DENTO-ALVEOLAR RESORPTION IN PERIODONTAL DISORDERS 290 



formation of alveolar bone ma^ be clue to three factors: inherited 

 characteristics, substances produced in the inflamed periodontal 

 tissues, and masticator\ functional impulses. 



The latter concept is based on the fact that weakening of the 

 alveolar bone as a result of resorption exposes the rest of it to in- 

 creased functional stress, or what is called hvperfunction. In all parts 

 of the skeleton, hvperfunction to a certain limit results in compensa- 

 tory bone apposition, provided that the bone tissue has a sufficient 

 supplv of hormones, xitamins, calcium salts, and other nutritional 

 elements necessary for bone production. In a growing organism 

 compensatory bone apposition and hereditary bone growth take 

 place at the same time. In this period heredity governs the gross 

 pattern of bone formation, while functional impulses modifv the 

 form and structure of the bones. 



The stimulating effect of mechanical functional impulses on bone 

 production was established bv Roux in 1895, and his findings have 

 been confirmed bv clinical observations and a series of experiments, 

 of which onlv those performed b\' Hiiupl and Psanskv ( 1938 ) and 

 by Watt and \Mlliams (1951) will be mentioned here. The former 

 authors observed that alveolar bone and connective tissue in the 

 pericementum had been produced in humans as a reaction to an 

 increase in masticatory functional stress for three nights by means 

 of activators (Fig. 6). Watt and Williams found that the size and 

 densitv of the mandible in growing and adult rats increased with 

 a rise in the masticatory functional stress. Both experiments support 

 the assumption that alveolar bone resorption is a trigger mechanism 

 which, subject to certain conditions, incites alveolar bone produc- 

 tion. 



Instead of any further comment on the different theories, the 

 problems pertinent to the loss of alveolar bone in periodontal dis- 

 orders will be discussed from the standpoint of (1) the relation 

 between circulatory disturbances in the periodontium and loss of 

 alveolar bone, (2) the effect of increased functional stress on the 

 alveolar bone, (3) the influence of periodontal and systemic condi- 

 tions on the loss of alveolar bone, and (4) the effect of periodontal 

 pathologv on resorption of the teeth themselves. 



