NEW CEMENTUM FORMATION INDUCED BY CYCLOSPORINE-A - A HISTOLOGICAL, ULTRASTRUCTURAL AND HISTOMORPHOMETRIC STUDY IN THE RAT

Cyclosporin A (CsA), a widely used immunosuppressive agent, is known t o induce gingival overgrowth; 30 mg/kg/d of CsA were administrated ora lly in young and adult male Sprague-Dawley rats. The same number of ra ts received oil-based vehicle solution. After 4, 9, 14 and 19 wk of Cs A or vehicle administration 3 control and 3 experimental rats were ana esthetized and tissues fixed by an intracardiac perfusion of fixative solution. Upper and lower jaws were dissected, demineralized and proce ssed for Epon inclusion. Histological examination revealed the presenc e of large amounts of new cementum (NC) covering extensive areas of th e acellular extrinsic fibre cementum (AEFC) in all the root surfaces. NC was particularly abundant at the cervical third of the roots facing the gingival connective tissue, where it occurred as layers, spurs or in both configurations. NC was characterized by its irregular outline , globular body content and infrequent presence of incremental lines. Histomorphometric evaluation by semi-automatic image analysis indicate d that the volume and the external surface of NC spurs were 2.86-6.49 and 1.29-1.97-fold increased comparative to those of the AEFC covering the same root areas. Electron microscopy revealed that NC was a funct ional tissue with insertion of collagen fibres perpendicularly to the long axis of the root. It can be concluded that under some experimenta l conditions formation of abundant amounts of NC can be achieved and t hat these results must be taken into account for a new approach in the treatment of periodontal disease.