Abrasion of human enamel and dentine caused by toothpastes of differing abrasivity determined using an in situ wear model

The early wear susceptibility of cementum, enamel and dentine in vitro

OBJECTIVES

To assess the differential early wear susceptibility of cementum, enamel and dentine at a micron level.

METHODS

Whole human molar buccal surfaces incorporating natural enamel and cementum (n = 20) confirmed by imaging (digital microscopy: Keyence, VHX-7000 Milton Keynes, UK), were mounted, scanned (profilometry: XYRIS 4000, Taicaan, Southampton, UK), and allocated to receive erosion (citric acid, pH 2.7, 30 min (n = 10)) or erosion/abrasion challenges (3 cycles of (citric acid, pH 2.7, 10 min, 60 300 g linear abrasion strokes), n=10). Samples were polished and the experiment repeated on polished enamel, and polished coronal and radicular dentine within the same tooth. Profilometric wear data were obtained using superimposition: GeoMagic (3Dsystems, Darmstadt, Germany) and subtraction: MountainsMap (DigitalSurf, Besancon, France). Data were normal. A general linear model was used to assess differences between groups and substrates.

RESULTS

The mean step height (SD) for natural enamel was 8.82 μm (2.53) for erosion and 11.48 μm (2.95) for erosion/abrasion. For natural cementum, the mean step height was 6.00 μm (2.29) for erosion and 4.67 μm (1.58) for erosion/abrasion. Dentine step heights ranged from 7.20 μm (1.53) for erosion and 9.79 μm (1.01) for erosion/abrasion with no statistical differences in dentine wear. Natural cementum surfaces had the lowest wear (p<0.001). Dentine had significantly less wear than natural enamel (p<0.02).

CONCLUSIONS

Cementum surfaces demonstrated the most wear resistance, followed by dentine under erosion dominant conditions in this in vitro study. Further in-vivo investigations are needed to confirm the intraoral stability of cementum.

CLINICAL SIGNIFICANCE

Cementum may be the least susceptible of dental substrates to wear and dentine does not wear at a faster rate than enamel under erosive conditions. This adds to our knowledge on the development of non-carious cervical lesions and questions whether wear rates will accelerate once dentine is exposed.

Abrasion Behaviour of Different Charcoal Toothpastes When Using Electric Toothbrushes

OBJECTIVES

The purpose of this in vitro study was to compare the abrasion behaviour of different charcoal toothpastes when brushing with electric toothbrushes on human enamel.

MATERIALS AND METHODS

A self-designed brushing machine was built using six commercially available electric toothbrushes in abrasion chambers. Each chamber was constantly supplied with a toothpaste-water mix. Pieces of human enamel, which were embedded in PMMA, were brushed for 4 h. Before and after brushing, profilometer measurements were performed in order to determine the substance loss due to brushing.

RESULTS

The following calculated mean removal values (mean ± SD) were found: (4.6 ± 0.6) µm (Group C: Splat Blackwood), (3.2 ± 0.9) µm (Group D: Curaprox Black is White), (2.3 ± 0.7) µm (Group B: Sensodyne Pro Schmelz), (1.7 ± 0.6) µm (Group A: Water), (1.4 ± 0.6) µm (Group E: Prokudent Black Brilliant). A post hoc Tukey HSD test (p = 0.05) showed that the results for Group A/B/E, Group B/D and Group C each lie within subsets that differ statistically significantly from the other subsets.

CONCLUSIONS

Within the limitations of this in vitro study, it can be stated that some charcoal toothpastes lead to significantly higher abrasion on human enamel, when brushing with electric brushes.

CLINICAL RELEVANCE

As low-abrasion toothpaste is generally advisable, and some charcoal toothpastes should be viewed critically with regard to their abrasive properties.

Activated charcoal toothpastes do not increase erosive tooth wear

OBJECTIVES

To assess the effect of activated charcoal toothpastes on enamel and dentin erosive wear.

METHODS

Ninety enamel and dentin slabs were randomly distributed into 9 experimental groups (n = 10/substrate): Artificial saliva (negative control); Elmex Caries (EXC - 1400 ppm F^- as AmF, reference toothpaste without charcoal); Colgate Luminous White Activated Charcoal (CLW - 1000 ppm F^- as MFP); Colgate Natural Extracts (CNE - 1450 ppm F- as NaF); Oral-B 3D White Mineral Clean (OMC - 1100 ppm F^- as NaF); Curaprox Black is White (CBW - 950 ppm F^- as MFP); Bianco Carbon (BIC - no F^-); Natural Suavetex (NSX - no F^-); Oralgen Nupearl Advanced (ONA - no F^-). Specimens were submitted to a 5-day erosion-toothbrushing abrasion cycling. Surface loss (SL) was determined with an optical profilometer. pH and concentration of available fluoride in the slurries were also assessed. Data were statistically analyzed (α = 0.05).

RESULTS

For both substrates, CBW, CNE and EXC had significantly lower SL values than the control. CLW and OMC promoted significantly less dentin wear than the control. All the other groups did not differ significantly from the control. There was a strong negative correlation between SL and concentration of fluoride in the slurries for enamel (r = -0.77) and dentin (r = -0.91), and a strong positive correlation (r = 0.77) between enamel SL and pH.

CONCLUSIONS

For both substrates, none of the activated charcoal-based toothpastes resulted in higher SL than brushing with artificial saliva. Only two of the charcoal toothpastes and the reference toothpaste were able to provide further protection against SL.

CLINICAL SIGNIFICANCE

Activated charcoal-containing toothpastes are becoming popular, despite the absence of evidence supporting their safety for use by individuals with erosive tooth wear. These products did not pose an additional risk for these subjects. However, it would be preferable to use products that exhibits further protective effect.

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 1^st 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 ± 0.35^a, 1.20 ± 0.22^b, 0.95 ± 0.19^b and 1.98 ± 0.32^a; on day 7 was 3.05 ± 0.40^a, 2.07 ± 0.32^b, 1.36 ± 0.33^c and 3.69 ± 0.27^d respectively. For acid-softened enamel at baseline, enamel loss on day 3 was 3.16 ± 0.19^a, 2.17 ± 0.14^b, 1.70 ± 0.11^c and 3.04 ± 0.19^a; on day 7 was 3.92 ± 0.25^a, 3.07 ± 0.13^b, 2.09 ± 0.15^c and 3.87 ± 0.25^a 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.

Effect of Whitening Toothpastes on Extrinsic Dental Stains

Aim and objectives:

To compare the effectiveness of the stain removing property of the whitening toothpastes (silica [Colgate Visible White], silica, papain and bromelain [Whitospark], and silica and calcium carbonate [Snowdent] containing toothpastes) on extrinsic dental stains and to assess the lasting of tooth whitening effect produced by the whitening toothpastes.

Materials and methods:

It is a randomized, concurrent parallel arm, non-invasive, controlled trial designed to compare the effectiveness of the whitening toothpastes on reducing extrinsic dental stains. Parametric t-test was used.

Results:

A statistically significant difference can be seen between Groups A and B, Groups B and C, and Groups B and D. Maximum mean and percentage reduction was found in Group B at the end of the second month in stain extent and intensity. A statistically significant difference was seen between subgroups B1 and B2. Maximum mean and percentage reduction was found in subgroup B1 at the end of the fourth month in stain extent and intensity.

Conclusion:

Silica, papain, and bromelain containing toothpastes (Whitospark) show effectiveness on reducing extrinsic dental stains.

Effect of Remineralizing Gels on Microhardness, Color and Wear Susceptibility of Bleached Enamel

Objectives:

To evaluate the effect of a remineralizing gel combining fluoride and calcium silicate/phosphate or a sodium fluoride gel on bleached enamel microhardness, color, and wear susceptibility.

Methods and Materials:

Two hundred forty bovine enamel-dentin samples were prepared. Baseline analysis of Knoop microhardness, color coordinates (L*a*b*), and surface profile were performed. According to the baseline microhardness values, specimens were stratified into six groups (n=40): NC (negative control)—no treatment; BL (positive control)—bleaching with 40% hydrogen peroxide gel (Opalescence Boost, Ultradent); BL/Rs—bleaching + application of calcium silicate/phosphate gel (Regenerate Serum, Unilever - Rs); Rs/BL—Rs + bleaching; Rs/BL/Rs—Rs + bleaching + Rs; and BL/F—bleaching + 2% sodium fluoride gel. After the treatment described for each group, color change (ΔE) and microhardness were evaluated again. To evaluate abrasion susceptibility, samples were randomly divided into two subgroups, according to the toothpaste used (Cp—Close Up or Rt—Regenerate), and underwent 100,000 brushing strokes. The profile of each sample was evaluated and the mean wear calculated. The data were analyzed by ANOVA and Tukey tests.

Results:

All bleached groups showed a significant reduction of microhardness in relation to the negative control. The groups treated with remineralizing gels showed a significantly higher microhardness and less wear than the positive control, although nonsignificant differences were observed among them. Nonsignificant differences in ΔE were found among bleached groups. The groups brushed with Regenerate toothpaste showed significantly less wear than those brushed with Close Up toothpaste.

Conclusions:

The remineralizing gels did not interfere with bleaching efficacy. However, all the treatments minimized the surface hardness reduction caused by the bleaching procedure and enamel loss after abrasion. Regenerate toothpaste resulted in less enamel abrasion.

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.

Clinical study investigating abrasive effects of three toothpastes and water in an in situ model

OBJECTIVES

This in situ study compared the abrasive effect of repeated brushings (over 10 days) of a low relative abrasive dentine (RDA) toothpaste with moderate and high relative abrasive dentine (RDA) toothpastes, on human dentine in situ.

MATERIALS AND METHODS

The study design was single centre, single blind, randomized, split mouth, two period, four-treatment cross-over, in situ study in 20 healthy subjects. Subjects wore bi-lateral lower buccal appliances each fitted with four dentine sections with treatment applied with a power toothbrush, during each 10 day study period. Samples were measured at baseline, day 5 and day 10 by contact profilometry, and baseline and day 10 with non-contact profilometry.

RESULTS

Nineteen subjects were included in the efficacy analysis. Results as measured by contact and non-contact profilometry from brushing with the moderate RDA paste and high RDA paste showed significantly (p<0.0001) more abrasion to dentine than brushing with the low RDA paste or water after 10 days. Dentine loss following tooth brushing with the low RDA paste was not significantly different from brushing with water, after 10 days.

CONCLUSIONS

The methodology successfully showed clear differentiation between the amount of dentine lost following toothbrushing with the low RDA paste compared to the moderate or high RDA pastes. Dentine loss following brushing with the low RDA paste showed a comparable degree of abrasion to brushing with water.

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.

Mutual wear evaluation of resin composites when opposing enamel and dentin

Mutual wear rates of resin composites and both superficial and deep layers of enamel and dentin were investigated by means of an in vitro wear test. Occlusal surfaces of extracted molars were ground flat to respective layers of enamel and dentin. Hemispherical-shaped styli (n = 8) made of microfilled and microhybrid composites were placed perpendicular to the finished tooth surface (600 grit) in the presence of tap water, and a two-body wear test (75 N load and 1.2 Hz) was performed for 100,000 cycles. The wear depths on both tooth and composite specimens were determined, and the data were statistically analyzed by two-way ANOVA and Boneferroni test (p < 0.05). The values of deep and superficial dentin specimens against Esthet-X (530.2 +/- 213.0 microm and 717.4 +/- 309.6 microm) were significantly greater than those against Epic-TMPT (34.1 +/- 17.6 microm and 29.3 +/- 10.8 microm). The values of Esthet-X against dentin were the smallest (2.4-2.6 microm), followed by those of the same material against enamel (5.5-6.1 microm), and those of Epic-TMPT against enamel (7.2-7.9 microm). It was concluded that the wear rates of dentin varied with the type of composite used while those of enamel showed the consistency.

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

There has been an increase in the demand from consumers and patients for products that whiten teeth. To meet this demand, a whitening toothpaste containing calcium carbonate and perlite as the abrasive system and an efficacious fluoride source has recently been launched. The aim of the current paper is to review the toothpaste's stain removal efficacy and its effects on enamel and dentine wear. It has been shown to be effective at removing model extrinsic stain in vitro. Further, it has been shown to be more effective in removing naturally occurring extrinsic tooth stain than a silica non-whitening control toothpaste after two weeks of twice daily brushing in a parallel group, double-blind clinical study using 152 adult volunteers. In addition, the enhanced whitening effect did not give a clinically relevant level of wear to enamel or a significant increase in dentine wear compared to marketed non-whitening toothpaste formulations, as shown by using an in situ type model with ex vivo brushing.

The measurement of enamel and dentine abrasion by tooth whitening products using an in situ model

OBJECTIVES

To determine the enamel and dentine wear of two whitening toothpastes using an in situ model with ex vivo brushing.

METHODS

Human enamel/dentine (approximately 50:50) blocks (approximately 4 x 4mm) were placed in the upper buccal aspects of full or partial dentures of a group of 25 subjects. Subjects brushed the specimens ex vivo with either a calcium carbonate/perlite or silica containing whitening toothpaste under exaggerated conditions as compared to normal for 30 s, twice per day. Specimens were removed after 4, 8 and 12 weeks and the wear to the enamel and dentine was determined. Enamel wear was determined by change in Knoop indent length and dentine wear was determined from the enamel-dentine step height, measured using optical profilometry.

RESULTS

The mean wear after 12 weeks was for enamel 0.27 and 0.19 microns, and for dentine 34.3 and 61.1 microns, for the calcium carbonate/perlite and silica toothpastes respectively. There were no significant differences between products after 12 weeks. The rate of wear was found to decrease throughout the duration of the study.

CONCLUSION

There were no significant differences between the two whitening toothpastes in terms of enamel and dentine wear after 12 weeks brushing.