Tooth Shade-Matching Ability Between Groups of Students with Different Color Knowledge

PURPOSE

The aim of this study was to evaluate the effect of gender and knowledge of color in dentistry on the visual shade-matching ability of dental students with no experience in shade matching and without identification skills.

MATERIALS AND METHODS

A total of 32 color-normal participants, 16 female (F) and 16 male (M), completed all phases of the experiment. The control group did not listen to a 60-minute lecture (FNL = females that did not listen; MNL = males that did not listen); the other group listened to a lecture about color in dentistry (FL = females that listened; ML= males that listened). The Toothguide Training Box (TTB) (VITA Zahnfabrik) was used. The final exam consisted of a total of 15 lightness-chroma-hue tasks. The correct selection of lightness (L*), chroma (C*), and hue (h*) was observed, as was the computed shade-matching score, ΣΔE*ab, for each participant. Mann-Whitney U test was used for statistical analysis of the data (α = .05) (SPSS 22.0 for Windows [IBM]).

RESULTS

Gender was found to play an important role in shade matching. The FL group selected L* better (L* = 12.11) in comparison with the MNL group (L* = 11.00), which is not significantly different (P = .19). The FL group selected L* better in comparison with the ML group (L* = 10.57), which is not significantly different (P = .10). The FNL group selected C* statistically significantly better (C* = 9.86) than did the ML group (C* = 8.57) (P = .016). The shade-matching score, ΣΔE*ab, for group FL (ΣΔE*ab = 22.50) and group ML (ΣΔE*ab = 31.79) was marginally statistically significant (P = .06).

CONCLUSION

A 60-minute lecture from the field of color in dentistry has a minimal impact on tooth-shade matching, whereas gender plays an important role.

Learning Shade Differentiation Using Toothguide Trainer and Toothguide Training Box: A Longitudinal Study with Dental Students

The positive training effect achieved with the Toothguide Training Box (TTB) has been demonstrated in previous studies. The aim of this study was to investigate the training effect with the TTB at six and 12 months using standardized color tests. The study involved 101 dental students. The participants were divided into two study groups and one control group. Ten standard color samples were determined under uniform environmental conditions with VITA 3D-Master. The control group (N=30) took the color test after one week. Study group 1 (N=49) took the color test after six months and study group 2 (N=22) at 12 months for the first time by following the TTB curriculum. The control group achieved an average ΔEt1=0.85. In study group 1, the ΔEt2 was 2.29, and in study group 2, ΔEt3=2.25. The results after six and 12 months were highly significant compared to the control group (α=0.001). Dependence was determined only with regard to gender. In this study, the TTB quickly led to an improvement in tooth color differentiation among students. After six months, there was a decrease in the training effect. These results suggest that the TTB curriculum should be provided at the end of preclinical training.

Influence of personality on tooth shade selection

PURPOSE

The harmonious shade matching of restorations with adjacent natural teeth is a prerequisite for a successful esthetic restoration. Color is a combined effect of the physical properties of an object, the light source, and the perception of the observer. The interpretation of color is influenced by both the physiological and psychological health of an individual. It is critical to understand the influence of an individual's psychological state on the shade selection procedure to achieve better shade matching and post-treatment patient counseling. The aim of this study was to evaluate the influence of personality on tooth shade selection capability.

MATERIALS AND METHODS

Two porcelain fused to metal (PFM) discs were fabricated. A reference shade was determined using a spectrophotometer (Vita Easyshade, Vita). The personalities of volunteers were identified using a Myers- Briggs Type Indicator (MBTI) questionnaire. The volunteers visually identified the shade of the two PFM discs under a controlled light source. The mean color difference was determined between the visual and the spectrophotometer values. The data thus obtained was statistically analyzed with Kruskal-Wallis and post-hoc comparison tests to ascertain the difference between the groups.

RESULTS

The groups that performed better in tooth shade selection were ENTJ (2.923 ± 2.36), ISTJ (3.086 ± 2.56), ENFJ (3.197 ± 2.936), and ESTJ (3.431± 2.78). The groups INTP (9.383 ± 3.30), ISTP (9.133 ± 3.44), ISFP (8.737 ± 2.81), and INTJ (8.480 ± 3.35) showed poor tooth shade selection ability. The Kruskal- Wallis test showed lower mean rank for group ENTJ (89.75), followed by ISTJ (92.25), and ENFJ (94.80).

CONCLUSION

Within the limitations of this study, it was concluded that there was a statistically significant difference between the different personalities with regard to tooth shade selection ability.

Evaluation of reliability and validity of three dental color-matching devices

PURPOSE

To assess the repeatability and accuracy of three dental color-matching devices under standardized and freehand measurement conditions.

MATERIALS AND METHODS

Two shade guides (Vita Classical A1-D4, Vita; and Vita Toothguide 3D-Master, Vita), and three color-matching devices (Easyshade, Vita; SpectroShade, MHT Optic Research; and ShadeVision, X-Rite) were used. Five shade tabs were selected from the Vita Classical A1-D4 (A2, A3.5, B1, C4, D3), and five from the Vita Toothguide 3D-Master (1M1, 2R1.5, 3M2, 4L2.5, 5M3) shade guides. Each shade tab was recorded 15 continuous, repeated times with each device under two different measurement conditions (standardized, and freehand). Both qualitative (color shade) and quantitative (L, a, and b) color characteristics were recorded. The color difference (ΔE) of each recorded value with the known values of the shade tab was calculated. The repeatability of each device was evaluated by the coefficient of variance. The accuracy of each device was determined by comparing the recorded values with the known values of the reference shade tab (one sample t test; α = 0.05). The agreement between the recorded shade and the reference shade tab was calculated. The influence of the parameters (devices and conditions) on the parameter ΔE was investigated (two-way ANOVA). Comparison of the devices was performed with Bonferroni pairwise post-hoc analysis.

RESULTS

Under standardized conditions, repeatability of all three devices was very good, except for ShadeVision with Vita Classical A1-D4. Accuracy ranged from good to fair, depending on the device and the shade guide. Under freehand conditions, repeatability and accuracy for Easyshade and ShadeVision were negatively influenced, but not for SpectroShade, regardless of the shade guide.

CONCLUSION

Based on the total of the color parameters assessed per device, SpectroShade was the most reliable of the three color-matching devices studied.

[Evaluation of the professional dentists' ability to determine the tooth shade guide: a pilot study]

BACKGROUND

During its clinical practice, the dentist is often faced with issues concerning the determination of teeth shade. This step is considered sensitive by numerous clinicians and dental laboratories. The objective of this study was to test the ability of professional dentists to visually determine the teeth color.

MATERIAL AND METHODS

Eleven dentists classified 35 unmarked samples according to their hue, chroma and value from 2 standardized tooth shade guides Ivoclar-Vivadent (Chromascop) et Vita (3D Master). The ratio between the number of matching samples and the total amount of samples from each group was calculated and converted to a score between 0 and 10.

RESULTS

Better scores were obtained for value and chroma with the 3D Master shade guide than with the Chromascop shade guide (p < 0.001). The opposite result was obtained for the hue (p < 0.05). Globally, better results were obtained for the value and chroma, the hue being the most difficult item to evaluate. A satisfying "color perception" was observed in 69% of the cases.

CONCLUSION

The results of this study argue in favor of a specific training for tooth shade determination in Odontology.

Stratification in anterior teeth using one dentine shade and a predefined thickness of enamel: a new concept in composite layering--Part II

While restoring an anterior tooth, shade matching is one of the crucial points that we can face to have an esthetic final outcome. After studying the physical and optical characteristics of enamel and dentine in the first part of this article, the second part will propose a new method for color matching and a clinical stratification using a simple and reproducible procedure for anterior restorations with only one dentine and one enamel shade.

Shade determination using camouflaged visual shade guides and an electronic spectrophotometer

The aim of the present study was to compare a camouflaged visual shade guide to a spectrophotometer designed for restorative dentistry. Two operators performed analyses of 66 subjects. One central upper incisor was measured four times by each operator; twice with a camouflaged visual shade guide and twice with a spectrophotometer Both methods had acceptable repeatability rates, but the electronic shade determination showed higher repeatability. In general, the electronically determined shades were darker than the visually determined shades. The use of a camouflaged visual shade guide seems to be an adequate method to reduce operator bias.

Composite shade guides and color matching

Finding reliable systems that can help the clinician match the color of direct composite restorations is often an issue. After reviewing several composite shade guides available on the market and outlining their main characteristics and limits (unrealistic specimen thickness, not made with the same material the clinician will use, only a few allow to overlap enamel tabs on dentin ones), the authors evaluated the reliability of a system designed to produce self-made standardized "tooth-shaped" shade guide specimens. Small changes in composite enamel thickness may determine huge differences in esthetic outcomes. In conclusion, the results showed that all the specimens demonstrated comparable enamel thickness in all the examined areas (cervical, middle, incisal).

Influence of ceramic color and translucency on shade match of CAD/CAM porcelain veneers

OBJECTIVE

To investigate the influence of translucency of CAD/CAM ceramic milling blocks on the final color of porcelain veneer cemented using resin cement with two different opacities.

MATERIALS AND METHODS

A standardized incisal lap preparation was made on a maxillary right central incisor that was duplicated using composite resin material (Z250, A4, 3M ESPE). The resin dies were individually laser scanned (Bluecam, Sirona) in order to build a 3D model of the porcelain veneer on the CAD software (Cerec 3D). Three types of milling blocks were used to fabricate the required restorations: multichromatic, high translucency, and low translucency milling blocks (IPS Empress CAD, A1 Vita shade tab). The milled veneers were polished, glazed, and bonded on the resin dies using high opacity and low opacity resin cements (Panavia F2.0). A digital shade guide device (Easyshade Advance, Vita) was used to measure color parameters (CIE Lab values) at the incisal, middle, and cervical third of each cemented restoration. ΔE values of the cemented veneers were calculated against the target color (A1).

RESULTS

Cementation of porcelain veneers resulted in significant color change of the resin die (A4) as ΔE values ranged between 8.9 and 13.7. However, the type of milling block did not have an observable effect on final color as the measured ΔE values, against original die color, were very close for the multichromatic block (ΔE = 10.7 ± 0.1), high translucency (ΔE = 9.7 ± 0.09), and low translucency blocks (ΔE = 13.4 ± 0.11). The opacity of the used resin cement did not affect the final shade match, as the observed ΔE values using either high opacity and low opacity resin cement were less than 2 for the three used ceramic blocks. The greatest color difference was observed between the incisal third of multichromatic veneers (ΔE = 8.9) and the cervical third of low translucency veneers (ΔE = 13.7), while for the rest of the test groups this shift was not clinically observable (ΔE < 2.5).

CONCLUSION

Within the limitations of this study, the shade match of CAD/CAM porcelain veneers was not influenced by the translucency of used milling block or the opacity of the resin cement.

Shade matching performance of dental students with three various lighting conditions

AIM

To evaluate the ability of dental students to match shades under three various light conditions.

MATERIALS AND METHODS

Sixty senior dental students participated in this study. All students were tested for color deficiency using Ishahara's tests. Nine classical vita shade tabs were randomly selected and their identification codes were concealed. The students were asked to match these 9 selected items by using a complete vita shade guide under three various light conditions (natural light, clinical light, and correcting light source). The chosen shade tabs were recorded and the correct matches were counted. Scores were calculated by adding the number of correct matches.

RESULTS

The mean values of correct match scores with natural light, clinical light and correcting light source were 4.82, 4.75 and 6.82, respectively. There was no significant difference in correct matches scores between men and women, nor among various vita A, B, C and D shades.

CONCLUSION

The students showed a better performance in shade matching under the correcting light source than natural light and clinical light. Gender had no effect on shade matching selection and there was no difference in shade matching ability among vita A, B, C, D shades.

CLINICAL SIGNIFICANCE

Shade matching performance is significantly improved with correcting light source.

An audit of shade reproduction of fixed metal ceramic prostheses

This investigation aimed to evaluate the colour difference between metal ceramic restorations and their corresponding shades and any reasons for a colour mismatch in the dental laboratory. The colour of 50 consecutive metal ceramic restorations produced in a laboratory was measured using a spectrophotometer and compared to the shade tabs. Colour reproduction was optimal at porcelain thicknesses between 1.4-1.6 mm, varied between technicians within the same laboratory and was better for shades in the 2M group. Most crowns were above the threshold for a clinically acceptable shade match and almost all crowns were lighter than the corresponding shade tab.

Toothguide Training Box for dental color choice training

The purpose of this study was to evaluate the use of the Toothguide Training Box (TTB) for training dental students in color identification. The seventy-four volunteers who took part in the study attended a seminar on the Vita 3D Master Guide (MG) and the TTB system as well as a demonstration of the equipment before training began. At the end of the training they took the TTB final test. In addition, the participants were asked to recognize ten MG shade tabs in a blind manner before and after TTB training. The training times and percentages of correct answers were compared using the paired t-test. Variations in scores with training times and percentages of correct answers before and after training were compared using the ANOVA test. Training times between thirty-one and thirty-eight minutes provided a significantly higher mean score than training times of over thirty-eight minutes (p=0.036). The percentage of correct answers obtained with the MG before and after training shows a positive correlation. High TTB scores are associated with a greater number of correct answers in MG shade tab selection.

[In vivo model to evaluate the accuracy of complete-tooth spectrophotometer for dental clinics]

OBJECTIVE

To test ΔE between measured value and right value from the Crystaleye complete-tooth spectrophotometer, and to evaluate the accuracy rate of the spectrophotometer.

METHODS

Twenty prosthodontists participated in the study. Each of them used Vita 3D-Master shadeguide to do the shade matching, and used Crystaleye complete-tooth spectrophotometer (before and after the test training) tested the middle of eight fixed tabs from shadeguide in the dark box. The results of shade matching and spectrophotometer were recorded. The accuracy rate of shade matching and the spectrophotometer before and after training were calculated.

RESULTS

The average accuracy rate of shade matching was 49%. The average accuracy rate of the spectrophotometer before and after training was 83% and 99%.

CONCLUSIONS

The accuracy of the spectrophotometer was significant higher than that in shade matching, and training can improve the accuracy rate.

Allocation of color space for different age groups using three-dimensional shade guide systems

PURPOSE

To determine the color space and the coverage error of two manual shade guide systems in four age groups of a selected population.

MATERIAL AND METHODS

A total of 174 patients were divided into four age groups and the shade of their natural teeth was measured (2067 teeth) with a spectrophotometer (Vita Easyshade). Color parameters in terms of L*, a*, b* values, chroma, and hue were recorded for each tooth. Color difference (ΔE*min) between each natural tooth and the closest match using two manual shade guide systems were calculated (3D Master shade guide standard and 3D Master shade guide with intermediate values). A Wilcoxon test was used to assess statistical differences between mean ΔE*min values for each system (α = 0.05).

RESULTS

The recoded ΔE of the two tested manual systems was 6.19 for 3D Master shade guide (standard) and 6.02 for 3D Master shade guide (intermediate values). A statistically significant difference (P < 0.001) was found between the mean ΔE*min of the two systems. 47% of natural teeth presented a best match with intermediate value and chroma shade tabs. The mean ΔE*min was influenced by the age group of the patients (5.15, 5.23, 6.58, and 6.69, respectively).

CONCLUSION

Using intermediate value and chroma did not improve shade match, nor the coverage error of the tested population. Nevertheless, better coverage error was observed in younger age groups compared to older anterior teeth.

Assessment of color fidelity of several composite resins compared to their Vita Classical shade registration

This study compared the color fidelity of different composite resins with their registration in the Vita Classical Shade Guide. Using a prefabricated Teflon mold, 120 specimens were divided into four groups (n = 30), according to the resin tested. Three subgroups (n = 10) were prepared for each resin group; these subgroups tested enamel shade, dentin shade, and enamel and dentin shade. Three measurements were performed to verify whether the tooth shade matched that of the Vita Classical Shade Guide. The color was evaluated and the shade variations were calculated. The data were submitted to a three-way ANOVA test (time, color match, and composite type), followed by Tukey's test. It was concluded that all composite resins showed color differences in relation to the Vita Classical Shade Guide.

An assessment of shade taking by dental undergraduates

This study investigated the shade recording abilities of dental students using the traditional methods and that incorporating a colour correcting device to that of a digital shade recording device. Shade matching ability was evaluated between different groups of students at Malmö and Cardiff. The use of the colour correcting device improved a student's ability to match shades when compared to the traditional method under normal lighting conditions. There was no gender difference to match shade amongst the participants. We observed that at one of the test sites the ability to take the correct shade improved as clinical experience was gained.

The parallel stratification masking technique: an analytical approach to predictably mask discolored dental substrate

Discolored dental substrates continue to challenge the restorative team when ultraconservative treatment modalities are chosen. An innovative laboratory concept--the parallel stratification masking technique--has been developed in order to achieve maximum preservation of dental hard tissues and predictably accomplish a desirable esthetic outcome. The major advantages of this technique are that the ceramist is able to: a)identify and map the discolored dental substrate, b)predictably mask the discolored dental substrate, and c) assess the appropriate masking efficacy of the fabricated restoration prior to laboratory delivery to the dentist in cases of bonded porcelain restorations.

Difference in illuminant-dependent color changes of shade guide tabs by the shade designation relative to three illuminants

PURPOSE

To determine the difference in illuminant-dependent color changes of shade guide tabs of Vita Lumin (VITA), Chromascop (CHRO) and Vita 3D-Master (3D-M) shade guides by the shade designation in each shade guide.

METHODS

Color of 16 tabs of VITA, 20 tabs of CHRO and 29 tabs of 3D-M was measured according to the CIELAB color scale relative to the CIE standard illuminant D65, A and F2. Color differences (deltaE*ab) between the A1 tab and other VITA tabs, between the 110 tab and other CHRO tabs and between the 0M1 tab and other 3D-M tabs relative to the three illuminants were calculated, and the ratios of deltaE*ab values relative to the different illuminants [deltaE*ab(A)/deltaE*ab(D65), deltaE*ab(F2)/deltaE*ab(D65) and deltaE*ab(F2)/deltaE*ab(A)] were calculated. Ratios of the hue angle shifts of each shade tab by the change of illuminant over the corresponding value of the Al, the 110 or the 0M1 tab were also calculated. Differences in the ratios of color difference and hue angle shift were analyzed with a repeated measures, two-way analysis of variance (alpha = 0.05).

RESULTS

Ratios of deltaE*ab values by the illuminant were 0.90-1.17, 0.95-1.07 and 0.99-1.06 for the VITA, the CHRO and the 3D-M shade guide, respectively. Ratios of the hue angle shifts by the illuminant were from -1.6 to 1.8 for the VITA, from -7.3 to 1.2 for the CHRO and from -1.2 to 3.1 for the 3D-M. Changes in color and hue angle of shade tabs were significantly different by the shade tab designation when illuminant was changed (P < 0.01).

Estimation of visual shade matching errors with 2 shade guides

OBJECTIVE

To compare the interobserver difference in visual shade matching and estimate the precision of color discrimination.

METHOD AND MATERIALS

Visual shade matching of a maxillary central incisor of 33 subjects was performed by 2 prosthodontists independently in a chair under ceiling daylight-corrected fluorescent lighting, using the Vitapan Classical and the Vitapan 3D Master shade guides (Vita Zahnfabrik). The 3 closest shade tabs were selected and ranked in order of best, second best, and third best matches. Interobserver agreement was found by comparing the best shade and the common shade for each subject by the 2 clinicians. The CIE Lab color difference, DeltaE*, between the best shade and the common shade selected by the clinicians was calculated for each subject. A t test (alpha = .05) was performed to find clinician differences of the means of the best shade and the common shade for both shade guides.

RESULTS

Interobserver agreement was 30% when matching the best shade; however, the ratio increased to over 85% for the common shade (a significant difference at the .05 level). No significant differences were found between the 2 shade guides by means of the mean color differences between the best shade match and the common shade match, while the Vitapan 3D Master shade guide was superior to the Vitapan Classical shade guide in reducing the interobserver color differences from 0.8 to 0.2.

CONCLUSION

Visual shade matching of teeth gave better agreement using the Vitapan 3D Master shade guide when selecting the common shade from among the closest 3 shades chosen by multiple observers.

A comparison between conventional visual and spectrophotometric methods for shade selection

OBJECTIVE

Inconsistencies among dentists in matching natural tooth shades have been documented. This study examined the reliability of a spectrophotometer in shade selection compared to visual method.

METHOD AND MATERIALS

Nine observers with normal color vision were asked to visually and digitally match shades of nine maxillary models with incisors being replaced by Vita Classical shade guide tabs. The same test was carried out in vivo on nine subjects' maxillary central incisors. Observers included prosthodontists, dental technicians, and postgraduate students.

RESULTS

No significant difference was found among observers in shade selection regardless of the selection method. However, there was a significant difference between digital and visual methods in shade selection. Digital method was five times more likely to match the original shade color compared to visual method.

CONCLUSION

The system does not solve all problems involved in the determination of a tooth shade. Vita Easyshade spectrophotometer was more likely to match the shade compared to visual method. Nevertheless, this system needs further refinement, as well as software upgrades. Shade-matching devices could help clinicians and technicians achieve a better shade choice. The combination of visual shade analysis and digital shade measurement together lies in the precise predictability of the miscibility of shades.

Repeatability of a dental shade-matching instrument when compared to traditional visual methods of shade evaluation

Electronic shade-matching instruments are available for clinical use; however, their accuracy has not been established. This study evaluated a new electronic method of clinical shade matching compared to the standard visual method. The Vita Easyshade system, an electronic method of shade matching, was used on 40 subjects to measure the central region of each patient's maxillary left central incisor (tooth No. 9). Two visual evaluators with predetermined visual shade matching abilities selected a shade from the same area of tooth No. 9 for all subjects. Student's t-test, using a 95% score confidence interval (CI), was used to compare the two methods. The Vita Easyshade system was accurate 85% of the time in this in vivo study; however, the instrument was predictably accurate only 68-91% of the time at the 95% CI.

Excellence in photography: heightening dentist-ceramist communication

The goal of the dentist is to share accurate color and other tooth characteristics about the tooth being matched. The doctor must also communicate what preparation (stump) shades the ceramist is tasked with covering since this may influence the final outer porcelain color, depending on the restorative material selected. The higher the quality of the data that we share with our dental technicians, the greater chance they have to provide us with a final restoration that matches what we and the patient sees. Dental technicians are at a great disadvantage since they are usually not able to actually see the patient. Therefore, quality digital photo images can fill that important missing link. Precise digital images can be a tremendous asset for most dental offices and they provide a mechanism for heightened communication with the ceramist and the dental laboratory team--one of the keys to aesthetic restorative success.

Shade distribution of commercial resin composites and color difference with shade guide tabs

PURPOSE

To determine the shade distribution of varied shades of contemporary resin composites, and to measure the color difference (deltaE*ab) between individual shades of resin composites and the nearest shade tabs, which showed the smallest color difference with each shade of resin composite, in the VITA shade guide.

METHODS

Eight light-curing resin composites, with a total of 41 shades, were studied. Color of specimens was measured on a reflection spectrophotometer over a white background. Ranges and distributions of CIE L*, C*ab, a* and b* values of each brand of resin composites were determined. Color difference between each shade of resin composites and each shade of the shade guide tabs were calculated, and the nearest shade guide tab was selected.

RESULTS

The range of CIE L* value for eight brands of resin composites was 3.2-9.0, that of C*ab was 2.5-11.6, that of CIE a* value was 1.1-5.8, and that of CIE b* value was 5.9-11.5. Color differences (deltaE*ab) between each shade of resin composites and the nearest shade tab of the shade guide was 0.9-12.8.

Optimization of tooth color and shade guide design

PURPOSE

One critical prerequisite for dental shade guides is to match the color range and distribution of human teeth. The purpose of this study was to design computer models for dental shade guides and compare them with an existing shade guide. A targeted coverage error for a newly developed shade guide was DeltaE(ab) < 2 with a corresponding CIE2000 value.

MATERIALS AND METHODS

A total of 1064 teeth were evaluated in vivo using an intra-oral spectrophotometer. Shade guide models were designed using different methods for representation of the data set, hierarchical clustering, and nonlinear constrained optimization. Coverage error was calculated for both CIELAB and CIE2000 values. Recorded values were compared with coverage error of Vitapan Classical (VC) shade guide. Wilcoxon signed-rank test for paired samples and linear regression were used in statistical analysis.

RESULTS

Coverage error of VC was 4.1 (SD 1.8), ranging from 0.5 to 11.5 DeltaE(ab). Group A shades had the best match for human teeth (43.9%) followed by Groups C (24.1%), B (20.4%), and D (11.7%) shades, respectively. CIELAB coverage error of the newly designed 24-tab shade guide using clustering and optimization was 2.05 (0.95) and 1.96 (0.92), respectively. Corresponding CIE2000 coverage error values were 1.43 (0.68) and 1.40 (0.65), respectively. A significant difference between results obtained using clustering and optimization was determined. CIELAB color differences were greater, but highly correlated as compared with their CIE2000 counterparts (DeltaE(00)= 0.64 x DeltaE(76)+ 0.13, r > 0.99).

DISCUSSION

This study demonstrated that, compared with existing shade guides, future shade guides can provide either (a) similar coverage of tooth color with fewer tabs, thus simplifying shade matching procedure, or (b) better coverage of tooth color with a similar number of tabs, in both cases increasing the chances of satisfactory matches and, consequently, better esthetics.

CONCLUSIONS

Both clustering and optimization enabled better representation of tooth color as compared with an existing dental shade guide. Optimization outperformed clustering and is therefore recommended as a method of choice for representation of tooth color and designing of dental shade guides.

Comparison of the shade matching ability of dental students using two light sources

STATEMENT OF PROBLEM

Shade selection is affected by a host of variables, including lighting.

PURPOSE

The purpose of this study was to assess the ability of dental students to match shades under natural lighting and using a light-correcting device, specifically to determine whether there are differences based on: (1) year in school, (2) gender of student, and (3) light source.

MATERIAL AND METHODS

A 14-item shade matching quiz (SMQ) and a questionnaire were field tested. No major modifications were made to SMQ or questionnaire. Demographic information included year in school, age, gender, previous experience, and Ishihara's Tests for Color-Blindness. The SMQ was administered on separate occasions during the spring and summer, under natural light (SMQ-NL) and using the light-correcting device (SMQ-CL). For each of the 14 items, students (n=216) were to select the matching shade tab from 5 preselected tabs. Statistical analyses included ANOVAs, paired t tests, and independent t tests (alpha=.05).

RESULTS

A total of 165 male and 51 female students participated, with an average age of 26 years. SMQ scores of 10 color-deficient students were excluded. There were no significant differences in SMQ-NL and SMQ-CL among the first through fourth year students (ANOVA), nor between men and women (t tests). The SMQ scores were significantly higher with the light-correcting device than with natural light: 11.4 +/- 1.9 and 10.4 +/- 2.0, respectively (paired t test, P<.001). With and without the light-correcting device, the Vita C shades were less likely to be matched than the Vita A or B shades (paired t tests, P<.001).

CONCLUSIONS

Dental students' shade matching abilities were better with a light-correcting source than under natural light. Gender and experience were not found to be factors in matching shades. The Vita C shades were least likely to be matched.

Clinical Color Match of Porcelain Visual Shade-Matching Systems

BACKGROUND

Accuracy of the total color replication process has not been clinically evaluated for various porcelain visual shade-matching systems.

PURPOSE

The purpose of this study was to evaluate the final color replication process of three porcelain visual shade-matching systems. Subjects' natural dentition was compared with laboratory-fabricated individualized porcelain shade tabs.

MATERIALS AND METHODS

Shade matches of 10 subjects' incisors were obtained using three different porcelain visual shade-matching systems. Commercial laboratories fabricated one corresponding individualized porcelain shade tab for each incisor per visual shade-matching system selection. Color-match evaluations of the fabricated individualized porcelain shade tabs to the corresponding teeth were completed by prosthodontists' consensus and by subjects' self-evaluation using the US Public Health Service criteria. Statistical analysis was carried out on the combined evaluations with logistic regression and the Generalized Estimating Equation for repeated measures.

RESULTS

The Vitapan 3D Master/Omega 900 system (Vident Inc., Brea, CA, USA) was significantly more likely than the Vita Lumin Vacuum/VMK 68 system (Vident Inc.) to obtain a clinically acceptable color match (odds ratio [OR]=6.31; 95% CI=1.24-32.07). The likelihood of obtaining a clinically acceptable color match through subjects' self-evaluation was found to be significantly higher compared with prosthodontists' consensus (OR=2.75; 95% CI=1.27-5.94).

CONCLUSIONS

Within the limits of this preliminary study, significant differences in clinical acceptability were seen between the color matches of the fabricated individualized porcelain shade tabs from different systems and subjects' central incisors. Subjects' range of acceptability was much broader compared with that of the prosthodontists in assessing the color match of the fabricated porcelain shade tabs.

CLINICAL SIGNIFICANCE

The use of certain porcelain visual shade-matching systems may result in a clinically acceptable color match of the final restoration more readily than the use of other systems. Color-match evaluation of final restorations should be accomplished through a consensus between prosthodontists and patients, given the difference in thresholds of acceptability.

The use of digital imaging for colour matching and communication in restorative dentistry

OBJECTIVE

To develop a shade matching method based on digital imaging and to compare observers' ability using this method with the conventional one set against a spectrophotometric 'gold standard'.

METHODS

Two Vita Lumin shade guides were used in this study, nine shades being selected from the first Vita Lumin shade guide, A2, A3, A3.5, B2, B3, B4, C1, C2 and C3. A second shade guide was used to match the selected shades. A Nikon Coolpix 990 digital camera with Nikon SB21B ring flash was used to record the digital images of the shade tabs of the two shade guides and the images were processed using Adobe Photoshop software. A total of 27 samples (three replicates of each shade of the nine tabs selected) were matched with a digital shade guide prepared from the digital images of the second shade guide by 10 observers on a computer screen (computerised matching method). The 10 observers also matched the same shade tabs using the conventional matching method simulated in a phantom head. In addition, colour values were obtained from the digital images using Adobe Photoshop and quantified according to an internationally recognised scale as CIELAB colour values, L*,a*,b*. The relationship of the digitally derived CIELAB values to the CIELAB values obtained using a reflectance spectrophotometer was investigated.

RESULTS

The cross tabulation statistical analysis showed a statistically significant difference (p<0.001) between the conventional method and the computer method with a 43% and 61.1% correct match respectively. There was also a statistically significant difference between observers in both methods (p<0.001 and p<0.04 for the conventional and computer methods respectively). A statistically significant high correlation of the CIELAB colour values were found between both colour measurement methods (p<0.001).

CONCLUSION

The observers' shade matching performance was significantly better with the computer method compared with the conventional one. There was a large variation in the observers' matching ability. The digital camera can be used as a means of colour measurements in the dental clinic.

Designing visually optimal shade guides

STATEMENT OF PROBLEM

Dental shade guides do not provide a broad coverage of tooth colors. There is a need for shade guides that can provide closer color matches.

PURPOSE

The purpose of this study was to propose and assess a visually optimal shade guide for tooth color matching.

MATERIAL AND METHODS

With the use of a spectrophotometric approach, the color distribution (L*a*b*) of 150 extracted human teeth and 3 commercially available shade guides (Vita Lumin V, Trubyte Bioform Color Order Shade Guide, and Vitapan 3D-Master Shade System) was measured. With the use of a hierarchical clustering approach, a series of shade guides was designed with a varying number of tabs. The average error (DeltaE) between colors from each shade guide and the extracted teeth was computed.

RESULTS

The proposed visually optimal shade guide had the smallest average error of all guides tested. The new guide achieved lower error with fewer shade tabs than the 3 commercial systems evaluated.

CONCLUSION

Within the limitations of this study, it was demonstrated that a hierarchical clustering technique can be used to design a visually optimal shade guide for a given population with a flexible degree of control over the mean error and number of tabs.

Advances in color matching

Recent advances in color matching have been driven by the market demand for high-quality esthetic restorations. Improved shade guides, availability of shade-taking devices, and research in the area of human color vision have improved the potential of clinicians to achieve excellent color-matched restorations. A thorough understanding of appearance attributes of natural teeth is required along with these new tools to maximize shade-matching results.

In vivo quantitative evaluation of tooth color with hand-held colorimeter and custom template

This article presents a technique for quantitatively evaluating the color of teeth, as well as color change in restorations and tooth surfaces. Through use of a custom template made of a thermoplastic polymer and a dental colorimeter, tooth surface color can be recorded periodically at the same location intraorally.

A shade selection technique

The purpose of this article is to present a variation on the standard technique of shade selection by use of the Vitapan 3-D master "tooth" guide and the Vitapan 3-D master "dentin" guide together. The dentin guide is used first to select the shade determinants, and the tooth guide is used to verify them.

Intrarater repeatability of shade selections with two shade guides

STATEMENT OF PROBLEM

Color research has shown that shade guides do not always represent the color of natural teeth. Moreover, visual evaluation has been found to be unreliable and inconsistent.

PURPOSE

This investigation evaluated the effects of 2 shade guides on the intrarater repeatability (reliability) of prosthodontists and general practitioners with regard to shade selection.

MATERIAL AND METHODS

Ten prosthodontists and ten general practitioners (all men, 35-45 years old) with an average practice experience of 14 years participated in this study. Examiners were tested to eliminate color blindness. Each clinician used Vita Lumin Vacuum and Vitapan 3D-Master shade guides to determine the shades of the maxillary right canines of 20 patients following a standard protocol. The identification codes of the shade tabs were masked to prevent shade memory. All teeth were polished before each shade selection, and the selection process was standardized for controlled lighting and procedures. Shade selections were randomly repeated 1 month later by the same practitioners on the same group of patients in accordance with the same shade-selection protocol. Analysis of variance and t tests for individual comparisons among means were performed (P<.05).

RESULTS

Significant interactions were found between the effects of shade guide system and specialty training on intrarater repeatability (P<.0001, analysis of variance). The intrarater repeatability of prosthodontists was significantly higher than that of general practitioners when the Vita Lumin Vacuum shade guide was used (P<.0001, t test). Use of the Vitapan 3D-Master shade guide significantly improved the intrarater repeatability of general practitioners compared with the Vita Lumin Vacuum shade guide (P<.0005). This improvement was not significant, however, among prosthodontists (P=.2861).

CONCLUSION

Within the limitations of this study, the prosthodontists demonstrated superior intrarater repeatability in shade selection, especially when the Vita Lumin Vacuum shade guide was used. Use of the Vitapan 3D-Master shade guide notably improved intrarater repeatability among the general practitioners.

Evaluation of a newly developed visual shade-matching apparatus

PURPOSE

This study evaluated a newly developed visual shade-matching apparatus, Shademat Visual+, as well as the influence of tab arrangement, clinician gender, and years in practice on shade-matching quality.

MATERIALS AND METHODS

A group of 129 color-normal evaluators-dental students and general dentists-matched the shade of four ceramometal crowns using the Vitapan Classical shade guide. Crowns were positioned onto the upper member of an artificial head and fastened to the headrest of the dental chair or Shademat Visual+. Shade tabs were arranged according to the manufacturer's suggestion or according to deltaE* in relation to the "lightest" tab and divided into groups (alternative arrangement). The evaluators matched the shade of four ceramometal crowns both in daylight and using the Shademat Visual+ artificial light source. The color coordinates were determined using digital image analysis. Based on deltaE* values, each shade-matching result was ranked from 1 (the worst match) to 16 (the best match) points.

RESULTS

The evaluators achieved a better result in Shademat Visual+ trials than in daylight trials (13.2 points vs 12.4 points; P < .001). For the same ceramometal crown, 12.7 points were recorded in daylight trials with the manufacturer-suggested arrangement, and 13.7 were recorded with the alternative arrangement (P< .001). Corresponding values for Shademat Visual+ trials were 13.6 points and 14.6 points, respectively (P< .001). Female-male and student-dentist evaluator differences were not significant.

CONCLUSION

The Shademat Visual+ apparatus enabled better shade-matching results than daylight. The alternative tab arrangement enabled better results than the manufacturer-suggested one. Gender and years in practice did not influence shade-matching quality.

Evaluation of visual and instrument shade matching

STATEMENT OF PROBLEM

Visual color matching to determine shades in dentistry is inconsistent and unreliable. If accurate, instrumental measurement of tooth color would provide objective, quantified data to match natural teeth to clinical shade guides.

PURPOSE

This study evaluated and compared the ability of a new computerized colorimeter and a simple visual test to match ceramic shade guide teeth.

MATERIAL AND METHODS

Thirty-one (n = 31) observers with normal color vision were allowed unlimited time to match one set of Vita Lumin shade guide teeth to the corresponding shade guide teeth of a second Vita Lumin shade guide. The same test was administered to 14 of the observers several months later to determine within-subject variability. A computerized colorimeter (Colortron II) equipped with a positioning guide was used to measure the middle third of each shade guide tooth. Through a "match tool" present in the computer's software, readings from one shade guide were matched with readings of the other shade guide by using CIELAB measurements and DeltaE values. The mean number of correct matches by the colorimeter and of correct matches in visual test were compared with a 1-tailed t test. Repeatability for both tests was determined with a paired t test.

RESULTS

The Colortron II instrument correctly matched 8 of the 16 tabs (50% correct), whereas visual matching by examiners averaged 7. 7 of 16 correct matches (48% correct) (standard deviation 2.7). No statistically significant differences existed between the 2 methods. The colorimeter demonstrated 100% repeatability and the visual test demonstrated fair repeatability (correlation coefficient r =.60).

CONCLUSIONS

Shade determination by visual means was inconsistent. Accuracy of a new colorimeter in matching porcelain shade guide teeth was only slightly better.

Using a computer color-matching system in color reproduction of porcelain restorations. Part 3: A newly developed spectrophotometer designed for clinical application

This paper reports the development of a newly modified, noncontact spectrophotometer for clinical use. The instrument is capable of accurately measuring the color within small areas (1 x 2 mm) of a tooth. This spectrophotometer used a 45 degree/0 degree geometry, a 150W halogen lamp, and fiberoptics to focus the light, together with a lens having a focal point distance of 85 mm. A movable platform was added to the apparatus to automatically scan and measure the color of specific areas. Short-term repeatability indicated the color difference delta E to be approximately 0.15.