Effect of fluoride varnish supplemented with sodium trimetaphosphate on enamel erosion and abrasion: An in situ/ex vivo study

Objective

To evaluate the effect of fluoride (F) varnishes supplemented or not with sodium trimetaphosphate (TMP) on enamel erosive wear followed or not by abrasion in situ.

Methods

Ten volunteers were selected and randomly divided into four groups, according to the varnishes tested: placebo (no F or TMP), 5% NaF (positive control), 2.5% NaF and 2.5% NaF/5% TMP. Enamel blocks (n = 4) were mounted in palatal devices and received an application of each test varnish, following a double-blind, crossover protocol. After 6 h, varnishes were completely removed and the blocks were subjected to erosive challenges by ex vivo immersion in citric acid (5 min, 4×/dia, 5 days). Following, half of the blocks were subjected to abrasion by brushing with a placebo dentifrice slurry for 15 s. Enamel wear (μm), surface hardness (SH_f) and cross-sectional hardness (ΔKHN) were assessed after each experimental period. Results were analyzed by ANOVA, Student–Newman–Keuls's test and Pearson correlation coefficient (p < 0.05).

Results

The fluoride varnish supplemented with TMP promoted significantly lower wear and ΔKHN when compared to the other groups after erosive challenges, followed or not by abrasion (p < 0.05). As for (SH_f) the fluoride varnish supplemented with TMP promoted similar results to the 5% NaF product, being significantly higher than the remaining groups after erosive and erosive + abrasive challenges (p < 0.05).

Conclusion

TMP significantly enhanced the effects of F on enamel wear after erosive challenges, followed or not by abrasion.     

Sodium fluoride mouthrinse used twice daily increased incipient caries lesion remineralization in an in situ model

Objectives

To investigate the remineralizing effects of fluoride mouthrinses used at different times and frequency in addition to fluoride toothpaste.

Methods

A randomized crossover single blinded study comprised 4 experimental phases of 21 days each. Twelve orthodontic volunteers were fixed with an orthodontic bracket containing an artificial carious enamel slab, which was from the same tooth in all 4 phases, and were randomly assigned to the following groups: (1) brushing with F toothpaste 2× per day (F- brush), (2) F- brush + rinsing with 0.05% NaF (F- rinse) after lunch, (3) F- brush + F-rinse before bedtime, and (4) F- brush + F- rinse 2× per day. Mean mineral gain after each phase was determined from mineral density profiles obtained using Micro-CT.

Results

The mean mineral gain in all treatments with F- brush and F-rinse were significantly greater than those in F- brush (p < 0.05). Moreover F- rinse 2× per day increased lesion remineralization more than F- rinse once a day.

Conclusions

The twice-daily use of 0.05% NaF mouthrinse combined with twice-daily regular use of fluoride toothpaste resulted in the greatest remineralization of incipient caries. These data indicate that rinsing frequency is a factor affecting the effectiveness of fluoride mouthrinse.

Clinical significance

The rinsing frequency of NaF mouthrinse, when used with fluoride toothpaste, also affects the remineralization. This finding, if confirmed by a clinical study, would lead to a new recommendation for fluoride mouthrinse used in high caries risk patients who could benefit from using it twice a day.     

Effect of experimental mouthrinses containing the combination of NaF and TiF4 on enamel erosive wear in vitro

Objective

This study analysed the anti-erosive effect of experimental solutions containing TiF₄ and NaF.

Methods

Bovine enamel samples (n = 15) were treated with: (1) commercial solution with SnCl₂/NaF (Erosion Protection^®); (2) experimental solution with 0.0815% TiF₄; (3) 0.105% NaF; (4) 0.042% NaF + 0.049% TiF₄; (5) 0.063% NaF + 0.036% TiF₄ or (6) control. The samples were submitted to pH cycles and daily fluoride applications for seven days. The enamel wear was measured using a contact profilometer and analysed by ANOVA (p < 0.05).

Results

The best anti-erosive effect was found for experimental solution with 0.0815% TiF₄ (99% reduction in enamel wear), followed by SnCl₂/NaF (78%) and 0.049% TiF₄ + 0.042% NaF solution (41%).

Conclusions

The experimental solution containing a specific combination of TiF₄ + NaF has the ability to partially reduce enamel erosion.     

Inhibition of tooth erosion by milk containing different fluoride concentrations: An in vitro study

Objectives

This in vitro study assessed the effect of milk containing different fluoride concentrations on tooth erosion.

Methods

Bovine enamel and root dentine specimens were treated with: (1) bovine whole milk with 0 ppm F; (2) 2.5 ppm F; (3) 5 ppm F; (4) 10 ppm F (all after erosion); (5) whole milk with 0 ppm F (before erosion); (6) NaF (0.05% F, positive control, after erosion) or (7) 0.9% NaCl (negative control, after erosion). The specimens were submitted to pH cycles (4× 90 s in soft drink) and treatments for 5 days. The specimens were immersed in the treatment solutions for 1 min (only at the first cycle each day) with further exposition to 1:1 milk:saliva slurry for 10 min. The tooth loss was measured using a contact profilometer and statistically analysed (p < 0.05).

Results

Rinsing with milk before erosive challenge significantly reduced tooth loss compared to negative control (67% and 24% reduction in dentine and enamel loss, respectively) and to milk after erosive challenge, only for dentine. The addition of fluoride to milk also reduced tooth loss compared to negative control, but with no significant differences among fluoride concentrations for enamel and dentine (μm), respectively: 0 ppm (3.63 ± 0.04 and 2.51 ± 0.53), 2.5 ppm F (2.86 ± 0.42 and 1.96 ± 0.47), 5 ppm F (2.81 ± 0.27 and 1.77 ± 0.44), 10 ppm F (2.03 ± 0.49 and 1.68 ± 0.59). There was a negative and significant correlation between [F] and the tooth loss.

Conclusions

Daily rinse with milk containing F is able to reduce both enamel and dentine erosion in vitro.

Clinical significance

Since the prevalence of dental erosion is steadily increasing, rinse with milk or its derivate might be an important strategy to reduce the progression of tooth erosion.     

Light cola drink is less erosive than the regular one: An in situ/ex vivo study

Objective

This in situ/ex vivo study assessed the erosive potential of a light cola drink when compared to a regular one.

Methods

During 2 experimental 14-days crossover phases, eight volunteers wore palatal devices with 2 human enamel blocks. The groups under study were: group light, erosive challenge with light cola drink and group regular, erosive challenge with regular cola drink. During 14 days, erosive challenges were performed extraorally 3X/day. In each challenge, the device was immersed in 150 ml of light cola (group light) or regular cola (group regular) for 5 min. Erosion was analysed by surface profilometry (μm) and surface microhardness change (%SMH). The data were statistically analyzed using paired t test (p < 0.05).

Results

Group light (0.6 ± 0.2 μm) showed significantly lesser wear than group regular (3.1 ± 1.0 μm). There was no significant difference between the groups for the %SMH (group light −63.9 ± 13.9 and group regular −78.5 ± 12.7).

Conclusions

The data suggest that the light cola drink is less erosive than the regular one.     

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

Objectives

To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro.

Methods

Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm × 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n = 10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle = artificial saliva (2 h, pH 7.0) + erosion (0.3% citric acid, pH 3.2, 5 min) + fluoride/control (5 min) + attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in μm was measured using optical profilometry.

Results

When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences.

Conclusions

The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.     

Randomised in situ trial on the effect of milk and CPP-ACP on dental erosion

Objectives

This randomised in situ study aimed to analyse the effect of milk (with or without 5 ppm F) and CPP-ACP pastes (with or without 900 ppm F) on dental erosion.

Methods

The study was a seven phase (5 days each) crossover design involving 15 participants wearing intraoral appliances with enamel and dentine specimens. Specimens were extraorally eroded (erosive soft drink, 6 × 90 s/day) and brushed (2 × 30 s/day, 2 N) using a non-fluoridated toothpaste (negative control). The test products were milk, milk + 5 ppm F (twice daily, each 100 ml/2 min), CPP-ACP paste, CPP-ACP paste + 900 ppm F (3 min/day) or a SnCl₂/AmF/NaF mouthrinse (positive control, 30 s/day), which were applied immediately after erosion with the appliances in the oral cavity. In an additional group, a fluoridated toothpaste was used without any additional test product. Tissue loss was determined profilometrically after 5 days and statistically analysed by linear mixed models methodologies (p < 0.05).

Results

Compared with the negative control (non-fluoridated toothpaste only, enamel: 2.2 ± 1.3 μm; dentine: 3.8 ± 2.2 μm), enamel and dentine loss was significantly reduced by the use of fluoridated toothpaste (enamel: 1.1 ± 1.0 μm; dentine: 2.4 ± 1.7 μm) and the SnCl₂/AmF/NaF mouthrinse (1.5 ± 1.5 μm; dentine: 1.8 ± 1.9 μm).

Conclusions

Milk and CPP-ACP were not effective in reducing enamel and dentine loss significantly, independently of the presence of fluoride.

Clinical significance

Enamel and dentine erosion were significantly reduced by the use of a fluoridated toothpaste or a SnCl₂/AmF/NaF mouthrinse, but not by milk or CPP-ACP under the conditions of the present study.

Clinical trials registration

NCT01566357.     

Effect of sodium,amine and stannous fluoride at the same concentration and different pH on in vitro erosion

Objective

This study aimed to compare the effects 0.5% and 1% sodium, amine and stannous fluoride at different pH on enamel erosion in vitro.

Methods

Bovine enamel samples were submitted to a cyclic de- and remineralisation for 3 days. Each day, the samples were exposed for 120 min to pooled human saliva and subsequently treated with one of the fluoride solutions for 3 min: amine fluoride (AmF, 0.5% and 1% F⁻), sodium fluoride (NaF, 0.5% and 1% F⁻), each at pH 3.9 and 7.0, and stannous fluoride (SnF₂, 0.5% and 1% F⁻), at pH: 3.9. Additionally, two groups were treated with fluoride-free placebo solutions (pH: 3.9 and 7.0) and one group served as control (no fluoridation). Ten specimens each group were inserted in a so-called artificial mouth and eroded six times daily with hydrochloric acid (pH 2.6) for 90 s each intermitted by exposure to artificial saliva (1 h). After 3 days, enamel loss was analyzed profilometrically and evaluated statistically by ANOVA.

Results

Only the acidic 0.5% and 1% SnF₂ and 1% AmF solutions were able to reduce erosive enamel loss significantly, while all other solutions and placebos did not differ significantly from the control. Between the acidic SnF₂ and the 1% AmF solutions no significant differences could be detected.

Conclusion

At the same concentrations, acidic SnF₂ and AmF may be more effective than NaF to protect enamel against erosion.     

Combined effect of amoxicillin and sodium fluoride on the structure of developing mouse enamel in vitro

Objective

Excess fluoride intake during tooth development is known to cause dental fluorosis. It has also been suggested that amoxicillin use in early childhood is associated with enamel hypomineralization. The aim was to investigate separate and combined effects of sodium fluoride (NaF) and amoxicillin on enamel formation in vitro.

Design

Mandibular molar tooth germs of E18 mouse embryos were cultured for 10 days in a medium containing NaF (10, 12 or 15 μM) and/or amoxicillin (0.5, 1, 2 or 3.6 mg/mL) or sodium clavulanate (0.07 mg/mL) alone or in combination with 0.5 mg/mL of amoxicillin. Morphological changes were studied from the whole tooth photographs and histological tissue sections with light microscope.

Results

Only with the highest concentrations of NaF or amoxicillin alone the extent of enamel in the first molars measured as the vertical enamel height/crown height ratio was reduced (p < 0.01, p < 0.001, respectively). At lower concentrations, combination of NaF (12 μM) and amoxicillin (2 mg/mL) significantly reduced enamel extent compared with the controls (p < 0.001). Histologically, the ameloblasts were still columnar but poorly organized and the nascent enamel was often non-homogeneous. Enamel formation was not seen in any second molars exposed to 12 μM NaF and 2 mg/mL of amoxicillin (or higher concentrations) compared with the presence of enamel in half of the controls (p < 0.001).

Conclusions

Amoxicillin and NaF dose dependently affect developing enamel of mouse molars in vitro and the effects are potentiative. The clinical significance of the results remains to be studied.     

In vitro assessment of artificial saliva formulations on initial enamel erosion remineralization

Objectives

Various formulations of artificial saliva are present in the literature and little guidance is available on the standardization of type of saliva for use in in vitro protocols for erosive studies. The aim of this study was to evaluate the remineralizing capacity of different formulations of artificial saliva on initial enamel erosive lesion.

Methods

Bovine enamel blocks were subjected to short-term acidic exposure by immersion in citric acid 0.05 M (pH 2.5) for 15 s, resulting in surface softening without tissue loss. Then 90 selected eroded enamel blocks were randomly and equally divided into 6 groups according to saliva formulation (n = 15): Saliva 1 (contain mucin); Saliva 2 (Saliva 1 without mucin); Saliva 3; Saliva 4; Saliva 5 (contain sodium carboxymethyl cellulose) and control (C) (deionized water). After demineralization enamel blocks were subjected to remineralization by immersion in the saliva's formulations for 2 h. Enamel remineralization was measured by superficial hardness test (% superficial hardness change). The data were tested using ANOVA and Tukey's test (p < 0.05).

Results

All the tested formulations of artificial saliva resulted in significantly higher enamel remineralization compared to control (p < 0.001). Saliva 3 showed higher percentage of enamel remineralization than Saliva 5 (p < 0.05).

Conclusions

Besides the variety of artificial saliva for erosion in vitro protocols, all the formulations tested were able to partially remineralize initial erosive lesions.     

The effect of saliva substitutes on enamel erosion in vitro

Objectives

To investigate the effect of saliva substitutes on enamel erosion in vitro.

Methods

A total of 204 bovine enamel samples were embedded in acrylic resin and allocated to 17 groups (n = 12). The specimens were eroded in an artificial mouth (3 days; 6 × 30 s/days, flow rate: 2 ml/min) using citric acid (pH: 2.5). Immediately after the erosive attacks, saliva substitutes (12 sprays, 3 gels) were applied. Between the erosive cycles the specimens were rinsed with artificial saliva (flowrate: 0.5 ml/min). A SnCl₂/AmF/NaF-containing mouthrinse was used as positive control, water spray served as negative control. Enamel loss was measured profilometrically and the data were analyzed using one-way ANOVA followed by Scheffé’s post hoc tests (p < 0.05).

Results

Four saliva substitutes increased enamel erosion, probably due to the low pH or the content of citric acid. Several saliva substitutes were able to reduce enamel erosion significantly by 60–90% (in the range of the positive control). The protective potential of these products was in the range of the positive control (reduction of enamel loss to 30% of negative control). The erosion-protective potential of these high-viscous products is probably related to their film-forming properties, leading to a mechanical protection of the surface.

Conclusion

Saliva substitutes containing a very low pH exhibit a distinct erosive potential, while most high-viscous products present an erosion-protective effect. It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.

Clinical significance

It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.     

Prevention of dentine erosion by brushing with anti-erosive toothpastes

Objective

This in vitro study aimed to investigate the preventive effect of brushing with anti-erosive toothpastes compared to a conventional fluoride toothpaste on dentine erosion.

Materials and methods

Bovine dentine specimens (n = 12 per subgroup) were eroded in an artificial mouth (6 days, 6 × 30 s/day) using either citric acid (pH:2.5) or a hydrochloric acid/pepsin solution (pH:1.6), simulating extrinsic or intrinsic erosive conditions, respectively. In between, the specimens were rinsed with artificial saliva. Twice daily, the specimens were brushed for 15 s in an automatic brushing machine at 2.5 N with a conventional fluoride toothpaste slurry (elmex, AmF) or toothpaste slurries with anti-erosive formulations: Apacare (NaF/1% nHAP), Biorepair (ZnCO₃-HAP), Chitodent (Chitosan), elmex Erosionsschutz (NaF/AmF/SnCl₂/Chitosan), mirasensitive hap (NaF/30% HAP), Sensodyne Proschmelz (NaF/KNO₃). Unbrushed specimens served as control. Dentine loss was measured profilometrically and statistically analysed using two-way and one-way ANOVA followed by Scheffe‘s post hoc tests. RDA-values of all toothpastes were determined, and linear mixed models were applied to analyse the influence of toothpaste abrasivity on dentine wear (p < 0.05).

Results

Dentine erosion of unbrushed specimens amounted to 5.1 ± 1.0 μm (extrinsic conditions) and 12.9 ± 1.4 μm (intrinsic conditions). All toothpastes significantly reduced dentine erosion by 24–67% (extrinsic conditions) and 21–40% (intrinsic conditions). Biorepair was least effective, while all other toothpastes were not significantly different from each other. Linear mixed models did not show a significant effect of the RDA-value of the respective toothpaste on dentine loss.

Conclusion

Toothpastes with anti-erosive formulations reduced dentine erosion, especially under simulated extrinsic erosive conditions, but were not superior to a conventional fluoride toothpaste.     

Effect of a single application of TiF4 and NaF varnishes and solutions on dentin erosion in vitro

Objectives

This in vitro study aimed to analyse the effect of a single application of TiF₄ and NaF varnishes and solutions to protect against dentin erosion.

Methods

Bovine root dentin samples were pre-treated with NaF-Duraphat varnish (2.26%F, pH 4.5), NaF/CaF₂-Duofluorid varnish (5.63%F, pH 8.0), NaF-experimental varnish (2.45%F, pH 4.5), TiF₄-experimental varnish (2.45%F, pH 1.2), NaF solution (2.26%F, pH 4.5), TiF₄ solution (2.45%F, pH 1.2) and placebo varnish (pH 5.0, no-F varnish control). Controls remained untreated. Ten samples in each group were then subjected to an erosive demineralisation (Sprite Zero, 4× 90 s/day) and remineralisation (artificial saliva, between the erosive cycles) cycling for 5 days. Dentin loss was measured profilometrically after pre-treatment and after 1, 3 and 5 days of de-remineralisation cycling. The data were statistically analysed by two-way ANOVA and Bonferroni's post hoc test (p < 0.05).

Results

After pre-treatment, TiF₄ solution significantly induced surface loss (1.08 ± 0.53 μm). Only Duraphat reduced the dentin loss overtime, but it did not significantly differ from placebo varnish (at 3rd and 5th days) and TiF₄ varnish (at 3rd day).

Conclusions

Duraphat varnish seems to be the best option to partially reduce dentin erosion. However, the maintenance of the effects of this treatment after successive erosive challenges is limited.     

Degree of mineral loss in softened human enamel after acid erosion measured by chemical analysis

Objectives

Erosive attack on enamel leads to a bulk material loss and a partial demineralisation at the lesion body. This zone of softened enamel has a reduced physical stability and large interprismatic porosities. The aim of the current study was to measure the degree of demineralisation with respect to the content of calcium and inorganic phosphorus in softened enamel using ultrasonication and chemical analysis. The erosive demineralisation was to be compared with demineralisation in caries.

Methods

Erosion of 10 polished human enamel samples was performed in 0.3% citric acid adjusted to pH 3.2 at 35 °C in a slowly stirred solution, each in a volume of 15 ml. After erosion the softened enamel was removed by ultrasonication in 2 ml of deionised water and enamel crystals were dissolved by adding 220 μl of 1 M HCl. Substance loss was measured profilometricaly after erosion and after ultrasonication. Surface size of eroded enamel was measured thus volume loss could be calculated. Calcium and phosphate ion concentration in the solutions were measured after ultrasonication.

Results

Citric acid erosion caused a mean substance loss of 16.0 μm (SD 2.5 μm) and further enamel softening of 2.4 μm (SD 1.5 μm). The degree of demineralisation of softened enamel, in comparison the original mineral content, was 62% for calcium and 64% for inorganic phosphorus was calculated.

Conclusion

The high degree of demineralisation shown in the current study explains the instability of softened enamel even against mild physical impact.     

Remineralizzazione dello smalto esposto all’azione erosiva delle bevande acide

Objectives

Aim of this in vitro study was to evaluate the effect of a calcium-phosphate based (CPP-ACP) paste in remineralisation of enamel surfaces eroded by acid soft drinks by atomic force microscopy (AFM).

Materials and methods

Twenty-four human caries-free central incisors were randomly and equally divided into four groups; teeth were exposed to the erosive action of two different acid soft drinks (Coca Cola and Gatorade) for 10 minutes twice a day for two weeks. After the second exposure, the teeth of two groups were covered with CPP-ACP paste for 10 minutes every day. Then, the samples were observed under AFM.

Results

All samples revealed increased values of surface roughness after exposure to acid soft drinks. Samples treated with CPP-ACP paste showed a significative reduction of roughness values (p < 0,01).

Conclusions

This study showed that acid soft drinks could erode tooth enamel surface; the use of CPP-ACP paste can enhance enamel remineralization.     

Effect of different adhesive systems and laser treatment on the shear bond strength of bleached enamel

Purpose

This study determined the shear bond strength of a nanohybrid composite resin to bleached enamel immediately or 15 days later using different adhesive systems and laser application.

Methods

One hundred and forty enamel specimens were prepared from human molar teeth and bleached either with 16% carbamide peroxide (CP) or 30% CP according to the manufacturer's (Vivastyle/Vivadent) recommendations. After bleaching treatments specimens were divided into two groups according to the treatment time of the adhesive procedures: immediately or 15 days after the bleaching treatments. The four groups were then divided into five subgroups due to the surface treatments: using a two-step self-etching adhesive (AdheSe, Ivoclar Vivadent G, Schaan, Liechtenstein) or a two-step etch and rinse adhesive (Excite, Ivoclar Vivadent G, Schaan, Liechtenstein) and application of laser prior to adhesive procedures or not. After adhesive procedures nanohybrid composite resin cylinders of 4 mm × 2 mm (Tetric Evo Ceram/Vivadent) were bonded to the enamel surfaces. All specimens were subjected to shear bond strength test after thermocycling and 24 h of storage in water. Data were analyzed statistically.

Results

Mann–Whitney U-test analysis showed no significant difference in the mean bond strength values of enamel bleached with either 16% CP or 30% CP (p > 0.05). There was no difference between the groups bonded immediately or 15 days after bleaching (p > 0.05). Application of the etch and rinse adhesive after 15 days showed the highest bond strength values, whereas self-etching adhesive and laser application showed the lowest values in both bleaching treatments.

Conclusions

The results suggested that following the bleaching treatments, the use of etch and rinse adhesive system may provide higher bond strengths than self-etching adhesive and laser application.     

Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion

Objectives

Sn²⁺ has promising erosion-inhibiting properties in solutions, but little is known about respective effects in toothpastes. In addition, biopolymers might have protecting potential. Aim of this study was to investigate the effects of Sn²⁺ in toothpastes and of a biopolymer (chitosan) added to a Sn²⁺ formulation on erosion/abrasion.

Methods

Enamel samples were subjected to cyclic erosion procedures (10 days; 0.50% citric acid, pH 2.5; 6× 2 min/day), and brushing (2× 15 s/day, load 200 g) during immersion in slurries (2 min). The toothpastes were NaF formulations (NaF/1, NaF/2, NaF/3) and Sn²⁺ formulations (NaF/SnCl₂, AmF/SnF₂, AmF/NaF/SnCl₂) and AmF/NaF/SnCl₂ + 0.5% chitosan.Declared concentrations of active ingredients in toothpastes were 1400–1450 μg/g F⁻ and 3280–3500 μg/g Sn²⁺. Negative controls were erosion only and placebo, positive control was a SnF₂ gel. Tissue loss was quantified profilometrically, Sn on enamel surfaces was measured by energy dispersive X-ray spectroscopy.

Results

Loss values (μm) for erosion only and placebo were 14.4 ± 4.5 and 20.2 ± 3.8, respectively, and 4.6 ± 1.9 for the positive control (p ≤ 0.001 each compared to erosion only). The other loss values were: NaF/1 16.5 ± 3.0, NaF/2 14.0 ± 2.7, NaF/3 12.6 ± 3.9, NaF/SnCl₂ 14.7 ± 5.1, AmF/SnF₂ 13.5 ± 4.8, AmF/NaF/SnCl₂ 12.4 ± 4.2, AmF/NaF/SnCl₂ + chitosan 6.6 ± 3.5 (except NaF/1 all p ≤ 0.01 compared to placebo). AmF/NaF/SnCl₂/chitosan was more effective than all other toothpastes (p ≤ 0.01 each). Sn on the enamel surface ranged between 1.3 ± 0.3 and 2.8 ± 0.04 wt.% with no obvious relationship with efficacy.

Conclusions

The NaF and Sn²⁺ toothpastes without chitosan exhibited similar anti-erosion and abrasion-prevention effects. The experimental Sn²⁺ formulation with chitosan revealed promising results similar to those of the positive control.

Clinical significance

NaF toothpastes offer a degree of protection against erosion/abrasion, which is likely sufficient for most subjects with average acid exposures. For patients with initial erosive lesions, however, more effective toothpaste is desirable. The combination of Sn²⁺ and a biopolymer appears promising in this context.     

Effect of a 10% carbamide peroxide on wear resistance of enamel and dentine: In situ study

Objectives

This triple-blind, 2 × 2 crossover in situ study, was undertaken to verify whether the wear resistance of enamel and root dentine would be affected by bleaching with a 10% carbamide peroxide agent and a placebo agent.

Methods

Thirty slabs of each substrate (2 mm × 3 mm × 2 mm) were selected for each phase, after flattening and polishing procedures and microhardness test. After a 7-day lead-in period, one specimen of each substrate was randomly bonded on the facial surface of each one of 30 subject's upper second premolars. The volunteers received instructions on how to perform toothbrushing and application of gel in the tray. Fifteen volunteers bleached their maxillary arch with a 10% carbamide peroxide bleaching agent for a 2-week period, while the remainders used a placebo agent. After a 1-week washout period, a new set of enamel and root dentine slabs were bonded to the premolars and volunteers were crossed over to the alternate agent for 14 days. The resistance of enamel and root dentine to wear following bleaching, toothbrushing and intraoral exposure was measured with a profilometer, using reference areas.

Results

For enamel, ANOVA did not demonstrate significant difference between wear provided by placebo and bleaching agent (p = 0.3713), but higher wear depth was observed for bleached root dentine (p = 0.0346).

Conclusions

While overnight bleaching caused no alteration in wear resistance of enamel, root dentine showed increased tissue loss.     

Combined effects of nano-hydroxyapatite and Galla chinensis on remineralisation of initial enamel lesion in vitro

Objectives

The aim of the present study was to investigate the combined effects of nano-hydroxyapatite and Galla chinensis on remineralisation of initial enamel lesion.

Methods

Bovine enamel blocks with in vitro produced initial lesion were used. The lesions were subjected to a pH-cycling regime for 12 days. Each daily cycle includes 4 × 3 min application with one of five treatments: NaF (positive control), deionised water (negative control), crude aqueous extract of G. chinensis (GCE), nano-hydroxyapatite (nano-HA) and GCE with nano-HA. The samples were subsequently evaluated using a microhardness tester, polarised light microscopy (PLM), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Results

Surface hardness measurements and integrated mineral recovery value obtained from cross-sectional microhardness test (CSMH) revealed that all the treatment groups had significantly greater effect on enhancing remineralisation than that of the negative control group. Detailed investigation of both CSMH and PLM indicated that nano-HA would only help mineral deposition predominate in the outer layer of lesion and had limited capacity to reduce the lesion depth significantly. In GCE–nano-HA combined treatment group, more mineral deposition occurred in the lesion body and lesion depth was reduced significantly. Meanwhile, significantly greater mineral deposition in the outer portion of the lesion was also observed in comparison with GCE group. The results of XRD and SEM also showed that GCE could influence the deposition and adsorption of nano-HA.

Conclusion

There was a significant synergistic effect of combined GCE and nano-HA treatment on promoting the remineralisation of initial enamel lesion.     

The effect of casein phosphopeptide–amorphous calcium phosphate on erosive enamel and dentine wear by toothbrush abrasion

Objective

In addition to its role as a remineralizing agent in preventing dental caries, calcium product (CPP–ACP) delivered as a mousse (Tooth Mousse^®, TM) can reduce erosion of enamel and dentine. The aim of this study was to determine whether CPP–ACP could also reduce erosive tooth wear involving toothbrush abrasion.

Methods

Flat, polished enamel and dentine specimens (n = 72) were subjected to 10 wear regimes, with each regime involving erosion in 0.3% citric acid (pH 3.2) for 10 min followed by toothbrush abrasion in a slurry of fluoride-free toothpaste and artificial saliva (1:3 ratio by weight) under a load of 2N for 200 cycles. The specimens were immersed in artificial saliva for 2 h between wear regimes. In the experimental group 1, TM (containing CPP–ACP) was applied at the beginning of each wear episode for 5 min whereas TM− (without CPP–ACP) was applied in the experimental group 2. No mousse was applied in the control group.

Results

TM significantly reduced enamel wear (mean ± S.E., 1.26 ± 0.33 μm in the experimental group 1 vs 3.48 ± 0.43 μm in the control group) and dentine wear (2.16 ± 0.89 μm in the experimental group 1 vs 10.29 ± 1.64 μm in the control group), and dentine wear was significantly less in the experimental group 1 than in the experimental group 2 (5.75 ± 0.98 μm).

Conclusion

The finding that TM reduced erosive tooth wear involving toothbrush abrasion, probably by remineralizing and lubricating eroded tooth surfaces, may have implications in the management of tooth wear.