Relieving Dry Mouth: Varying Levels of pH Found in Bottled Water
Bailey Jean Fisher; Angela Spencer, PhD; Van Haywood, DMD; and Gayathri Konchady, DMD
It is estimated that 30% of people older than 60 years suffer from hyposalivation or dry mouth. Drinking water frequently has been recommended as a safe, non-pharmacologic way to combat hyposalivation. The saliva in patients with dry mouth is acidic. Beverages consumed daily may have an erosive potential on teeth. The pH and the mineral content of the beverage determine its erosive potential. An acidic beverage, therefore, may have harmful effects on mineralized tooth structures, causing erosion of enamel, dentin, and cementum. Because bottled water is both convenient and easily available, the authors tested the pH of eight common brands of bottled water. (One brand included two different bottle types, for a total of nine bottled waters tested.) To standardize the pH electrode, pH buffers of 4.7 and 10 were used. The pH was measured using the Denver Instruments basic pH meter. Six recordings were used for each brand and then averaged to report the pH. Two of the bottled water samples tested were below the critical level of 5.2 pH to 5.5 pH, the level at which erosion of enamel occurs. Six of the samples tested were below the critical pH of 6.8, at which erosion of root dentin occurs. The authors conclude that both patients and clinicians incorrectly presume bottled water to be innocuous. Clinicians should be cognizant of the erosive potential of different brands of bottled water to both educate patients and recommend water with neutral or alkaline pH for patients with symptoms of dry mouth to prevent further deterioration and demineralization of tooth structure.
The pH level of a liquid or saliva is measured on a scale of 0 to 14. In healthy individuals the pH of saliva ranges from 6.8 to 7.2. At 25°C, a pH level of less than 7 is considered acidic, greater than 7 is considered basic, and a pH equal to 7 is neutral.1 Erosion of enamel occurs when the pH of the oral cavity is less than 5.5, and there is 10-fold increase in enamel solubility resulting in a 100-fold increase in enamel demineralization with each unit drop in pH.2 Lowered pH levels resulting from bacterial acid production caused by the breakdown of fermentable carbohydrates leads to the site-specific demineralization of enamel, ie, caries.3,4 Erosion is the demineralization of the tooth structure due to a drop in pH5 caused by either an extrinsic (eg, diet)6 or an intrinsic (eg, gastroesophageal reflux) source.7
Demineralization or erosion is affected by saliva.8 The buffers in saliva are mostly bicarbonate and phosphate that neutralize the acid produced by plaque bacteria and maintain homeostasis.9 Research has identified bacteria that produce alkali from arginine and increase the pH of saliva, thereby preventing demineralization.10,11 Patients with dry mouth experience increased caries in the cervical, incisal, and marginal areas of teeth, but the caries is often more severe than the amount of plaque and carbohydrate intake. Frequent consumption of acidic beverages has an additive effect on the demineralization of enamel and dentin in patients with dry mouth whose saliva has a low pH level.12 Compared to enamel, root surface is more susceptible to erosion because of the lower mineral content and higher organic content of cementum and dentin.13 The critical pH that is correlated to erosion of enamel is 5.2 to 5.5 and that of root dentin is 6.7.14,15 There is less likelihood of demineralization when the pH is basic or neutral.
Frequent consumption of water is a common non-pharmacologic approach used to combat dry mouth. Because patients with dry mouth are not dehydrated, it is recommended they take frequent small sips of water. Consequently, the water used for relief of dry mouth, otherwise known as hyposalivation or xerostomia, should have a pH level that is neutral or basic. The pH and mineral content of the beverage is the determining factor of the erosive potential of any beverage; consequently, knowledge of the pH of a beverage is needed to develop a preventive strategy for patients with dry mouth.
Because pH levels of bottled water are typically not provided by the manufacturers and distributors, the authors tested the pH of commonly available brands in their local area.
All bottled water used for analysis was purchased in either Augusta, GA, or Atlanta, GA. Bottled water samples were purchased at Walmart, Rite Aid, Kroger, and Bi-Lo stores. Six bottles of each of the following brands were purchased: Alkalife Ten Spring Water; Dasani®; Deer Park® 100% Natural Spring Water; Great Value Purified Drinking Water; Kroger Purified Drinking Water; Rite Aid Pantry Crystal Lake Spring Water, screw cap; Rite Aid Pantry Crystal Lake Spring Water, squirt bottle; Sam’s Choice Purified Drinking Water; and Southern Home Spring Water. The pH electrode (Accumet™, Fisher Scientific, fishersci.com) was standardized using pH buffers of 4, 7, and 10. The meter used was Denver Basic pH Meter16 (Denver Instrument Co., denverinstrument.com) as shown in Figure 1.
Each brand of bottled water was measured with an average of six recordings of pH. The glassware and the pH electrode were rinsed three times in between measurements with the water of the bottle being measured. The pH electrode sat for 2 minutes in the sample before recording the pH level. Because the pH can be affected by the amount of carbon dioxide (CO2) present in the atmosphere, it is imperative to have consistency in the exposure of the sample to the atmosphere while measuring. Therefore, a consistent 2-minute time period was used for each sample between initial measuring and recording the pH level.
After analysis with a pH electrode, the six recordings of the pH level of each brand of bottled water were averaged; the results are listed in Table 1. Two of the bottled water samples tested were below the critical pH level of 5.2 to 5.5, at which erosion of enamel takes place, and six of the samples tested were below the critical pH level of 6.7, at which erosion of root dentin occurs.
The terms dry mouth, xerostomia, and hyposalivation are used interchangeably by clinicians. An estimated 30% of people older than 60 years suffer from dry mouth.17 Hyposalivation, either from decreased salivary flow or insufficient production of saliva, is the cause of dry mouth.18 Xerostomia is the subjective perception of dryness experienced by the patient.19 The prevalence of xerostomia is significantly greater in people who have the autoimmune disease Sjögren’s syndrome, and is very severe in patients who have received head and neck radiation treatment.20
The most common causes of dry mouth are consumption of xerogenic drugs, aging, autoimmune diseases, such as Sjögren’s syndrome, and a history of radiation treatment to the head and neck region.21 The most severe dryness occurs in post-radiation therapy patients.22
The most common symptoms of dry mouth are soreness, burning sensation, sticky mucosa, difficulty swallowing and speaking, change in taste, halitosis, and inability to wear dentures.17 Patients with dry mouth experience increased caries in the cervical, incisal, and marginal areas of their teeth that is often more than would be expected by the amount of plaque and carbohydrate intake.18 Other symptoms of dry mouth include erythematous candidiasis, loss of papillae on the tongue, and cracked, peeling lips.23 With newer cancer treatments increasing patient survival rate and longevity, clinicians need to focus on improving the patient’s quality of life after cancer treatment. Postradiation saliva flow rate is reduced to < 10% of the initial rate.24 Radiation causes loss of function in the salivary glands and a decrease in amylase activity and, thereby, a more acidic pH of the saliva.25
It is vitally important to educate patients with dry mouth to use fluoride to resist teeth erosion. They should also be exhorted to avoid consuming beverages with acidic pH and to obtain symptomatic relief by chewing xylitol gum and using pharmacologic salivary stimulants,26 as well as acupuncture.27 While this project used a small sample size when testing local bottled water, there are numerous articles citing the relationship of pH of beverages to caries and urging caution about consumption.2,5,28,29 According to the International Bottled Water Association (IBWA), Americans consumed 11.7 billion gallons of bottled water in 2015, an increase of 7.9% compared with 2014.30 Sales of bottled water have steadily risen in recent years while sales of calorie- and carbohydrate-rich soda and juices have declined.31 The increasing demand for bottled water is thought to be due to consumers becoming more health conscious and making better choices regarding diet, opting for a zero-calorie, convenient beverage option.30
Alkalife reported the pH levels of various brands of bottled water32: Dasani has a pH of 5.6, Deer Park a pH of 7.8, and Alkalife Ten has a pH of 10. In the present study, the pH levels of Dasani and Deer Park bottled waters were tested to confirm the accuracy of the data presented by Alkalife and for comparative purposes. The Environmental Protection Agency has defined the pH guidelines for surface water to be in the range of 6.5 to 9.33 The range of pH could be the result of CO2 dissolving in the water leading to a decrease in pH.34 The pH of a solution is measured by the number of hydrogen ions (H+) present1: pH = – log [H+].
The mineral content of water depends on the source of the water and also determines the pH. If bottled water is either not purified or purified via reverse osmosis, the pH of the water is dependent upon the source. Natural spring water is underground water originating from rain and snow precipitation that is filtered naturally by gravel and sand as it percolates downward toward the impermeable layer of clay and rocks in the earth. Spring water is naturally alkaline or acidic depending on the mineral content at the site. Natural spring water is usually filtered to remove chlorine and disinfected using ultraviolet light before being bottled for consumption. The mineral content in spring water is not altered through the process.35
The source of water could impact pH if minimal processing or purification methods were performed on the water. Purification methods eliminate the importance of source location. Purified water may be spring or tap water that has been subjected to reverse osmosis, distillation, or deionization to remove all impurities.36 The purification method serves to standardize the pH of all bottled water of that particular brand. Ultra-purification removes the vital mineral content, especially calcium and phosphate, needed for homeostasis of calcified tooth structure. Although this may be appealing to some consumers who think the water is more purified and thus safer, ultra-purification reduces the pH of the water and may be detrimental to patients with hyposalivation. The addition of taste enhancers also can affect pH. Companies alter the taste of water with additives, such as potassium chloride, salt, phosphoric acid, citric acid, and maleic acid. These reduce the pH of the water, making it more acidic.1
Bottled water does not always have a neutral pH. Though slightly acidic bottled water may not be harmful in healthy individuals whose salivary buffers will neutralize acidity, clinicians must be aware of the pH level and the erosive potential of bottled water to make safe recommendations for patients who have dry mouth. Clinicians should inform patients of the potential erosive effect of acidic pH water and make recommendations for drinking neutral or alkaline water.
This work was funded by the Department of Chemistry and Physics, the Center for Undergraduate Research and Scholarship, and the Pamplin Student Research Fund at Augusta University, Augusta, Georgia.
It is with much sadness the authors report the sudden accidental death of Dr. Konchady during this project. She was an important part of the faculty at Augusta University, and her smile and warm nature will be missed.
About the Authors
Bailey Jean Fisher
Dental College of Georgia at Augusta University
Angela Spencer, PhD
Assistant Professor of Chemistry
Department of Chemistry and Physics at Augusta University
Van Haywood, DMD
Department of Restorative Sciences
Dental College of Georgia at Augusta University
Gayathri Konchady, DMD
Department of Restorative Sciences
Dental College of Georgia at Augusta University
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