- Email: [email protected]
In vitro action of Bordeaux red wine on the microhardness of human dental enamel
Archives of Oral Biology (2003) 48, 141—145
In vitro action of Bordeaux red wine on the microhardness of human dental enamel L. Lupi-Peguriera,*, M. Mullera, E. Leforestierb, M.F. Bertrandb, M. Bollac a
Laboratory of Dental Biomaterials and Experimental Odontology, Department of Public Health, Faculty of Odontology, University of Nice-Sophia Antipolis 24, Avenue Des Diables Bleus, 06357 Nice Cedex 4, France b Laboratory of Dental Biomaterials and Experimental Odontology, Department of Conservative Dentistry and Endodontics, University of Nice-Sophia Antipolis 24, Avenue Des Diables Bleus, 06357 Nice Cedex 4, France c Laboratory of Dental Biomaterials and Experimental Odontology, Department of Biomaterials, University of Nice-Sophia Antipolis 24, Avenue Des Diables Bleus, 06357 Nice Cedex 4, France Accepted 9 October 2002
KEYWORDS Dental erosion; French wine; Microhardness; Scanning electron microscopy
Summary Several studies have demonstrated that the regular and large consumption of wine is associated with increased risk of tooth erosion. Here, the effect of Bordeaux red wine on enamel was estimated by measuring changes in its Vickers microhardness. Thirty premolars were used; microhardness tests were performed on buccal areas before and after 10, 30, 90 and 120 s immersion in the wine (pH ¼ 3:9). Enamel surfaces were also observed by scanning electron microscopy. No statistically significant difference was found between the mean Vickers microhardness obtained at t ¼ 0 and 90 s, but slight signs of enamel demineralisation were observed with the scanning electron microscope. It appears that wine has no disastrous effect on the microhardness of dental enamel when the two are in contact for less than 90 s. When the exposure is for at least 120 s, it may become harmful, as the decrease in the microhardness of enamel was then significant (P < 0:05). ß 2003 Elsevier Science Ltd. All rights reserved.
Introduction Erosion is that type of tooth wear, resulting from exposure to non-bacterial chemical attack, that leads to loss of dental hard tissue. Clinically, the demineralised enamel surface is removed, leaving a smooth surface.1—4 Exposure of dentine is often marked by an increase in tooth sensitivity. Eventually the pulp may be exposed. Erosion is almost always caused either by gastric acid or dietary acids, or by acid present in the atmosphere of
Corresponding author. Tel.: þ33-4-92-00-13-18; fax: þ33-4-92-00-12-63. E-mail address: [email protected] (L. Lupi-Pegurier).
the workplace.5 Traditional terminology describes two main patterns: 1. Exogenous erosion caused by extrinsic factors, e.g. dietary, occupational. Usually, the lesions are bilateral, affecting mostly the labial and buccal surfaces of incisors, canines and premolars adjacent to the gingival margin. Approximal and occlusal surfaces may be involved too.6 2. Endogenous erosion caused by an intrinsic factor, i.e. gastric acid. This presents primarily with dissolution of enamel and dentine from the palatal and lingual surfaces of the dentition, with subsequent thinning of the maxillary incisal edges.5,7
0003–9969/03/$ — see front matter ß 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0003-9969(02)00206-6
142
L. Lupi-Pegurier et al.
The frequent consumption of citrus fruits and their juice is well documented as causing erosion,4,8 as are acidic soft drinks.3,4,9,10 Miller11 noted that erosion occurred after exposure of the teeth to organic and inorganic acids. He speculated that, as with fruit juices, regular wine drinking might similarly lead to erosion and demonstrated that decalcification occurred in vitro when human teeth were bathed in a ‘Rhine wine’. Later, several case reports and clinical studies have revealed that regular and heavy wine consumption (up to and including chronic alcoholism) and professional exposure, e.g. in wine tasters, are associated with an increased risk of tooth erosion.1,5,12,13 However, the dental effects of moderate exposure to wine have never, to the best of our knowledge, been studied. France is the second largest wine producer in the world after Italy and over 60 l per capita are consumed annually. Our purpose now was to study the effect of a French red wine, a Bordeaux, on teeth according to time of exposure. Effects were assessed by measuring the Vickers microhardness of the enamel surface and observing changes in the enamel by scanning electron microscopy.
Materials and methods The wine The beverage tested was a Bordeaux red wine (B. Taillan, 1996). Its pH was read with a radiometer PHM 84 pH meter (digit 505; Crison, Barcelona, Spain) fitted with a pH electrode (Fisher Bioblock Scientific, Illkirch, France) at 25 8C. The wine was analysed for phosphorus by the ammonium molybdate method and for calcium by atomic absorption spectrophotometry. Fluoride was analysed using standard procedures and a fluoride ion-specific electrode (no. 960900; Orion Research Inc.). Ca, PO4 and F concentrations are presented in Table 1.
Preparation of enamel specimens Thirty-six caries-free human premolars that had been freshly extracted for orthodontic reasons from 13- to 15-year-old children, with no cracks on the Table 1 pH and concentration of inorganic ions in the tested wine (B. Taillan Bordeaux red). PH
3.9
Calcium concentration (mg/l)
Phosphate concentration (mg/l)
Fluoride concentration (mg/l)
139
326
2.9
buccal side as viewed under a stereomicroscope, were selected from a pool of extracted teeth. They had been stored in distilled water. The chosen teeth were washed with distilled water and air-dried. Each tooth was then embedded in epoxy resin (BuehlerÕ, Lake Bluff, Illinois, USA) and positioned with the buccal bulge exposed above the level of the liquid resin. After the resin had set, the buccal aspects of the crowns were serially polished with 600—1200-grit wet silicone-carbide paper discs on a polishing machine (Struers, Copenhagen, Denmark) under water cooling. The surfaces were ground until an area of enamel of about 4 mm diametre in the mid-central region had been smoothed, according to the method used by.14 They were then polished with a 1 mm diamond abrasive on Struers polishing cloth. Between the two polishing steps and after the final polishing, all samples were sonicated for 5 min in distilled water. All the specimens were then washed and stored in distilled water.
Vickers hardness measurements Twelve baseline measurements of Vickers microhardness (HMV 2000 microhardness tester; Shimadzu Europa, Duisburg, Germany) were spread uniformly over the entire flat area on the buccal surface of each sample under a load of 200 g over 10 s. Then, 30 specimens were immersed in 10 ml of wine for 10 s under constant shaking at 37 8C. Three teeth were used as positive controls and were immersed in Coca-ColaTM; three other teeth were used as negative controls and were immersed in distilled water. All the teeth were then sonicated in distilled water and dried in air. Twelve measurements of Vickers microhardness were performed again on the same surface. The same experiments were reproduced with the same teeth with 10, 30, 90 and 120 s of immersion time in the different liquids.
Scanning electron microscopy In order to observe the enamel surface at each step, four specimens were specially selected at t ¼ 0 and after 10, 30 and 90 s of immersion. They were dried in an oven at 37 8C, sputter-coated with gold and examined in a scanning electron microscope (LV 2003; Jeol Ltd., Tokyo, Japan). The surfaces were photographed at a magnification of 500.
Statistics The Student’s t-test (for the 30 teeth immersed in the wine) and the Wilcoxon test for paired data (control groups) were used to analyse differences in Vickers microhardness measurements before and
In vitro action of Bordeaux red wine on the microhardness of human dental enamel
143
Figure 1 Vickers microhardness test results at different immersion times. Table 2
Vickers microhardness after each immersion time in control groups.
Immersion time (s)
Distilled water (mean S.D.)
0 10 30 90 120
317.8 332.8 321.9 324.0 325.3
27.0 30.1 27.2 20.6 29.5
P
10 s/0 s: NS 30 s/10 s: NS 90 s/30 s: NS 120 s/90 s: NS
after the different immersion times in the liquids. Unpaired data were analysed using ANOVA, Fisher’s PLSD and the Mann—Whitney U-test (Statview; Abacus concepts Inc., Berkeley, CA, USA). The significance level chosen in all statistical tests was 0.05.
Results Wine analysis The pH measured by the pH meter was 3.9.
Coca-ColaTM (mean S.D.) 324 20.6 286.6 22.7 254.3 17.0 229.9 22.6 206.7 19.4
P
10 s/0 s: P < 0.00001 30 s/10 s: P < 0.00001 90 s/30 s: P < 0.0001 120 s/90 s: P < 0.0001
Vickers hardness measurements The results for Vickers microhardness are shown in Fig. 1 for the wine group and in Table 2 for the controls. The mean baseline Vickers hardness number before immersion in the wine ranged between 322:4 14:5 and 352:7 11:9. Overall, the initial Vickers surface microhardness was 338:3 29:4 and there was no statistical significance difference between the teeth at the beginning of the experiments. Hardness of the enamel decreased as the exposure time in the wine and in the cola increased,
Figure 2 Scanning electron micrograph of enamel before immersion in red wine.
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Figure 3
Scanning electron micrograph of enamel after a 90 s immersion in red wine.
suggesting that erosion was progressive over time. However, these differences were not of statistical significance for the wine group, as the Student’s ttest for paired data showed no significant decrease in the surface Vickers microhardness of the teeth before and after a 90 s exposure to the wine (Fig. 1). Therefore, considered on an individual basis, only three teeth showed statistically significant differences between the periods t ¼ 0 and 90 s. When the exposure time was increased to reach 120 s, the decrease in the enamel microhardness was statistically significant (P < 0:01).
Scanning electron microscopic observations At 500 magnification, exposure times of 10 and 30 s produced no signs of erosion; no difference could be seen when these surfaces were compared with those of the control surface (Fig. 2), but there was a small degree of erosion after 90 s immersion in the wine (Fig. 3).
Discussion A Bordeaux red wine was chosen because it is the most frequently drunk wine in France and widely drunk all over the world. Microhardness tests were complemented by scanning electron microscopy of the tooth surface, which allowed us to obtain both a qualitative and quantitative evaluation of the action of the wine on dental enamel. It has been shown that microhardness tests are suitable for determining the small changes in surface microhardness that demonstrate the effect of acids on
enamel and therefore attack by erosion.15 The enamel specimens were ground with 1200-grade silicon-carbide paper so that the smooth surface would highlight the slightest signs of possible erosion. To simulate conditions in the mouth the specimens were kept moist until the moment they were immersed in the wine. They were only dried immediately before preparation for the microhardness measurements and microscopy. Premolars, freshly extracted for orthodontic reasons, were chosen because they had not yet been exposed to much attack in the mouth that could otherwise have altered the enamel and modified its properties. The erosive capacity of different drinks is statistically associated not only with their pH and their phosphorus and fluoride contents but also with the baseline surface microhardness of the exposed enamel.2 In order to determine whether the wine really had erosive potential or not, the same teeth were used throughout the study and the microhardness measurements were performed after different immersion times. The demineralizing effect of the excessive intake of soft drinks, especially of citrus fruits with low pH and other acidic beverages, is well documented.9,10,16 The causative agents are usually acidic substances, the attack rate differing in respect of specific properties of certain acids.2 In the same way, the buffering power of wine has been attributed to the presence of numerous different organic acids.17 Most fruit juices have a lower pH than the tested wine,2 suggesting that wine would be less harmful to enamel. Moreover, the other components of wine, and particularly its calcium, phosphate and fluoride content, could counteract the effects of low pH and make the beverage less
In vitro action of Bordeaux red wine on the microhardness of human dental enamel
harmful than if only the pH were to be taken into consideration (Table 1). In practice, a drink passes quickly through the mouth, except in unusual circumstances, e.g. holding an acid beverage in the mouth before swallowing, which constitutes a risk factor for tooth erosion.18 This effect has been confirmed in several case reports and clinical studies on wine tasters or chronic alcoholics, in whom intensive exposure to wine is linked with significant tooth erosion.1,4,5,12,13 Our negative and positive controls proved that the method was able to show the decrease in the microhardness of dental enamel after immersion in a soft drink known to cause erosion (Coca-ColaTM) and demonstrated that distilled water had no action on this microhardness. After a 90 s immersion in the red wine, there was no overall statistically significant decrease in the microhardness of the tooth surface, but, considered on an individual basis, three teeth showed a decrease in microhardness. This change might be explained either by the specific nature of the enamel in the three teeth, confirming results obtained by Lussi,2 or by the particular donor’s history, such as a problem occurring during the period of posteruptive mineralisation. When the exposure was longer and reached at least 120 s, the overall decrease in enamel microhardness was statistically significant. Therefore, our results suggest that exposure to a French red wine is innocuous for an immersion time of less than 120 s in vitro. Moreover, because of the formation of a pellicle,19 as well as the buffer capacity, pH value and flow rate of saliva, the erosive effect of this drink might be even less under in vivo conditions.3 However, this will be true only for healthy individuals with normal salivary function. For patients with reduced salivary flow, the harmless exposure time to the wine could be lower. It must also be borne in mind that these experiments were conducted on slightly abraded enamel, which is perhaps more susceptible to demineralisation than superficial enamel, in order to perform the microhardness measurements.2 In conclusion, within the constraints of this study, though various fruit juices or carbonated drinks with relatively low pH are known to have an erosive effect on human tooth enamel in a reasonably short time in vitro, wine, which also has a low pH, seems to be harmless. A microhardness study showed no erosion due to the wine over a period of 90 s and nor did scanning electron microscopy show any deterioration of the enamel structure.
145
Acknowledgements We wish to acknowledge Alain Bertrand, wine-making professor in the University of Bordeaux and Jane Magnaldo (English teacher in the University of Nice) for their contribution to the study.
References 1. Smith BGN, Robb ND. Dental erosion in patients with chronic alcoholism. J Dent 1989;17:219—221. 2. Lussi A, Jaeggi T, Scharer S. The influence of different factors on in vitro enamel erosion. Caries Res 1993;27:387—393. 3. Lussi A, Jaeggi T, Jaeggi-Scharer S. Prediction of the erosive potential of some beverages. Caries Res 1995;29:349—354. 4. Ferguson MM, Dunbar RJ, Smith JA, Wall JG. Enamel erosion related to winemaking. Occup Med 1996;46:159—162. 5. Chaudhry SI, Harris JL, Challacombe SJ. Dental erosion in a wine merchant: an occupational hazard? Br Dent J 1997;182:226—228. 6. Zero DT. Etiology of dental erosion–—extrinsic factors. Eur J Oral Sci 1996;104:162—177. 7. Scheutzel P. Etiology of dental erosion–—intrinsic factors. Eur J Oral Sci 1996;104:178—1190. 8. Kunzel W, Cruz MMS, Fisher T. Dental erosion in Cuban children associated with excessive consumption of oranges. Eur J Oral Sci 2000;108:104—109. 9. Lussi A, Kohler N, Zero D, Schaffner M, Megert B. A comparison of the erosive potential of different beverages in primary and permanent teeth using an in vitro model. Eur J Oral Sci 2000;108:110—114. 10. Grando LJ, Tames DR, Cardoso AC, Gabilan NH. In vitro study of enamel erosion caused by soft drinks and lemon juice in deciduous teeth analysed by stereomicroscopy and scanning electron microscopy. Caries Res 1996;30: 373—378. 11. Miller WD. Experiments and observations on the wasting of tooth tissue variously designated as erosion, abrasion, chemical abrasion, denudation, etc. Dent. Cosmos. 49; 1907:109—124, 225—247. 12. Wiktorsson AM, Zimmerman M, Angmar-Mansson B. Erosive tooth wear:prevalence and severity in Swedish winetasters. Eur J Sci 1997;105:544—550. 13. Gray A, Ferguson MM, Wall JG. Wine tasting and dental erosion. Case report. Aust Dent J 1998;43:32—34. 14. Grobler SR, Du Toit IJ, Basson NJ. The effect of honey on human tooth enamel in vitro observed by electron microscopy and microhardness measurements. Arch Oral Biol 1994;39:147—153. 15. Zero DT, Rahbek I, Fu J, Prskin HM, Featherstone JDB. Comparison of the iodide permeability test. Caries Res 1990;24:181—188. 16. Larsen MJ, Nyvad B. Enamel erosion by some soft drinks and orange juice relative to their pH. Caries Res 1999;33:81—87. 17. Ministe `re de l’Economie, des Finances et de l’Industrie. [email protected]. 18. Lussi A, Schaffner M. Progression risk factors for dental erosion and wedge shaped defects over a 6-year period. Caries Res 2000;34:182—187. 19. Hannig M, Balz M. Influence of in vivo formed salivary pellicle on enamel erosion. Caries Res 1999;33:372—379.
In vitro action of Bordeaux red wine on the microhardness of human dental enamel L. Lupi-Peguriera,*, M. Mullera, E. Leforestierb, M.F. Bertrandb, M. Bollac a
Laboratory of Dental Biomaterials and Experimental Odontology, Department of Public Health, Faculty of Odontology, University of Nice-Sophia Antipolis 24, Avenue Des Diables Bleus, 06357 Nice Cedex 4, France b Laboratory of Dental Biomaterials and Experimental Odontology, Department of Conservative Dentistry and Endodontics, University of Nice-Sophia Antipolis 24, Avenue Des Diables Bleus, 06357 Nice Cedex 4, France c Laboratory of Dental Biomaterials and Experimental Odontology, Department of Biomaterials, University of Nice-Sophia Antipolis 24, Avenue Des Diables Bleus, 06357 Nice Cedex 4, France Accepted 9 October 2002
KEYWORDS Dental erosion; French wine; Microhardness; Scanning electron microscopy
Summary Several studies have demonstrated that the regular and large consumption of wine is associated with increased risk of tooth erosion. Here, the effect of Bordeaux red wine on enamel was estimated by measuring changes in its Vickers microhardness. Thirty premolars were used; microhardness tests were performed on buccal areas before and after 10, 30, 90 and 120 s immersion in the wine (pH ¼ 3:9). Enamel surfaces were also observed by scanning electron microscopy. No statistically significant difference was found between the mean Vickers microhardness obtained at t ¼ 0 and 90 s, but slight signs of enamel demineralisation were observed with the scanning electron microscope. It appears that wine has no disastrous effect on the microhardness of dental enamel when the two are in contact for less than 90 s. When the exposure is for at least 120 s, it may become harmful, as the decrease in the microhardness of enamel was then significant (P < 0:05). ß 2003 Elsevier Science Ltd. All rights reserved.
Introduction Erosion is that type of tooth wear, resulting from exposure to non-bacterial chemical attack, that leads to loss of dental hard tissue. Clinically, the demineralised enamel surface is removed, leaving a smooth surface.1—4 Exposure of dentine is often marked by an increase in tooth sensitivity. Eventually the pulp may be exposed. Erosion is almost always caused either by gastric acid or dietary acids, or by acid present in the atmosphere of
Corresponding author. Tel.: þ33-4-92-00-13-18; fax: þ33-4-92-00-12-63. E-mail address: [email protected] (L. Lupi-Pegurier).
the workplace.5 Traditional terminology describes two main patterns: 1. Exogenous erosion caused by extrinsic factors, e.g. dietary, occupational. Usually, the lesions are bilateral, affecting mostly the labial and buccal surfaces of incisors, canines and premolars adjacent to the gingival margin. Approximal and occlusal surfaces may be involved too.6 2. Endogenous erosion caused by an intrinsic factor, i.e. gastric acid. This presents primarily with dissolution of enamel and dentine from the palatal and lingual surfaces of the dentition, with subsequent thinning of the maxillary incisal edges.5,7
0003–9969/03/$ — see front matter ß 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0003-9969(02)00206-6
142
L. Lupi-Pegurier et al.
The frequent consumption of citrus fruits and their juice is well documented as causing erosion,4,8 as are acidic soft drinks.3,4,9,10 Miller11 noted that erosion occurred after exposure of the teeth to organic and inorganic acids. He speculated that, as with fruit juices, regular wine drinking might similarly lead to erosion and demonstrated that decalcification occurred in vitro when human teeth were bathed in a ‘Rhine wine’. Later, several case reports and clinical studies have revealed that regular and heavy wine consumption (up to and including chronic alcoholism) and professional exposure, e.g. in wine tasters, are associated with an increased risk of tooth erosion.1,5,12,13 However, the dental effects of moderate exposure to wine have never, to the best of our knowledge, been studied. France is the second largest wine producer in the world after Italy and over 60 l per capita are consumed annually. Our purpose now was to study the effect of a French red wine, a Bordeaux, on teeth according to time of exposure. Effects were assessed by measuring the Vickers microhardness of the enamel surface and observing changes in the enamel by scanning electron microscopy.
Materials and methods The wine The beverage tested was a Bordeaux red wine (B. Taillan, 1996). Its pH was read with a radiometer PHM 84 pH meter (digit 505; Crison, Barcelona, Spain) fitted with a pH electrode (Fisher Bioblock Scientific, Illkirch, France) at 25 8C. The wine was analysed for phosphorus by the ammonium molybdate method and for calcium by atomic absorption spectrophotometry. Fluoride was analysed using standard procedures and a fluoride ion-specific electrode (no. 960900; Orion Research Inc.). Ca, PO4 and F concentrations are presented in Table 1.
Preparation of enamel specimens Thirty-six caries-free human premolars that had been freshly extracted for orthodontic reasons from 13- to 15-year-old children, with no cracks on the Table 1 pH and concentration of inorganic ions in the tested wine (B. Taillan Bordeaux red). PH
3.9
Calcium concentration (mg/l)
Phosphate concentration (mg/l)
Fluoride concentration (mg/l)
139
326
2.9
buccal side as viewed under a stereomicroscope, were selected from a pool of extracted teeth. They had been stored in distilled water. The chosen teeth were washed with distilled water and air-dried. Each tooth was then embedded in epoxy resin (BuehlerÕ, Lake Bluff, Illinois, USA) and positioned with the buccal bulge exposed above the level of the liquid resin. After the resin had set, the buccal aspects of the crowns were serially polished with 600—1200-grit wet silicone-carbide paper discs on a polishing machine (Struers, Copenhagen, Denmark) under water cooling. The surfaces were ground until an area of enamel of about 4 mm diametre in the mid-central region had been smoothed, according to the method used by.14 They were then polished with a 1 mm diamond abrasive on Struers polishing cloth. Between the two polishing steps and after the final polishing, all samples were sonicated for 5 min in distilled water. All the specimens were then washed and stored in distilled water.
Vickers hardness measurements Twelve baseline measurements of Vickers microhardness (HMV 2000 microhardness tester; Shimadzu Europa, Duisburg, Germany) were spread uniformly over the entire flat area on the buccal surface of each sample under a load of 200 g over 10 s. Then, 30 specimens were immersed in 10 ml of wine for 10 s under constant shaking at 37 8C. Three teeth were used as positive controls and were immersed in Coca-ColaTM; three other teeth were used as negative controls and were immersed in distilled water. All the teeth were then sonicated in distilled water and dried in air. Twelve measurements of Vickers microhardness were performed again on the same surface. The same experiments were reproduced with the same teeth with 10, 30, 90 and 120 s of immersion time in the different liquids.
Scanning electron microscopy In order to observe the enamel surface at each step, four specimens were specially selected at t ¼ 0 and after 10, 30 and 90 s of immersion. They were dried in an oven at 37 8C, sputter-coated with gold and examined in a scanning electron microscope (LV 2003; Jeol Ltd., Tokyo, Japan). The surfaces were photographed at a magnification of 500.
Statistics The Student’s t-test (for the 30 teeth immersed in the wine) and the Wilcoxon test for paired data (control groups) were used to analyse differences in Vickers microhardness measurements before and
In vitro action of Bordeaux red wine on the microhardness of human dental enamel
143
Figure 1 Vickers microhardness test results at different immersion times. Table 2
Vickers microhardness after each immersion time in control groups.
Immersion time (s)
Distilled water (mean S.D.)
0 10 30 90 120
317.8 332.8 321.9 324.0 325.3
27.0 30.1 27.2 20.6 29.5
P
10 s/0 s: NS 30 s/10 s: NS 90 s/30 s: NS 120 s/90 s: NS
after the different immersion times in the liquids. Unpaired data were analysed using ANOVA, Fisher’s PLSD and the Mann—Whitney U-test (Statview; Abacus concepts Inc., Berkeley, CA, USA). The significance level chosen in all statistical tests was 0.05.
Results Wine analysis The pH measured by the pH meter was 3.9.
Coca-ColaTM (mean S.D.) 324 20.6 286.6 22.7 254.3 17.0 229.9 22.6 206.7 19.4
P
10 s/0 s: P < 0.00001 30 s/10 s: P < 0.00001 90 s/30 s: P < 0.0001 120 s/90 s: P < 0.0001
Vickers hardness measurements The results for Vickers microhardness are shown in Fig. 1 for the wine group and in Table 2 for the controls. The mean baseline Vickers hardness number before immersion in the wine ranged between 322:4 14:5 and 352:7 11:9. Overall, the initial Vickers surface microhardness was 338:3 29:4 and there was no statistical significance difference between the teeth at the beginning of the experiments. Hardness of the enamel decreased as the exposure time in the wine and in the cola increased,
Figure 2 Scanning electron micrograph of enamel before immersion in red wine.
144
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Figure 3
Scanning electron micrograph of enamel after a 90 s immersion in red wine.
suggesting that erosion was progressive over time. However, these differences were not of statistical significance for the wine group, as the Student’s ttest for paired data showed no significant decrease in the surface Vickers microhardness of the teeth before and after a 90 s exposure to the wine (Fig. 1). Therefore, considered on an individual basis, only three teeth showed statistically significant differences between the periods t ¼ 0 and 90 s. When the exposure time was increased to reach 120 s, the decrease in the enamel microhardness was statistically significant (P < 0:01).
Scanning electron microscopic observations At 500 magnification, exposure times of 10 and 30 s produced no signs of erosion; no difference could be seen when these surfaces were compared with those of the control surface (Fig. 2), but there was a small degree of erosion after 90 s immersion in the wine (Fig. 3).
Discussion A Bordeaux red wine was chosen because it is the most frequently drunk wine in France and widely drunk all over the world. Microhardness tests were complemented by scanning electron microscopy of the tooth surface, which allowed us to obtain both a qualitative and quantitative evaluation of the action of the wine on dental enamel. It has been shown that microhardness tests are suitable for determining the small changes in surface microhardness that demonstrate the effect of acids on
enamel and therefore attack by erosion.15 The enamel specimens were ground with 1200-grade silicon-carbide paper so that the smooth surface would highlight the slightest signs of possible erosion. To simulate conditions in the mouth the specimens were kept moist until the moment they were immersed in the wine. They were only dried immediately before preparation for the microhardness measurements and microscopy. Premolars, freshly extracted for orthodontic reasons, were chosen because they had not yet been exposed to much attack in the mouth that could otherwise have altered the enamel and modified its properties. The erosive capacity of different drinks is statistically associated not only with their pH and their phosphorus and fluoride contents but also with the baseline surface microhardness of the exposed enamel.2 In order to determine whether the wine really had erosive potential or not, the same teeth were used throughout the study and the microhardness measurements were performed after different immersion times. The demineralizing effect of the excessive intake of soft drinks, especially of citrus fruits with low pH and other acidic beverages, is well documented.9,10,16 The causative agents are usually acidic substances, the attack rate differing in respect of specific properties of certain acids.2 In the same way, the buffering power of wine has been attributed to the presence of numerous different organic acids.17 Most fruit juices have a lower pH than the tested wine,2 suggesting that wine would be less harmful to enamel. Moreover, the other components of wine, and particularly its calcium, phosphate and fluoride content, could counteract the effects of low pH and make the beverage less
In vitro action of Bordeaux red wine on the microhardness of human dental enamel
harmful than if only the pH were to be taken into consideration (Table 1). In practice, a drink passes quickly through the mouth, except in unusual circumstances, e.g. holding an acid beverage in the mouth before swallowing, which constitutes a risk factor for tooth erosion.18 This effect has been confirmed in several case reports and clinical studies on wine tasters or chronic alcoholics, in whom intensive exposure to wine is linked with significant tooth erosion.1,4,5,12,13 Our negative and positive controls proved that the method was able to show the decrease in the microhardness of dental enamel after immersion in a soft drink known to cause erosion (Coca-ColaTM) and demonstrated that distilled water had no action on this microhardness. After a 90 s immersion in the red wine, there was no overall statistically significant decrease in the microhardness of the tooth surface, but, considered on an individual basis, three teeth showed a decrease in microhardness. This change might be explained either by the specific nature of the enamel in the three teeth, confirming results obtained by Lussi,2 or by the particular donor’s history, such as a problem occurring during the period of posteruptive mineralisation. When the exposure was longer and reached at least 120 s, the overall decrease in enamel microhardness was statistically significant. Therefore, our results suggest that exposure to a French red wine is innocuous for an immersion time of less than 120 s in vitro. Moreover, because of the formation of a pellicle,19 as well as the buffer capacity, pH value and flow rate of saliva, the erosive effect of this drink might be even less under in vivo conditions.3 However, this will be true only for healthy individuals with normal salivary function. For patients with reduced salivary flow, the harmless exposure time to the wine could be lower. It must also be borne in mind that these experiments were conducted on slightly abraded enamel, which is perhaps more susceptible to demineralisation than superficial enamel, in order to perform the microhardness measurements.2 In conclusion, within the constraints of this study, though various fruit juices or carbonated drinks with relatively low pH are known to have an erosive effect on human tooth enamel in a reasonably short time in vitro, wine, which also has a low pH, seems to be harmless. A microhardness study showed no erosion due to the wine over a period of 90 s and nor did scanning electron microscopy show any deterioration of the enamel structure.
145
Acknowledgements We wish to acknowledge Alain Bertrand, wine-making professor in the University of Bordeaux and Jane Magnaldo (English teacher in the University of Nice) for their contribution to the study.
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