Review of the extrinsic stain removal and enamel/dentine abrasion by a calcium carbonate and perlite containing whitening toothpaste

Analysis of Covarine Particle in Toothpaste Through Microfluidic Simulation, Experimental Validation, and Electrical Impedance Spectroscopy

Covarine, copper phthalocyanine, a novel tooth whitening ingredient, has been incorporated into various toothpaste formulations using diverse technologies such as larger flakes, two-phase pastes, and microbeads. In this study, we investigated the behavior of covarine microbeads (200 μm) in Colgate advanced white toothpaste when mixed with artificial and real saliva. Our analysis utilized a custom-designed microfluidic mixer with 400 μm wide channels arranged in serpentine patterns, featuring a Y-shaped design for saliva and toothpaste flow. The mixer, fabricated using stereolithography 3D printing technology, incorporated a flexible transparent resin (Formlabs' Flexible 80A resin) and PMMA layers. COMSOL simulations were performed by utilizing parameters extracted from toothpaste and saliva datasheets, supplemented by laboratory measurements, to enhance simulation accuracy. Experimental assessments encompassing the behavior of covarine particles were conducted using an optical profilometer. Viscosity tests and electrical impedance spectroscopy employing recently developed all-carbon electrodes were employed to analyze different toothpaste dilutions. The integration of experimental data from microfluidic chips with computational simulations offers thorough insights into the interactions of covarine particles with saliva and the formation of microfilms on enamel surfaces.

Evaluation of Stain Removal Efficacy and Color Stability of Three Different Dentifrices on Artificially Stained Enamel Surface-An In Vitro Study

AIM

The aim of the present study was to assess the stain removal ability and color stability of three distinct dentifrices on artificially stained enamel surface.

MATERIALS AND METHODS

This study included 75 intact, healthy premolars free of dental caries that were extracted during orthodontic therapy. The samples were allowed to dry for 6 hours after being submerged in the prepared tea solution for roughly 18 hours every day. Then this procedure was repeated for seven successive days. All samples were randomly divided into three experimental groups with 25 samples in each group. Group I: control dentifrice, group II: dentifrice containing hydrogen peroxide, group III: dentifrice containing papain and bromelain. A specially designed toothbrushing simulator was used to brush every sample in the relevant group. Using a spectrophotometer and a measurement program, color measurement was evaluated after staining process after 4 weeks and 8 weeks of teeth cleaning. Using a profilometer, the surface roughness values (Ra) were assessed.

RESULTS

After 8 weeks of brushing of stained samples, the color stability was better in dentifrice containing hydrogen peroxide (1.14 ± 0.11) followed by dentifrice containing papain and bromelain (1.22 ± 0.08) and control group (1.30 ± 0.09). And after 8 weeks of brushing of stained samples, the surface roughness was more in dentifrice containing hydrogen peroxide (0.237 ± 0.02) followed by dentifrice containing papain and bromelain (0.229 ± 0.13) and control group (0.207 ± 0.05).

CONCLUSION

The present study concluded that the dentifrice containing hydrogen peroxide showed a superior whitening effect on the stained enamel surface than dentifrice containing papain and bromelain and control dentifrice.

CLINICAL SIGNIFICANCE

The development of various dentifrice products has been greatly aided by the increased demand for an improved esthetic appearance. Teeth's natural color and any external stains that could accumulate on the tooth surface combine to determine a tooth's color. Additionally, the use of whitening dental pastes to remove external stains has grown in favor. With the development of these whitening toothpastes, dentifrices' ability to lessen or eliminate extrinsic dental stains has increased. How to cite this article: Mishra D, Kamath DG, Alagla M, et al. Evaluation of Stain Removal Efficacy and Color Stability of Three Different Dentifrices on Artificially Stained Enamel Surface-An In Vitro Study. J Contemp Dent Pract 2024;25(1):68-71.

Effect of whitening toothpastes on the surface roughness and microhardness of human teeth-an in vitro study

OBJECTIVE

To determine the effect of whitening toothpastes on the surface roughness and microhardness of human teeth.

METHODOLOGY

Surface roughness was estimated using the Talysurf instrument, and microhardness was estimated using the Vickers hardness tester before and after the application of whitening toothpastes on mounted extracted human teeth.

RESULTS

In the activated charcoal group, there was a reduction in the surface roughness from 1.21 at baseline to 1.09 at 1 month and a further reduction to 1.02 at 3 months, which was found to be statistically significant. However, no statistically significant difference in surface roughness was found in the other toothpaste groups. With respect to microhardness, all 4 whitening toothpastes showed a statistically significant reduction in microhardness after 3 months of brushing. However, the reduction was significantly higher in group 2 and in group 4 compared to the others.

CONCLUSION

This study showed that whitening toothpaste containing activated charcoal significantly reduced the surface roughness, whereas toothpastes with blue covarine and toothpastes containing activated charcoal significantly reduced the microhardness of the tooth.

CLINICAL RELEVANCE

This study emphasizes the need for healthcare professionals to be aware of the potential disadvantages of whitening toothpastes and make evidence-based decisions when recommending the product to patients.

Evaluating the Effect of Active Charcoal-Containing Toothpaste on Color Change, Microhardness, and Surface Roughness of Tooth Enamel and Resin Composite Restorative Materials

Methods

Thirty-six bovine incisors and resin composite samples were prepared, stained with black tea, and then randomly divided into two groups. The samples were brushed with a charcoal-containing toothpaste (Colgate® MAX WHITE) and daily toothpaste (Colgate® Max Fresh) for 10,000 cycles. Before and after brushing cycles, color variables (ΔL, Δa, Δb), total color change (ΔE), plus Vickers microhardness were evaluated. Two samples of each group were prepared for surface roughness assessment via atomic force microscope. Data were analyzed by Shapiro-Wilk, Independent sample t-test and Mann-Whitney U tests.

Results

According to the obtained results, ΔE and ΔL were significantly higher whereas Δa and Δb were noticeably lower in charcoal-containing toothpaste group in comparison with daily toothpaste in both composite and enamel samples. The microhardness of samples brushed with Colgate® MAX WHITE was significantly higher than that of Colgate® Max Fresh in enamel (P = 0.04), whereas no significant difference was found in composite resin samples (P = 0.23). Colgate® MAX WHITE enhanced the roughness of both enamel and composite surfaces.

Conclusion

The charcoal-containing toothpaste could improve the color of both enamel and resin composite with no negative effect on microhardness. Nevertheless, its adverse roughening effect should be considered occasionally on composite restorations.

Mechanical Acaricides Active against the Blacklegged Tick, Ixodes scapularis

Cases of Lyme disease in humans are on the rise in the United States and Canada. The vector of the bacteria that causes this disease is the blacklegged tick, Ixodes scapularis. Current control methods for I. scapularis mainly involve chemical acaricides. Unfortunately, ticks are developing resistance to these chemicals, and more and more, the public prefers non-toxic alternatives to chemical pesticides. We discovered that volcanic glass, Imergard^TM WP, and other industrial minerals such as Celite 610 were efficacious mechanical insecticides against mosquitoes, filth flies, and agricultural pests. In this report, when 6-10- and 50-70-day old unfed I. scapularis nymphs were dipped for 1-2 s into Celite, the time to 50% mortality (LT₅₀) was 66.8 and 81.7 min, respectively, at 30 °C and 50% relative humidity (RH). The LT₅₀ was actually shorter at a higher 70% RH, 43.8 min. Scanning electron microscopy showed that the ticks were coated over most of their body surface, including partial to almost total coverage of the opening to their respiratory system. The other mechanical insecticide, Imergard, had similar efficacy against blacklegged unfed nymphs with an LT₅₀ at 30 °C and 50% RH of 70.4 min. Although more research is needed, this study suggests that industrial minerals could be used as an alternative to chemical pesticides to control ticks and Lyme disease.

Vapor Phase Alkylation of Isomeric Cresols with Tert-Butyl Alcohol over Perlite Supported Sulfated Zirconia Catalyst

In the present study, perlite was thermally activated and then modified desirably to generate super acidity by loading different weight percentages of sulfated zirconia (SZ) via the two-step sol-gel method. As-prepared sulfated zirconia perlite (SZP) catalysts showed suitable catalytic potential in the vapor phase alkylation of o, m, and p-cresols with tert-butyl alcohol. The presence of crystalline phases in SZP catalysts was confirmed by XRD and FT-IR studies. TEM images revealed the nano size of the catalysts in the range of 9–25 nm. The presence of SZ on the surface of perlite was further confirmed by N2 adsorption–desorption, SEM, SEM-EDX, TGA, and UV-Vis DRS techniques. The pyridine FT-IR results confirmed the existence of Brønsted, Lewis acidic sites and their combination as super acidic catalytic active centers on the surface of catalyst utilized in the vapor phase alkylation of o, m, and p-cresols with tert-butyl alcohol. The regeneration and reusability of the preferred catalyst until the 5th reaction cycle without any considerable loss in catalytic activity demonstrated the stability of the catalyst. Comparative studies show that SZP can be regenerated and is superior compared to other catalysts previously used for other alkylation reactions with the potential for use on a large scale.

New thinking for filth fly control: residual, non-chemical wall spray from volcanic glass

Filth flies are of medical and veterinary importance because of the transfer of disease organisms to animals and humans. The traditional control methods include the use of chemical insecticides. A novel mechanical insecticide made from volcanic glass and originally developed to control mosquitoes (Imergard™ WP; ImG) was investigated for control of adult grey flesh flies, Sarcophaga bullata (Parker), secondary screwworms, Cochliomyia macellaria (F.), and house flies, Musca domestica L. In a modified WHO cone test device, the time to 50% mortality (LT₅₀ ) when applied at 5 g/m² (tested at 30 °C and 50% relative humidity (rH)) was 7.1, 4.3 and 3.2 h, respectively. When knockdown was included, the LT₅₀ s were 5.5, 1.5 and 2.8 h, respectively. Application rates of 1.25 and greater g/m² had the shortest LT₅₀ s. The time to the LT₅₀ increased for M. domestica as rH increased, but ImG was still active at the highest rH tested of 70%. Scanning electron micrographs showed ImG was present on all body parts, unlike that for mosquitoes where it was found mostly on the lower legs. These first studies on the use of Imergard WP against flies suggest this could be an alternative method for filth fly control.

Composite surface roughness and color change following airflow usage

Background

Esthetic dental restorations have gained increasing popularity. The surface of restorations should be smooth enough to achieve maximum esthetics and prevent the adhesion of microorganisms and food particles. This study aimed to assess the surface roughness and color change of composite specimens following airflow usage.

Methods

In this in vitro, experimental study, 30 Tokuyama composite discs were fabricated and randomly divided into three groups (n = 10) for the use of airflow with calcium carbonate/bicarbonate powder and conventional polishing with FlexiDisc. The surface roughness of the specimens was measured by profilometry while the color change was assessed by measuring the L*, a* and b* color parameters using spectrophotometry before polishing (T1). The composite specimens were then polished for stain removal, and their surface roughness as well as color parameters were remeasured after polishing (T2). Paired t-test and Tukey’s test were applied for within-group and between-group comparisons.

Results

Significant differences were noted in roughness average (Ra) between airflow with calcium carbonate (0.251 ± 0.014 μm) and airflow with sodium bicarbonate (0.421 ± 0.208 μm), and between airflow with sodium bicarbonate and FlexiDisc (0.207 ± 0.076 μm) groups after polishing (P < 0.05). Regarding the correlation of change in surface roughness and color parameters at T1 and T2, an inverse correlation was noted between the change in surface roughness and all color parameters except for L*. In other words, reduction in surface roughness decreased the a* and b* color parameters.

Conclusions

Within the limitations of this study, the results showed that the airflow device used in this study had no significant difference with conventional polishing in terms of reduction in surface roughness and staining. Considering the cost and maintenance of the airflow device, it is not suggested as a suitable alternative to the conventional polishing procedures.

Trial Registration Number: This study does not involve human subjects.

Colour stability of stained composite resins after brushing with whitening toothpaste

OBJECTIVE

The aim of this study was to evaluate the effect of brushing with whitening toothpaste on the colour change of composite resins discoloured with coffee.

METHODS

Disc-shaped samples were prepared using one nano-hybrid (Clearfil Majesty Esthetic), one micro-hybrid (GC G-aenial Anterior) and one nano-ceramic composite (Zenit) (n = 6). After initial colour measurements, the samples were coloured in the coffee solution for 5 days. Colour measurements were made again after the colouring process, and brushing simulation was applied for 7, 15 and 30 days with two different whitening toothpastes containing calcium carbonate+perlite (Signal whitening system, SWN) and hydrated silica+hydrogen peroxide (Colgate optic White, COW) and a conventional non-whitening toothpaste containing hydrated silica (Sensodyne pronamel, SPN). Colour change (∆E₀₀ ) after brushing was calculated using the CIEDE2000 system. Repeated measures variance analysis was used for the analysis of data.

RESULTS

G-aenial anterior and Zenit showed significant coloration compared to Majesty esthetic after coloration with coffee (p < 0.05). The colour change in all composite resins was above the clinically acceptable limit (ΔE₀₀  > 1.8). Colour change over time after brushing with both whitening toothpastes differed significantly (p < 0.05). SWN and COW exhibited a significantly higher whitening effect than SPN (p < 0.05). While there was no significant difference in composite groups brushed with the SWS (p > 0.05), there was a significant difference between Majesty esthetic, G-aenial anterior and Zenit in groups brushed with COW (p < 0.05).

CONCLUSIONS

Colour change was high in micro-hybrid and nano-ceramic composites which were discoloured in coffee. The whitening toothpastes were effective in reducing the coloration caused by coffee.

Adhesion and whitening effects of P11-4 self-assembling peptide and HAP suspension on bovine enamel

OBJECTIVES

This study evaluated the adhesion and whitening effects of a combination of P11-4 self-assembling peptide and hydroxyapatite (peptide-HAP) on bovine enamel.

METHODS

Forty-six caries-free bovine teeth were selected, and 40 teeth were randomly allocated to one of five groups (n = 8). First, the effects of application frequency, exposure time, and storage in saliva on the whitening effects of an experimental low-concentrated peptide-HAP suspension (0.5 wt% HAP; Curodont, Credentis) were evaluated and compared with a commercial bleaching agent (VivaStyle Paint on Plus, VS, Ivoclar Vivadent). Tooth color was measured using a spectrophotometer (Gretag MacBeth), and color changes ΔE were statistically analyzed. Second, the effects of peptide-HAP concentration (low versus high: 6.25% HAP; Curodont Protect), and its interactions with saliva and postapplication restaining, were investigated. Third, enamel surfaces (n = 2) were treated with low concentration peptide-HAP and high-concentration peptide-HAP in polymeric and monomeric forms (Curodont Protect & Curodont Repair, Credentis) and analyzed by SEM.

RESULTS

The ΔE of the low-concentration peptide-HAP suspension did not differ from that of VS. Application frequency, exposure time, and storage in saliva did not have any significant impact on whitening efficacy of the peptide-HAP suspension. Increasing the concentration of the suspension did not promote overall ΔE. SEM observations confirmed the presence of the newly generated peptide and HAP on the enamel surface.

CONCLUSIONS

The peptide-HAP suspension is a mild tooth whitener, and the adhesion of peptide-HAP to enamel is concentration dependent.

CLINICAL RELEVANCE

This peptide-HAP suspension is effective in offsetting discoloration caused by restaining after treatment.

Effect of an Optical Whitening Toothpaste on Color Stability of Tooth-Colored Restorative Materials

Objectives  This study aimed to assess the effect of an optical whitening toothpaste on color stability of microhybrid, nanofilled, and microfilled composite resins and resin-modified glass ionomer (RMGI) cement in comparison of two other toothpastes.

Materials and Methods  In this experimental study, disc-shaped composite samples were fabricated. The samples were then polished using silicon carbide papers. Twenty-seven samples of each material were fabricated and subjected to colorimetry using a spectrophotometer. Each group of material was then divided into three subgroups for the application of conventional whitening and whitening containing blue covarine toothpastes. One operator brushed the samples with an electric soft toothbrush with circular motion twice a day, each time for 30 seconds. Colorimetry was performed at 0, 1, 7, 30, and 90 days.

Statistical Analysis  Two-way analysis of variance (ANOVA), one-way ANOVA, and Tukey’s honestly significant difference (HSD) test were used for statistical analysis.

Results  The interaction effect of type of restorative material and time on ∆E was not significant at baseline or 1 day ( p > 0.05). The effect of type of toothpaste on ∆E was not significant at baseline or 1 day ( p = 0.78) but the effect of type of material was significant ( p < 0.05). The toothpastes had significantly different effects on ∆E of Z250 at all time points ( p < 0.05) except for ∆E0–30 ( p = 0.106). The toothpastes had significantly different effects on ∆E of Z350 and Gradia at all time points ( p < 0.05). The same was true for RMGI except for ∆E0–7 ( p = 0.43) and ∆E0–90 ( p = 0.52). The majority of color changes caused by toothpastes were not clinically perceivable (∆E < 3.3), except for ∆E0–90 by the whitening toothpaste (∆E = 9), ∆E0–90 by the conventional toothpaste for Z350 (∆E = 3.9), and ∆E0–1 by the whitening toothpaste for RMGI (∆E = 3.7).

Conclusion  The color change of all composite samples was not clinically perceivable (<3.3) at all time points, which shows that the tested toothpastes do not cause a significant change in color of composite materials.

Toothpaste Composition Effect on Enamel Chromatic and Morphological Characteristics: In Vitro Analysis

The aim of this in vitro study was to assess the effect of toothpastes, with different compositions, on optical and morphological features of sound and demineralized enamel. We selected twenty-five teeth, recently extracted for orthodontic purposes, for this in vitro study. The teeth were caries free, without stains, fissures, filling or hypoplasia observed at inspection under standard conditions. Teeth were brushed (for 2–3 min, twice a day, for 21 days), with five different toothpastes (four commercially available and an experimental one) containing fluoride and hydroxyapatite. After that, teeth were demineralized with 37% orthophosforic acid (Ultra Etch^®, Ultradent Products Inc., South Jordan, UT, USA) for 60 s. We repeated the brushing protocol for another 21 days on demineralized enamel. Enamel vestibular surfaces were examined using a spectrophotometer (Vita EasyShade -Vita Zahnfabrik, Bad Sackingen, Germany) and a Scanning Electron Microscope (Inspect S^®, FEI Company, Hillsboro, OR, USA). Differences were statistically significant for colour parameters L* and ΔE*. SEM evaluation reveals demineralized enamel mineral gain after brushing with selected toothpastes. Toothpastes with specific ingredients can represent a balance between aesthetic and mineralization, and an oral hygiene correct algorithm is able to preserve enamel characteristics during ortodontic treatement with fixed appliances.

The Effect of Different Bleaching Treatments and Thermal-Mechanical Cycling on the Shear Bond Strength of Orthodontic Brackets

Objective

The aim of the present study was to compare the shear bond strength (SBS) of orthodontic brackets bonded to the enamel after at-home and in-office bleaching treatments.

Methods

Sixty bovine incisors were subjected to initial color readings and then classified into three groups: CP (16% carbamide peroxide), HP (35% hydrogen peroxide), and C (control). After treatments, new color readout was obtained, and orthodontic brackets were bonded to the bleached area. Half of the samples of each group (n=10) were subjected to thermal-mechanical cycling (TMC) testing (1,200,000 cycles; 44.2 N; 2 Hz/s), whereas the other half were stored in distilled water at 37 °C for 24 h. Samples were subjected to the SBS test at a speed of 0.5 mm/min. The mean SBS was analyzed (two-way ANOVA, Bonferroni test, p<0.05), and the fracture patterns were classified as adhesive, cohesive, and mixed types.

Results

There was no difference (p>0.05) in SBS values between the samples subjected to TMC and the cycled samples in any group. Samples subjected to carbamide peroxide presented lower SBS (p<0.05) than the non-cycled ones. Enamel adhesive fractures were higher in the bleached groups than in the control group, which presented mixed fractures prevalence, regardless of whether it was subjected to TMC or not.

Conclusion

Thermal-mechanical cycling was not significant for SBS of orthodontic brackets, but tooth bleaching was a factor.

Effect of pH on whitening efficacy of 35% hydrogen peroxide and enamel microhardness

OBJECTIVE

This study aimed to evaluate the effect of 35% hydrogen peroxide at different pH values and the degree of tooth staining on whitening efficacy and enamel microhardness.

MATERIALS AND METHODS

90 enamel-dentin specimens were obtained from bovine incisors. They were randomly divided into 2 groups (n = 45), 1 group was immersed in a staining broth for 14 days, and another group was not stained and kept in distilled water at 37°C. Twenty-four hours after the staining procedure, each group was distributed into 3 subgroups that were whitened by 35% hydrogen peroxide with different pH values (5, 7, and 8.4) for 30 minutes. The color was measured at baseline and 7 days after whitening. Microhardness was measured at baseline, immediate, 24 hours, and 1 month after the whitening procedure. Data were submitted to 2-way analysis of variance (ANOVA) and the Tukey test for multiple comparisons for color analysis. Repeated measures ANOVA and the Tukey test were used to analyze microhardness data.

RESULTS

The color change of the stained groups (ΔE₀₀  = 4.6) was significantly higher than that of the nonstained groups (ΔE₀₀  = 3.7). Microhardness value decreased significantly immediately after whitening for all subgroups and did not return to initial values. For each measurement time, microhardness was not significantly different among subgroups with different pH values.

CONCLUSIONS

Despite the effectiveness of 35% hydrogen peroxide, changes on gel pH did not affect the whitening efficacy, and the enamel was superficially demineralized, regardless of pH values.

CLINICAL SIGNIFICANCE

Independently of the pH value of whitening gel, enamel undergoes superficial demineralization and with a reduction in superficial microhardness that does not return to the initial values. However, using hydrogen peroxide with different pH values does not alter the whitening effect.

An in vitro screening assay for dental stain cleaning

BACKGROUND

The present study aimed to develop an in vitro model for stain removal from natural enamel for the assessment and comparison of oral hygiene products.

METHODS

Bovine teeth (n = 8 per group) were ground/polished to provide flat enamel specimens and ferric-tannate deposits were precipitated onto the enamel surfaces. The ferric-tannate stained enamel specimens were brushed using an in vitro tooth-brushing simulator with slurries containing commercially available toothpaste products, dental abrasive particles, and sodium tripolyphosphate (STP) solutions of different concentrations. The colour of the enamel surfaces was measured using a spectrophotometer before and after stain application as well as after the brushing treatments.

RESULTS

Differences in stain removal efficacy were found between the toothpastes categorised as whitening and non-whitening comprising of different types of dental abrasives (hydrated silica and alumina). A mean value of 27% for stain removal was detected for the three non-whitening toothpastes and 59% of stain removal was detected for the three whitening toothpastes after 1000 strokes. Compared with the slurry with Zeodent 113 abrasive alone, the addition of STP provided better performance for stain removal under the same brushing conditions (mean value of 62% for Zeodent 113 abrasive alone and 72% with the addition of 5% (w/w) STP after 1000 strokes). No difference was evident between the STP concentration of 5% (w/w) and 10% (w/w).

CONCLUSIONS

The ferric-tannate/bovine enamel model reported here provides good stain retention, is rapidly and easily prepared, and is shown to be progressively and reproducibly sensitive to toothbrushing using different toothpastes and surfactant/chelating agent solutions. Importantly, it provides good discrimination between various oral hygiene products. The stain removal assay reported here has considerable potential to enable comparative assessments of different toothpaste types in terms of their cleaning capabilities.

Comparison of effectiveness of abrasive and enzymatic action of whitening toothpastes in removal of extrinsic stains - a clinical trial

OBJECTIVE

To compare the effectiveness of abrasive component (perlite/calcium carbonate) and enzymatic component (papain and bromelain) of whitening toothpaste in removal of extrinsic stains.

METHODS

This study is a randomized, triple blind and parallel group study in which 90 subjects aged 18-40 years were included. At baseline, stains scores were assessed by Macpherson's modification of Lobene Stain Index and subjects were randomly assigned to two groups with 45 subjects in each. Group 1 used whitening toothpaste with enzymatic action and group 2 with abrasive action. After 1 month, stain scores were assessed for the effectiveness of the two toothpastes and 2 months later to check the stain prevention efficacy. Wilcoxson's test was used to compare between baseline 1 and 2 months stain scores, and Mann-Witney U-test was applied for intragroup comparison.

RESULTS

The mean baseline total stain score for the subjects allocated to the enzymatic toothpaste was 37.24 ± 2.11 which reduced to 30.77 ± 2.48 in 1 month, and for the abrasive paste, total stain reduced from 35.08 ± 2.96 to 32.89 ± 1.95. The reductions in total stain scores with both the pastes were significant compared with baseline stain scores (at 1 month Group 1, P = 0.0233 and Group 2, P = 0.0324; at 2 months, Group 1 P = 0.0356). Both the toothpastes proved to be equally good in removal of extrinsic stains; however, the enzymatic paste showed better results as compared to abrasive toothpaste.

CONCLUSION

Whitening toothpaste with abrasive action and enzymatic action are equally effective in removal of extrinsic stains; however, whitening toothpaste with abrasive action needs to be used with caution.

The importance of measuring toothpaste abrasivity in both a quantitative and qualitative way

OBJECTIVE

To evaluate the relative abrasivity of different toothpastes and polishing pastes both qualitatively and quantitatively.

MATERIALS AND METHODS

Acrylic plates were exposed to brushing in a brushing machine with a toothpaste/water slurry for 1 and 6 h. Twelve different toothpastes were used and also four different polishing pastes. The results were evaluated using a profilometer after 1 and 6 h of brushing (corresponding to 2000 and 12 000 double strokes, respectively). A surface roughness value (Ra-value) and also a volume loss value were calculated from the profilometer measurements. These values were then correlated to each other. An unpaired t-test for the difference in the abrasion values between the toothpastes and the abrasion values over time was used.

RESULTS

The polishing paste RDA® 170 yielded higher Ra-values than RDA 250®, both after 1 and 6 h of brushing (1.01 ± 0.22 and 8.99 ± 1.55 compared to 0.63 ± 0.26 and 7.83 ± 5.89, respectively) as well as volume loss values (3.71 ± 0.17 and 20.20 ± 2.41 compared to 2.15 ± 1.41 and 14.79 ± 11.76, respectively), thus poor correlations between the RDA and Ra and Volume loss values were shown. Among the toothpastes, Apotekets® showed the highest Ra value after 1 h of brushing and Pepsodent® whitening after 6 h of brushing. Pepsodent® whitening also showed the highest volume loss values, both after 1 and 6 h of brushing.

CONCLUSION

This study emphasizes the importance of not only considering the RDA value, but also a roughness value, when describing the abrasivity of a toothpaste. Furthermore, it can be concluded that so called 'whitening' toothpastes do not necessarily have a higher abrasive effect than other toothpastes.

ESR investigation of ROS generated by H2O2 bleaching with TiO2 coated HAp

It is well known that clinical bleaching can be achieved with a solution of 30% hydrogen peroxide (H2O2) or H2O2/titanium dioxide (TiO2) combination. This study examined the hypothesis that TiO2 coated with hydroxyapatite (HAp-TiO2) can generate reactive oxygen species (ROS). ROS are generated via photocatalysis using electron spin resonance (ESR). The bleaching properties of HAp-TiO2 in the presence of H2O2 can be measured using hematoporphyrin litmus paper and extracted teeth. We demonstrate that superoxides (O2(•-)) and hydroxyl radicals (HO(•)) can be generated through excitation of anatase TiO2, rutile TiO2, anatase HAp-TiO2, and rutile HAp-TiO2 in the presence of H2O2. The combination of R HAp-TiO2 with H2O2 produced the highest level of HO(•) generation and the most marked bleaching effects of all the samples. The superior bleaching effects exhibited by R HAp-TiO2 with H2O2 suggest that this combination may lead to novel methods for the clinical application of bleaching treatments.

Interaction between biopolyelectrolytes and sparingly soluble mineral particles

We investigate the complex physicochemical behavior of dispersions containing calcium carbonate (CaCO(3)) particles, a sparingly soluble mineral salt; and carrageenans, negatively charged biopolyelectrolytes containing sulfate groups. We reveal that the carrageenans suspend and stabilize CaCO(3) particles in neutral systems by absorbing on the particle surface which provides electrosteric stabilization. In addition, carrageenans provide a weak apparent yield stress which keeps the particles suspended for several months. The absorption measurements of carrageenan on the CaCO(3) particle indicate that more carrageenan is removed from the solution than expected from the case of a simple monolayer adsorption. Confocal laser scanning microscopy observations confirm that polyelectrolyte-containing precipitate is formed in both CaCO(3)-carrageenan and CaCl(2)-carrageenan mixtures. On the basis of these results, we confirm that in the presence of carrageenan some CaCO(3) dissolves and the Ca(2+) ions interact with the sulfate groups leading to aggregation and formation of particle-like structures. These new insights are important for fundamental understanding of other mineral-polyelectrolyte systems and have important implications for various industrial applications where calcium carbonate is used.

Whitening toothpastes: a review of the literature

OBJECTIVES

To review and summarise the whitening agents contained within tooth whitening toothpaste formulations, their mode of action in tooth whitening, and the in vitro and clinical methods used to evaluate and demonstrate their efficacy.

METHODS

Original scientific full papers or reviews listed in ISI Web of Science and Medline were included in this review using the search terms white*, toothpaste and dentifrice.

CONCLUSIONS

Due to the reported consumer and patient dissatisfaction with their perceived tooth color, toothpaste manufacturers have responded by developing a vast array of contemporary whitening toothpastes. One of the key functional ingredients in whitening toothpastes is the abrasive system. In general, these have been designed to give effective removal of extrinsic stains and help prevent tooth stains from reforming without undue abrasivity towards the dental hard tissues. Whitening toothpastes may contain additional agents that augment the abrasive cleaning by aiding the removal and/or prevention of extrinsic stains, for examples, peroxide, enzymes, citrate, pyrophosphate and hexametaphosphate, or optical agents such as blue covarine which can improve tooth whiteness following tooth brushing. In vitro methods used to evaluate tooth whitening efficacy typically determine the ability of a toothpaste formulation to remove/prevent model extrinsic stains on substrates such as enamel or hydroxyapatite or changes in the intrinsic color of tooth specimens. Clinical protocols for evaluating the efficacy of whitening toothpastes typically determine either stain removal or prevention, where changes in natural stain or chlorhexidine/tea induced stain are measured typically over 2-6 weeks. In some clinical studies the overall tooth color change was measured using techniques such as Vita shade guides, colorimeters and image analysis of digital photographs of teeth.

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.

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.