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.

European Organization for Caries Research Workshop: Methodology for Determination of Potentially Available Fluoride in Toothpastes.

Toothpastes are the most universally accepted form of fluoride delivery for caries prevention. To provide anti-caries benefits, they must be able to release fluoride during the time of tooth brushing or post brushing into the oral cavity. However, there is no standard accepted procedure to measure how much fluoride in a toothpaste may be (bio) available for release. The European Organization for Caries Research proposed and supported a workshop with experts in fluoride analysis in toothpastes and representatives from industry. The objective of the workshop was to discuss issues surrounding fluoride analysis in toothpaste and reach consensus on terminology and best practices, wherever the available evidence allowed it. Participants received a background paper and heard presentations followed by structured discussion to define the problem. The group also reviewed evidence on the validity, reliability and feasibility of each technique (namely chromatography and fluoride electroanalysis) and discussed their strengths and limitations. Participants were able to reach a consensus on terminology and were also able to identify and summarize the advantages and disadvantages of each technique. However, they agreed that most currently available methods were developed for regulatory agencies several decades ago, utilizing the best available data from clinical trials then, but require to be updated. They also agreed that although significant advances to our understanding of the mechanism of action of fluoride in toothpaste have been achieved over the past 4 decades, this clearly is an extraordinarily complex subject and more work remains to be done.

The impact of priming on dentally induced social judgements: An experimental study.

OBJECTIVE: To ascertain the effects of priming to consider tooth appearance (i.e. exposure to a 'tooth whitening television advert') versus control (a 'non-dental' television advert) on social judgements of tooth colour in a group of Caucasians. METHODS: Two groups of Caucasians randomly assigned to watch either a tooth-whitening advert (experimental, N = 67) or a bread advert (control, N = 62). All rated the measures of social perceptions: friendliness, popularity, social life, success, intelligence, graduation, introversion/extroversion, happiness, self-confidence, attractiveness, age-estimation and satisfaction, after watching either of the adverts and viewing three digitally modified photographs (Darkened, natural and whitened teeth) of different Caucasian adults (males and females) separately. RESULTS: There were no statistically significant differences for all the measures of social perception between the groups. Nevertheless, the questions that inquired about popularity, friendliness, success, intelligence, happiness, self-confidence, attractiveness and satisfaction were consistently rated higher for all three tooth shades in the experimental than the control groups. Further, within the experimental and control groups, higher ratings were given to the faces with whitened teeth than the natural and darkened teeth. CONCLUSIONS: Priming has little impact on dentally induced social judgements as this study failed to demonstrate statistically significant differences. Nevertheless, both groups gave the highest subjective ratings for the faces with whitened teeth and the tooth-whitening advert group associated the faces in the photographs with higher subjective ratings than the non-dental advert group irrespective of the tooth shade. One reason for this could be the way media affects the psychological well-being. CLINICAL SIGNIFICANCE STATEMENT: The almost universal exposure to idealised tooth appearance in the media may increase demand for aesthetic treatments. Standardising the colour of the tooth plays a huge impact and making individuals to view a tooth whitening advert just prior to a procedure might influence patient choices.

Protective effect of calcium silicate toothpaste on enamel erosion and abrasion in vitro.

OBJECTIVES: To compare in vitro the effect of a toothpaste containing fluoride (F), calcium silicate (CaSi) and sodium phosphate salts to conventional toothpaste (NaF) on human enamel specimens submitted to erosive and abrasive challenges. METHODS: 48 sound and 48 enamel samples pre-treated with 1% citric acid were divided into 4 groups (n = 12): Group 1- Non-fluoride toothpaste; Group 2- NaF toothpaste (1450 ppmF); Group 3- CaSi toothpaste (1450 ppmF; MFP); Group 4- Erosion only. The samples were subjected to pH cycling (3 cycles/day; 90s; 1% citric acid, pH 3.6) and to abrasion for 7 days. After the 1st and the last cycle, they were submitted to abrasion (15s, 1.5N load), using a brushing machine, soft toothbrush and toothpaste slurry (1:3; 15ml/sample) and then immersed in the slurry for 45s. Samples were immersed in artificial saliva between the challenges. Enamel loss was evaluated using profilometry on days 3 and 7. Data were analysed by ANOVA and Tukey's test (p < 0.05). RESULTS: For sound enamel at baseline, mean (±SD) enamel loss (µm) for groups 1-4 on day 3 was 2.15 ± 0.35a, 1.20 ± 0.22b, 0.95 ± 0.19b and 1.98 ± 0.32a; on day 7 was 3.05 ± 0.40a, 2.07 ± 0.32b, 1.36 ± 0.33c and 3.69 ± 0.27d respectively. For acid-softened enamel at baseline, enamel loss on day 3 was 3.16 ± 0.19a, 2.17 ± 0.14b, 1.70 ± 0.11c and 3.04 ± 0.19a; on day 7 was 3.92 ± 0.25a, 3.07 ± 0.13b, 2.09 ± 0.15c and 3.87 ± 0.25a respectively. CONCLUSIONS: Both F toothpastes led to significantly higher enamel protection from short-term erosion and abrasion in comparison to the non-F toothpaste and erosion only. In the longer term, CaSi toothpaste conferred significantly higher protection than NaF toothpaste. CLINICAL SIGNIFICANCE: The results showed that for the longer term the CaSi toothpaste provided significantly higher protection than the NaF toothpaste, which indicates a good potential of the former to help prevent erosive tooth wear.

In vitro dentine tubule occlusion by a novel toothpaste containing calcium silicate and sodium phosphate.

OBJECTIVES: To investigate the deposition, formation of hydroxyapatite (HAP) and acid resistance of dentine surfaces following brushing with a toothpaste containing calcium silicate and sodium phosphate (CSSP) and fluoride in vitro. METHODS: Human dentine specimens were brushed with a slurry of CSSP toothpaste followed by exposure to simulated oral fluid (SOF) in two in vitro studies, with a silica-based non-occluding toothpaste as control. The surface and tubule deposits were analysed after 14 cycles with scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). In a third study, dentine specimens were additionally exposed to citric acid erosive challenges for 30, 300 or 600 s after 2, 6, 10 and 14 cycles of SOF and either the CSSP toothpaste or a positive control toothpaste containing calcium sodium phosphosilicate and fluoride. The level of tubule occlusion was evaluated using SEM. RESULTS: The SEM analyses indicated complete coverage of the dentine surface following 14 cycles of brushing with CSSP toothpaste with no observable patent tubules, in contrast to the non-occluding control toothpaste. The TEM and SAED analyses confirmed the deposited material on the surface and within tubules was HAP. The deposited material from CSSP toothpaste was more acid resistant than the deposited material from the positive control toothpaste at all time points and acid exposure levels (p < 0.05). CONCLUSIONS: The CSSP toothpaste fully occluded dentine tubules and formed the mineral HAP. The dentine deposition on and within dentine tubules was resilient to acid erosive challenges. CLINICAL SIGNIFICANCE: A novel toothpaste containing CSSP can form HAP on dentine surfaces and within tubules. The potential of this technology is for a novel approach for the protection of dentine surfaces to acid challenges and the reduction of dentine hypersensitivity.

A silica toothpaste containing blue covarine: a new technological breakthrough in whitening.

There continues to be a demand from consumers and patients for products that whiten teeth. These products are generally either peroxide-based bleaching formats to improve intrinsic tooth colour or whitening toothpastes with enhanced physical and chemical cleaning properties to remove and prevent extrinsic tooth stain. Through the understanding of colour science and its application to tooth colour a new approach to tooth whitening is now possible from toothpaste. This is achieved by the deposition of blue covarine onto the tooth surface where it changes the optical properties of the teeth such that their appearance is both measurably and perceivably whiter immediately after treatment. In vitro and in vivo studies confirm the efficacy of this whitening approach in a silica based whitening toothpaste containing blue covarine. In addition, this toothpaste has been shown not to have an undue degree of abrasivity to enamel or dentine compared to other relevant commercially available products, and is an efficacious source of fluoride.

Detection threshold of non-contacting laser profilometry and influence of thermal variation on characterisation of early surface form and textural changes in natural human enamel.

OBJECTIVES: To determine the detection threshold of non-contacting laser profilometry (NCLP) measuring surface form and surface roughness change in natural human enamel in vitro, characterise how ambient scanning thermal variation affects NCLP measurement, and calculate bulk enamel loss in natural human enamel. METHODS: NCLP repeatability and reproducibility accuracy was determined by consecutively scanning natural human enamel samples with/without sample repositioning. Ambient thermal variation and NCLP sensor displacement over short (30 s), medium (20 min), and long (2 h) scanning periods were evaluated for their standard deviation. Natural human enamel specimens (n = 12) were eroded using citric acid (0.3% w/w pH3.2) for 5, 10, and 15 min and characterised using surface profilometry, tandem scanning confocal microscopy (TSM), and optical coherence tomography (OCT). RESULTS: Repeatability and reproducibility error of NCLP for surface form was 0.28 µm and 0.43 µm, and for surface roughness 0.07 µm and 0.08 µm. Ambient thermal variation resulted in NCLP sensor displacement of 0.56 µm and 1.05 µm over medium and long scanning periods. Wear scar depth (µm) was calculated between 0.72-1.61 at 5 min, 1.72-3.06 at 10 min, and 3.40-7.06 at 15 min. Mean (SD) surface roughness (µm) was 1.13 (0.13), 1.52 (0.23), 1.44 (0.19), and 1.43 (0.21) at baseline, 5, 10, and 15 min. Qualitative image analysis indicated erosive change at the surface level, progressing after increasing erosion time. SIGNIFICANCE: Minimum detectable limits for NCLP measuring surface form and surface roughness changes were characterised. Ambient thermal variation, subsequent sensor displacement, and its impact on NCLP performance were characterised. Dental erosion lesions in natural human enamel could be characterised using surface profilometry, surface roughness, OCT, and TSM. Step height formation could be calculated within NCLP and temperature operating limits using profile superimposition and profile subtraction techniques. Natural enamel samples can now be used in in-vitro studies to investigate the formation and development of early acid erosive tooth wear, as well as the assessment of methods for enamel lesion remineralisation and repair.

A review of tooth colour and whiteness.

OBJECTIVES: To review current knowledge on the definition of tooth whiteness and its application within dentistry, together with the measured range of tooth colours. METHODS: 'Medline' and 'ISI Web of Sciences' databases were searched electronically with key words tooth, teeth, colour, colour, white and whiteness. CONCLUSIONS: The application of colour science within dentistry has permitted the measurement of tooth colour in an objective way, with the most common colour space in current use being the CIELAB (Commission Internationale de l'Eclairage). Indeed, many investigators from a range of different countries have reported L*, a* and b* values for teeth measured in vivo using instrumental techniques such as spectrophotometers, colorimeters and image analysis of digital images. In general, these studies show a large range in L*, a* and b* values, but consistently show that there is a significant contribution of b* value or yellowness in natural tooth colour. Further developments in colour science have lead to the description of tooth whiteness and changes in tooth whiteness based on whiteness indices, with the most relevant and applicable being the WIO whiteness index, a modified version of the CIE whiteness index.

A novel optical approach to achieving tooth whitening.

OBJECTIVE: To investigate a new optical approach to tooth whitening by enhancing the measurement and perception of tooth whiteness using blue coloured materials deposited onto the tooth surface. METHODS: Salivary pellicle coated human extracted teeth or polished enamel specimens were used as substrates and their colour was measured using a colorimeter in the CIELAB mode. Whole teeth were treated with a range of blue dyes and pigments and the colour measured following rinsing with water. Whole teeth were treated with Blue Covarine for 30 s, rinsed with water and colour changes assessed via colorimetric and visual assessment with a Vita Shade guide under controlled lighting (D65). Deposition of Blue Covarine onto cut enamel specimens was investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Tooth colour changes were also investigated following brushing for 1 min with toothpaste formulations containing Blue Covarine. RESULTS: Blue Covarine gave a significantly greater deltab* shift (p < 0.0001) compared to water. Blue Covarine gave a mean Vita Shade change of 1.18 compared to the water control (-0.03) (p <0.0001) and an increase in objectively measured whiteness index (WIO) (p <0.0001). Blue Covarine was chemically detected on enamel surfaces using TOF-SIMS. Toothpaste formulations containing Blue Covarine gave improvements in tooth whiteness. CONCLUSIONS: Blue Covarine has been identified as a new approach to tooth whitening. Its mode of action involves deposition and retention on tooth surfaces where it alters the optical properties of the tooth. This gives rise to an increase in the overall measurement and perception of tooth whiteness.

In vitro cleaning, abrasion and fluoride efficacy of a new silica based whitening toothpaste containing blue covarine.

OBJECTIVES: To investigate the stain removal ability, abrasivity towards enamel and dentine, and fluoride efficacy of a new silica based blue covarine whitening toothpaste in vitro. METHODS: Stain removal was assessed by brushing artificially stained bovine specimens with slurries of either the new toothpaste or one of two whitening products or a non-whitening silica product. Toothpaste abrasivity was assessed by brushing enamel/dentine specimens with slurries of either the new toothpaste, a whitening toothpaste or a non-whitening toothpaste and measuring the wear via a combination of changes in geometry of Knoop indents and surface profilometry. Fluoride efficacy was assessed using remineralisation, demineralisation and fluoride-uptake methods. RESULTS: The in vitro cleaning study showed that the silica based blue covarine whitening toothpaste removed significantly (p < 0.05) more stain than the non-whitening toothpaste and was as effective as the two marketed silica based whitening toothpastes. This enhanced tooth whitening benefit did not give rise to a concomitant statistically significant increase in the level of wear to enamel and dentine compared to the non-whitening silica based toothpaste. The fluoride efficacy was superior to a non-fluoridated control and was as effective as a clinically tested formulation containing the same fluoride source. CONCLUSIONS: The studies show that the new whitening toothpaste is effective in extrinsic stain removal, does not have an undue degree of abrasivity to enamel or dentine compared to other relevant commercially available products, and is an efficacious source of fluoride.

The protective nature of pellicle towards toothpaste abrasion on enamel and dentine.

OBJECTIVES: To determine the protective nature of pellicle towards toothpaste abrasion. METHODS: The enamel region of human enamel-dentine blocks was indented with a Knoop diamond and the profile across the enamel-dentine junction was measured. Blocks were either exposed to deionised water or placed onto intra-oral appliances and worn in the mouth to produce in situ pellicles. This was followed by a 10-day period of tooth brushing experiments. Each day, specimens were brushed with a slurry of either Toothpaste A (RDA=90) or Toothpaste B (RDA=204) for 25 cycles (10s) on a brushing machine. This was repeated three times per day for a total of 750 brushing cycles. Between brushing cycles specimens were returned to water or in situ. The geometry of the Knoop indents and the enamel-dentine profile were re-measured and the enamel and dentine wear calculated. Specimens were also prepared for TEM analyses. RESULTS: The mean enamel wear (microm) for Toothpastes A and B (water) was 0.23 and 0.06, and for Toothpastes A and B (in situ) was 0.03 and 0.08, respectively. The mean dentine wear (microm) for Toothpastes A and B (water) was 5.08 and 6.03, and for Toothpastes A and B (in situ) was 1.94 and 1.70, respectively. For Toothpaste A, the presence of in situ pellicle significantly (p<0.05) reduced enamel and dentine wear compared to water and for Toothpaste B, dentine wear was significantly reduced compared to water. After tooth brushing, residues of the in situ pellicle layer could be detected on enamel and dentine surfaces by TEM analysis. CONCLUSIONS: The study has demonstrated for the first time that the presence of pellicle can significantly reduce toothpaste abrasion.

Evaluation of a new silica whitening toothpaste containing blue covarine on the colour of anterior restoration materials in vitro.

OBJECTIVES: The aims of this study were to evaluate the effects of a novel silica-based blue covarine whitening toothpaste on the colour of anterior restoration materials. METHODS: Restoration materials (three glass ionomers, three resin composites) were cast into disks (10 mm diameter, 2 mm thick) using cylindrical moulds. Specimens were immersed in pooled whole saliva prior to exposure to staining materials via one of two protocols. CIELAB colour measurements were taken at baseline and after each stage of the procedures. In one protocol, specimens were brushed with 10 ml of 33% (w/w) silica whitening toothpaste containing blue covarine slurry in water four times, for 10 min each time, with control specimens being immersed in water or red wine for the same period. Disks were re-immersed in saliva for 2 h between cycles. In the other protocol, specimens were immersed in 20 ml of water, red wine or silica whitening toothpaste containing blue covarine slurry for 96 h with colour measurements being taken afterwards. The second protocol disks were then brushed for 2 min using a non-whitening silica paste and further colour measurements made. Colour differences were then calculated. RESULTS: At the end of both protocols the disks treated with silica whitening toothpaste containing blue covarine were not significantly different from the water controls (p > 0.1) in contrast to those treated with red wine. Even prior to brushing in the second protocol, there was no significant staining from the new toothpaste compared to the water control (p > 0.1). CONCLUSIONS: There was no significant staining by the silica whitening toothpaste containing blue covarine on any of these materials.

The in vitro and in vivo validation of a mobile non-contact camera-based digital imaging system for tooth colour measurement.

OBJECTIVE: To assess the reproducibility of a mobile non-contact camera-based digital imaging system (DIS) for measuring tooth colour under in vitro and in vivo conditions. METHODS: One in vitro and two in vivo studies were performed using a mobile non-contact camera-based digital imaging system. In vitro study: two operators used the DIS to image 10 dry tooth specimens in a randomised order on three occasions. In vivo study 1:25 subjects with two natural, normally aligned, upper central incisors had their teeth imaged using the DIS on four consecutive days by one operator to measure day-to-day variability. On one of the four test days, duplicate images were collected by three different operators to measure inter- and intra-operator variability. In vivo study 2:11 subjects with two natural, normally aligned, upper central incisors had their teeth imaged using the DIS twice daily over three days within the same week to assess day-to-day variability. Three operators collected images from subjects in a randomised order to measure inter- and intra-operator variability. RESULTS: Subject-to-subject variability was the largest source of variation within the data. Pairwise correlations and concordance coefficients were > 0.7 for each operator, demonstrating good precision and excellent operator agreement in each of the studies. Intraclass correlation coefficients (ICCs) for each operator indicate that day-to-day reliability was good to excellent, where all ICC's where > 0.75 for each operator. CONCLUSION: The mobile non-contact camera-based digital imaging system was shown to be a reproducible means of measuring tooth colour in both in vitro and in vivo experiments.

An interproximal model to determine the erosion-protective effect of calcium silicate, sodium phosphate, fluoride formulations.

OBJECTIVES: Previous work has shown the effectiveness of a newly developed interproximal model to differentiate between the amount of remineralization caused by toothpastes used with or without a dual-phase gel treatment system containing calcium silicate, sodium phosphate salts and fluoride to repair acid-softened enamel. The aim of this study was to utilize the same interproximal model to identify how effective calcium silicate phosphate toothpastes are at reducing surface softening in the early stages of erosion. The model was also used to identify the effect of increasing the frequency of acid exposure on the reduction in surface hardness. METHODS: Human enamel specimens were prepared and mounted in an interproximal face-to-face arrangement and exposed to a cycling regime of whole human saliva, treatment, artificial saliva and 1% citric acid pH 3.75. Specimens were measured by surface microhardness at baseline and after three and seven days. The frequency of acid exposure was increased from 2 to 4 cycles a day for the second part of the study. RESULTS: The results showed that specimens treated with the calcium silicate phosphate toothpastes softened less than those treated with control fluoridated or non-fluoride toothpastes at each time point and following an increase in the frequency of acid exposure. SIGNIFICANCE: This work has demonstrated how an interproximal model can also be successfully used to determine differences in the erosion protection of various treatments as well as determining how they perform when the frequency of acid exposure is increased.

Review of the effects of peroxide on enamel and dentine properties.

OBJECTIVES: To review the available literature investigating the effects of peroxide-based products and solutions on enamel and dentine properties. SOURCES: All original scientific full papers listed in ISI Web of Science and Medline were included in this review using the search terms peroxide AND (enamel OR dentin*) up to the end of 2006. CONCLUSIONS: The majority of studies indicate that peroxide containing products and solutions have no significant deleterious effects on enamel and dentine surface morphology and chemistry, surface microhardness, subsurface enamel and dentine microhardness or ultrastructure. In addition, in vitro studies indicate that they have no significant clinically relevant effects on subsequent enamel and dentine loss caused by acidic erosive challenges, toothpaste abrasion or caries lesion formation. The contrasting studies that do show an effect on some of the above properties, in general, have some limitations in the in vitro methods used which do not accurately reflect the in vivo situation or use products/solutions that have a particularly low pH where acidic erosive processes are likely to dominate and explain the observed changes in enamel and dentine.

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.

In vitro evaluation of a silica whitening toothpaste containing blue covarine on the colour of teeth containing anterior restoration materials.

OBJECTIVES: To investigate the effects of a silica-based whitening toothpaste containing blue covarine on the colour of restorations in extracted human teeth. METHODS: Human extracted teeth were mounted in acrylic resin. A cavity was cut into the enamel surface and the specimen restored with either glass ionomer or composite dental materials. Following 4 weeks storage in water, specimens were treated with either water, red wine or a toothpaste containing blue covarine (n=10) for 24h followed by brushing with a silica-based toothpaste. Specimens were imaged with a digital imaging system at baseline, after 24h treatment and after brushing with a silica-based toothpaste. CIELAB colour parameters were determined for the restoration and the whole specimen and overall mean colour changes calculated (ΔE). Baseline and post-brushing images were compared subjectively for overall stain and staining around the restoration margin. RESULTS: Red wine produced the largest ΔE values for whole specimens and for all restoration materials and the largest subjective stain scores for whole specimens and restoration margins. The red wine stain was not completely removed by brushing with a silica-based toothpaste. Comparisons of the red wine group with either the blue covarine toothpaste group or the water group were of statistical significance for all parameters (ANOVA, Tukey-Kramer, p<0.05). Following brushing with the silica-based toothpaste, specimens from the blue covarine toothpaste group were not significantly different (p>0.05) to the water group, for all restoration material types. CONCLUSIONS: Exaggerated treatment with a blue covarine containing toothpaste does not significantly affect the colour of the restoration or the restoration margin of the dental materials tested versus a water alone treatment. CLINICAL SIGNIFICANCE: The silica-based blue covarine containing toothpaste does not permanently stain the restorative materials tested or their margins.

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.

In vitro and clinical evaluation of optical tooth whitening toothpastes.

OBJECTIVES: To measure tooth whitening effects delivered immediately after brushing with silica-based toothpastes containing either blue covarine or a combination of blue covarine and FD&C Blue No. 1 in vitro and in vivo. METHODS: Salivary pellicle coated human extracted teeth were brushed with either a slurry of a toothpaste containing blue covarine (BC) or a formulation containing a matched level of blue covarine and FD&C Blue No.1 (BC+D). The colour of the specimens were measured in vitro using a colorimeter, before and after brushing and changes in CIELAB and tooth Whiteness Index (WIO) values calculated. In a double-blind cross-over clinical study, subjects brushed with BC toothpaste, a toothpaste containing increased levels of blue covarine (BC+) or BC+D toothpaste and tooth colour changes were measured with a digital image analysis system. RESULTS: The in vitro study demonstrated that BC+D gave a significantly (p=0.002) greater change in WIO value than BC. Clinical results showed that BC, BC+ and BC+D gave a significant increase in WIO (p<0.0001) from baseline. The WIO change was significantly greater when brushing with BC+D toothpaste than with either toothpaste BC (p<0.0001) or BC+ (p<0.05). CONCLUSIONS: Toothpastes containing blue covarine or a combination of blue covarine and FD&C Blue No. 1 gave a statistically significant improvement in tooth whiteness immediately after brushing in both in vitro and clinical studies. In addition, the toothpaste containing both blue covarine and FD&C Blue No. 1 gave statistically significant greater tooth whitening from baseline than the blue covarine containing toothpastes. CLINICAL SIGNIFICANCE: The silica-based toothpastes containing blue covarine or a combination of blue covarine and FD&C Blue No. 1 evaluated in the current study gave significant tooth whitening benefits immediately after one brush.

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.