Achieving a precise diagnosis of the pulp status of traumatized teeth is difficult. The time to interfere through endodontic treatment for these teeth is greatly dependent on the doctor's experience. A 24-year-old male patient suffered a traumatic injury to tooth #9 that resulted in an apical root horizontal fracture 3 days before he came to the hospital. The injured tooth showed no response to pulp sensitivity testing at the first visit and was discolored 1 week later. Tooth #9 was immobilized to its adjacent teeth for 4 weeks by a composite splint. The patient was asked to make regular follow-up appointments for 72 weeks. The changes in the pulp microcirculation of tooth #9 after the injury were recorded using laser Doppler flowmetry (LDF) and a tissue oxygen monitor (OXY). The LDF was used to directly measure the pulpal blood flow, and the OXY was used to detect the tissue oxygen saturation and total hemoglobin at each appointment. Tooth #9 survived a period of pulp infarct that started at week 4 and showed complete revascularization within 10 weeks. The color of the tooth returned to normal after revascularization. The tooth responded to sensitivity testing at week 58, and radiographic examinations confirmed its hard tissue was healing. Without other clinical signs besides tooth discoloration and an absence of response to pulp sensitivity testing, the complete self-repair of pulp can be expected in teeth with pulp infarct after a horizontal root fracture, and more than 1 year of follow-up is recommended. The use of LDF combined with OXY monitoring has great value in the timely and precise reflection of changes in pulp status after dental trauma.