Purpose: to evaluate the effect of over-instrumentation followed by underextended and overextended root canal filling on the periapical tissues on a histological level
N = 19 maxillary anterior human teeth, 15 roots of posterior monkey teeth •All teeth responded normally to vitalometry test. Pulp extirpation done, pulp tissue prepared for histological examination
•Teeth were over-instrumented beyond apical foramen from 2 – 10 mm •Nine human teeth and nine monkey teeth canals were obturated and material forced beyond the apex. The remaing sample (10 human and 6 monkey teeth roots) obturation was kept short of the apical foramina
•All teeth were extracted, resected and prepared with the bone surrounding the apical area with difference in time of sample prepared: underfilled 12-365 days overfilled 7-180 days.
Most highlighted Results:
•Over different observation periods, all samples showed signs of periapical inflammatory response
•Underfilled group: inflammatory reaction subsided after 3 months and regeneration took place
•Overfilled group: persistent chronic inflammation and kept enlarging in size. Greater tendency toward epithelial proliferation and cyst formation. No evidence of repair.
Overfilling and extrusion of obturation material and dentin chips beyond the apical foramen induced an inflammatory reaction. Underfilling showed that reactions subsided within 3 months and repair occurred eventually.
Underfilling is better than overfilling.