Sterilisation
On this page 2 sections
Methods
| Method | Main number | Mechanism | Used for | Notes |
|---|---|---|---|---|
| Autoclave | 121°C, 15 psi, 15–30 min | Moist heat | Dental instruments | |
| Autoclave | 134°C, ~3–5 min | Moist heat | Fast cycles | |
| Hot air oven | 160°C, 2 h | Oxidation | Glass, metal, oils | |
| Boiling | 100°C | Heat | Disinfection only | |
| UV | 254 nm | DNA damage | Air/surfaces | |
| Gamma | Co-60 | DNA/free radicals | Disposable equipment | |
| EtO | ~37–63°C | Alkylation | Heat-sensitive devices | |
| H₂O₂ plasma | ~40–60°C | Oxidation/free radicals | Heat-sensitive devices | |
| Glutaraldehyde | 2% | Alkylation | Mainly HLD | Sharps Added with sodium bicarbonate = full antimicrobial property |
| Peracetic acid | ~0.2% | Oxidation | Compatible instruments | |
| Filtration | 0.22 µm | Physical removal | Heat-sensitive liquids |
ANTISEPTICS
Antiseptic = chemical applied to living tissue/skin to inhibit or kill microorganisms.
| Antiseptic | Common concentration | Mechanism | Mainly used for | Important points |
|---|---|---|---|---|
| Alcohol – ethanol | 70% | Protein denaturation + membrane disruption | Skin preparation | Rapid; no reliable sporicidal activity |
| Isopropyl alcohol | 70% | Protein denaturation | Skin antisepsis | Similar to ethanol |
| Chlorhexidine (CHX) | 2–4% skin; 0.12–0.2% oral rinse | Disrupts cell membrane | Skin, oral cavity | Excellent substantivity; broad activity |
| Povidone-iodine | 10% solution (~1% available iodine) | Oxidation/iodination | Skin, mucosa | Broad spectrum; less residual activity than CHX |
| Iodine | ~1–2% | Oxidation/iodination | Skin | Older preparation; staining/irritation |
| Hydrogen peroxide | 3% | Oxidation/free radicals | Wound cleansing historically | Limited tissue use; not preferred for routine wound antisepsis |
| Triclosan | ~0.1–0.5% | Inhibits fatty-acid synthesis | Antiseptic soaps historically | Limited modern use because of resistance/environmental concerns |
| Hexachlorophene | 3% | Disrupts bacterial membrane | Historical surgical/skin antisepsis | Mainly Gram-positive; neurotoxic, especially in infants |
| Benzalkonium chloride | ~0.01–0.1% | Membrane disruption | Skin/mucosal antisepsis | Quaternary ammonium compound |
| Cetrimide | ~0.5% | Membrane disruption | Skin cleansing/antisepsis | Often combined with other agents |
| Silver compounds | Variable | Protein binding/enzymatic inhibition | Burns/wounds | Modern use is formulation-specific |
DISINFECTANTS
Disinfectant = chemical used on inanimate objects/surfaces to destroy pathogenic microorganisms.
| Disinfectant | Common concentration | Level | Used on | Key point |
|---|---|---|---|---|
| Alcohol | 70% | Intermediate | Small surfaces/equipment | Rapid; no spores |
| Sodium hypochlorite | 0.1–0.5% depending on purpose | Intermediate/high depending on concentration/use | Surfaces, blood spills | Chlorine-releasing agent |
| Glutaraldehyde | 2% | High-level | Heat-sensitive instruments | Can achieve sterilization with prolonged validated exposure |
| OPA | 0.55% | High-level | Heat-sensitive instruments/endoscopes | Ortho-phthalaldehyde |
| Hydrogen peroxide | ~2–7.5%, product dependent | Low → high depending on formulation | Surfaces/instruments | Oxidizing agent |
| Peracetic acid | ~0.2% in some systems | High-level/sterilant | Automated instrument systems | Powerful oxidizer; sporicidal |
| Phenolics | ~0.5–3%, product dependent | Intermediate | Environmental surfaces | Good against bacteria/fungi; poor against spores |
| Quaternary ammonium compounds | ~0.1–0.2%, product dependent | Low | Environmental surfaces | Good for routine environmental cleaning |
| Formaldehyde | Variable | High-level/sterilant | Historical/controlled applications | Toxic; carcinogenic concern |
| Iodophors | Variable | Low/intermediate | Environmental surfaces | Iodine-releasing compounds |
| Chlorine dioxide | Variable | High-level | Water/surfaces | Strong oxidizer |