To study the effects of over-instrumentation and overfilling on the results of the re-treatments performed in a previous study.
- 344 patients (556 roots) underwent endodontic retreatment during 2 years.
- the reason for retreatment was either technically incomplete root filling without PA lesion (technical group), or PA lesion present radiographically (osteitis group).
- retreatment procedures were done by students under supervision, the procedures were described in details,
- New root filling was made by using gutta-percha and resin in chloroform as an adhesive in the canal, according to the multi-cone technique.
- treatment factors including: overinstrumentation through the apex or if complete mechanical cleansing of the root canal was impossible to perform were recorded.
- Within 2 years, the cases were followed up, clinical and radiographical examinations done.
- Overfills were registered through radiographs taken before, during, and after re-treatment. Also recorded, was the status of periapical area (whether the original PA lesion had healed completely, was reduced in size, was unchanged, or had increased in size).
- In cases with original PA lesions and no overfilling, 62% of the lesions healed, and 22% reduced in size.
- the rate of healing of PA significantly reduced in cases of overfilling (36%) and in cases where the canals were cleaned through the apex (over instrumentation): 41%.
To create favorable healing conditions when re-treating endodontic cases, a combination of
over-instrumentation and overfilling should be avoided.