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Dry mouth is a common oral complaint with widespread clinical and quality of life implications.1-9 There are a variety of salivary and non-salivary causes for symptoms of oral dryness;1 therefore, it is important for oral healthcare professionals to determine the cause of the symptoms. In addition, it is important to recognize that the management of salivary hypofunction and dry mouth is multidisciplinary and multimodal.2
Saliva is very protective of the oral cavity and also helps with nourishment and proper speech. Protective functions include lubrication, antimicrobial activity, mucosal integrity, lavage, cleansing, buffering, and remineralization. In addition, saliva aids in food preparation, digestion, and taste. Finally, without adequate moisture, oral dryness makes proper phonetics difficult, subsequently affecting speech (Table 1).
Saliva is produced by the parotid, submandibular, and sublingual glands, which collectively account for 90% of saliva production. The remaining 10% is produced by the minor salivary glands, which are found in the submucosa throughout the oral cavity. Estimated daily salivary output is approximately one liter per day, with diurnal variations of up to 50%.2
Saliva is classified as serous and mucous, based on its differing composition and the type of cells producing it. Parotid glands are mainly of the serous type, and the sublingual glands are predominantly mucous cells. The submandibular glands contain a mixture of both, whereas the minor salivary glands are almost entirely mucous. Mucous saliva is more viscous saliva that is rich in protein. Serous saliva, however, is watery and essentially devoid of protein.2
By definition, salivary dysfunction is any alteration in the qualitative or quantitative output of saliva and includes both hyper- and hypofunction. Hyposalivation is considered a measureable decrease in the function of one or more salivary glands as measured by flow rate.2-4,7,8
Xerostomia, on the other hand, is defined as a patient's subjective feeling of oral dryness, which may or may not be a result of decreased salivary flow.2-4,7 It is important to recognize that xerostomia is not a diagnosis but a symptom with multiple possible causes. It is believed to affect up to 40% of Americans and more than 70% of individuals over the age of 65.1-9 It is generally more prevalent in women. It is hypothesized that xerostomia is experienced by patients when salivary secretion drops to 40% to 50% of normal volume.2,4,7
Hyposalivation and/or altered salivary composition comprise the salivary causes of xerostomia complaints and include diseases such as Sjögren's syndrome, autoimmune disorders, diabetes, HIV infection, sarcoidosis, herpes virus, hepatitis C virus, and end-stage renal disease.1-9 In addition, hyposalivation can be a side effect of various treatments such as medications, radiation therapy and I-131 radiation therapy for thyroid disease.9-18 Finally, salivary gland traumas and tumors along with nutritional deficiencies, including eating disorders, can all lead to salivary causes of oral dryness.1
Clinically, a patient with a dry mouth will have dry lips and irritation at the corners of their mouth, or angular cheilitis.2,4,7 Their buccal mucosa will be dry, often sticking to a mirror or any type of retraction device. There will be little pooled saliva in the vestibules and what is there will be thick and frothy. Similarly, it will be difficult to milk saliva from the salivary glands. The patient's tongue will be dry, cracked, and have little papillation. Finally, it is common to see plaque accumulation, cervical caries, and many previously restored teeth (Figure 1).
Medication-induced xerostomia is a common and significant side effect of many medications including over 500 listed in the Physician's Drug Reference.2,4,7 This risk of developing dry mouth increases with the number of drugs taken. Because of this known synergistic effect of medications, older people are more likely to be affected. There is often a close temporal relationship between the drug initiation and the complaints of oral dryness. These symptoms may resolve with drug withdrawal. Common medications known to cause oral dryness are summarized in Table 2.
Sjögren's syndrome is a chronic, autoimmune, inflammatory disorder characterized by dry eyes and a dry oral cavity.10-12 It can occur alone (primary Sjögren's syndrome), or in conjunction with other autoimmune rheumatologic diseases (secondary Sjögren's syndrome), such as rheumatoid arthritis and systemic lupus erythematosus.11 The estimated prevalence of Sjögren's syndrome in the United States is 0.6%, with the highest prevalence occurring in the fourth to fifth decade of life. Nearly 90% of those affected with Sjögren's syndrome are women.10-12
Radiation therapy combined with surgery is the main treatment for head-and-neck cancers. Depending on the site and extension of primary tumors and the path of lymphatic spread, all or part of the major and minor salivary glands are often included within the radiation fields. Salivary gland exposure to radiation results in severe hypofunction and changes in salivary composition and quality.13-16 This damage occurs primarily to serous cells which are responsible for producing watery saliva. The severity of salivary gland damage is dependent on the volume of glandular tissue in the radiation field and the radiation dose. An 80% reduction in both parotid and submandibular and sublingual flow rates occurs after the first 2 weeks of radiation therapy.16 Xerostomia and salivary gland hypofunction often persist for the remainder of the patient's life.16
Salivary glands are known to undergo significant changes with age, with secretory components being replaced by fibrous and fatty tissue. These age-related changes are most evident in the submandibular glands and less so in the minor and parotid glands.17 Age-related changes in salivary composition, specifically electrolytes, have been found to include decreased sodium and increased potassium concentrations. It is most likely that such changes are due to the additive affects of medications for the medical illness for which they are being used.
Diagnosis and Management
Identifying patients at risk of developing salivary gland hypofunction is vital for the oral healthcare professional. A comprehensive medical history including the assessment of systemic and local disease, history of trauma, and a complete medication list is a vital first step in this process. There are five simple, symptom-related questions that are predictive of hyposalivation and can aid in identifying at risk patients (Table 3).2,4 In addition, a thorough physical examination is needed, which includes extraoral and intraoral assessment and possibly the measurement of salivary flow rates or serologic tests when necessary. Occasionally, imaging such as specialized salivary studies, MRI, or CT, is needed. Salivary gland biopsies including minor gland biopsies, fine needle aspiration, and major gland biopsies may also be indicated in certain patients.
After establishing a diagnosis of xerostomia or salivary gland hypofunction and the underlying etiology, a stepwise management approach should be implemented. There are five goals of management including: alleviating symptoms, instituting preventive measures, treating existing oral conditions, improving salivary function (if possible), and managing underlying systemic conditions.2,4,7 Management of symptoms includes diet and habit modifications such as frequently sipping water; sucking on ice chips; avoiding dry, hard, sticky, and acidic foods; and limiting caffeine and alcohol. Attempts to increase salivary flow can also be achieved with sugar-free xylitol-containing mints, candies, and gum. In addition, the use of salivary substitutes and lubricants in the form of artificial saliva, rinses, gels, sprays, and toothpastes is helpful. A bedside humidifier during sleeping hours is usually beneficial for those that have significant nighttime dryness (see Table 4 for summary).
Saliva substitutes have moistening and lubricating properties with the purpose of providing prolonged wetness of the oral mucosa. They come in a variety of forms, such as gels, liquids, and sprays. These saliva substitutes may have mild subjective effects. Stimulants such as sugar-free chewing gum or sugar-free hard candy seem to provide more relief than any saliva substitute. Gum containing xylitol not only stimulates the glands, but also can help prevent caries.2,4 Trying several different substitutes can help identify the most effective agent for a patient (Table 4).
Occasionally, patients with hyposalivation need systemic medication to improve their symptoms. These medications are called sialagogues, and these drugs require functional glandular tissue to be effective. The two main sialagogues are pilocarpine and cevimeline. Pilocarpine increases smooth muscle tone and motility of the gastrointestinal and urinary tracts, biliary ducts, and bronchi. In addition, pilocarpine stimulates water and electrolyte flow as well as other salivary components such as proteins. Excessive sweating, rhinitis, urinary and gastrointestinal disturbances, and a risk of cardiovascular and pulmonary effects are among its most common side effects. Cevimeline hydrochloride, is a newer drug and is more specific for salivary and lacrimal glands. Patients usually report fewer side effects with cevimeline.2,4,7
Sialagogues have a few major limitations, however. First, their side effect profile is extensive and, therefore, limits their use among patients with GI or cardiac risk. In addition, sialagogues are unable to protect salivary glands from the onset of progressive autoimmune disease or delay its onset. Finally, these systemic medications have little or no effect on the destructive effects of ionizing radiation.
The clinical complications of hyposalivation and xerostomia include, but are not limited to, caries, periodontal disease, mucosal abnormalities, halitosis, candidiasis, and difficulty with mastication, swallowing, and speaking.9,18 Therefore, the clinician cannot underestimate the importance of preventive measures in the overall management of a patient with reduced saliva. Increased frequency of oral and dental evaluation and recall maintenance every 2 to 3 months is imperative. Nutritional counseling recommending a low carbohydrate diet is also needed. In addition, topical fluoride applications, at home or in the dental office, with solutions, gels, foams, or varnishes, is important in preventing dental caries. The identification and management of other oral conditions such as candidiasis, bacterial infections, and ill-fitting prostheses is important.
Although a dry mouth is often not preventable, the effects it has on the oral cavity can be. It is important for all members of the oral healthcare team to understand the detrimental outcome that oral dryness or decreased saliva can have on a patient's mouth, body, and—ultimately—quality of life.
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13. O'Sullivan EM, Higginson IJ. Clinical effectiveness and safety of acupuncture in the treatment of irradiation-induced xerostomia in patients with head and neck cancer: a systematic review. Acupunct Med. 2010;28(4):191-199.
14. Vissink A, Mitchell JB, Baum BJ, et al. Clinical management of salivary gland hypofunction and xerostomia in head-and-neck cancer patients: successes and barriers. Int J Radiat Oncol Biol Phys. 2010;78(4):983-991.
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About the Authors
Katharine Ciarrocca, DMD, MSEd
Department of Oral Rehabilitation Division of Geriatric Dentistry
Oral Health and Diagnostic Sciences
Georgia Health Sciences University
College of Dental Medicine
Wendy S. Hupp, DMD
Assistant Professor of Oral Medicine
Department of General Dentistry and Oral Medicine
University of Louisville School of Dentistry
F. John Firriolo, DDS, PhD
Professor of Oral Diagnosis and Oral Medicine
University of Louisville School of Dentistry
Scott S. De Rossi, DMD, DABOM
Chairman, Department of Oral Health and Diagnostic Sciences
Director, Clinical Center for Oral Medicine
Associate Professor of Oral Medicine
Associate Professor of Otolaryngology/Head & Neck Surgery
Associate Professor of Dermatology
Georgia Health Sciences University