Hi, There is no such research, but what people write on Google is that if there is over obturated( failed RCT) it can cause repeated irritation to the tissue and may lead to cancerous lesion.   But a we'll did RCT will never cause any irritation because the material used to fill the root canal never come in contact with living tissue. So you don't need to worry. Hope the answer to your query. Regards Dr Muzaffer Hussain Parray.