Periodontitis (gum disease) is an infection of the gums that can lead to tooth loss. In recent years, many types of dental lasers or other devices have been used for the non-surgical treatment of periodontal diseases. However, it remains unclear whether the combined application of laser and air polishing is effective as an adjuvant treatment for periodontitis. The purpose of this study is to compare the use of combined application of Er:YAG laser and sub-gingival air polishing powder, with the treatment of Er:YAG laser only, in periodontal diseases treatment in a Chinese population.

The study will use a split-mouth design, two quadrants (one quadrant from each jaw) were randomly allocated to either the test or control group. The quadrants in the test group received Er:YAG laser (ERL) plus sub-gingival air polishing treatment, while the quadrants in the control group received ERL only. Clinical periodontal examinations were evaluated at baseline, 3 months, 6 months, 1 year, and 2 years.

Inclusion Criteria:

• 1) aged 35-65 years old, in good systemic healthy;
• 2) clinically diagnosed with generalized stage Ⅱ or stage Ⅲ periodontitis;
• 3) a minimum of 20 teeth

Exclusion Criteria:

• 1) pregnancy or recent pregnancy plans;
• 2) had received periodontal treatment within the previous 6 months;
• 3) taken antibiotics within the previous 3 months;
• 4) had diabetes;
• 5) obvious malocclusion, history of orthodontic treatment, or a habit of mouth breathing.