The human tooth is divided into a crown, a neck and a root. The crown is divided into three parts: the outermost enamel, the middle dentin and the innermost pulp chamber. The oral side of the pulp chamber is called the top of the chamber and the root side of the chamber is called the bottom of the chamber. Generally when doing open pulp drainage or doing root canal treatment, the pulp is opened or the top of the pulp chamber is uncovered at the top of the pulp chamber. The bottom of the pulp chamber should never be destroyed during root canal treatment. If the pulp chamber floor is destroyed, it will cause root bifurcation lesions, recurrent inflammation, periodontal abscess, and even need to be extracted. So it must be distinguished.