Purpose: to determine the immediate treatment result and incidence of flare-ups after retreatment of teeth with resorcinol-formaldehyde (RF) resin fillings.
N= 58 cases of retreatment of root filled with RF resin material
Materials/Methods:
•Records of 34 patients with 58 teeth that were filled with RF and retreated in a postgraduate endodontic clinic were reviewed.
•Reason for retreatment (symptoms versus restorative) and occurrence of flare-ups (pain or swelling requiring an emergency visit) and the periapical status before retreatment were recorded.
•Radiographs were taken for initial (resin obturations) and posttreatment (gutta-percha obturations) evaluations were used.
•Before & after retreatment, the length of obturated canal was measured by starting at the coronal orifice and measuring to the apical-most extent of the filling. The length of unobturated canal(s) was measured from the apical-most extent of the filling to a point 1-mm from the radiographic apex of the root. The % of the filled canal space was calculated.
•After retreatment quality of obturation was rated as optimal if 100% of the canals were filled, improved if the percentage of canals filled was increased by at least 10%, unchanged if the increase in percentage of canals filled was <10%, and worse if an iatrogenic perforation or separated instrument occurred.

Most highlighted Results:
- 48% of the total canal space was filled before retreatment; 90% was filled after retreatment.
- After retreatment, obturations were rated as optimal in 59%, improved in 33%, unchanged in 6%, and worse in 2%.
- 12% had post-retreatment flare-ups.
- No statistical relations was found between the incidence of flare-ups and the quality of obturation before or after retreatment (in terms of length) or the presence of symptoms or PA lesions before retreatment.
Clinical significance:
Studies with larger sample size are needed to determine the variables related to flare up.
