TREATMENT OF TEMPOROMANDIBULAR-JOINT STRUCTURES BY 308-NM EXCIMER-LASER - AN IN-VITRO INVESTIGATION

Arthroscopy of the temporomandibular joint (TMJ) has become a clinically important and increasingly accepted method for diagnosis and treatment of TMJ alteration. This minimally invasive method is clearly limited by the anatomic dimensions of the TMJ. The 308-nm excimer laser has already found clinical applications in angioplasty, ophthalmology, and dentistry. This study aimed to find out whether it is possible to ablate TMJ-related structures under arthroscopic conditions. It also aimed to determine the energy threshold for ablation and the maximum rate of ablation. By histologic investigation of the irradiated tissues, the amount of tissue alteration was determined. TMJ structures of freshly slaughtered pigs served as tissue samples. The 308-nm excimer laser light was guided through optical fibers. The tissue was irradiated under continuous flow of saline solution. The energy threshold for ablation of TMJ structures was found at about 1 J/cm2. The maximum rate of ablation was found at 3-5 mum/pulse, depending on the type of tissue. The amount of tissue alteration varied between 1 and 150 mum. The types of tissue alteration were vacuolization and hyalinization. The results of the investigations described indicate that the 308-nm excimer laser is an ideal tool for TMJ arthroscopic surgery. Unlike other laser systems, it offers a unique combination of minimal tissue alteration, precise tissue ablation, guidability through optical fibers, and good transmission through water. This makes possible endoscopic removal of free bodies, adhesions, exostoses, and appositions in a minimally invasive surgical procedure.