CHAPTER VII 

 THE PERIODONTAL MEMBRANE 



THE periodontal membrane, alveolodental periosteum or 

 pericementum, surrounds the implanted part of the tooth 

 in man, intervening between the cement of the root and 

 the bone of the alveolus. It is derived from the connective 

 tissue of the tooth-sac or outer portion of the follicle, and 

 consists of connective-tissue fibres and cells with nerves and 

 blood-vessels, but no elastic tissue. 



It is held by Malassez (2) that the term alveolodental 

 periosteum commonly employed in describing this membrane 

 is ' as false from the physiological point of view as from the 

 anatomical '. He considers it shows none of the charac- 

 teristics of an enveloping membrane, but solid fibrous 

 fasciculi, which he considers form a kind of circular ligament. 

 He further says : * Reviewing the evidence of comparative 

 anatomy, we see that in many animals the teeth are not 

 enclosed in alveoli, but they are seen to be simply included 

 in the mucous membrane of the gum, but are also attached 

 to the maxilla by solid ligament ous fasciculi, the analogue 

 of the so-called alveolodental periosteum.' 



Ranvier l also stated that ' there exists between the tooth 

 and its alveolus no separable membrane such as is present 

 around the long bones ', and looks upon the alveolar cavity 

 as ' nothing but an enlarged medullary space, communicating 

 with neighbouring spaces '. 



The white fibrous connective-tissue bundles, of which this 

 membrane is chiefly composed, pass from tooth to bone in 

 a more or less transverse direction, and they become blended 

 with the tissue of the gum at the neck of the tooth. These 

 bundles are attached to the cement by strong fibrous bands 

 which pass into its substance (figs. 191, 193, and 199) as 

 Sharpey's fibres, and they penetrate the bone of the alveolus 

 in a similar manner. The direction of the connective-tissue 

 strands or bundles varies considerably in different parts. 

 1 Ranvier, Unpublished Lectures at the College of France. 



