Erosive potential of beverages sold in Australian schools

Transcription

1 SCIENTIFIC ARTICLE Australian Dental Journal 2009; 54: doi: /j x Erosive potential of beverages sold in Australian schools NJ Cochrane,* F Cai,* Y Yuan,* EC Reynolds* *Centre for Oral Health Science, Melbourne Dental School, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria. ABSTRACT Background: Dental erosion is an increasingly prevalent problem in Australia. The aim of this study was to analyse the composition and erosive potential of beverages sold for consumption in Victorian schools. Methods: Fifteen drinks were selected and analysed to determine their ph, titratable acidity and ionic composition (calcium, fluoride and inorganic phosphate). The erosive potential of the beverages was measured by analysing weight loss, surface loss and the release of calcium ions from human enamel following a 30-minute or 24-hour exposure. The association of the chemical parameters with the measures of erosion was determined using Spearman s rank correlation. Results: All beverages tested except the milks and the bottled water produced significant dental erosion in vitro. The only chemical parameter that correlated significantly with all measures of erosion was the initial ph of the beverage (p < 0.01). Levels of fluoride similar to those of Australian reticulated water were found in the carbonated beverages. Conclusions: The majority of the tested beverages sold from school canteens exhibited erosive potential. Keywords: Dental erosion, fluoride, ph, soft drinks, surface loss, weight loss. Abbreviations and acronyms: CaF 2 = fluorite; DS = degree of saturation; FA = fluorapatite; HA = hydroxyapatite; KOH = potassium hydroxide; SL = surface loss; WL = weight loss. (Accepted for publication 21 December 2008.) INTRODUCTION Dental erosion is the loss of tooth structure by acid dissolution that does not involve bacteria. 1 Evidence suggests that the prevalence of erosion is steadily increasing. 2 A recent examination of 714, 6- to 15- year-old students from eight Australian schools found that 68 per cent had at least one tooth that exhibited signs of erosion. 3 This was higher than seen in studies of children in other first world populations with prevalence of 41 per cent in the United States 4 and moderate erosion in 51 per cent in the United Kingdom. 5 Given this high and growing prevalence, understanding the erosion process and identifying foods and beverages with high potential erosivity is essential. The consumption of soft drinks has consistently been linked with dental erosion and is considered one of the most important risk factors. 6 8 A recent governmentcommissioned survey of 900, 12- to 17-year-old school children in Victoria found that approximately 80 per cent consumed sugar-containing soft drinks regularly. The proportion of students who drank three, two, one or no cans of high sugar soft drink per day was 10 per cent, 35 per cent, 37 per cent and 18 per cent, respectively. 9 In the USA, consumption of acidic drinks has increased by 300 per cent in the past 20 years, and the serving sizes have grown from 185 g in the 1950s, to 240 g in the 1960s and up to 500 g in the late 1990s. 10 The USA offers a reasonable comparison to Australia as a developed country enjoying a similar popular culture. The increase in consumption of soft drinks has been identified as a contributing factor in dental caries, 11 obesity 12,13 and diabetes. 14 This has prompted the Victorian State Government to ban the sale of high sugar-containing beverages from primary and secondary Australian state school canteens and vending machines. Sugar-free alternatives will continue to be available, as will fruit juices that are not artificially sweetened. 15 This ban has not been introduced to tackle the dental issues of high soft drink consumption although positive effects on reducing dental caries amongst school children may be seen. Further information is required to determine whether banning high sugar-containing drinks will have a positive effect on reducing dental erosion. Seow and Thong 16 reported on the ph, degree of etching and Vickers hardness of a range of Australian beverages but did not examine their titratable acidity, calcium, inorganic phosphate or fluoride content. These 238 ª 2009 Australian Dental Association

2 Erosive potential of school beverages beverage parameters are known to influence their erosivity but, to the authors knowledge, no studies of Australian beverages have reported this information in the context of their dental erosivity. Therefore, the aim of this study was to analyse the composition and erosive potential of the common beverages sold for consumption in Victorian schools. MATERIALS AND METHODS Beverage selection and preparation Fifteen beverages common to the canteens of three Victorian high schools were selected for analysis (Table 1). Two plastic bottles of each beverage were purchased. A freshly opened bottle was used for analysis to avoid loss of carbon dioxide from the carbonated beverages. For the calcium, inorganic phosphate and fluoride ion analyses some beverages contained protein or solid material which were removed prior to analysis. Milkbased beverages (Pura Milk and Big M) were diluted 1:5 with distilled deionized water and deproteinated by mixing 1:1 with 24% trichloracetic acid. After 30 minutes the solution was filtered through No. 2 Whatman paper. Fruitopia orange juice, Deep Spring and Solo samples were centrifuged (JA 12 rotor, 7000 rpm, 10 C, 30 minutes) and the supernatant filtrated through a 0.2 lm Sartorius membrane. Chemical analysis The 15 beverages were randomly coded to ensure blind analysis with respect to fluoride, calcium and inorganic phosphate. Each sample of beverage was analysed in duplicate. The ph and titratable acidity of the beverages were measured immediately after opening the bottles. A 5 g sample was stirred in a TTA80 titration assembly (Radiometer, Copenhagen, Denmark), and the initial ph taken using a G2040 glass electrode and PHN 82 Standard ph Meter (Radiometer, Copenhagen, Denmark). Using an ABU80 autoburette with a TTT80 titrator (Radiometer, Copenhagen, Denmark), 0.1 M potassium hydroxide (KOH) was added to bring the ph to 5.5 and then to 7.0. The volume of KOH added was measured in millilitres and recorded to obtain the titratable acidity. The beverages were decarbonated overnight and the ph measured (Eutech Instruments ph 510 Cyberscan ph meter). Undiluted samples were mixed 1:1 with total ionic strength adjustment buffer (TISAB, Merck, Darmstadt, Germany) and analysed with a fluoride ion-specific electrode (Radiometer Ion85 ion analyser, Copenhagen, Denmark). 17 Calcium was determined in the initial beverages and then again after 24-hour exposure to enamel using atomic absorption spectrophotometry. 18 Inorganic phosphate was determined in the initial beverages using the molybdate malachite colorimetric method of Itaya and Ui. 19 Table 1. The selected beverages and the manufacturer, ingredients, and grouping Beverage name Grouping Ingredient list Coca-Cola Sugar-containing carbonated water, sugar, colour (150d), food acid (338), flavours, caffeine Pepsi carbonated beverages carbonated water, sugar, colour (150d), food acid (338), flavours, caffeine Solo carbonated water, sugar, reconstituted lemon juice (5%), food acids (330, 331), flavour, preservatives (211, 223), colour (102) Sprite carbonated water, sugar, food acids (330, 331), flavour, preservative (211) Deep Spring Sparkling natural mineral water, sugar, orange juice (3%), lemon juice (1%), lime juice (1%), flavours, food acid (330), preservative (211), colour (102) Coca-Cola Zero Non-sugar-containing carbonated beverages carbonated water, colour (150d), food acids (338, 331), flavour, sweeteners (951, 950), preservative (211), caffeine Pepsi Max carbonated water, colour (150d), sweeteners (951, 950), food acids (338, 330), preservative (211), flavour, caffeine Sprite Zero carbonated water, food acids (330, 331), flavour, sweeteners (951, 950), preservative (211) Diet Coca-Cola carbonated water, flavour, colour (150d), food acids (338, 330), sweeteners (951, 950), preservative (211), caffeine Powerade Sports drinks water, sucrose, maltodextrin, food acids (330, 331), flavour, tripotassium citrate, sodium chloride, colour (129), tripotassium phosphate Gatorade water, sucrose, glucose, food acids (330, 331), monopotassium phosphate, sodium chloride, flavour, colour (129) Pura Milk Milk drinks milk Big M (chocolate) milk, sugar, milk solids non fat, cocoa powder (min 0.25%), flavours, colours (155, 133) Mount Franklin Not grouped Australian spring water Fruitopia (Orange Juice) orange juice (from concentrate 99.8%), flavour, vitamin C As listed on the beverage bottles. Food acid: 330 = Citric acid, 331 = Sodium citrate, 338 = Phosphoric acid; Colours: 150d = Caramel IV, 102 = Tatrazine, 155 = Brown HT, 133 = Brilliant blue FCF, 129 = Allura red AC; Preservatives: 221 = Sodium benzoate, 223 = Sodium metabisulphite; Sweeteners: 951 = Aspartame, 950 = Acesulphame potassium. ª 2009 Australian Dental Association 239

3 NJ Cochrane et al. The ph, calcium, inorganic phosphate and fluoride concentrations in the original beverages were entered into an iterative computational procedure to calculate the ion activities of the various species present in solution using the expanded Debye-Huckel equation. 18 Ionic strength was estimated from the labelled ion content. The ion activities were then used to determine the apparent degree of saturation (DS) with respect to hydroxyapatite (HA), fluorapatite (FA) and fluorite (CaF 2 ) using the equation DS = (IAP Ksp) 1 n where IAP is the ion activity product, Ksp the solubility product of the solid phase and n equals the number of ions in a unit cell. Erosion analysis Preparation of enamel blocks Ninety extracted human molars free of dental caries, cracks, hypomineralized defects or any other surface irregularities were collected from the Royal Dental Hospital of Melbourne with ethics approval from the University of Melbourne Human Research Ethics Committee (HREC # ). The teeth were separated into two groups, one group (n = 45) prepared for weight loss (WL) and calcium change (DCa) erosive measurements and the other group (n = 45) for surface loss (SL) as measured by white-light non-contact surface profilometry. The teeth to be analysed by WL and DCa were polished (3M ESPE Sof-Lex TM discs) to remove the variable fluoride rich surface layer (50 lm) and sectioned on a Minitom (Struers, Denmark) to obtain enamel blocks of either the buccal, palatal or approximal surface. The blocks were coated in nail varnish (Revlon Love That Red 670, NY, USA) leaving an approximately 3 3 mm window of enamel. This area of exposed enamel was digitally photographed and the exact area calculated using Olysia BioReport (Soft Imaging System GmbH v3.2 Build 777). The varnished blocks were placed in a desiccator containing silica gel for 24 hours and their weight recorded. The teeth to be analysed by surface profilometry were cut into blocks and embedded in epoxy resin (EpoFix, Struers, Denmark), and lapped with SiC paper (Struers, Denmark) and diamond pastes (Struers, Denmark) to expose an approximately 3 3 mm enamel window. The embedded blocks were pre-scanned using whitelight non-contact surface profilometer (Altisurf 500, Cotec, France) and only included in the study if the roughness was < 0.1 lm. Following inclusion the enamel was painted with nail varnish (Revlon Love That Red 670, NY, USA), to create a 1 1mm window that was exposed to the beverages for a 30-minute erosive challenge. Erosive challenge Each embedded and unembedded enamel block was attached to the side of a polypropylene tube with sticky wax (Model Cement, Kemdent) with one enamel block per tube. Six 40 ml samples of each freshly opened beverage (90 samples total) were tested (three samples of each beverage with unembedded enamel blocks and three samples of each beverage with embedded blocks). The beverage samples and enamel blocks were incubated at 19 C (HT infors, MINITRON, Incubator Shaker, 120 rpm). This temperature (19 C) was the mean value experimentally determined by four subjects rinsing one of the beverages stored at 4 C for 15 seconds. After 30 minutes of incubation, the 45 embedded blocks were removed and re-scanned twice using white-light non-contact surface profilometry to determine the amount of SL in micrometres. After 24 hours, the remaining 45 varnish-coated unembedded blocks were also removed, desiccated as described above and reweighed. The beverage samples from the 24-hour WL challenge were chemically analysed as described previously to determine the DCa. Statistical analysis SPSS software (version 14.1) was utilized for the statistical analysis. Spearman s rank correlation was determined for each of the chemical parameters of the beverages with each of the three measures of erosion (WL, DCa and SL). 20 The three measures of erosion were also correlated with each other using Spearman s rank correlation. Differences in parameters for each beverage group were analysed using an ANOVA with a Tukey post hoc. 20 RESULTS The beverages purchased for analysis are shown in Table 1 along with the manufacturer and the ingredients listed on the bottles. Of the 15 drinks, nine were carbonated (five sugar-containing and four sugar-free), two were sports drinks, two were milk drinks, one fruit juice and one bottled water. Chemical parameters of the beverages The ph, calcium, inorganic phosphate and fluoride concentrations of these beverages are shown in Table 2. The initial ph of the beverages ranged from 2.36 (Pepsi) to 6.73 (Pura Milk) with all beverages excluding the milks and the bottled water between 2.36 and The ph of all carbonated beverages was found to increase following decarbonation by an average of 0.31 ± 0.10 ph units. The beverages contained variable 240 ª 2009 Australian Dental Association

4 Erosive potential of school beverages Table 2. The ph, calcium, inorganic phosphate and fluoride concentrations, titratable acidity and degree of saturation with respect to hydroxyapatite (DS HA ), fluorapatite (DS FA ) and fluorite (DSCaF 2 ) of the beverages, and their correlations with weight loss (WL), surface loss (SL) and change in calcium (DCa) Beverage ph (initial) ph (decarbonated) Calcium (mm) Phosphate (mm) Fluoride (ppm) Titratable acidity (mm) DS HA DS FA DSCaF 2 fi ph 5.5 fi ph 7.0 Pepsi 2.36à 2.78à 0.15à 5.45à 0.51à 8.22à 18.43à Coca-Cola Solo Pepsi Max Coca-Cola Zero Sprite Sprite Zero Diet Coca-Cola Deep Spring Powerade Gatorade Fruitopia Mount Franklin Big M N A Pura Milk N A Correlation with WL 0.89* 0.88* ns ns ns ns ns ns ns ns Correlation with SL 0.80* 0.79* ns ns ns )0.62* ns ns ns ns Correlation with DCa 0.89* 0.87* ns ns ns ns ns ns ns ns àmean of duplicate assays. ph was converted to [H + ] and the association to WL, SL and DCa determined. *p < concentrations of calcium and inorganic phosphate ions. The milks contained the highest concentration of both calcium and inorganic phosphate ions, followed by the orange juice. All carbonated and sports beverages contained less than 0.71 mm calcium ions. The concentration of inorganic phosphate ions in the carbonated and sports beverages was found to vary between undetectable and 6.69 mm. Fluoride ions were detected in all beverages with a range of 0.03 to 1.05 ppm. The bottled water was found to have the lowest titratable acidity (0.08 and 0.21 mm of KOH to raise the ph to 5.5 and 7.0, respectively) and orange juice had the highest (69.27 and mm of KOH to raise the ph to 5.5 and 7.0, respectively). Using the measured ionic concentrations of calcium, inorganic phosphate and fluoride and the solution ph it could be calculated that all of the beverages were undersaturated with respect to HA, FA and CaF 2 except the milk drinks, which were highly supersaturated with respect to HA and FA. Erosive potential The WL, SL and DCa produced by the beverages is presented in Table 3. Coca-Cola and Pepsi showed the highest erosivity according to all three measures whereas the milks and water showed little to no erosion. The three measures of erosion were correlated with each other to assess their relationship (Table 3). Table 3. The weight loss (WL), surface loss (SL) and change in calcium (DCa) produced by the beverages (ranked by WL) WL (mg mm 2 ) SL (lm) DCa (lmol mm 2 ) Coca-Cola 0.79à ± à ± à ± 1.89 Pepsi 0.73 ± ± ± 1.94 Solo 0.61 ± ± ± 2.14 Pepsi Max 0.51 ± ± ± 0.47 Sprite Zero 0.40 ± ± ± 0.31 Gatorade 0.40 ± ± ± 0.77 Coca-Cola Zero 0.39 ± ± ± 1.44 Deep Spring 0.38 ± ± ± 2.41 Sprite 0.31 ± ± ± 0.55 Diet Coca-Cola 0.30 ± ± ± 0.44 Powerade 0.25 ± ± ± 0.18 Fruitopia 0.20 ± ± ± 1.99 Pura Milk 0.03 ± NA Mount Franklin 0.01 ± ± 0.02 Big M )0.01 ± ± 0.00 NA Correlation with WL 1.00* 0.82* 1.00* Correlation with SL 0.82* 1.00* 0.74* Correlation with DCa 1.00* 0.74* 1.00* àmean ± SD (n = 3). *All correlations significant (p < 0.01). Significant correlations were found between all measures of erosion (r > 0.74, p < 0.01) with the highest being between WL and DCa (r = 1.00). Correlations of erosion to chemical parameters The association of each of the nine chemical parameters characterized in Table 2 with each of the three measures of erosion were determined using Spearman s ª 2009 Australian Dental Association 241

5 NJ Cochrane et al. Table 4. The grouped ph, weight loss (WL), surface loss (SL) of the selected beverages ph (initial) WL (mg mm 2 ) SL (lm) Sugar-containing 2.72 ± 0.32,à 0.57 ± 0.22,à 4.18 ± 2.10,à carbonated beverages Non-sugarcontaining 2.97 ± ± ± 1.55 carbonated beverages Sports drinks 3.24 ± 0.05à, 0.33 ± 0.10à 2.37 ± 0.96à Milk drinks 6.69 ± 0.04,, 0.01 ± 0.03, 0.07 ± 0.13, Values in same column marked with same symbol (, à,, ) are significantly different (p < 0.05) (n = 6 15). rank correlation. The only statistically significant correlations between the measures of erosion and the chemical parameters were between the initial and decarbonated ph values and all measures of erosion (r = 0.79, p < 0.01), and between surface loss and titratable acidity to ph 5.5 (r = )0.62, p < 0.05). Grouping summary The average ph, WL and SL for each of the four defined beverage groups are shown in Table 4. There were no significant differences between the initial ph or the two measures of erosion between the sugar and non-sugar-containing carbonated beverages. All carbonated beverages had significantly different ph and erosivity compared with the milk drinks. The sports drinks were significantly different to the sugar-containing carbonated beverages but not significantly different to the non-sugar-containing carbonated beverages. DISCUSSION Of the 15 beverages selected from Victorian schools, all produced significant erosion of dental enamel except the two milk drinks and the bottled water as measured by WL, SL and DCa. Coca-Cola is sold throughout the world and has therefore been analysed in a variety of erosion studies. The ph has been reported in several studies as being between 2.3 to ,16 In this study, care was taken to measure the ph immediately after opening the bottle as release of carbon dioxide has an effect on beverage ph. Larsen and Nyvad 8 also reported measuring ph immediately after bottle opening and obtained a ph measurement of 2.4 matching closely that obtained in this study. Larsen and Nyvad 8 also analysed the majority of the other chemical parameters tested in this study and found similar results except for the calcium and fluoride concentrations. The values obtained by Larsen and Nyvad 8 were titratable acidity to ph 5.5 and 7.0, 9 mm and 25 mm, respectively and calcium, inorganic phosphate and fluoride ion concentrations 0.26 mm, 5.47 mm, and 0.2 ppm, respectively. The different calcium and fluoride concentrations in Coca-Cola likely reflect differences in the local water supplies used to produce the beverages. This variation in a branded beverage produced in different localities has been reported previously by Heilman et al. 21 The range of ph values observed in the beverages studied may be explained by the varying composition of acids present within them. Different types of food acids are added to beverages to improve their organoleptic properties. Milk and water have no added acids, but the orange juice contained ascorbic acid (vitamin C) in addition to its naturally occurring citric acid, while all the carbonated and sports drinks in the study contained added food acids (Table 1). The carbonation of certain beverages appeared to influence their ph (Table 2). The carbonation process incorporates pressurized carbon dioxide (CO 2 ) into water (H 2 O) that produces carbonic acid (H 2 CO 3 ), thereby further lowering the ph of the beverage. Of the 15 beverages tested, the nine carbonated beverages had the lowest ph with release of the carbon dioxide increasing the ph by an average of 0.31 ± 0.10 units. The buffering capacity of a solution is defined as its ability to resist changes in ph when an acid or base is added, and may be expressed as the change in titratable acidity per unit change in ph. While ph is the equilibrium measure of the free hydrogen ion concentration in solution, titratable acidity measures the total available hydrogen ion concentration, and includes both free and undissociated (bound) hydrogen ions from acids that can be neutralized by a strong base such as potassium hydroxide. Many of the beverages had a high titratable acidity (Table 2). All carbonated and sports drinks contained either phosphoric acid, citric acid or sodium citrate or a combination of these food acids. Phosphoric and citric acid are triprotic acids that can release up to three hydrogen ions in solution. Both phosphate and particularly citrate can also sequester calcium ions. Mount Franklin bottled water had a ph of 4.65 and this was attributed to carbonation and or naturally present mineral acids in the spring water. All beverages except for Fruitopia orange juice and the milks had a calcium concentration under 1 mm. A number of the soft drinks had higher inorganic phosphate concentrations, however, this corresponded to those with phosphoric acid as an added ingredient. The presence of significant concentrations of fluoride in the beverages was an unexpected finding. The two milks, Mount Franklin water and Deep Spring all had low fluoride concentrations. The fluoride concentration of bovine milk has been reported to be in the range of 0.03 to 0.06 ppm which is in agreement with the results of this study. 22 Deep Spring lists natural mineral water 242 ª 2009 Australian Dental Association

6 Erosive potential of school beverages as an ingredient and a recent analysis of bottled waters also found low fluoride concentrations. 17 When these beverages were removed, the average fluoride concentrations in the remaining beverages was 0.72 ± 0.16 ppm which falls within the Australian target for water fluoridation of 0.7 to 1.0 ppm fluoride. 23 Heilman et al. 21 examined the fluoride levels in carbonated beverages sold in the USA and made a similar finding with the majority of tested beverages having fluoride levels in excess of 0.60 ppm. They attributed this to the water used in production of the beverages. Dental erosion should not occur when the DS with respect to enamel mineral of the solution in contact with the enamel is greater than one. 24 The calcium, inorganic phosphate, fluoride and hydroxide concentrations were used to determine the apparent DS with respect to HA and FA. All beverages that were undersaturated with respect to HA and FA produced erosion as measured by WL, SL and DCa. However, the amount of erosion was not correlated with the apparent DS. This contrasts with Jensdottir et al. 25 who found a significant correlation between DS HA and DCa. Similarly, no significant correlation was found between DS HA and WL. 25 As the majority of the beverages were highly undersaturated with respect to apatite and some of the beverages contained citrate, that would chelate calcium and hence not allow accurate determinations of DS, then this may help explain why no correlation of apparent DS with erosive potential was found in the current study. No significant correlation between erosive potential and the calcium and inorganic phosphate content of the beverages tested was found either. This is in agreement with the findings of Jensdottir et al. 25 Additionally, the beverage fluoride concentration was not correlated to any of the measures of erosion. As all of the beverages that produced measurable erosion were undersaturated with respect to FA and CaF 2, the fluoride content of the beverage was alone insufficient to prevent erosion. This is in agreement with the findings of Larsen and Richards 26 who found that only high concentrations of fluoride were able to prevent erosion when the beverage was supersaturated with respect to calcium fluoride. The ph of the beverage was found to correlate with all measures of erosion (r > 0.80, p < 0.01). In this study, the titratable acidity showed no relationship to any measures of erosion except the titratable acidity to ph 5.5, which correlated with SL (r = )0.62, p < 0.05) but not with WL or DCa. Other researchers have had similar difficulties in obtaining significant correlations between this chemical parameter and erosion in vitro. Larsen and Nyvad 8 were unable to show a significant correlation between titratable acidity and WL. Jensdottir et al. 25 found a correlation between titratable acidity with 24-hour WL but could not correlate it with DCa. Titratable acidity is important, however, as can be seen in this study with the bottled water sample (Mount Franklin) which had a low ph (4.65) but negligible titratable acidity and hence no effective erosive potential. The in vivo environment contains many buffers in saliva and plaque that may neutralize acid and therefore beverage titratable acidity would have a greater role. Beverages with high titratable acidity would be better able to maintain a low ph and therefore a state of undersaturation necessary for the erosion process to progress. In vitro studies of erosion have used WL, surface profilometry and or DCa to quantify the effect of various foods and beverages. 25,27 Frequently, WL is the measure of choice due to its simplicity although long treatment durations are necessary to produce measurable changes. In this study, the three methods of WL, SL and DCa were compared. As surface profilometry has a high resolution, the duration of exposure could be reduced. All measures of erosion correlated highly with each other (r > 0.74, p < 0.01), justifying the use by other authors of one measure as an indicator of erosion. It is acknowledged that the in vitro environment studied would exaggerate the erosive potential of the beverages as it lacked the intrinsic buffering systems of saliva and the presence of plaque and pellicle that has been shown to provide a surface protective effect. 28 Hence, caution is required in extrapolating these results to the intraoral environment although the relative erosivity of the beverages should be a useful guide. This study revealed no significant differences between the ph or erosivity of sugar and non-sugar-containing carbonated drinks. Therefore, banning sugar-containing beverages from schools may have positive health effects for reducing obesity, diabetes and dental caries but it may not reduce the risk of dental erosion. CONCLUSIONS The greatest determinant of erosive potential identified in this study was the ph of the beverage. Other factors such as calcium, inorganic phosphate and fluoride content and titratable acidity showed little correlation with erosion in this in vitro model. This study found no significant differences in erosivity between sugar and non-sugar-containing carbonated beverages. ACKNOWLEDGEMENTS The authors would like to acknowledge P Chen, N Liew, H Navani, S Shastri, S Taylor and F Yang for their contributions as part of their undergraduate Bachelor of Dental Science course. Additionally, they would like to thank Glenn Walker for statistical advice and John Ward of CSIRO Forestry and Forest Products ª 2009 Australian Dental Association 243

7 NJ Cochrane et al. for assistance with non-contact profilometry. This study was supported by The Melbourne Dental School at the University of Melbourne. REFERENCES 1. Zipkin I, McClure FJ. Salivary citrate and dental erosion. J Dent Res 1949;28: Moss SJ. Dental erosion. Int Dent J 1998;48: Kazoullis S, Seow WK, Holcombe T, Newman B, Ford D. Common dental conditions associated with dental erosion in schoolchildren in Australia. Pediatr Dent 2007;29: Deery C, Wagner ML, Longbottom C, Simon R, Nugent ZJ. The prevalence of dental erosion in a United States and a United Kingdom sample of adolescents. Pediatr Dent 2000;22: Al-Dlaigan YH, Shaw L, Smith A. Dental erosion in a group of British 14-year-old, school children. Part I: Prevalence and influence of differing socioeconomic backgrounds. Br Dent J 2001;190: Tahmassebi JF, Duggal MS, Malik-Kotru G, Curzon MEJ. Soft drinks and dental health: a review of the current literature. J Dent 2006;34: Jarvinen VK, Rytomaa II, Heinonen OP. Risk factors in dental erosion. J Dent Res 1991;70: Larsen MJ, Nyvad B. Enamel erosion by some soft drinks and orange juices relative to their ph, buffering effects and contents of calcium phosphate. Caries Res 1999;33: Austin P. Sugary drink ban in schools not enough. The Age. 24 April Cavadini C, Siega-Riz AM, Popkin BM. US adolescent food intake trends from 1965 to Arch Dis Child 2000;83: Erratum in: Arch Dis Child 2002;87: Heller KE, Burt BA, Eklund SA. Sugared soda consumption and dental caries in the United States. J Dent Res 2001;80: Gill TP, Rangan AM, Webb KL. The weight of evidence suggests that soft drinks are a major issue in childhood and adolescent obesity. Med J Aust 2006;184: Ludwig DS, Peterson KE, Gortmaker SL. Relation between consumption of sugar-sweetened drinks and childhood obesity: a prospective, observational analysis. Lancet 2001;357: Schulze MB, Manson JAE, Ludwig DS, et al. Sugar-sweetened beverages, weight gain, and incidence of type 2 diabetes in young and middle-aged women. J Am Med Assoc 2004;292: Victorian State Government. Back to school Seow WK, Thong KM. Erosive effects of common beverages on extracted premolar teeth. Aust Dent J 2005;50: Cochrane NJ, Saranathan S, Morgan MV, Dashper SG. Fluoride content of still bottled water in Australia. Aust Dent J 2006;51: Cochrane NJ, Saranathan S, Cai F, Cross KJ, Reynolds EC. Enamel subsurface lesion remineralisation with casein phosphopeptide stabilised solutions of calcium, phosphate and fluoride. Caries Res 2008;42: Itaya K, Ui M. A new micromethod for the colorimetric determination of inorganic phosphate. Clin Chim Acta 1966;14: Sokal R, Rohlf F. Biometry. San Francisco: WH Freeman and Co, 1969: Heilman JR, Kiritsy MC, Levy SM, Wefel JS. Assessing fluoride levels of carbonated soft drinks. J Am Dent Assoc 1999;130: Fomon SJ, Ekstrand J. Fluoride intake. In: Fejerskov O, Ekstrand J, Burt BA, eds. Fluoride in dentistry. 2nd edn. Copenhagen: Munksgaard, 1996: National Health and Medical Research Council. Australian drinking water guidelines. Fact sheet No. 51. Canberra: Commonwealth of Australia, Larsen MJ. Chemical events during tooth dissolution. J Dent Res 1990;69 Spec No: ; discussion Jensdottir T, Bardow A, Holbrook P. Properties and modification of soft drinks in relation to their erosive potential in vitro. J Dent 2005;33: Larsen MJ, Richards A. Fluoride is unable to reduce dental erosion from soft drinks. Caries Res 2002;36: West NX, Hughes JA, Addy M. Erosion of dentine and enamel in vitro by dietary acids: the effect of temperature, acid character, concentration and exposure time. J Oral Rehabil 2000;27: Amaechi BT, Higham SM, Edgar WM, Milosevic A. Thickness of acquired salivary pellicle as a determinant of the sites of dental erosion. J Dent Res 1999;78: Address for correspondence: Professor EC Reynolds Centre for Oral Health Science Melbourne Dental School The University of Melbourne 720 Swanston Street Melbourne VIC e.reynolds@unimelb.edu.au 244 ª 2009 Australian Dental Association