A COMPARISON OF THE SALIVARY PROTEASE ACTIVITY IN THE HARVARD AND HUNT-HOPPERT CARIES-RESISTANT AND CARIES-SUSCEPTIBLE RATS

¹ Harvard School of Dental Medicine, Boston, Mass.

1. Under our laboratory conditions, as in the laboratories at Michigan State University, the rats of the Hunt-Hoppert caries-susceptible strain demonstrated strikingly higher protease activity levels in saliva than did the rats of the Hunt-Hoppert caries-resistant strain. This ratio was consistent when ration 700 + 15 per cent Cellu flour was fed instead of the Hoppert-Webber-Canniff diet, and also when the rats of the Hunt-Hoppert caries-resistant strain developed extensive carious lesions.

2. In contrast, rats of the Harvard caries-susceptible and caries-resistant strains exhibited low protease activity levels in the saliva with no significant difference between the caries-susceptible and caries-resistant animals.

3. In view of the above findings, it would appear that the tendency toward high salivary protease levels in the caries-susceptible Hunt-Hoppert animals is a genetically determined trait that has appeared simultaneously with the tendency toward high caries-susceptibility. On the same basis, it would also be suspected that salivary protease activity, per se, is not directly related to dental caries.