the 3:1 ratios of s : d , , s : f , x : d , and x : f caused slight lowerings to plaque ph means of 6.3 , 6.8 , 6.7 , and 6.7 , respectively , while 3:1 s : u caused the ph to drop to 5.6 .
C0016327
f
C0011389
plaque