Development of a whiteness index for dentistry

Tooth whitening: current status and prospects

As a safe, effective, economical, and convenient technique, tooth whitening is one of the most popular treatments for improving tooth discoloration. This review summarizes the theoretical and recent research developments in the classification and mechanisms of tooth discoloration, as well as the principles, agents, effects, and side effects of tooth whitening techniques. The aim is to provide a basis for the clinical treatment of tooth whitening techniques and to suggest possible new ideas for further research. The accepted mechanism of whitening is the redox reaction of oxides in the whitening reagent, and the whitening effect is remarkable. However, side effects such as tooth sensitivity and irritation of gum and other oral soft tissues can still occur. It is recommended that more monitoring be carried out in the clinic to monitor these side effects, and care should be taken to protect the soft tissues in the mouth during office whitening procedures. Furthermore, there is a need to develop new additives or natural whitening products to reduce the occurrence of side effects.

Staining and bleaching susceptibility of zirconia-reinforced lithium silicate glass-ceramics with different thicknesses, translucencies, and fabrication methods

STATEMENT OF PROBLEM

The influence of different thicknesses, translucencies, and fabrication methods on the spectrophotometric and topographical properties of zirconia-reinforced lithium silicate glass-ceramics (ZLSs) for dental restorations remains unclear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of thicknesses, translucencies, and fabrication methods on the color stability, translucency parameter, opalescence parameter, whiteness stability, transmitted irradiance, light transmittance, opacity, gloss, and roughness of ZLSs exposed to coffee staining and bleaching treatments.

MATERIAL AND METHODS

Two pressable ZLSs (VITA AMBRIA, VA and Celtra Press, CP) and 2 machinable ZLSs (VITA Suprinity, VS and Celtra Duo, CD) were examined at high translucency (HT) and low translucency (LT) levels in 2 thicknesses (n=160). The specimens were evaluated at baseline, after coffee staining, and after bleaching. The color stability (ΔE2000), translucency parameter (TP), opalescence parameter (OP), whiteness index (WID), and whiteness stability (ΔWID) were measured with a spectrophotometer. Transmitted irradiance (It), light transmission (T), and opacity (O) were obtained from a light-polymerizing unit and a polymerization light collection device. Roughness stability (ΔSa%) was determined with an optical profilometer, and gloss stability (ΔGU%) was recorded with a gloss meter. Data of ΔCIE2000, ΔWID, ΔSa%, and ΔGU% were analyzed by 4-way ANOVA, and data of the TP, OP, WID, It, T, and O were analyzed by repeated 4-way ANOVA (α=.05).

RESULTS

VS-HT exceeded the ΔCIE2000 acceptability threshold after coffee staining and bleaching protocols. Pressable ZLSs exhibited greater color stability than machinable ZLSs. The 1-mm-thick VA, CP, and CD materials exceeded the ΔWID perceptibility threshold after bleaching. The highest TP and OP was displayed by the 1-mm-thick CP after bleaching. ΔGU increased after water storage and decreased after coffee staining and bleaching. ΔSa% significantly increased after bleaching (P<.05).

CONCLUSIONS

The color stability and other spectrophotometric properties of ZLSs depended on material thickness. The effects of ZLS fabrication methods and translucency levels on their measured properties were inconsistent. Subjecting 1-mm-thick ZLS materials to acidic media adversely impacted their stainability and surface texture.

Effects of ultraviolet weathering aging on the color stability and biocompatibility of various computer-aided design and computer-aided manufacturing glass-ceramic materials

OBJECTIVES

This study assessed the changes in color stability and biocompatibility of computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramics after ultraviolet weathering (UW) aging.

METHODS

A total of 300 plate-shaped specimens (12.0 × 14.0 × 1.5 mm3) were prepared using a leucite-reinforced glass-ceramic (IPS Empress CAD; E), a lithium disilicate (IPS e.max CAD; M), and two zirconia-reinforced lithium silicate (Celtra Duo; C, Vita Suprinity; V) glass-ceramics. Specimens were divided into three groups (n = 25, each), subjected to water storage at 37 °C for 24 h (control group), or UW aging at 150 kJ/m2 (first-aged group) or 300 kJ/m2 (second-aged group). The color stability, mechanical and surface properties, and biocompatibility of the CAD-CAM glass-ceramics were investigated experimentally, followed by statistical analysis.

RESULTS

The brightness and redness or greenness were reduced in all groups after aging. After the first aging, V exhibited the largest color change and E exhibited the smallest color change. After the second aging, E exhibited the highest nanoindentation hardness and Young's modulus. The surface roughness was the highest for V after the first aging. Furthermore, the hydrophilicity of the materials increased after aging process. The cell proliferation/viability of human gingival fibroblasts was the highest in E before and after aging. Almost all cells survived for all groups based on a live/dead assay.

CONCLUSIONS

Leucite-reinforced glass-ceramic exhibit the highest color stability and biocompatibility after aging. The color stability and biocompatibility of CAD-CAM glass-ceramics depend on the aging process and material type.

CLINICAL SIGNIFICANCE

Various CAD-CAM glass-ceramics exhibit adequate color stability after UW aging. The leucite-reinforced glass-ceramics exhibit the highest color stability, cell proliferation, and viability after aging. The color stability, mechanical and surface properties, and biocompatibility of the glass-ceramics depend on the aging process and material type.

Ex vivo study of molecular changes of stained teeth following hydrogen peroxide and peroxymonosulfate treatments

White teeth can give confidence and tend to be associated with a healthier lifestyle in modern society. Therefore, tooth-bleaching strategies have been developed, including the use of hydrogen peroxide. Recently, peroxymonosulfate has been introduced as an alternative bleaching method to hydrogen peroxide. Although both chemicals are oxidizing agents, their effects on the molecular composition of the stained teeth are yet unknown. In this study, the molecular profiles of teeth bleached with hydrogen peroxide and peroxymonosulfate were compared using Liquid Chromatography-Tandem Mass Spectrometry. Statistical analyses were used to assess the samples. In addition, reference spectral libraries and in silico tools were used to perform metabolite annotation. Overall, principal component analysis showed a strong separation between control and hydrogen peroxide and peroxymonosulfate samples (p < 0.001). The analysis of molecular changes revealed amino acids and dipeptides in stained teeth samples after hydrogen peroxide and peroxymonosulfate treatments. Noteworthy, the two bleaching methods led to distinct molecular profiles. For example, diterpenoids were more prevalent after peroxymonosulfate treatment, while a greater abundance of alkaloids was detected after hydrogen peroxide treatment. Whereas non-bleached samples (controls) showed mainly lipids. Therefore, this study shows how two different tooth-whitening peroxides could affect the molecular profiles of human teeth.

Dental and composite resin discoloration induced by different hydraulic calcium silicate-based cements: two-year in vitro assessment

Few long-term studies assess the discoloration induced by hydraulic calcium silicate-based cement on dental structures. In addition, as far as we know, no long-term study has assessed the discoloration induced by these cement on composite resin. This in vitro study aimed to assess, during a period of two years, the discoloration potential of different hydraulic calcium silicate-based cements (hCSCs) on the enamel/dentin structure and composite resin restoration. A total of 40 enamel/dentin discs were obtained from bovine incisors, and 40 composite resin discs (10 mm in diameter × 2 mm thick) were fabricated. A 0.8 mm-deep cavity was made in the center of each disc and filled with the following hCSCs (n=10): Original MTA (Angelus); MTA Repair HP (Angelus); NeoMTA Plus (Avalon); and Biodentine (Septodont). An initial color measurement was performed (T0 - baseline). After 7, 15, 30, 45, 90, 300 days, and two years, new color measurements were performed to determine the color (ΔE00), lightness (ΔL'), chroma (ΔC'), hue differences (ΔH'), and whiteness index (WID). For enamel/dentin, the ΔE00 was significant among groups and periods (p<0.05). NeoMTA Plus had the greatest ΔE00. The NeoMTA Plus group had the greatest ΔE00 after two years for composite resin. Significant reduction in lightness was observed for all groups after two years (p<0.05). The most significant WID values were observed after 30 days for Biodentine (enamel/dentin) and MTA Repair HP groups (composite resin) (p<0.05). The hCSCs changed the colorimetric behavior of both substrates, leading to greater darkening over time. The Bi2O3 in the Original MTA seems relevant in the short periods of color change assessment.

Whitening Optical Effect of New Chewing Gums

Background:

Today, many treatments are available to enhance the color of teeth, but they require a few days to weeks to deliver this effect.

Objective:

To evaluate the instantaneous optical whitening effect of two new sugar-free chewing gums and one dentifrice of proven efficacy versus one placebo chewing gum.

Methods:

This was a single-blind, parallel trial. 424 participants entered the study and were randomly allocated to four groups. They received a personal silicone mask with a calibrated hole at one upper incisor to apply a dental colorimeter. The tools tested were chewing-gum containing indigotine (E132-FD&C Blue 2) and spirulina, chewing-gum containing only spirulina, chewing-gum placebo, and dentifrice containing Blue Covarine. Vita® Easyshade scored the tooth color, and the WIO and WID whiteness indexes were calculated. For chewing gums, the color of the teeth was scored before the assumption and after 2’30” of mastication. For dentifrice, participants brushed for 1’30”, then rinsed, and the color was scored before brushing and after 2’30”. Statistical analysis was performed by ANOVA and Tukey post-hoc.

Results:

The two experimental whitening chewing gums and the dentifrice significantly increased the WIO and the WID indexes from the baselines (p<0.001). Moreover, their effects were statistically greater than those reported for the placebo chewing gum (p<0.05) but not significatively different among them (p=NS).

Conclusion:

All the tested whitening tools showed an instant optical whitening perception. Further studies are required to assess the intensity of the effect over a prolonged time to meet the people's request for fast whitening tools.

The clinical trial registration no. is PVM-2020-01.

What's next in the use of opacifiers for cosmetic coatings of solid dosage forms? Insights on current titanium dioxide alternatives

The consolidated use of coatings containing E171 (i.e. titanium dioxide, TiO2) as an opacifier has made the white color of the resulting dosage forms a quality standard in the pharmaceutical and dietary supplement fields. This color is also associated with the efficiency of the coating layer in protecting the substrate from the effects of UV rays. However, health risks related to diet exposure to TiO2 has recently been advanced and its addition in coating formulations has been seriously questioned. As a consequence, in principle safer TiO2-free formulations have been recently launched on the market, especially for coatings of dietary supplements. In this work, we evaluated the overall physico-technological characteristics and performance of immediate release tablets coated with a variety of commercial cosmetic formulations free of E171. Moreover, a quantitative method based on the CIELab color space was proposed for the first time for studying the covering/coloring performance of the coating formulations. Based on the results obtained, the possibility to achieve a satisfactory covering capability and a degree of white comparable to that of a standard TiO2-containing reference with all the commercially-available ready-to-use TiO2-free products considered, without affecting the dissolution performance, was demonstrated.

Investigation of hue effects in tooth whiteness perception

OBJECTIVE

To identify the hue angles that provide the optimal perception of tooth whitening.

METHODS

Thirty-three male/female adult observers with normal color vision were recruited to assess teeth images on a color calibrated display. Images of teeth were generated which simulated color changes in each of eight hue directions in the CIE a*b* plane, each equi-distant from a baseline tooth color. Using a paired comparison study design, observers were asked to indicate which of two images had whiter teeth. The data were converted into an interval scale using Thurstone's Law of Comparative Judgment. The relationship between the hue angles and the scores was modeled by curve fitting.

RESULTS

The optimal hues were found in a region between green and blue in the CIE a*b chart. When the tooth color travels in an optimal hue direction, the same amount of color change will result in a greater change in whiteness perception than when traveling in other hue directions.

CONCLUSIONS

The optimal hues for tooth whitening were identified from the visual perception study. The most effective tooth whitening direction is to change tooth color towards the greenish-blue hue direction.

CLINICAL SIGNIFICANCE

This study gives clinicians and researchers a better understanding of tooth color hue effects in tooth whiteness perception.

The impact of tooth colour on the perceptions of age and social judgements

OBJECTIVE

Psychological research has established that the presence of dental anomalies negatively impact social judgements. This study sought to determine the effects of tooth colour on the subjective ratings of social judgements in a group of Caucasian adults.

METHODS

A cross sectional experimental analogue design comprised fifty Caucasian adults: 25 women and 25 men. A total of 54 digitally modified photographs of Caucasian males and females (darkened, natural, whitened teeth) were evaluated. All participants evaluated each of the images on 12 characteristics: popularity, friendliness, social life, success, graduation, happiness, intelligence, perceived age, introversion/extraversion, self-confidence, attractiveness and satisfaction with the tooth shade. Analysis of variance (ANOVA) was used to compare ratings.

RESULTS

Participants associated darkened teeth with poorer subjective ratings, with the highest ratings been given to whitened teeth, and natural teeth being intermediate. These trends were similar across all participant age groups and gender. Further, the gender and age groups of the images had a significant effect on the appraisals. Faces of younger models received higher ratings than the faces of older models and female images were rated higher than the males.

CONCLUSION

In the absence of other information, tooth colour exerts an influence upon the appraisals made in social situations. It appears that whitened tooth appearance is preferred to natural tooth appearance, irrespective of age and gender of the judge. The faces with more whitened dentition are perceived to be younger across all age groups and gender of the judges. Participants dissatisfied with their own tooth shade drew out more stereotypic behaviour.

CLINICAL SIGNIFICANCE STATEMENT

This research used standardised tooth colour as a basis to investigate perceived age and social functioning. As clinicians face daily challenges to achieve patient satisfaction with respect to dental aesthetics, standardizing the colour may enhance the patients' satisfaction. Further, participants dissatisfied with their own tooth shade drew out more stereotypic behaviour. The whitened dentition may impair the psychological well-being of the individuals and is probably a reason for the increasing demand for cosmetic dental procedures. These results may be instructive for the development of a psycho-educational intervention to prevent any unrealistic expectations.

Change of dental color and temperature through two bleaching agents boosted with light emitted by diodes

INTRODUCTION

The use of light sources during the application of bleaching can reduce the time and improve the results, but at the same time this can increase the dental temperature. The objective of this study was to evaluate the performance of two bleaching agents and the increase in dental temperature with the use of light emitted by diodes (LED)-unit.

MATERIALS AND METHODS

Forty third molars were obtained and randomized: the whiteness without lamp (WHN) and Pola office without lamp (PON) groups, two bleaching systems based on 35% hydrogen peroxide were used, according to manufacturer specifications. For the whiteness with lamp (WHL) and Pola office with lamp (POL) groups the same bleaching agents were light boosted. A spectrophotometer and ∆WI_D equation was used to record and analyzed teeth color. An infrared thermometer was used to record the external and internal temperature. A ∆T was obtained by the difference of the temperature of the groups with and without LED (WHN-WHL and PON-POL). For statistical analysis Kruskal-Wallis test and Anova test were performed.

RESULTS

The WHN, PON, WHL, and POL groups reported ∆WI_D values of 4.88 ± 1.08, 9.26 ± 3.27, 5.70 ± 2.48, 12.08 ± 5.44, respectively. The dates of internal temperature were 1.01 and 1.07°C, and for external temperature were 1.61 and 1.15°C respectively.

CONCLUSIONS

With the limitations of this study, both bleaching agents reported a significant increase in ∆WI_D with and without association of light. Significant temperature increases were also observed. The highest average temperature increase was approximately 1.61°C.

CLINICAL SIGNIFICANCE

Bleaching agents boosted with LED may improve the results of bleaching, but it is not essential to obtain good results.

Color inconstancy of natural teeth measured under white light-emitting diode illuminants

OBJECTIVE

To evaluate color and whiteness changes of natural teeth under nine white LED illuminants recently proposed by CIE.

METHODS

From spectral reflectance factors of 36 caries-free upper central incisors, corresponding colors under illuminant D65 and CIE 1931 standard colorimetric observer were computed for all tested illuminants, using the chromatic adaptation transform CAT16. Color differences (CIELAB and CIEDE2000 units) and whiteness (WI_D and WI_O indices) from teeth illuminated by CIE standard illuminants (D65 and A) and white LED illuminants were calculated. The appearance of 630 pairs of teeth under all illuminants was also evaluated.

RESULTS

Color gamuts from 36 teeth under tested illuminants showed similar volume and shape in CIELAB color space, but their centers of gravity changed in many different directions with respect to colors under D65 or A illuminants: Considering colors under D65/A, color shifts produced by white LED illuminants were in the ranges 2.0-8.6/1.1-7.0 CIELAB units (1.4-8.2/0.6-6.8 CIEDE2000 units). Average WI_D and WI_O values for the 36 teeth under different illuminants ranged from -5.8 to +19.3 and from -7.7 to +11.1, respectively. Considering 630 pairs of teeth, average color differences (mainly lightness differences) were below 0.5 CIELAB units (0.3 CIEDE2000 units), and average whiteness differences ranged from 8.1 to 10.7 for WI_D (23.4-25.1 for WI_O).

SIGNIFICANCE

Using CIE LED illuminants, most changes in color and whiteness for individual teeth were above typical threshold values of perceptibility and acceptability in dentistry. However, considering pairs of teeth, the average color and whiteness differences under all tested illuminants were very similar.

The change of teeth color, whiteness variations and its psychosocial and self-perception effects when using low vs. high concentration bleaching gels: a one-year follow-up

Background

Dental bleaching in traditional concentrations generates greater sensitivity. In this respect, new systems of lower concentration of hydrogen peroxide for tooth bleaching appeared, with color stability unknown over time. The aim of this study was to compare the change and stability of color with low-concentration (6%) hydrogen peroxide gel in an in-office bleaching setting relative to conventional 37.5% gel, including their effects on psychosocial and esthetic self-perception, after 1 year.

Methods

Patients (n = 25) were assessed at 12 months post bleaching treatment (whitening with 6% chemo-activated alkaline formula gel versus 37.5% traditional concentration gel). Color changes were measured objectively using total variation in color (ΔE), and subjectively using Vita Classical and Vita Bleached scale (ΔSGU) by calibrated evaluators (Kappa = 0.85). The Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ) and Oral Health Impact Profile (OHIP-14) aesthetic questionnaires were used to measure the self-perception and the psychosocial impact of the bleaching protocols.

Results

The effect (ΔE) of 37.5% HP (8.37 ± 2.73) was significantly better than that of 6% HP (5.27 ± 2.53) in terms of color rebound after 1 year of follow-up. There were significant differences in psychosocial impact and esthetic self-perception measurements prior to bleaching versus one-year post-whitening time points; positive effects were maintained.

Conclusions

Low concentration (6%) achieved effective bleaching with good stability after 1 year, accompanied by a positive psychosocial impact and enhanced self-perception at follow-up.

Trial registration

NCT03217994 (before enrollment of the first participant). Data register: July 14, 2017.

Influence of Bleaching and Aging Procedures on Color and Whiteness of Dental Composites

Bleaching can cause perceptible color changes on resin-based composite (RBC) restorations that may not be stable with aging. The objective of this study was to evaluate color stability and whiteness variations of RBCs after bleaching and aging procedures. Discs (10 mm in diameter and 1 mm thick) of shades A2 and A3 were fabricated from two RBCs (Filtek Z250 and Filtek Z350 XT) and divided into three subgroups (for each composite and shade) (n=5) as follows: control (no bleaching), at-home bleaching, and in-office bleaching. All specimens underwent an accelerated artificial aging up to 450 KJ/m2 and 900 KJ/m2 in an aging chamber (Suntest XXL+). A spectroradiometer (SpectraScan PR-670) was used to obtain CIE L*a*b* coordinates. CIEDE2000 color difference (ΔE00) and whiteness index for dentistry (WID) were used to evaluate color stability. Color and whiteness differences data were analyzed considering the 50:50% visual color difference thresholds (perceptibility [PT] and acceptability [AT]) and 50:50% whiteness thresholds (whiteness perceptibility [WPT] and whiteness acceptability [WAT]). Analysis of variance and Tukey tests (α=0.05) were used to statistically analyze the data. After bleaching, all specimens showed ΔE00 and ΔWID values below their corresponding acceptability thresholds (AT and WAT, respectively). After aging, L* and WID values decreased while b* values increased (p≤0.05), resulting in ΔE00 and ΔWID values above AT and WAT, respectively. Color changes after bleaching RBCs were clinically acceptable, while aging provoked clinically perceptible color changes.

Tooth color and whitening - digital technologies

OBJECTIVES

To review the key concepts of color in the dental domain with specific reference to the use of digital technology to measure color and color appearance.

MATERIALS AND METHODS

The literature on color assessment in dentistry is considered and methods for assessing whiteness, yellowness and color appearance are collated and described.

RESULTS AND CONCLUSION

A variety of methods for assessing color have been shown to exist and be viable including digital imaging. Equations to predict whiteness are identified; there is evidence that they are effective but further evaluation may be needed.

Recent Advances in Color and Whiteness Evaluations in Dentistry

Background:

The final goal of color measurement or shade specification in dentistry is the reproduction by prosthetic materials of all important appearance characteristics of natural oral structures. The application of color science in dentistry is an objective way to measure and evaluate such structures and dental materials in clinical practice and dental research.

Methods:

Literature on color science was reviewed to present new metrics to evaluate color differences of dental materials and dental structures. Visual acceptability and perceptibility values of color differences are reviewed and new whiteness indexes to describe whiteness in dentistry are presented.

Results:

In the last decade, the CIELAB 50:50% perceptibility and acceptability thresholds were set to 1.2 and 2.7, respectively, and the CIEDE2000 50:50% perceptibility and acceptability thresholds were set to 0.8 and 1.8. The CIEDE2000 color-difference formula became increasingly popular in dentistry. Developments in color science have led to the description of tooth whiteness and changes in tooth whiteness based on whiteness indexes, with the most relevant being the WID whiteness index, which is a customized index based in CIELAB color space.

Conclusion:

The application of color science in dentistry has allowed the precise description of tooth color and whiteness. The revised and new CIEDE2000 color-difference formula is expected to fully replace the outdated CIELAB formula in almost all dental applications. Recent psychophysical studies have reported values of visual thresholds and new whiteness indexes, which can serve as quality control tools to guide the selection of esthetic dental materials, evaluate clinical performance, and interpret visual and instrumental findings in clinical dentistry, dental research, and subsequent standardization.

Whiteness difference thresholds in dentistry

OBJECTIVE

To determine the visual whiteness thresholds for esthetic dentistry using the whiteness index for dentistry based on CIELAB color space (WI_D).

METHODS

A total of 60 observers (Dentists and Laypersons; n=30) from three research sites participated in the study. A psychophysical experiment based on visual assessments of simulated images of teeth on a calibrated display was performed. Images of simulated upper central incisors (SUCI) were consecutively displayed in pairs (60) and the whiteness of each SUCI pair was compared. WI_D was used to calculate the visual thresholds (WPT- perceptibility threshold; and WAT- acceptability threshold) with 95% confidence intervals (CI) and a Takagi-Sugeno-Kang (TSK) Fuzzy Approximation model was used as fitting procedure. Data was statistical analyzed using paired t-test (α=0.05).

RESULTS

WPT and WAT were 0.72 (CI: 0.0-2.69; r²=0.52) and 2.62 (CI: 0.2-7+; r²=0.57) WI_D units, respectively. Significant differences (p<0.05) were found between WPT and WAT, and between dentist (WPT=0.46WI_D units; WAT=2.20 WI_D units) and layperson (WPT=0.94 WI_D units; WAT=2.95 WI_D units).

SIGNIFICANCE

The visual whiteness difference thresholds determined with WI_D index can serve as reference values for research and manufacturing of dental materials, and for clinical practice situations such as assessing the effectiveness of bleaching treatments.

Investigation of the perceptual thresholds of tooth whiteness

OBJECTIVE

To investigate the tooth whiteness perceptibility thresholds of the average observer to changes in the CIELAB values and an optimised whiteness Index for dentistry (WIO) based on psychophysical studies.

METHODS

A psychophysical experiment based on visual assessments of digital images of teeth on a calibrated display with a group of observers (n=32) has been conducted to determine the perceptual thresholds in tooth whiteness. Digital simulations of a tooth that is identical in shape to the left incisor in the image of teeth were superimposed on to images. The colour of the simulated tooth was varied and observers were asked to respond whether there was a difference in whiteness between the left incisor and the simulated tooth. Thresholds for detection of differences in whiteness were independently determined in four conditions: ΔL*, Δa*, Δb* and a blue optical whitening direction. Raw data were fitted using a non-parametric approach and thresholds of CIELAB and WIO for each conditions were calculated.

RESULTS

Estimates of the threshold of the four conditions of ΔL*, Δa*, Δb* and a blue covarine optical tooth whitening direction were 1.14, 3.24, 1.11 and 1.51 respectively, with the corresponding WIO thresholds of 2.77, 6.52, 3.09 and 1.99 respectively.

CONCLUSIONS

The thresholds for tooth whiteness perception in CIELAB space and WIO space were determined. The findings demonstrate that for a whitening treatment with a blue covarine optical technology, a colour change of about 2 WIO units would be noticeable.

CLINICAL SIGNIFICANCE

This study gives a better understanding of the tooth whiteness perception threshold, and will help clinicians identify perceivable differences in tooth colour during matching and whitening procedures.

Evaluation of chromatic changes of a nanocomposite resin using the new whitness index

Background and aims

To evaluate the staining effects of two brands of coffee and the bleaching efficiency of two in-office bleaching methods, upon different opacities of a commercial nanocomposite.

Methods

Twenty four specimens of each opacity, A3 Dentin, A3 Body and A3 Enamel, were fabricated from Filtek Supreme (3MEspe). The specimens were further divided into two groups (n=12) and were immersed in two coffee solutions (Bio Organic Coffee Bellarom, 100% Arabica, and Iulius Meinl Coffee), for 24 hours. Between the staining sessions, the specimens were stored in sterile water, at 37°C. Each group was further divided into three (n=4), in order to be bleached, as follows: Group 1 - Beyond 35% in office, for 4 applications of 15 minutes each, Group 2 – Zoom Day White 6% in office, for 4 applications of 15 minutes each, Group 3 – Control Group, stored in sterile water. Color values were measured with a dental spectrophotometer Vita EasyShade 4.0 and five measurements were recorded for each sample at a time. Lightness L*, color coordinates a* and b* were recorded, at baseline, after staining in coffee and after bleaching. Whiteness index (WID) of the three composite resins (A3D, A3B, A3E) in the three moments were calculated, as well as the color difference Delta E* correspondent to the staining and bleaching process. Data were analyzed using one-way repeated measures ANOVA and the WID index was calculated WID (p<0.05). Univariate analysis of variance was performed for assessing the influence of staining solution upon composite resins, as well as for testing the effect of bleaching agents. The significance level was set at α=0.05 and pairwise comparisons were adjusted by the Least Significant Difference method.

Results

The pairwise comparisons showed no significant difference between the effects of the two bleaching agents upon the WID, meaning that they induce almost similar color changes. The results of the univariate ANOVA test indicated a significant effect of the composite resin and the staining solution upon the WID (p<0.05). However, no significant interaction effect was found between the composite resin and the staining solution (p=0.095). There was a significant difference in the staining effect of the two coffee solutions only for A3B and A3E composite resins (p<0.05).

Conclusions

The chromatic changes of the nanocomposite resin could be evaluated by the variation of the whiteness index. The staining effect induced by the two types of coffee was similar. The most effective protocol was the in-office bleaching method based on Beyond 35%.

The in vitro and in vivo reproducibility of a video-based digital imaging system for tooth colour measurement

OBJECTIVES

To assess the robustness of a new custom built video-based digital imaging system (VDIS) for measuring tooth colour and whiteness under in vitro and in vivo conditions.

METHODS

The VDIS imaging system was developed for tooth colour measurement and evaluated in vitro and in vivo. The in vitro validation used extracted human teeth (HT, n=14) stored in water and VITA Classical shade guide tabs (SG, n=16). These were measured by the VDIS at baseline, 5min, 2h, 1 week and 2 weeks to evaluate the system repeatability. For in vivo validation, adult volunteers (male/female, n=34) with two natural, unrestored central incisors had their teeth imaged using the VDIS at baseline, 5min and 2h (3 images each) by two different operators to evaluate time and operator effects. Between taking individual images, subjects moved from the imaging-frame to assess the effect of re-positioning on reproducibility. From the in vitro and in vivo images, the average tooth RGB values were obtained, and the CIELAB values and a tooth whiteness index WIO value were calculated. Repeatability and reproducibility of VDIS imaging system was assessed using appropriate repeated measurement analysis techniques and ANOVA.

RESULTS

The measurement variations in vitro were between 1 and 2 units of ΔWIO and the average colour differences were less than 1 ΔE^*_ab unit. For the in vivo study, analysis of the CIELAB parameters and WIO showed that subject variability accounted for between 82 and 99% of the observed variability in the measurement process. The operator variability was less than 0.5% and the overall measurement error was found to be only 0.3% for WIO. Across assessment times the variability was less than 0.5%.

CONCLUSIONS

The dental imaging system V-DIS was shown to be a highly reproducible means for tooth colour and whiteness measurement.

CLINICAL SIGNIFICANCE

Digital imaging based techniques gives a highly reproducible approach to measuring tooth colour.

Tooth colour and whiteness: A review

OBJECTIVES

To review current knowledge concerning the application of colour science on tooth colour and whiteness description, measurement, distribution and its psychological impact.

DATA SOURCES

"Scopus" databases were searched electronically with the principal keywords tooth, teeth, colour, white, whiteness. Language was restricted to English and original studies and reviews were included. Conference papers and abstracts were excluded.

CONCLUSIONS

The appearance and colour of teeth are a common concern for patients across many populations and are associated with an increased desire for treatments that improve dental aesthetics, including tooth whitening. The application of colour science in dentistry has allowed the precise description of tooth colour and whiteness. Coupled with the advances in instrumental tooth colour measurement, such as spectrophotometers, colorimeters, spectroradiometers and digital imaging systems, these parameters are quantifiable in a reproducible and robust manner. These principles have been applied to the tooth colour distribution in many study populations, indicating, in general, differences in tooth colour for subject age and gender, but not for ethnicity. Psychophysical studies on tooth colour and whiteness via third party assessment of images indicate that whitened teeth lead to judgements that are more positive on personality traits such as social competence and appeal, intellectual ability and relationship satisfaction.

Aesthetically improved and efficient tannin–metal chelates for the treatment of dentinal hypersensitivity

Tannin–metal chelates for the efficient nucleation of hydroxyapatite and an aesthetically improved solution for the dentinal hypersensitivity treatment.

Optical Dental Whitening Efficacy of Blue Covarine Toothpaste in Teeth Stained by Different Colors

OBJECTIVE

Evaluate the immediate and cumulative optical whitening efficacy of a blue covarine toothpaste.

MATERIALS AND METHODS

180 bovine tooth specimens with similar shade (ΔE < 3.5) were staining of different beverage: black tea(BT), green tea (GT), red wine (RW), orange soda (OS), and brazilian açai juice (AJ), and then submitted to tooth brushing with a blue covarine toothpaste (Op) or a control abrasive toothpaste (Ab). The whitening effect was evaluated at baseline (B), after staining (S), after 1 day (1D) and 7 days of cumulative use of toothpastes (7D). The color shade chances were assessment by Vita Easyshade reflectance spectroscope and the data of CIELab color coordinates (L*, a*, and b*), color difference (ΔE) and the whiteness index optimized (WIO), were analyzed by two-way mixed analysis of variance (ANOVA) for repeated measures and Bonferroni-corrected t-tests (α = 0.05).

RESULTS

The analysis showed statistically significant differences before and after staining by colored beverages (p < 0.05), but no differences were found due to the action of toothpaste (p > 0.05), in the CIELab coordinates, ΔE and WIO index.

CONCLUSIONS

The use of toothpastes (Op or Ab) reduced the dental staining caused by different colored beverage, but the whitening effect of blue covarine toothpaste could not be confirmed (p > 0.05).

Enamel Surface Changes After Exposure to Bleaching Gels Containing Carbamide Peroxide or Hydrogen Peroxide

OBJECTIVE

This study evaluated the differences in enamel color change, surface hardness, elastic modulus, and surface roughness between treatments with four bleaching gels containing carbamide peroxide (two at 10% and one each at 35%, and 45%) and two bleaching gels containing hydrogen peroxide (two at 40%).

METHODS

Enamel specimens were bleached and color changes were measured. Color change was calculated using either ΔE or the Bleaching Index (BI). Then, surface hardness, elastic modulus, and surface roughness of the enamel specimens were evaluated. All measurements were performed at baseline and directly after the first bleaching treatment for all carbamide peroxide- and hydrogen peroxide-containing bleaching gels. In addition, final measurements were made 24 hours after each of a total of 10 bleaching treatments for carbamide peroxide bleaching gels, and 1 week after each of a total of three bleaching treatments for hydrogen peroxide bleaching gels.

RESULTS

After the last bleaching treatment, respective ΔE scores were 17.6 and 8.2 for the two 10% carbamide peroxide gels, 12.9 and 5.6 for the 45% and 35% carbamide peroxide gels, and 9.6 and 13.9 for the two 40% hydrogen peroxide gels. The respective BI scores were -2.0 and -2.0 for the two 10% carbamide peroxide gels, -3.5 and -1.5 for the 45% and 35% carbamide peroxide gels, and -2.0 and -3.0 for the two 40% hydrogen peroxide gels. Each bleaching gel treatment resulted in significant whitening; however, no significant difference was found among the gels after the last bleaching. Whitening occurred within the first bleaching treatments and did not increase significantly during the remaining treatments. Surface hardness significantly decreased after the last bleaching treatment, when 10% carbamide peroxide was used. Furthermore, significant changes in the elastic modulus or surface roughness occurred only after treatment with 10% carbamide peroxide.

CONCLUSION

All six bleaching gels effectively bleached the enamel specimens independent of their concentration of peroxide. Gels with low peroxide concentration and longer contact time negatively affected the enamel surface.

Quantitative light fluorescence (QLF) and polarized white light (PWL) assessments of dental fluorosis in an epidemiological setting

Background

To determine if a novel dual camera imaging system employing both polarized white light (PWL) and quantitative light induced fluorescence imaging (QLF) is appropriate for measuring enamel fluorosis in an epidemiological setting. The use of remote and objective scoring systems is of importance in fluorosis assessments due to the potential risk of examiner bias using clinical methods.

Methods

Subjects were recruited from a panel previously characterized for fluorosis and caries to ensure a range of fluorosis presentation. A total of 164 children, aged 11 years (±1.3) participated following consent. Each child was examined using the novel imaging system, a traditional digital SLR camera, and clinically using the Dean’s and Thylstrup and Fejerskov (TF) Indices on the upper central and lateral incisors. Polarized white light and SLR images were scored for both Dean’s and TF indices by raters and fluorescence images were automatically scored using software.

Results

Data from 164 children were available with a good distribution of fluorosis severity. The automated software analysis of QLF images demonstrated significant correlations with the clinical examinations for both Dean’s and TF index. Agreement (measured by weighted Kappa’s) between examiners scoring clinically, from polarized photographs and from SLR images ranged from 0.56 to 0.92.

Conclusions

The study suggests that the use of a digital imaging system to capture images for either automated software analysis, or remote assessment by raters is suitable for epidemiological work. The use of recorded images enables study archiving, assessment by multiple examiners, remote assessment and objectivity due to the blinding of subject status.

Influence of surface roughness on the color of dental-resin composites

This study deals with the influence of surface roughness on the color of resin composites. Ten resin composites (microfilled, hybrid, and microhybrid) were each polished with 500-grit, 1200-grit, 2000-grit, and 4000-grit SiC papers. The roughness parameter (R(a)) was measured using a Plμ confocal microscope, and field-emission scanning electron microscope (Fe-SEM) images were used to investigate filler morphology. Color was measured using a spectroradiometer and a D65 standard illuminant (geometry diffuse/0° specular component excluded (SCE) mode). Surface roughness decreased with grit number and was not influenced by filler size or size distribution. A significant influence of R(a) on lightness (L*) was found. Lightness increased with decreases in roughness, except for specimens that underwent polishing procedure 4 (PP4; 500-grit, 1200-grit, 2000-grit, and 4000-grit SiC papers consecutively). Generally, it was found that surface roughness influenced the color of resin composites. The composites that underwent PP1 (500-grit SiC paper) exhibited significant differences in chroma (C*), hue (h°), and lightness (L*) compared to composites that underwent PP3 (500-grit, 1200-grit, and 2000-grit SiC papers consecutively) and PP4. Color difference (∆E*) between the polishing procedures was within acceptability thresholds in dentistry.

Color appearance models and complex visual stimuli

OBJECTIVES

Teeth in a patient's mouth in a dental office, or in the natural environment, represent very complex stimuli for the human color vision system. Predicting their perceived color is a daunting task at best. Colorimetry is designed mainly for the evaluation of uniform, flat, opaque, materials of fairly large size viewed on a medium-grey background under near-daylight sources of fairly high luminance. On the contrary, in situ teeth vary spatially, are curved and ridged, translucent, relatively small, and viewed against a variable background under nonuniform, and typically nonstandard, illumination. These differences in stimuli and viewing conditions summarize the difficulty in predicting the color appearance of teeth.

SOURCES

The field of color science has extended basic colorimetry, as represented by CIE XYZ and CIELAB coordinates, to more complex visual stimuli and viewing environments. The CIECAM02 color appearance model accurately addresses issues of chromatic adaptation, luminance effects and adaptation, background and surround effects, and the higher dimensionality of color appearance. Such models represent a significant advance and are used successfully in a variety of applications. However, many stimuli vary in space and time at scales not addressed by typical color appearance models. For example, high-definition video images would fall into such a category and so would in situ human teeth. More recently, color appearance models and image quality metrics have been combined to create image appearance models for even more complex visual stimuli.

CONCLUSIONS

This paper provides an overview of fundamental and advanced colorimetry leading up to color appearance and image appearance models and their potential application in dentistry.