Heat Sterilization Methods Overview

Heat Sterilization Methods

• Common methods include dry heat and moist heat sterilization, ohmic heating.
• Freezing is NOT a heat sterilization method.

Mechanism of Heat Sterilization

• Heat kills microorganisms primarily by denaturing proteins, disrupting cell membranes, and inhibiting DNA replication.

Dry Heat Sterilization

• Requires higher temperatures and longer exposure times than moist heat due to slower heat penetration through materials.
• Water molecules transfer heat more effectively than air.
• Typically sufficient temperatures and times are 160°C for 2 hours.

Moist Heat Sterilization

• Commonly used for sterilizing surgical instruments.
• Effective for semi-critical and critical instruments.

Factors Influencing Heat Sterilization

• Temperature
• Exposure time
• Type of microorganism

Heat Inactivation of Coronaviruses

• Heat treatment effectively inactivates coronaviruses on surfaces and in suspension.
• Effectiveness depends on the specific strain and method.
• Moist heat is usually more effective than dry heat.

Chemical Sterilization Methods (Heat-Sensitive Instruments)

• Ethylene oxide gas, hydrogen peroxide gas plasma, peracetic acid are common methods.
• Autoclaving is NOT a chemical method, but a heat-based method.

Ethylene Oxide Gas Sterilization

• Highly effective against many microorganisms, including spores.
• Significant disadvantages include high toxicity and flammability, specialized equipment, and long cycle times.

Peracetic Acid Sterilization

• Effective sterilant.
• Considerations include its corrosive nature, need for thorough rinsing, and deactivation by organic material.

Factors Influencing Chemical Sterilization

• Sterilant concentration
• Exposure time
• Temperature

Glutaraldehyde

• High-level disinfectant, usually not a sterilant as not effective against spores unless prolonged exposure.

Hydrogen Peroxide Gas Plasma

• Suitable for sterilizing various materials including Stainless steel, Plastics, and some cellulose-based materials.
• Not suitable for liquids.

Peracetic Acid Mechanism

• Disrupts cell membranes, denatures proteins, and oxidizes cellular components.

Best Sterilization Method for Complex Instruments

• Hydrogen peroxide gas plasma is suitable for complex instruments due to its penetrating ability through intricate designs and lumens.

Dental Aerosols

• Mixture of solid and liquid particles generated during dental procedures.
• Primarily generated during procedures involving high-speed handpieces and ultrasonic scalers.

Concern of Dental Aerosols

• Transmission of infectious diseases.
• Irritation of eyes and respiratory tract.

Microorganisms in Dental Aerosols

• Bacteria, viruses, and fungi can be present.

Aerosol Particle Size

• Typically 0.1 to 100 micrometers in size for particles, but can be larger.

Reducing Dental Aerosol Generation

• High-volume evacuation
• Rubber dam isolation
• Pre-procedural mouth rinse can help reduce microbial load.

Personal Protective Equipment (Dental Professionals)

• Masks (N95 or equivalent)
• Eye protection
• Gloves

Airborne Aerosol Duration

• Dental aerosols can remain airborne for several minutes.

Dental Aerosol Management

• Increasing ventilation
• Using air purifiers with HEPA filters
• Directing airflow away from the patient

Splatter

• Larger and heavier aerosol particles.
• More likely to contain infectious microorganisms.

Preventing Bloodborne Pathogen Transmission

• Handwashing and use of protective equipment (gloves).
• Vaccination against Hepatitis B, Influenza, and MMR (Measles, Mumps, Rubella) are often recommended.

Hand Hygiene in Dental Setting

• Wash or sanitize hands before and after treating each patient
• Sanitize or wash after contact with contaminated surfaces
• Before and after putting on and removing gloves.

Sharps Handling

• Dispose of sharps in puncture-resistant containers immediately after use.

Reducing Airborne Transmission

• High-volume evacuation
• Use of rubber dam
• Proper ventilation.

Surface Disinfection

• Appropriate hospital-grade EPA-registered disinfectant is suitable for cleaning.

Pre-Procedural Mouth Rinses

• Typically contain Chlorhexidine gluconate, essential oils, and/or hydrogen peroxide, but not sodium fluoride.

Surface Barriers

• Used on surfaces frequently touched or vulnerable to contamination.
• Made from materials like plastic sheeting.
• Change barriers after each patient or when visibly soiled.

Sterility Maintenance

• Hand hygiene, instrument sterilization, surface disinfection and protective equipment are of utmost importance.

Critical Instruments

• Surgical instruments and scalpel and burs, for example.
• These often require heat sterilization methods (autoclaving or dry heat) or chemical sterilization methods (ethylene oxide).

Sterilization Monitoring

• Biological indicators verify both the sterilizer and procedure effectiveness.

Antiseptics in Dentistry

• Used to reduce microorganisms on living tissues, not for sterilizing instruments.
• Common antiseptics in dentistry include chlorhexidine gluconate, povidone-iodine and hydrogen peroxide.

Chlorhexidine Gluconate

• Broad-spectrum antiseptic, effective against various microorganisms.
• Potential side effects include staining and altered senses.

Povidone-Iodine

• Contraindications include iodine allergies and certain medical conditions.

Hydrogen Peroxide

• Releases oxygen radicals to damage microbial cells.

Typical Chlorhexidine Gluconate Mouth Rinse Concentration

• Typically 0.12%.

Antiseptic Substantivity

• Chlorhexidine gluconate has a longer substantivity than other antiseptics.