The aging population is the most rapidly growing segment of the U.S. population.1 The proportion of the population 65 years or older is projected to increase from 12.4 percent in 2000 to 19.6 percent in 2030.1 These demographic trends are even more dramatic for adults 80 years or older, whose numbers are expected to increase from 9.3 million in 2000 to 19.5 million in 2030.1 These changes are likely to have a meaningful impact on the oral health of the aging population.
Among the common problems in elderly people that have a significant impact on their quality of life are salivary gland hypofunction, the complaint of a dry mouth (xerostomia) and edentulism. The prevalence of xerostomia increases with age and affects about 30 percent of the population 65 years and older.2 As elderly people live longer in association with coexisting medical disorders, the likelihood of developing dry mouth problems increases.3,4 The number of edentulous older adults is growing as the population ages. While the prevalence of edentulism in each age cohort actually is diminishing, the actual number of edentulous adults and those wearing complete dentures in the United States is increasing because of the expansion of the aging population.5 In the United States, 24.9 percent of the population 60 years or older, or approximately 10.5 percent of the total population, are edentulous; that percentage is anticipated to increase to 15.5 by 2020.5,6 The wearing of dentures is complicated severely by a dry mouth, yet this problem has received insufficient research attention, and few proven treatments are reported in the literature.
We conducted a systematic review of the published scientific literature on articles published from January 1950 to the second week of September 2007, when applicable. We searched six databases: Ovid MEDLINE, Evidence Based Medicine Reviews Database, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, Database of Abstracts of Reviews of Effects and the Cochrane Central Register of Controlled Trials. Our literature search used the following key words: "denture," "hyposalivation," "xerostomia," "dry mouth," "elderly" and "aged." We limited the citation search to articles written in English and describing studies that involved human subjects.
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RESULTS
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We identified 11 articles3,4,7–15 from the literature search, none of them being a report of a randomized controlled clinical trial. The few clinical research studies published on the topic of hyposalivation and denture retention represent a low level of evidence for establishing clinical practice guidelines. Accordingly, no conclusions can be made regarding the effects of hyposalivation treatment on denture retention. It is strongly recommended that randomized controlled clinical trials be conducted in the denture-wearing population with dry mouth.
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DISCUSSION
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Saliva and oral health.
Saliva is a versatile substance that serves many purposes in the oral and pharyngeal environment.16 It is a lubricant that facilitates the swallowing of food, a mechanical device that cleans the dentition, an immunological barrier, a digestive initiator and an ionic stimulator for taste. Diminished salivary output from the major and minor glands is called "salivary hypofunction," and the subjective complaint of a dry mouth is termed "xerostomia." When salivary hypofunction occurs, it leads to a plethora of sequelae, including dental caries, candidiasis, erosion and ulceration of mucosal tissues, dysgeusia, dysphagia, gingivitis, halitosis and impaired use of removable prostheses.2,17,18
The minor salivary glands of the palate are called the "palatine glands." They are located primarily between the midline palatal suture and the vertical portion of the alveolar ridge, with ducts opening directly onto the mucosal surface. Palatine glands secrete mucins and immunoglobulins at a continuous slow rate, which protects and moistens the oral tissues. These minor salivary glands synthesize and store the mucin until they are stimulated by the parasympathetic system.19
Many older adults experience salivary gland hypofunction and complain of xerostomia.20 While it previously was thought that salivary function declined with greater age, it is now accepted that output from major salivary glands does not undergo clinically significant decrements in healthy people.21–24 Salivary constituents also appear to be generally age-stable in the absence of major medical problems and medications.25,26 It is likely that numerous systemic diseases (such as Sjögren syndrome) and their treatments (medications, head and neck radiation, chemotherapy) contribute significantly to salivary gland hypo-function in elderly people.2,17,18,27
Salivary hypofunction and xerostomia in elderly people.
Salivary problems are caused by local as well as systemic conditions.2,17,18,28 Oral sources of salivary gland disease are infectious (bacterial and viral), noninfectious (obstructions such as sialolith, mucocele, ranula) and neoplastic (benign: pleomorphic adenoma; malignant: mucoepidermoid carcinoma, adenoid cystic carcinoma). Systemic conditions are divided into systemic diseases, use of medications and the effects of head and neck radiotherapy. The most common systemic disease is Sjögren syndrome, an autoimmune exocrinopathy producing dry eyes and a dry mouth.7,8,29,30 Other pertinent diseases include rheumatoid arthritis, HIV infection, diabetes, Alzheimer disease and stroke.9,10 The most common cause of salivary disorders in elderly people is prescription and nonprescription medications, primarily because of certain drugs’ anti-cholinergic effects. For example, 80 percent of the most commonly prescribed medications have been reported to cause xerostomia,9 with more than 400 medications causing an adverse effect of salivary gland hypofunction.31 These medications include tricyclic antidepressants, sedatives and tranquilizers, antihistamines, antihypertensive agents, cytotoxic agents, antiparkinsonism agents and antiseizure drugs.32 Radiation therapy, a common treatment modality for head and neck cancers, causes permanent salivary hypofunction and persistent xerostomia.33
Treatment of salivary hypofunction involves identification of the causative agent and then appropriate therapy (such as antibiotics for bacterial infections and surgery for neoplasm).17 For most conditions, therapy requires replacement of lost fluid with artificial salivary formulations (gels, rinses, sprays) and salivary stimulation with prescription drugs (cevimeline or pilocarpine), sugar-free gums and mints.
The role of saliva in denture retention.
Saliva is critical for retention of and comfort in wearing removable prostheses.18 In the denture-wearing population, salivary wetting mechanics are necessary to create adhesion, cohesion and surface tension that ultimately lead to increased retention of prostheses. Adhesion is the bond created by saliva between the oral mucosal epithelium and the denture base. Cohesion is the bonding between saliva components that leads to greater retention of prostheses. Surface tension is the denture’s ability to resist separation from tissues and is related closely to the fit of the prosthesis. An intimate fit of denture bases to supporting tissues and the presence of adequate border seals will provide optimal denture function, provided that saliva is adequate in amount, flow and consistency. Saliva allows for the formation of a vacuum pressure on the seating of dentures and contributes significantly to denture retention and the wearer’s satisfaction with the prosthesis. Dentures can dislodge during function, and the presence of adequate saliva and swallowing allows for repeated seating of the prosthesis and subsequent retention and denture stabilization. Adhesion, cohesion and surface tension are interrelated, and they all depend on saliva.
Saliva also is necessary to prepare food for digestion and deglutition; its insufficient output adversely affects nutrition in the elderly edentulous population.12,34 Lack of saliva in the denture-mucosa interface can produce denture sores owing to lack of lubrication and prosthesis retention, as well as to a reduction in the number of immune factors that the salivary film provides. Lack of denture stability and retention can cause social embarrassment if prostheses dislodge during common functions; they ultimately could impair a person’s ability or willingness to speak or eat, particularly in public. Therefore, xerostomia and salivary hypofunction can have a devastating effect for the denture-wearing edentulous patient because of numerous compounding factors that affect chewing, swallowing, tasting and speaking.12,35
Xerostomia influences patients’ comfort and satisfaction with their dentures, but total salivary output may have less relevance to the denture-wearing population than may the flow from a specific gland. For example, there is only a slight correlation between the secretion from parotid glands and the retention of maxillary dentures.36 Alternatively, a significant relationship has been discovered between palatal salivary gland function and denture retention, independent of such factors such as alveolar ridge shape and mucosal quality.11,14 The palatal minor salivary glands play a strong role in the successful use of maxillary removable prostheses, and diminishment of their function because of a myriad of local and systemic factors as described above may predispose a patient to discomfort, impaired retention, mucosal irritation, fungal infections, dysgeusia and dysphagia.37
Dry mouth and dentures.
Patients with salivary hypofunction are more susceptible to mucosal candidiasis, which can manifest with a combination of a pseudomembranous covering, erythema of the underlying tissues and a burning sensation of the tongue or other intraoral soft tissues. Patients with complete dentures and hyposalivation who experience candidiasis may require extended antifungal therapy to eliminate the infection. Fungus-associated denture stomatitis usually is diagnosed by means of clinical findings, although microscopy can be used to confirm the clinical diagnosis by showing mycelia or pseudohyphae in a direct smear.13
In the patient with insufficient saliva, the lack of salivary lubrication can produce traumatic ulcerations of the mucosa. The ulcerations typically manifest as small, painful lesions with elevated circumferential fibrous tissue. In patients who wear dentures, if the cause of the ulceration is not treated, a frictional reactive hyperplasia can occur that develops into an epulis fissuratum. An epulis fissuratum appears as redundant tissue in the alveolar vestibule. Treatment of an epulis fissuratum or a fibroepithelial polyp requires complete surgical excision, and after surgery, the dentures must be refabricated, rebased or relined.
Although there is insufficient scientific evidence regarding the use of denture adhesives in general, their use to enhance retention of well-made prostheses is acceptable and, at times, necessary.38 Moistened denture adhesives improve adhesion and cohesion and create a uniform fill of material, particularly on well-made prostheses, that improves surface tension. Therefore, the use of adhesives in patients who have hyposalivation can lead to enhanced denture function and patient comfort. The patient should be educated regarding the daily use of adhesives and should be advised to visit the dentist annually to evaluate the adequacy of the prosthesis and the health of the underlying denture-bearing tissues.
Idiopathic dysesthesia or stomatopyrosis (commonly called "burning mouth syndrome") is diagnosed in patients with xerostomia who wear dentures by means of excluding fungal, traumatic, mucosal, neoplastic, endocrine, serologic or nutritional causes.39,40 It is characterized by a burning sensation in one or several oral structures in contact with the dentures. These patients’ oral mucosa have a normal clinical appearance; the cause may be that microfriction of the denture against the mucosa induces a dysesthesia.39 Although treatment regimens have been recommended for burning mouth syndrome,40 there has been little documentation on the condition in denture-wearing patients who have dry mouth.
Treatment of dry mouth problems in denture wearers.
There are a host of treatments for dry mouth,2,17,41–43 although remedies usually are palliative,44 and none are described specifically for the denture-wearing population. Initial therapy begins with a thorough assessment of the underlying cause. In elderly patients, this assessment must include a review of concurrent medical problems and medications—in particular, drugs with anticholinergic activity. In the denture-wearing patient, the assessment also must include the denture and the denture-bearing mucosal surface. If the dentist can see denture sores, he or she should consider that a poor denture fit may be a causative factor in the patient’s salivary hypofunction and must treat it. This typically is the case for overextended mandibular lingual flanges. Excessive pressure in the lingual anterior regions potentially can cause mucosal soreness as well as hypofunction of the sublingual and submandibular glands, and it requires adjustments to the prosthesis.45
Patients with insufficient saliva benefit from wetting their dentures before placing them in the mouth.6 Salivary substitutes, artificial saliva and salivary stimulants therefore can be beneficial for the denture-wearing patient in terms of helping with adhesion and cohesion and, subsequently, prosthesis retention. Patients can be advised to spray their prostheses with artificial saliva before denture insertion and before meals. During mealtime, greater intake of liquids, and of water in particular, is recommended. Increasing the wetting of the prosthesis enhances retention and stability during function, and this will aid in mastication and swallowing. Intermittent intake of water also can help during speech. Although the use of adhesives in patients with xerostomia and hyposalivation requires additional care, it often is necessary to stabilize a removable prosthesis. Patients should be instructed to wet their prostheses before applying adhesive,6 and a combined use of artificial saliva and denture adhesive appears to be beneficial.
There is a dearth of studies examining the use of adhesives and artificial saliva to enhance denture retention and reduce xerostomia in edentulous patients with salivary hypofunction. Furthermore, there is a need for the development of long-lasting materials that will improve patient comfort; increase ease of chewing, swallowing and speaking; and reduce common oropharyngeal problems, such as fungal infections, in these patients. As the aging population continues to expand and the number of older people requiring removable prostheses increases, there is a great need to identify existing and novel products that will enhance the oral health quality of life of denture-wearing adults who have dry mouth.
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SUMMARY
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We conducted a systematic review of the literature from six electronic databases from January 1950 to the second week of September 2007 by using the following key words: "denture," "hyposalivation," "xerostomia," "dry mouth," "elderly" and "aged." We limited the citation search to articles written in English and involving human subjects. We identified 11 articles in the search, none of which was a report of a randomized controlled clinical trial. These few published clinical research studies represent a low level of evidence for establishing clinical practice guidelines; therefore, we can make no conclusions regarding the effects of hyposalivation treatment on denture retention.
The edentulous population is increasing in the United States as the population becomes increasingly older. Concomitantly, xerostomia and hyposalivation due to concurrent medical problems and medications will affect an increasing number of elderly people, including the population wearing dentures. The vulnerable elderly denture-wearing population with xerostomia and salivary hypofunction is at risk of experiencing social withdrawal, malnutrition and a host of oropharyngeal problems. There are few adequate treatments for these common oral problems, and new therapies are required that will enhance denture retention, reduce dryness and enhance oropharyngeal health in older edentulous patients who also have xerostomia. Further prospective clinical trials are needed to establish a framework for evidence-based treatment for denture-wearing patients experiencing dry mouth.
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