Most researchers consider acid-containing soft drinks and beverages as primary culprits in the growing incidence of dental erosion.8,9,14,15,20-22 Over the past several decades, serving sizes in the US have increased dramatically.8,23 The average drink size, in the 1950’s, was slightly less than seven (7) fluid (fl.) ounces (207 mL). By the 1960’s, this average serving size had increased to twelve (12) fl. ounces (355 mL), and by the late 1990’s had increased still further to twenty (20) fl. ounces (532 mL) (Figure 7). In many restaurants, the largest sizes that are sold often contain 42-44 fl. ounces (1,242-1,301 mL), and free refills are commonly available. Between 56% and 85% of children at school have been reported to consume at least one (1) soft drink daily, with 20% consuming an average of four (4) or more servings every day.8,24
Beverage sizes have grown significantly. In the 1950’s, the average cola drink in a US restaurant was 7 fl. ounces (207 mL). Serving sizes have increased steadily ever since; today, the average serving size is over 30 fl. ounces (887 mL), with individual “large” portions often providing 42-44 fl. ounces (1,242-1,301 mL), or more, of beverage.
In the US, current caloric intake has been shown to be up to about 4,000 calories per day per person. Approximately 25% of this caloric consumption is in the form of sugar-sweetened beverages or, at the very least, added sugars to the diet. A study by Credit Suisse compared the gross domestic product of various nations versus their annual consumption of sugar-sweetened beverages.25 As shown in Figure 8, the US is well above other countries in this assessment, which indicates a very high risk for dental erosion in this country, due to the low pH and high acid levels in sugar-sweetened beverages. In the US, the average person consumes over 40 gallons (151 L) of sugar-sweetened beverages per year.25,26 It is no surprise that the US has obesity problems, caries problems, and other related side effects.
Annual global consumption of sodas vs. GDP per capita clearly demonstrate a much higher level of consumption in the US compared to other nations.
The severity of erosive acid attacks depends on multiple factors, such as the pH (Table 2), the titratable acidity and the buffering capacity of both the beverage, or food, and the saliva of the individual ingesting the beverage. Another primary factor is the contact time of the acid on the teeth. The longer the teeth are subject to an erosive acid challenge, the more likely they will be to undergo erosive changes.
In addition, all acids are not alike with regard to their erosive potential. Studies have shown that citric and lactic acids have a higher erosive potential than acetic, maleic, phosphoric and tartaric acids, although all of these dietary acids have some degree of erosive potential. When included in products containing other ingredients, such as calcium, phosphate and/or fluoride, the erosive potential of an acid can be significantly decreased. For example, acidic beverages, when supplemented with calcium, phosphate and fluoride, have been shown to have a reduced erosive potential compared to controls.27 In addition, yogurt, which has a relatively low pH, has little erosive potential due to its high calcium and phosphate content.28
Consumption of a single acidic beverage and drinking it normally has little impact on dental erosion. Although the pH of saliva does drop while drinking it, the saliva will generally provide sufficient buffering to quickly re-establish a neutral pH. If people swish their drinks, or if they sip these beverages over long periods of time, there is a much higher likelihood of having problems. One way to help minimize the potential for prolonged contact of acidic beverages with the teeth is to drink through a straw, as this may help to minimize contact with the teeth.29
Table 2. pH values of common beverages.
|Coffee and milk||5.3|
|Orange Juice (Minute Maid)||2.64|
|Reference: Battery Acid||1.0|
While there is growing awareness of dietary issues related to the high consumption of soft drinks, particularly among school aged children, the issue of dental erosion is not limited to consumption of only these beverages. Equally challenging to the enamel surface is excess exposure to fruits, acid containing vegetables, fruit juices, wine, and other dietary foods and beverages that are otherwise considered healthy alternatives to soft drinks. It is difficult to protect against an increasing erosive challenge, no matter what kind of diet is consumed.28,29,31-33
One of the driving factors for dental erosion is the duration of contact between dietary acids and the teeth. As a result, there is some perception that high viscosity drinks may be more erosive than those with lower viscosity, due to their tendency to be retained in the mouth for longer periods of time. Recent in vitro studies, however, have suggested that the opposite might be true,34,35 possibly a result of the ingredients that enhance viscosity actually being able to slow the release of acids from the beverage, thus causing less damage. This area of research will be interesting to watch, as it will take more robust models and clinical trials to confirm whether increased viscosity enhances erosion, or helps to prevent it.