The correlation between the viscosity of the whole saliva and its mucin concentration or the degree of clinical findings in patients suffering from periodontal diseases was investigated.
Clinical findings were examined in the facial surface of the four first fully erupted molars, and in the facial surface of the maxillary right central incisor and mandibular left central incisor as follows: The plaque and calculus score was determined by Green-Vermillion's method; the degree of gingival inflammation was examined by a modification of Schour-Massler's method; the degree of alveolar bone loss was measured on X-ray photos by method of Schei et al.; and the depth of periodontal pockets was measured with a pocket maker. The periodontal condition was classified into four categories on the basis of clinical findings and X-ray photos as follows: simple gingivitis, slight periodontitis, moderate periodontitis and advanced periodontitis. Healthy dental students were selected as control subjects in this study.
The viscosity of whole saliva was measured by a cone-plate viscometer: immediately after collection the saliva was centrifuged for 10min. at 2, 000g, and 1.5ml of its supernatant was submitted for measurement of the viscosity at 4°C under the shear rate of 9.6sec^-1. Protein and sugar contents of the salivary mucin were measured by Lowry's and Anthron's methods, respectively.
The following results were obtained:
1. The salivary viscosity was found to be the highest between 31 and 40 years of age.
2. There was no significant difference in the viscosity between males and females.
3. Although the viscosity tended to be high at pH range from 6.5 to 7.0, there was no statistically significant correlation between the pH and the viscosity.
4. The salivary viscosity in patients suffering from periodontal diseases was higher than that of normal subjects, except those of simple gingivitis. Moreover, there was a significant increment of the viscosity with the progress of the disease.
5. The salivary mucin content was significantly higher than that of normal subjects and a statistically significant positive correlation was found between the viscosity and the salivary mucin content.
6. A statistically significant positive correlation was found between the salivary viscosity and the depth of periodontal pocket, and between the salivary viscosity and the degree of alveolar bone loss.
7. A statistically significant positive correlation was found between the protein content on one hand, and the calculus score, the depth of periodontal pocket, or the degree of alveolar bone loss on the other.
8. A statistically significant positive correlation was found between the sugar content on one hand, and the plaque score, the calculus score, or the degree of alveolar bone loss on the other.
It was concluded that the viscosity of the whole saliva is closely related to the salivary mucin content, various clinical findings and periodontal condition.