Abstract: [Abstract] Objective In our previous study ，we have demonstrated that the two-incision fistula operation was an effective and safe as a treatment for oral ranulas. Following the previous study, we try to explore the mechanism of the two-incision fistula technique for the treatment of oral ranulas, which may be a new treatment for the retention cyst. Methods A total of 19 patients were enrolled. All of the cases were oral ranulas. Minimally invasive treatment of oral ranulas was performed by the two-incision fistula technique. Two paralleled incisions were initially made at the apex of cyst of sublingual gland. After the mucus had drained, the incision was sutured with the middle mucosal strip in the cyst. Results 16 cases were cured and there were no complications. 3 cases recurred, but disappeared after a second operation. There were 14 patients whose wound dehiscence and 5 patients whose suture were safe after 7 days for operation. For the 3 patients recurred, there were 1 patient whose wound was dehiscence and 2 patients whose suture were safe. Conclusion Two-incision fistula technique is a new treatment to oral ranulas. The operation mechanism may be related to the formation of fistula on the surface of suturing the mucosa or mucosal fistula because of the thin mucosa after wound dehiscence.

Key words: [key words] Oral ranulas, The mechanism, Two-incision fistula operation, Fistula