The efficacy of Vitapex paste in single-visit root canal treatment for chronic periapical sinus is reported as follows with satisfactory results: 1 Materials and Methods 1.1 Clinical Data - 56 cases of patients with chronic periapical inflammation, involving 58 teeth, aged 16-56 years. Among them, there were 21 anterior teeth, 19 premolars, and 18 molars. Before treatment, patients had a history of varying degrees of tenderness, recurrent teeth with apical gingival sinus discharging purulent secretions, percussion pain. X-ray dental films showed varying degrees of bone mass destruction in the periapical area. 1.2 Materials - 3% hydrogen peroxide, Vitapex root canal filling paste (Japan Morita Co., Ltd.), gutta-percha. 1.3 Treatment - Preoperative radiography was conducted to assess periapical tissue damage, the number of root canals, their length, curvature, and periodontal support structure. Teeth were routinely opened, pulp removed, and root canals expanded up to the apical foramen. The maximum size used was 35-40, eliminating bacteria or necrotic tissue within the root canal. A small curette was used to scrape the sinus, ensuring its patency. The root canal and sinus were repeatedly and alternately flushed with 3% hydrogen peroxide and normal saline. Cotton pledgets were used to suction the root canal, disinfect it, and measure the filling length. Vitapex paste was injected into the root canal up to the apical one-third under even pressure, gently driving the paste to fill the root canal and sinus until the paste overflowed from the sinus opening. Gutta-percha was inserted into the root canal lengthwise, without overfilling, followed by routine restoration of dental defects. 1.4 Efficacy Standards - No symptoms in patients, clinical examination showing no gingival swelling, percussion pain, healed sinus. X-ray film showed complete root canal filling, disappearance or shrinkage of apical shadow. If the paste has been absorbed after super-fill, it was considered successful. Failure - After treatment, obvious discomfort or pain, swelling, sinus not closed, still with purulent discharge. X-ray showed apical shadow extended or unchanged. One week after treatment, no symptoms were observed in 54 cases, accounting for 93.1%, due to more paste absorption leading to prolonged sinus non-healing. Six months review showed success in 51 cases, failed in seven, success rate of 87.9%. Failures were attributed to incomplete root canal filling, expansion of apical shadow, and non-healing sinus. The occurrence of chronic periapical disease is closely related to infected root canal microorganisms. Infected root canal microorganisms are often mixed infections, with obligate anaerobes being dominant bacteria within the root canal and periapical lesions, including Bacteroides, Fusobacterium, Peptostreptococcus, Eubacterium, Campylobacter, and Actinomyces. Vitapex paste's main ingredients are calcium hydroxide, iodoform, and polysiloxane oil. Calcium hydroxide, as a strong alkaline substance, has a pH value of up to 12.3, neutralizing acid and reducing inflammation and pain. Its antibacterial effect is achieved through the release of OH-, altering the bacterial envelope structure for an antibacterial effect. Calcium hydroxide also has non-sensitizing, converging, and non-stimulating advantages for periapical tissues; iodoform provides good corrosion protection, foul removal, and reduces exudate. In contact with tissue fluid, purulent exudate fatty substances or bacterial products, iodoform slowly decomposes free iodine, resulting in a bactericidal effect. Iodoform is non-irritating to tissues, promoting the convergence, absorption of apical lesions, growth of healthy granulation tissue, and healing of periapical lesions. Polysiloxane oil is water-resistant, insulated, preventing the absorption of the paste in the root canal; sinus filled with Vitapex paste gradually heals, absorbing and calcifying. Therefore, Vitapex paste filling the root canal and sinus has persistent antibacterial properties, effectively suppressing residual bacteria within the root canal and sinus, preventing reinfection, while its strong tissue penetration characteristics allow tissue absorption, replacement of granulation tissue, inducing tissue regeneration, and accelerating the healing of periapical lesions. Studies have shown that the efficacy of root canal therapy using primary or secondary methods, or many times France, shows no significant difference. As long as appropriate patient selection and meticulous operation are ensured, continuous use of root canal filling materials for disinfection can guarantee successful treatment. In summary, the clinical efficacy of Vitapex paste in single-visit root canal treatment for chronic periapical sinus certainly reduces the number of patient visits, with significantly fewer side effects, appropriate over-filling contributing to lesion healing, making it suitable for clinical use.