9.2 Subgingival Debridement, Plaque Control & Antimicrobial Adjuncts

9.2 Subgingival Debridement, Plaque Control & Antimicrobial Adjuncts

Non-surgical periodontal therapy represents the fundamental initial phase of periodontal management (Step 1 and Step 2 therapy according to the EFP S3 Level Clinical Practice Guidelines adapted for Australian practice). The primary biological objective is to suppress dysbiotic subgingival biofilms, eliminate calcified accretions (calculus), reduce tissue inflammation, and establish a bio-acceptable root surface that permits periodontal healing via a long junctional epithelium.

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1. Step 1 Therapy: Supragingival Biofilm Control & Risk Factor Modification

Step 1 therapy aims to empower the patient through behavioural change, mechanical plaque control instruction, professional mechanical plaque removal (PMPR), and risk factor control.

A. Mechanical Biofilm Removal Techniques

• Toothbrushing: The Modified Bass Technique is recommended. The bristles are placed at a 45-degree angle to the long axis of the tooth directed into the gingival sulcus, vibrated with small circular/sulcular motions, and rolled occlusally.
• Interdental Cleaning (Gold Standard): Interdental brushes (IDBs) are significantly more effective than dental floss for biofilm removal in open interdental spaces (Types II and III embrasures). IDBs must be sized correctly to fit snuggly without wire-to-tooth contact (utilizing colour-coded sizing probes).
• Dental Floss: Indicated strictly for Type I embrasures where interdental papillae completely fill the interproximal space and tight contact points prevent IDB insertion.

B. Chemical Plaque Control (Mouthrinses)

• Chlorhexidine Gluconate (0.2% or 0.12%): Gold standard chemical anti-plaque agent. Its bisbiguanide structure imparts strong substantivity (binds to oral mucosa and tooth enamel, releasing slowly over 12 hours).
• Indications: Short-term adjunct (1 to 2 weeks) following periodontal surgery, during acute necrotising periodontal conditions, or when mechanical brushing is painful or contraindicated.
• Adverse Effects: Extrinsic brown staining of teeth and tongue, dysgeusia (taste alteration), enhanced supragingival calculus formation, and rare mucosal desquamation.
• Drug Interaction: Chlorhexidine is inactivated by anionic surfactants such as sodium lauryl sulfate (SLS) found in standard toothpastes. Patients must rinse with water or wait at least 30 minutes between toothbrushing and Chlorhexidine rinsing.

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2. Step 2 Therapy: Subgingival Instrumentation (SGI)

Subgingival instrumentation (formerly termed root surface debridement or scaling and root planing) involves the mechanical removal of subgingival biofilm and calculus from root surfaces.

A. Hand Instrumentation: Gracey Area-Specific Curettes

Gracey curettes feature a offset working blade angled at 70 degrees to the lower shank. Only the lower, longer curved cutting edge is used for debridement.

Working Adaptation: To establish the correct 70-degree cutting angle against the root surface, the clinician must align the lower (terminal) shank parallel to the surface being debrided.

B. Power-Driven Instrumentation: Sonic & Ultrasonic Scalers

• Magnetostrictive Units (20,000 - 40,000 Hz): Stack of nickel-iron alloy leaves; insert tip moves in an elliptical pattern, active on all 4 sides.
• Piezoelectric Units (25,000 - 50,000 Hz): Ceramic crystals; insert tip moves in a linear back-and-forth pattern, active primarily on lateral sides.
• Biological Mechanisms: Fluid lavaging cleanses the pocket, while cavitation (collapse of microbubbles creating shockwaves) and acoustic microstreaming disrupt bacterial cell walls.

C. Debridement Protocol: Full-Mouth vs Quadrant Scaling

Randomized clinical trials demonstrate that Full-Mouth Debridement (FMD) completed in one or two sessions within 24 hours yields equivalent clinical outcomes (probing depth reduction and attachment gain) to traditional quadrant scaling performed over 4 weekly appointments. Choice of protocol depends on patient medical status, anxiety, compliance, and appointment logistics.

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3. Antimicrobial Adjuncts & Prescribing Guidelines (eTG Dentistry)

Routine systemic antibiotic administration for standard Stage I, II, or III periodontitis is contraindicated in Australian dental practice due to rising global antimicrobial resistance.

A. Systemic Antibiotics (eTG Prescribing Criteria)

Systemic antibiotics are indicated strictly as an adjunct to mechanical subgingival debridement in specific aggressive or non-responding cases:

1. Stage IV Grade C Periodontitis in Young Adults (rapidly progressive breakdown).
2. Necrotising Periodontitis with systemic involvement (fever, malaise, lymphadenopathy).
3. Refractory Periodontitis despite technically thorough debridement.

Clinical Warning on Metronidazole: Metronidazole causes a severe disulfiram-like reaction if consumed with alcohol (nausea, vomiting, flushing, tachycardia) and significantly potentiates Warfarin, raising the patient's INR and bleeding risk.

B. Locally Delivered Antimicrobial Devices

Locally delivered sustained-release devices (e.g. Chlorhexidine chip / PerioChip, Minocycline microspheres, Doxycycline gel) are inserted directly into deep residual pockets (≥5 mm with BOP) following initial debridement. While they provide modest localized pocket depth reduction, they are expensive, site-specific adjuncts and cannot replace mechanical debridement.

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4. Post-Debridement Re-Evaluation Protocol (Step 2 Outcome Assessment)

Re-evaluation must be conducted 8 to 12 weeks post-completion of subgingival debridement. Evaluating earlier than 8 weeks yields inaccurate probing measurements due to immature, healing connective tissue.

Key Healing Phenomena & Endpoints:

• Tissue Resolution: Reduction of gingival edema, resulting in tissue recession and decreased probing depth.
• Long Junctional Epithelium (LJE): Primary mode of repair following non-surgical debridement (no new connective tissue attachment or bone growth occurs non-surgically).
• Successful Endpoints:
  • Full-mouth plaque score < 20%.
  • Full-mouth BOP score < 10-15%.
  • Absence of residual pockets ≥ 5 mm with BOP (ideal probing depths ≤ 4 mm without BOP).
  • Sites exhibiting residual probing depths ≥ 6 mm with BOP represent non-responding sites requiring Step 3 Surgical Evaluation.