ATYPICAL APICAL LESIONS DETECTED DURING A STUDY OF SHORT-TERM TISSUE RESPONSES TO 3 DIFFERENT ENDODONTIC INSTRUMENTATION TECHNIQUES

An investigation is in progress using the beagle dog to investigate th e short-term responses of the supporting tissues to different methods of root canal preparation. Atypical apical lesions have been observed in 4/27 teeth examined 7-14. days after instrumentation. These lesions were related to the apical foramina and were characterized by total c ellular destruction. The centres of the lesions had densely staining m aterial which appeared to be either damaged collagen or nuclear fragme nts. PMNLs were present at the periphery. The exact aetiology of these lesions is uncertain at present. The possibility of a previously unre ported tissue reaction to sodium hypochlorite is being investigated fu rther.