Saliva is the natural environment of the mouth. Its presence is essential for the proper functioning of both hard and soft tissues. When we run out of saliva, normal activities such as eating or talking may become hard to bear.
In adults 0,5 to 1 litre of saliva is produced on daily basis. Physiologically the secretion drops at night and increases during ingestion. The presence of saliva is a result of the intense work of salivary glands: six large and about four hundred small glands. When these delicate structures become damaged, normal functioning becomes extremely uneasy. The presence of saliva is invaluable for the human body. Not only it hydrates the mucosal surface allowing painless swallowing and speaking (the presence of mucin and glycoproteins), but also plays an important role in acid buffering (bicarbonates and inorganic phosphate), protects the teeth by the remineralization properties (calcium and phosphates), has antibacterial properties (lysozyme, lactoferrin, and other compounds) and also takes part in the initial food digestion (the presence of enzymes such as amylase, lipase, protease).
It is estimated that around 80 million people suffer from xerostomia – persistend dry mouth caused by the insufficient saliva flow. When the salivary flow is reduced to the level of <0,1ml/min (hiposalivation) the patient experiences discomfort linked to the dry mouth. The lower level of saliva, the worse the mood, the greater the isolation from society. Painful speech leads to withdrawal from social life, while pain during swallowing may contribute to eating disorders.
The salivary flow disorders are linked particularly close to drugs, chemotherapies and radiotherapies, and some systemic illnesses. Medications that cause dry mouth is a group of over 500 known substances. The main drugs inducing xerostomia are: anticholinergics (atropine, antidepressants, antihistamines) and sympathomimetics (amphetamines) and other drugs like tramadol lithium, omeprazole, diuretics, prostease inhibitors). Some drugs such as hydralazine, busulfan or thiabendazole induce symptoms similar to the primary Sjögrens’ syndrome. Nevertheless drug induced xerostomia is usually temporary and treatable.
Worse situation occurs when we deal with radiation-induced xerostomia. Delicate tissues of the salivary glands, parotid gland in particular, exposed to the X-rays face rapid destruction. 52Gy is a single dose that can cause irreversible damage to the salivary glands, leading to the reduction of salivary flow. The average dose used in oral cancer radiotherapy is estimated between 60-70Gy and it leaves a patient with the level of salivary flow assessed at 5% of the original production. After 5 weeks of intensive cancer treatment the saliva flow is almost non-existent. Time after time a hypertrophy of the extant salivary glands takes place in order to make up for the cell loss. Unfortunately the saliva secretion never will be able to reach the original level. Damage of the salivary glands may be also caused by chemotherapy (xerostomia observed in more than 50%of patients) and graft versus host disease.
Systemic diseases leading to the xerostomia formation are among others: Sjögren;s syndrome, HCV infection, sarcoidosis, AIDS and diabetes. The ways in which the salivary glands are being destroyed differ from one disease to another, but all of them lead to increased susceptibility to dental caries and gingivitis, dysarthria, dysphagia, susceptibility to fungal infections, burning tongue sensation, cracking lips and salivary glands enlargement.
If the patient suffers from dry mouth for more than three months xerostomia should be suspected. Confirming sialometric, sialographic, sialoscyntigraphic, sialochemical tests and biopsy should then be performed.
Depending on the degree of damage to the salivary glands many different therapies are used. For small lesions the non-pharmacological ways to stimulate the salivary glands have been used: chewing gum, physiotherapy, acupuncture and electrical stimulators situated in special overlays. Frequently prescribed are the medications that increase saliva production (eg, pilocarpine, cevimeline, bethanehol, karbacholine, pyridostigmine, bromhexine). When stimulating the salivary gland is found to be ineffective in abolishing symptoms, patients resort to oil based lubricants with antibacterial and soothing properties. Such measures are available over the counter in gel forms, rinses, and sprays. Novel devices automatically dispensing lubricants into the mouth and electrostimulating overdetures mainly is a domain of Israeli companies.
Discomfort felt by the patients suffering from xerostomia prevents them from normal functioning . Easing the symptoms is difficult, and general practitioners and pharmacists are not always able to help people looking for advice on the dry mouth topic. The problem of xerostomia should be the reason for greater caution during radiological diagnostics of the head and neck.