Changes In Surface Microhardness Research Articles

Effect of commercial alcoholic drinks on sound enamel surface of bovine teeth

Copyright © 2013 by Journal of Korean Academy of Oral Health This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives: The purpose of this study was to evaluate the change in surface microhardness of sound enamel of bovine teeth due to commercial alcoholic drinks. Methods: The experiment group comprised of wines, makgeollis, and beers with low pH, while distilled water was used as the control. The two experiment groups were administered soju having the highest (SojuH) and lowest (SojuL) pH. Drinking wines were classified into 2 groups: agitated (wine A) and nonagitated (wine NA) wines. The pH values, buffering capacity, and concentrations of fluorine, calcium, and phosphorus of both the wine groups were measured. Eighty-four bovine specimens were divided into seven groups (N=12) and were immersed for 1, 3, 5, 10, 30, 60, and 120 min, respectively. The surface microhardness was measured using a microhardness tester before and after treatment with each alcoholic drink. After 120 min, the enamel surface was examined using a scanning electron microscope (SEM). The statistical methods used in this study were one-way analysis of variance (ANOVA) and repeated-measure ANOVA. Results: The differences in the surface microhardness (∆VHN) values obtained before and after treatment for 120 min were statistically significant among groups. Makgeolli, wine A, and wine NA significantly eroded the enamel after 120 min. However, sojuH and sojuL had an effect similar to that of distilled water, which was used in the control group. Beer caused slight enamel erosion. SEM images revealed that makgeolli, wine A, and wine NA caused significant erosion of the enamel surface, while beer caused slight erosion. SEM observation results were similar to those obtained after surface microhardness evaluation. Conclusions: The study findings suggest that alcoholic drinks, such as makgeolli and wine, with organic acids and a pH value less than 4.0 can cause tooth enamel erosion. Therefore, alcoholic drinks with low pH values and organic acid composition should not be retained for long periods in the mouth.

Effect of low pH on surface rehardening efficacy of high concentration fluoride treatments on non-cavitated lesions

ObjectiveProfessionally applied acidulated phosphate fluoride has been shown to reduce caries incidence. However, it has been suggested that its efficacy might be reduced in advanced non-cavitated lesions. This study aimed to compare the surface rehardening and fluoride uptake effect of 2%-NaF solutions at different pH on non-cavitated caries-like lesions with two different levels of demineralization. MethodsHuman enamel specimens were demineralized to create early and advanced non-cavitated lesions. Specimens for each type of lesion were divided into 3 groups, treated for four minutes with either 2%-NaF pH 3.5, 2%-NaF at pH 7.0, or neutral deionized water, and exposed to a pH cycling remineralization/demineralization model for five days. An additional treatment was then done as described above followed by five more days of cycling (total of 2 treatments, ten-day pH cycling). Specimens were analyzed for surface microhardness change and fluoride uptake. ResultsIt was found that for both types of lesions, acidic pH fluoride treatment was significantly (p<0.05) more effective than neutral pH treatment in rehardening the lesion surface and promoting fluoride uptake. Furthermore, the low pH vs neutral pH difference in rehardening was significantly larger in the less demineralized lesions (p=0.0001). Water treatment resulted in no rehardening or fluoride uptake. ConclusionsResults from this study suggest that high concentration fluoride treatments at acidic pH are more effective in rehardening the surface of non-cavitated caries lesions and promoting fluoride uptake than those at neutral pH. This effect appears to be greater in less demineralized lesions when compared to more advanced ones. Clinical significanceThe results of this investigation suggest that when no other attenuating circumstances are present (e.g., the possibility of damaging tooth-coloured restorations), high concentration fluoride treatments for high risk individuals might be more efficacious using products at low pH.

Effect of Psidium cattleianum leaf extract on enamel demineralisation and dental biofilm composition in situ

ObjectivePrevious evaluations of Psidium cattleianum leaf extract were not done in conditions similar to the oral environment. The aim of this study was to evaluate the effect of P. cattleianum leaf extract on enamel demineralisation, extracellular polysaccharide formation, and the microbial composition of dental biofilms formed in situ. DesignTen volunteers took part in this crossover study. They wore palatal appliances containing 4 enamel blocks for 14days. Each volunteer dripped 20% sucrose 8 times per day on the enamel blocks. Twice a day, deionised water (negative control), extract, or a commercial mouthwash (active control) was dripped after sucrose application. On the 12th and 13th days of the experiment, plaque acidogenicity was measured with a microelectrode, and the pH drop was calculated. On the 14th day, biofilms were harvested and total anaerobic microorganisms (TM), total streptococci (TS), mutans streptococci (MS), and extracellular polysaccharides (EPS) were evaluated. Enamel demineralisation was evaluated by the percentage change of surface microhardness (%ΔSMH) and integrated loss of subsurface hardness (ΔKHN). The researcher was blinded to the treatments during data collection. ResultsThe extract group showed lower TM, TS, MS, EPS, %ΔSMH, and ΔKHN values than the negative control group. There were no differences between the active and negative control groups regarding MS and EPS levels. There were no differences in pH drop between the extract and active control groups, although they were significantly different from the negative control group. For all other parameters, the extract differed from the active control group. ConclusionPsidium cattleianum leaf extract exhibits a potential anticariogenic effect.

In situ Evaluation of the Erosive Potential of Orange Juice Modified by Food Additives

The aim of this study was to evaluatethe erosive potential of orange juice modified with food-approved additives: 0.4 g/l of calcium (Ca) from calcium lactate pentahydrate, 0.2 g/l of linear sodium polyphosphate (LPP) or their combination (Ca+LPP) were added to a commercially available orange juice (negative control, C–). A commercially available calcium-modified orange juice (1.6 g/l of calcium) was the positive control (C+). These juices were tested using a short-term erosion in situmodel, consisting of a five-phase, single-blind crossover clinical trial involving 10 subjects. In each phase, subjects inserted custom-made palatal appliances containing 8 bovine enamel specimens in the mouth and performed erosive challenges for a total of 0 (control), 10, 20, and 30 min. Two specimens were randomly removed from the appliances after each challenge period. Enamel surface microhardness was measured before and after the clinical phase and the percentage of surface microhardness change (%SMC) was determined. Before the procedures, in each phase, the subjects performed a taste test, where the juice assigned to that phase was blindly compared to C–. Overall, C+ showed the lowest %SMC, being the least erosive solution (p < 0.05), followed by Ca+LPP and Ca, which did not differ from each other (p > 0.05). LPP and C– were the most erosive solutions (p < 0.05). Taste differences were higher for C+ (5/10 subjects) and Ca (4/10 subjects), but detectable in all groups, including C– (2/10 subjects). Calcium reduced the erosive potential of the orange juice, while no protection was observed for LPP.

Effect of the simulated body fluid containing bleaching agent on the hypersensitivity and surface microhardness of the tooth

In this study, the whitening effect of simulated body fluid (SBF) and side effects of a hydrogen peroxide (H 2O 2) as the bleaching treatment of tooth enamel surfaces was investigated. H 2O 2 solution of 25% and 30% was prepared by diluting the commercially available 35% H 2O 2 solution with either distilled water (DW) or SBF of 1×, 3×, and 5× concentrations. These diluted H 2O 2 solutions were applied to the dental enamel surface of eighty human premolars for 15 min, followed by rinsing with DW. The procedure was repeated 4 times. The changes in color and surface microhardness before and after the bleaching procedure were recorded. The enamel surfaces of bleached teeth were examined with SEM. The results indicated that the brightness and microhardness of the tooth surface increased after bleaching with the SBF diluted agent compared to teeth treated with the DW diluted agent. These results might be due to the deposition of bone-like apatite that was observed with SEM. This bone-like apatite fills the area of roughness and holes in the enamel surfaces that were caused by bleaching, and created smoother and harder enamel surfaces. The result of this study suggested that a bleaching agent comprised of hydrogen peroxide and SBF would prevent the destructive side effects of bleaching and increase surface microhardness as well as having a whitening effect.

The addition of nano-sized hydroxyapatite to a sports drink to inhibit dental erosion— In vitro study using bovine enamel

Objectives This study examined the dental erosion and demineralization potential of a sports drink containing nano-sized hydroxyapatite (nano-HA) as an additive. Methods The experimental solutions were Powerade (PA) alone and PA with 0.05%, 0.10%, and 0.25% nano-HA. The pH, titratable acidity, and calcium and phosphate content of each solution were analysed, and the degree of saturation with respect to the dental enamel (DS En) was obtained. Twelve sound bovine enamel specimens for each group were treated in accordance with the pH-cycling schedule which had 60 min treatment with experimental solution per day for 7 days. The erosion potential was determined from the changes in surface micro hardness (SMH), the depths of erosion and demineralized layer using confocal laser scanning microscopy (CLSM), and the morphological changes to the tooth surface were examined with scanning electron microscopy (SEM) after pH-cycling. Results pH and DS En increased with increasing nano-HA concentration in the drinks, whereas the titratable acidity decreased. There were significant differences in the SMH between the PA alone and >0.10% nano-HA groups ( p < 0.001). Although the PA alone group showed a pronounced erosion depth, CLSM showed no erosion depth in 0.25% nano-HA group. SEM showed an intact surface with increasing nano-HA concentration in the drinks. In conclusion, dental erosion was effectively prevented with increase of adding concentration of nano-HA, and a sports drink containing 0.25% nano-HA might prevent dental erosion.

Development of an orange juice surrogate for the study of dental erosion

The aim of this study was to create a synthetic juice (SJ) to be used as a surrogate for natural orange juices in erosion studies, verifying its erosive potential. The SJ was formulated based on the chemical composition of orange juices from different locations. Forty enamel and 40 root dentin specimens were randomly assigned into 4 experimental groups (n = 10): SJ; 1% Citric Acid (CA); Minute Maid Original® (MM) and Florida Natural Original® (FN). The specimens were immersed in their respective solutions for 5 min, 6x/day for 5 days, in an erosion-remineralization cycling model. Enamel specimens were analyzed by surface Knoop microhardness and optical profilometry and dentin specimens only by optical profilometry. Outcomes were analyzed statistically by ANOVA followed by Tukey's test considering a significance level of 5%. For enamel, the surface loss and microhardness changes found for MM and SJ groups were similar (p>0.05) and significantly lower (p<0.01) than those found in the CA group. For dentin, CA promoted significantly greater (p<0.01) surface loss compared with all the other groups. No significant difference (p>0.05) was observed in dentin surface loss between MM and SJ. In conclusion, CA was the most erosive solution, and SJ had a similar erosive potential to that of MM natural orange juice.

Electrical Contact Resistance in Thin $({\leq}{\rm 0.5}~\mu{\rm m})$ Gold Plated Contacts: Effect of Gold Plating Thickness

This paper describes the electrical contact resistance (ECR) measurements made on thin gold plated (gold plating of ≤ 0.5 μm with a Ni underlayer of ~2 μm) oxygen free high conductivity (OFHC) Cu contacts in vacuum environment. ECR in gold plated OFHC Cu contacts is found to be slightly higher than that in bare OFHC Cu contacts. Even though gold is a softer material than copper, the relatively high ECR values observed in gold plated contacts are mainly due to the higher hardness and electrical resistivity of the underlying Ni layer. It is well known that ECR is directly related to plating factor, which increases with increasing coating thickness when the electrical resistivity of coating material is more than that of substrate. Surprisingly, in the present case it is found that the ECR decreases with increasing gold layer thickness on OFHC Cu substrate (gold has higher electrical resistivity than OFHC Cu). It is analytically demonstrated from the topography and microhardness measurements results that this peculiar behavior is associated with thin gold platings, where the changes in surface roughness and microhardness with increasing layer thickness overshadow the effect of plating factor on ECR.

Comparing Different Methods to Assess Erosive Lesion Depths and Progression in vitro

The aim of this study was to compare the precision and accuracy of 5 different methods applied to assess surface substance loss or changes in surface microhardness (SMH) on the same enamel surfaces after repeated acid exposures. Ground specimens from human molars were exposed to 0.01 M HCl (pH 2.2) for 6 min × 2 and measurements performed 3 times to estimate precision. The accuracies (systematic errors) were calculated against the manufacturer’s calibration standard. Lesion depth progression was from 94 to 110%, related to repeated acid exposure. The precisions/accuracies were: WLI (white light interferometry), 0.5/0.4%; SP (stylus profilometry), 4.7/0.7%; OP (optical profilometry), 1.4/12%; AAS (atomic absorption spectroscopy), 0.4/17% (measured calcium loss was converted to lesion depth). The correlation between WLI and SP was R² = 0.98, and between WLI and OP it was R² = 0.85. SMH gave information on qualitative changes of the surface (precision: 5.5%, accuracy: 4.0%). WLI performed best in precision and accuracy, but SP, OP and AAS are all relevant methods for analysing lesion depths and progression, SMH seems suitable for analysing minor changes in surface enamel only.

A comparative evaluation of fluoridated and non-fluoridated mouthrinses using a 5-day cycling enamel erosion model

Objectives To assess the relative protective effect of commercial mouthrinses containing 0-450ppm fluoride on erosion progression in enamel using a simulated 5-day in vitro cycling model with concurrent monitoring of surface microhardness (SMH) and bulk tissue loss. Methods Specimens were randomly assigned to six treatment groups (n=6). The model mimicked morning and evening use with rinse times (30 or 60s) reflecting those prescribed on pack, interspersed with three cycles of demineralisation/remineralisation per simulated day. The latter comprised 1.0% citric acid monohydrate pH3.2 for 300s, with subsequent remineralisation in mucin-free artificial saliva pH7.0 for 120min. SMH was determined by Vickers microindentation and bulk tissue loss using white-light interferometry. Results From the end of day 1, fluoride-containing mouthrinses conferred statistically significant reductions in bulk tissue loss versus fluoride-free rinses (p<0.05), with lesion depth inversely proportional to fluoride concentration. From day 3, the mean lesion depth of specimens treated with the 450 ppm rinse were statistically significantly lower than all comparator treatment groups (p<0.05). Two distinct trends were apparent when comparing SMH changes in groups treated with fluoride-free versus fluoride-containing mouthrinses. In the latter, SMH levelled out over the final three simulated days in contrast to the former whose SMH continued to fall; differences were statistically significant at day 5 (p< 0.05). Conclusions Bulk tissue loss is inversely proportional to fluoride concentration in this cycling model. The plateau in SMH reflects stabilisation of mineral density as the study progresses and the number of fluoride binding sites and consequently uptake increases, in turn leading to enhanced lesion remineralisation.

Enamel benefits of a new hydroxyapatite containing fluoride toothpaste

Objectives: To evaluate the enamel benefits of a new toothpaste containing hydroxyapatite (HAP) and sodium monofluorophosphate (SMFP). Methods: Salivary pellicle coated sound bovine enamel specimens were cycled six times through either HAP/water slurry or water alone treatments, followed by citric acid (15mM or 50mM, pH 3.8) challenges and saliva. The extent of enamel demineralisation was determined by changes in the enamel surface microhardness (SMH). In a second study, the sound enamel specimens were treated with either water, non-fluoride toothpaste, the HAP/SMFP toothpaste or the HAP/SMFP toothpaste pre-treated with a phosphatase enzyme, followed by a citric acid challenge (50mM, pH 3.8) and saliva. Changes in SMH were detemined after six cycles. The reduction in enamel demineralisation by the HAP/SMFP toothpaste was further evaluated in a pH cycling experiment where the acid challenge was 50mM acetic acid (pH 5.0) for 60mins. The remineralisation of sub-surface enamel lesions was measured via changes in SMH following treatment with the HAP/SMFP toothpaste or control toothpastes. In a radiolabelled study, sound and subsurface enamel lesions were treated with 45Ca labelled HAP toothpaste in an in vitro pH cycling study and the uptake of labelled calcium determined. Results: The HAP water slurry significantly (p<0.05) reduced the enamel demineralisation caused by the citric acid challenges, at both concentrations, compared to the water controls. The HAP/SMFP toothpaste significantly (p<0.05) reduced the enamel demineralisation caused by both citric acid and acetic acid challenges compared to the control treatments. In the remineralisation study, the HAP/SMFP toothpaste significantly (p<0.05) increased the remineralisation of enamel compared to a non-fluoride toothpaste. The radiolabelled HAP toothpaste study demonstrated the uptake of calcium to sound enamel and subsurface enamel lesions. Conclusions: A new HAP/SMFP containing toothpaste significantly (p<0.05) reduced the demineralisation of enamel caused by acid challenges compared to control treatments and significantly (p<0.05) increased the remineralisation of sub-surface enamel lesions compared to a non-fluoride toothpaste. A radiolabelled HAP study has demonstrated that calcium ions from the HAP are available to be involved in enamel remineralisation processes that are relevant to help protection from dental erosion and dental caries in vivo.

In vitro assessment of an experimental coat applied over fluoride varnishes

Objective:The time of contact between the product and enamel surface is important in ensuring the efficacy of fluoride varnishes. Thus, some alternatives could avoid fluoride loss to saliva and improve the anticariogenic action of the product. This study evaluated the effect of an experimental coat on the anticariogenic action of fluoride varnishes.Material and Methods:Enamel bovine blocks were selected by evaluating surface microhardness and randomized into five groups (n=24): placebo, Duraphat™, Duraphat™ with coat, Duofluorid™ and Duofluorid™ with coat. Twelve blocks from each group were used to analyze calcium fluoride (CaF2) formed on enamel after treatment. The other 12 blocks were subjected to pH cycling for 7 days. The varnishes were kept on enamel for 6 h. Next, the percentage change of surface microhardness (%SMHC) and mineral loss (ΔZ) were calculated. CaF2 retained and fluoride present in the pH-cycled solutions were also measured.Results:The use of the coat did not decrease %SMHC and ΔZ, but all fluoride varnishes had better results when compared to the placebo (ANOVA and Kruskal-Wallis, respectively). The values from CaF2 formed were higher compared to the values of CaF2 retained (non-paired t test, p<0.05). There was a trend to decrease the amount of F in the solutions at the end of pH cycling (Kruskal-Wallis, p<0.05).Conclusions:Although the experimental coat increased the formation of CaF2 on the enamel surface, it did not significantly improve the anticariogenic action of fluoride varnishes.

Individual Variations in Protective Effects of Experimentally Formed Salivary Pellicles

Salivary proteins protect teeth against acid-induced softening and demineralization by forming a pellicle. However, little is known about individual, gender and ethnic variations in this effect. Therefore, we aimed to determine differences in protective effects of experimentally formed pellicles from 10 healthy young Scandinavians (3 women and 7 men) and 10 healthy young non-Scandinavians (4 women and 6 men) including Arabic, Persian, Pakistan, Indian, and Chinese subjects. Bovine enamel blocks, which were precoated with parotid and submandibular salivary proteins for 12 h, were exposed to an acidic solution with surface microhardness (SMH) determinations before and after. No change in SMH equalled 100% protection, whereas SMH corresponding to no protein coating equalled 0%. The results showed that experimentally formed pellicles from non-Scandinavians protected enamel better than pellicles from Scandinavians (p < 0.001). Within groups protective effects of pellicles formed from parotid and submandibular saliva were equal and subjects with high protection from parotid saliva pellicles also had high protection from submandibular saliva pellicles (r = 0.78; p < 0.001). Within groups considerable differences were obtained among individuals ranging from 25 to 51% protection. However, SDS-PAGE and HPLC did not reveal any systematic relation between saliva protein composition and protective effects, although slightly more of the SN-isoform of S-type cystatin was found in pooled parotid saliva from those non-Scandinavian subjects showing highest protection. We conclude that individual variations in experimental pellicle protection against erosive challenges exist and that such variations appear not to be due to differences in a single protein component.

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.

In situ effect of an erosive challenge on different restorative materials and on enamel adjacent to these materials

Objectives This in situ study evaluated the effect of an erosive challenge on different restorative materials and on enamel restored with these materials, as well as the ability of these materials to protect the adjacent enamel against erosion. Methods Ten volunteers wore palatal devices with eight bovine enamel blocks, randomly selected and distributed into two vertical rows, corresponding to the following groups: GI/GV, resin-modified glass ionomer; GII/GVI, conventional glass ionomer; GIII/GVII, composite resin; GIV/GVIII, amalgam. One row (corresponding to groups I–IV) was immersed in a cola drink and the other row (corresponding to groups V–VIII) was subjected to saliva only. The palatal device was continuously worn for 7 days and only half of the appliance (groups I–IV) was immersed in the soft drink (Coca-Cola ®, 150 mL) for 5 min, three times a day. The study variables comprised the wear (profilometry, μm) and the percentage of surface microhardness change (%SMHC). Data were tested for significant differences by two-way ANOVA and Tukey's tests ( p < 0.05). Results Considering the restorative materials, for %SMHC and wear, there were no differences among the materials and between the saliva and the erosive challenge. For enamel analyses, the erosive challenge promoted a higher wear and %SMHC of the enamel than did the saliva. There were no significant differences in wear and %SMHC of the enamel adjacent to the different restorative materials. Conclusion This research data suggest that there is little %SMHC and wear of the studied restorative materials and none of them had a preventive effect against erosion on adjacent enamel, which showed a pronounced wear.

Damage effect of keV proton irradiation on aluminized Kapton film

Damage effects of proton irradiation on aluminized Kapton films were investigated through ground simulation experiments, in which the energy of protons was 90 keV and the flux was 5.0×10 11 cm −2 s −1. Changes in surface morphology, optical properties, microhardness and microstructure of Kapton/Al were analyzed. The experimental results show that proton irradiation results in the increase of surface roughness and microhardness, and the degradation of the reflective property in the 500–1200 nm range. Raman spectra and XPS analysis demonstrate that changes in chemical structure occurred during irradiation, including the bond breaking of the part of the carbonyl and aromatic ether, ring opening reaction of cyclic imide, and the formation of some new bonds and structure.

Effect of calcium pre-rinse and fluoride dentifrice on remineralisation of artificially demineralised enamel and on the composition of the dental biofilm formed in situ

Objective: This in situ blind crossover study investigated the effect of calcium (Ca) rinse prior to the use fluoride (F) dentifrice on remineralisation of artificially demineralised enamel and on the composition of biofilm. Design: During four phases of 14 days, 10 volunteers wore appliances containing two artificially demineralised bovine enamel blocks. Three times a day, they rinsed with 10 mL of Ca (150 mM) or placebo rinse (1 min). A slurry (1:3, w/v) of F (1030 ppm) or placebo dentifrice was dripped onto the blocks. During 1 min, the volunteers brushed their teeth with the respective dentifrice. The appliance was replaced into the mouth and the volunteers rinsed with water. The biofilm formed on the blocks was analysed for F and Ca. Enamel alterations were evaluated by the percentage of surface microhardness change (%SMHC), cross-sectional microhardness (% mineral volume) and alkali-soluble F analysis. Data were analysed by ANOVA ( p < 0.05). Results: The use of the Ca pre-rinse before the F dentifrice produced a six- and four-fold increase in biofilm F and Ca concentrations, respectively. For enamel, the remineralisation was significantly improved by the Ca pre-rinse when compared to the other treatments. There was a significantly higher concentration of alkali-soluble F in enamel when the F dentifrice was used, but the Ca pre-rinse did not have any significant additive effect. Conclusions: According to our protocol, the Ca pre-rinse significantly increased biofilm F concentration and, regardless the use of F dentifrice, significantly enhanced the remineralisation of artificially demineralised enamel.

Influence of Fluoride Dentifrice on Brushing Abrasion of Eroded Human Enamel: An in situ/ex vivo Study

This in situ/ex vivo study assessed the effect of fluoride dentifrice on eroded enamel subjected to brushing abrasion. In a crossover study performed in 2 phases, 10 volunteers wore acrylic palatal appliances, each containing 3 human enamel blocks. Dentifrice was used to brush the volunteers’ teeth and the specimens subjected to abrasion. In phases A and B the dentifrices used had the same formulation, except for the absence or presence of fluoride, respectively. The blocks were subjected to erosion by immersion of the appliances in a cola drink for 5 min, 4 times a day. Then the blocks were brushed, and the appliance was replaced into the mouth. Enamel alterations were determined using profilometry and percentage change in surface microhardness (%SMHC) tests. The data were tested using the paired t test. The mean wear values (±SD, µm) were: group A 6.84 ± 1.72 and group B 5.38 ± 1.21 (p = 0.04). The mean %SMHC values (±SD) were: group A 54.6 ± 16.2 and group B 45.7 ± 6.8 (p = 0.04). Fluoride dentifrice had a protective effect on eroded enamel subjected to brushing abrasion.

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 30 min. 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 5 min in 150 mL of cola drink, 4 times a day. Immediately after immersion, no treatment was performed in one row. The other row was brushed after 1 min using a fluoride dentifrice and the device was replaced into mouth. After 30 min, the remaining row was brushed. In the other phase, the procedures were repeated, but after immersion the volunteers rinsed for 1 min with 10 mL of a 10 mM 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 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.