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Significant positive correlations between protease activities in saliva and supragingival/subgingival calculus indices, periodontal pocket depth, or P-M-A index were confirmed. When the partial correlation was calculated, the subgingival calculus index correlated well with the sediment protease at pH 8.5, and the supragingival calculus index showed a significant correlation with the supernate protease at pH 4.5.

Some investigators' 2 have felt that there is no difference between supragingival and subgingival calculus either in composition or in mineralizing source. Others3' 4 have expressed the opinion that supragingival calculus is formed from saliva but that subgingival calculus is formed from tissue fluid in the gingival crevice. Studies on the fluid outflow from the gingival crevice58 have seemed to add support to the latter theory. These various ideas remain to be proven. Since the composition of supragingival calculus9 has been found to depend on the location in the mouth and the extent of the calculus produced in a subject, it is of interest to obtain similar information on subgingival calculus. A problem arises in studying dental calculus. One must be able to determine with some degree of certitude that a collected specimen is either supraor subgingival. In this study an attempt was made to do so.