Biologic aspects of endodontics: IV. Periapical tissue reactions to root-filled teeth whose canals had been instrumented short of their apices

Abstract

Pulp extirpations and root canal instrumentation shy of the apices of the teeth were performed on thirty-four human anterior teeth and on thirty-two roots of sixteen teeth of Macaca rhesus monkeys. The root canals were then filled short of the apices of twenty-four human teeth and twenty-two roots of eleven monkey teeth. Root canal fillings were purposely forced beyond the apices of nine human teeth and ten roots of five animal teeth. Observations were made of the periapical tissue reactions to those procedures after time intervals ranging from 6 to 270 days in the human groups and 14 days to 270 days in the animal series. Comparisons were made between the periapical tissue reactions of the two groups. Periapical tissue reactions were similar in both groups, initially. There was an acute inflammatory response in the apical pulp and periapical tissues, which was gradually superseded by chronic inflammation. Dentine filings were found to have been impacted on the remaining apical pulp stump in the group in which the canals had been filled shy of the apex. When the filling material had been pushed beyond the apex, the dentine debris and root canal filling materials were found in the periapical tissues. In both groups, periapical inflammation was accompanied by root end and alveolar bone resorption. Within 3 to 6 months, repair of the resorptions by secondary cementum and bone elaboration occurred routinely in most of the teeth. From 6 to 12 months later such repair was generally complete in the group in which the canals were filled shy of the apices. Repair was delayed in the group in which the canals had been overfilled. In addition, in this group there was a greater tendency toward proliferation of cell rests of Malassez. Foreign filling material in the periapical tissues tended to become encapsulated by collagen fibers. It was concluded that, in cases of vital pulp extirpation, optimum results, in terms of tissue repair, were obtained when root canals were instrumented and filled short of the apices of the teeth.