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ORIGINAL RESEARCH Table of Contents   
Year : 2008  |  Volume : 19  |  Issue : 3  |  Page : 191-195
A study on reproducing silicone shade guide for maxillofacial prostheses matching Indian skin color


Department of Prosthodontics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad - 580 009, Karnataka State, India

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Date of Submission11-May-2007
Date of Decision19-Nov-2007
Date of Acceptance21-Nov-2007
 

   Abstract 

Aim: The value and success of a well-fitting and anatomically correct prosthesis are compromised if the color does not match the adjoining tissues. The use of powder colors to help develop a simplified silicone shade guide to aid in the fabrication of silicone facial prostheses for Indian patients has been described here.
Materials and Methods: Ten powder pigments were used to fabricate the silicone samples for three different subjects having light, medium and dark complexions who were separated into three groups depending on the value of their shades. Four-step wedge silicone samples with thickness variations of 1, 2, 4 and 6mm were fabricated. Visual assessment of the samples was done by four evaluators to check the agreement of color match. Data was statistically analyzed using kappa coefficients.
Results: The kappa values were found to be 0.09-0.44 for a light skin tone, -0.11 to 0.77 for medium skin and 0.44 to 0.85 for dark skin tones. This study showed that the samples of dark skin tone matched the skin tone well and showed a statistically good agreement. To further test the validity of these shade guides, facial silicone veneers were fabricated for three patients having light, medium and dark complexion. The color matching showed satisfactory results.
Conclusion: The silicone veneers matched the skin color of all three patients. Hence, this shade guide will help clinicians to obtain a good intrinsic shade and minimize extrinsic coloration.

Keywords: Maxillofacial prostheses coloring, shade matching, silicone shade guide

How to cite this article:
Guttal SS, Patil NP, Nadiger RK, Kulkarni R. A study on reproducing silicone shade guide for maxillofacial prostheses matching Indian skin color. Indian J Dent Res 2008;19:191-5

How to cite this URL:
Guttal SS, Patil NP, Nadiger RK, Kulkarni R. A study on reproducing silicone shade guide for maxillofacial prostheses matching Indian skin color. Indian J Dent Res [serial online] 2008 [cited 2014 Nov 27];19:191-5. Available from: http://www.ijdr.in/text.asp?2008/19/3/191/42949
The increase in acquired facial defects resulting from cancer surgeries, automobile accidents leading to facial trauma and congenital facial defects, has led to an increased demand for maxillofacial prostheses. The materials used in the fabrication of these prostheses can be silicones that are tinted externally and internally to match the color of the surrounding structures. The value and success of well-fitting and anatomically correct prostheses are compromised if the color does not match the adjoining tissue. Hence, a prosthesis that is given a solid flat color is unrealistic and will appear artificial. [1],[2]

The major source of color in human skin are specialized melanin-bearing organelles, the melanosomes present within the epidermis. Gross human skin color derives from the visual impact of the the sum of the melanin pigmentation of the numerous epidermal melanin units. Melanin occurs in two types: 1) black to brown eumelanin and 2) yellow to reddish pheolmelanin. [3] Melanosomes in keratinocytes of light skin are membrane-bound clusters, whereas melanosomes in keratinocytes of dark skin tend to be larger and distributed individually. It has been shown that melanosomes within keratinocytes of Asian skin are distributed as a combination of individual (62.6%) and clustered (37.4%) melanosomes. [4] It has been concluded that the melanosome distribution in keratinocytes of Asian skin is intermediate between light Caucasian and dark African. Hence, yellowish brown is the predominant color for Indian skin.

Color matching of facial prostheses to human skin has long been a challenge to the clinician. Many different materials and methods have been documented. [5],[6],[7],[8],[9],[10] Earlier extrinsic coloring was done to achieve a desired skin tone. [11],[12],[13] Barnhart [5] achieved a more natural, deeper, and long-lasting skin tone by intrinsically coloring silicone rubber with commercially available, colored methymethacrylate powders. The technique involved an easily reproducible specific color whenever required.

Color reproduction in facial prostheses was tried by adding inorganic pigment powders to clear methylmethacrylate powder and then applying these intrinsically to a medical-grade silicone rubber. [6] Inorganic pigments were directly added to silicone rubber. [8] A tattooing machine [9] and an artist's spray gun [7] were used to apply pigments. Godoy et al, [1] developed an acrylic resin shade guide by mixing different dry earth pigmens with a roch wax carver and a Hue-Friedy cleoid discoid carver, which carried loads of up to an average of 0.0158 g and 0.0024 g, respectively. There are many studies [5],[11],[14] explaining the different techniques of color reproduction but the literature is scanty with respect to the studies concerning silicone color matching that of Indian skin. Hence, the purpose of this study was to develop a simplified silicone shade guide which matches the Indian skin color. This guide will help the prosthodontist to obtain a good intrinsic shade and minimize extrinsic coloration for Indian patients.


   Materials and Methods Top


Room temperature vulcanizing silicone (Silastic, Factor II, Lakeside, Az) was selected as the base material for the shade guide and facial prostheses because of its reported advantages over acrylic resin and polyvinyl chloride. [15] The powder pigments (Camlin Ltd, Mumbai, India) used were synthetic inorganic iron oxides [Table 1]. They were all nontoxic and blended well with silicone. Three subjects were chosen to represent the three basic tones: 1) light, 2) medium and 3) dark complexion found in the Indian population. Each of these basic tones was divided into three groups depending on the value of their shades [Figure 1].

A four-step wedge wax pattern with thickness variations of 1, 2, 4 and 6 mm [Figure 2] was prepared. Each step specimen had an area of 1.5 cm 2 , providing an adequate area of silicone for visual matching. The wax pattern was invested and wax elimination was done [Figure 3]. Unpigmented silicone (Factor II) was packed into the mold and processed. These were used to assess the coloring effect of the pigments on the processed silicone base material. The powder pigments were added to a length of 6 cm of silicone laid on a glass slab. The pigments were added with the help of a spoon excavator. One load of pigments in the spoon added up to an average of 0.001 g. This was measured with a digital analyzer. Each load of pigments in the spoon excavator was considered as one load and the numbers of loads were added for each pigment. As most prosthodontists may not have a precision balance, we used volumetric amounts of stock powder pigments obtained from the spoon excavator to develop the shades. The powder pigments were dispersed in the silicone by mixing with a spatula. After the desired color was achieved, a small amount of colored silicone was placed in the center of a folded transparent plastic sheet and tested with the patients' malar skin under daylight. Then, the silicone was packed into the four-step wedge mold and cured at room temperature. Visual evaluation was done independently by the primary author and by three other evaluators. The evaluators were screened for color vision deficiency. All the evaluators underwent the Ishihra chart test and were not found to be color vision-deficient. The visual assessment of color matching was done based on a score sheet using a scoring system. The scoring system was defined as follows: 1-different and unacceptable, 2-nearly same but acceptable, 3-satisfactory color match and 4-exact color match. The samples were secured to the malar skin of the patients using a small amount of transparent, secure medical adhesive and transparent adhesive tape [Figure 4]. Each evaluator assigned scores for each silicone sample and repeated the scoring 15 times for the same sample. Similarly, the procedure was carried out for the other two subjects with medium and dark complexions. By the process of elimination and the addition of other selected colors, various proportions of colors were mixed together and processed to give new shades, thus forming a range of skin shades for the skin shade guide [Figure 5]. The compositions of the shade guide samples representing the basic skin tones found in the Indian population are listed in [Table 2],[Table 3],[Table 4].

Furthermore, to test the reproducibility of the shade guide, samples in the form of textured veneers or onlays were constructed for the three patients representing light, medium and dark skin. These samples covered the zygomatic prominence of the face so that a direct comparison of the shade of material with immediately adjacent skin tone was possible. The impression of the malar area of the face was made with light body polysiloxane (Aquasil, Dentsply, Caulk, Milford, Del). The impression was coated with a thin layer of petroleum jelly. The silicone mix was prepared and polymerized on the impression using the corresponding skin shade guide [Figure 6]. These silicone veneers were placed on the malar region and secured with medical grade adhesive. These samples were photographed in day light using a Nikon Coolpix 4100 digital camera at a distance of 30 cm between the subject and the lens.

Four independent observers evaluated the three samples for each of the patients to check the color match [Figure 7],[Figure 8],[Figure 9]. Statistical analysis (Intercooled stata 9.2 version, Tx, USA) of the data was performed using Kappa coefficient (kappa statistics) to assess the agreement among the evaluators. The level of significance was set at P < 0.05.


   Results Top


The interexaminer results for the four-step wedge silicone samples showed moderate agreement for the light skin tone; the kappa values ranged from 0.09 to 0.44 [Table 5]. Kappa showed moderate to good agreement with the values ranging from -0.11 to 0.77 for the medium skin tone [Table 6]. The evaluation of silicone samples for dark skin tone showed good agreement. The kappa values for dark skin tone ranged from 0.44 to 0.85 [Table 7]. All four evaluators calculated the kappa coefficient for each skin tone.

Qualitative evaluations of the silicone veneers were done; the veneers matched the skin tone. Subjective and objective evaluation of the silicone veneers was done. All the three subjects chosen for the study were satisfied with the color match.


   Discussion Top


Edwards and Duntly [16] attributed skin color to five pigments: melanin, melanoid, oxyhemoglobin, reduced hemoglobin and carotene, which are found in different layers of the skin. The absorptive characteristics of these skin pigments, especially of melanin, contribute to the total reflected light and determine the hue, value and saturation of the skin color. Wasserman, [17] in an extensive spectrophotometric analysis of skin color in different racial groups, found that irrespective of race, the dominant reflected hue is red. Differences between races and the different variances in the same population group are governed by the melanin content. [16],[17],[18] Saturation varies markedly but it is highest in brown skin and lower in white. [17] The Indian population has more melanin content, hence, the basic tone is yellowish brown.

Techniques for the evaluation of skin color include visual examination, comparision with standard color guides and use of colorimetry, spectrophotometry and reflectometry. [17],[19] Visual examination was used to evaluate the skin color by four different evaluators in this study. It is the most cost-effective method compared to the more expensive spectrophotometry and reflectometry. [20] However, any technique that increases longevity, reduces fabrication time and provides esthetically acceptable prostheses warrants further consideration. [8] All these criteria have been met by utilizing stock pigments and the visual examination technique in this study.

In the present study, all the evaluators found that stepwise thickness of the samples matched the patient's skin to the best of all depths. Lesser depths allowed the patient's skin color to show through, as on the margins of prostheses. This has a clinical application because most prostheses have thin margins that are <1 mm. There was perfect agreement (73-93%) among the evaluators for the dark skin tone. The agreement decreased for the light skin tone. All the evaluators had given scores between 2 and 3 and hence, it may be inferred that matching light skin shades is difficult in the Indian population. Clinically, the color formulas used were consistently repeatable. This was tested by matching the silicone veneers for different subjects. There was no extrinsic coloring done for the veneers. The color shade guide showed superior results with intrinsic coloring. However, the veneers would have shown excellent results in shade matching after the addition of external tinting. For external tinting, same colors can be used for the corresponding skin tone as given in [Table 2],[Table 3],[Table 4].

The limitations of this study are as follows: 1) visual assessment may be error-ridden in accurate shade matching, 2) The results may vary if the materials are changed. The use of this color formula gives a basic guide for skin color matching. Further efforts are warranted to study the skin color of the Indian population using spectrophotometry.


   Conclusion Top


Esthetics is an important factor for a patient's acceptance of a facial prosthesis. This study would be of value to prosthodontists who fabricate facial prostheses for the Indian skin color. A silicone shade guide has been developed using stock powder pigments. The predominant colors that match the Indian skin color are yellow ochre, light red, burnt umber, burnt sienna and Vandyke brown. When necessary, these shades can be altered by changing the proportions of a given formula.


   Acknowledgments Top


The authors gratefully acknowledge the support and encouragement given by Dr. C. Bhasker Rao. The authors acknowledge Dr. Ashith Acharya for his assistance in the manuscript preparation.

 
   References Top

1.Godoy AJ, Lemon JC, Nakamura SH, King GE. A shade guide for acrylic resin facial prosthesis. J Prosthet Dent 1992;68:120-2.  Back to cited text no. 1  [PUBMED]  
2.Clark EB. The colors problem in dentistry: A practical application of the primary psychological colors. Dent Dig 1931;37:571-82.  Back to cited text no. 2    
3.Ito S, Wakamatsu K. Quantitative analysis of eumelanin and pheomelanin in humans, mice, and other animals: A comparative review. Pigment Cell Res 2003;16:523-31.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Thong HY, Jee SH, Sun CC, Biossy RE. The patterns of melanosome distribution in keratinocytes of human skin as one determining factor of skin color. Br J Dermatol 2003;149:498-505.  Back to cited text no. 4    
5.Barnhart GW. A new material and technic in the art of somato-prosthesis. J Dent Res 1960;39:836-44.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Tashma J. Coloring somatoprostheses. J Prosthet Dent 1967;17:303-5.  Back to cited text no. 6  [PUBMED]  
7.Ouelette JE. Spray coloring of silicone elastomer maxillofacial prosthesis. J Prosthet Dent 1969;22:271-5.  Back to cited text no. 7    
8.Firtell DN, Bartlett SO. Maxillofacial prostheses: Reproducilble fabrication. J Prosthet Dent 1969;22:247-52.  Back to cited text no. 8  [PUBMED]  
9.Schaff NG. Color characterizing silicone rubber facial prosthesis. J Prosthet Dent 1970;24:198-202.  Back to cited text no. 9    
10.Fine L, Robinson JE, Brnhart GW, Karl L. New method for coloring facial prosthesis. J Prosthet Dent 1978;39:643-9.  Back to cited text no. 10    
11.Kazanjian VH, Rowe AT, Young HA. Prosthesis of the mouth and face. J Dent Res 1932;12:651.  Back to cited text no. 11    
12.Bulbulian AH. Congenital and postoperative loss of the ear. Dent Digest 1942;48:472.  Back to cited text no. 12    
13.Fonder AC. Dental materials and skill in oral and facial prosthesis. J Am Dent Assoc 1955;50:636.  Back to cited text no. 13  [PUBMED]  
14.Gillman MB. Color matching: Matching skin color in facial prosthesis via the spectrophotometer with special reference to dental restorations demanding color fidelity. Dent Items Interest 1950;72:1250-5.  Back to cited text no. 14  [PUBMED]  
15.Roberts AC. Silicones for facial prosthesis. Dent Pract Dent Rec 1971;21:276.  Back to cited text no. 15  [PUBMED]  
16.Edwards EH, Duntley QS. The pigments and color of living human skin. Am J Anat 1939;65:1-4.  Back to cited text no. 16    
17.Wasserman HP. The color of human skin. Dermatologica 1971;143:166.  Back to cited text no. 17    
18.Buckley WR, Green F. Reflection spectrophotometry. Arch Dermatol 1961;89:110.  Back to cited text no. 18    
19.Barnicot NA. Reflectometry of the skin in southern Nigerians and some in mulattoes. Hum Biol 1958;30:150.  Back to cited text no. 19  [PUBMED]  
20.Cantor R, Webber RL, Sround L, Ryge G. Method for evaluating prosthetic facial materials. J Prosthet Dent 1969;21:324.  Back to cited text no. 20    

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Correspondence Address:
Satyabodh S Guttal
Department of Prosthodontics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad - 580 009, Karnataka State
India
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DOI: 10.4103/0970-9290.42949

PMID: 18797093

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]

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