Printing and mounting digital casts in the centric relation position for use on an analog articulator: A dental technique.

A technique for recording, printing, and mounting digital casts in centric relation is described. Combining elements of analog and digital workflows, centric relation records can be transferred by digital scanning and used to align casts for articulation. This method is useful to the clinician adapting to digital workflow or preferring a physical semiadjustable articulator in conjunction with digital scans.

Proposed shade guide for human facial skin and lip: a pilot study.

STATEMENT OF PROBLEM: Currently, no commercially available facial shade guide exists in the United States for the fabrication of facial prostheses. PURPOSE: The purpose of this study was to measure facial skin and lip color in a human population sample stratified by age, gender, and race. Clustering analysis was used to determine optimal color coordinates for a proposed facial shade guide. MATERIAL AND METHODS: Participants (n=119) were recruited from 4 racial/ethnic groups, 5 age groups, and both genders. Reflectance measurements of participants' noses and lower lips were made by using a spectroradiometer and xenon arc lamp with a 45/0 optical configuration. Repeated measures ANOVA (α=.05), to identify skin and lip color differences, resulting from race, age, gender, and location, and a hierarchical clustering analysis, to identify clusters of skin colors) were used. RESULTS: Significant contributors to L*a*b* facial color were race and facial location (P<.01). b* affected all factors (P<.05). Age affected only b* (P<.001), while gender affected only L* (P<.05) and b* (P<.05). Analyses identified 5 clusters of skin color. CONCLUSIONS: The study showed that skin color caused by age and gender primarily occurred within the yellow-blue axis. A significant lightness difference between gender groups was also found. Clustering analysis identified 5 distinct skin shade tabs.

Incisal translucency of vital natural unrestored teeth: a clinical study.

INTRODUCTION: Understanding the distribution of incisal translucency will provide clinicians a guide to use this knowledge to improve the esthetic replication of anterior restorations. The aim of this study is to investigate the distribution of incisal translucency of unrestored vital natural maxillary central, lateral, and canine vital teeth from a stratified population in different age, gender, and race. MATERIALS AND METHODS: A total of 120 subjects were recruited for this study. Six subjects with equal gender balance from four racial/ethnic groups (White, Black, Asian, and others) were recruited from each of the following age groups: 18 to 29 years, 30 to 39 years, 40 to 49 years, 50 to 59 years, and 60 to 85 years. Potential subjects were clinically screened to determine if three specific anterior teeth (maxillary central incisor, lateral incisor, and canine) were non-restored, natural permanent teeth free from external staining or bleaching. A digital imaging and shade analysis device was used to measure tooth translucency. RESULTS: Statistically significant interaction (p < 0.001) was found for the groups. The interaction between race and gender was not statistically significant (p = 0.485). However, the interaction between race and age (p = 0.03), age and gender (p = 0.015), and among age, race, and gender (p < 0.001) was found statistically significant according to the analysis of variance test results. The interaction between race and gender was not statistically significant (p = 0.485).

Coverage error of gingival shade guide systems in measuring color of attached anterior gingiva.

STATEMENT OF PROBLEM: It remains unclear which gingival shade guide is most effective in producing the best visual shade match. PURPOSE: The purpose of this study was to determine and compare the coverage errors (CEs) of 2 different gingival shade guides and their combination in a selected population. MATERIAL AND METHODS: The CEs of the following gingival shade guides were evaluated: (1) Lucitone 199, (2) IPS Gingiva, and (3) a combination of the 2 shade guide systems. The spectral reflectance values of the center of each gingival shade tab (1.5 mm in diameter) were measured (without a backing) with a spectroradiometer and an external light source at wavelengths from 380 nm to 780 nm at 2-nm intervals. All spectral reflectance measurements were made using 0-degree observer and 45-degree illumination and then converted to CIE values. The attached gingiva of 120 subjects was measured with the same protocol. The CEs of each of the 120 subjects' attached gingiva for each of the 2 shade guide systems and their combination were determined and averaged. The mean minimum CEs were analyzed with repeated measures ANOVA and the post hoc Tukey HSD for multiple comparison (alpha=.05). RESULTS: A significant difference (P<.001) was found among the mean minimum CEs of the 2 gingival shade guide systems and their combination. The Tukey HSD test revealed that the mean minimum CEs for Lucitone 199 (Delta E 10.8 +/-4.4) were significantly different from the IPS Gingiva (Delta E 8.6 +/-3.6) shade guide system. However, the combination of the 2 gingival shade guide systems (Delta E 7.9 +/-3.4) was not significantly different from the IPS Gingiva system, but a significant difference was found among races (P=.016). No interactions were found between the other tested groups. The mean CE for white individuals (Delta E 8.3 +/-2.5) is significantly different and less than the mean CE for African Americans (Delta E 10.0 +/-4.4). The CEs for Asians (Delta E=9.1 +/-4.3) and others (Delta E 9.0 +/-4.4) are not significantly different from CEs for whites or African Americans. CONCLUSIONS: The IPS Gingiva shade guide system resulted in the lowest CEs compared to the Lucitone 199 shade guide system. The mean CE for Lucitone 199 was significantly greater than the mean CE for IPS Gingiva and for the combination of the 2 guides. The mean CE for whites is significantly different and less than the mean CE for African Americans. The CEs for Asians and others are not significantly different from CEs for whites or African Americans.

Estimating the color of maxillary central incisors based on age and gender.

STATEMENT OF PROBLEM: There is no scientific information regarding the selection of the color of teeth for edentulous patients. PURPOSE: The purpose of this study was to evaluate linear regression models that may be used to predict color parameters for central incisors of edentulous patients based on some characteristics of dentate subjects. MATERIAL AND METHODS: A spectroradiometer and an external light source were set in a noncontacting 45/0 degree (45-degree illumination and 0-degree observer) optical configuration to measure the color of subjects' vital craniofacial structures (maxillary central incisor, attached gingiva, and facial skin). The subjects (n=120) were stratified into 5 age groups with 4 racial groups and balanced for gender. Linear first-order regression was used to determine the significant factors (alpha=.05) in the prediction model for each color direction of the color of the maxillary central incisor. Age, gender, and color of the other craniofacial structures were studied as potential predictors. Final predictions in each color direction were based only on the statistically significant factors, and then the color differences between observed and predicted CIELAB values for the central incisors were calculated and summarized. RESULTS: The statistically significant predictors of age and gender accounted for 36% of the total variability in L*. The statistically significant predictor of age accounted for 16% of the total variability in a*. The statistically significant predictors of age and gender accounted for 21% of the variability in b*. The mean Delta (SD) between predicted and observed CIELAB values for the central incisor was 5.8 (3.2). CONCLUSIONS: Age and gender were found to be statistically significant determinants in predicting the natural color of central incisors. Although the precision of these predictions was less than the median color difference found for all pairs of teeth studied, and may be considered an acceptable precision, further study is needed to reduce this precision to the limit of detection.

Measurement of color for craniofacial structures using a 45/0-degree optical configuration.

STATEMENT OF PROBLEM: The color of vital craniofacial structures has not been measured accurately. PURPOSE: The purpose of this study was to determine the color of vital craniofacial structures and evaluate the validity and test-retest reliability of a noncontacting 45/0-degree optical configuration. MATERIAL AND METHODS: A spectroradiometer and an external light source were configured in a noncontacting 45/0-degree (45-degree illumination and 0-degree observer) optical configuration to measure the color of subjects' vital craniofacial structures (central and lateral incisor and canine, attached gingiva, lips, and facial skin). The 120 subjects were stratified into 5 age groups with 4 racial categories and balanced for gender. For evaluation of validity, linear regressions and 95% confidence intervals were calculated for DeltaL( *), Deltaa( *), Deltab( *) [color difference of (CIE) LAB values] between the measured and certified values of the 22 color patches of the DC Color Checker. For test-retest reliability, a random sample of 12 (10%) subjects was remeasured at a second visit. Paired t tests, correlations, and Bland-Altman analyses were performed between the first and second measurements of the 12 pairs of L( *), a( *), and b( *) values for the 6 craniofacial structures. RESULTS: For validity, the mean color difference and linear regression for Commission Internationale d'Eclairage (CIE) LAB values between measured and certified color of the 22 opaque color patches were DeltaE of 1.46 and 0.99 for all regressions, respectively. Only Deltaa( *) did not contain zero in its 95% confidence interval. For test-retest reliability, no paired t tests were significantly different from each other, and the Pearson correlation coefficient ranged from 0.9 (9 pairs) to 0.7 (3 pairs). Ten of the 18 Bland-Altman plots showed good reliability. CONCLUSION: The spectral reflectance of craniofacial structures can be measured with acceptable validity and test-retest reliability using a noncontacting 45/0-degree optical configuration.