Methylene blue dye: an aid to endodontic surgery.

In dentistry, methylene blue dye (injection USP 1%; American Quinine Co., Inc. Shirley, NY) is mainly used for laboratory research. In endodontics, it is used most often in marginal leakage studies to stain and locate those areas of the root canal system not sealed by the obturating material (1). It is also used to treat methemoglobenemia due to prilocaine toxicity (2, 3). Methyleneblue dye is often used in general medicine. It is injected intravenously to evaluate renal function. General surgeons inject the dye into sinus tracts that dissect through healthy tissues from a source of infection, making the outlined tracts easier to identify and remove. Vital staining with methylene blue dye has been used previously by us to selectively stain tissue during molar surgery (4) when the ability to differentiate tooth from bone is hindered by poor visibility, excessive bleeding, or unusual root anatomy. Once the root has been located and the initial resection accomplished, methylene blue dye (Fig. 1) is dabbed onto the amputated root surface with a sterile cotton pellet for 1 to 2 min. The surgical area is then washed with sterile saline solution. The remaining dye will stain not only the internal root canal anatomy exposed by the resection but also the periodontal ligament (Fig. 2). Such differential staining outlines the root anatomy enhancing the operator's ability to complete the resection of the root and to expose any existing isthmuses (Fig. 3). If an isthmus of pulp tissue joining two canals in a single root is exposed by resection, the apical amalgam must be placed so that the two canals as well as the isthmus will be filled and sealed (4, 5). Methylene blue dye has also been used in an earlier research study to determine the incidence of isthmuses connecting two canals in single roots (4). The study