Laboratory Studies on the Dental Effects of Soft Drinks and Other Beverages

• Sarah Story• Undergraduate in Pre-Dentistry• Biology Department• Tennessee Technological University• Cookeville, TN 38505• Date: April 26, 2006

Introduction: The consumption of soft drinks has increased dramatically over past decades; the

soft drink industry is reported to produce 10 billion 192-ounce cases per year. Over a 50-year period, annual soft drink production appears to have increased five fold, from 100 12-ounce cans per person in 1947 to nearly 600 12-ounce cans per person in 1997. Looking at it another way, the average person in 1947 consumed approximately two cans of soft drinks per week, while the average person in 1997 consumed approximately 12 cans of soft drinks per week, or nearly two cans per day (von Fraunhofer & Rogers 2004).

Dental erosion is a non-carious, pathological loss of tooth surface, distinct from abrasion and attrition, and is defined as the irreversible loss of dental hard tissue by a chemical dissolution by acids other than those produced by bacteria. Over the last two decades, tooth erosion has become a significant clinical problem (Sirimaharaji & others 2002). Nutrition plays a key role in erosion. Any product with a low pH value has the potential to cause structural damage when ingested (Shipley & others 2005). Erosion can occur from frequently consumed soft drinks, fruit juices, and sports/energy drinks.

Introduction continued… The erosive potential of beverages is thought to involve several factors, including low

pH and the buffering capacity of the drink. Soft drinks may contain several different types of acid that contribute to the low pH value. Carbonated beverages will contain carbonic acid formed by carbon dioxide in solution. Even when the carbon dioxide has been released and the drinks become “flat” the pH remains low (acidic). This indicates that soft drinks have inherent acidity due to other acids that are added to stimulate taste and counteract sweetness. These other acids include, for example, phosphoric acid and citric acids present in cola-type drinks (Edwards & others 1999). Fruit juices and fruit-flavored drinks are made from a concentrated source of fruit and consist of organic acids derived from the fruit such as citric acid from oranges, tartaric acid from grapes and malic acid from apples. Added vitamin C (ascorbic acid) may also contribute to the acidity of soft drinks. Typically, soft drinks consumed at meal times are less injurious than those consumed alone and continuous sipping is considered more harmful to dentition than consuming an entire beverage at once. However, it has been reported that certain soft drinks (notably cola beverages) are retained on the dental enamel and are less likely than other beverages to be removed by saliva, resulting in an increased cariogenicity.

Introduction continued… Why does a tooth dissolve in acid? The underlying acidity of beverages is believed to be the primary

factor in the development of dental erosion; this total acid level (known as titratable acid), rather than pH, is thought to be an important factor in erosion because it determines the actual hydrogen ion availability for interaction with the tooth surface. The measurement of a beverage’s total acid content may be a more realistic and more accurate method for predicting erosive potential. Other important factors concerning the erosive quality of beverages include the type of acid and its calcium chelating properties, exposure time, and temperature (Fraunhofer & Rogers 2004). Dental enamel is composed primarily of hydroxyapatite (HA), Ca₁₀(PO₄)₆(OH)₂, but it also contains several impurities such as carbonate and fluoride. Because the proportions of these impurities vary from person to person, and indeed from tooth to tooth, and because the impurities can influence enamel solubility, that solubility is not fixed and varies slightly from person to person (Dawes 2003).

There is no question that erosion causes significant damage to dental enamel, particularly among young people. Although altering drinking habits may prevent erosion by reducing the intake of acidic beverages, such an adjustment cannot always be achieved. However, recent work suggests that modifying beverages (for example, by the addition of citrate ions) alters the acidogenic potential, effectively reducing erosion (Fraunhofer & Rogers 2004).

Objective and Hypothesis

Objective: The objective of my study is to determine which beverage has the most erosive

effect on dental enamel.

Hypothesis: In meeting my objective, I will test my hypothesis that non-cola and energy

drinks will have the most erosive effect on dental enamel.

Null Hypothesis: In meeting my objective, I will test the hypothesis that the erosion on

the enamel will be the same for all beverages tested.

The drinks that were used:

Methods and Materials

The test teeth are sound (caries free) human

molars and premolars that had been extracted for

orthodontic or periodontal reasons. After

sterilization in an autoclave each specimen will be

dried and weighed to 0.01 mg. All studies will be

preformed at room temperature.

The test beverages and test specimens will be

placed in plastic containers with 5 mL of the test

beverage. The specimens will be allowed to soak

in the test beverage for 60 minutes each and then

allowed to dry until for 24 hours and then weighed.

This process will be preformed over 24 hour

intervals for a 7 day (168 hour) period. The

beverages for each specimen will be replaced daily

with fresh solution after each weighing. Mean

percentage weight losses and weight losses per

unit area will be calculated for each set if enamel

specimens (von Fraunhofer & Rogers 2004).

Actual Experiment Pictures

Results The amounts of enamel dissolution that occurred in the 20 specimens over the 7 day period are

summarized in the table and figure 1. The control, tap water, showed no enamel dissolution. All other

media exhibited a progressive attack on the dental enamel, with a linear or straight line relationship

between the enamel dissolution and exposure time over the test period. Typical dissolution curves are

shown in Figure 1.

The beverage Red Bull showed the greatest affect on the dental enamel followed my Minute Maid

Lemonade. Results from Fruit Punch Gatorade were within .002 grams of Minute Maid Lemonade,

and showed the third greatest enamel dissolution from the tested beverages. The results from Mountain

Dew were within .01-.02 grams of the Red Bull and Minute Maid Lemonade, and resulted in being the

beverage with the least enamel dissolution before the control. The Figures 2 and 3 shows an example of

enamel dissolution in a teenage boy who managed to do decade’s worth of damage to his enamel in just

a few years. Effects such as those in figures 2 and 3 could be expected with continued exposure.

Tables, Figures and Graphs

Fig. 2 and 3. Left- Molar with acid erosion. This teen-ager has the enamel of a 65-year old. Right-Normal molar

Fig. 1. Enamel dissolution in various beverages.

Beverage Container pH Sugar per 12 oz.

7 Day Average Weight

Lost

Mountain Dew Bottle 3.14 46 grams .023 g

Red Bull Can 3.32 27 grams .043 g

Minute Maid Lemonade

Bottle 2.80 40 grams .033 g

Fruit Punch Gatorade

Bottle 2.95 28 grams .035 g

Control(tap water)

Bottle 7.0 0 grams 0 g

Table. Beverages utilized in this study.

Discussion This study exposed caries- free dental enamel to a variety of popular beverages continuously over a

period of 7 days (168 hours). Some criticisms that can be made about this experiment are: the small

sample size of beverages used and the short exposure time (von Fraunhofer & Rogers 2004). The

beverages that were selected were selected because of there potential to have an erosive effect on the

dental enamel based on the results from other researched studies. A larger sample size is usually

preferable when conducting an experiment (von Fraunhofer & Rogers 2004). However, this study was

intended to identify which beverages held the most erosive effect on the enamel.

Regarding the length of the test period, it has to be recognized that realistic testing of enamel

dissolution in soft drinks and other beverages is demanding because it is difficult to determine the

extent of oral exposure for any given individual. Many different factors affect any individual person

which can make them more or less susceptible to enamel dissolution. However, it is possible to make

certain projections through careful experiments. Based on an average daily consumption pf 25 ounces

of soft drink and a residence time in the couth of five seconds, the total exposure time to beverages

would equal 22, 750 seconds (380 minutes or 6.3 hours) per year. However, it is more likely that the

exposure time for a beverage on the dentition is closer to 20 seconds before salivary clearance occurs

which would make the annual exposure time of dental enamel to beverages approximately 90,000

seconds (1,500 minutes or 25 hours).

Discussion Continued…

Despite limitations, certain conclusions can be drawn from this study. First, exposure to

beverages with the presence of simple carbohydrates (sugars found in these beverages)

or artificial sweeteners show noticeable amounts of enamel dissolution. A more

interesting observation was the decreased amount of enamel dissolution in the cola-

based drink when compared to the non-cola drinks. These differences could not be

credited to the beverages pH since there has been no known correlation between pH

and enamel dissolution (Gtenby & others 1989). The pH range for most beverages is

2.0-3.4, which is well below the marked pH for dental caries (5.5). The range suggests

that enhanced enamel dissolution results from effects other than beverage pH, most

likely the additives within non-cola beverages that are added for desired results. As

indicated earlier, acids found in these beverages can alter the effects of dental erosion

because of their ability to lower the pH needed to maintain caries free teeth (Rugg-Gunn

and Nunn 1999). As a result, they can be very aggressive towards dental enamel

(Davani and others 2003).

Conclusions The data reported here indicates that

certain beverages may cause significant

enamel dissolution with repeated exposure.

The non-cola drinks showed the greatest

dissolution of the dental enamel. The data

suggests that enamel aggressively is

determined by beverage composition (such

as additives) rather than beverage pH.

Mountain Dew was found to be the safest

drinks tested followed by Minute Maid

Lemonade, Fruit Punch Gatorade, and lastly

Red Bull. It would seem that reducing

beverage intake and residence time in the

mouth by salivary clearance or rinsing

would be beneficial.

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