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CALCIFIC CHANGES IN THE PULP. 417

symbol with red ink, to prevent the unnecessary removal of temporary
fillings and to explain the reason for their presence and thus avoid the
accident of unnecessarily uncovering the pulp in such cases.

Oalcific Changes in the Pulp as related to the Operation
OF Pulp Capping.

When loss of substance takes place slowly, either by carious action
or by attrition, a notable calcific growth takes place in the pulp cham-
ber opposite to the point of waste in the direction of the radiant course

Fig. 394.

Secondary dentin, resulting from irritation of the dentinal fibrils by caries (Black). A, Diagram
of an incisor having a decay in the hibial surface, a, and a deposit of secondary dentin at b.
The point from which tlie illustration B is talien is shown by c. B, Illustration of the tissue
of the secondary deposit in A : a, primary dentin : h, secondary dentin : c, seems to be a blood-
vessel that has become calcified ; d, an irregular fault having some resemblance to the laeunse
of bone ; e, pulp chamber. It will be noted that there are irregular deposits of granular matter
in the substance of the secondary dentin, and that the tubules wind about them.
of the tubules (see Fig. 394). If the loss of substance from the ex-
terior progresses with sufficient slowness encroachment upon the pulp
does not take place. The pulp chamber may become obliterated by the
progressive deposition of calcific matter, which has the designation of
secondary dentin.
The morphological character of the secondary deposit is histologically
irregular, being frequently of mixed character, presenting some of the
characteristics of dentin and also containing cemental cells with radiant
and anastomosing canaliculi. For this reason deposits have been
designated as osteo-dentin.
In the earlier years of life opportunity does not offer to study these
changes of structure, as the usual progress of caries is too rapid, but in
advanced life they are common, it being not infrequent to find complete
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