Retention of KOH-soluble fluoride on enamel and dentine under erosive conditions--A comparison of in vitro and in situ results

OBJECTIVES: Aim of the study was to investigate the stability of CaF(2)-like precipitates on enamel and dentine under neutral or acidic conditions and to compare in vitro and in situ results. METHODS: Human enamel and dentine specimens were fluoridated (Elmex fluid, 5 min) and subjected to erosive demineralisation (Sprite light: 3/day each; 30 s in vitro, 2 min in situ) or stored under neutral conditions for 4 (in vitro) or 7 (in situ) days. KOH-soluble fluoride was determined using an ion selective electrode. Between the acid attacks, specimens were stored in remineralisation solution (in vitro) or retained in the oral cavity (four volunteers for enamel and dentine each). RESULTS: Initially, high amounts of KOH-soluble fluoride were gained (between 77.9+/-12.3 and 96.0+/-46.4 microg/cm2). Under neutral conditions in vitro, a significant decrease on enamel (16.2+/-5.0 microg/cm2) and dentine (18.6+/-10.5 microg/cm2) was found, which was more severe under acidic conditions (6.3+/-3.0 and 5.1+/-2.1 microg/cm2, respectively). Under in situ conditions, KOH-soluble fluoride was strikingly stable on enamel under neutral (42.3+/-12.6 microg/cm2) as well as under acidic conditions (54.1+/-17.4 microg/cm2). On dentine, the dissolution kinetics of KOH-soluble fluoride was similar to the in vitro conditions, but the loss was less severe (45.3+/-12.9 microg/cm2 under neutral and 8.8+/-6.4 microg/cm2 under acidic conditions). CONCLUSIONS: In vitro, more KOH-soluble fluoride was lost under erosive compared to neutral conditions. The intra-oral environment was considerably protective for CaF2-like precipitates especially on enamel.     

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.     

Erosion-inhibiting potential of a stannous chloride-containing fluoride solution under acid flow conditions in vitro

Objectives

This study aimed to analyse the erosion-inhibiting potential of a single application of stannous chloride-containing fluoride solution on pellicle-covered enamel and dentine under constant acid flow conditions in vitro.

Design

Bovine enamel (n = 60) and dentine (n = 60) samples were exposed 1 h to the oral cavity of 4 healthy volunteers to allow for in situ pellicle formation. Pellicle-covered samples were randomly assigned to three groups (each n = 20 enamel and n = 20 dentine samples; 5 enamel and 5 dentine samples/volunteer) and treated once with a SnCl2/AmF/NaF (800 ppm Sn(II), 500 ppm F, pH 4.5) or a NaF solution (500 ppm F, pH 4.5) for 2 min or remained untreated (controls). Samples were eroded with hydrochloric acid (pH 2.6) in a small erosion chamber at 60 μl/min for 25 min. Calcium release into the acid was monitored in consecutive 30 s intervals for 5 min, then at 1 min intervals up to a total erosion time of 25 min using the Arsenazo III procedure. Data were statistically analysed by random-effects linear models (p < 0.05).

Results

The stannous chloride-containing fluoride solution reduced calcium loss of enamel and dentine to up to 6 min and 3.5 min, respectively. Calcium loss (% of control) amounted from 24 ± 7 (30 s) up to 93 ± 14 (6 min) in enamel and from 38 ± 13 (30 s) to 87 ± 15 (3.5 min) in dentine. The sodium fluoride solution was unable to reduce enamel and dentine erosion at any time point.

Conclusion

A single application of a stannous chloride-containing fluoride solution reduced enamel and dentine erosion up to 6 min and 3.5 min of constant acid flow, respectively.     

Frequency of intake and amount of fluoride in milk for remineralisation of artificial caries on enamel and dentine: Ex vivo/in situ study

ObjectivesThis study analysed the effect of frequency of intake and amount of fluoride in milk on the remineralisation of artificial enamel and dentine caries lesions ex vivo/in situ.Materials and methodsPre-demineralised bovine enamel and dentine slabs were randomly allocated into 5 groups and fixed in removable appliances used by subjects for 7 days in each phase. Each treatment comprised milk containing 2.5 ppm fluoride daily (T1), or every other day (T2), 5.0 ppm F daily (T3), or every other day (T4) or no treatment (T5).ResultsEnamel alterations were quantified by surface hardness recovery (%SHR) and transversal microradiography (TMR), and in dentine by TMR only. Data were analysed by ANOVA and Tukey’s test (p < 0.05). For enamel, the highest %SHR was found for T1 and T3 compared to control, without significant differences between them. All groups showed positive values of ΔΔZ − T1 (247.3 ± 198.5); T2 (110.9 ± 303.2); T3 (226.0 ± 299.2); T5 (5.0 ± 288.0), except T4 (−274.5 ± 407.3). For dentine, the only group that presented remineralisation was T2 (350.0 ± 657.5).ConclusionsFluoridated milk daily seems to have higher remineralising effect on enamel than its use every other day. Dentine, does not seem to benefit from daily use of fluoridated milk.     

Protection of short-time enamel erosion by different tetrafluoride compounds

OBJECTIVE: This in vitro study aimed to analyse the protective effect of differently concentrated titanium (TiF(4)), zirconium (ZrF(4)) and hafnium (HfF(4)) tetrafluoride on enamel erosion. METHODS: Polished enamel surfaces of 36 bovine crowns were covered with tape leaving 4 enamel windows each 3mm in diameter exposed. The crowns were randomly assigned to six groups (each n=6) and pretreated with 4% TiF(4), 10% TiF(4), 4% ZrF(4), 10% ZrF(4), 4% HfF(4) or 10% HfF(4) for 4 min (first window), 10 min (second window) or 15 min (third window). The fourth window of each crown was not pretreated and served as control. Erosion was performed stepwise with 1% HCl (pH 2) in five consecutive intervals of each 15 s (total 75 s). Enamel dissolution was quantified by colorimetric determination of phosphate release into the acid. For each tooth, cumulative phosphate loss of enamel pretreated with one of the tetrafluoride compounds was calculated as percentage of the respective control and statistically analysed using two-way ANOVA. RESULTS: Enamel erosion was significantly reduced by TiF(4), ZrF(4) and HfF(4) application. Cumulative phosphate loss (mean % of control, 75s erosion) after 4-15 min application was significantly lower for 4% ZrF(4) (7-11%), 10% ZrF(4) (2-6%), 4% HfF(4) (11-9%) and 10% HfF(4) (12-16%) compared to 4% TiF(4) (42-27%) and 10% TiF(4) (54-33%). Only for 4% and 10% TiF(4), phosphate loss decreased with increasing duration of application, but also increased with increasing acid intervals. CONCLUSION: TiF(4), ZrF(4) and HfF(4) might protect enamel against short-time erosion, but protection was more enhanced by ZrF(4) and HfF(4) compared to TiF(4) application overtime.     

Quantitative analysis of the impact of the organic matrix on the fluoride effect on erosion progression in human dentine using longitudinal microradiography

After an initial demineralisation, an intensive fluoridation is capable of inhibiting the erosive mineral loss in dentine completely, which might be related to the presence of the exposed organic dentine matrix. Aim of the present study was, therefore, to evaluate whether fluoride is also effective when the organic material is removed. The study was a cyclic de- and remineralisation model over 5 days in vitro. Samples from human coronal dentine were demineralised with citric acid (pH 2.3; 6 x 10 min per day) and intermittently stored in a remineralisation solution. Groups (n = 25 each) were defined as follows: Group 1: erosion only, no fluoridation; Group 2: erosion, alternately fluoridation with toothpaste (NaF; 0.15% F-; 3 x 5 min per day), mouthrinse (Olaflur/SnF2; 0.025 F-; 3 x 5 min per day) and gel (Olaflur/NaF; 1.25% F-; at Days 1 and 3 instead of one toothpaste application); Group 3: erosion and fluoridation as Group 2, organic material was continuously removed with collagenase (from Clostridium Histolyticum type VII, 100 U/ml) added to the remineralisation solution. Mineral content was monitored daily using longitudinal microradiogaphy. After fluoridation in the presence of collagenase, a linear increase in mineral loss (73.3 +/- 17.6 microm at Day 5) was observed, which significantly (P < or = 0.001) exceeded that of the control group (45.9 +/- 14.3 microm at Day 5). After fluoridation in the absence of collagenase, mineral loss ceased after the 2nd day (12.2 +/- 10.2 microm at Day 5) and was significantly lower compared to Groups 1 and 3 (P < or = 0.001). The results indicate that the dentine matrix is essential for the effectiveness of fluoride in dental erosion.     

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.     

A qualitative and quantitative investigation into the effect of fluoride formulations on enamel erosion and erosion-abrasion in vitro

Objectives

To investigate the effect of a single application of highly concentrated SnF₂ and NaF solutions and a NaF/CaF₂ varnish on human enamel subjected to hydrochloric acid erosion and tooth brush abrasion.

Methods

Forty enamel samples were prepared from human third molars and NaF (9500 ppm, pH 8.0), SnF₂ (9500 ppm, pH 2.6) solutions; Bifluorid10^® varnish (42,500 ppm, NaF 5%, CaF₂ 5%) and deionized water (control) was applied to the enamel. Following this three, six and nine cycles of erosion [1 cycle = erosion (0.01 M HCl, pH 2.2, 2 min) + artificial saliva (1 h, pH 7.0)] and erosion-abrasion [1 cycle = erosion (0.01 M HCl, pH 2.2, 2 min) + artificial saliva (1 h, pH 7.0) + abrasion (120 linear strokes in artificial saliva from Tepe medium soft brushes 200 g loading)] were carried out. The fluoride treated enamel was analysed using Knoop microhardness, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).

Results

For erosion alone, there was significantly less microhardness reduction in the Bifluorid10^® group after three and six cycles of erosion (P < 0.05), however no other groups showed statistically different hardness (P > 0.05). The EDS analysis showed that only the Bifluorid10^® group had any detectable fluorine following erosion and erosion-abrasion (0.1 wt.% and 0.2 wt.% fluorine respectively). The surface fluorine was found to have been removed after erosion and erosion-abrasion for all other surface treatments. Although precipitates were observed after application of the surface treatments, following erosion-abrasion, no visible surface effects from any fluoride preparation remained.

Conclusions

Enamel surface precipitates from application NaF, SnF₂ solutions appear to not be able to provide protection against gastric erosion and tooth brush abrasion. The NaF/CaF₂ varnish provided limited protection against erosion but the role for such varnishes in gastric erosion and tooth brush abrasion remains uncertain.     

Effect of stannous and fluoride concentration in a mouth rinse on erosive tissue loss in enamel in vitro

The aim of this in vitro study was to investigate the influence of stannous and fluoride ion concentrations in various experimental solutions on erosion progression in enamel. Human enamel specimens were subjected to a cyclic de- and remineralisation procedure for 10 days, with six demineralisation periods per day, of 5 min each. Erosive demineralisation was performed with 0.05 M citric acid (pH 2.3). Except in the control group, specimens were treated for 2 min with test solutions after the first and the sixth demineralisation. Test solutions were: 1500 mg/L F⁻ groups: group 1: 2800 mg/L Sn²⁺; group 2: 2100 mg/L Sn²⁺; group 3: 1400 mg/L Sn²⁺; group 4: 700 mg/L Sn²⁺; 1000 mg/L F⁻ groups: group 5: 2100 mg/L Sn²⁺; group 6: 1400 mg/L Sn²⁺. All preparations were adjusted to pH 4.5. Tissue loss was determined profilometrically after the last experimental day. As expected, the greatest tissue loss (μm, mean ± S.D.) was found in the control group (72.6 ± 11.5). All test solutions were able to reduce tissue loss significantly (p ≤ 0.001). The reduction of tissue loss by test solutions depended on the ratio of the tin concentration to the fluoride concentration. Lowest values were obtained by the application of the solutions of group 1 (7.8 ± 2.5) and group 5 (7.6 ± 5.2). Solutions with high concentrations of tin and fluoride are very effective in reducing erosive tissue loss, and their efficacy increased with increasing ratios of tin to fluoride concentrations.     

不同氟离子导入条件对牙本质小管的封闭作用

目的通过体外实验研究导人氟离子的不同条件对牙本质小管封闭的效果。方法制备牙本质模型45个,每组5个共9组,其中正常牙本质组仅用打磨处理,其余8组模型用6％柠檬酸酸蚀后,除1个脱矿组之外,7个再矿化组用NF-Ⅱ型护齿仪在不同的电流、时间利NaF浓度下进行氟离子导入处理。扫描电镜观察各组牙本质模型表面及纵断面的形貌,将观测结果进行统计分析;另外,对钙、磷元素含量进行能量色散X射线分析。结果脱矿组大部分牙本质小管开放,再矿化组牙本质小管内可见明显的矿化物沉积,各组的牙本质小管面积和相对面积有显著性差异（P〈0．05）;而能量色散X射线分析显示脱矿组与再矿化各组表面钙磷比无显著性差异（P〉0．05）。结论NF-Ⅱ型护齿仪的氟离子导入对于牙本质小管有一定封闭作用,在本实验条件下,牙本质再矿化的最佳电流为0．1mA或0．3mA,最佳时间为6min,最佳的NaF浓度为1％。     

含氟涂料和含氟牙膏对釉面再矿化和抗酸作用的实验研究

目的：观察含氟涂料与含氟牙膏对釉质表面再矿化和抗酸作用。方法：取牛恒切牙制备釉质片;统一酸蚀脱矿后随机分为4组（n＝3）;分别为生理盐水（A组对照）、Duraphat含氟涂料（B组）、Fluor Protector含氟涂料（C组）、含氟牙膏规律处理（D组）;处理期间标本置于人工唾液孵育2周;再次酸蚀;各阶段均用显微硬度仪测定釉面显微硬度、扫描电镜观察釉面,图像分析电镜下釉面微孔隙面积差异;统计分析。结果：首次酸蚀后釉面明显脱矿。分组处理2周,A组釉面再矿化不明显;B组和C组釉面形成涂料保护层;D组釉面可见明显再矿化。再次酸蚀后：A组和D组显微硬度下降,B组和C组涂料保护层有明显抗酸作用。再次酸蚀后,A组和D组釉面微孔隙面积增加（P＜0．05）,但D组小于A组（P＜0．05）;B组、C组无显著变化（P＞0．05）。结论：含氟涂料在釉面形成保护层,具有抗酸蚀和促进釉面再矿化作用;含氟牙膏能促进脱矿釉面再矿化,抗酸作用较弱。     

Pronamel and tooth mousse: an initial assessment of erosion prevention in vitro

OBJECTIVES: The aim of this study was to examine whether a single topical application of proenamel or tooth mousse would prevent enamel erosion METHODS: Enamel samples were treated with either proenamel or tooth mousse applied for 15 min. The control group was placed in distilled water for 15 min. All specimens were then exposed to an erosive challenge of 0.2% citric acid for 1h. Enamel loss was determined using surfometry. RESULTS: The mean amount of enamel removed in the control group was 5.02 microm (S.D. 1.16). The mean enamel loss in the proenamel group was 2.60 microm (S.D. 0.90) and the mean enamel loss in the tooth mousse group was 3.28 microm (S.D. 1.22). The results for the proenamel group were statistically significantly different from the control group at the p<0.01 level and the results for the tooth mousse group were statistically significantly different from the control group at the p<0.05 level. CONCLUSIONS: Tooth mousse and proenamel may offer a degree of protection from erosion of permanent enamel.     

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.     

Calcium lactate pre-rinse increased fluoride protection against enamel erosion in a randomized controlled in situ trial

Objectives

This in situ trial study was designed to evaluate whether calcium (Ca) pre-rinse would increase the fluoride (F) rinse protection against enamel erosion.

Methods

Fifteen volunteers participated in this split-mouth, 3-phase, crossover design study wearing a palatal appliance containing four sterilized bovine enamel slabs, for 10 days. In the 1st phase, five participants followed protocol A: daily rinse with a Ca lactate (CaL, 150 mmol/L, 1 min), followed by F (NaF 12 mmol/L, 1 min). Other five participants followed protocol B: daily rinse only with F, while the remainders followed protocol C: no rinse (negative control). Appliances were removed from the mouth and one side of the palatal appliance was exposed to a daily erosive challenge (0.05 M citric acid, 90 s); the other side served as control (deionized water – no erosion). In the 2nd phase volunteers were crossed over to other protocol and in the 3rd phase volunteers received the remaining protocol not yet assigned. Specimens were evaluated for surface loss using an optical profilometer.

Results

Repeated-measures three-way ANOVA (p = 0.009) and Tukey's test showed that CaL pre-rinse followed by NaF rinse significantly decreased surface loss of enamel when performed prior to an erosive challenge in comparison with the condition in which NaF only was used.

Conclusions

Pre-rinse with CaL may increase the protection exerted by NaF against erosive wear.     

Effects of fluoride concentration and temperature of milk on caries lesion rehardening

Objectives

The aim of the present in vitro study was to investigate the effects of fluoride concentration and temperature of milk on caries lesion rehardening under pH cycling conditions.

Methods

Incipient caries-like lesions were formed in human enamel specimens, characterized using Vickers surface microhardness (VHN) and assigned to seven treatment groups (n = 18 per group): fluoride was tested at five levels (0, 2.5, 5, 10, 20 mg/l, all 22 °C) and milk temperature at three levels (4, 22, 60 °C), but only for 10 mg/l F. Lesions were pH cycled for 15d (4×/daily 10 min milk treatments, 1×/daily 4 h acid challenge, remineralization in human/artificial saliva mixture). VHN of specimens were measured again and changes from lesion baseline were calculated. Subsequently, enamel fluoride uptake (EFU) was determined using the micro drill technique.

Results

Lesions responded to fluoride in a dose–response manner with higher fluoride concentrations resulting in more lesion rehardening (20 > 10 ≥ 5 ≥ 2.5 > 0 mg/l F). Furthermore, fluoridated milk at 60 °C was found to be more efficacious than at 4 °C (60 ≥ 22 > 4 °C). EFU results were similar (20 > 10 > 5 > 2.5 ≥ 0 mg/l F; 60 > 22 ≥ 4 °C).

Conclusions

Both fluoride concentration and milk temperature are likely to contribute to the anti-caries potential of fluoridated milk.     

An in vitro study of the distribution of silver and fluoride following application of 40 per cent silver fluoride solution to dentine

An in vitro test system involving application of 40 per cent silver fluoride solution to prepared cavities of moderate depth in extracted teeth failed to demonstrate the passage of significant amounts of fluoride into the dental pulp, despite a very high concentration of fluoride (100 000 ppm) in the applied solution. The test system used may not be conducive to quantitative investigation of ionic transfer because of disruptions to pulp circulation and fluid flow through dentine following tooth extraction. For this reason, the results are inconclusive as to whether or not application of 40 per cent silver fluoride as a cavity varnish or liner, and its use in the 'atraumatic' technique for treating deep caries, can be considered safe clinical procedures.     

Preventive effects of dentifrice containing 5000ppm fluoride against dental erosion in situ

Objective

To evaluate the effectiveness of a dentifrice with 5000 ppm fluoride in preventing dental erosion by orange juice in situ in comparison to a control dentifrice with 1450 ppm fluoride.

Methods

This was a double-blind and randomized clinical study with a cross-over design. Sixteen subjects wore an intra-oral appliance containing two enamel disks with an exposed surface of approximately 2 mm × 5 mm. Enamel disks in the study group were treated with a dentifrice with 5000 ppm fluoride and in the control group with 1450 ppm fluoride. The subjects rinsed with slurries of study dentifrices for one minute before immersing the enamel disks in 250 ml orange Juice four times in an 8-h period daily. The treatment procedure was repeated for three 5-day phases for each dentifrice. Enamel erosion was measured after each 5-day treatment phase using a focus-variation 3D scanning microscopy. Medians and inter-quartile ranges (IQR) of mean erosion depth were compared between the groups.

Results

The mean erosion depths of enamel varied greatly amongst the subjects. Enamel treated with 5000 ppm fluoride had less erosion (median 5.7 μm, IQR 4.5 μm) as compared to the control (median 12.6 μm, IQR 12.3 μm) after 15 days of fluoride treatment and erosive challenge cycles (p < 0.05).

Conclusions

Enamel treated with 5000 ppm fluoride had significantly improved resistance to erosion by orange juice. Periodic application of 5000 ppm fluoride may be beneficial in individuals at risk of acidic erosion associated with soft drink consumptions.     

Effect of TiF4, ZrF4, HfF4 and AmF on erosion and erosion/abrasion of enamel and dentin in situ

Objective

This in situ study aimed to analyse the impact of different tetrafluorides (TiF₄, ZrF₄ and HfF₄) and AmF on erosion and erosion plus abrasion of enamel and dentin.

Design

Ten volunteers took part in this crossover and double-blind study performed in 8 phases of each 3 days. In each phase, 2 bovine enamel and 2 dentin specimens were fixed in intraoral appliances. One enamel and one dentin sample were pretreated once with TiF₄, ZrF₄, HfF₄ or AmF (all 0.5 M F) for 60 s, while the other samples remained unfluoridated and served as control. Then, all samples were subjected to either erosion only (4 times/day, 90 s) or to erosion and abrasion (2 times/day, 30 s/sample). Toothbrushing abrasion was performed 90 min after the first and last erosion with an electrical toothbrush and fluoridated toothpaste at 1.2 N. After 3 days, enamel and dentin loss was assessed by profilometry (μm) and analysed by repeated measures ANOVA and paired t-test (p < 0.05).

Results

All fluoride solutions reduced enamel and dentin loss significantly compared to the controls. Generally, eroded samples showed less wear than eroded and abraded samples. The protective potential of the fluorides was not significantly different and was only slightly, but mostly not significantly, decreased by abrasion. The protective effect of the fluoride solutions was similar in enamel and dentin.

Conclusion

Tetrafluorides and AmF are able to reduce erosion and erosion plus abrasion in situ and are almost equally effective.     

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.     

体外应用氟化物对牙酸蚀症再矿化效果的评价-显微硬度测定

目的 用显微硬度测量法研究氟化物对碳酸饮料酸蚀后的乳牙釉质的再矿化作用.方法 收集临床拔除的滞留第二乳磨牙共16颗,制成牙釉质样本.经碳酸饮料浸泡,每天2次,每次10分钟,共5天后,分为对照组(A组)、2%氟化钠溶液组(B组)、含1.23%氟离子凝胶组(C组)和含低氟过饱和钙磷溶液矿化液组(含氟10ppm)(D组)四组,每组16个牙块.经不同的氟化物处理釉质表面,每天1次,每次2分钟,共5天.分别在酸蚀前、酸蚀后和再矿化后用显微硬度计测定釉质表面硬度.数据使用SPSS10.0统计软件包进行单因素方差分析(ANOVA).结果 饮料酸蚀后的牙釉质表面硬度值明显下降.与对照组相比,经2%氟化钠溶液和1.23%氟离子凝胶组处理后的牙釉质表面硬度值均比处理前显著上升(分别为P=0.031和P=0.017),这两组之间的差异无显著性;矿化液处理后的牙釉质表面硬度值无显著变化(P=0.894).结论 显微硬度测定实验显示高浓度的氟制剂2%氟化钠溶液和含1.23%氟离子凝胶能够显著地促进酸蚀釉质再矿化;低氟浓度矿化液在短时间内对酸蚀釉质再矿化作用不明显.