It is wisely said that the worth of something is known only when we lost it. Saliva being an essential complex fluid in the oral cavity, is composed of water (99%) and a variety of non-organic and organic substances including enzymes, hormones, antibodies, antimicrobial constituents and growth factors. Saliva helps to prevent dental caries, promotes remineralisation of the incipient caries, has buffering action on acid produced by oral bacteria and prevents other types of oral infections. Thence, saliva plays a vital role in the oral cavity and any deficiency or its absence will affect the quality of life undeniably. Xerostomia (ZEER-oh-STOH-mee-ah), or better known by “dry mouth” is the state of reduced salivary volumes and remains a subjective complaint.
Many a times, in the state of nervousness or when the person is upset or under stress, dry mouth can be experienced. But a relative longer duration of xeroted mouth is a matter of concern. Xerostomia is not a disease by itself but a sign of certain diseases and conditions which might pose serious health issues.
Xerostomia is a common symptom with an estimated prevalence of 20% in the general population and an increased (30%) prevalence rate among the females. As xerostomia or a dry mouth state is relatable to emotional inhibition of the salivary secretions, it has been used as a lie detector in criminal offences.
What all causes dry mouth??
To be simpler, when the saliva produced by the salivary glands is not enough to keep the mouth wet held responsible for dry mouth. There may be varied reasons for not producing enough of saliva which continues as
- Iatrogenic causes: These occur during any medical treatment including drug therapy, local radiation, chemotherapy or graft versus host diseases.
Drugs: With about 500 reported drugs, these are the most frequent cause of dry mouth especially in the elderly. Few of the reported drugs causing xerostomia are listed as
- Anticholinergic drugs: Atropine, Scopolamine etc.
- Antihistaminic drugs: Pheniramine maleate, astemizole, chlorpheniramine etc.
- Antihypertensive agents: angiotensin converting enzyme inhibitors, angiotensin receptor blockers, ∞ and β adrenergic blockers, diuretics
- Opioids: Morphine, codeine etc.
- Psychotropic agents: antidepressants, antipsychotics
- Skeletal muscle relaxants: cyclobenzaprine, orphenadrine etc.
- Sedatives and anxiolytics: alprazolam, diazepam etc.
- Nonsteroidal anti-inflammatory drugs (NSAIDS): ibuprofen, naproxen etc.
Majority of the medications do not affect the salivary glands but the probability of the decreased unstimulated saliva increases. The synergistic effects of xerogenic medications, multiple medications (polypharmacy), higher dose of medication and the time of starting the
medication increases with the increased rsk of dry mouth which is prevalent in the older people.
1. Radiotherapy and Chemotherapy: These are the primary, concomitant treatment modality employed in all head and neck tumors. The fractionated dose of 10 grays (Gy) weekly i.e., 2Gy daily for 5 consecutive days over 5-7 weeks with at a total dose of 50-70 grays is the standard radiotherapy dose for head and neck cancer. Doses greater than 60 Gy poses permanent damage to the salivary glands with no recovery in salivary hypofunction over time. Radiation induced xerostomia starts in the first week of radiotherapy itself with 50-60% decrease in the salivary flow which continues to diminish to about 20% in 7 weeks. Acute effects of radiation therapy on salivary function starts in the first week of the exposure and continues progressively. The accompanying side effects in the oral cavity include mucositis (inflammation of oral mucosa), dysphagia (difficulty in eating food), erythema and mucosal atrophy.
Many of the malignant tumors are treated either by chemotherapy alone or with a combination of radio and chemotherapy. Xerostomia, being the forth most common side effect of chemotherapy makes the saliva thick and thus increasing the incidence of dental caries.
- Developmental causes: The poor development of the salivary gland known as salivary gland agenesis or any congenital obstruction in the salivary gland duct leads to poor formation and flow of the saliva brings around xerostomia.
- Pathologic causes: Any disease or infections pertaining to salivary gland or its duct often leads to the condition of dry mouth. Sialolithiasis or calculi or stones in the salivary glands or ducts causes stagnation of the saliva. Salivary stones are typically composed of calcium phosphate and hydroxyapatite. Though, liths can be found in any of the major or minor salivary glands or its ducts but they are most commonly found in submandibular salivary gland duct. The long, tortuous course of the submandibular salivary gland or the Wharton’s duct and the salivary flow through it against the gravity makes this gland more prone for the development of stones. The patient suffers intense pain immediately after having meals and also experience reduced salivary flow due to the obstruction in the salivary duct.
Any bacterial or viral colonisation in the salivary gland or its ducts leads to sialadenitis accompanied with dry mouth, purulent discharge, swelling and severe radiating pain. Parotid gland being most commonly affected, presents with marked suppuration. The pus is cultured to mark the confirmation and the treatment is planned accordingly.
Sjogren’s syndrome is an autoimmune disorder primarily affecting salivary and lacrimal glands. In accordance with the literature, the Swedish ophthalmologist Henrik Sjogren first described the syndrome in a group of women with the symptoms of xerostomia, rheumatoid arthritis, and eye dryness termed as kerotoconjunctivitis sicca. With the further researches, it was confirmed that the primary sjogren’s syndrome or sicca syndrome, SS1 is limited only to the eyes and the mouth whereas the secondary sjogren’s syndrome, SS2 involves the connective tissue causing rheumatoid arthritis, systemic sclerosis or systemic lupus erythematosus.
Uncontrolled diabetes mellitus with polyuria and poor hydration often reports with the condition of dry mouth. Poorly controlled diabetes presents with the reduced salivary flow. Among the diabetic patients with xerostomia, oral candidiasis, median rhomboid glossitis, denture stomatitis and angular chelitis with denture are commonly associated.
HIV/AIDS associated with a group of disorders affecting varied organs and systems. The involvement of the major and minor salivary glands affects the acini and thus the production of saliva leading to dry mouth.
There are several other disorders that might cause xerostomia. Any damage to the nerves signalling the saliva production or its flow will cause dry mouth. Other diseases like hypertension, depression and dementia of the Alzheimer’s type often causes oral dryness with poor parasympathetic stimulation as one of the etiological factors.
To what dry mouth leads to??
The condition of dry mouth or xerostomia affects the quality of life in different ways. To list a few, we have
- Dysphagia, difficulty in eating or chewing food
- Dysguesia, altered taste sensation
- Dysarthria, difficulty in speaking causing slowed or slurred speech
- Halitosis, bad breath
- Oral candidiasis and ulcerations
- Cracked, fissured lips and the corner of the mouth
- Fissured, erythematous tongue with burning sensation
- Increased incidence of dental caries
- Periodontal diseases with accumulation of plaque and calculus
- Denture wearers feel discomfort while wearing the dentures
Methods to investigate xerostomia
The history given by the patient about his oral dryness plays a significant role in the diagnosis of xerostomia. Particular attention should be given towards the reported symptoms, medications used and the past medical history. Several of the researchers have prepared a questionnaire (shown in the table) for the patients suffering from dry mouth condition. The mouth mirror test, where back of the mouth mirror is drawn along the buccal mucosa and the friction is recorded accordingly. Salivary function tests with the assessment of the stimulated and unstimulated salivary flow forms the important diagnostic tool. Unstimulated saliva includes saliva from both the major and the minor salivary glands and the salivary flow of less than 0.1ml/min is considered as hyposalivation.
Questionnaire assessing xerostomia
Stimulated saliva is collected after the patient has chewed a gum and 0.5 ml/min or less salivary flow is considered to be hyposalivation. Salivary flow rate is measured by sialometry. Salivary gland imaging including sialography helps in demonstrating the gland structures or visualising the calculi. Salivary gland function is well assessed by using salivary scintigraphy. The ductal and acinar structures are visualised using ultrasonography while the parenchymal structures of the salivary gland tissue is demonstrated using CT scan and MRI. Schirmer’s test and Rose Bengal staining also helps in the detection of the less salivary and lacrimal flow. Minor and major salivary gland biopsy proves to be useful in cases like Sjogren’s syndrome, amyloidosis, HIV/AIDS and in malignancies.
How xerostomia can be managed??
Early diagnosis and subsequent treatment can slow down the progression of dry mouth and improve the comfort of the patient. A multidisciplinary approach including the following components is found helpful in treating the cases of xerostomia:
- Patient education
- Managing the systemic health of the patient
- Preventive measures
- Pharmacologic treatment
- Other methods
Patient education: The patients should be well educated with detailed information regarding the causes of oral dryness and its consequences. The emphasis should be given on the regular oral hygiene measures, use of topical fluoride, regular visits to the dentist to be followed by the patients. Counselling sessions on cessation of the tobacco use habit and other interventions to be conducted on regular intervals in the benefit of the patients.
Systemic health management: It is the duty of the dentist to keep an eye over the medications used by his patients in order to avoid the use of over the counter drugs causing xerostomia. The prompt diagnosis of the systemic diseases also helps to avoid the dry mouth condition.
Preventive measures: Preventive care is utmost important and has to instituted to avoid the oral complications pertaining to xerostomia. The patients should be asked to drink as much as water as they can or consume sugarless drinks to keep themselves hydrated. Chewing sugarless gums or sugarless hard candy or citrus, cinnamon or mint flavoured candies helps to stimulate the salivary flow. The spicy or salty food should be avoided as these might cause pain in the oral mucosa. Use of humidifiers in the night time helps keeping the mouth moistened.
Pharmacological treatment: The ultimate goal of any treatment modality including pharmacological measures is to improve the salivary stimulation. Lubricating agents in the form of gels, mouthwashes, lozenges and toothpastes helps dampening the oral mucosa. Sialogogues like Pilocarpine, Civemeline, Bethanecol, etc. directly stimulates the salivary glands and thus increasing the salivary flow. Pilocarpine and Civemeline are the cholinergic agonists and used widely in cases of xerostomia. Pilocarpine in the dosage of 5mg 4 times daily or 10 mg thrice daily is found successful in stimulating the salivary flow. 30 mg Civemeline used thrice daily helps cure xerostomia secondary to irradiation, Sjogren’s syndrome, HCV infection, and drug therapy. Bromohexine (32-48 mg daily) and Zidovudine found successful in improving the salivary flow rates and limiting the oral symptoms especially in cases of Sjogren’s syndrome. A significant reduction in xerostomia is seen with the regular infusion of infliximab for about 1 year.
Administration of interferon-∞ both parenteraly (3 x 106 IU/week) and IM (1 x 106 IU/week) increases the salivary and the lacrimal flow by increasing the transcription and production of aquaporin-5. Corticosteroids like 2mg/ml helps reducing the oral and ocular symptoms in cases of Sjogren’s syndrome. Immunosuppressant drugs like cyclosporine, cyclophosphamide and thalidomide are found improving the symptoms of xerostomia.
Also, artificial salivary substitutes are available which help dampening the oral mucosa. The preparations like mucins, glycoproteins, salivary enzymes and polymers like carboxymethylcellulose protects the hard tissues of the teeth from dissolution in the dry oral environment. Salivix pastilles act as local salivary substitutes prevent the condition of dry mouth.
Other methods: Salitron increases salivary stimulation by neuroelectrostimulation. In the first generation stimulator, intraoral probe is applied to the mucosal surface daily for a few minutes. Second generation stimulator is a removable appliance produced for individual patients. Dental implant based third generation device is in the miniature form and generates frequent stimuli and senses wetness/dryness of the mouth. It is a remote controlled device and can be easily operated by the patient.
Acupuncture increases the parasympathetic activity and stimulate the salivary flow by helping release the neuropeptide. Hyperbaric oxygen (HBO) therapy is popular in the treatment of radiation- induced xerostomia. Tissue engineering with artificial salivary gland mimics the natural duct system and helps in improving the flow of the saliva in the oral cavity.
On a concluding note
Dry mouth has always been a matter of concern for the patients as well as the clinicians. Our oral health and function depends on salivary function and hence, proper assessment, early recognition and prevention and treatment of the patients suffering from xerostomia found an utmost importance.
