THE TEETH. - 663 



(2) Inflammation of the pericementum is either a plastic (formative) or sup- 

 purative (destructive) process. These two kinds differ from each other only in 

 degree and intensity. 



(3) Plastic pericementitis is characterized l)y the formation of nests of inflam- 

 matory elements, arisen from medullary elements which have appeared from the 

 connective tissue after dissolution of its basis-substance. 



(4) Plastic per icementitis may terminate in resolution, if the inflammatory 

 elements he not numerous, and the basis-substance be reestablished ; or it leads to 

 hyperplasia of the connective tissue, if a large number of inflammatory elements 

 have formed and the inflammatory process has repeatedly recurred. 



(5) Per icementitis in its more intense degrees is always accompanied by 

 cementitis of the root of the tooth, and by osteitis of the wall of the alveolus. 

 Plastic pericementitis leads to a new formation of cementum, as well as of bone- 

 exostosis. 



(6) Suppurative pericementitis results from the breaking apart of the inflam- 

 matory corpuscles which have arisen from the connective tissue of the pericementum 

 itself. Emigrated colorless blood-corpuscles probably share in the formation of 

 pus-corpuscles ; but no proof thereof is possible. The main mass of pus-corpuscles 

 is due to a transformation and destruction of the inflamed tissue. 



CARIES. BY FRANK ABBOTT, M. D.* 



Methods. The results recently obtained with regard to the minute structure 

 of the teeth have "been arrived at by new methods. As a matter of course, 

 dried specimens of teeth, formerly almost exclusively in use, did not reveal 

 any of the soft parts within the hard dental tissues. Only a frame of the tissue 

 was left, and we may readily understand why the investigations of the carious 

 process as yet have not passed above hypotheses and speculations. 



For preparing dentine and cement, there is no better method known than 

 slow decalcification by means of a one per cent, solution of chromic acid. The 

 enamel of teeth prepared in the foregoing manner can never be cut, because 

 it becomes extremely brittle ; therefore, I was obliged to resort for its exami- 

 nation to the method first practiced by Dr. Bodecker. The thin slices should 

 be kept for decalcification, for twenty-four hours, in a very dilute solution of 

 chromic acid. A saturation of this solution of over one-half of one per cent. , 

 in my opinion, is deleterious to the enamel, which, if completely decalcified, 

 shows only a minute net-work of living matter, as I first have observed, but no 

 trace of the enamel-rods and prisms. 



Caries of Enamel, t The clinical phenomenon of caries, in its very origin, 

 consists essentially in a discoloration of the enamel. A whitish or grayish 

 spot on the surface of the enamel is indicative, to an experienced eye, of the 

 beginning of decay, which spot proves, when touched with an instrument, to 

 be soft and crumbly. Often a brown spot is visible on the enamel as a sign 

 of the softening process. The less pigmentation present, the more rapid 

 is the process of decay. On the contrary, the more distinct the discol- 



* Abstract from the author's essay, " Caries of Human Teeth." The Dental Cosmos, Phil- 

 adelphia, 1878 and 1879. 



t The fact that caries of the teeth begins as a chemical process scarcely will, in my opin- 

 ion, be questioned. On a dead tooth, natural or artificial, as well as on teeth manufactured 

 from the dentine of the elephant or the hippopotamus, the process will remain, under all cir- 

 cumstances, a chemical ono. assisted only by the putrefying remains of the organic material 

 of the tooth ; while on a live tooth either acute or chronic reaction-changes take place. 



