Research progress of smear layer of root canal

Smear layer of root canal refers to a polluted layer which is generated and adhered to the root canal wall, and even partly penetrated into dentinal tubule in the process of clearing root canal by preparation instrument and forming root canal on treating it caused by endodontic disease. It plays significant roles in the success of root canal therapy and postoperative long-term effect. it is unable to be eliminated by ordinary flushing fluids like saline, distilled water, but can be cleared away by special washing fluids, like sodium hypochlorite solution, etc. Nowadays, in clinic it inevitably emerges no matter hand instrument or rotary instrument is applied for root canal cleaning or root canal has been formed. However, improvement of root canal preparation methods can reduce the emergence of smear layer. After reviewing relevant literatures, the article is going to summarize research progress of the smear layer of root canal in the aspects of its generating process, significance, and removal measures.