23.1 Infection Control & Sterilization
Key Takeaways
- Standard (routine) precautions treat all blood, saliva, and body fluids as potentially infectious—hand hygiene, PPE, safe sharps, and environmental controls apply to every patient.
- Critical instruments penetrate soft tissue or bone and require sterilization; semi-critical touch mucous membranes and need sterilization or high-level disinfection; noncritical touch intact skin and need intermediate- or low-level disinfection.
- Steam autoclave sterilization is the dental workhorse; chemical vapor and dry heat are alternatives with different temperature/time and material constraints—know the concept, not a single brand recipe.
- Biological (spore) testing is the gold-standard monitor of sterilizer function; chemical indicators and mechanical readouts support but do not replace spore tests.
- Bloodborne pathogens of highest dental concern include HBV, HCV, and HIV; prevent exposure with engineering controls, work practices, PPE, and immediate post-exposure protocols.
23.1 Infection Control & Sterilization
Quick Answer: Protect patients and the dental team with standard precautions (hand hygiene, PPE, safe injection/sharps, environmental cleaning) applied to every patient. Classify instruments with the Spaulding system: critical → sterilize, semi-critical → sterilize (preferred) or high-level disinfect, noncritical → intermediate/low-level disinfect. Validate sterilizers with biological (spore) tests, not chemical indicators alone. Know steam autoclave as first-line sterilization and the roles of chemical vapor and dry heat.
Infection control sits inside the AFK blueprint cluster covering evidence-based dentistry, prevention, infection control, and ethics (collectively about 5 ± 5%). Items test decision rules: which process for which instrument, what monitoring proves sterilization, and how to prevent bloodborne pathogen transmission—not brand-name product catalogs.
Why Infection Control Is Non-Negotiable
Dental procedures generate blood, saliva, aerosols, and contaminated instruments. The oral cavity harbors pathogens; many patients have undiagnosed bloodborne infections. Regulatory colleges and public-health guidance expect written policies, staff training, equipment maintenance logs, and a culture of safety. AFK questions reward the clinician who chooses the most protective correct option without unnecessary overkill (e.g., “autoclave the operatory floor”).
Standard (Routine) Precautions
Standard precautions assume that all blood, body fluids, secretions, excretions (except sweat), non-intact skin, and mucous membranes may contain transmissible agents. They replace the outdated idea of using extra barriers only for “known infectious” patients.
| Element | AFK teaching points |
|---|---|
| Hand hygiene | Before/after patient contact, after glove removal, after contact with contaminated surfaces; soap-and-water when hands are visibly soiled or after known spore risk; alcohol-based rubs when hands are not visibly soiled |
| PPE | Gloves, protective eyewear/face shield, mask, gown/clinic attire as indicated by splash/spray risk |
| Respiratory hygiene | Cough etiquette; mask symptomatic patients when appropriate; ventilation awareness |
| Safe injection practices | Single-dose vials preferred; never reuse needles/syringes between patients; multi-dose vials handled with aseptic technique |
| Sharps safety | Engineered sharps protection, immediate disposal, never recap with two-handed technique |
| Environmental cleaning | Clinical contact surfaces cleaned then disinfected between patients; house-keeping surfaces regularly |
| Instrument processing | Contaminated → transport → clean → package → sterilize → store |
| Waste | Biomedical/sharps waste segregated per local rules |
Transmission-based precautions (contact, droplet, airborne) are added when a known/suspected infection requires more than standard precautions (e.g., active tuberculosis—defer elective care; use airborne precautions and public-health pathways). AFK expects you to escalate thoughtfully, not invent isolation units for every cold.
Personal Protective Equipment (PPE)
PPE is the last line after elimination/engineering/work-practice controls—but it is mandatory in routine dentistry because exposure risk is continuous.
| PPE item | Purpose | Key rules |
|---|---|---|
| Gloves | Barrier to blood/saliva | Change between patients; change if torn; do not wash and reuse exam gloves; hand hygiene after removal |
| Masks | Protect mucous membranes from splash/aerosol; source control | Change when wet/soiled; fit over nose and mouth; surgical masks for most dental procedures; higher-level respirators when indicated by pathogen/procedure policy |
| Eye protection / face shield | Protect conjunctiva | Side shields or full face shield for splash procedures; clean between patients |
| Gowns / protective clothing | Protect skin and street clothes | Fluid-resistant when heavy spray expected; change when visibly soiled |
| Clinic footwear / hair | Reduce contamination transfer | Covered shoes; hair secured out of field |
Glove notes high-yield for exams:
- Latex allergy awareness → non-latex alternatives (nitrile common).
- Gloves are not sterilized for routine exam use; sterile gloves for invasive surgery when indicated.
- Contaminated gloves do not replace hand hygiene.
Sequence concept: don PPE before contact with the contaminated field; doff carefully to avoid self-contamination (gloves often removed first in many protocols; follow current local training). Exam items usually test purpose and change rules, not a single universal donning script.
Spaulding Classification of Instruments and Devices
This is the decision skeleton for cleaning, disinfection, and sterilization.
| Category | Contact | Examples | Minimum process |
|---|---|---|---|
| Critical | Penetrates soft tissue, contacts bone, or enters bloodstream | Scalpel blades, periodontal scalers, surgical instruments, endodontic files (when used in canal), implant drills | Sterilization (heat preferred) |
| Semi-critical | Contacts mucous membranes or non-intact skin; does not penetrate | Mirrors, amalgam condensers, reusable impression trays, dental handpieces (treated as critical/semi-critical per guidance—heat sterilize between patients) | Sterilization preferred; high-level disinfection only if heat-sensitive and sterilization not feasible |
| Noncritical | Contacts intact skin only | Blood pressure cuffs, radiograph tube heads (barrier + wipe), light handles (barriers preferred), countertops | Intermediate- or low-level disinfection after cleaning; barriers reduce soiling |
Handpieces: modern infection-control teaching treats dental handpieces as requiring heat sterilization between patients after cleaning and lubrication per manufacturer—do not wipe-only a used handpiece and return it to the next patient.
Single-use devices (needles, prophylaxis cups, many burs labeled disposable) are not reprocessed—discard after one patient.
Instrument Reprocessing Workflow
- Point-of-use wipe/remove gross soil so bioburden does not dry.
- Transport in a rigid, leak-proof, labeled container—not loose in a pocket.
- Cleaning (ultrasonic, washer-disinfector, or manual scrub with care)—cleaning is prerequisite to sterilization; organic debris shields microbes.
- Inspection and packaging in pouches/cassettes with chemical indicators.
- Sterilization in a validated cycle.
- Storage of sterile packs dry, intact, away from contamination; reprocess if package wet, torn, or dropped.
Holding solutions keep instruments moist; they are not sterilants for critical items by themselves.
Sterilization Methods
Sterilization destroys all microbial life, including bacterial spores. Disinfection reduces pathogens but is not a spore-kill guarantee.
Steam under pressure (autoclave) — primary method
Saturated steam under pressure is the most common, preferred method for heat-stable critical and semi-critical instruments.
| Concept | Teaching points |
|---|---|
| Principle | Moist heat coagulates proteins; steam must contact all surfaces |
| Typical parameters (classic teaching ranges) | Gravity displacement often cited around 121 °C for ~15–30 min at ~15 psi, or 134 °C for shorter cycles (e.g., ~3–10+ min depending on load/type)—exact times are cycle- and load-dependent; know the concept of validated time–temperature–pressure, not one magic number for every load |
| Types | Gravity displacement vs pre-vacuum (prevac better steam penetration for wrapped loads/handpieces) |
| Advantages | Reliable, rapid relative to dry heat, non-toxic residual, penetrates well when air removed |
| Limitations | May corrode carbon steel if not dried/protected; some plastics/electronics heat-sensitive; wet packs are non-sterile storage failures |
| Loading | Do not overcrowd; hinge instruments open; packages not stacked to block steam |
Chemical vapor (chemi-clave concept)
Uses a chemical solution (historically formaldehyde/alcohol-type sterilants vaporized under pressure/heat) rather than pure water steam.
| Feature | Note |
|---|---|
| Advantage | Less corrosion of carbon steel instruments than moist steam in some classic comparisons |
| Limitations | Chemical odor/ventilation needs; special solution cost; not for all materials; must follow manufacturer cycle |
| AFK use | Recognize as an alternative heat-pressure method—not first-line for all practices today |
Dry heat
Hot air destroys microbes by oxidation; no moisture.
| Feature | Note |
|---|---|
| Classic parameters (order-of-magnitude teaching) | Higher temperatures and longer times than steam—e.g., concepts around 160–170+ °C for 1–2 hours depending on oven type/load (static vs forced air)—again, validated cycle matters |
| Advantages | No corrosion from moisture; good for oils, powders, some metal items that steam damages |
| Limitations | Long cycles; high heat damages many plastics; poor penetration of closed containers if misused; uneven heating if overloaded |
Other methods (recognition level)
| Method | Role |
|---|---|
| Ethylene oxide (EtO) gas | Low-temperature sterilization for heat-sensitive items in industrial/hospital settings; long aeration; toxicity concerns |
| Hydrogen peroxide gas plasma / vapor systems | Low-temperature hospital sterilizers for heat-sensitive devices |
| Liquid chemical sterilants (e.g., glutaraldehyde, peracetic acid concepts) | Immersion for heat-sensitive semi-critical items when heat sterilization impossible; time-critical; rinse; not ideal for packaged storage; staff exposure hazards |
| Flash / immediate-use steam sterilization | Emergency unwrapped cycles—not a routine substitute for full packaged processing |
Cold “sterilization” marketing claims for brief surface wipes are not equivalent to autoclave sterilization of critical instruments.
Monitoring the Sterilizer
Three complementary layers:
| Monitor type | What it tells you | Limitation |
|---|---|---|
| Mechanical | Cycle reached set time, temperature, pressure (gauges, printouts) | Does not prove kill of microbes if steam quality/load wrong |
| Chemical indicators | External tape/inks change with heat/steam exposure; internal multi-parameter indicators more informative | Indicate conditions met, not absolute sterility of every item |
| Biological indicators (spore tests) | Highly resistant spores (e.g., Geobacillus stearothermophilus for steam; Bacillus atrophaeus classically for dry heat/EtO) incubated after a test cycle | Gold standard of sterilizer efficacy; required on a regular schedule (commonly at least weekly in many dental infection-control recommendations, plus after repairs/new units—follow current local standards) |
Failed spore test: take sterilizer out of service, review loading/packaging/maintenance, retest, reprocess loads since last negative test per policy, fix before returning to use. Do not ignore a positive BI because “tape turned black.”
Disinfection Levels (Environmental and Noncritical)
After cleaning (remove soil):
| Level | Spectrum (concept) | Dental use examples |
|---|---|---|
| High-level disinfection (HLD) | Kills many microbes including mycobacteria; may not kill high numbers of spores with short contact | Heat-sensitive semi-critical items when sterilization not possible |
| Intermediate-level | Tuberculocidal; kills vegetative bacteria, most viruses/fungi; not reliable sterilization | Clinical contact surfaces contaminated with blood; operatory surfaces between patients (many hospital-grade intermediate disinfectants) |
| Low-level | Kills most vegetative bacteria and some viruses/fungi; may not be tuberculocidal | Housekeeping surfaces without blood; some noncritical equipment |
Clinical contact surfaces (light handles, chair switches, air-water syringe handles): prefer barriers changed between patients plus clean/disinfect at end of day or when visibly soiled; if no barrier, disinfect between patients with appropriate product and wet contact time.
Impression and prosthesis disinfection: rinse gross debris, disinfect per material compatibility (immersion or spray with timed contact), rinse again before lab send-out—protect the laboratory chain.
Waterlines, Aerosols, and Environmental Notes
- Dental unit waterlines can grow biofilm; use treated water systems, flushing protocols, and monitoring where required so coolant water meets potable-quality targets for non-surgical use; sterile water/solutions for surgical irrigation.
- Aerosol-generating procedures: high-volume evacuation, rubber dam when practical, pre-procedural rinse concepts, adequate ventilation.
- Radiology: barrier-wrap sensors/film holders; disinfect between patients.
Sharps Injury Prevention
| Practice | Detail |
|---|---|
| Engineering controls | Safety syringes/scalpels where available; sharps containers at point of use |
| Work practices | One-handed scoop if recapping unavoidable; pass instruments in neutral zone; never bend/break needles by hand |
| Container rules | Puncture-resistant, closable, upright, not overfilled |
| After injury | Immediate first aid (wash; mucous membrane flush), report, medical evaluation for post-exposure prophylaxis (PEP) decisions—especially HIV/HBV |
Bloodborne Pathogens
| Pathogen | Clinical relevance |
|---|---|
| HBV (hepatitis B virus) | Highly infectious in blood; vaccination of dental workers is a cornerstone control; survives on surfaces longer than many viruses |
| HCV (hepatitis C virus) | Bloodborne; no vaccine; standard precautions critical |
| HIV | Lower transmission risk per percutaneous injury than HBV in classic estimates, but serious; PEP timing matters after significant exposure |
| Other | Emerging pathogens, herpes viruses, mycobacteria—standard + transmission-based precautions as indicated |
Hierarchy of controls: eliminate hazard → engineering (sharps containers, safety devices) → administrative (policies, training, immunization) → PPE. Vaccination, training, and exposure response plans are part of professional duty, not optional extras.
Rapid review list
- Standard precautions for every patient
- Critical = sterilize; semi-critical = sterilize preferred; noncritical = disinfect
- Clean before you sterilize
- Steam autoclave first-line; dry heat/chemical vapor as alternatives
- Spore (biological) testing validates sterilizers
- Chemical indicators ≠ proof of sterility alone
- Never two-handed recap; report sharps injuries
- HBV vaccine + PEP pathways for bloodborne exposure
Section 23.2 shifts from technical safety to ethical principles that govern how dentists treat patients, data, and the public in Canadian practice.
According to the Spaulding classification, a periodontal scaler used subgingivally should be processed by which minimum standard?
Which statement best describes monitoring of dental sterilizers?
Compared with steam autoclaving, dry-heat sterilization is best characterized as:
A dental assistant sustains a needlestick after an injection. What is the most appropriate immediate management concept?