抄録
It has generally been accepted that dental tartar may be found deposited upon every tooth, but friable, light-colored deposits collect primarily upon the buccal surfaces of the upper molars and the lingual surfaces of the lower incisors, i.e., opposite the exits of the ducts of the salivary glands. On the other respect, increased pH of saliva reduces so much solubility of calcium salts that calcium salt precipitates in saliva. Besides of escape of carbon dioxide from saliva1,2) and proteolysis by some oral bacteria, 3,4) as a factor of local alkalization, Frank 5) mentioned that higher content of free ammonia in saliva was in some relationship with those individuals having a greater tendency to form calculus and claimed that the slight decrease of ammonia content after restless removal of calculus showed that the existence was partially dependent on the ammonia content. The source of ammonia nitrogen in human saliva has been shown to be amino acids and urea.6) Dealing with the ammonia releasing systems in the mouth, Stephan7) reported on the substancial ureolytic action of plaque material and Bliss8) found that tartar
scraped from the teeth of normal and nephritic dogs contains urease which acts upon the urea in saliva to produce ammonia. Hine and O’Donnel9i made tests on salivary samples whose 92.8% showed some degree of ammonia production from urea and they suggested a possibility that presence of urease in the mouth would result in an alkaline reaction which might be favor for dental calculus deposition. Ureolytic bacteria were suspected to have some preferential habitation at the particular sites of the mouth where calculus often appear. Topographic difference, therefore, in respect of urease activity of bacterial plaque materials were traced in the present paper.
