Strip Perforation of the Danger Zone in Mandibular Molars: A Case Report and Literature Review

Background The danger zone (DZ) commonly refers to the area of mesial roots in mandibular molars, which is more vulnerable to perforations in cases of over-instrumentation. Midroot perforations may lead to a dubious prognosis and ultimately to tooth extraction. In clinical practice, identifying the danger zone and preventing perforation are extremely crucial. However, there are no articles that systematically summarize relevant studies since the concept was first introduced in the 1980s. Case presentation This report describes a failed root canal treatment because of a stripe perforation during preparation. In our hospital, a female patient underwent root canal treatment on her mandibular first molar. After the standard procedure of root canal preparation, the pathological condition of the tooth worsens. A CBCT showed a transmissive shadow at the root bifurcation and partial loss of dentin in the proximal mesio-buccal root. This tooth was eventually recommended for extraction. Conclusions Each clinical case must be analyzed carefully and individually before endodontic procedures to minimize the occurrence of iatrogenic perforations. In addition, this report provides a comprehensive review of research advances related to the danger zone (DZ) and summarizes the characteristics of the DZ. The risk factors associated with streak perforation events, such as instrument selection and anatomical factors, are also explored in detail. Through a comprehensive analysis of these research advances and risk factors, we can better understand characteristics and potential risks of the DZ to guide endodontic treatment decisions in clinical practice to improve the success rate and prognostic quality of treatment.