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Swelling of salivary glands may results due to chronic and acute inflammation, which arise in certain autoimmune diseases, by duct obstruction due to sialolithiasis and tumors. The incidence of drug induced xerostomia is high in elderly people whereas certain other factors such as radiations and viral infections such as Hep. C, HIV and EBV are major etiological factors for xerostomia. Caries incidence also increases with xerostomia. Malignancy is also an important cause of salivary gland enlargement.
Salivary gland disorders and pattern of incidence varies among different age groups. Sialolithiasis (acute and chronic) responds better to surgical treatment rather than conservative approaches. Malignant tumors are common among adults. Topical as well as systematic therapies are useful for xerostomia. In future genetic engineering will prove to be fruitful in the in salivary gland diseases.
Saliva is glycoprotein in nature and is produced by major and minor salivary glands. Secretion of saliva is a reflex function emanating from salivary centers and is dependent on afferent stimulation. Major role of salivary gland is mucin production, which act as a lubricant to keep the old cavity moist. Saliva is also involved in perception of taste as well as limit the bacterial aggregation and also help to maintain the integrity of enamel.1 If the production of saliva is disrupted, then it can lead to caries and several other periodontal diseases.
Normal saliva production is about 500ml per day 2 and saliva flow rate varies in 24-hours, which is dependent upon the demand and physiological state of the patient. Salivary secretion is under the control of autonomic nervous system. Diseases of salivary glands can lead to the gland enlargement, pain as well as xerostomia. There are many reasons for xerostomia such as Sjorgen's syndrome and exposure to radiations. Certain drugs with anticholinergic effects and sympathomimetic actions are also associated with xerostomia.3
Other important causes of long standing xerostomia are:
Viral infections e.g. HIV, HCV etc.
If xerostomia is prolonged it will have an unpleasant feeling and thus affecting the quality of life.4, 5 Some systemic as well as local therapies are used recently to overcome xerostomia. Salivary glands disorders vary among different age group i.e. children and adults, but some diseases such as parotitis epidemica and cytomegaly can occur in both.6 Choice of antibiotics is different for different age groups. According to some studies, acute and chronic sialadentitis as well as secondary inflammation associated with sialolithiasis are common among different age groups.7, 8, 9 The pathogenesis of certain diseases are still not understood. Therapeutic strategies based on the clinical experience cannot be defined due to small number of patient in each age group. Various bacterial and viral infections are related with sialadentitis. The major cause of parotid swelling is parotitis epidemica 10 and it is more prevalent among the ages of 2 to14. 11
Underlying systemic diseases, such as fever, dehydration and immunosuppression are often related to acute inflammation of parotid gland. 12, 13
Inflammation of submandibular gland is due to duct obstruction or some congenital anomaly. Reports about sialolithiasis in submandibular duct and neoplastic changes in newborn and in adults are very uncommon.14
For chronic sialadentitis, the etiologic factors are disorders related to secretion and some immunological reactions. Salivary gland disorders could be extrahepatic manifestation of HCV, HIV and EBV. 15, 16, 17, 19
Average daily production of saliva is 500ml, decreased production of saliva is known as xerostomia.
Several drugs with anticholinergic and sympathomimetic actions are the potent causative agents for xerostomia.
Salivary glands are highly prone to damage after exposure to radiations. In oral cancer treatment the administration of 60-70 Gy radiations can lead to rapid reduction in flow rates and after 5 weeks the flow eventually ceases.
Chemotherapy used in the treatment of cancers can contribute towards dryness of mouth as well as production of saliva having a thicker consistency. 20
Sjorgen's syndrome can lead to dryness of eyes and mouth. 21, 22
Sarcoidosis (9% patients) can lead to salivary gland enlargement especially of parotid gland. 23
About 4-8% of adults and children with HCV infection can have complications associated with salivary glands as well as xerostomia. 24, 25
Sialolithiasis is rarely observed in infants and adults, youngest case observed in 2years old child. 26, 27
Salivary gland swelling can be due to malignancies. Parotid gland is the most common gland involved in malignancies. 28, 29
66.6% tumors of salivary gland are non-epithelial of which 75-80% are benign while 20% are malignant tumors.28, 29
Salivary gland tumors are more common in adults.
10% of benign tumors are associated with submandibular gland.
Xerostomia is an abnormal reduction of saliva and it result due to certain diseases or by the use of certain medication. In a day average person produce saliva of about 500ml. However flow rates varies when depends upon the demand and physiological state of a patient
Flow rate at rest in 0.3ml\min
During sleep, is 0.1ml\min
During eating ,is 4.5ml\min
Salivary secretion is dependent upon several ordinarily influences that act through the calcium dependent or cyclic adenosine path way. Saliva produced under the parasympathetic stimulation have low protein content whereas less saliva produce under the sympathetic stimulation and have a high protein content. Lesser amount of saliva with high protein content can give rise to sensation dryness. 30 Patients who are in anxious or depressed states also report for having dry mouth. Prevalence of caries is increased among the xerostomic patients.
Etiological factors contributing towards xerostomia
Diseases of the salivary gland
Now a day's about 500 medicines are associated with xerostomia. Moreover the synergistic effect of some medication have been recognized which are more prevalent among the elderly people. 31 The main mechanism for the drug induced xerostomia is due to sympathomimetic or anticholinergic action. It is more common in patients who are treated for hypertension or for some other psychiatric illness. Some drugs such as lithium, omeprazole, protease inhibiter are potent contributors towards xerostomia in about 7% of the patients using protease inhibiters may have xerostomia. 31
Radiations can cause damage to salivary glands whereas parotid glands are highly suspected to damage. 32, 33 If the dose of the radiation is as low as 20 Gy salivary flow will permanently ceases if it is given as the single dose in administration of 60-70Gy can cause rapid decline in the flow during in initial first week of treatment. There is a direct proportional relationship between degree of exposure to radiation and degree of xerostomia induced. 20 Whereas the partially radiated patients have increase saliva flow rates.
Various malignancies are treated with the combination of radiation and chemotherapy in a study of about 127 patients 34, 35 having an advanced cancer and xerostomia. Drugs used to treat cancer can produce thick saliva which lead to dry sensation of mouth.
Disorders of salivary glands:
Sjorgen's syndrome: 21
It is a chronic immune mediated disorder which is characterized by inflammation of exocrine glands which can lead to symptoms of dryness. It can be classified as primary disease in which sign and symptoms appears in eyes and mouth. It may be classified as secondary SS in which xerostomia and xeropthalmia appears. The cause of disease is profound in lymphocytic infiltrate in salivary glands. 36
Chronic Sarcoidosis can give rise to xerostomia as well as salivary gland enlargement in upto 9% of affected patients. The incidence of this disease is greater in parotid gland. 37
4-8% of adolescents and infants with HIV are associated with the salivary gland disorders particularly with xerostomia and enlargement of salivary glands. 38
Xerostomia is a predominant among patients infected with HCV and salivary flow rates are also reduced significantly\. 24, 25 Pathologic features of HCV associated sialadentitis are similar but not identical as those with SS 39, which is associated with a low degree of inflammation being found in HCV.
Other causes of xerostomia's:
Biliary cirrhosis 40
Cystic fibrosis 41
Diabetes mellitus 42, 43
Salivary gland agenesis, ectodermal dysplasia, and triple A syndrome are the rare causes associated with xerostomia.
Salivary gland tumors:
Salivary gland tumors make up of about 0.3% of human tumors, 10% are all of head and neck, where as 5% of such tumors are prevalent among 16 years of age.
Parotid gland sialadentitis:
It's rarely observed in children 19 according to a study done on 635 patients; only one case is observed in a 44 year old boy, 7 cases reported in 25 years. Chronic sialadentitis parotitis is an autoimmune disease. It starts between 3-6 years of age and peak incidence in 5-10 years of age
According to various studies all benign tumors of salivary glands are associated with parotid gland. 29, 44, 45 Ussmiller46 observe the predominance of non epithelial benign tumors in 15 years of age
Uncommon in children and adults .these can be mucoepidermoid carcinoma , adenoid cystic carcinoma and acintic cell carcinoma , according to Enerott(47) 2637 patients were observed and are more commonly prevalent among adults , 15-25% malignant in adults.
Therapies designed for xerostomia includes
Systemic therapy ; drugs like pilocarpine , bethanacol , cevimiline reduces the drug induced xerostomia
Oral care for patients having salivary gland disorders oral hygiene should be maintained and dentures should be well fitted
Some topical therapies are also available for the treatment e.g. Sugar free gums , candies 48, 49 mucosal sprays 50, humidifiers 51
For sialolithiasis, antibiotics and therapeutic doses are required. Inflammation associated with sialadentitis in adult requires surgical procedures.
In future the technology of genetic engineering proves fruitful in the treatment of disorders of salivary glands.
Salivary gland disorders are scarce among children and adolescents. Acute and chronic sialadentitis requires surgical treatment in adults, however spontaneous healing can occur in infants. Parotid gland malignancies are more common in adults. There is a triple association with HCV, Sjorgen's syndrome and salivary gland lymphoma and the HIV is involved in lymphogenesis. Several systemic and topical therapies are effective in management of xerostomia.
However in future gene therapy and tissue engineering can be better treatment options, but the etiology and pathogenesis of the disease should be completely known. 52