148 R. F. SOGNNAES 



separated from the tooth surface by a thin cuticular membrane, 

 which stains orthochromatically with tokiidine bhie, presumably 

 originates from sahva, and possibly may be of protective significance. 

 Tentatively, one may suggest that a three-stepped sequence of 

 events may be involved in the pathogenesis of "idiopathic" dental 

 erosion: (1) primary absence or secondary loss of some protective 

 salivary organic coating on the tooth surface; (2) drainage of min- 

 erals from the unprotected and, hence, more soluble peripheral tooth 

 substance by some decalcifying agent present in or brought into 

 contact with the oral environment; and ( 3 ) destruction of this super- 

 ficially decalcified tooth surface through biochemical and biophysical 

 influences or even simple mechanical friction by lip, cheek, tongue, 

 food, or toothbrush. 



Resorption 



On the basis of what has been learned from dento-alveolar resorp- 

 tion processes (Fig. 30E and F), one cannot point to the content 

 and distribution of cellular elements (Fig. 30d and e) or to any 

 consistent proportion of inorganic and organic ingredients to ac- 

 count for the origin of the multinucleated osteoclasts, on the one 

 hand, and the susceptibility to resorption on the other. It is sus- 

 pected, therefore, that changes in the environment adjacent to the 

 disintegrating surfaces must be explored for factors that induce the 

 virtually simultaneous removal of organic and inorganic elements of 

 these tissues in the process of resorption (Fig. 31). 



Postmortem Destruction 



Postmortem changes have been observed in human teeth of pre- 

 historic, ancient, and recent times originating from Palestine, Egypt, 

 Greece, Iceland, Norway, and Central America. The histological ob- 

 servations indicate that the commonest postmortem change consists 

 in large irregular boring canals which penetrate the dentin and 

 cementum, leaving sharply defined margins with no evidence of any 

 gradients in demineralization (Fig. 30G). The microscopic pattern 

 of the postmortem destruction is suggestive of an invasion by fungi 

 (Fig. 30f). Postmortem changes were rarely found in the enamel and 

 were limited to localized areas of erosion of the enamel surface. 



