Research content: select the patients with accidental pulp exposure or decayed pulp exposure in the pediatric dentistry department of The Affiliated Stomatology Hospital of Zhejiang University School of Medicine from February 2022 to October 2022.

1. Strictly implement the case selection criteria to reduce the deviation. 2. Conduct uniform training and assessment for doctors. 3. Record in detail: the age, gender, tooth position, cavity type, x-Ray examination, size and reason of pulp exposure, time of hemostasis, filling material, signs and symptoms of initial consultation and follow-up, etc. 4. Analyze the clinical data to study the success rate of direct pulp capping of primary teeth; analyze the influence of various factors to study how to improve the success rate of direct pulp capping of primary teeth.

Inclusion Criteria:

• No irreversible signs or symptoms of pulpitis in the affected tooth.
• Mechanical pulp exposure caused by cavity preparation or trauma, or pulp exposure after decayed tissue removal, with healthy dentin around the pulp exposure.
• The size of the exposed pulp<1 mm.
• The morphology of pulp tissue at the pulp exposure is normal, and the bleeding should be able to be controlled within 5 minutes.
• X-ray showed that there was no abnormal resorption or fracture of the root and no lesions around the root.

Exclusion Criteria:

• The child is unable to cooperate with the treatment.
• Pulp exposure > 1 mm.
• Irreversible signs or symptoms of pulpitis in the affected tooth.
• Abnormal morphology of the pulp tissue at the pulp exposure, much bleeding and inability to stop bleeding.
• X-ray shows: abnormal resorption or fracture of the tooth root and lesions around the root.
• The parents or the child refused to participate in the experiment.