The effect of pH on the erosion of dentine and enamel by dietary acids in vitro

Effects of common dental materials used in preventive or operative dentistry on dentin permeability and remineralization

The aim of this study was to evaluate the dentin remineralization induced by bioactive substances contained in common dental materials used in preventive and operative dentistry. Several materials were applied on human dentin segments. Dentin permeability was quantified using a fluid filtration system working at 20 cm H(2)O. Micro-Raman, SEM-EDX, and microhardness calculation were used to evaluate changes in the mineralization of dentin. Dentin treated with the prophylactic materials showed different dentin permeability values, in particular subsequent to immersion in remineralizing solutions (RSS). The bioactive glass (Sylc) was the only substance able to reduce dentin permeability after immersion in remineralizing solution and to show hydroxyapatite precipitation as a sign of dentin remineralization. The reduction in dentin permeability obtained after the application of the other prophylactic materials used in this study was due to the presence of the remnant material in the dentinal tubules, with no remineralization effect after storage in remineralizing solution. In conclusion, the results indicated that bioactive glass prophy powder may induce immediate remineralization of dentin.

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 60min 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.

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.

Pop-cola acids and tooth erosion: an in vitro, in vivo, electron-microscopic, and clinical report

Introduction. Manufactured Colas are consumed universally as soft drinks. Evidence about the acid contents of Cola-beverages and its effects on teeth is rare. Aim. To assess (i) cola acidity and buffering capacity in vitro, (ii) tooth erosion after swishing with colas in vivo (iii) scanning electron microscopic effects on teeth of colas, and tooth-brush abrasion, and (iv) report a clinical case of erosion from cola consumption. Materials and Methods. (i) We measured six commercially available pop "Cola beverages", pH, and buffering capacities using a pH-Mettler Automatic Titrator, with weak solution of Sodium Hydroxide (ii) two cohorts, one with teeth, the second without teeth rinsed with aliquots of Cola for 60 seconds. Swished cola samples tested for calcium and phosphorus contents using standardized chemical analytical methods (iii) enamel, dentine, and the enamel-cemental junction from unerupted extracted wisdom teeth were examined with a scanning electron microscope after exposure to colas, and tested for tooth-brush abrasion; (iv) a clinical case of pop cola erosion presentation, are all described. Results. Comparisons among pop colas tested in vitro reveal high acidity with very low pH. Buffering capacities in millilitres of 0.5 M NaOH needed to increase one pH unit, to pH 5.5 and pH 7 are reported. Rinsing in vivo with pop cola causes leeching of calcium from teeth; SEM shows dental erosion, and pop-cola consumption induces advanced dental erosion and facilitates abrasion. Conclusions. (i) Pop-Cola acid activity is below the critical pH 5.5 for tooth dissolution, with high buffering capacities countering neutralization effects of saliva; (ii) calcium is leeched out of teeth after rinsing with pop colas; (iii) SEM evidence explains why chronic exposure to acid pop colas causes dental frangibles; (iv) a clinical case of pop-cola erosion confirms this.

In vitro and in vivo analyses of the effects of desensitizing agents on dentin permeability and dentinal tubule occlusion

This study was done to assess the influence of the topical application of two different desensitizing agents on dentin permeability and dentinal tubule occlusion. Twenty-one rats provided 84 teeth: 36 for the in vitro and 48 for the in vivo investigation. The following agents were tested: Group 1, 2% potassium nitrate plus 2% sodium fluoride gel; Group 2, 5% sodium fluoride varnish; Group 3, 3% hydroxyethylcellulose gel (control). Cervical cavities were prepared and EDTA was applied to expose the dentinal tubules. After each treatment, Evans blue dye was applied to the teeth. Dentin permeability, scanning electron microscope (SEM) sections, and energy dispersive X-ray (EDX) were analyzed. One-way ANOVA was used to compare the data. There were significant differences (P < 0.05) among groups for dentin permeability, number of tubules/mm(2), tubule area and tubular diameter. Groups 1 and 2 (both in vitro and in vivo) showed open and partially occluded tubules. Group 3 had the most open tubules. EDX revealed similar composition for both experimental conditions. Within the limits of the study, 2% nitrate potassium plus 2% sodium fluoride gel and 5% fluoride varnish decreased the dentin permeability, resulting in partial tubular occlusion.

In vitro evaluation of the effect of natural orange juices on dentin morphology

The patient's diet has been considered an important etiological factor of dentin hypersensitivity. The frequent ingestion of acidic substances can promote the loss of dental structure or remove the smear layer. The purpose of this study was to evaluate the degree of smear layer removal and dentinal tubules exposure by different natural orange juices. Extracted human teeth were submitted to manual scaling in order to develop the smear layer. Seventy dentin samples were obtained and distributed into the following groups: Control, lime orange, lime, valência orange, navel orange, mandarin, and tangerine. Each group included 2 methods of application: Topical and topical + friction. After preparation for SEM analysis, photomicrographs were assessed by a blind calibrated examiner using an index system. The Kruskal-Wallis test indicated a significant influence of the orange juices on smear layer removal. Significant difference was observed between navel orange, valência orange, mandarin and the control group (p < 0.05). These orange juices resulted in greater removal of the smear layer and greater opening of dentinal tubules. The comparison between the application methods for each group using the Mann-Whitney test showed that friction increased smear layer removal significantly only for lime orange and lime. The data suggest that certain natural orange juices are more effective in terms of smear layer removal and dentinal tubules exposure than others.

In vitro release of phosphoric acid ester from self-etching primer

Self-etching primers have simplified the process of direct bonding of dental resins, by eliminating the rinsing step after etching in conventional bonding, for example. Although it is generally assumed that all of the applied self-etching primer is incorporated into the resin, the possibility that a substantial amount remains free and extractable into a person's saliva has not been investigated. The aim of the present study was to examine this issue by bonding brackets to extracted teeth with self-etching primers under controlled conditions and determining the proportion of the applied phosphoric acid ester that is subsequently extractable by high-performance liquid chromatography. Approximately half of the applied acid ester was extractable and thus not integrated into the polymeric network following standard light curing. This was reduced to 40% when the curing time was doubled. Acid ester leaching was a rapid process that was essentially completed within an hour.

Acidic beverages increase the risk of in vitro tooth erosion

Acidic beverages are thought to increase the potential for dental erosion. We report pH and titratable acidities (ie, quantity of base required to bring a solution to neutral pH) of beverages popular in the United States and lesion depths in enamel and root surfaces after beverage exposure, and we describe associations among pH, titratable acidity, and both enamel and root erosive lesion depths. The pH of 100% juices, regular sodas, diet sodas, and sports drinks upon opening and the titratable acidity both upon opening and after 60 minutes of stirring were measured. Enamel and root surfaces of healthy permanent molars and premolars were exposed to individual beverages (4 enamel and 4 root surfaces per beverage) for 25 hours, and erosion was measured. Statistical analyses included 2-sample t tests, analyses of variance with post hoc Tukey studentized range test; and Spearman rank correlation coefficients. All beverages were acidic; the titratable acidity of energy drinks was greater than that of regular and diet sodas that were greater than that of 100% juices and sports drinks (P < .05). Enamel lesion depths after beverage exposures were greatest for Gatorade, followed by those for Red Bull and Coke that were greater than those for Diet Coke and 100% apple juice (P < .05). Root lesion depths were greatest for Gatorade, followed by Red Bull, Coke, 100% apple juice, and Diet Coke (P < .05). Lesion depths were not associated with pH or titratable acidity. Beverages popular in the United States can produce dental erosion.

Impact of the in situ formed salivary pellicle on enamel and dentine erosion induced by different acids

OBJECTIVE

To investigate and compare the protective impact of the in situ formed salivary pellicle on enamel and dentine erosion caused by different acids at pH 2.6.

METHODS

Bovine enamel and dentine samples were exposed for 120 min in the oral cavity of 10 healthy volunteers. Subsequently, enamel and dentine pellicle-covered specimens were extraorally immersed in 1 ml hydrochloric, citric or phosphoric acid (pH 2.6, 60 s, each acid n=30 samples). Pellicle-free samples (each acid n=10) served as controls. Calcium release into the acid was determined by atomic absorption spectroscopy. The data were analysed by two-way ANOVA and Tukey's test (alpha=0.05).

RESULTS

Pellicle-covered samples showed significantly less calcium loss compared to pellicle-free samples in all acid groups. The mean (SD) pellicle protection (% reduction of calcium loss) was significantly better for enamel samples [60.9 (5.3)] than for dentine samples [30.5 (5.0)], but revealed no differences among the acids.

CONCLUSION

The efficacy of the in situ pellicle in reducing erosion was 2-fold better for enamel than for dentine. Protection of the pellicle was not influenced by the kind of acid when enamel and dentine erosion was performed at pH 2.6.

Laser-activated fluoride treatment of enamel as prevention against erosion

BACKGROUND

Erosion is the loss of dental hard tissues from an acidic challenge, often resulting in exposure of dentinal tubules and hypersensitivity to environmental stimuli. Laser-activated fluoride (LAF) therapy with 488nm laser energy has been shown previously to increase the resistance of human enamel and dentine to acid dissolution. The aims of this study were to investigate the action spectrum of LAF in protecting tooth enamel from softening in response to an erosive challenge, and to examine for any temperature change with the treatment.

MATERIALS AND METHODS

Buccal and lingual surfaces of extracted sound molar and premolar teeth were used to prepare matched pairs of enamel slabs (N = 10 per group). After application of 1.23% neutral sodium fluoride gel (12 300ppm F ion), slab surfaces were lased with 488, 514.5, 532, 633, 670, 830 or 1064nm wavelength (energy density 15J/cm(-2); spot size 5mm), then exposed to an erosive challenge (1.0M HCI for five minutes). The Vicker's hardness number (VHN) was recorded before fluoride gel application and again following the acid challenge. Negative controls did not receive laser exposure.

RESULTS

All wavelengths of laser light examined provided a protective LAF effect against softening, compared with the negative control surfaces.

CONCLUSION

From these findings, we conclude that the action spectrum of the LAF effect extends across the visible spectrum, providing protection to dental enamel from an erosive challenge.

A clinical study in situ to assess the effect of a food approved polymer on the erosion potential of drinks

OBJECTIVES

The consumption of acidic soft drinks continues to rise as do concerns regarding effects of frequent intake. The aim of the study was to determine the effect of acidic soft drinks containing food approved polymers, on dental enamel.

METHODS

The study design was a single blind, randomised, five-treatment crossover clinical trial involving 15 healthy dentate subjects. Subjects wore an upper removable acrylic appliance retaining two enamel specimens and consumed 250ml of beverage four times/day for 10 days. The following beverages were tested: (1) unmodified acidic soft drink, (2) experimental acidic soft drink with 0.02% polyphosphate, (3) experimental acidic soft drink with 0.02% polyphosphate and 0.01% calcium, (4) experimental acidic soft drink with 0.02% polyphosphate and 0.03% xanthan gum, and (5) mineral water. Tissue loss was measured at days 5 and 10 of each study leg using a profilometer.

RESULTS

The order of erosion from most to least at day 10 was unmodified acidic soft drink>experimental acidic soft drink with polyphosphate>experimental acidic soft drink with polyphosphate+gum>experimental acidic soft drink with polyphosphate+calcium>mineral water. At day 10 the unmodified acidic soft drink was significantly (p=0.001) more erosive than all other drinks.

CONCLUSIONS

Unmodified acidic soft drink with the addition of polyphosphate alone or combined with calcium or xanthan gum are all effective at reducing erosion of enamel compared with the unmodified soft acidic drink.

Protective effect of the in situ pellicle on dentin erosion–an ex vivo pilot study

AIM

The acquired pellicle is well known as an anti-erosive proteinaceous layer on enamel, but its protective properties on dentin have not been investigated in detail until now. The aim of the present ex vivo study was to evaluate the erosive effects on pellicle coated dentin.

METHODS

Bovine dentin slabs were exposed to the oral cavity of one subject for 120 min for in situ pellicle formation. Subsequently, the slabs were incubated with HCl (pH 2.3) in vitro for 5 min and erosive calcium-release was measured photometrically. In addition, the acid treated specimens were evaluated by transmission electron microscopy (TEM). Pellicle free samples served as controls.

RESULTS

Calcium erosion from the pellicle coated dentin slabs amounted to 23.5+/-2.9 microg Ca/min (pellicle free samples: 32.2+/-4.2 microg Ca/min). The difference was statistically significant (p < or = 0.05). In pellicle coated as well as in uncoated dentin samples, TEM-evaluation showed a demineralised dentinal surface layer which thickness ranged between 3 and 6 microm. The pellicle itself was partially dissolved but not removed by hydrochloric acid treatment.

CONCLUSION

The protective properties of the acquired pellicle against an erosive challenge of the dentinal surface are limited. The dentinal pellicle functions like an ion permeable network rather than a barrier.

Surface layer erosion of natural caries lesions with phosphoric and hydrochloric acid gels in preparation for resin infiltration

The infiltration of proximal enamel lesions with low-viscosity light curing resins could be a viable approach to stop lesion progression. However, penetration of sealant might be hampered by the comparatively highly mineralized surface layers of natural lesions. Therefore, the aim of this study was to compare the efficacy of three different etching gels in removing the surface layer in various etching times. Extracted human molars and premolars showing proximal white spot lesions were cut across the demineralized areas. Ninety-six lesions expected from visual examination to be confined to the outer enamel (C1) were selected. The cut surface and half of each lesion were varnished, thus serving as control. Subsequently, the lesions were etched with either phosphoric (37%) or hydrochloric (5 or 15%) acid gel for 30-120 s (n = 8/group). Specimens were examined using confocal microscopy and transversal microradiography. Surface layer reduction was significantly increased in lesions etched with 15% HCl gel for 90 and 120 s compared to those etched with H(3)PO(4) gel for 30-120 s (p < 0.05). No significant differences regarding the depths of erosion in the lesions compared to sound enamel could be observed (p > 0.05). An effective reduction in the surface layer of natural enamel caries can be achieved by etching with 15% hydrochloric acid gel for 90-120 s.

The erosive potential of flavoured sparkling water drinks

OBJECTIVE

The potential role of acidic drinks in the aetiology of dental erosion is well recognized. Whilst the wide-scale consumption of bottled waters is unlikely to contribute significantly to erosion, the role of flavoured sparkling water drinks is unclear. The aim of this study was to determine the pH, titratable acidity and in vitro erosive potential of a selection of these drinks drawn from the UK market to identify what dietary advice would be appropriate in relation to their consumption.

METHODS

pH was measured using a pH electrode and titratable acidity recorded by titration with 0.1-m NaOH. Erosive potential was assessed using an in vitro dissolution assay with hydroxyapatite powder and electron microscopic examination of surface enamel of extracted human teeth, following exposure to the flavoured sparkling waters for 30 min.

RESULTS

All of the flavoured waters tested showed appreciable titratable acidity (0.344-0.663 mmol) and low pH (2.74-3.34). In the hydroxyapatite dissolution assay, all of the waters demonstrated erosive potential (89-143%) similar to or greater than that of pure orange juice, an established erosive drink. Exposure of the extracted teeth to the flavoured waters resulted in surface changes consistent with erosive dissolution.

CONCLUSIONS

Flavoured sparkling waters should be considered as potentially erosive, and preventive advice on their consumption should recognize them as potentially acidic drinks rather than water with flavouring.

An investigation using atomic force microscopy nanoindentation of dental enamel demineralization as a function of undissociated acid concentration and differential buffer capacity

Acidic drinks and foodstuffs can demineralize dental hard tissues, leading to a pathological condition known as dental erosion, which is of increasing clinical concern. The first step in enamel dissolution is a demineralization of the outer few micrometres of tissue, which results in a softening of the structure. The primary determinant of dissolution rate is pH, but the concentration of undissociated acid, which is related to buffer capacity, also appears to be important. In this study, atomic force microscopy nanoindentation was used to measure the first initial demineralization (softening) induced within 1 min by exposure to solutions with a range of undissociated acid concentration and natural pH of 3.3 or with an undissociated acid concentration of 10 mmol l-1 and pH adjusted to 3.3. The results indicate that differential buffering capacity is a better determinant of softening than undissociated acid concentration. Under the conditions of these experiments, a buffer capacity of >3 mmol l-1 pH-1 does not have any further effect on dissolution rate. These results imply that differential buffering capacity should be used for preference over undissociated acid concentration or titratable acidity, which are more commonly employed in the literature.

Impact of the acid flow rate on dentin erosion

OBJECTIVE

The study aimed to evaluate the erosive effects of acids flowing with different velocities and duration on dentin previously pre-treated with distilled water or human saliva.

METHODS

Bovine dentin surfaces were submitted to a 10 min demineralisation with hydrochloric or citric acid (pH 2.3, 37 degrees C) in an artificial mouth at flow rates of 3, 2.25, 1.5, 0.75 or 0.15 ml/min or in 30 ml of the respective acid without movement (each subgroup n=16 specimens). Prior to the demineralisation, half of the specimens of each group were either pre-treated with distilled water or human saliva for 120 min. After 2, 5 and 10 min demineralisation, profilometric traces of dentin loss were performed perpendicular to the direction of acid flow at three sites (A-C) with intervals of 500 microm. The first profile (A) was taken in a distance of 1.5 mm from the acid starting to flow over the sample. Thus, median dentin loss at each site was calculated and statistically analysed by five-way ANOVA.

RESULTS

Dentin loss increased with increasing acid flow rate and demineralisation time and was higher for demineralisation with citric acid compared to hydrochloric acid. For given flow rates of 0.15 to 3 ml/min, measurement of dentin loss yielded highest values for site A and decreasing values for sites B and C. For all groups, no significant differences of dentin loss were observed between specimens pre-treated with distilled water or human saliva.

CONCLUSION

Under the conditions of this study, both duration of demineralisation and acid flow rate but not pre-treatment with distilled water or saliva influence the extent of dentin erosion.

In vitro wear of resin-based materials—Simultaneous corrosive and abrasive wear

The aim of this study was to evaluate the wear of resin-based materials caused by the association of abrasive and corrosive processes. Twenty specimens were prepared for each material, cast in epoxy in acrylic rings, polished, and profiled with an MTS 3D Profiler. Antagonists were made from deciduous molars. Specimens were distributed into eight groups (n = 10), according to the material (Filtek Supreme, Point 4, Dyract AP, and Fuji II LC) and the type of slurry (neutral and acidic), and then cycled 100,000 times in the OHSU oral wear simulator. The specimens were cleaned and reprofiled. Volume loss and maximum depth were determined. ANOVA and Tukey's test were used for data analysis (p < 0.05). The area of the wear facet on the antagonist was also measured. Composites displayed less wear than the compomer and the resin-modified glass ionomer. Significant differences also were found for cusp wear, with a significant positive correlation shown between cusp and material wear. The acidic slurry significantly increased the wear of the materials compared to the neutral slurry. Exposure to acidic slurry accelerated the wear of resin-based materials.

Erosive effects of different acids on bovine enamel: release of calcium and phosphate in vitro

The present study intended to investigate minimal erosive effects of different acids on enamel during short time incubation via determination of calcium and phosphate dissolution. Bovine enamel specimens were eroded for 1-5 min with eight different acids of pH 2, 2.3 and 3 (citric (CA), maleic (MA), lactic (LA), tartaric (TA), phosphoric (PA), oxalic (OA), acetic (AA) and hydrochloric acid (HCl)). Calcium (Ca) and phosphate (P) release were determined photometrically using arsenazo III (calcium) and malachite green (phosphate) as substrates. Each subgroup contained eight enamel specimens. Amount of titratable acid was determined for all acidic solutions. MA, LA, TA, AA and HCl caused linear release of Ca and P, PA of Ca, CA of P. For CA, MA, LA, TA, AA, PA and HCl mineral loss was shown to be pH-dependent. Ca dissolution varied between 28.6+/-4.4 (LA, pH 2) and 2.4+/-0.7 nmol mm(-2)min(-1) (HCl, pH 3), P dissolution ranged between 17.2+/-2.6 (LA, pH 2) and 1.4+/-0.4 nmol mm(-2)min(-1) (HCl, pH 3). LA was one of the most erosive acids. AA was very erosive at pH 3. HCl and MA were shown to have the lowest erosive effects. There was only a weak correlation (r=0.28) between P and Ca release and the amount of titratable acid. The method of the present study allows investigation of minimal erosive effects via direct determination of P and Ca dissolution. During short time exposition at constant pH level, erosive effects mainly depend on pH and type of acid but not on amount of titratable acid.

Influence of the Organic Matrix on Root Dentine Erosion by Citric Acid

This investigation was conducted in an attempt to clarify the role of the organic matrix in bovine dentine demineralisation by 1% citric acid. Dentine slabs (n = 15) were treated for 2 min with 10% sodium hypochlorite (NaOCl, a strong protein solvent), 2% glutaraldehyde (GDA, a protein fixative) or deionised water (DIW, as negative control) prior to each of 5 demineralisation periods of 30 min. The mineral loss (DeltaZ), lesion depth (LD) and surface loss (SL) were determined after each period of demineralisation, by transverse microradiography. The NaOCl-treated group showed higher DeltaZ and LD than the GDA- and DIW-treated groups. No differences between GDA and DIW groups were found. The DeltaZ and LD profiles were explained by quadratic fits (r(2) >0.80; p = 0.001) in all groups. SL was detected only in the NaOCl-treated group. The data suggested that the maintenance of the organic matrix in the lesion might be important to reduce the erosion progression rate.

Human enamel erosion in constant composition citric acid solutions as a function of degree of saturation with respect to hydroxyapatite

The objective of this study was to investigate human enamel erosion under constant composition conditions, as a function of solution degree of saturation (DS) with respect to hydroxyapatite. The experimental conditions were relevant to the initial stages of enamel erosion by soft drinks. Nanoindentation was used to compare enamel surface softening caused by a control mineral water and two citric acid solutions with DS = 0.000 and DS = 0.032, both having pH 3.30. Enamel hardness and reduced elastic modulus were measured after 0, 30, 60, 120, 300 and 600 s exposure. A statistically significant change in enamel hardness was detected after 30 s exposure to both citric acid solutions, indicating that nanoindentation is extremely sensitive to the initial stages of erosion. There was a statistically significant difference between the mechanical properties of enamel exposed to the two citric acid solutions after 30, 60 and 120 s. At these times, the solution with DS = 0.000 caused twice as much enamel softening as that with DS = 0.032. This demonstrates that it may be possible to design a soft drink with a low erosive potential and a good taste by a small change in DS, at a typical drink pH.

Erosive Effect of a New Sports Drink on Dental Enamel during Exercise

PURPOSE

To compare the potential erosive effect of a prototype carbohydrate-electrolyte drink (PCE) with a neutral control (water) and a commercially available carbohydrate-electrolyte drink (CCE) during exercise.

METHODS

: Nineteen healthy adults (male, N = 16; female, N = 3) took part in this single blind, three-way crossover study. Subjects were given each of the three drinks according to a randomization schedule, approximately balanced for first-order carryover effects. At the beginning of each of the three study periods, the volunteers were fitted with an intraoral appliance containing two human enamel blocks. During each study period, volunteers exercised for 75 min.d(-1) (5 repetitions of 15 min of exercise, with 5-min rests between exercise repetitions), 5 d.wk(-1) for 3 wk. Each day, drink aliquots of 200 mL were consumed during a 5-min period before exercise and after every 15-min bout of exercise, followed by a final 400-mL aliquot ingested over a 10-min period: a total of 1400 mL per study day. Dental erosion was measured as tissue loss from the enamel blocks by profilometry at the end of each study period.

RESULTS

Water, PCE, and CCE produced 0.138 microm (SD 0.090 microm), 0.138 microm (SD 0.038 microm), and 4.238 microm (SD 3.872 microm) of enamel loss, respectively. A Wilcoxon t statistic showed a significant statistical difference between the PCE and CCE drinks (P < 0.001), whereas no significant difference could be detected between the PCE drink and water (P = 0.740).

CONCLUSION

The PCE solution showed minimal erosion compared with the commercially available drink, and was statistically indistinguishable from water under the conditions of this study. Use of CE solutions formulated to minimize erosion during exercise may provide significant dental benefits.

The validation of Quantitative light-induced fluorescence to quantify acid erosion of human enamel

OBJECTIVE

The purpose of this study was to validate the Quantitative light-induced fluorescence (QLF) device against transverse microradiography (TMR) with regard to the quantification of enamel erosion in vitro.

DESIGN

Longitudinal in vitro.

METHODS

Thirty previously extracted, caries free, human premolars were selected and prepared by gentle pumicing and coating in an acid-resistant nail-varnish save for an exposed window on the buccal surface. QLF baseline images were taken and the teeth then exposed to an erosive solution, 0.1% citric acid (pH 2.74). Teeth were removed at 30min intervals, air-dried and QLF images taken. At this time one tooth was randomly selected, removed from solution and sectioned through the lesion at three sites. The polished sample (100microm) was subjected to TMR and analysed for erosive mineral loss using proprietary software, with the DeltaZ values noted. QLF images were analysed by a blinded examiner with DeltaF and DeltaQ values recorded. Data were entered into SPSS and the correlation between the DeltaZ and DeltaF, and DeltaZ and DeltaQ values calculated.

RESULTS

A wide range of erosive lesions was produced, with a steady increase in both DeltaZ and DeltaF over time; DeltaZ (24.0 (S.D. 1.2)-6114.3 (S.D. 1177.57)); DeltaF (1.8-11.2), DeltaQ (2.5-202.6). The results were scatter plotted and a regression line calculated. A positive correlation between DeltaZ and DeltaF of 0.91 was found, and for DeltaZ and DeltaQ; 0.87.

CONCLUSIONS

The ability for QLF to detect and longitudinally monitor in vitro erosion has been shown. The strong positive correlation of DeltaF with DeltaZ suggests that percentage fluorescence loss as measured by QLF could be of great value in the development of a non-destructive, longitudinal tool for use in vitro, in situ and possibly in vivo.

The erosive potential of commercially available mouthrinses on enamel as measured by Quantitative Light-induced Fluorescence (QLF)

DESIGN

Longitudinal in vitro.

METHODS

Previously extracted, caries free, human premolars were selected and prepared by gentle pumicing and coating in an acid-resistant nail-varnish save for an exposed enamel window on the buccal surface. Each was assigned to one of eight groups (six per group, 10 in positive control); positive control (citric acid, pH 2.7, F(-) 0 ppm), negative control (pH 7.0, F(-) 0 ppm) Listerine (pH 3.87, F(-) 0.021 ppm), Tesco Value (pH 6.05, F(-) 289.00 ppm), Tesco Total Care (pH 6.20, F(-) 313.84 ppm), Sainsbury's (pH 6.15, F(-) 365.75 ppm), Sensodyne (pH 6.12, F(-) 285.30 ppm) and Corsodyl (pH 5.65, F(-) 0 ppm). The titratable acid values (TAV) for each rinse were established using volume (ml) of 0.1 M NaOH to achieve pH 7. Fluoride values were obtained by ion selective electrode. The solutions were kept at 37 degrees C and gently agitated. Teeth were removed at hourly intervals for 15 h, air-dried and subjected to Quantitative Light-induced Fluorescence (QLF) examination by a blinded examiner and DeltaQ values recorded. At the conclusion of the study each of the positive control teeth and one from each other group were sectioned through the eroded lesion, ground and polished to 100 micrometers and subjected to transverse microradiography and DeltaZ recorded for validation.

RESULTS

TAVs were: Listerine 2.45 L > Sainsbury's 0.35 ml >Tesco Total Care 0.14 ml > Tesco Value 0.08 ml > Corsodyl 0.10 ml >Sensodyne 0.9 ml. DeltaQ increased over time for the positive control, (0 h 0.2, 10 h 95.2, 15 h 152.3). Negative controls remained stable. The increase in DeltaQ for each rinse after 15 h was Listerine (9.3(+/-7.2)), Corsodyl (1.5(+/-1.2)), Tesco Value (1.8(+/-1.2)), Tesco Total Care (1.4(+/-1.1)), Sainsbury's (3.4(+/-2.2)), Sensodyne (0.9(+/-1.6)). TMR confirmed the presence/absence of erosive lesions.

CONCLUSIONS

QLF effectively monitored erosion in the positive controls and lack of erosion in the NC. Only one mouthrinse (Listerine) caused any erosion compared to the negative control, but this was only significant after 14 h of continuous use.

Human enamel dissolution in citric acid as a function of pH in the range 2.30< or =pH< or =6.30--a nanoindentation study

The objective of this study was to investigate the dissolution of human enamel in citric acid solutions over a wide range of pH. The in vitro conditions are considered to be relevant to soft drink-induced enamel erosion. Nanoindentation was used to investigate changes in the nanomechanical properties of polished enamel surfaces after exposure to citric acid solutions. Solutions used had 38.1 mmol l-1 citric acid and pH greater than 2.3 but less than 6.3 (2.30 < or = pH < or = 6.30). Samples were exposed to rapidly stirred, constant composition solutions for 120 s. Statistically significant changes in enamel hardness and reduced elastic modulus were observed after exposure to all solutions. There was an approximately linear dependence of enamel hardness on solution pH for 2.90 < or = pH < or = 6.30. Below pH 2.90, enamel is thought to have reached the lowest possible hardness value. The reduction in enamel dissolution caused by an increase in pH of a soft drink is likely to be small. Product modification to reduce the erosive potential of drinks may require additional methods such as addition of calcium salts.