304 MICROSCOPIC ANATOMY OF THE TEETH 



evidenced by the fact that alternations of removal and 

 deposition of tissue are often seen in these teeth during the 

 process of absorption, and this is also evident in the absorp- 

 tion of the roots of permanent teeth. As previously stated, 

 osteoblasts and osteoclasts appear to be interchangeable, 

 the same cells sometimes performing one function, some- 

 times another ; the multinucleated osteoclasts being simply 

 modified osteoblasts. 



In a recent paper (8) Dr. Eugene Talbot says : ' When 

 once the absorption of cementum has occurred, it is rarely if 

 ever reproduced.' The tissue which fills up the absorbed 

 areas in many teeth which have undergone chronic absorp- 

 tion certainly appears to be an irregular deposit of cement, 

 which in many of the author's specimens is laminated. 



Black also says : ' These absorptions ... are afterwards 

 repaired by the deposits of cementum, and the lamellae 

 of cementum subsequently la-id down are seen to pass over 

 them without any material disturbance.' (1). 



One would imagine that in the very recent absorptions 

 produced in Talbot's experiments on dogs sufficient time 

 had not been allowed for the process of re -deposition to take 

 place. 



REFERENCES 



1. Black, G. V. The Periosteum and Peridental Membrane. 



2. v. Brunn, A. See references to Chapter VIII. 



3. Choquet, J. (a) ' Notes sur les rapports anatomiques entre I'Email et 



le Cement.' UOdontologie, Feb. 1899. 



(6) ' fitudes sur la resorption des racines des dents temporaires,' &c. 

 Trans. Fifth Int. Dent. Congress, Berlin, 1910. 



4. Hopewell Smith, A. Normal and Pathological Histology of the Teeth, 



1919, p. 84. 



5. Kassander. Anat. Anzeig., 18, 1900. 



6. Robin et Magitot. Genese et developpement des follicules dentaires.' 



Journ. de I 'Anat. et de la Physiol., vol. iv, 1861. 



7. Schafer, E. A. Microscopic Anatomy, 1912, p. 148. 



8. Talbot, Eugene. ' Bone Absorption around the Roots of Teeth.' 



Dental Cosmos, May 1919. 



9. Waldeyer. Archiv f. Milcr. Anat., i. 1865. 



10. Woodhead, G. Sims. Practical Pathology, Edin., 1892, p. 474. 



