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The Periodontal Adjunctive Antibiotics Study (PAAS)

September 7, 2023
Brittni Ball
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Studies

The PAAS study evaluated the effectiveness of adjunctive antibiotics in the treatment of periodontal disease. This large, pragmatic randomized clinical trial engaged practitioners from the South Central, Southwest, and Western Nodes of the National Dental PBRN. In total, the Network successfully completed recruitment, enrolling 258 consented participants, 239 randomized, and completing 227 baseline visits during the active enrollment window. Data collection officially ended December 31, 2025 as the study moved fully into the data‑cleaning and analysis phase.

Patients with periodontitis were randomly assigned to either receive scaling and root planing (SRP) plus adjunctive antibiotics or SRP plus placebo. The study adjunctive antibiotics were Metronidazole 500 mg and Amoxicillin 500 mg every 8 hours for 10 days. The interventions were provided by a dentist or hygienist. Participants were followed through their 6‑week and 12‑month visits, and the team completed final periodontal chart entry.

WHY WAS THIS STUDY DONE?

Antibiotic stewardship calls for optimizing antibiotic prescribing to effectively treat infections, and to reduce antibiotic misuse to prevent the development of antibiotic-resistant microbial strains.

Historically, antibiotics have been an integral part of periodontal disease treatment. The combined use of Amoxicillin, a broad spectrum antibacterial of the penicillin family, and Metronidazole, active against most anaerobic bacteria and some protozoans, have become the most prescribed antibiotic adjunct in the treatment of chronic periodontal disease. However, a systematic review on nonsurgical treatment of periodontitis[1] revealed that only small-scale clinical trials were available to support recommending antibiotics to severe or aggressive periodontitis cases. The ADA expert panel[2] recommendation for antibiotics as adjunctive therapies to SRP was considered of weak strength and suggested that larger pragmatic clinical trials would benefit dental professionals in their clinical decision making.

WHAT WAS EXPECTED OF PRACTITIONERS?

Participating practitioners played a central role in the success of the study. Their responsibilities included:

Recruiting eligible adult patients with periodontitis
Administering the screening form and obtaining informed consent
Conducting baseline periodontal charting and uploading full‑mouth probing data
Dispensing study medication or placebo at the SRP appointment
Counseling patients on oral hygiene practices
Completing post‑visit surveys at approximately 6‑weeks and 12‑months
Uploading periodontal charts at each designated study visit

Practitioners met these responsibilities across multiple sites, contributing to a diverse, real‑world dataset that reflects everyday clinical practice.

WHICH PATIENTS COULD PARTICIPATE?

Patients were eligible to participate if they met the following criteria at the time of recruitment:

Age 35 or older
Diagnosed with periodontitis
Suitable candidates for non‑surgical periodontal therapy
Willing to complete follow‑up visits and study procedures

Enrollment closed at the end of 2025, and all patients who entered the study completed the protocol through their scheduled visits based on individual SRP timelines.

CURRENT UPDATES

With enrollment and follow‑up complete, the PAAS study moved into its final operational phase during early 2026. Current study activities include:

Data Cleaning & Dataset Preparation
Adverse Event Analysis
Double Data Entry & Quality Control
Study Payments

PAAS New Progress and New Criteria Webinar March 2025

PAAS Best Practices Webinar August 2024

PAAS Introduction Webinar February 2024

[1] Smiley CJ, Tracy SL, Abt E, Michalowicz BS, John MT, Gunsolley J, Cobb CM, Rossmann J, Harrel SK, Forrest JL, Hujoel PP, Noraian KW, Greenwell H, Frantsve-Hawley J, Estrich C, Hanson N. Systematic review and meta-analysis on the nonsurgical treatment of chronic periodontitis by means of scaling and root planing with or without adjuncts. J Am Dent Assoc. 2015 Jul;146(7):508-24.e5. doi: 10.1016/j.adaj.2015.01.028. PMID: 26113099.

[2] Smiley CJ, Tracy SL, Abt E, Michalowicz BS, John MT, Gunsolley J, Cobb CM, Rossmann J, Harrel SK, Forrest JL, Hujoel PP, Noraian KW, Greenwell H, Frantsve-Hawley J, Estrich C, Hanson N. Evidence-based clinical practice guideline on the nonsurgical treatment of chronic periodontitis by means of scaling and root planing with or without adjuncts. J Am Dent Assoc. 2015 Jul;146(7):525-35. doi: 10.1016/j.adaj.2015.01.026. PMID: 26113100.