Is it true that the sealer puff contributes to failure of root canal treatment ?? Possible reason for these findings are 1. The resorption of the root apex in established apical periodontitis cases means these cases have a higher failure rate due to the long standing disease rather than sealer which extrudes through the apex 2. Sealers are generally cytotoxic and can cause inflammation and slow healing 3. Over preparation may lead to a sealer puff and the over prep causes damage to apical tissue