Translucency thresholds for dental materials

Objective

To determine the translucency acceptability and perceptibility thresholds for dental resin composites using CIEDE2000 and CIELAB color difference formulas.

Color differences: Polymerized composite and corresponding Vitapan Classical shade tab

ObjectivesThis study compared newer composite resin restorative materials to the Vitapan Classical tabs they purported to represent.MethodsFive Vitapan Classical tabs were studied: A3.5, B2, C1, C3, and D2 (n = 3). These tabs created a variety of levels of lightness, chroma and hue. Each of these five shade tabs was removed from three different shade guides, and an intraoral spectrophotometer was used to capture CIELAB color coordinates. Three separate readings were made and all nine were averaged. The inter-tab color differences were also calculated. Five specimens approximately 4.0 mm thick were fabricated for each of the shades studied using five different composite resin materials. Composite specimens were of the same size and shape as target shade tabs, and three separate recordings were made for each of them. This average was compared to five Vitapan Classical shade tabs to calculate the color differences using both CIELAB and CIEDE2000 color difference formulas. Color differences were compared to thresholds for perceptibility and acceptability reported in other studies.ResultsCIELAB and CIEDE2000 color differences ranged from 3.9 to 22.8 and from 2.1 to 13.8, respectively. None of the materials proved, an acceptable CIELAB color match to any of the shades tested.ConclusionWhen various shade tabs of Vitapan Classical shade guides were compared with correspondent tabs made of direct restorative composites, no material/shade combination resulted in an acceptable mismatch relative to the used standard of acceptability. Therefore, evaluated resin composites exhibited poor match compared to target Vitapan Classical tabs.     

Perceptibility and acceptability of CIELAB color differences in computer-simulated teeth

OBJECTIVES: To determine the perceptibility and acceptability of tooth color differences using computer-generated pairs of teeth with simulated gingival displayed on a calibrated color monitor using appropriate signal detection theory methodology (SDT). METHODS: Twelve dental professionals (four from each of the following groups: dentists, dental auxiliaries, and fixed prosthodontic technicians) and four dental patients served as subjects. Responses to tooth color differences (DeltaE) were measured on each of the three principal axes of CIELAB color space (L*, a*, and b*). As a control, responses to DeltaE=0 (the false alarm rate) were also measured in the same experimental session. RESULTS: No group differences among subjects were found. All gave 50% match or acceptance points that averaged about 1.0 DeltaE units in the L* and a* directions, and 2.6 units in the b* direction. False alarm rates across all subjects averaged 27% (4-55%) and 28% (0.4-61%), respectively, for perceptibility and acceptability. A reanalysis of the data based on SDT, which takes subjects' false alarm rates into account, gave somewhat larger color difference thresholds. CONCLUSIONS: Color difference thresholds for our simulated teeth are generally in line with and extend results obtained with studies using "real" dental materials. No differences between thresholds for acceptability versus perceptibility were found. Furthermore, subjects often reported color differences when none existed, and this behavior needs to be factored into any determination of quality control standards for the fabrication of dental prostheses.     

Comparison of CIELAB DeltaE(*) and CIEDE2000 color-differences after polymerization and thermocycling of resin composites.

OBJECTIVES: Though instrumental technologies have been widely used for quantifying color of esthetic dental materials, the sizes for the perceptible or acceptable color-difference varied. Instead of the CIELAB DeltaE(*)(DeltaE(ab)(*)) formula, the CIEDE2000 (DeltaE(00)) formula that included weighting and parametric functions was introduced. The objective of this study was to determine the correlation between color-difference values of DeltaE(ab)(*) and DeltaE(00) after polymerization and thermocycling of dental resin composites. METHODS: Color-differences were calculated between unpolymerized and polymerized, and between polymerized and thermocycled resin composites. Color was measured relative to the standard illuminant D65 over a white background with SCE geometry. Regression analyses were performed between the color difference values of DeltaE(ab)(*) and DeltaE(00). RESULTS: There were significant correlations between DeltaE(ab)(*) values and DeltaE(00) values after polymerization and thermocycling (p<0.01), and the correlation coefficient was 0.99 and 0.98, respectively. SIGNIFICANCE: Within the limit of this study, the results suggest that two color-difference formulas can be used interchangeably for the evaluation of the color-difference of resin composites after polymerization and thermocycling. However, for the evaluation of changes in separate color parameters such as lightness, chroma and hue, the DeltaE(00) formula could be considered for the color evaluation of esthetic dental materials after confirming with human observer responses.     

Correlations between Color Differences Based on Three Color-Difference Formulas Using Dental Shade Guide Tabs

Purpose: The purpose of this study was to determine the correlation among color-difference values based on three formulas between shade tab pairs from two shade guides [Vita Lumin (VITA) and Chromascop (CHRO)].
Materials and Methods: The color of shade tabs was measured relative to the standard illuminant D₆₅ under the 8° standard observer function, and distributions for CIE L *, a *, and b * values were compared. One hundred and twenty shade pairs from VITA and 190 shade pairs from CHRO were used to calculate color differences using CIELAB, DIN99, and CIEDE2000 formulas (Δ E*_ab , Δ E ₉₉, and Δ E ₀₀, respectively). A paired t- test was used to determine the difference between each pair of the three color-difference values (α= 0.01). Regression analysis was used to determine the correlations between the color differences (α= 0.01).
Results: For both shade guides, there were significant differences between Δ E*_ab and Δ E ₀₀, Δ E*_ab and Δ E ₉₉, and Δ E ₉₉ and Δ E ₀₀ ( p < 0.01). Δ E*_ab and Δ E ₀₀, and Δ E*_ab and Δ E ₉₉ were strongly correlated (r²= 0.90 to 0.94, p < 0.05). Although a simplified a * rescaling function of the CIE a * axis has been added in the CIEDE2000 formula, the influence of the opposite signs in the a * value were found to be irrelevant to the Δ E ₀₀ value.
Conclusion: Δ E*_ab, Δ E ₉₉, and Δ E ₀₀ can be used interchangeably for the evaluation of color difference of shade tabs.     

Intraoral determination of the tolerance of dentists for perceptibility and acceptability of shade mismatch

STATEMENT OF PROBLEM: There is little agreement in the dental literature as to how much color difference constitutes an acceptable shade mismatch or how much color difference is considered perceivable to observers. Most studies attempting to determine perceptibility and acceptability of tolerances for shade mismatches have been conducted under in vitro conditions that are not applicable to clinical scenarios. PURPOSE: The goal of this study was to determine valid acceptability and perceptibility tolerances for shade mismatch in an actual clinical scenario using spectroradiometric instrumentation. MATERIAL AND METHODS: A test denture was fabricated that allowed 10 maxillary left central incisors of varying shade mismatch with the right central incisor to be interchanged within the denture base. A spectroradiometer was used to determine the CIELAB coordinates and color differences (DeltaE) between the right central incisor and the interchangeable left central incisor denture teeth. The interchangeable denture teeth ranged uniformly from 1 DeltaE unit (visually undetectable) to greater than 10 DeltaE units (an obvious shade mismatch). The test denture with each of the interchangeable teeth was modeled by a subject to 28 dentists in a clinical setting. For each of the interchangeable teeth, dentist observers were asked if they could see a difference between the central incisors and, if so, whether the difference was acceptable. A Probit regression analysis was used to predict acceptability and perceptibility tolerances with 95% confidence limits. RESULTS: The predicted color difference at which 50% of the dentist observers could perceive a color difference (50/50 perceptibility) was 2.6 DeltaE units. The predicted color difference at which 50% of the subjects would remake the restoration due to color mismatch (clinically unacceptable color match) was 5.5 DeltaE. Acceptability and perceptibility color tolerances at the 50/50 level were significantly different (P<.05), as their 95% confidence limits did not overlap. CONCLUSIONS: Tolerances for perceptibility were significantly lower than tolerances for acceptability for shade mismatch between 2 denture teeth.     

In vitro evaluation of color change in maxillofacial elastomer through the use of an ultraviolet light absorber and a hindered amine light stabilizer

STATEMENT OF PROBLEM: External prostheses composed of silicone elastomers exhibit an unwanted color change over time. PURPOSE: This study evaluated color stability when an ultraviolet light absorber and hindered amine light stabilizer were mixed in the maxillofacial elastomer containing either organic or inorganic pigments. MATERIAL AND METHODS: The materials used were an RTV silicone elastomer, 1 natural inorganic dry-earth pigment (burnt sienna) and 2 synthesized organic pigments (hansa yellow and alizarin red), ultraviolet light absorber (UVA) and hindered amine light stabilizer (HALS). Specimens (n=160) were fabricated in a custom mold and randomly assigned and exposed to weathering sites in Miami and Phoenix for approximately 3 months. Eight test groups (2 of each 4 material types with or without additives) of 10 specimens each were assigned to each site. L*, a*, b* readings were obtained before and after weathering from a spectrocolorimeter. Nonpigmented elastomers served as the control. Three-factor ANOVA was conducted to examine interaction effects between weathering sites, specimen type, and the presence of additive (alpha=.05). Overall color change (Delta E) and change in color coordinates (Delta L*, Delta a*, Delta b*) of specimen groups with and without additive were analyzed with independent sample t tests. RESULTS: In specimen groups with the additives (UVA and HALS), color change decreased significantly (P<.05) in burnt sienna and hansa yellow in Phoenix and in the control and hansa yellow in Miami. Additives did not affect color change in the alizarin red group. CONCLUSION: UVA and HALS were shown to be effective in retarding color change in some circumstances.     

Comparison of CIE lab, CIEDE 2000, and DIN 99 color differences between various shades of resin composites

PURPOSE: In addition to the CIE Lab color-difference formula (deltaE*ab), advanced formulas that include weighting functions have been introduced. The objectives of this study were to determine the correlations in color differences between different shade pairs of resin composites by different color formulas, and to determine whether the weighting functions included in the advanced formulas influenced the color-difference values. MATERIALS AND METHODS: Color was measured after polymerization of two resin composites in 26 shades, and color differences between shades were calculated by deltaE*ab, CIEDE 2000 (deltaE00), and DIN 99 (deltaE99) formulas. Regression analyses were performed between the color differences calculated by three formulas in each group divided by the differences in color parametric factors between the pairs compared. RESULTS: There were significant correlations between deltaEab and deltaE00, deltaEab and deltaE99, and deltaE99 and deltaE00 (r2 = .99, .89, and .90, respectively). The weighting functions in the CIEDE 2000 formula had influence on deltaE00 values when differences in chroma and hue between compared pairs were great. CONCLUSION: Differences in parametric factors between the pairs compared influenced the correlation between deltaE*ab and deltaE99 values (r2 = .25 to .97). As the CIEDE 2000 formula has been proven to be better matched to observer responses and showed significant involvement of weighting functions compared to CIE Lab color difference, this formula should be considered for evaluation of the color of resin composites.     

Evaluation of polymerization-dependent changes in color and translucency of resin composites using two formulae

The aim of this study was to evaluate polymerization-dependent changes in the color and translucency parameter (TP) of resin composites and to compare results obtained using two color-difference metric formulae, CIELAB and CIEDE 2000. Twenty-eight shades of commercial resin composites were analyzed. Specimens (n = 5) were made as discs, 11 mm in diameter and 2-mm thick, using cylindrical molds. Data were collected before and after composite polymerization, using a spectrophotometer. In regard to in vitro color changes of composites (ΔE*) a ΔE₇₆ of 3.7 or greater was considered to be an unacceptable color change. Data were analyzed by analysis of variance, and Fisher’s protected least significant difference (PLSD) intervals for comparison of means were calculated at the 0.05 level of significance. Mean polymerization-dependent differences in color were ΔE₀₀ = 4.48 (2.11) and ΔE₇₆ = 5.51 (2.68). The ΔTP₀₀ range was 2.57, while the ΔTP₇₆ range was 2.89. Mean polymerization-dependent differences in translucency were ΔTP₀₀ = 0.84 (0.77) and ΔTP₇₆ = 0.87 (0.76). Analysis of variance showed significant differences among composites, shades, and their interactions (P < 0.0001; power = 1.0). Regression equations and r values for the two color-difference formulae and all evaluated TP values showed very strong correlation. In conclusion, within the limitations of this study, polymerization-dependent changes in color and translucency were highly varied. The majority of shades showed polymerization-dependent differences in color higher than the ΔE₇₆ = 3.7. The TP generally increased after light polymerization by light activation. The very strong correlation (r > 0.97) between the two color-difference formulae indicates that the limitations of the CIELAB system do not appear to be a problem when evaluating composites; however, recorded differences between ΔE₇₆ and ΔE₀₀ values stress the importance of data conversion.     

Use of a porcelain color discrimination test to evaluate color difference formulas

STATEMENT OF PROBLEM: Limited studies have indicated that an alternative small color difference formula would be more appropriate for use in dentistry. PURPOSE: The purposes of this study were to determine which color difference formula provides a superior degree of fit for judgments of perceptibility and acceptability and to determine if different groups of evaluators have different levels of perceptibility and acceptability for each color difference formula. MATERIAL AND METHODS: Each observer from 4 groups (4 dentists, 4 dental assistants, 4 technicians, and 4 patients)made independent observations of perceptibility and acceptability judgments on pairs of opaque porcelain (VitaOmega 900) disks (14 mm in diameter by 3 mm thick). Color differences of the pairs were calculated using DeltaE*(ab), DeltaE(CMC)(l:c), and DeltaE(2000) color difference formulas, and the observer judgments were regressed to each color difference in dependently for perceptibility and acceptability. The area under the receiver operator curves was calculated and ranked, and the optimal factor for the CMC (Colour Measurement Committee, Society of Dyers and Colourists, Great Britain) color difference formula was chosen. A repeated measures maximum likelihood ANOVA (alpha=.05) was applied to determine statistical significance of fit among the observer groups, and the various color difference formulas for both perceptibility and acceptability. Tukey-Kramer Adjustment (alpha=.05) was used as a post hoc test. RESULTS: A difference in the degree of fit of the judgments of color differences was found for the 3 formulas (P=.001)and the 2 judgment types (P<.001) studied, with no significant interaction (P=.979). The Tukey-Kramer test identified a lower degree of fit for the DeltaE*(ab) formula compared to DeltaE(CMC)(2:3) and DeltaE(2000) formulas. No significant difference was found in the mean judgment levels among the observer groups (P=.474) studied, nor within any interaction (P>.404). CONCLUSIONS: DeltaE(2000) and DeltaE(CMC)(2:3) color difference formulas provide a better fit to the calculated color differences,therefore providing better indicators of human perceptibility and acceptability of color differences between tooth colors.     

Effects of staining and artificial aging on optical properties of gingiva-colored resin-based restorative materials

Clinical Oral Investigations - To evaluate CIEDE2000/CIELAB differences in color (ΔE00/ΔEab), and translucency parameter (ΔTP00/ΔTPab), and gloss of gingiva-colored resin-based...     

Color and translucency of zirconia infrastructures and porcelain-layered systems

Statement of problem

A good color match combined with a proper translucency match results in excellent esthetics for a metal-free restoration, yet basic color and translucency comparisons between available zirconia systems are not well described.

COLOR IN DENTISTRY: MATCH ME, MATCH ME NOT

This Critical Appraisal focuses on defining color match in dentistry through determination of perceptibility and acceptability visual thresholds. Differences between in vitro and clinical conditions, monochromatic and polychromatic materials, and old and new Commission Internationale de l'Eclairage (International Commission on Illumination; CIE) formulas will be considered. Color difference thresholds can serve as a quality control tool and as guidelines for selection of dental materials and evaluation of their clinical performance.     

Changes in appearance of silicone elastomers for maxillofacial prostheses as a result of aging

PURPOSE: The purpose of this study was to investigate the influence of certain defined variables on color and opacity of silicone elastomers for maxillofacial prostheses. MATERIALS AND METHODS: Three condensation-type and five addition-type silicone elastomers were tested for their changes in color and opacity as a result of aging. The specimens were aged under a xenon light source, dry or wet, and in darkness, also dry (control specimens) or wet. The aging times were 24, 96, 168, 336, 504, 840, 1176, and 1512 hours. The changes in appearance were measured with a spectrophotometer. RESULTS: The condensation-type polymers increased in opacity in an aqueous environment, while the addition-type polymers, as a group, showed the smallest color changes. Although the addition-type polymers generally had a higher filler content than the condensation types, they had a lower opacity. However, because of their higher viscosity, the condensation-type polymers offer better possibilities for intrinsic coloring of the prosthesis. CONCLUSION: Under the experimental conditions studied, significant differences between the silicone elastomers regarding color and opacity changes were demonstrated. However, for a proper choice of material in a given case, these factors have to be related to biologic and mechanical properties of the material.     

Defining a natural tooth color space based on a 3-dimensional shade system

STATEMENT OF PROBLEM: The natural tooth color space reported by a manufacturer may not represent the comprehensive spectrum of natural teeth for all population groups. PURPOSE: The purpose of this study was to define a natural tooth color space within the Greater Buffalo, New York population and to compare that to the color space determined by a manufacturer. MATERIAL AND METHODS: Nine hundred and thirty-three maxillary central incisors (501 patients) were measured with a shade-taking device (Vita Easyshade). For each tooth, L*, a*, b* values, chroma, hue, and the closest shade (Vita 3D-Master) were recorded. A linear regression analysis was performed to determine how well the manufacturer's values predict actual values for L*, a*, and b*. Color differences (DeltaE*) between the Buffalo population and the closest shade were also calculated. A 1-sample t test was used to determine whether the color differences seen in the sample were statistically different from the perceptibility threshold, DeltaE*=3.7 (alpha=.05). RESULTS: All 3 attributes of the Buffalo population displayed a broader range than those from the shade guide. However, the regression analysis revealed a significantly positive relationship between the L*, a*, and b* values of the 2 methods (P<.001). The 1-sample t test revealed a significant DeltaE* (mean DeltaE*=6.15) difference from the perceptibility threshold of DeltaE*=3.7 (P<.001). CONCLUSIONS: Color differences between the Buffalo population and the shade guide were frequently above published perceptibility thresholds, but within the range of acceptability. The Buffalo population tooth color space encompassed the manufacturer's color space.     

Performance of two-flux and four-flux models for predicting the spectral reflectance and transmittance factors of flowable dental resin composites

ObjectiveTo evaluate the prediction accuracy of the Kubelka-Munk Reflectance Theory and other more innovative two-flux and four-flux models for predicting the reflectance and transmittance factors of two flowable dental resin composites of various thicknesses within clinically acceptable color difference.MethodsCylindrical samples of Aura Easy Flow resin composite (Ae1, Ae2, Ae3, Ae4 shades) and Estelite Universal Flow SuperLow resin composite (A1, A2, A3, A3.5, A4, A5 shades) were prepared with thicknesses ranging from 0.3 mm to 1.8 mm. Their reflectance and transmittance factors were measured with a spectrophotometer based on an integrating sphere, and were also predicted by 3 different two-flux models and 2 different four-flux models. The accuracy of reflectance and transmittance factor predictions was assessed using the CIEDE2000 color distance metric and 50:50% acceptability and perceptibility threshold criteria.ResultsEymard’s four-flux model is found to be the most accurate for predicting the spectral reflectance and transmittance factors, with 85% (resp. 100%) of all color deviations below the acceptability threshold, and below the perceptibility threshold for 40% (resp. 57%) of the samples with thickness ranging from 0.3 to 1.8 mm in reflectance (resp. transmittance) mode. The Kubelka-Munk Reflectance Theory is found to be the least accurate model for predicting the spectral reflectance and transmittance factors of dental resin of thickness ranging from 0.3 to 1.8 mm.SignificanceEymard’s four-flux model enables to predict the color of slices of dental materials within acceptable color differences. Eymard’s four-flux model’s optical parameters thus describe light-matter interactions in dental materials more accurately than state of the art Kubelka-Munk Reflectance Theory.     

Color stability of thermochromic pigment in maxillofacial silicone

PURPOSE

Maxillofacial silicone elastomer is usually colored intrinsically with color pigments to match skin colors. The purpose of this study was to investigate the color stability of a maxillofacial silicone elastomer, colored with a thermochromic, color changing pigment.

MATERIALS AND METHODS

Disc-shaped maxillofacial silicone specimens were prepared and divided into 3 groups: a conventionally colored control group, one group additionally colored with 0.2 wt% thermochromic pigment , and one group with 0.6 wt% thermochromic pigment. Half of the surface of each specimen was covered with an aluminium foil. All of the specimens were exposed to UV radiation in 6 hour cycles over 46 days. In between the UV exposures, half of the specimens were stored in darkness, at room temperature, and the other half was stored in an incubator, at a humidity of 97% and a temperature of +37℃. Color measurements were made with a spectrophotometer and registered according to the CIELAB L^*a^*b^* color model system. The changes in L^*, a^* and b^* values during artificial aging were statistically analyzed by using paired samples t-test and repeated measures ANOVA. P-values <.05 were considered as statistically significant.

RESULTS

The UV exposure resulted in visually noticeable and statistically significant color changes in the L^*, a^* and b^* values in both of the test groups containing thermochromic pigment. Storage in the incubator lead to statistically significant color changes in the a^* and b^* values of the specimens containing thermochromic pigment, compared to those stored at room temperature.

CONCLUSION

The specimens containing thermochromic pigment were very sensitive to UV radiation, and the thermochromic pigment is not suitable, as such, to be used in maxillofacial prostheses.     

Color stability of maxillofacial prosthetic silicone functionalized with oxide nanocoating

Statement of problem

Maxillofacial prostheses made of silicone elastomers undergo undesirable color degradation over time. How this color change can be prevented is unclear.

Effect of Extraoral Aging Conditions on Color Stability of Maxillofacial Silicone Elastomer

Purpose: Maxillofacial prostheses require enhancement or replacement due to deterioration in their color during service. The purpose of this study was to investigate color stability of pigmented and nonpigmented maxillofacial silicone elastomer exposed to different human and environmental aging conditions. Material and Methods: One hundred and twelve disk‐shaped silicone (TechSil S25, Technovent, Leeds, UK) specimens were prepared and equally divided into pigmented (using intrinsic rose‐pink skin shade, P409, Principality Medical, Newport, UK) and nonpigmented categories of seven groups (n = 16; 8 pigmented and 8 nonpigmented): dark storage (control) (group 1), sebum solution storage (group 2), acidic perspiration storage (group 3), light aging (group 4), natural outdoor weathering (group 5), silicone‐cleaning solution (group 6), and mixed conditioning of sebum storage and light aging (group 7). Conditioning periods (groups) were 6 months (groups 1, 2, 3, 5), 360 hours (groups 4, 7), and 30 hours (group 6). Color change (ΔE) was measured at the start and end of conditioning. In addition, for groups 1, 2, and 4, ΔE was measured at fixed intervals of 30 days, 15 days, and 30 hours, respectively. Data were analyzed with one‐way analysis of variance (ANOVA), Dunnett’s‐T3 post hoc, and independent t‐tests (p < 0.05). Linear regression was implemented to investigate ΔE with time for groups 1, 2, and 4. Results: Six of the seven treatment conditions induced perceivable color change (ΔE > 3). Within the nonpigmented category, specimens stored in the dark for 6 months (group 1) exhibited high ΔE (6.17), which was greater (p < 0.05) than that produced by silicone‐cleaning solution for 30 hours (group 6) (ΔE = 2.08). Within the pigmented category, light aging (group 4), outdoor (group 5), and mixed (group 7) conditionings induced greatest color changes (ΔE = 8.26, 8.30, 9.89, respectively) (p < 0.05); however, there was a strong positive linear function of log‐time after dark storage (group 1) and light aging (group 4). Conclusions: There is inherent color instability of nonpigmented silicone elastomer, which adds to the overall color change of silicone prostheses. Storing silicone elastomer in simulated sebum under light aging induced the greatest color changes. Overall, the color stability of TechSil S25 maxillofacial heat‐temperature‐vulcanizing (HTV) silicone elastomer was unacceptable (ΔE > 3.0, range from 3.48 to 9.89 for pigmented and 3.89 to 10.78 for nonpigmented) when subjected to six of the seven extraoral aging conditionings used in this study. Inherent color instability of nonpigmented facial silicone elastomers primarily contributes to the color degradation of extraoral facial prostheses. Sebaceous skin secretions along with daylight radiation cause the greatest perceivable color change to the silicone and pigment used in this study.     

Interfacial corrections of maxillofacial elastomers for Kubelka–Munk theory using non-contact measurements

ObjectiveReflectance measurements using a 45°/0° non-contact measuring system provide accurate data for translucent materials, yet the interfacial reflection corrections (IRCs) for Kubelka–Munk theory have not been evaluated using this system. The objective is to determine which IRC method for Kubelka–Munk theory (K-MT) models the spectral reflectance of pigmented maxillofacial elastomer (MFE) with least error.MethodSamples at varying thicknesses of each of 19 shades of skin-colored maxillofacial elastomer were measured using this system on each of three backings. Reflectance values within the visible wavelength range for each shade were fit by non-linear regression to K-MT using different IRC methods: no IRC correction (No), IRC for opaque materials (Op) and IRC for translucent materials (Tr). Errors associated with each method were analyzed using repeated-measures ANOVA and a Bonferroni-corrected t-test.ResultsAverage error mean square values over all wavelengths were 0.00038 for K-MT with no IRC, 0.00023 with Op IRC, and 0.00015 with Tr IRC. The No method gave a statistically higher error than either the Op or Tr method at all analyzed wavelengths, and the Tr gave a lower error than the OP at all analyzed wavelengths between 450 and 600 nm. The predicted CIELAB values of all the shades tested fell into the range of human skin color space.SignificanceCorrected Kubelka–Munk theory with the IRC for translucent materials proposed by Richmond provides higher accuracy on maxillofacial elastomer over the more important visible wavelengths. Color and translucency of maxillofacial elastomer can be predicted using corrected K-M theory.