114 R. F. SOGNNAES 



The most significant single endea\or to test quantitatively and 

 directly the general environment of the mouth in patients with 

 erosion, as compared with controls, is a study by Zipkin and Mc- 

 Clure (1949). They examined salivary citrate in 121 adult patients, 

 60 of whom had dental erosion. Statistical analysis of their data 

 indicated a significant positive correlation between the presence of 

 dental erosion and an elevated citrate content of the saliva. Both 

 the citrate content of the saliva and the incidence and extent of 

 erosion proved to be highest in the older age group, namelv, above 

 40 years of age. 



In apparent conflict with this observation is the studv bv Shulman 

 and Robinson ( 1948 ) , in which they found no difference in sal- 

 ivary citrate content between 15 freshman dental students who 

 had dental erosion and 25 controls. This finding might appear to 

 suggest that salivary citrate and erosion may increase independ- 

 ently of each other with increasing age, the two facts being coin- 

 cidental rather than etiologically related. Young students, however, 

 would be less likely to suffer from typical erosion, and the salivary 

 citrate was increasing not merely with age, but with erosion and 

 age. Theoretically citrate could serve as a calcium-sequestering 

 agent ( see chapter 25 by Jenkins and Dawes ) . 



The possible implication of such a chelation influence in erosion 

 is not new. As early as the 1880's it was postulated by Kirk ( 1887 ) 

 that some agent in the mucous glands situated along the buccal and 

 lip mucosa may be responsible for erosion. The idea was also ex- 

 pressed that this mucous secretion may be produced on a more con- 

 tinuous basis during the night — more so than the buffered secretion 

 from the larger parotid glands. On the basis of some very limited 

 observations, Badanes (1930) reported that oxalate tended to accu- 

 mulate from the mucosa, especially on that side of the mouth op- 

 posite to the side upon which the person slept. 



More recently there have appeared a few additional in vivo and 

 in vitro observations with reference to certain calcium-binding 

 agents. For example, Ericsson in Sweden ( 1953 ) examined the 

 citrate level in the saliva after short periods up to 20 minutes after 

 ingestion of orange juice and grapefruit. As might be expected, the 

 citrate level rose sharply within the first couple of minutes, but 



