DENTAL HARD TISSUE DESTRUCTION 129 



canals. Second, it has been noted that the regions bordering on 

 cracks in the teeth are favorable sites for the invaders. Such cracks 

 are most likely to have occurred some time after burial, owing to a 

 drying-out process. Another favored site for the spreading of the 

 canals is the junction between cementum and dentin and also the 

 dentin near the dentoenamel junction. Here, again, the drying-out 

 process would cause tension owing to the difference in coefficient 

 of expansion between the two structures. This drying-out process 

 would be expected to take some time, a fact which is in keeping with 

 the greater frequency of the postmortem canals in the older teeth 

 obtained from one and the same geographic region. 



The agents responsible for the pattern of the postmortem destiiic- 

 tion of the dentin and cementum, as observed at the microscopic 

 level, have not been definitely established. A few specimens ap- 

 peared to contain highly refractile thread forms within some of the 

 canals, but these may have been artifacts caused by the drying-out 

 process of larger organisms. Many of the canals were very similar 

 to those thought to be caused by the invasion of fungi, as suggested 

 by the early observations of Wedl, whereas Werner (1937) sus- 

 pected algae and worms as being capable of causing similar canals. 

 The fact that the canals vary in width and extent of penetration 

 would, however, not necessarily mean that different types of organ- 

 isms are involved, because their pattern may well depend upon the 

 conditions met along the way, which may allow for periodic lateral 

 action instead of foi-ward penetration. The secondary infiltration of 

 minerals noted in some of our dental specimens may be similar to 

 that observed in old exhumed bone and attributed largely to deposi- 

 tion of calcium carbonate. 



Various agents may be responsible for the surface destruction 

 which was observed in the cementum and which represented the 

 only significant postmortem change in the enamel. The fact that the 

 enamel, which is the most exposed and the most acid-soluble part of 

 the teeth, was usually less affected than the cementum suggests that 

 the erosions are not due to a generally acid environment entirely 

 surrounding the jaws and teeth, but must be due to destructive 

 agents localized at certain regions of the teeth. 



These erosions do not have the appearance of caries except when 



