Tooth erosion and consumption of acidic beverages

Tooth erosion, also termed erosive tooth wear, is defined as a chemical-mechanical process resulting in a cumulative loss of hard dental tissue, characterized by the loss of natural tooth contour and morphology.  The cause of tooth erosion is a multifactorial. Pathology in which dietary intake, saliva, dental hygiene and general health all play mitigating, yet different, roles.  Epidemiologic studies have shown that the intake of acidic beverages, such as carbonated drinks, fruit juices, and sports drinks, is an important factor associated with tooth erosion.  In children and adolescents the dominant causative factor for tooth erosion is consumption of soft drinks, with the global prevalence of root erosion  in children (about 5 years of age) to be 30%.

Reddy et al. (2016, J. Amer. Dent. Assoc., 147:255-263) determined the erosive potential of about 380 beverages, assessed their pH, and categorized the beverages according to their corrosive nature to teeth.  Table 1 lists a few of the beverages categorized as “extremely erosive”. It is interesting to note that many of these beverages may be considered nutritious for children (e.g., Welch’s Ruby Red Grapefruit Juice, pH 2.97) or, at least, innocuous (e.g., Minute Maid Lemonade, pH 2.57; Arizona ). Iced Tea, pH 2.85).

Beverage pH Beverage pH
Fruit Juices Sodas
Ocean Spray Cranberry 2.56 RC Cola 2.32
Minute Maid Cranberry Grape 2.71 Coca-Cola Caffeine Free 2.34
V8 Splash Berry Blend 2.94 Pepsi Cola 2.39
Fruit drinks Energy drinks
Welch’s Blueberry Kiwi Blast 2.57 Jolt Power Cola 2.47
Tropicana Twister Blue Raspberry Rush 2.62 24:7 Energy Cherry Berry 2.61
Snapple Mango Madness 2.89 Rockstar Energy Drink 2.74

 

To understand the interplay between tooth erosion and intake of acidic beverages, attention is directed to the chemistry of tooth erosion.  Dental enamel, the hardest substance in the human body, is composed of calcium (Ca2+), phosphate (PO43-), hydroxide (OH-), and, to a lesser extent, fluoride (F-) ions.  There is a continuous exchange of these ions between tooth enamel and saliva in the oral cavity.  When the enamel is bathed in saliva with low concentrations of these ions, the ions diffuse from the enamel into the aqueous oral cavity (leading to tooth demineralization); conversely, when saliva contains high concentrations of these ions, the ions diffuse from the salvia into the enamel (leading to tooth remineralization). As calcium seems to be the key ion in tooth demineralization and remineralization processes, the calcium concentration of an acidic beverage is a key factor in effecting enamel hardness.  Low pH exacerbates the release of calcium from enamel. Ingestion of acidic beverages with a low level of calcium result in calcium leaving the tooth enamel, thus promoting demineralization, softening the enamel and  leading to tooth erosion. Further acid-induced demineralization of the outer enamel may extend into the underlying dentin, causing painful hypersensitivities and esthetic and functional limitations. 

Many acidic beverages contain at least one of the following acids: carbonic acid, phosphoric acid, malic acid, and citric acid. For example, Gatorade (pH 2.89) contains citric acid, Coca-Cola (pH 2.55) contains phosphoric acid and carbonic acid), and Sprite (pH 2.57) contains carbonic acid and citric acid). Owing to the low pH values of these beverages, these acids weaken the link between calcium and the phosphate mineral composition of the enamel and dentin, leading to mineral loss and tooth softening.

The method of drinking acidic beverages greatly influences the pH on the surface of the teeth and consequently mediates the risk of tooth erosion.  Studies of different drinking habits showed that, in general, the more prolonged time an acidic beverage is maintained in the mouth, the greater the risk for tooth erosion.  The most deleterious modes of acidic beverage intake, leading to a prolonged drop of pH in the oral cavity, were holding the drink in the mouth for 2 min before swallowing , long-sipping from a glass (15 min duration), and short-sipping from a glass (2 min duration). Gulping (swallowing quickly, 3X in 5 min intervals) resulted in only a small decrease in pH and was considered harmless. Drinking from a straw positioned towards the upper palate did not affect tooth surface pH. But if acidic beverages were habitually consumed through a straw or ‘pull-out’ drinking cap positioned in front of the teeth, then the incisors were eroded quickly.

The primary teeth of children are highly susceptible to erosion and acidic beverages should not be placed in a baby bottle, especially before bed-time, when the mouth is relatively dry. Dry mouth conditions from the lack of saliva exacerbate tooth erosion, as saliva dilutes the acidic beverage and buffers the pH of the oral cavity. The risk for developing significant erosive lesions was evident in infants given fruit drinks (e.g., apple juice) in a feeding bottle at bed-time.

It was suggested that pediatric patients who exhibit tooth erosion should be encouraged to sometimes substitute ingestion of milk or yogurt rather than consumption of an acidic beverage. It was shown that the greater the intake of milk or milk products (e.g., yogurt), the lower the prevalence of tooth erosion. The protective effect of milk is most likely due to its high amounts of calcium, phosphate, and casein (a protein).  Calcium and phosphate protect the dental surface against demineralization and casein, as well as milk lipids, adhere to the tooth surface, working as a protective barrier against acids.  Yogurt is also a protector against acid-induced tooth erosion as it contains high concentrations of calcium and phosphate and is non-corrosive, despite its low pH (≈4.0).

Too much milk, bathing the teeth, particularly at night, may, however, result in a different type of enamel  deterioration leading to “baby bottle cavities.”

When tooth erosion is noted, additional tips to reduce the deleterious effects of intake of acidic beverages include to restrict the consumption of acidic beverages to the main meals, to rapidly consume acidic beverages rather than to swirl them in the mouth, to add calcium effervescent tablets to suitable acidic beverages (e.g., to orange juice), to drink calcium-enriched sports drinks, and to reduce the frequency of consumption of acidic beverages. 

Tooth erosion may be exacerbated by acidic gastric fluid entering the oral cavity, as in individuals with gastrointestinal reflux disease as in bulimia.  A dry mouth is conducive to tooth erosion.

Saliva is the most important defense mechanism against dental erosion. Saliva dilutes acidic substances, buffers the pH of the oral cavity, forms a pellicle on tooth surfaces to protect against acid stress, and increases the rate of remineralization of eroded dental enamel by restoring calcium, phosphate, and fluoride. Reduced salivary flow rate, such as that due to high levels of exercise which dehydrates the body because of intense sweating, can be a risk factor tooth erosion.  Athletes should rehydrate with water, rather than with sport drinks (pH 2.8 to 3.2).

Parents should encourage their children to hydrate with neutral pH fluids, particularly water. Being aware of the potential complication of tooth erosion by ingesting low pH (acidic) sports drinks and sodas will go a long way towards a healthier smile.