Objective The objective of this review was to evaluate the effect of subgingival debridement by ultrasonic debridement (UD) in comparison with subgingival air polishing (SubGAP) during periodontal maintenance. Methods A systematic search of electronic databases was conducted to identify publications from January 01, 2000, to December 21, 2018. Publication selection, data extraction, and risk of bias assessment were performed by two reviewers independently. The addressed problem-intervention-comparison-outcomes question was "For patients in the periodontal maintenance phase, is SubGAP more likely to result in better clinical outcomes than UD?" Results From a total of 435 articles identified, 6 studies were included. Although none of them was evaluated to have a low risk of bias, overall, the main reason was that blinding of personnel was almost impossible to achieve for the study design. Owing to the heterogeneity, the data from included studies could not be synthesized. Most of the included studies suggested no statistical difference in pocketdepth reduction, except for one which showed UD was superior to SubGAP. In terms of clinical attachment loss and gingival regression, no treatment was indicated to have more benefits than the other based on the present evidence. SubGAP had a preferable comfort level compared with UD, as reported. It must be noted that none of included studies' follow-up time was more than 1 year. Conclusion The clinical efficacy of SubGAP compared with that of UD for periodontal maintenance remains inconclusive on account of limited evidence. To date, neither SubGAP nor UD showed superior clinical effect when compared. High-quality, well-designed clinical studies are still needed to ascertain the long-term clinical stability.