FACTORS INFLUENCING DKNTAL CARIES 



263 



Fig. 1. Three overlapping circles depict the possible relationships of the 

 factorial groups responsible for caries activity. There are numerous variables in 

 each parameter. When the infection is active, conditions in each are conducive; 

 but when it is inactixe, to know which of the groups is in a noncontributory 

 status is exceedingl\- difficult and often impossible. 



Despite the prevalence of caries in human populations, we might 

 also expect to find that rather specific conditions are necessary for 

 activity. It follows, therefore, that in order to establish the caries- 

 inactive host as immune or resistant, one must be sure about which 

 factors are in a noncontributory status; such definition has rarely, if 

 ever, been attained with certainty. 



Many experiments in the field of dental caries have not been con- 

 trolled in terms of the single-factor variable described in their de- 

 sign, and as a result such studies are open to various interpretations 

 in terms of mechanisms responsible for the results. As suggested 

 above, the limiting factor is obviouslv in the biological complexities 

 of the disease itself rather than in the experimental design as it 

 has been conceived in the mind of the investigator. "In view of the 

 high number of multiple pathways possible for most biological 

 processes, and in view of the randomness of manv of the biologi- 

 cal processes, particularly on the molecular level, causality in 

 biological systems is at best onlv statistically predictive" (Mayr, 

 1961). 



