A study of epithelial odontogenic residues in the pig.

Formation of the junctional epithelium was studied by routine light microscopy in the molar teeth of commercially slaughtered pigs. It was found that the process whereby the reduced enamel epithelium (REE) contributed to the junctional epithelium formation corresponded largely with changes in man previously described by Schroeder and Listgarten (Monographs in Developmental Biology, Vol. II, Basel, S. Karger, 1971). The configuration of the marginal rests of Malassez (ROM) and their relationship to the junctional epithelium and REE was similarly studied by means of true serial sections. It was found that the ROM in that portion of the periodontium below the alveolar crest formed a well defined network of epithelial strands, but the network became more poorly defined and diverged away from the surface of the cementum as the cementoenamel junction was approached. The coronal border of this network ultimately became continuous with the REE by means of a relatively few vertical strands of epithelium. The possibility that the presence of epithelial residues in the periodontium may contribute to pocket formation and the potential effects of its configuration and continuity with the junctional epithelium are speculatively considered.

The rests of Malassez and chronic marginal periodontitis.

The structure of the rests of Malassez and the relationship which they bear to the junctional epithelium in the marginal region of pigs' molars was investigated. A 3-dimensional picture of the marginal rests and their relationship to the junctional epithelium was built up by means of standardized photomicrographs made from serial sections. In teeth involved in chronic marginal inflammation, the rests in this region appeared to form a continuous network and we confirmed the original suggestion of Grant & Bernick that, at frequent intervals, the junctional epithelium"... seemed to be continuous with the epithelial rests in the upper third of the root...". If the anatomical relationship of the rests in man resembles that seen in the pig and they form a continuous network communicating at intervals with the junctional epithelium, this relationship must inevitably lead to speculation about the effects of any potential for reactive proliferative equivalent to that which is frequently seen in the apical region. It is possible that the rests might be acting as the "thin end of the wedge", augmenting and facilitating apical migration of the junctional epithelium during the pathogenesis of the periodontal pocket.

A method of schematic three-dimensional reconstruction for studying the gross morphology of epithelial residues in periodontal ligament.

A series of standardized black and white composite photomicrographs of serial sections at X 160 magnification were placed side by side to a straight reference line through the cementum margins. The distances of various parts of the epithelial rest system from the reference line were measured and from the measurements a bar graph was constructed which provided a 3-dimensional representation of the overall configuration of the marginally-sited rests and their relationship to the junctional epithelium. The epithelial residues formed a continuous network the coronal border of which was in intermittent direct continuity with the junctional epithelium. However, to what extent this was affected by the mild chronic inflammation present could not be assessed.

A new look at the rests of Malassez. A review of their embryological origin, anatomy, and possible role in periodontal health and disease.

The embryological formation and anatomy of the rests of Malassez are described and their possible roles of health and disease are discussed. It is emphasized that the rests are worthy of new interest and further study. They comprise a structure whose precise anatomy still is in need of accurate description and in which the presence or absence of a physiological role is unproven.