4): Blaes J. Today s technology improves the shade-matching problems of yesterday. Journal of Indiana Dental Association ;81: Ristic I, Paravina RD. Color measuring instruments. Acta Stomatologica Naissi 2009;25: Paul S, Peter A, Pietrobon N, Hammerle CH. Visual and spectrophotometric shade analysis of human teeth. Journal of Dental Research 2002;81: Da Silva JD, Park SE, Weber HP, Ishikawa-Nagai S. Clinical performance of a newly developed spectrophotometer system on tooth color reproduction. Journal of Prosthetic Dentistry 2008;99: Kim-Pusateri S, Brewer J, Davis EL, Wee AG. Reliability and accuracy of four dental shade-matching devices. Journal of Prosthetic Dentistry 2009;101: Joiner A. Tooth colour: a review of the literature. J Dent 2004;32: Baharin SA et al. Anterior Tooth Shade Selection Procedure: Influence of Light Sources and Patient s Position. Sains Malaysiana 2013;42(1): Afrashtehfar KI. Increased Predictability in Tooth Shade-Matching, How to cite this article: Mitra A, Adhikari C. Shade Selection in Tooth Coloured Restoration. Arch of Dent and Med Res 2017;3(3):12-18.