Impact of Plasma Surface Treatment on Implant Stability and Early Osseointegration: A Retrospective Cohort Study

(1) Introduction: The clinical success of dental implants depends on rapid osseointegration, which can be impaired by hydrocarbon contamination and biological aging of titanium surfaces. Chairside plasma surface treatment has emerged as a practical method to restore surface hydrophilicity and enhance early bone-implant integration. (2) Materials and Methods: This retrospective cohort study evaluated 73 plasma-treated implants placed in 47 patients from June 2023 to October 2024. Non-thermal atmospheric pressure plasma was applied immediately before placement using the ACTILINK™ Reborn system. Implant stability was assessed baseline, weekly for the first four weeks, and again at week 8 using resonance frequency analysis (ISQ). Subgroup analyses were conducted according to initial ISQ, jaw location, implant length/diameter, and final insertion torque. (3) Results: All implants healed uneventfully without a stability dip. Mean ISQ increased from 78.97 ± 5.52 at placement to 83.74 ± 4.36 at week 8 (<i>p</i> < 0.001). Implants with lower initial stability demonstrated the greatest relative gains, while those with very high initial stability showed minimal changes. Mandibular and shorter implants demonstrated higher stability gains compared to maxillary and longer fixtures. (4) Conclusions: Chairside plasma surface treatment was associated with progressive ISQ increases during the 8-week healing period. The greatest gains occurred in implants with lower initial stability, while very stable implants showed little change. Stability improvements were also greater in mandibular sites, shorter fixtures, and those with higher insertion torque. These findings are limited to short-term ISQ outcomes and require validation in prospective controlled trials with standardized protocols.