3.3 Dental Antibiotic Prescribing, Prophylaxis & Therapeutic Guidelines

3.3 Dental Antibiotic Prescribing, Prophylaxis & Therapeutic Guidelines

Antimicrobial resistance represents a global public health crisis. In dental practice, prescribing must adhere strictly to Australian Therapeutic Guidelines: Dental (eTG). Antibiotics are secondary adjuncts to definitive local operative intervention (e.g., endodontic therapy, incision and drainage, or tooth extraction) and are never a substitute for operative care.

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Principles of Dental Antimicrobial Stewardship

Dentists prescribe approximately 10% of all outpatient human antibiotics. Overprescribing contributes directly to selection pressure for resistant strains (such as MRSA and $VRE$), disruption of the human microbiome, and severe adverse drug events including Clostridioides difficile colitis.

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|                               CORE ANTIMICROBIAL STEWARDSHIP RULES                                |
|                                                                                                   |
|  1. Operative Drainage / Debridement is mandatory — Antibiotics do not penetrate necrotic pulps.   |
|  2. Limit use strictly to systemic signs or rapidly spreading infection.                         |
|  3. Use narrow-spectrum agents at target therapeutic doses for the shortest effective duration.    |
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Clinical Conditions where Antibiotics are NOT Indicated

• Irreversible pulpitis or acute apical periodontitis.
• Localised dentoalveolar abscess without fever or facial swelling.
• Alveolar osteitis (dry socket).
• Pericoronitis restricted to local operculum inflammation without systemic signs or trismus.
• Periodontal abscess accessible for immediate debridement/drainage.
• Routine uncomplicated tooth extractions in healthy individuals.

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Indications for Systemic Antibiotics

Systemic empirical antibiotic therapy is indicated only when local operative measures are insufficient or delayed, accompanied by one or more of the following:

1. Spreading Infection: Cellulitis, extraoral swelling, diffuse tissue space involvement (e.g., submandibular, sublingual, lateral pharyngeal spaces).
2. Systemic Manifestations: Fever ($>38^\circ\text{C}$), tachycardia, malaise, lethargy, or regional lymphadenopathy.
3. Trismus: Indicating infection spread to the muscles of mastication or pterygomandibular space.
4. Immunocompromised Host: Patients undergoing active chemotherapy, severe uncontrolled diabetes ($\text{HbA1c} > 9%$), high-dose systemic immunosuppression, or advanced HIV.

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First-Line & Alternative Empirical Prescribing Regimens

Odontogenic infections are polymicrobial, involving facultative anaerobes (Streptococcus anginosus group) and strict anaerobes (Prevotella, Porphyromonas, Fusobacterium species).

SUMMARY OF DRUG DOSAGES:
- Amoxicillin: 500 mg oral q8h
- Metronidazole: 400 mg oral q8h (Strictly avoid alcohol due to disulfiram-like reaction)
- Clindamycin: 300 mg oral q8h (Monitor for watery diarrhea / C. difficile risk)
- Cephalexin: 500 mg oral q6h (Avoid in immediate IgE anaphylaxis to penicillin)

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Management of Severe & Spreading Odontogenic Infections

Rapidly spreading odontogenic infections can cause life-threatening airway compromise (e.g., Ludwig's Angina) or descend into the superior mediastinum (Descending Necrotising Mediastinitis).

Ludwig's Angina

Rigid, brawny, bilateral cellulitis involving the submandibular, sublingual, and submental spaces simultaneously. Primary origin is typically mandibular second or third molars whose roots extend inferior to the mylohyoid muscle attachment.

• Clinical Red Flags: Elevation and protrusion of the tongue, inability to swallow saliva (drooling), stridor, dyspnea, "hot potato" voice.
• Emergency Management: Immediate emergency hospital referral (000), securing airway via fiberoptic intubation or tracheostomy, high-dose intravenous antibiotics (e.g., IV Benzylpenicillin + Metronidazole or IV Lincomycin/Clindamycin), and emergency surgical incision and decompression.

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Prevention of Infective Endocarditis (IE)

In accordance with guidelines from the Therapeutic Guidelines: Dental and the Heart Foundation of Australia, antibiotic prophylaxis is not recommended for the vast majority of cardiac patients. It is restricted strictly to patients possessing high-risk cardiac conditions undergoing high-risk dental procedures.

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|                               INFECTIVE ENDOCARDITIS RISK MATRIX                                  |
|                                                                                                   |
|  HIGH-RISK CARDIAC CONDITION   +   HIGH-RISK DENTAL PROCEDURE   ===>  ANTIBIOTIC PROPHYLAXIS      |
|  (Prosthetic valves, prior IE,     (Gingival manipulation,            INDICATED                   |
|   cyanotic CHD, cardiac transplant) periapical/mucosal puncture)                                  |
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High-Risk Cardiac Conditions Requiring Prophylaxis

1. Prosthetic Cardiac Valves or prosthetic material used for cardiac valve repair.
2. Previous History of Infective Endocarditis.
3. Congenital Heart Disease (CHD):
   • Unrepaired cyanotic congenital heart disease (including palliative shunts and conduits).
   • Completely repaired congenital heart defect with prosthetic material during the first 6 months post-procedure.
   • Repaired CHD with residual defects at or adjacent to the site of a prosthetic patch or prosthetic device.
4. Cardiac Transplant Recipients who develop cardiac valvulopathy.

Note: Prophylaxis is NO LONGER RECOMMENDED for rheumatic heart disease, mitral valve prolapse, coronary artery stents, or prosthetic joint replacements.

High-Risk Dental Procedures

Procedures involving manipulation of gingival tissue, the periapical region of teeth, or perforation of the oral mucosa (e.g., extractions, subgingival scaling, root planing, endodontic instrumentation beyond apex, matrix band placement, biopsy).

Recommended Prophylactic Regimens (Single Pre-Procedure Dose)

All doses administered 30 to 60 minutes prior to dental procedure:

• Standard Adult Dose: Amoxicillin 2 g orally (Children: 50 mg/kg up to 2 g).
• Penicillin Allergic (Non-Immediate / Mild): Cephalexin 2 g orally (Children: 50 mg/kg).
• Severe Penicillin Allergy (Immediate IgE / Anaphylaxis): Doxycycline 100 mg orally (child dosing per current Therapeutic Guidelines/ADA advice) OR Azithromycin 500 mg orally (Children: 10 mg/kg up to 500 mg). Clindamycin is no longer preferred for IE prophylaxis in current Australian guidance.