Epithelial proliferation in periapical lesions

Various endodontic procedures were performed on seventy-two teeth which had no periapical pathosis prior to endodontic treatment. From 6 to 360 days later the periapical tissues of these teeth were examined histologically. In eighteen such tissues (26 per cent), proliferation of cell rests of Malassez had occurred. The lowest incidence of epithelial growth appeared in cases in which the root canals had been instrumented short of the root apices of the teeth and then left unfilled (25 per cent) or filled short of the apices (17 per cent). The highest incidence of epithelial proliferation appeared in those cases in which the root canals were instrumented and filled beyond the apices of the teeth (46 per cent). Epithelium began to proliferate as early as 14 days after endodontic treatment. In six of fourteen lesions, there was evidence of entrapment and degeneration of epithelial strands in newly formed collagen fibers. Twenty-two teeth in which periapical lesions were present prior to endodontic therapy were examined histologically. In five of these teeth no endodontic therapy had been undertaken, and in seventeen teeth endodontic therapy had been performed 10 to 220 days prior to root resection. Epithelial proliferation was found in ten of the twenty-two lesions. Studies of the epithelium in seven specimens 56 to 220 days after endodontic therapy had been performed revealed that the epithelium was degenerating in three lesions. In four lesions no degenerative epithelium changes could be discerned.