Quantitation of vital bleaching by computer analysis of photographic images

Digital Shade Matching in Dentistry: A Systematic Review

The pursuit of aesthetic excellence in dentistry, shaped by societal trends and digital advancements, highlights the critical role of precise shade matching in restorative procedures. Although conventional methods are prevalent, challenges such as shade guide variability and subjective interpretation necessitate a re-evaluation in the face of emerging non-proximity digital instruments. This systematic review employs PRISMA protocols and keyword-based search strategies spanning the Scopus®, PubMed.gov, and Web of ScienceTM databases, with the last updated search carried out in October 2023. The study aimed to synthesise literature that identified digital non-proximity recording instruments and associated colour spaces in dentistry and compare the clinical outcomes of digital systems with spectrophotometers and conventional visual methods. Utilising predefined criteria and resolving disagreements between two reviewers through Cohen's kappa calculator, the review assessed 85 articles, with 33 included in a PICO model for clinical comparisons. The results reveal that 42% of studies employed the CIELAB colour space. Despite the challenges in study quality, non-proximity digital instruments demonstrated more consistent clinical outcomes than visual methods, akin to spectrophotometers, emphasising their efficacy in controlled conditions. The review underscores the evolving landscape of dental shade matching, recognising technological advancements and advocating for methodological rigor in dental research.

Visual and digital tooth shade selection methods, related effective factors and conditions, and their accuracy and precision: A literature review

OBJECTIVE

Despite developments of dental shade selection methods, shade selection is still a challenge affecting esthetic outcomes. The purpose of this review was to discuss visual and digital shade taking methods, related effective factors and conditions, and their accuracy and precision to find out the most accurate, precise shade selection method available in dentistry.

OVERVIEW

The key terms of accuracy, background, ceramic, color, colorimeter, color analysis, color science, color measurement, color measuring instrument, color matching, composite resin, dental/tooth shade guide, digital camera, esthetics, imaging, imaging application/program/ software, intraoral scanner, light source, photography, precision, shade, shade matching/ determination/prediction/reproduction/selection, shade taking device, spectrophotometer, spectrophotometry, tooth color measurement, tooth color/shade, and visual perception were used separately and jointly to detect related English-language articles published between January 1, 1985, and January 1, 2021. Electronic/non-electronic searches of Google Scholar/PubMed/Scopus/Web of Science were accomplished. Consequently, 249 articles were considered. Accordingly, the digital methods show higher accuracy and precision compared to the visual methods while requiring to be enhanced regarding accuracy to achieve ideal shade taking results.

CONCLUSIONS

Dental spectrophotometers provide the highest overall accuracy and precision among different shade selection methods while needing clinical setting to control related effective factors/conditions and technological improvement to perform optimally.

CLINICAL SIGNIFICANCE

Different factors can affect the accuracy and precision of tooth shade selection methods and devices. The understanding of these effective factors may lead to a standard shade taking protocol using accurate, precise methods and devices.

Accuracy and repeatability of different intraoral scanners on shade determination

OBJECTIVE

To evaluate the accuracy and repeatability of different intraoral scanners on shade determination.

MATERIALS AND METHODS

Ten different shades of Vita Mark II blocks were used. A disc-shape specimen (10 mm in diameter and 1 mm thick) per ceramic block was fabricated. Ten color measurements per specimen were performed by each instrument (Vita Easyshade V [control], 3shape Trios, Cerec Omnicam, Cerec Primescan) and recorded in Vita Classic color system. The number of correct shade match per instrument for each shade was recorded. Instrumental accuracy was compared using Cochran Q test and repeatability was analyzed using Cronbach's alpha.

RESULTS

There was a significant difference in the instrumental accuracy for shade determination (p < 0.001). There was no statistical difference between the Easyshade V (78%) and the 3Shape Trios (66%) (p > 0.05), with the latter being similar to the other scanners Primescan(63%) and Omnicam (57%) (p > 0.05). No significant difference was found (p > 0.05) when different shades were evaluated by the same instrument. Similar repeatability was found for the different devices, ranging from 44.3% for Easyshade to 51.9% for Omnicam.

CONCLUSION

The evaluated instruments showed less than expected repeatability and accuracy on measuring different dental shades. Therefore, caution should be exercised when using instrumental shade determination, which should be accompanied by experienced human visual assessment.

CLINICAL SIGNIFICANCE

The outcome of this study might help clinicians evaluate the performance of intraoral scanners as a shade matching tool.

Spectrophotometric Evaluation of Shade Selection with Digital and Visual Methods

Aim

The main purpose of the study was to learn the possible shade differences between human eye and the digital method with spectrophotometric methods.

Materials and Methods

Fifty dental students of age groups 18-25 with maxillary right central incisor after undergoing oral prophylaxis were included in this study. Before undergoing shade selection, standardization protocol was followed. The shade of the right maxillary central incisor was determined by using the following methods: visual, spectrophotometer, and digital photography. The shades obtained by both spectrophotometer and visual methods are compared and similarly L*, a*, and b* values obtained by both spectrophotometer and digital methods are compared. Finally these comparisons are subjected to statistical analysis.

Results

Z and P values of digital and spectrophotometric methods were found to be statistically significant. Tooth shade selected between spectrophotometric and visual method was analyzed by using chi-square test, which shows highly significant value.

Conclusion

It was concluded that the digital photography can be used as one of the reliable methods for shade selection in a clinical setup.

Effect of different beverages and storage period on bis-acryl color stability using two assessment methods

OBJECTIVE

This study aimed to evaluate the color stability (ΔE₀₀ ) of bis-acryl resins after different immersion solutions and storage time by different evaluation methods.

MATERIALS AND METHODS

Sixty specimens (n = 30) were prepared from Protemp 4 and Structur 3. The specimens were divided into three groups (n = 10), according to the immersion solution (artificial saliva, cola beverage, and yerba mate tea) and evaluated at two storage times (7 and 14 days). The ΔE₀₀ of each group was calculated using color coordinates obtained by a spectrophotometer and by a digital method, using the CIEDE2000 color difference formula. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05).

RESULTS

The 7-day period presented the lowest ΔE₀₀ values, regardless of the material and solution evaluated for both evaluation methods (ΔE₀₀  < 0.93; ΔE₀₀  < 3.12). The immersion solution with the highest color change was yerba mate tea after 14 days (ΔE₀₀  > 2.11). For digital analyses, all materials and solutions at both times presented ΔE₀₀ values higher than the clinically acceptable (ΔE₀₀  > 1.8), while in spectrophotometer only in yerba mate tea (14 days) Structur was above the clinical acceptability level.

CONCLUSIONS

Yerba mate tea was the immersion solution with a higher color change in both materials and assessment methods. The highest values were found after 14 days of immersion, regardless of the solution. The ΔE₀₀ for the digital method was higher than the spectrophotometer analysis.

CLINICAL SIGNIFICANCE

It is important to identify the influence of staining beverages on interim materials used in patients requiring temporary rehabilitation. The use of a spectrophotometer seems to be more accurate than the digital method for the evaluation of color parameters of the tested materials.

The combined use of a nonabrasive, activator-containing toothpaste and a light emitting diode device improves the onset time of tooth whitening

Objective

The objective of this randomized clinical study was to assess the onset time of the whitening effect of a combined use of a nonabrasive, activator-containing toothpaste and a light emitting diode (LED) device, compared to that of the toothpaste alone.

Materials and Methods

A nonabrasive, activator-containing toothpaste was used twice daily alone or combined with an LED device for 15 days. The onset of the tooth whitening effect was evaluated through tooth color (a* b*, CIELAB) and tooth whiteness (WIO) by image analysis of standardized images. Local tolerance was assessed at days 1, 8, and 15.

Results

On day 8, a significant (P = 0.003) tooth whitening effect compared to day 1 was observed with the toothpaste and the LED device, sustaining until the end of the study. Whitening using the toothpaste alone was significant compared to day 1 after 15 days, only. One subject reported mild redness, itching, and burning on day 1 on the gum of the lower jaw that was possibly related to with the toothpaste. The subject withdrew from the study. No adverse event was reported in the group using the LED device.

Conclusion

Both tooth whitening methods had a significant whitening effect after 15 days of use. However, the onset of whitening was significantly faster when using the nonabrasive, activator-containing toothpaste combined with an LED device. The toothpaste and LED device were both safe.

Evaluation of Natural Tooth Color Space of the Indian Population and Its Comparison to Manufacturer's Shade Systems

PURPOSE

This study evaluated the natural tooth color space of the Indian population and compared it with the manufacturer's shade systems.

MATERIALS AND METHODS

Maxillary central incisors of individuals aged 18-30 years and shade tabs of Vita Lumin vaccum (VL), Vitapan 3D master (V3D), and Shofu's Vintage Halo (SVH) shade guide were digitally photographed under standardized conditions. L*a*b* values from middle part of tooth and shade tab were attained using Adobe Photoshop 7.0 software. Comparative evaluation between the natural teeth and shade tabs was done, and color differences were noted and analyzed using appropriate software.

RESULTS

The L*a*b* values of the Indian population displayed a broader range than the shade guides. The mean Δ E* for VL shade guide was 7.22, 7.99 for SVH, and 8.39 for V3D, which was statistically significant. Color space of the Indian population on displayed an elongated cone with an irregular base. The plots of all the three shade guides were narrower and shorter and deficient in the blue-green region as compared to the population.

CONCLUSIONS

Within the limitations of this study, the mean color difference between the Indian population and the three shade guides was above the acceptability thresholds (ΔE* = 2.7-6.8). VL, V3D, and SVH shade guides were deficient in their coverage and therefore can be considered inconsistent.

Effect of Different Esthetic Post-Core Materials on Color of Direct-Composite Restorations: A Preliminary Clinical Study

BACKGROUND The purpose of this study was to determine the influence of 2 different esthetic post materials on the final color of direct-composite restorations by using a digital technique under in vivo conditions. MATERIAL AND METHODS We included 22 pulpless incisor teeth treated with conventionally cemented zirconia (n=11) and polyethylene fiber (n=11) posts in the study. Teeth were restored with a hybrid resin. The color of direct-composite restorations and contralateral control teeth was measured using a digital technique. The Commission Internationale de L'Eclairage, or CIE, L*a*b* and RGB color systems were investigated. Descriptive statistical analysis was performed for the CIE L*a*b* values. Color differences (ΔE) for the average L*, a*, and b* color parameters between every pair of groups were calculated (P>.05). RESULTS Significant differences were not found in the color difference luminosity (lum), R, G, B, and L* a* b* values between the zircon-rich glass fiber post (Z) and contralateral control teeth (Cz) (P>.05) and between the polyethylene fiber post (P) and contralateral control teeth (Cp) (P>.05). However, there was a statistically significant difference between the color a* values of the polyethylene fiber post (P) and contralateral control teeth (Cp) (p<0.05). Color differences (ΔE) between the zircon-rich glass fiber post (Z) and contralateral control teeth, and the polyethylene fiber post (P) and contralateral teeth were not statistically significant (P>.05). CONCLUSIONS Definitive restorations were equally affected by the 2 materials. Both materials can be used reliably in clinical practice. However, further research that focuses on the effect of intraoral conditions is needed.

Comparison of photographic and conventional methods for tooth shade selection: A clinical evaluation

Aim:

This study aimed to compare three different methods used for shade selection, i.e., visual method, spectrophotometer, and digital photography method.

Materials and Methods:

Fifty participants were selected from the Out Patient Department of Prosthodontics. Presence of the maxillary right central incisor with no history of any restorative or endodontic procedures was the primary inclusion criterion. The shade of the right maxillary central incisor was determined using all the three shade selection procedures, namely, visual, spectrophotometric, and digital photography method for all the selected participants. The shades obtained in the visual method using a shade guide were noted down for further comparisons. The spectrophotometer reported the L*, a*, and b* values along with the actual shade whereas the digital photography method reported only the L*, a*, and b* values. The agreement between the readings obtained by the three different methods was compared and subjected to appropriate statistical analysis.

Results:

The results showed that when the three methods studied were compared, there was a statistically significant proportion of agreement between spectrophotometric and visual method (P < 0.01) with higher proportion of “yes” (agreement) and between the spectrophotometric and digital photography method (P < 0.01) with higher proportion of “yes” (agreement). Coefficient of agreement (using Kappa coefficient) between spectrophotometric and visual shades revealed a fair agreement. The mean ΔE was 1.69. There was a statistically significant difference between the proportion of ΔE more than and <2, between spectrophotometric and digital photography methods (P < 0.01) with higher proportion of <2 ΔE. Furthermore, percentage of agreement between shades obtained by the visual and spectrophotometric method showed maximum agreement with A1 shade.

Conclusion:

It was concluded that the digital photography method emerged as a reliable method for shade selection in a clinical setup.

A Study on Possibility of Clinical Application for Color Measurements of Shade Guides Using an Intraoral Digital Scanner

PURPOSE

To assess if color measurement with intraoral scanner correlates with digital colorimeter and to evaluate the possibility of application of a digital scanner for shade selection.

MATERIALS AND METHODS

The L*a*b* values of the five shade tabs (A1, A2, A3, A3.5, and A4) were obtained with an intraoral scanner (TRIOS Pod) and a colorimeter (ShadeEye). Both devices were calibrated according to the manufacturer's instructions before measurements. Color measurement values were compared with paired t-test, and a Pearson's correlation analysis was performed to evaluate the relationship of two methods.

RESULTS

The L*a*b* values of the colorimeter were significantly different from those of the digital scanner (p < 0.001). The L* and b* values of both methods were strongly correlated with each other (both p < 0.05). The device repeatability in both methods were reported to be excellent (p < 0.05). Within the limitations of this study, color measurements with digital intraoral scanners and computer-assisted image analysis were in accordance with those of the colorimeter with respect to L* and b* values; however, all the coordinates of shade tabs were significantly different between two methods.

CONCLUSIONS

The digital intraoral scanner may not be used as the primary method of color selection in clinical practices, considering significant differences in color parameters with colorimeter. The scanner's capability in shade selection should be further evaluated.

Consistency and standardization of color in medical imaging: a consensus report

This article summarizes the consensus reached at the Summit on Color in Medical Imaging held at the Food and Drug Administration (FDA) on May 8-9, 2013, co-sponsored by the FDA and ICC (International Color Consortium). The purpose of the meeting was to gather information on how color is currently handled by medical imaging systems to identify areas where there is a need for improvement, to define objective requirements, and to facilitate consensus development of best practices. Participants were asked to identify areas of concern and unmet needs. This summary documents the topics that were discussed at the meeting and recommendations that were made by the participants. Key areas identified where improvements in color would provide immediate tangible benefits were those of digital microscopy, telemedicine, medical photography (particularly ophthalmic and dental photography), and display calibration. Work in these and other related areas has been started within several professional groups, including the creation of the ICC Medical Imaging Working Group.

Effect of dental bleaching after bracket bonding and debonding using three different adhesive systems

OBJECTIVE

To evaluate the influence of bonding and debonding of orthodontic brackets on dental in-home bleaching, taking into account three different adhesive systems.

METHODS

Forty-four bovine incisors were divided into four groups according to the primer system used for orthodontic bracket bonding. Following the debonding of orthodontic brackets, the teeth were stored in staining solution for 96 hours. Then, teeth were whitened using 10% carbamide peroxide for two weeks at a 6-hour-a-day regime. Standardized digital photographs were taken at the following intervals: T₀ (initial); T₁ (after debonding); T₂ (after pigmentation); T₃, T₄ and T₅ representing 1, 7, and 14 days of bleaching. Repeatability and stability tests were carried out to check the method accuracy. Images were analyzed using Adobe Photoshop 7.0 software considering (L*a*b*) color coordinate values and a modified color difference total (ΔE').

RESULTS

The results of this study (ANOVA and Tukey; p < 0.01) demonstrated that after 7 days of bleaching, experimental groups showed significantly less teeth whitening compared to the control group. However, there were no significant color differences between the groups after 14 days, according to values of lightness (L*).

CONCLUSIONS

Regardless of the adhesive primer system applied, bonding and debonding of orthodontic brackets alters the outcome of tooth whitening in the first 7 days of bleaching, however it has no influence on the whitening of the dental structure after 14 days of in-home dental bleaching with 10% carbamide peroxide.

Tooth, skin, hair and eye colour interrelationships in Greek young adults

The purpose of this study was to investigate the possible interrelationships of teeth, skin, eye and hair colour. A portable colorimeter (Shade Eye NCC/Shofu) was used to record the colour in the CIELAB system of the upper right incisors in 150 dental school students, along with their skin colour at three different areas. Natural hair and eye colour was classified into several categories by a trained examiner (ICC 0.93-0.99). One-way ANOVA and correlation tests were used to statistically analyse the data. Skin was found to have significantly higher L*, b* but lower a* values than teeth (p < 0.05). A significant correlation (p < 0.05) of teeth to skin L* and a*colour coordinate was found, but not to b* coordinate (p > 0.05). Hair tones were not correlated to teeth L* or b*, but only to a*coordinate. Teeth and eye colour coordinates were not correlated (p > 0.05). Eye and hair tones were found to have the highest significant correlation (ρ = 0.369). In conclusion, teeth of this cohort were found to be lighter, less red and yellow than the skin. Teeth colour was not related to eye colour, but lighter teeth were found to be associated with lighter skins, and redder lateral incisors to lighter hair. Darker facial skins or yellower forehead areas were also associated with darker hair and vice versa. The clinical relevance of the study is that the investigated facial characteristics are inter-correlated weakly to moderately, and for this reason predicting the colour parameters of one facial characteristic by another would not be accurate, but helpful for a rough colour selection as associations show.

Digital Computer Matching of Tooth Color

This study aimed to determine the validity of the digital photocolorimetric (PCM) method in matching the color of human teeth. First, two Vitapan Classical shade guides, each containing 16 shade guide teeth, were visually shade matched, and digital photographs of each three pair of shade guide teeth were taken in a color matching booth. Secondly, visual shade matching of the upper central incisors of 48 subjects was performed by two prosthodontists independently in a chair, using the Vitapan Classical shade guide. The three closest shade guide teeth were visually selected and ranked in order of preference, for which digital photographs were taken under ceiling daylight-corrected fluorescent lighting. All digital images were analyzed on a computer screen using software to calculate the color difference between the reference tooth and other teeth in the same digital image. The percent color matching for the shade guide teeth and human teeth was 88% and 75%, respectively. There was no statistically significant difference in matching the tooth color between the shade guide teeth and human teeth. The digital PCM method is valid for the range of human teeth based on the Vitapan Classical shade guide. This method enhances communication with the laboratory personnel in matching the tooth color.

Toluidine blue color perception in identification of oral mucosal lesions

The objective of this study is to examine observer agreement on the rank of the color tones after toluidine blue staining of a mucosal lesion. Cohort study with repeated measures is the design of the study. Twenty observers ranked and scored 8 specified areas on the color images of a lesion before and after toluidine blue application in two sessions. Inter and intra-observer variations were analyzed with Cohen's kappa. The L* (the black-white axis), a* (red-green axis), and b* (yellow-blue axis) values were measured and set as the gold standards. Intra and inter-observer agreements were к = 0.86 and к = 0.854. All color parameters were effective on the color ranking order (pL* = 0.00, pa* = 0.007, pb* = 0.00), although L* and b* were more effective on the ranking of the samples than a*. Areas that appeared pale blue visually had a significant blue component, but the observers were confused with the effect of whiteness of the area in clinical decision making.

Quantitative analysis of KTP laser photodynamic bleaching of tetracycline-discolored teeth

OBJECTIVE AND BACKGROUND DATA

Photodynamic bleaching is a recently developed method that may be suitable for photo-oxidation of difficult internal stains. This study examined the outcomes of photodynamic bleaching for treatment of confirmed cases of tetracycline discoloration, when used as a single-appointment procedure.

MATERIALS AND METHODS

Digital analysis of standardized pre- and post-treatment digital photographs of a total of 90 maxillary incisors from 23 adult patients undergoing photodynamic bleaching was undertaken. The patients were treated by a visible green KTP laser (wavelength 532 nm) combined with a rhodamine-B photosensitizer gel (Smartbleach) applied to the teeth and activated for 30 sec. Each tooth underwent four cycles of 30 sec of laser exposure. Digital image analysis was undertaken in a blinded manner, and we examined changes in the four maxillary incisors in terms of blue pixel intensity (yellowness).

RESULTS

Least squares linear regression analysis and a one-tailed paired t-test using the matched pairs of pre- and post-treatment data for mean blue pixel intensity showed that a significant lightening effect was achieved by the bleaching treatment. Significant increases in blue pixel intensity (reductions in yellowness) occurred in 78% of the teeth treated.

CONCLUSIONS

In-office KTP laser photodynamic bleaching provides a clinically useful improvement in tooth shade in teeth with tetracycline discoloration.

Measurement of discolouration of orthodontic elastomeric modules with a digital camera

The objective of this study was to measure discolouration using a digital camera on various types of clear orthodontic elastic modules, immersion solutions, and time periods to determine whether the cause of discolouration of these modules was due to simple staining, chemical degradation, or both. Three types of clear orthodontic elastomeric modules were investigated [Plastic ligatures (AO); Power 'O's 012 (OC); dispense-A-tie (TP)]. The elastomeric modules were immersed in the stretched condition in distilled water (control group) and in 75 per cent ethanol for chemical degradation and 2 per cent methylene blue for simple staining. After 0, 1, 2, 3, 6, 9, 12, 15, 18, and 21 hours and 1, 2, 3, 4, and 5 days of immersion, digital images of the modules were taken and processed using commercial software. The differences in colour changes depending on the type of elastomeric modules, immersion solution, and immersion period were analysed using a three-way analysis of variance and Tukey's multiple comparison test. The colour changes in the ethanol and methylene blue solutions by immersion period were analysed with regression analysis. There were significant differences in discolouration depending on the type of elastomeric modules, immersion solution, and immersion period (P < 0.05). The range of colour changes (Delta E* ab) was 1.0-20.0 units for AO, 0.6-30.0 units for OC, and 1.1-18.8 units for TP, independent of immersion solution and time. Methylene blue resulted in the greatest colour change. Discolouration due to chemical degradation by the ethanol solution mainly occurred in the first few hours, reached a plateau with no further increase over time, and was greater than staining by methylene blue in that period. Discolouration due to staining by methylene blue, however, continued to increase over the whole immersion period. Therefore, discolouration of elastomeric modules was a result of chemical degradation as well as staining in the early stages but in the later stages was due only to simple staining.

The evaluation of a novel method comparing quantitative light-induced fluorescence (QLF) with spectrophotometry to assess staining and bleaching of teeth

This study reports the development and evaluation of a novel method using quantitative light-induced fluorescence (QLF), which enables its use for quantifying and assessing whole tooth surface staining and tooth whitening. The method was compared with a spectrophotometer to assess reliability. Two experimental phases, intrinsic stain formation and tooth whitening, were conducted in vitro on 16 extracted bovine teeth. Intrinsic stains were developed via access through lingual surfaces and root canals of these teeth using tea solution (2 g/100 ml, Marks and Spencer Extra Strong Tea, Marks and Spencer, London, UK) for 6 days. Stains were removed using 33% hydrogen peroxide (VWR Prolab, Leicestershire, UK) in cycles over 150 min. Stain development/whitening was monitored with QLF (Inspektor Research systems, Amsterdam, Netherlands) and spectrophotometry (Easy shade, Vita Zahnfabrik, Bad Säckingen, Germany). Parameters Delta F for QLF and Delta E for the spectrophotometer were obtained. The progression of stain intensity and removal observed by the methods were tested for correlation using Pearson's correlation coefficient. Intra-examiner reliability for each method was tested. QLF showed a high correlation with spectrophotometry for detecting and monitoring intrinsic tooth stain progression (Pearson coefficient r was -0.987 with correlation significant p < 0.0001). For stain removal, the Pearson coefficient (r) between both methods was -0.906 with no significance p = 0.094. The use of an external reference material in combination with the inner patch QLF analysis technique had the ability to detect and measure whole tooth surface staining and its removal longitudinally. The reliability of the method shows a potential clinical application.

Coverage error of three conceptually different shade guide systems to vital unrestored dentition

STATEMENT OF PROBLEM

It remains unclear which shade guide system is most representative of the shades found in the human dentition.

PURPOSE

The purpose of this study was to determine and to compare the coverage errors (CEs) of 3 different shades in a selected population.

MATERIAL AND METHODS

The coverage errors of the following shade guide systems were evaluated to determine which shade guide system is most effective in producing the best visual shade match: (1) Vita Lumin, (2) Chromascop, (3) Vitapan 3D Master, and (4) a combination of the 3 shade guide systems. The spectral reflectance values of the central one ninth (1-mm diameter) of each shade tab (without a backing) were measured 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 color values of 359 anterior teeth were measured with the same protocol. The CEs for each of the 359 anterior teeth for each shade guide system, and with all 3 shade guide systems, were determined and averaged. Repeated measure ANOVA was used to evaluate the mean minimum CEs within-subject (shade guide system) and between-subject (age) difference as well as the interaction between these variables (alpha=.05). Then, a post hoc multiple comparison was performed using the Tukey-Kramer test.

RESULTS

A significant difference (P<.001) was found among the mean minimum CEs of the 3 shade guide systems and their combination, but not between age groups (P=.384). An interaction was found between shade guide systems and age (P<.001). The Tukey-Kramer test revealed that the mean minimum CEs for Vita Lumin (5.39 DeltaE) and Chromoscop (5.28 DeltaE) shade guide systems were not significantly different from each other. However, the combination of all 3 shade guide systems (3.69 DeltaE) and Vitapan 3D Master (3.93 DeltaE) were significantly different from the Vita Lumin and Chromoscop shade guide system. The rankings of the shade guide systems within each age group were similar between the age groups.

CONCLUSIONS

The Vitapan 3D Master shade guide system resulted in the lowest coverage errors compared to the Vita Lumin or Chromascop shade guide systems. Coverage errors for the Vitapan 3D Master shade guide system did not differ significantly from the coverage errors when all 3 shade guide systems were combined.

Efficacy and oral side effects of two highly concentrated tray-based bleaching systems

The aim of this study was to investigate the tooth-whitening efficacy and oral side effects of the two tray-based bleaching systems Visalys whitening (VW) and Opalescence PF (OP). A stratified, randomised distribution of the subjects (n = 60) to two treatment groups was performed according to baseline tooth brightness (L* values) as determined by colourimeter and to the criteria smoker/non-smoker. Tooth colour was evaluated by measuring L*a*b* values generated from standardised digital image analysis with Adobe Photoshop of the facial surfaces of the right central maxillary incisor. Tooth hypersensitivity, with intensity graded from 0 (no hypersensitivity) to 10 (high hypersensitivity), was assessed chair-side using an air syringe. After bleaching therapy, both treatment groups demonstrated significant improvements in tooth colour (p < or = 0.05). A shift towards less yellow (-Deltab*) and brighter (+DeltaL*) tooth colour was observed. Deltab* was significantly higher in the OP group in comparison to the VW group, DeltaL* showed no significant difference between the both treatment groups (p < or = 0.05). After bleaching, the intensity of tooth hypersensitivity was increased significantly compared to baseline in both groups (p < or = 0.05), with no significant difference between the both groups. Both highly concentrated bleaching systems are effective as tooth-whitening systems, with few reported side effects such as transient tooth hypersensitivity.

Comparison of digital and spectrophotometric measurements of colour shade guides

Colour determination may be precisely performed with spectrophotometers, however this technique is time consuming and requires special devices. The aim of this study was to determine the correlation between the colour measurements performed on three shade guides of the same manufacturer, obtained with digital and spectrophotometric analyses. Sixty shade tabs of three shade guides were analysed to determine the L*, a*, b* values with a spectrophotometer. The same shade tabs were also imaged with a digital camera, and same colour parameters were determined on the digital images with the software. Three measurements for each shade tab were made with both methods. Statistical differences between the results of two methods were determined using anova (alpha = 0.05). Additionally, presence of any correlation between two methods within each guide was investigated by using correlation analysis. It was observed that the a* and b* values obtained by digital method were correlated with those of the spectrophotometer. Spectrophotometric analysis revealed no disparities among the L* measurements of the shade tabs of three shade guides (P > 0.05), but significant differences were observed between the L* values of the shade tabs with digital analysis method (P = 0.000). The digital method formed more subgroups than the spectrophotometer. For a* and b* values, both methods revealed significant differences among the shade tabs (P < 0.05). Additionally, both analyses revealed that colour characteristics of the first shade guide was different than the other two. The results obtained by digital method were correlated with those of the spectrophotometer, especially for a* and b* values.

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.

Tooth colour: a review of the literature

OBJECTIVES

To review current knowledge with respect to tooth colour and its measurement.

METHODS

'Medline' database for the period 1966 to the present day and 'ISI Web of Science' database for the period 1974 to the present day were searched electronically with key words tooth, teeth, colour and color.

CONCLUSIONS

The colour and appearance of teeth is a complex phenomenon, with many factors such as lighting conditions, translucency, opacity, light scattering, gloss and the human eye and brain influencing the overall perception of tooth colour. The measurement of tooth colour is possible via a number of methods including visual assessment with shade guides, spectrophotometry, colourimetry and computer analysis of digital images. These methods have successfully been used to measure longitudinal tooth colour changes when the dentition has undergone tooth whitening procedures.

Digital Photography and the Assessment of Therapeutic Results after Bleaching Procedures

The therapeutic outcome of tooth-bleaching procedures can be assessed by different methods, one of them being digital photography. However, none of the methods seems to be perfect. In this overview factors are discussed that have an influence on color rendition and image brightness in (digital) photography. A photographic procedure is proposed that results in comparable images. Beginning with a short description of some digital cameras currently used in dental photography, the article discusses the influence of light and camera technology on image brightness and color rendition in detail. Even if a highly standardized procedure is performed, there remain factors that affect color and brightness that cannot be excluded completely. Therefore, a photographic procedure is proposed that includes a piece of gray card in the picture as a neutral reference object. In this way, color casts can be eliminated and image brightness can be fine tuned using a standard image-editing program (Adobe Photoshop, Adobe Systems Incorporated, San Jose, CA, USA) before the relevant color values are metered by the same software.

CLINICAL SIGNIFICANCE

A photographic procedure using digital cameras is proposed that is relatively simple and sufficiently precise to allow the assessment of the therapeutic outcome of tooth-bleaching procedures.