Dental bacterial plaque is the most frequent modifiable finding in patients with periodontal (gum) diseases. Many studies have provided evidence that mechanical removal of dental plaque is critical for improving the periodontal health. The standard initial treatment of periodontitis (gum disease) is to remove plaque and calculus form the teeth and root structures using sclaing and root planing (SRP). Typically hand instruments and an ultrasonic scaler are used for SRP

While this method removes some of the bacteria that leads to periodontitis, microorganisms are not completely eliminated through SRP. Studies have shown that after 3 months, the bacteria initially present prior to scaling and root planing had recolonized. In order to prevent recurrence of periodontitis, it is recommended that oral bacteria be kept at low levels.

When used at the proper wave length, dental lasers have been shown to effectively removes calculus, without damaging surrounding tissue. The Er:YAG laser has been FDA-approved for the use of scaling and root planing in Dentistry. While studies on the Er:YAG laser have shown that it is effective in removing calculus and preserving the tooth root structure, there is no consensus of the level of calculus removal. The Er:YAG laser may also be more effective in removing microbial bacteria than SRP with hand instruments and ultrasonic scaler.

The purpose of this study is to evaluate the effectiveness of the Er:YAG laser, as an adjunct to scaling and root planing, in removing microbial bacteria. Participants with chronic periodontitis will be randomized to have one quadrant undergo scaling and root planing using hand instruments and ultrasonic scaler alone, while a second quadrant will receive the same treatment, with the addition of the Er:YAG laser. Outcomes studies will be traditional periodontal clinical parameters at 6 weeks and 3 months after treatment. Microbial cultures will be performed at baseline and 3 months to compare survival and re-population by periodontal microorganisms.

Primary Aim: The primary aim of this study is to evaluate the efficacy of Er:YAG laser as an adjunct to mechanical scaling and root planing periodontal therapy by comparing probing depth and clinical attachment levels.

Secondary aim: The secondary aim of this study is to evaluate the efficacy of Er:YAG laser as an adjunct to mechanical scaling and root planing periodontal therapy by comparing gingival bleeding index and plaque index.

Tertiary aim: The tertiary aim of this study is to compare the microbial outcomes of mechanical periodontal therapy alone vs. mechanical therapy combined followed with Er:YAG laser therapy at the same time.

Inclusion Criteria:

• Patients enrolled in the Post-Graduate Periodontology Clinic at Tufts University School of Dental Medicine (TUSDM)
• Recent (within the past 30 days) diagnosis of moderate to severe chronic periodontitis in at least two quadrants according to the Armitage Classification
• Have had full mouth and vertical bite-wing series of diagnostic radiographs exposed at TUSDM within 6 months preceding entry of the study as a standard of care
• Have a treatment plan made by the original provider and certified by the PI based on the working diagnosis, presenting etiology, and the predicted therapeutic outcomes of the case (prognosis).
• Each of the two selected quadrants should have at least 5 teeth including the canine, first premolar and second premolar in contact with at least one tooth that has ≥ 5 mms and ≤ 9 mms probing depths with bleeding on probing.

Exclusion Criteria:

• Participants must not have had mechanical debridement or any other professional periodontal therapy within 6 months preceding entering the study
• Participants with significant chronic oral soft tissue pathology (lichen planus, Benign Mucous Membrane Pemphigoid, Steven Johnson's Syndrome, Sjogren's Syndrome, etc.) which might affect host response to the presence of bacteria.
• Participants with fixed appliances or partial dentures, to standardize the effect of the treatment since they are plaque retentive.
• Participants who smoke tobacco
• Participants who require prophylactic antibiotics prior to dental treatment
• Participants who have taken systemic antibiotic medications within the previous 6 months
• Participants with uncontrolled systemic conditions or disease such as diabetes and immunological disorders
• Participants with known drug allergies or known adverse effects following the use of oral hygiene products.
• Participants who are pregnant or lactating
• Teeth with grade III mobility or teeth with hopeless prognosis indicated for extraction