“…Dawes and Jenkins [1962] suggested that the low sus ceptibility of the lower incisor teeth to ca ries was related to the higher calcium and phosphorus concentration observed in plaque from this area, compared with plaque from other areas of the mouth. In several later studies, with more standar dised recording methods, when the total caries activity of the mouth was assessed and subjects were divided into those show ing either high caries activity or low caries activity, significant inverse relationships were found between caries experience and plaque calcium or phosphorus levels [Kleinherg et al, 1969;Ashley, 1972Ashley, , 1975Schamschula et al, 1977], In most studies, the DMF index has been used as a measure of caries experi ence, but caries progression is discontinu ous and hence a carious lesion or filling is an indication of past events and not neces sarily of current caries activity. In the study reported by Luoma [1964], the sub jects were divided on the basis of DMF and caries increment over a 1-year period.…”