Nonsurgical Periodontal Therapy and Chemotherapeutics
What this domain tests
Nonsurgical therapy is the foundation of periodontal care. Questions test mechanical debridement, adjunctive chemicals, antibiotic stewardship, and host modulation.
Core rules
- SRP removes biofilm and calculus from root surfaces. Hand and ultrasonic instruments achieve comparable outcomes in experienced hands.
- Full-mouth disinfection and full-mouth SRP within 24 hours have not consistently outperformed quadrant therapy; evidence is equivocal.
- Chlorhexidine 0.12–0.2% has substantivity of about 12 hours and is useful short-term when brushing is impossible. It stains, alters taste, and is not a long-term substitute for mechanical control.
- Local delivery systems such as minocycline microspheres, doxycycline gel, and chlorhexidine chips give modest pocket reduction as adjuncts.
- Systemic antibiotics are not routine for chronic periodontitis. Amoxicillin 500 mg plus metronidazole 400 mg three times daily for 7 days is an adjunct for Grade C disease or necrotizing disease, ideally after debridement.
- Subantimicrobial-dose doxycycline 20 mg twice daily modulates matrix metalloproteinases; it is not an antibiotic cure.
Worked example
A 38-year-old with generalized Stage III Grade C periodontitis, no allergies, and good compliance completes SRP. Pockets remain 6 mm or deeper with bleeding. Because the phenotype is rapidly progressing, adjunctive amoxicillin–metronidazole may be justified after re-evaluation, alongside risk-factor control. For a 60-year-old with Stage II Grade B disease and residual 5-mm pockets, antibiotics are not indicated; re-instrumentation and maintenance are appropriate.
Traps
- Prescribing antibiotics before mechanical therapy.
- Using chlorhexidine as a permanent mouthwash.
- Confusing host modulation with antimicrobial therapy.
- Assuming a single SRP session cures disease; re-evaluation at 6–8 weeks is required.