Purpose: The aim of the this study was to determine if mixing dextrose with local anesthetic could alter the clinical outcome of dextrose prolotherapy for TMJ subluxation. Patients and Methods: Eighteen patients with painful subluxation of the TMJ were randomly assigned to 1 of 2 equal-sized groups. Patients in the active group received 4 injections of dextrose solution (2 mL of 10% dextrose and 1 mL of 2% mepivacaine) for each TMJ, each 6 weeks apart, whereas patients in the placebo group received injections of placebo solution (2 mL of 10% dextrose and 1 mL Of saline solution) on the same schedule. A numerical rating scale (NRS) expressing TMJ pain on rest and during function , maximal mouth opening (MMO), clicking sound, and frequency of luxations (number of locking episodes per month) were assessed at each injection appointment just before the injection procedure and 3 months after the last injection. The collected data were then statistically analyzed. Results: All the evaluated parameters showed insignificant differences between the two groups throughout the study intervals with the exception that pain on function at 18 weeks postoperatively significantly decreased in group 1 than in group 2 and the number of analgesic intake was significantly decrease in group 1 compared to those in group 2 at 6 weeks and 3 months after injection. The frequency of luxations means significantly decreased in all post-injection intervals relative to the preoperative mean in each group. The mouth opening showed insignificant decrease by time in both groups. By the end of the study, group 2 showed higher prevalence of clicking than group 1. Conclusion: Based on the results of the present study, local anesthetic could not be considered as an integral part of the dextrose solution for prolotherapy as evident by its minor analgesic effect.