Objective: The aim of this study was to evaluate, under intraoral conditions, the opening resistance of the clip mechanisms of two passive self-ligating bracket systems, Damon Q2 and Damon Ultima, to support reliable bracket selection in clinical practice. Subjects and Methods: The materials consisted of measurements obtained from passive self-ligating maxillary first premolar brackets used in the orthodontic treatment of 20 patients. The force required to open the clips of Damon™ Q2 SL and Damon™ Ultima SL brackets (Ormco Corporation, California, USA) was recorded in grams using a digital force gauge mounted on a custom-designed experimental setup. After the initial measurements, the brackets were bonded to the palatal surfaces of the maxillary first premolar teeth. The experimental apparatus consisted of two parallel black acrylic blocks, a step motor providing linear motion, a motor control unit, and a digital force gauge. A clip-opening mechanism was fixed to the stationary block, while the force gauge was attached to the movable block. Linear movement was generated at a constant speed of 5 mm/min.After three months of intraoral use, the brackets were debonded and the measurements were repeated. Results: The results demonstrated that the mean clip-opening force of the Damon Ultima bracket at baseline (T0) was significantly higher than that of the Damon Q2 bracket. Although no significant difference was observed between the two systems at T1, the magnitude of force change from T0 to T1 was significantly greater for the Damon Q2 bracket. Conclusion: Intraoral exposure significantly increased the clip-opening resistance of both bracket systems. Damon Ultima showed higher initial forces, while Damon Q2 exhibited greater changes over time. These differences may influence clinical bracket selection. Further studies are needed to evaluate long-term performance.