Infection Control and Safety
What this domain tests
How the laboratory breaks the chain of cross-infection between clinic and bench, plus the occupational hazards specific to a dental lab.
Core rules
- Spaulding classification. Critical items (penetrate tissue) require sterilization; semicritical items (contact mucosa) require sterilization or high-level disinfection; noncritical items require low-level disinfection. Impressions, models and prostheses arrive as semicritical items.
- Impression handling. Rinse under running water to remove visible blood and saliva, disinfect with the material-compatible agent and contact time specified by the manufacturer, bag with a dated label, then pour. Prolonged immersion degrades alginate and some polyethers.
- Sterilization monitoring. Gravity autoclave at about 121 °C, 15 psi, 15 minutes, or 132–134 °C for a shorter cycle. Use a chemical indicator in every load and a biological indicator (Geobacillus stearothermophilus) at least weekly and after any failed load.
- Bench hygiene. Fresh pumice per case, disinfect the lathe and handpieces, no food or drink at the bench, hand hygiene before and after glove removal.
- Occupational hazards. Silica and gypsum dust - wet trim and use local exhaust; beryllium and nickel in base-metal alloys - extraction ventilation and dust masks; monomer vapour - fume extraction; sharps from broken blades and burs.
Worked example
An alginate impression arrives with visible blood. Rinse it, then disinfect with the approved agent for the full contact time, bag and label it with patient identifiers and the date. Do not pour it first and disinfect the model afterwards: the contaminated impression has already contaminated the bench, and a disinfected model does not clean the impression.
Traps that cost marks
- Pouring an impression before disinfection.
- Substituting a quick wipe for the specified contact time.
- Relying on chemical indicators alone for sterilizer assurance.