Effects of different treatments on chemical and morphological features of eroded dentin.

To evaluate the treatment of eroded dentin (Sensodyne Repair & Protect™, Er:YAG laser and combinations). The occlusal surfaces of 25 third molars were sectioned 1.5 mm in thickness. After an erosion cycle (5 min in demineralizing solution + 3 h in remineralizing solution; six cycles a day for 8 days), the samples were divided into five groups (n = 5): (E) erosion - control; (ES) erosion + Sensodyne Repair & Protect (NovaMin); (EL) erosion + Er:YAG laser (40 mJ, 10 Hz, 0.4 W, 50 µs, 3.1 J/cm2, 63 W/cm2); (ELS) erosion + Er:YAG laser + Sensodyne; and (ESL) erosion + Sensodyne + Er:YAG laser. Following storage in ultrapure water (37 °C/14 days), the Ca/P ratio was evaluated by EDXRF and the morphology surfaces examined in SEM. The percentage of exposed dentin tubules was calculated. One-way analysis of variance and Tukey's test at 5% were used to treat the data. The Ca/P ratio was higher in E and ES groups. More exposed dentin tubules were found in E group and less exposed tubules were found in the ES group (p < 0.0001). When the toothpaste and laser were combined, the number of occluded dentin tubules was higher when laser was performed first (ELS). A positive effect was found when the laser and toothpaste were combined.

A novel approach to study in situ enamel erosion and abrasion lesions.

OBJECTIVES: This study investigated previous hypotheses that the tongue can abrade acid softened/eroded enamel surfaces. METHODS: Twelve upper removable appliances each retaining 2 anterior and 2 posterior human enamel specimens were constructed. Each specimen was exposed to acid on both surfaces, but only one surface was allowed contact with the tongue. Therefore, 96 surfaces were assessed. Appliances were worn from 9.30 to 17.00 Monday to Friday for 22days. Acid eroded lesions were created by immersing the specimens for 5min in 50ml orange juice three times daily. Enamel loss was measured using Quantitative light- induced fluorescence (QLF) and Non- contact profilometry (NCLP) and the differences (D) between tongue (Dt) and palate facing (DP) surfaces determined. RESULTS: %ΔFD(t-p) from the two anterior specimens were greater than from those placed posteriorly with mean values of 15.9% (±9.1) and 14.4% (±8.4), 5.6% (±8.7) and 4.5% (±6.6) respectively. Similarly, NCLP data showed anterior specimens had greater differences for mean step height (MSH) between tongue- facing and the palate- facing (control) surfaces than posterior specimens. MSHD(t-p) values were 59.4µm (±30.3) for anterior tongue facing surfaces and 55.5µm (±29.4) for posterior palate facing surfaces. For the posterior specimens MSH was 48.1µm (±26.1) and 51.7µm (±30.4) respectively (p<0.05). CONCLUSION: The greater enamel surface loss of the anterior specimens demonstrates that abrasion by the tongue on acid softened/eroded enamel in situ is likely.

A randomised clinical trial to determine the abrasive effect of the tongue on human enamel loss with and without a prior erosive challenge.

OBJECTIVES: To investigate the abrasive effect of the tongue on human enamel loss with and without a prior dietary acid challenge in an in situ model. METHODS: A single centre, single blind, randomly allocated, split mouth, four treatment regimen, in situ study in healthy adult volunteers was undertaken. Twenty four subjects wore two lower intra-oral appliances each fitted with 4 human enamel samples 6h/day for 15 days. The samples were treated with either 50ml orange juice or water for 5min ex vivo 4x/day; prior to being licked or not licked with the subject's tongue for 60s. There were 2 samples per group per subject. Surface loss was measured by contact profilometry. RESULTS: 23 subjects completed the study with no adverse events. The mean loss of enamel at 15days was: 0.08µm for water without licking, 0.10µm with water and licking; 1.55µm with orange juice alone, 3.65µm with orange juice and licking. In the absence of erosive challenge, licking had no detectable effect on enamel loss p=0.28. Without licking, orange juice had a highly significant effect on loss compared to water, p<0.001. Erosive challenge followed by licking more than doubled the loss of enamel p<0.001. CONCLUSIONS: When enamel was exposed to orange juice prior to licking, tissue loss as a result of tongue abrasion of the eroded surface was increased, and double that of the erosive challenge alone. Licking enamel with the tongue had no perceptible effect on enamel loss in the absence of the erosive challenge. CLINICAL SIGNIFICANCE: Enamel wear resulting from tongue abrasion on tooth surfaces softened by acid challenge, can be an unavoidable consequence of oral function. This may account for the pattern of erosive toothwear on palatal and occlusal tooth surfaces, reinforcing the importance of restricting the frequency of dietary acid challenge in susceptible individuals.

Fluoride gel supplemented with sodium hexametaphosphate reduces enamel erosive wear in situ.

OBJECTIVE: This study evaluated the effect of fluoride gels, supplemented or not with sodium hexametaphosphate (HMP), on enamel erosive wear in situ. METHODS: Twelve healthy volunteers wore palatal appliances containing four bovine enamel discs. Subjects were randomly allocated into four experimental phases (double-blind, crossover protocol) according to the gels: Placebo (no fluoride or HMP), 1% NaF, 2% NaF, and 1% NaF+9% HMP. Enamel discs were selected after polishing and surface hardness analysis, and treated only once with the respective gels prior to each experimental phase. Erosion (ERO) was performed by extra-oral immersion of the appliance in 0.05M citric acid, pH 3.2 (four times/day, five minutes each, 5 days). Additional abrasion (ERO+ABR) was produced on only two discs by toothbrushing with fluoridated dentifrice after ERO (four times/day, 30s, 5 days). The specimens were submitted to profilometry and hardness analysis. The results were analyzed by two-way ANOVA and the Student-Newman-Keuls test (p<0.05). RESULTS: The 1% NaF+9% HMP gel promoted significantly lower enamel wear for ERO compared to the other groups, being statistically lower than 1% NaF and Placebo for ERO+ABR. Similarly, the lowest values of integrated lesion area were found for 1% NaF+9% HMP and 2% NaF, respectively, for ERO and ERO+ABR. CONCLUSION: The addition of HMP to the 1% NaF gel promoted greater protective effect against ERO and ERO+ABR compared to the 1% NaF gel, achieving similar protective levels to those seen for the 2% NaF gel. CLINICAL SIGNIFICANCE: Gel containing 1% NaF+9% HMP showed a high anti-erosive potential, being a safer alternative when compared to a conventional 2% NaF gel.

A spectroscopic and surface microhardness study on enamel exposed to beverages supplemented with lower iron concentrations.

OBJECTIVES: This study aimed to compare the in vitro mineral loss and surface microhardness (SMH) changes in human enamel specimens following supplementation of acidic carbonated beverages with low iron concentrations than when treated without. STUDY DESIGN: 180 enamel blocks each from primary and permanent teeth were prepared and equally subdivided (n=10) for their respective treatments in Group 1 (Coca Cola and Sprite without iron supplementation) and Group 2 (beverages supplemented with 2/5 mmol/L FeSO4.7H2O). Following initial SMH estimation, the blocks were subjected to 3 treatment cycles of 5/20 minute incubation periods, equally interspaced by a 5-min treatment in artificial saliva. The calcium and phosphate released after each cycle were analyzed spectrophotometrically and the final SMH was recorded. The results were tested using student's T test, One-way ANOVA and Kruskal Walli's test (p<0.05). RESULTS: Two and five mmol/L FeSO4.7H2O supplementation produced a highly significant SMH change and calcium and phosphate reduction than when treated without (p<.0005). Both the enamel specimens showed similar patterns of mineral loss and SMH reduction, with pronounced effects in the twenty minute incubation cycles. CONCLUSION: Our results suggest that 2 mmol/L FeSO4.7H2O supplementation to acidic beverages is beneficial in reducing mineral loss and preserving surface microhardness of human enamel.

Souakine mouth rinse solution protects deciduous enamel from simulated erosion in vitro.

AIM: To determine whether a souakine mouth rinse solution can provide protection of deciduous teeth against simulated erosion in vitro. MATERIALS AND METHODS: Thirty deciduous anterior teeth were used. Half of each tooth was covered with a varnish and teeth were randomly divided into a treated (S) and a control group (C). Each group was immersed in cola drink for 5 minutes and treated with an aqueous solution of Souakine (S) or water (C) for 2 minutes. The treatment was renewed 5 times a day for 8 days. Teeth were then embedded, sectioned and observed under polarised light microscope. Observed data were quantitatively analysed by SPSS software. RESULTS: In group (C), the unvarnished part of the enamel showed a deep green layer of erosion, compared to the varnished part. The difference in depth of this layer was significant (p<0.05). In group (S), the green layer of erosion was highly located in the unvarnished part as compared to the unvarnished part of the control group (C) (p<0.05). This layer of erosion was comparable to that in the varnished part, either in control or treated groups. CONCLUSION: The beneficial results of Souakine against erosion are validated either by a protective or a remineralisation effect.

Erosion protection by calcium lactate/sodium fluoride rinses under different salivary flows in vitro.

This study investigated the effect of a calcium lactate prerinse on sodium fluoride protection in an in vitro erosion-remineralization model simulating two different salivary flow rates. Enamel and dentin specimens were randomly assigned to 6 groups (n = 8), according to the combination between rinse treatments - deionized water (DIW), 12 mM NaF (NaF) or 150 mM calcium lactate followed by NaF (CaL + NaF) - and unstimulated salivary flow rates - 0.5 or 0.05 ml/min - simulating normal and low salivary flow rates, respectively. The specimens were placed into custom-made devices, creating a sealed chamber on the specimen surface connected to a peristaltic pump. Citric acid was injected into the chamber for 2 min, followed by artificial saliva (0.5 or 0.05 ml/min) for 60 min. This cycle was repeated 4×/day for 3 days. Rinse treatments were performed daily 30 min after the 1st and 4th erosive challenges, for 1 min each time. Surface loss was determined by optical profilometry. KOH-soluble fluoride and structurally bound fluoride were determined in specimens at the end of the experiment. Data were analyzed by 2-way ANOVA and Tukey tests (α = 0.05). NaF and CaL + NaF exhibited significantly lower enamel and dentin loss than DIW, with no difference between them for normal flow conditions. The low salivary flow rate increased enamel and dentin loss, except for CaL + NaF, which presented overall higher KOH-soluble and structurally bound fluoride levels. The results suggest that the NaF rinse was able to reduce erosion progression. Although the CaL prerinse considerably increased F availability, it enhanced NaF protection against dentin erosion only under hyposalivatory conditions.

Combined effect of a fluoride-, stannous- and chitosan-containing toothpaste and stannous-containing rinse on the prevention of initial enamel erosion-abrasion.

OBJECTIVES: The aim of this study was to assess the preventive effect of a fluoride-, stannous- and chitosan-containing (F/Sn/chitosan-) toothpaste (TP) on initial enamel erosion and abrasion. METHODS: In total, 150 human premolar enamel specimens were ground, polished and divided into 5 toothpaste/rinse groups (n=30): (G1) placebo-TP/tap water, (G2) sodium fluoride (NaF-) TP/tap water, (G3) F/Sn/chitosan-TP/tap water, (G4) F/Sn/chitosan-TP/Sn-rinse, (G5) NaF-TP/NaF-rinse. The 8-day erosion-abrasion cyclic treatment (one cycle/day) consisted of incubating the samples in artificial saliva (30min), then submitting the samples to toothbrush abrasion (2min incubation in toothpaste slurry; brushing with 20 toothbrush strokes) and rinsing (2min; 10ml) with the respective solution: tap water (G1-G3), Sn-rinse (G4) or NaF-rinse (G5). Afterwards, the samples were submitted to erosion (2min; 30ml 1% citric acid, pH=3.6). Surface microhardness (SMH) was measured initially and after every abrasion and erosion treatment. Enamel substance loss was calculated after each abrasion. Non-parametric ANOVA followed by Wilcoxon rank tests were used for analysis. RESULTS: G1 presented the greatest SMH decrease, while G4 presented the least SMH decrease (p<0.001). G3 had a similar SMH decrease to G2 and G5. Substance loss was significantly lower in G4 than all other groups (p<0.05), closely followed by G3. Both G2 and G5 showed similar calculated enamel substance loss to G1. CONCLUSION: The treatment with F/Sn/chitosan-TP and tap water provided a similar SMH decrease to both NaF-TP groups, but significantly lower substance loss. F/Sn/Chitosan-TP and Sn-rinse showed a better preventive effect, which promoted less SMH decrease and reduced substance loss. CLINICAL SIGNIFICANCE: The toothpaste containing fluoride, stannous and chitosan shows promising results in reducing substance loss from erosion and abrasion. The combination of this toothpaste with the stannous-containing rinse showed even better prevention against erosion-abrasion.

Development and evaluation of a low-erosive apple juice drink with Phosphoryl-Oligosaccharides of Calcium.

This study aimed to evaluate effectiveness of Phosphoryl-Oligosaccharides of Calcium (POs-Ca) added to apple juice on enamel erosion. Five juices were prepared by adding 0%, 0.5%, 1%, 1.5% or 2% POs-Ca to commercial apple juice, and subjected to Visual Analogue Scale (VAS) taste evaluation and pH and calcium/inorganic-phosphates analyses. To evaluate erosion, polished bovine enamel blocks were immersed in each juice for 5 or 60 min (n=20). Enamel surface loss (SL) and roughness (Ra) were also analyzed. VAS indicated acceptable taste for juices containing up to 1% POs-Ca. POs-Ca addition resulted in increased pH (3.61-3.88), calcium (0.95-25.10 mM), and inorganic-phosphate (1.77-20.44 mM). After 5 min, 0% juice resulted in significant erosion (p<0.05). However even after 60 min, no significant increase was found in Ra and SL compared to water (control) for 1.5-2% juices (p>0.05). Addition of 1-1.5% POs-Ca could significantly reduce enamel erosion by apple juice maintaining an acceptable taste.

Effect of safflower oil on the protective properties of the in situ formed salivary pellicle.

AIM: The prevalence of dental erosion is still increasing. A possible preventive approach might be rinsing with edible oils to improve the protective properties of the pellicle layer. This was tested in the present in situ study using safflower oil. METHODS: Pellicle formation was carried out in situ on bovine enamel slabs fixed buccally to individual upper jaw splints (6 subjects). After 1 min of pellicle formation subjects rinsed with safflower oil for 10 min, subsequently the samples were exposed in the oral cavity for another 19 min. Enamel slabs without oral exposure and slabs exposed to the oral cavity for 30 min without any rinse served as controls. After pellicle formation in situ, slabs were incubated in HCl (pH 2; 2.3; 3) for 120 s, and kinetics of calcium and phosphate release were measured photometrically (arsenazo III, malachite green). Furthermore, the ultrastructure of the pellicles was evaluated by transmission electron microscopy (TEM). RESULTS: Pellicle alone reduced erosive calcium and phosphate release significantly at all pH values. Pellicle modification by safflower oil resulted in an enhanced calcium loss at all pH values and caused an enhanced phosphate loss at pH 2.3. TEM indicated scattered accumulation of lipid micelles and irregular vesicle-like structures attached to the oil-treated pellicle layer. Acid etching affected the ultrastructure of the pellicle irrespective of oil rinsing. CONCLUSION: The protective properties of the pellicle layer against extensive erosive attacks are limited and mainly determined by pH. The protective effects are modified and reduced by rinses with safflower oil.

Prevention of toothbrushing abrasion of acid-softened enamel by CO(2) laser irradiation.

OBJECTIVE: The aim of the present study was to evaluate the effect of CO(2) laser irradiation (10.6µm) at 0.3J/cm(2) (0.5µs; 226Hz) on the resistance of softened enamel to toothbrushing abrasion, in vitro. METHODS: Sixty human enamel samples were obtained, polished with silicon carbide papers and randomly divided into five groups (n=12), receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C). After surface treatment they were submitted to a 25-day erosive-abrasive cycle in 100ml sprite light (90s) and brushed twice daily with an electric toothbrush. Between the demineralization periods samples were immersed in supersaturated mineral solution. At the end of the experiments enamel surface loss was determined using a contact profilometer and morphological analysis was performed using scanning electron microscopy (SEM). For SEM analysis of demineralization pattern, cross-sectional cuts of cycled samples were prepared. The data were statistically analysed by one-way ANOVA model with subsequent pairwise comparison of treatments. RESULTS: Abrasive surface loss was significantly lower in all laser groups compared to both control and fluoride groups (p<0.0001 in all cases). Amongst the laser groups no significant difference was observed. Softened enamel layer underneath lesions was less pronounced in laser-irradiated samples. CONCLUSION: Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5µs, 226Hz) either alone or in combination with amine fluoride gel significantly decreases toothbrushing abrasion of softened-enamel, in vitro.

Roughness and pH changes of enamel surface induced by soft drinks in vitro-applications of stylus profilometry, focus variation 3D scanning microscopy and micro pH sensor.

This study aimed to evaluate enamel surface roughness (Ra) and pH before and after erosion by soft drinks. Enamel was exposed to a soft drink (cola, orange juice or green tea) for 1, 5 or 60 min; Ra was measured using contact-stylus surface profilometry (SSP) and non-contact focus variation 3D microscope (FVM). Surface pH was measured using a micro pH sensor. Data were analyzed at significance level of alpha=0.05. There was a significant correlation in Ra between SSP and FVM. FVM images showed no changes in the surface morphology after various periods of exposure to green tea. Unlike cola and orange juice, exposure to green tea did not significantly affect Ra or pH. A significant correlation was observed between surface pH and Ra change after exposure to the drinks. Optical surface analysis and micro pH sensor may be useful tools for non-damaging, quantitative assessment of soft drinks erosion on enamel.

Preventing erosion with novel agents.

OBJECTIVES: This in vitro study aimed to investigate the protective effect of four commercial novel agents against erosion. METHODS: Ninety human molars were distributed into 9 groups, and after incubation in human saliva for 2 h, a pellicle was formed. Subsequently, the specimens were submitted to demineralization (orange juice, pH 3.6, 3 min) and remineralization (paste slurry containing one of the tested novel agents, 3 min) cycles, two times per day, for 4 days. The tested agents were: (1) DenShield Tooth; active ingredient: 7.5% W/W NovaMin(®) (calcium sodium phosphosilicate); (2) Nanosensitive hca; active ingredient: 7.5% W/W NovaMin(®); (3) GC Tooth Mousse; active ingredient: 10% Recaldent™ (CPP-ACP); (4) GC MI Paste Plus; active ingredients: 10% Recaldent™, 900 ppm fluoride. Two experimental procedures were performed: in procedure 1, the tested agents were applied prior to the erosive attack, and in procedure 2 after the erosive attack. A control group receiving no prophylactic treatment was included. Surface nanohardness (SNH) of enamel specimens was measured after pellicle formation and after completion of daily cyclic treatment. RESULTS: SNH significantly decreased at the end of the experiment for all groups (p<0.05). In both procedures, there was no statistically significant difference between the control group and those treated with paste slurries (p>0.05). In addition, the changes in SNH (ΔSNH=SNHbaseline-SNHfinal) did not show statistically significant difference between both procedures (p>0.05). CONCLUSION: Tooth erosion cannot be prevented or repaired by these novel agents, regardless of fluoride content.

In vitro alterations in dental enamel exposed to acidic medicines.

OBJECTIVE: To evaluate the effect of acidic medicines (Klaricid(®), Claritin(®), and Dimetapp(®)) on surface enamel in vitro. METHODS: Enamel blocks (n=104) were randomly distributed into two groups: G1 (pH-cycling simulating physiological oral conditions) and G2 (erosive conditions). Each group was divided into four subgroups, three to be immersed in the medicines and the control in deionized water. Specimen surfaces were evaluated for roughness and hardness at baseline and again after the in vitro experimental phase, which included 30 min immersions in the medicines twice daily for 12 days. Scanning electron microscopy (SEM) was also performed after the in vitro experimental phase. RESULTS: All medicines produced a significant reduction in hardness in G1 after 12 days (P<0.05). The three medicines promoted greater roughness after both pH-regimens - G1 and G2 (P<0.01), except for Claritin in G1. Scanning electron microscopy analysis showed erosive patterns in all subgroups. Dimetapp(®) showed the most erosion and Klaricid(®) the least, in both groups. CONCLUSION: Dimetapp(®) (lowest pH and viscosity) and deionized water (control) showed the most pronounced erosive patterns. Klaricid(®) (highest pH and viscosity) presented an in vitro protective effect against acid attacks perhaps due to its mineral content and viscosity.

Effects of 1.23% acidulated phosphate fluoride gel and drinkable yogurt on human enamel erosion, in vitro.

OBJECTIVES: In this in vitro study, the authors sought to determine the effects of 1.23% acidulated phosphate fluoride gel (APF) or drinkable yogurt on human enamel after exposure to an acidic drink. METHOD AND MATERIALS: Sixteen surgically removed, caries-free, human third molars were cut into four portions: mesial, distal, buccal, and lingual. Each portion was distributed into one of four groups, with each specimen embedded in acrylic resin and its enamel center lightly ground and polished. Three groups of specimens were immersed in orange juice for 2 minutes. One group received no other treatment (OR), one group was subsequently immersed in drinkable yogurt for 5 minutes (OR:YO), while another group had 1.23% APF applied for 4 minutes (OR:APF). The final group was immersed in only drinkable yogurt for 5 minutes (YO). Each exposure was performed twice daily for 60 days; between exposures, the samples were stored in artificial saliva. The enamel surfaces were monitored by three criteria: erosion depth, surface hardness, and SEM. RESULTS: Erosion depth increased progressively in all groups. Surface microhardness progressively decreased in all groups except the OR:APF group, where hardness was significantly higher than other groups at 60 days (P < .05). SEM inspection revealed preferential loss of rod crystallites with retention of interrod crystallites in all specimens exposed to orange juice. The enamel exposed to only drinkable yogurt revealed modest and uniform etching. CONCLUSION: Drinkable yogurt alone or posttreatment of enamel after exposure to an acidic drink with either 1.23% APF or drinkable yogurt leads to enamel dissolution and does not reduce enamel erosion, in vitro.

Influence of peroxide treatment on bovine enamel surface--cross-sectional analysis.

Carbamide peroxide and hydrogen peroxide are used as the main agents in vital tooth bleaching. In this study, the influence of peroxide treatment on cross-sectional morphology and mechanical property was investigated. A 3 x 5-mm window of enamel on the labial surface of a bovine tooth was exposed to immersion in 10% or 30% carbamide peroxide or hydrogen peroxide for 30 or 180 min. After immersion, the cross-sectional structure of each specimen was examined by nanoindentation and SEM. Nanohardness in the enamel showed a decrease at 2 microm below the surface, but none at 50 microm. High concentrations of peroxide caused erosion to a depth of 5 microm below the surface. In conclusion, decrease in nanohardness and change in morphology were limited to an area less than 50 microm below the surface, regardless of either concentration of peroxide or period of immersion.

TiF(4) and NaF at pH 1.2 but not at pH 3.5 are able to reduce dentin erosion.

OBJECTIVE: This study aimed to analyse and compare the protective effect of buffered (pH 3.5) and native (pH 1.2) TiF(4) in comparison to NaF solutions of same pH on dentin erosion. DESIGN: Bovine samples were pretreated with 1.50% TiF(4) or 2.02% NaF (both 0.48M F) solutions, each with a pH of 1.2 and 3.5. The control group received no fluoride pretreatment. Ten samples in each group were eroded with HCl (pH 2.6) for 10x60s. Erosion was analysed by determination of calcium release into the acid. Additionally, the surface and the elemental surface composition were examined by scanning electron microscopy (two samples in each group) and X-ray energy-dispersive spectroscopy in fluoridated but not eroded samples (six samples in each group). Cumulative calcium release (nmol/mm(2)) was statistically analysed by repeated measures ANOVA and one-way ANOVA at t=10min. RESULTS: TiF(4) and NaF at pH 1.2 decreased calcium release significantly, while TiF(4) and NaF at pH 3.5 were not effective. Samples treated with TiF(4) at pH 1.2 showed a significant increase of Ti, while NaF pretreatment increased F concentration significantly. TiF(4) at pH 1.2 led to the formation of globular precipitates occluding dentinal tubules, which could not be observed on samples treated with TiF(4) at pH 3.5. NaF at pH 1.2 but not at pH 3.5 induced the formation of surface precipitates covering dentinal tubules. CONCLUSION: Dentin erosion can be significantly reduced by TiF(4) and NaF at pH 1.2, but not at pH 3.5.

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 degrees 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 microl of 1M 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 microm (SD 2.5 microm) and further enamel softening of 2.4 microm (SD 1.5 microm). 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.

Effects of tooth whitening and orange juice on surface properties of dental enamel.

OBJECTIVE: To study the effects of 6% H2O2 activated with LED light on surface enamel as compared to orange juice challenges in vitro. METHODS: A total of 40 human enamel discs were incubated in saliva overnight to allow pellicle formation and then divided into three groups: 15 for whitening treatments, 15 for orange juice immersions and 10 for normal saline controls. Baseline microhardness was measured with a microhardness Knoop indenter (50g, 10s) and surface topography was evaluated with a focus-variation 3D scanning microscopy. Enamel discs were treated with H2O2 or orange juice for 20 min each cycle for five cycles to simulate daily treatment with the products for 5 days. The discs were stored in saliva between treatment cycles. Microhardness and surface topography were evaluated again after treatments. Changes in microhardness and in surface area roughness (Sa), mean maximum peak-to-valley distance (Sz) and the developed surface area ratio (Sdr) were compared before and after treatments (t-test) and among groups (ANOVA). RESULTS: Enamel surface hardness decreased by 84% after orange juice immersion but no statistically significant changes were observed in the whitening and control groups. Surface topography changed significantly only in the orange juice group as shown by increased Sa (1.2 microm vs. 2.0 microm), Sz (7.7 microm vs. 10.2 microm) and Sdr (2.8% vs. 6.0%). No such changes were observed in the whitening and control groups. CONCLUSION: In comparison to orange juice challenges, the effects of 6% H2O2 on surface enamel are insignificant. Orange juice erosion markedly decreased hardness and increased roughness of enamel.

In situ enamel morphology evaluation after acidic soft drink consumption: protection factor of contemporary toothpaste.

OBJECTIVE: The enamel erosion induced by acidic soft drinks is an increasingly important problem. The aim of this study was to investigate the effect of soft drinks on enamel erosion and the protection offered by representative modern toothpastes using a new 'in situ scanning electron microscopy (SEM)-replica technique'. METHODS: Six patients were selected to receive in vivo enamel replicas, fabricated with a polyvinyl-siloxane/polyether impression material. Scanning electron microscopy was used to evaluate the morphology of enamel surface before and after exposure to lemon juice and SPRITE. The protective effectiveness of toothpaste was further evaluated with the same method. Furthermore, to validate the effectiveness of the in situ SEM-replica technique, we compared it to a direct in vitro SEM investigation on extracted teeth. RESULTS: Scanning electron microscopy investigation of the in situ replicas showed severe enamel morphology alterations after acidic soft drink exposure. On the other hand, it was also showed the protective effectiveness of toothpaste in preventing enamel erosion induced by acidic soft drinks. The direct in vitro SEM investigation provided similar enamel erosion results and proved the effectiveness of the in situ SEM-replica technique. CONCLUSION: Acidic soft drinks induce enamel erosion but regular use of toothpaste might reduce the risk for enamel erosion. The in situ SEM-replica technique provides an accurate method for tracing enamel morphology alterations and erosion induced by acidic soft drinks.