Infection Control in Prosthodontics
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Direct answer
No other dental speciality shuttles as much material between surgery and laboratory as prosthodontics, and every shuttle is a two-way transmission opportunity: impressions, wax rims, try-in dentures and casts all leave the mouth contaminated and all return to it. The framework is Spaulding's classification — critical items that enter tissue are sterilised, semi-critical items touching mucosa (impressions, dentures, mirrors) receive high-level disinfection, non-critical items touching intact skin need intermediate or low-level disinfection — executed with steam sterilisation at 121 degrees Celsius for about 15 minutes or 134 degrees for three to four. Prosthodontic practice then adds its own customs: impressions rinsed, immersed in 0.5% sodium hypochlorite for about ten minutes and labelled before dispatch, prostheses disinfected after every try-in, and the polishing lathe treated as the cross-infection site it quietly is, with fresh pumice and segregated wheels for incoming and outgoing work.
What you must remember
- Spaulding's three classes with prosthodontic residents: critical — surgical burs, scalpels, extracting forceps; semi-critical — mouth mirrors, impression trays, dentures and other mucosa-contacting items; non-critical — articulator components handled with gloves, light handles, blood pressure cuffs.
- Heat sterilisation parameters: autoclave at 121 degrees Celsius and 15 psi for about 15–20 minutes, or 134 degrees for 3–4 minutes; dry heat at 160 degrees for 30–60 minutes as the alternative; boiling water is disinfection at best and never adequate.
- Chemical tiers: 2% glutaraldehyde gives high-level disinfection in roughly 20–30 minutes and sterilisation only after about 8–10 hours of immersion; 0.5% sodium hypochlorite for about 10 minutes is the workhorse for impressions and surfaces.
- The impression protocol: rinse under running water, immerse (spray as fallback), rinse again, dispatch in a sealed bag labelled disinfected — and treat everything returning from the laboratory as contaminated in reverse.
- Try-in discipline: every denture, rim or framework that has been in a mouth is disinfected before it re-enters the laboratory and again before it re-enters the patient.
- The polishing lathe hazard: pumice slurry shared between contaminated and clean work is a bacterial culture medium; use freshly prepared pumice (ideally with an added disinfectant), dedicated or disinfected rag wheels, and clean the lathe regularly.
- Hepatitis B outranks HIV in resilience: HBV survives longer on surfaces and is the infection control benchmark organism, the reason vaccination and surface protocols exist.
- Indian framing: clinical waste follows the Biomedical Waste Management Rules colour-coding — yellow for contaminated recyclable-free waste, red for contaminated recyclables, with sharps in white puncture-proof containers — per current national rules.
A denture's round trip, traced
A try-in denture leaves the patient's mouth coated in saliva. At the chairside it is rinsed, immersed in glutaraldehyde or hypochlorite for the disinfection window, rinsed again, and placed in a sealed container marked disinfected for the technician. In the laboratory it is processed onto its final form — then, because laboratory benches are nobody's clean zone, it is disinfected again before returning. At delivery it is rinsed and inserted; at every subsequent adjustment visit the cycle repeats. Meanwhile, the cast was handled with gloves, the pumice was freshly mixed for outgoing work only, and the trimming burs were autoclaved between patients. Break any single link — the unlabelled impression, the shared pumice, the denture tried in "just quickly" between two patients without disinfection — and the chain is only as safe as that moment.
Where students slip
The recurring slip is treating disinfection as a one-way, one-time act: prosthodontic contamination flows surgery-to-laboratory and laboratory-to-surgery, and the try-in denture is the vehicle candidates forget. The second is classification confusion — assigning impressions to critical (they are semi-critical, since they contact mucosa without penetrating it) or quoting glutaraldehyde's sterilisation time as minutes instead of hours. The third is the lathe blind spot: the student who sterilises burs meticulously and then polishes every case in the same grey pumice has built the classic viva scenario, and the fresh-pumice-plus-segregated-wheels answer is what redeems it.
Frequently asked questions
What is Spaulding's classification with prosthodontic examples?
Critical items entering tissue (burs, forceps) require sterilisation; semi-critical mucosa-contacting items (impressions, dentures, mirrors) require high-level disinfection; non-critical skin-contact items need low-level disinfection.
What are the standard autoclave cycles?
Steam at 121 degrees Celsius and 15 psi for roughly 15–20 minutes, or the short cycle at 134 degrees for 3–4 minutes — with the time counted from full temperature and pressure.
How is 2% glutaraldehyde used in prosthodontics?
As a high-level disinfectant by immersion for about 20–30 minutes for heat-sensitive items and impressions, achieving sterilisation only after roughly 8–10 hours — with ventilation and PPE respected.
Why is the polishing lathe a cross-infection risk?
Shared pumice becomes a bacterial growth medium, and rag wheels carry organisms between patients; fresh disinfected pumice, segregated wheels and regular lathe cleaning interrupt the chain.
How is biomedical waste segregated in Indian dental practice?
Per the Biomedical Waste Management Rules colour-coding — yellow bags for soiled clinical waste, red for contaminated recyclable items, and sharps into white puncture-proof containers.