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Xerostomia (dry mouth) and Sjogren's Syndrome David Hay
Every day, over a 24 hour period, the average person produces at least 500ml of saliva. This material, which is a very complex fluid, is secreted mainly by three paired salivary glands. The largest, the parotid glands, are situated just below the ear and behind the angle of the lower jaw. The sub-mandibular glands are sited just in front of the angle of the lower jaw on its inner surface and the sub-lingual glands which are situated toward the front of the floor of the mouth between the tongue and the inside of the lower jaw. There are also many minor salivary glands under the mucosal surfaces throughout the oral cavity. Salivary flow rates vary considerably during any one 24 hour period depending on the demand or the current physiological status of the patient, for example:
Unstimulated/resting flow rate - 0.3ml/min [18ml/hour]
Flow rate during sleep - 0.1ml/min [6ml/hour]
Eating/chewing - 4.0-5.0ml/min [240-300ml/hour]
In Sjogren's Disease the production of saliva diminishes in proportion to the degree of progressive destruction of the salivary gland tissue. Diagnostic tests for xerostomia [pronounced 'zerro-stow-meeuh'] may include measuring the flow rate of the saliva; scintigraphy [where a dye is absorbed through the duct of the gland and is then measured in the gland substance]; microscopic examination of some of the salivary gland tissue usually removed from either the lower lip or the parotid gland. These special tests, when combined with the patient's history is usually sufficient to confirm the diagnosis. The spectrum of other signs and symptoms associated with the Sjogren's Syndrome may also be present to a variable degree.
FUNCTIONS OF SALIVA
Saliva is an important component of the environment of the oral cavity for many reasons. It is a natural cleansing agent of the teeth and gums helping to wash away accumulated food, debris, bacteria and plaque. It lubricates the soft tissues of the mouth including the gums, tongue, palate, floor of the mouth, cheeks and lips and, more importantly, the throat enabling swallowing to easily occur.
Saliva contains numerous proteins such as amylase [one of the digestive enzymes which starts the break-down of starch in some foods] and immunoglobulins which help to counteract infections and the stickiness of bacteria adhering to the teeth and soft tissue. In xerostomia some proteins may be missing or may be altered in their composition and function.
Saliva contains many inorganic elements, such as calcium and phosphate, which help to remineralise the teeth making them less susceptible to dental decay.
Saliva also contains buffering ['acid soaking up'] systems which neutralise and inhibit the effects of acids produced by the oral bacteria or which are included in the diet.
Xerostomia and hyposalivation [less salivary flow than normal] may be a most unpleasant and devastating problem for the patient with Sjogren's Disease. Decreases in the quality as well as alterations in the composition of the beneficial constituents of saliva predispose the patient to many problems.
The lips may become dry, sore and cracked. A common complaint is a dry and burning tongue. Swollen, tender salivary glands and angular cheilitis [a cracking of the corners of the mouth] can be unpleasant. All the soft tissues of the oral cavity may have a thinner layer of cells than normal and, therefore, may be more susceptible to damage. Taste sensation can be altered because there is inadequate liquid to dissolve tastants in the food so that the taste buds can be activated.
Sjogren's patients may be prone to secondary oral infections, principally from the yeast-like organism, Candida albicans, which produces the condition candidosis [thrush]. Candidosis may present clinically in a variety of forms, the most common being a generalised inflammation of the mucosal [skin] surfaces of the mouth and tongue on which there can be small superficial whitish patches. These may be removed leaving a red area underneath which often bleeds easily. The corners of the mouth may be infected [angular cheilitis] and this is a common problem especially in denture wearers. Candidosis may be associated with a tender/burning sensation which can be aggravated by hot or spicy foods.
Lack of saliva may affect the nutritional status of the individual because eating and swallowing becomes such a time-consuming ordeal, while talking and conversing may become impossible without frequent sips of water or alternative lubricants.
Denture wearing may become difficult because dry mouth can significantly add to the problem of retaining and eating with the dentures, which invariably become loose.
Of particular importance is the problem of greatly increased dental decay which can occur in patients who have their own natural teeth. In order to understand why the teeth can demineralise or decay so rapidly when there is a dry mouth some understanding of the physiology of the oral cavity is necessary.
Tooth structure is rather like reinforced concrete. There is a framework of tough, strong collagen fibres [like the steel framework of a building], around which is deposited the crystalline minerals of the tooth [concrete] that gives the structure its rigidity and toughness. The crystal/mineral part can be dissolved out by acids. In a patient with normal salivary function there is a balance between the minerals contained in the saliva [which is saturated with calcium salts] and tooth structure. That is, should a small amount of mineral be dissolved out of the tooth, then calcium crystals will tend to be deposited back into the tooth via the saliva. This process is greatly enhanced by the presence of 'fluoride ion' [which is the reason for the incorporation of fluoride in water and toothpastes] and the re-formation of tooth mineral crystals is rather like the way in which crystals of alum or copper sulphate can be built up in a school chemistry experiment.
The structure of the teeth will actually start to dissolve away in solutions where the pH [acidity] is 5.5 or less! The scale which measures degrees of acidity or alkalinity is known as the 'pH' scale, where pH 7 is neutral, pH 14 is highly alkaline and pH 0 is highly acid.
Thus, normal salivary flows with normal mineral content and normal buffering capacity [normal 'acid soaking up' properties], is a most important physiological mechanism for maintaining the integrity of tooth structure. When saliva is reduced or absent then mineral replacement of tooth structure does not occur, any acid attack on the tooth lasts for longer and, as a consequence, there is a net loss of calcuim salts from the tooth structure and dental decay rapidly supervenes.
Under what conditions does the tooth environment become sufficiently acid to cause mineral loss? There are, in fact, two ways in which this can occur.
1. Acidic foods and drinks
Food and beverages which are part of the normal diet can vary considerably in acidity or alkalinity. It is important to know all that commercially available carbonated fizzy drinks and commercially available fruit juices, eg Coke, Fanta, Lemonade, L&P, Fresh Up, Just Juice, McCoy, Twist, Arano etc [this is not a complete list], range from pH 3.8-2.4. Although some fruit juices have a natural acidity all products are adjusted to have pH 3.8 or less in order to prevent bacterial contamination and to prolong shelf life. Lemon and Glycerine Mouth Swabs, designed to 'freshen up the mouth', also have pH 2.4.
In other words all these products are capable of dissolving tooth structure and can demineralise the teeth. Such beverages tend to be drunk, sipped frequently or used during the day by people with dry mouth to keep the mouth moist. Usually, in a person with normal salivary flow, not much damage occurs [unless the materials are used habitually or excessively] because the normal compensatory mechanisms described above are active and any adverse effects of food or beverage acids is rapidly eliminated. But tooth mineral loss in a person who has xerostomia can be significant under these conditions because the compensatory mechanisms are absent or reduced. This does not mean that such drinks should be completely avoided. It does mean that they should not be used continually as mouth moisteners or oral lubricants.
2. Dental Decay
In the mouth there are some 27 species of microorganisms [bacteria] to be found. These are considered to be normal inhabitants of the oral cavity in the same way that all parts of the body have a normal resident microflora. In the mouth these microorganisms grow rapidly over the tooth surfaces forming 'dental plaque'. Plaque is usually partially removed by regular oral hygiene methods such as tooth brushing and flossing but it is impossible to remove every vestige of plaque from all the nooks and crannies of the teeth and gums and after tooth cleansing plaque builds up again quite rapidly by bacterial cell division and multiplication.
Some species [families] of plaque microorganisms use sugars in the diet for their own energy and metabolic requirements. Their waste products are strong organic acids which are excreted into the plaque thus creating an environment around the teeth which is acidic enough to dissolve the minerals out of the tooth. In fact, the acidity of the plaque may fall as low as pH 2.5!
In a patient with normal salivary flow the effects of this acid production are, again, quite quickly neutralised by the diluting and buffering action of saliva. When there is reduced or absent saliva the acids remain undiluted, the buffering systems do not work and the tooth structure is exposed to the effects of acid for much longer which, in turn, leads to greatly increased tooth decay. Careful attention to oral and tooth hygiene is important in all patients but is mandatory in those who have xerostomia where plaque control is of vital significance in the prevention of dental decay. Plaque control may be enhanced by the regular use of antiseptic mouthrinses [eg chlorhexidine gluconate 0.2% (products: Savacol by Colgate or Chlorhexidine Mouthwash by Delta West)]. The use of a fluoride containing toothpaste is also recommended.
Hence, the action of the oral bacteria on the sugar sweetners in foods and drinks to produce acidic plaque together with the acidity of the drinks themselves can cause an additive effect and the end result can be an increase in dental decay and tooth demineralisation.
Xerostomia and its sequelae are managed according to severity.
1. First, if there is some secretory glandular tissue working, it can be stimulated by chewing gums or sucking sweets. This may be sufficient to maintain adequate lubrication in the mouth between meals for talking and normal activities. However, it is vital that if you have your own natural teeth, such gums or sweets are sugar free [otherwise dental decay via conversion of sugar to acids by the microflora in the mouth will occur]
Example products: Sugar free gums.
V6 gum - this product contains urea which leads to an alkaline environment in the mouth, which in turn, actively neutralises acid production and discourages tooth mineral loss.
Sugar free sweets.
2. The drug Pilocarpine appears to be a useful sialogogue [salivary stimulant] but, as with all drugs, there are side effects and the patient needs to be carefully screened for heart disease, diabetes and other medications first. Although this drug may increase salivary flow, patients can find the side effects unacceptable.
3. WATER, Water, water - sipped frequently as desired.
4. Saliva replacements. Generally these are compounded from methyl- cellulose [the base which contains the lubricant] plus a variety of other compounds designed to mimic true saliva as much as possible. Patients complain that these feel greasy. A mucin based artificial saliva has recently been introduced which more closely resembles saliva itself. The price of these materials is off-putting.
Example products: Luborant [methylcellulose base]
Saliva Orthana [mucin based].
These saliva substitutes are not suitable when eating and at the present time there is little available except to increase fluid intake during meals.
5. In patients with dry mouth denture wearing can be a major trial because retention of dentures relies considerably on the good fit of the prosthesis but also on the surface tension effect of the viscous saliva under the denture. The saliva 'seals' the edges of the denture preventing air from getting under the appliance which would allow it to drop. In xerostomia this component of denture retention can be largely absent. There are some aids for retaining the dentures which rely on the application of a thick sticky material which causes a semi-adhesion of the denture to the underlying tissues.
Example products: Polygrip
5. It can be seen that in order to prevent, as much as possible, the problem of extensive and rapid dental decay and to ensure that dentures are maintained, regular dental examinations are a priority. In the case of those who have their natural dentition a dentist should be able to advise in appropriate oral hygeine techniques eg brushing flossing, antiseptics, fluoride applications/rinses. Use F' toothpastes.
Example products: Savacol [chlorhexidine gluconate 0.2%]
Fluoride containing toothpastes
Biotene Antibacterial Dry Mouth Toothpaste [designed to help tooth remineralisation and to replace salivary antibacterial activity by including several ingredients present in normal saliva]. Not currently available in NZ.
Oralbalance [designed to use with Biotene and also contains similar ingredients and enzymes]. Not currently available in NZ.
6. Avoid acid juices and avoid acid oral swabs. Many people resort to using fruit juices/carbonated fizzy drinks to make the mouth feel nice and to keep it damp. Unfortunately, if used habitually, all of these drinks will demineralise the teeth.
7. Infections of the salivary glands require antibiotic therapy or, if persistent, consideration may need to be given to surgical removal of the gland/s. Candidosis may require prolonged courses of antifungal agents.
The general management of the oral problems associated with this extremely unpleasant and inconvenient disease have been outlined in this paper and the importance of regular dental maintenance has been emphasised.
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