FACTORS INFLUENCING DENTAL CARIES XiO 



have been misconstrued by Scliatz and Martin ( 1962 ) : "If decay 

 were due to acid, all the aforementioned organisms should have 

 been cariogenic since all are acidogenic." The reasoning here is open 

 to question because in the experimental hamster model not all acido- 

 genic organisms will colonize and produce plaques on enamel sur- 

 faces. The results of Fitzgerald and Keyes (1960) should not be 

 used to support the proteolvsis-chelation theorv. 



The discussion of streptococci b\' Burnett and Scherp ( 1962 ) is 

 quoted below because many obserxations on caries activity seem 

 to be in coincidence with what is known about this group of bac- 

 teria: 



The environmental and nutritional requirements of streptococci diflFer 

 widely among various strains and species, ranging from the most exacting 

 conditions to the abilitv to grow in a very adverse environment. The hu- 

 man pathogenic strains are generally more exacting in their environmental 

 and nutritional requirements than are the nonpathogenic strains. The 

 following essentials have been recognized: Carbohydrates — a readily 

 available source of carbohydrate is necessary for the growth of aerobic 

 streptococci, although it may not be essential for the growth of some 

 species of anaerobic streptococci. The amount of carbohydrate available 

 in media may be critical; if too much is available, sufficient acid is pro- 

 duced to inhibit or kill streptococci; if not enough is present, growth 

 does not occur. Carbon dioxide — a proper amount of carbon dioxide 

 (usually 5 per cent) favors growth and utilization of nutritive material 

 and may act, for instance, as a substitute for purines. Vitamins — some 

 water-soluble vitamins such as biotin, pantothenic and nicotinic acid, 

 thiamine, riboflavin, pyridoxal, and folic acid are essential for growth, 

 varying with the species. Purines, pyrimidines, and as yet undefined 

 growth-promoting substances, e.g., yeast or liver extracts, may enhance or 

 even be essential for the growth of the more fastidious streptococci, bi- 

 organic salts and buffers — although a balanced inorganic ion system is 

 needed for the growth of streptococci, their specific requirements have 

 not been adequately defined. Good buffers are necessary for the neutrali- 

 zation of acids produced during metabolism. 



Questions about the requirements for COi> and for inorganic salts 

 and buffers have been of interest to us. Is there a special need when 

 certain organisms have to deal with high loads of carbohydrates? 

 It seems reasonable to postulate that those organisms which have 

 invaded the tooth are surviving and probably finding a fa\orable 



