Aim: The aim of this study is to evaluate the clinical efficacy of subgingival glycine powder air polishing in periodontitis during PMT. Materials and methods: Forty PMT patients were recruited from subjects referred to the Department of Periodontology, Faculty of Dentistry, Damascus University. AgP group comprised twenty patients diagnosed with generalized aggressive periodontitis, whereas ChP group included 20 patients diagnosed with generalized chronic periodontitis. Using a split mouth study design, subgingival plaque was removed by means of glycine powder air polishing GPAP or curettes MCD. Clinical periodontal parameters were recorded at baseline and at 3 months after treatment. A visual analog scale was used to evaluate inconvenience during therapy. Results: The two studied groups showed improvements in all clinical indices after 3 months (p = 0.001). There were no significant statistical differences between GPAP and MCD in both of AgP and ChP groups (p > 0.05). GPAP therapy was significantly less painful than MCD in AgP and ChP groups (p = 0.018, p = 0.038, respectively). Conclusion: Subgingival glycine air polishing was effective in treatment periodontitis during maintenance care and perceived to be more acceptable by the patients than conventional curettes. Clinical significance: Subgingival glycine air polishing has been shown to remove biofilm in periodontal pockets without causing damage to the root surfaces or soft tissues; therefore, it was suggested to be used as an alternative to repeated use of conventional curettes in periodontal maintenance therapy (PMT).