Rinsing with antacid suspension reduces hydrochloric acid-induced erosion

ObjectiveMouthrinsing with antacids, following erosive episodes, have been suggested as a preventative strategy to minimize tooth surface loss due to their neutralizing effect. The purpose of this in situ study was to evaluate the effect of an antacid suspension containing sodium alginate, sodium bicarbonate and calcium carbonate in controlling simulated erosion of enamel of intrinsic origin.DesignThe experimental units were 48 slabs (3 × 3 × 2 mm) of bovine enamel, randomly divided among 12 volunteers who wore palatal appliances with two enamel slabs. One of them was exposed extra-orally twice a day to 25 mL of a hydrochloric acid (HCl) solution (0.01 M, pH 2) for 2 min. There were two independent phases, lasting 5 days each. In the first phase, according to a random scheme, half of the participants rinsed with 10 mL of antacid suspension (Gaviscon^®, Reckitt Benckiser Healthcare Ltd.), while the remainder was rinsed with deionized water, for 1 min. For the second phase, new slabs were inserted and participants switched to the treatment not received in the first stage. Therefore, the groups were as follows: (a) erosive challenge with HCl + antacid suspension; (b) erosive challenge with HCl + deionized water (DIW); (c) no erosive challenge + antacid suspension; (d) no erosive challenge + DIW. Specimens were assessed in terms of surface loss using optical profilometry and Knoop microhardness. The data were analyzed using repeated measures two-way analysis of variance and Tukey’s tests.ResultsCompared to DIW rinses, surface loss of enamel was significantly lower when using an antacid rinse following erosive challenges (p = 0.015). The Knoop microhardness of the enamel was significantly higher when the antacid rinse was used (p = 0.026).ConclusionsThe antacid suspension containing sodium alginate, sodium bicarbonate and calcium carbonate, rinsed after erosive challenges of intrinsic origin, reduced enamel surface loss.     

Effect of an iron mouthrinse on enamel and dentine erosion subjected or not to abrasion: an in situ/ex vivo study

OBJECTIVES: This in situ/ex vivo study evaluated whether a rinse with an iron solution could reduce wear and the percentage of microhardness change of human enamel and dentine submitted to erosion followed by brushing after 1 or 30min. DESIGN: During 2 experimental 5-day crossover phases (wash-out period of 10 days), 10 volunteers wore intraoral palatal devices, with 12 specimens (6 of enamel and 6 of dentine) arranged in 3 horizontal rows (4 specimens each). In one phase, the volunteers immersed the device for 5min in 150mL of cola drink, 4 times a day. Immediately after immersion, no treatment was performed in one row. The other row was brushed after 1min using a fluoride dentifrice and the device was replaced into mouth. After 30min, the remaining row was brushed. In the other phase, the procedures were repeated, but after immersion the volunteers rinsed for 1min with 10mL of a 10mM ferrous sulphate solution. Changes in surface microhardness (%SMH) and wear (profilometry) of enamel and dentine were measured. Data were tested using ANOVA and Tukey's tests (p<0.05). RESULTS: The enamel presented more wear than dentine, under all experimental conditions. The iron solution caused a significant reduction on the %SMH in enamel, and a significant reduction on the wear in dentine, regardless the other conditions. CONCLUSIONS: Rinsing with an iron solution after an erosive attack, followed or not by an abrasive episode, may be a viable alternative to reduce the loss of dental structure.     

Protective effect of the in situ formed short-term salivary pellicle

Salivary pellicle, as previously investigated, protects the enamel surface after certain processes of maturation against the influence of acidic agents. The aim of the present study was to investigate the protective effect of the short-term salivary pellicle formed in situ over periods of 3, 60 and 120 min. Six human volunteers used intraoral acrylic splints with bovine enamel samples fixed at the buccal and palatal sites of the maxillary first molars and second premolars. Enamel specimens (n = 252) with and without pellicle were immersed for 60 s in 1.0% citric acid solution under agitation. Knoop surface hardness (KHN) of uneroded polished enamel was measured as a baseline and estimated immediately after erosive treatment reflecting the microhardness loss (DeltaKHN). The amounts of calcium dissolved from the eroded enamel surface were analysed by atomic absorption spectroscopy and scored in mg/l per 10 mm2 of enamel surface area. In addition, the scanning electron microscope was used for the micromorphological examination of the erosive alterations of the enamel surface. The average microhardness loss values after erosion of the enamel samples with buccally/palatally formed pellicle layers were measured as 139.1/144.9 DeltaKHN for 3 min pellicle, 145.9/146.9 DeltaKHN for 60 min pellicle and 141.7/138.6 DeltaKHN for 120 min pellicle. Calcium release values from the specimens with buccal/palatal pellicles were amounted to 15.0/14.9, 16.5/15.9 and 15.3/17.4 mg/l per 10 mm2 for 3, 60 and 120 min-old pellicles, respectively. No significant differences were related to the pellicle formation time and intraoral site (buccal or palatal) in all tested series (ANOVA, P < 0.05). However, significant protection of the enamel surface provided by the pellicle layer was observed on all pellicle-covered surfaces if compared to the non-covered enamel samples (calcium release: 25.6 mg/l per 10 mm2; microhardness loss 187.0 DeltaKHN). These data were in accordance with the morphologic alterations caused by citric acid on the pellicle-covered and pellicle non-covered specimens. It could be concluded that salivary pellicle formed in situ within a period of 3 min offers protection of enamel against citric acid. However, pellicle does not completely inhibit the erosive action of citric acid under the conditions of the present study.     

Effect of xylitol:sorbitol on fluoride enamel demineralization reduction in situ

OBJECTIVES: To evaluate if sugar alcohols would reduce enamel demineralization enhancing the fluoride (F) effect. METHODS: A crossover in situ study was conducted in four phases, during which 10 volunteers were submitted to one of the treatments: (I) Distilled and deionized water, as a negative control; (II) F (226 microg F/ml as NaF; concentration used in commercial mouthrinse); (III) X:S (xylitol:sorbitol 1:3; final concentration 1.6M; 28% of sugar alcohols) and (IV) F+X:S (same final concentration that groups II and III). The volunteers wore palatal appliances containing four bovine enamel blocks of known surface microhardness (SMH), covered with a 'test plaque' of mutans streptococci, which were immersed during 1 min in one of the allocated treatment solutions simultaneously that the volunteers rinsed their mouths with the same solution. After the rinsing the appliances were put in the mouth and after 20 min a cariogenic challenge was made with 20% sucrose solution during 1 min. After further 45 min the 'test plaque' was collected for F analysis, enamel SMH was again determined and the percentage of change in relation to baseline was calculated; F uptake in enamel was also determined. RESULTS: With respect to all the analyses made, the group F+X:S did not differ from the F treatment (p>0.05) and the groups treated with F and F+X:S differed from the negative control (p<0.05). CONCLUSIONS: The results suggest that xylitol:sorbitol may not enhance the effect of fluoride present in mouth rinse on the reduction of enamel demineralization.     

Remineralization effects of casein phosphopeptide-amorphous calcium phosphate crème on artificial early enamel lesions of primary teeth

International Journal of Paediatric Dentistry 2011 Background. Caries in children younger than 72 months is called early childhood caries (ECC). Sixty‐six per cent of Chinese children younger than 5 years old have dental decay, and about 97% of them are untreated. Aims. This in vitro study was conducted to evaluate the remineralization effects of the casein phosphopeptide‐amorphous calcium phosphate (CPP‐ACP) crème on the artificial early enamel lesions of the primary teeth and to assess its caries‐prevention efficiency. Design. Enamel specimens with artificial early lesions were produced and were then randomly divided into Group A: distilled and deionized water, DDW, as negative control; Group B: CPP‐ACP crème, test group; Group C: 500 ppm NaF solution, as positive control. The enamel surface microhardness (SMH) was measured before, after demineralization, and 30 days after remineralization. The results were analysed with the SPSS 13.0 software package. The enamel specimens were analysed by the scanning electron microscope. Results. The CPP‐ACP crème increased SMH of the eroded enamel significantly more than 500 ppm NaF solution did. The morphology of the enamel was different in each group. Conclusions. The CPP‐ACP crème is effective in remineralizing early enamel lesions of the primary teeth, a little more effective than 500 ppm NaF and can be used for the prevention of ECC.     

Enamel microhardness and bond strengths of self‐etching primer adhesives

Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self‐etching primer adhesives. Eur J Oral Sci 2010; 118: 191–196. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (μSBS). Buccal and lingual mid‐coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self‐etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One‐half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15‐s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37º°C, the μSBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min^?1 until bond failure occurred. The mean μSBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and μSBS. The weights used were the inverse of the variance of the μSBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the μSBS. These results suggest that the μSBS of the self‐etch adhesive systems are not influenced by enamel surface microhardness.     

Toothbrushing after an erosive attack: will waiting avoid tooth wear?

The purpose of this study was to determine if storage for up to 4 h in human saliva results in a decrease of erosive tooth wear (ETW) and in an increase of surface microhardness (SMH) of enamel samples after an erosive attack with subsequent abrasion. Furthermore, we determined the impact of individual salivary parameters on ETW and SMH. Enamel samples were distributed into five groups: group 1 had neither erosion nor saliva treatment; groups 2–5 were treated with erosion, then group 2 was placed in a humid chamber and groups 3–5 were incubated in saliva for 30 min, 2 h, and 4 h, respectively. After erosion and saliva treatments, all groups were treated with abrasion. Surface microhardness and ETW were measured before and after erosion, incubation in saliva, and abrasion. Surface microhardness and ETW showed significant changes throughout the experiment: SMH decreased and ETW increased in groups 2–5, regardless of the length of incubation in saliva. The results of groups 3–5 (exposed to saliva) were not significantly different from those of group 2 (not exposed to saliva). Exposure of eroded enamel to saliva for up to 4 h was not able to increase SMH or reduce ETW. However, additional experiments with artificial saliva without proteins showed protection from erosive tooth wear. The recommendation to postpone toothbrushing of enamel after an erosive attack should be reconsidered.     

Counteractive effect of antacid suspensions on intrinsic dental erosion

This in vitro study aimed to investigate the anti-erosive effect of antacid suspensions applied to enamel after exposure to hydrochloric acid (HCl). Ninety bovine enamel slabs were embedded, flattened, and polished. Reference areas were created and specimens were divided into six groups. They were exposed to 0.01 M HCl (pH 2) for 2 min, followed by immersion for 1 min in one of the following test suspensions: magnesium hydroxide, aluminum hydroxide, magnesium hydroxide/aluminum hydroxide, sodium alginate/sodium bicarbonate/calcium carbonate, or hydrated magnesium aluminate. Artificial saliva was used as a negative control. Specimens were subjected to a total of five cycles of erosion/antacid treatment. Enamel surface loss was measured (in micrometers) by optical profilometry. In addition, baseline and final surface microhardness (SMH) values of enamel were obtained. It was found that antacid suspensions significantly reduced enamel loss, and that similar protection was afforded by all formulations. No differences were observed between the final enamel SMH values among groups. Antacid suspensions counteracted HCl-induced enamel loss, although they were not effective in reducing enamel softening. Mouth rinsing with antacid suspensions after vomiting can potentially represent a promising strategy to counteract enamel loss caused by erosion.     

槲皮素对牙本质抗酸蚀性能的影响

目的评价槲皮素对人牙本质抗酸蚀性能的影响,为探寻理想的牙侵蚀症预防和治疗方案提供依据。方法选择福建医科大学附属口腔医院口腔颌面外科门诊提供的因正畸需要而拔除的人第三磨牙50颗,制备牙本质试件128个,用随机数字表法将试件随机分为8组(每组16个)。各组(每组选12个试件)分别用去离子水(对照组)、无水乙醇(对照组)、12.300 mg/L氟化钠、0.120 mg/L氯己定、0.183 mg/L表没食子儿茶素没食子酸脂(epigallocatechin gallate,EGCG)和0.075、0.150、0.300 mg/L槲皮素进行处理。每天37℃下用各组相应试剂浸泡试件2 min、去离子水冲洗并静置于人工唾液2 h后,使用柠檬酸(pH=2.45)进行4次酸蚀循环;连续7 d。分别检测试件酸蚀前后的表面显微硬度及表面轮廓(计算表面硬组织丧失量),用扫描电镜观察试件表面形貌。各组剩余4个试件用10%磷酸脱矿后干燥过夜,37℃下用各组相应试剂浸泡2 min,置于人工唾液中浸提7 d,检测浸提液中Ⅰ型胶原吡啶交联终肽(cross-linked carboxyterminal telopeptide of typeⅠcollagen,ICTP)含量。结果相比对照组,氯己定、槲皮素、EGCG均可显著抑制酸蚀循环引起的牙本质表面软化和硬组织丧失,0.300 mg/L槲皮素组试件酸蚀后表面显微硬度减小率最小[(8.75±4.95)%],表面硬组织丧失量最小[(2.26±1.16)μm],ICTP含量最低[(5.72±0.88)ng],均显著低于氯己定及EGCG组(P<0.05)。各槲皮素组表面硬组织丧失量和ICTP含量差异均无统计学意义(P>0.05);0.300 mg/L槲皮素组酸蚀后表面显微硬度减小率均显著小于0.075和0.150 mg/L槲皮素组(P<0.05)。结论槲皮素可显著提高人牙本质抗酸蚀性能,其中0.300 mg/L槲皮素的作用最佳。     

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 pH and acid concentration on erosive dissolution of enamel,dentine, and compressed hydroxyapatite

Shellis RP, Barbour ME, Jones SB, Addy M. Effects of pH and acid concentration on erosive dissolution of enamel, dentine, and compressed hydroxyapatite.
Eur J Oral Sci 2010; 118: 475–482. © 2010 Eur J Oral Sci The aims of this study were to determine the effects of pH and acid concentration on the dissolution of enamel, dentine, and compressed hydroxyapatite (HA) in citric acid solutions (15.6 and 52.1 mmol l^?1; pH 2.45, 3.2, and 3.9), using a pH‐stat system. After an initial adjustment period, the dissolution rates of enamel and HA were constant, while that of dentine decreased with time. The dissolution rate increased as the pH decreased, and this was most marked for enamel. To compare substrates, the rate of mineral dissolution was normalized to the area occupied by mineral at the specimen surface. For a given acid concentration, the normalized dissolution rate of HA was always less than that for either dentine or enamel. The dissolution rate for dentine mineral was similar to that for enamel at pH 2.45 and greater at pH 3.2 and pH 3.9. The concentration of acid significantly affected the enamel dissolution rate at pH 2.45 and pH 3.2, but not at pH 3.9, and did not significantly affect the dissolution rates of dentine or HA at any pH. The variation in response of the dissolution rate to acid concentration/buffer capacity with respect to pH and tissue type might complicate attempts to predict erosive potential from solution composition.     

Protective effect of the dental pellicle against erosive challenges in situ

The acquired dental pellicle helps prevent erosion, but the protection level is unknown. This in situ study tested whether a two-hour pellicle protects against different erosive challenges by orange juice. Subjects wore palatal appliances loaded with either enamel or dentin specimens. Pellicle was allowed to form, or not (control), on the surfaces of the specimens intra-orally for 2 hrs before the erosive challenges of 0 (control), 10, 20, and 30 minutes' duration. Specimens were randomly removed from the appliances after each challenge. Percentage of surface microhardness change (%SMC) was determined for the enamel specimens, and that of mineral loss and lesion depth for the dentin specimens. Enamel specimens with the pellicle showed a significantly lower %SMC, only after the 10-minute challenge. No protection was found for dentin. It was concluded that the acquired pellicle reduced dental erosion, but that this effect was limited to the less severe erosive challenge on enamel surfaces.     

Effect of casein phosphopeptide-amorphous calcium phosphate added to acidic beverages on enamel erosion in vitro

Background: To investigate, in vitro, the effect on enamel erosion of the addition of 0.2% w/v casein phosphopeptide‐amorphous calcium phosphate (CPP‐ACP) to four commercially‐available soft drinks, two of which were carbonated. Methods: Enamel specimens (n = 27) were sectioned from sound extracted human third molar teeth and polished to a mirror finish. Exposed enamel windows of 1 mm² were created by painting the surface with acid‐resistant nail varnish. Four citric flavoured soft drinks (pH range 2.2 to 2.4) and distilled deionized water (DDW) were tested. Each drink was tested with and without 0.2% CPP‐ACP w/v. The specimens were placed into 50 mL of solution at 37 °C for 30 minutes, rinsed and varnish removed. The samples were profiled with a white light profilometer and erosive depths recorded. Results: All soft drinks tested caused enamel erosion but adding 0.2% w/v CPP‐ACP significantly reduced (p <0.05) erosive depth in all test solutions in comparison with the solutions without CPP‐ACP. The erosive depths for all solutions with 0.2% CPP‐ACP did not differ significantly from those of DDW. Conclusions: Adding CPP‐ACP at 0.2% w/v significantly decreased the erosivity of all four soft drinks. The erosivity of the soft drinks with 0.2% CPP‐ACP added did not differ significantly from that of distilled water.     

In vitro microhardness studies on a new anti-erosion desensitizing toothpaste

OBJECTIVE: To evaluate in vitro the efficacy of a new anti-erosion desensitizing toothpaste to inhibit enamel surface softening by a dietary acid, and promote re-hardening of artificial erosive lesions. METHODOLOGY: The ability of the toothpaste to inhibit formation and promote repair of erosive lesions in human enamel has been investigated. In an enamel surface softening study, sound human enamel was pre-treated with one of four toothpaste slurries for two minutes, before exposure to 1.0% citric acid, pH 3.8, for a total of 30 minutes. The surface microhardness (SMH) of the specimens was determined at baseline and at 10-minute intervals using a Struers Duramin-1 microindentor. In an enamel re-hardening study, the erosive lesions were prepared by exposure of the specimens to 1.0% citric acid, pH 3.8, for 30 minutes. After two minutes treatment with a toothpaste slurry, lesion repair was monitored by SMH after 4, 24, and 48 hours incubation in artificial saliva. This remineralizing phase was modified by the addition of an aliquot of the relevant toothpaste slurry, to mimic in vivo carryover of the formulation. RESULTS: The new test formulation, Elmex Sensitive, and Colgate Sensitive exhibited statistically significant inhibition of citric acid-mediated enamel surface softening versus a fluoride-free placebo at all time points. The test toothpaste gave statistically superior protection against the erosive challenge compared to Elmex Sensitive and Colgate Sensitive after 20- and 30-minute exposures. In the remineralization studies, erosive lesions treated with the test toothpaste exhibited statistically superior re-hardening versus lesions treated with Elmex Sensitive and Colgate Sensitive after 24- and 48-hour incubation in the artificial saliva. Lesions treated with Elmex Sensitive re-hardened to a statistically significant extent versus the fluoride-free placebo toothpaste. A re-hardening study, in which a series of the new toothpaste-base formulations containing increasing concentrations of NaF were evaluated, showed a clear fluoride dose response. CONCLUSION: The present microhardness studies show that treatment with fluoride-containing toothpastes helps protect sound enamel from acid-mediated surface softening, and promotes re-hardening of erosive lesions. The new test toothpaste exhibited statistically superior efficacy to Elmex Sensitive and Colgate Sensitive in both in vitro models.     

奥乐V护牙剂对早期釉质龋再矿化作用的研究

目的 观察奥乐V护牙剂对早期釉质龋的再矿化作用。方法 将50个牛牙釉质块建立人工龋模型后随机分为5组：奥乐V护牙剂组、GC护牙素组、氟化钠（NaF）组、奥乐V护牙剂+NaF组、去离子水（DDW）组,分别进入 pH循环模型。采用显微硬度计测定各组标本脱矿前和pH循环后的釉质表面硬度值,扫描电镜观察各组再矿化后釉 质表面形态结构的改变。结果 各实验组经再矿化处理后其表面显微硬度均明显提高（P<0.001）,奥乐V护牙剂组再矿化后其表面显微硬度低于NaF组（P<0.001）,但与GC护牙素组间差异无统计学意义（P>0.05）;再矿化后奥乐V护牙剂组釉质表面有较大颗粒沉积。结论 奥乐V护牙剂具有促早期人工釉质龋再矿化的作用。     

Mechanism of action of tin‐containing fluoride solutions as anti‐erosive agents in dentine – an in vitro tin‐uptake,tissue loss,and scanning electron microscopy study

Ganss C, Hardt M, Lussi A, Cocks A‐K, Klimek J, Schlueter N. Mechanism of action of tin‐containing fluoride solutions as anti‐erosive agents in dentine – an in vitro tin‐uptake, tissue loss, and scanning electron microscopy study. Eur J Oral Sci 2010; 118: 376–384. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci Solutions containing tin and fluoride exhibit remarkable anti‐erosive properties with tin ions as a major agent. To elucidate its mechanism of action in dentine, the tin uptake on and in the tissue was investigated and related to histological findings and substance loss. Samples were treated twice daily, each treatment lasting for 2 min, with fluoride solutions [pH 4.5; 1,500 parts per million (p.p.m.) F] containing 2,100, 1,400, or 400 p.p.m. Sn as SnCl₂. In experiments 1 and 2, samples were eroded with citric acid (pH 2.3) six times each day, each treatment lasting for 5 min; in experiment 2, the demineralized organic matrix was continuously digested by collagenase; in experiment 3, no erosive challenges were performed. Sample surfaces and cross‐sections were investigated using energy dispersive X‐ray spectroscopy, scanning electron microscopy, and profilometry. Surface retention of tin was found in almost all treatment groups and was highest in experiment 2. On cross‐sections, tin was retained within the organic matrix; in mineralized areas, tin was found mainly within a depth of 10 μm. Test solutions inhibited substance loss significantly; in experiment 2, the effect was dose‐dependent. Erosion inhibition seemed to depend mainly on the incorporation of tin in the mineralized dentine when the organic portion was preserved, but on surface precipitation when the organic portion was continuously digested.     

Impact of fluoride, milk and water rinsing on surface rehardening of acid softened enamel. An in situ study

PURPOSE: To evaluate the impact of fluoride, milk and water rinsing on surface rehardening of acid softened enamel in situ. METHODS: Ten subjects performed six tests of4 hours each. In each test, three softened enamel samples were attached to intraoral appliances. For softening, samples were immersed extraorally in an acidic beverage for 120 seconds. Subsequently, specimens were worn intraorally for 5 minutes (Tests 1-3) or 30 minutes (Tests 4-6). Thereafter, the volunteers rinsed with a 250 ppm SnF2/Olaflur solution (Tests 1 and 4), milk (Tests 2 and 5) or non-carbonated mineral water (Tests 3 and 6) for 60 seconds. At each test, one sample was covered with tape during intraoral rinsing and thus, served as control. After rinsing, both test and the control samples were exposed to the oral cavity for up to 4 hours after demineralization. Surface microhardness (SMH) of the specimens was assessed at baseline, immediately after softening and 4 hours after softening. For each subject, the secretion rate of resting and stimulated saliva, buffering capacity and pH-value as well as calcium and phosphate concentration of saliva were measured. Statistical analysis was performed by ANCOVA followed by stratified analyses with Bonferroni correction. RESULTS: Baseline Knoop Hardness (mean +/- S.D.) amounted to 403.1 +/- 39.4. Immediately after softening, mean SMH was reduced to 214.4 +/- 24.1 KHN. Rinsing with 250 ppm fluoride, milk or water after 5 minutes or 30 minutes intraoral exposure of softened samples had a significant effect on rehardening. The increase of SMH (DeltaKHN) was highest after rinsing with fluoride (5 minutes: 95.0 +/- 18.3; 30 minutes: 94.2 +/- 24.3) followed by milk (5 minutes: 77.1 +/- 14.1; 30 minutes: 80.3 +/- 18.7) and water (5 minutes: 49.0 +/- 9.9; 30 minutes: 47.0 +/- 14.1), but did not achieve baseline values. It is concluded that a single rinse with a 250 ppm SnF2/Olaflur solution, milk or water increases rehardening of previously acid softened enamel.     

Low‐fluoride toothpaste and deciduous enamel demineralization under biofilm accumulation and sucrose exposure

Cury JA, do Amaral RC, Tenuta LMA, Del Bel Cury AA, Tabchoury CPM. Low‐fluoride toothpaste and deciduous enamel demineralization under biofilm accumulation and sucrose exposure. Eur J Oral Sci 2010; 118: 370–375. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci Because low‐fluoride toothpaste (500 p.p.m. F) has not clearly been shown to be effective for controlling caries in caries‐active children, this experimental in situ study was conducted to evaluate whether its effect, when compared with a conventional toothpaste (1,000–1,500 p.p.m. F), would depend on the cariogenic challenge. During four phases of 14 d each, 14 volunteers used 500 or 1,100 p.p.m. F toothpaste and wore palatal appliances containing deciduous enamel slabs, on which biofilm was accumulated and exposed to 20% sucrose solution at frequencies increasing from two to eight times per day. The F concentration was determined in the biofilm formed, and enamel demineralization was assessed by surface hardness loss (%SHL) and integrated area of hardness × lesion depth (ΔS). The F uptake by enamel was also determined. Fluoride in biofilm fluid and solids was statistically higher when conventional F toothpaste was used. The toothpastes did not differ statistically in terms of %SHL, ΔS, and F in enamel, but only the conventional F toothpaste significantly reduced caries‐lesion progression according to the frequency of sucrose exposure. The findings suggest that the high‐F availability in biofilm, resulting from the use of conventional toothpaste compared with low‐F toothpaste, may be important for reducing caries‐lesion progression in conjunction with a high frequency of sucrose exposure.     

Surface microhardness changes, enamel fluoride uptake, and fluoride availability from commercial toothpastes

OBJECTIVE: The aim of the present study was to evaluate the ability of a new fluoride-containing dentifrice to protect surface-softened enamel against further erosive challenges in an in vitro cycling model, and to relate any effects to enamel fluoride uptake (EFU) and free fluoride. METHODOLOGY: Human enamel specimens were subjected to a daily cycling regimen comprising: three two-minute treatments; five two-minute challenges using 1% citric acid pH 3.8; and remineralization in a mixture of human saliva and mucin-containing artificial saliva. Surface microhardness (SMH) was measured at baseline, 10, and 20 days, and the fluoride content of biopsied specimens determined at 20 days. EFU studies were based on method #40 described in the United States Food and Drug Administration (FDA) testing procedures. Free-fluoride availability was determined from slurries of one part toothpaste plus three parts deionized water. RESULTS: SMH showed that a 1150 ppm NaF test dentifrice protected enamel specimens greater than Crest Cavity Protection (1100 ppm NaF) and a fluoride-free placebo at both 10 days and 20 days (p < 0.05). The fluoride content of specimens treated with this prototype was higher than either Crest or the placebo. SMH for a 1450 ppm NaF test dentifrice was greater than for Elmex Sensitive (1450 ppm amine F) and placebo at 10 days, while both products were greater than the placebo at 20 days. The fluoride content of specimens treated with this test dentifrice was higher than Elmex Sensitive, which was higher than placebo. The fluoride uptake seen in the cycling model correlated for the NaF dentifrices with a standard EFU procedure. Different EFU results for a series of commercial dentifrices demonstrated that EFU is not necessarily a function of free-fluoride availability. CONCLUSION: This study demonstrated that fluoride dentifrices can increase the protection of enamel against an erosive challenge in vitro, and that the increased protection correlated with fluoride uptake. The fluoride uptake seen in the cycling model correlated with a standard FDA EFU procedure for the NaF dentifrices. The present studies demonstrate the importance of formulation effects on driving performance in in vitro models.