SALIVARY GLANDS AND ORAL LESIONS IN DIABETES MELLITUS

Salivary glands and oral lesions in diabetes mellitus. An experimental and clinical study with special reference to the influence of metabolic control and duration of the disease Carl-Olof Reuterving Departments o f Internal Medicine, Oral Pathology and Pathology, University o f Umeå, Umeå, Sweden Diabetes mellitus is associated with several clinically significant abnormalities in the oral cavity and salivary glands, the most common being periodontitis, salivary gland enlargement and a sensation of dry mouth. The pre­ valence o f dental caries in diabetics is mostly reported to be decreased or unaffected. Since there is a shortage of information concerning the influence of metabolic control and duration of diabetes on these abnormalities, the present studies were performed. Three-month-old rats were made alloxan-diabetic and investigated after one and twelve months’ duration of dia­ betes for oral lesions and feeding behavior. They had free access to a standard pellet diet and tap water. Strepto­ coccus mutans and lactobacilli were naturally occurring. In diabetic rats the proportion o f the oral flora which was lactobacilli was positively correlated to the blood glucose level. Untreated long-term alloxan-diabetic rats de­ veloped advanced periodontal disease and root surface caries in the molars at sites o f interdental impaction of foreign material. The degree of alveolar bone loss was positively correlated to the blood glucose level. Diabetic rats were hyperphagic and had a longer total eating time, including day-time eating, mainly by having longer meals but no significant increase of meal frequency, as compared with non-diabetic animals. The untreated al­ loxan-diabetic rats developed reduced salivary gland weight which was o f the same degree in shortand long­ term diabetic animals. Shortand long-term untreated alloxan-diabetic rats showed a similar degree of morphometrically estimated lipid accumulation in the acinar cells of the submandibular glands, and the degree was posi­ tively correlated to the blood glucose level. However, lipid inclusion occurred only in rats with a morning non­ fasting blood glucose level exceeding 15 mmol/L. The capillaries in the submandibular glands of the untreated long-term alloxan-diabetic rats had a significantly increased thickness of the basement membranes as compared with the observations in short-term diabetic and non-diabetic rats. Untreated alloxan-diabetic rats were also shown to have a decreased salivary flow rate compared with non-diabetic rats, and the decreased flow was negatively correlated to the blood glucose concentration. Salivary flow rate increased with the duration of the disease. The diabetic rats had increased salivary glucose levels, which were positively correlated to blood glucose values when the latter were above 15 mmol/L, suggesting a threshold mechanism for salivary glucose excretion. Insulin therapy reversed salivary flow rate and salivary glucose concentrations toward normal. Salivary investigations were performed in eleven diabetic patients on two occasions with different metabolic con­ trol. Salivary flow rate showed marked interindividual differences but was not significantly changed by improv­ ed metabolic control although several of the patients initially had severely deranged glucose metabolism. A posi­ tive correlation between the glucose concentration in blood and saliva was seen in the parotid saliva during secre­ tory stimulation. No significant change in electrolytes, amylase or antimicrobial factors was found.