310 I. REICHBORN-KJENNERUD 



it nia\^ be assumed tliat tbev are due to increased functional stress. 

 Another finding sustaining this concept is the nearly constant ap- 

 pearance of pulp stones and the retraction of the crown pulps in the 

 front teeth in these cases. These reactions must result from circula- 

 tory disturbances in the apical part of the pericementum due to in- 

 creased moxements of the root tips during mastication, 



A clinical s\ mptom which verv often precedes and always follows 

 an alveolar bone resorption manifesting itself in an increased tooth 

 mobility is dullness by transversal percussion of the teeth. Histolog- 

 ical observations and experiments indicate that this symptom is due 

 to circulatory disturl:)ances in the pericementum ( Reichborn-Kjen- 

 nerud, 1956). Percussion "dullness" is a means of diagnosing an 

 increase in the functional stress above the physiological limit. 



It can be concluded that an increase in the masticatory functional 

 stress has the following effects. When it is raised to a certain limit 

 it stimulates a compensatory production of alveolar bone. If it in- 

 creases above this limit, this reaction does not occur, but pathological 

 changes appear, followed by destruction of alveolar bone. Functional 

 impulses of this type will thus impede the formation of alveolar bone 

 and incite destruction of it. 



The Influence of Periodontal and Systemic Conditions 

 ON THE Loss OF Alveolar Bone 



Because circulatory disturbances increasing the tissue tonus are 

 followed by bone resorption, all external periodontal conditions con- 

 tributing to the development of these changes in the periodontium 

 will promote destruction of alveolar bone. 



The internal anatomy and the physiology of the periodontium 

 and of all other organs will always influence the initiation and fur- 

 ther spread of disorders, and are very often responsible for the re- 

 lapse of diseases. 



The structure of the periodontium ma\' be more or less favorable 

 for the loss of alveolar bone. It is probable that the resistance of 

 east Greenland Eskimos and other peoples to loss of alveolar bone 

 is partly due to the anatomy of their periodontia. Anatomical con- 

 ditions having the opposite efl^ect are increased permeability and 



