Statistical analysis of salivary ph changes after the intake of black tea and yerba mate supplemented with sweeteners

Transcription

1 Journal of Oral Science, Vol.41, No.2, 81-85, 1999 Statistical analysis of salivary ph changes after the intake of black tea and yerba mate supplemented with sweeteners Marla Elena Lopez de Bocanera, Myriam Adriana Koss de Stisman, Elena Bru de LabandaƒÌ and Amalia Chervonagura de Gepner Catedra de Qulmica BiolOgica, Facultad de Odontologla, Universidad Nacional de Tucuman (U.N.T.), Tucuman, ArgentinaƒÌCERELA (Centro de Referencia para Lactobacilos) (Received 20 October 1998 and accepted 27 May 1999) Abstract: Many studies have demonstrated the effect of various beverages on hard tissues of the mouth. Sugar consumption has also been avoided because it is associated with caries activity, and artificial sweetener research has been promoted. In this paper, data about the buffer capacity of black tea and yerba mate supplemented with sugar or one of two artificial sweeteners (Barny diet and NutraSweet) were examined. Salivary ph variations after the ingestion of both infusions were statistically analysed. A factorial design of four variables (Infusion, Sweetener, Concentration and Time) and their effects were considered independently and combined. The addition of sucrose lowered the ph of the infusions while black tea showed a greater buffer capacity than yerba mate. Significant differences (p < ) were obtained when salivary ph values were compared between infusions supplemented with sugar or artificial sweeteners. When a factorial design was used to examine differences between Barny diet and NutraSweet, no significant two- or three-way interactions could be observed. This statistical analysis showed a small significant variation in salivary ph after the ingestion of black tea or yerba mate with sugar but not with artificial sweeteners at the recommended concentrations. (J. Oral Sci. 41, 81-85, 1999) Key words: factorial design; saliva; ph; sugar; artificial sweeteners; mate; tea. Introduction There exists a growing knowledge of the importance of saliva in oral and dental health since its components and its ph are some of the factors involved in the development of caries (1). Salivary ph indicates the hydrogen ion concentration present in the saliva solution, thus allowing a calculation of acidic or alkaline saliva characteristics. Average ph of saliva at rest is about 6.8, and varies between 6.5 and 7.0. In non-stimulated saliva or when flow is low, chloride is the predominant ion Correspondence to Dr. Maria E. Lopez de Bocanera, Avenida Benjamin Ardoz 800,(4000) S.M. de Tucuman, Argentina and there are only traces of bicarbonate, resulting in a lower ph. This low bicarbonate content results in saliva being a less powerful buffer. Diurnal variations affect the buffering capacity of saliva, which is highest in the morning (2). These properties of saliva are important in the maintenance of the integrity of oral tissues. Most fruit juices and drinks have a ph low enough to induce erosion of the enamel surface (3). Their sugar content is also responsible for dissolution of hydroxyapatite after bacterial fermentation. In recent years, artificial sweeteners have been used in caries prevention (and also as sugar-free medicine products (4) because their low levels of calories). Some work has also been examining the erosion property of beverages with sugar or artificial sweeteners (3,5). In contrast, tea is known for its anti-cariogenic properties since it produces the inhibition of glucosyl transferase and sucrose-dependent bacterial cell adherence (6). Tea contains polyphenols, which are also components of yerba mate, a beverage of low cost commonly drunk in South America. Yerba mate is called "green tea" in other parts of the world. Barny diet and NutraSweet, the sweeteners employed in this work, are frequently consumed artificial sweeteners, composed of saccharin-cyclamate and aspartame, respectively. They are used to sweeten coffee, tea or other drinks. However, people use these products less because of dental health care, but rather mostly because of obesity or diabetes problems (4). Thus, the aim of this work was: a) to compare the ph and the buffer capacity of black tea and yerba mate supplemented with sugar or each of two artificial sweeteners (Barny diet and NutraSweet), and b) to analyse statistically the most important factors that modify temporary salivary ph after the ingestion of both infusions supplemented with sugar and the two artificial sweeteners at two different concentrations. Materials and Methods Sweeteners Commercial sucrose and two types of artificial sweeteners (Barny diet, liquid) and (NutraSweet, powder) were used. They were added at two different concentrations to infusions of black tea and yerba mate. The chemical composition of Barny diet was (mg of compound/ml demineralized water) 80 mg sodium cyclamate,

2 82 20 mg sodium saccharin, 100 mg dextrose, and 10 mg methylparabene. NutraSweet contained (per g of product) an unspecified amount of carbohydrates and 36 mg of aspartame. Concentrations The sweeteners were added at two different concentrations: C1, 2 teaspoons of sugar (6.18 g) or 20 drops of Barny diet (80 mg of cyclamate +20 mg of saccharin) or 1.0 g of NutraSweet (36 mg of aspartame). C2 corresponds to half the dose used for Ci. Concentrations of sweeteners were different due to different sweetening capacities. Infusions The preparation of black tea and yerba mate infusions were performed following the recommendations of the manufacturers. The first was prepared by adding 2g of black tea to 150 ml of boiling distilled water, leaving it to settle for three min. Yerba mate infusion was prepared in a similar fashion, except that 3g of yerba mate was added. Both infusions were filtered after preparation. Subjects and saliva samples A group of 32 people (number was required for the development of the factorial design) were included in this study. Their ages ranged between 18 and 20 years. Their general and buccal health states were considered "very good" by a doctor and a dentist. They were divided randomly into two groups, one which received black tea and one which received yerba mate. Samples of whole saliva for each determination were taken from the sublingual region by aspiration using a sterile plastic syringe. Sampling was carried out in the morning, before and after drinking of the infusion. Measurement of ph Measurements were carried out using a PS-30 Corning ph Meter. Determinations were done immediately after sampling in order to avoid false alkalinization. ph determinations of the infusions with the addition or not of sugar and sweeteners (in vitro measurements), and those of salivary ph were obtained in duplicate. Buffer capacity The buffer capacity was determined by recording the ph of 2 ml of infusion (initial ph, phi) and after the addition of 0.5 ml of 0.1 M HCl or 0.1 M NaOH (final ph, phf). The difference between these determinations (ApH) revealed the buffer power. The smaller the ApH, the grater the buffer capacity of the infusion (5). Experimental design After two h of fasting, 1 ml of whole saliva was obtained from the subjects. Initial ph was measured in each sample. Black tea or yerba mate infusions were prepared, immediately afterwards sugar and the sweeteners were added. After three min each of the subjects drank their respective infusions. Fifteen and 30 min later, saliva samples were taken again and ph was determined. Statistics A complete aleatoric factorial design with four factors at three, two, two and two levels (7) was followed, in order to evaluate the quantitative effects that the variables exerted on ph, individually as well in combination. The factors and levels were: Sweetener (sugar and artificial sweetener, Barny diet and NutraSweet), Infusion (black tea and yerba mate), Concentration (CI and C2), and Time after ingestion (15 and 30 min). In order to carry out the statistical analysis of the data the following items were calculated: 1) effects of the interaction at the same level, 2) main effects of the factors, 3) effects of the interactions between two and three factors, and 4) statistical significance of the effects. Tukey tests were used for post hoc analysis. Results Experimental results In vitro ph determinations of infusions with and without sugar or artificial sweeteners supplemented at two concentrations are listed in Table 1. ph value of black tea was statistically different (p < 0.01) than that of yerba mate. The supplement of artificial sweeteners had no significant effect on the infusion phs, while they were significantly lowered (p <0.0001) when sugar was supplemented. No significant differences were observed when using the two concentrations of sweeteners. The buffer capacity towards acids of yerba mate alone was greater than that of black tea, but the last infusion had greater power when sugar was added. Other sweeteners did not alter the buffer capacity of both infusions. Average salivary ph was determined before the intake of the various infusions (initial ph }SD): x = 7.02 }0.31 (n = 32). Salivary ph values were later obtained at two different times after the intake of the infusions supplemented with two concentrations of sweeteners. They are expressed and ordered in Table 2. Higher mean salivary phs were obtained for yerba mate compared to that for black tea. Statistical significant differences (p < ) were also obtained between when sugar was added compared to when infusions included artificial sweeteners. These results were evidenced by the analysis of the variance of the factorial design (Table 3). It showed that Sweetener and Infusion were statistically significant factors (p < 0.01). Concentration and Time have some influence when combined with the type of infusion, but these trends did not reach significance. There were statistically significant (p < 0.01) main effects of Sugar and the type of Infusion (Table 4). That is, there were significant differences when the sugar condition was compared to when the artificial sweeteners were added, and between yerba mate and black tea. The statistical analysis of the influence of the artificial sweeteners (Table 5) revealed that salivary ph did not vary after the addition of Barny diet or NutraSweet, or between the

3 83 Table 1 ph Values and buffer capacity of infusions (yerba mate and black tea) added or not withsweeteners NutraSweet) at two concentrations (CI and C2) (Sugar, Barny diet or Table 2 Factorial design for the different variables (artificial sweetener, infusion, concentration and time) for both levels Table 3 Analysis of the variance of the factorial design

4 84 Table 4 Main effects of sweetener, infusion, concentration and time Means with same superscript differ significantly (p<0.01) Table 5 Main effects of artificial sweeteners, infusions, concentration and time Means with different superscripts differ significantly (p< 0.05) two test times (15 or 30 min). A trend was apparent for the concentrations of the artificial sweeteners. The secondary effects, that is, the interaction between two and three factors, were not statistically significant (p<0.05) for any of the combinations. Discussion The mouth is the initial part of the digestive tube, so the type of food that is consumed may influence oral tissues. Saccharin, cyclamate and aspartame are examples of artificial non-caloric sweeteners to which non-cariogenic properties are attributed (8-10). It is well known that consumption of tea reduced caries development in humans and animals, an effect now attributed to its fluoride content (11). Tea also contains caffeine, an alkaloid, structurally defined as 1,3,5 trimethyl xanthin, that interferes with dental calcification causing formation of smaller enamel crystals (11). It is also considered that various polyphenols present in tea extracts inhibit growth of Streptococcus mutans. Inhibition of the synthesis of glucans from sucrose by glucosyl transferase of Streptococcus sobrinus has also been demonstrated (6). Polyphenols are also constituents of yerba mate, but their action in the mouth has not been described. In this paper the ph values of the infusion black tea of yerba mate with or without commercial sugar, Barny diet and NutraSweet at two concentrations was determined. Our results showed that the ph of infusions with the artificial sweeteners was close to neutrality, but the addition of sugar lowered the ph. However, tea and yerba mate developed in vitro a buffer capacity towards acids, and a less effective property towards alkaline substances. The addition of sweeteners did not alter significantly the ph of the infusions. The response of saliva towards these beverages was later considered. After their consumption, salivary ph was statistically analysed (7) using a factorial design to assess for significant main effects and interactions, as in previous work (12). Determinations of saliva ph were carried out 15 and 30 min after the ingestion. This in vivo examination revealed that there were significant differences in the saliva ph levels between types of infusions, probably related to their different buffer capacity. Sugar was also a significant factor which had an effect on saliva ph values. However, the phs were close to the initial ph values, and the buffer capacity arrangements of saliva should also be considered. Artificial sweeteners did not significantly influence salivary ph levels. The determination of the buffer capacity of beverages is considered necessary by Lussi et al (3) for the prediction of its erosive potential action on surface softening of enamel. Other properties are the baseline ph and their phosphate and fluoride composition, ions that bind calcium. Calcium may provide protection to the enamel before the occurrence of undersaturation (13). That is, in vivo other factors are involved. The action of saliva, its flow rate, its influence on the formation of the pellicle (3), and the effect of the oral flora on dental plaque are also factors that have an important influence. On the other hand, Gardiner et al (14) noted that many food parameters need to be assessed, since they did not find a linear relationship between sucrose concentration in a food and its acidogenic potential. In this last sense, the effect of yerba mate on plaque ph should be considered in further studies. Acknowledgments This investigation was supported in part by a grant from CIUNT (Consejo de Investigaciones de la Universidad Nacional de Tucuman). References 1. Hall, H.D. (1993) Protective and maintenance functions of human saliva. Quintessence Int. 24, Jenkins, G. N.(1983) Fisiologia y bioquimica bucal. 4th ed., Editorial Limusa, S. A. Mexico, (in Spanish) 3. Lussi, A., Jaeggi, T. and Jaeggi-Scharer, S. (1995) Prediction of the erosive potential of some beverages. Caries Res. 29, Birkhed, D. (1989) Sugar substitutes-one consequence of the Vipeholm study? Scand. J. Dent. Res. 97, Lissera, R. G., Luna Maldonado, E. R. and Battellino, L.J. (1998) In vitro erosive capacity of some fruit juices and soft or low alcoholic strength beverages on human teeth. Acta Odont. Latinoamer. 11, Ooshima, T., Minami, T., Aono, W., Izumitani, A., Sobue, S., Fujiwara, T. Kawabata, S. and Hamada, S. (1993) Oolong tea polyphenols inhibit experimental dental caries in SPF rats infected with mutans streptococci. Caries Res. 27,

5 85 7. Box, G.E., Hunter, W.G., Hunter, J.S.(1988) Estadistica para investigadores. Editorial Reverte, Barcelona, (in Spanish) 8. Grenby, T.H. (1991) Advances in non-caloric sweeteners with dental health advantages over sugars. Proc. Finn. Dent. Soc. 87, Imfeld, T. (1993) Efficacy of sweeteners and sugar substitutes in caries prevention. Caries Res. 27, Suppl. 1, Ziesenitz, S.C. and Siebert, G. (1988) Uptake of saccharin and related intense sweeteners by Streptococcus mutans NCTC Z. Ernahrungsswiss 27, Schneider, P.E., Alonzo, G., Nakamoto, T., Falster, A.U. and Simmons, W.B. (1995) Effects of caffeine intake during gestation and lactation on the acid solubility of enamel in weanling rats. Caries Res. 29, Gancel, F. and Novel, G. (1994) Exopolysaccharide production by Streptococcus salivarius ssp. thermophilus cultures. 1. Conditions of production. J. Dairy Sci. 77, Hay, D.I. (1995) Salivary factors in caries models. Adv. Dent. Res. 9, Gardiner, J.A., Pollard, M.A. and Curzon, M.E.J. (1997) The effect of different concentrations of sugars in two foods (yoghurts and baked beans) on plaque ph. Int. Dent. J., 47,