>-2()'-2 p. II. KEYES AND II. V. JORDAN 



the mechanisms of carbohvdrate degradation and associated phos- 

 phorylation. It seems reasonable to expect that tlie exploration of 

 some of the non-acidogenic aspects of the disease might lead to in- 

 formation of \'alue in strengthening a program of comprehensive 

 therapeutic control. 



Students of dental caries recognize that in addition to salivary 

 components, the highly variable nature of such di\'erse substrates as 

 food residues and mineralized tissue makes the disease more complex 

 to study than many other infections in which the intra- and extra- 

 cellular components of the tissues furnish the principal substi'ate for 

 the invading organisms. Some of the experimental findings to be 

 discussed lend support to the idea that colonization and invasion of 

 the cariogenic flora may be related to properties of the enamel and 

 dentin which the pathogens find beneficial to their life cvcle. 



Etiological Factors 



There is no single cause of caries, it is a multifactorial disease as 

 are other infections. Etiolog\' can be considered in terms of con- 

 tributing factors in the host, the oral microbiota, and the dietarv 

 substrate. It is possible to gain a broader perspective on the disease 

 processes in caries bv considering somewhat analogous interactions 

 between host, microbe, and over-all environment in other experi- 

 mental infections, e.g. tuberculosis (Ratcliffe et ah, 1953, 1957). 

 Additional insight into the complexities of biological interactions 

 and into their analysis can be gained from the discourse "Cause and 

 Effect in Biology" ( MaM", 1961 ) . 



In Fig. 1, three overlapping circles have been used to depict the 

 possible relationships in the factorial triad contributing to caries 

 activity, i.e. the host, the microbiota, and the diet. When the disease 

 is active, these three sets of factors are in concentricitv. Investigators 

 are becoming increasingly aware that each one of these components 

 behaves in a dynamic and variable wa\' and that under laborator\' 

 conditions only the most delicate balance of the three will induce 

 the disease and favor its progression. However, the magnitude of 

 each contributing factor is still difficult to identify positively and is 

 rarely amenable to control bv conventional experimental methods. 



