9.2 Dental Laboratory and Prosthodontic Infection Prevention

Dental Laboratory and Prosthodontic Infection Prevention

An impression, bite record, appliance, or prosthesis can carry saliva and blood from the operatory into an in-office or commercial laboratory. The return trip can carry laboratory contamination back to the patient. A safe system defines who cleans and disinfects each item, which compatible product is used, and how the receiving party knows the item’s status.

Classify Items by Patient Contact

• Critical instruments penetrate soft tissue or bone. Bone-cutting trephines and surgical burs are examples; clean, package, and heat sterilize them when reusable and heat-tolerant. A trephine is an instrument used during implant surgery, not itself an implantable device.
• Semicritical items contact mucosa without penetrating it. Impression trays, facebow forks, reusable bite-registration devices, and patient-contact parts of prosthetic workflows are semicritical. Heat sterilize heat-tolerant items. For heat-sensitive items, use the manufacturer-validated high-level-disinfection method or a single-use alternative.
• Noncritical equipment contacts intact skin or only environmental surfaces. Articulator frames, transport pans, model trimmers, and lathe housings are cleaned and disinfected according to contamination, material compatibility, and the environmental-product label.

Do not assume that every surgical guide is critical or every plastic tray is disposable. Its intended tissue contact and labeling determine the classification and process.

Impressions and Bite Records

Clean an impression promptly enough to prevent soil from drying, while avoiding a method that damages fine detail. Then use an EPA-registered hospital disinfectant with a label claim and application compatible with the impression material, and follow both the material and disinfectant instructions for concentration, application, contact time, rinsing, and storage.

Alginate, polyether, polyvinyl siloxane, polysulfide, and impression compound have different water absorption and dimensional-stability limits. A generic “ten-minute soak” or a universal 1:10 bleach recipe can distort one material even if another tolerates it. Spray, immersion, sealed-bag contact, or another technique is acceptable only when the relevant manufacturers validate it.

After treatment, rinse or dry only as directed and label the item’s decontamination status. Prevent the clean impression from touching the contaminated sink, shipping container, or counter. A reusable tray is reprocessed separately according to its Spaulding classification and IFU.

Wax rims and bite records can soften or distort with heat or chemicals. Use a compatible method and avoid prolonged contact not supported by the material manufacturer. Facebow forks that enter the mouth are semicritical and should be heat sterilized if heat-tolerant; the external facebow frame is handled according to its contact and IFU.

Casts, Appliances, and Prostheses

A stone cast poured from a properly decontaminated impression begins clean, but trimming, adjustment, try-in, or contact with contaminated hands can recontaminate it. If a cast or model needs decontamination, choose a method compatible with gypsum and the case materials. Excess liquid can erode surfaces or change dimensions, so an operatory-surface recipe is not automatically suitable.

A denture, partial, retainer, occlusal guard, or repair appliance coming from a patient is cleaned and disinfected before laboratory adjustment. Select a product compatible with acrylic, metal, soft liner, attachment, and implant component. Chlorine may corrode metal; heat may distort acrylic; alcohol or other solvents may craze some polymers. After adjustment, clean and disinfect the item again before it returns to the patient if the laboratory process contaminated it. Rinse off chemical residue when the product and device instructions require it.

Never place a patient appliance directly into a communal ultrasonic tank. Use a dedicated container or beaker system and a solution validated for the appliance, preventing the tank fluid from becoming a cross-patient reservoir. Time and chemistry follow the equipment, solution, and appliance instructions—not a universal 10-to-15-minute rule.

Lathe, Pumice, and Polishing Controls

The polishing lathe can spread microorganisms through wheels, pumice slurry, aerosols, and hand contact. Establish a clean/dirty workflow:

1. Clean and disinfect the patient appliance before adjustment.
2. Use fresh, unit-dosed pumice or polishing material for one patient rather than a communal wet pan.
3. Use a new single-use wheel or clean and heat sterilize a reusable heat-tolerant rag wheel, bur, polishing point, or laboratory knife between patients according to its IFU.
4. Use shields, local dust collection, and eye/face and respiratory protection selected from the dust, splash, and chemical hazard assessment.
5. Discard the patient-specific slurry and clean the pan and work surfaces after the case.

Sterile water is not a universal requirement for pumice, and adding bleach to slurry is not a substitute for unit dosing and validated reprocessing. Never mix a disinfectant into pumice unless both the polishing material and appliance manufacturers permit it.

Communication with an Off-Site Laboratory

The dental office and laboratory need a written protocol that prevents both missed disinfection and unnecessary repeated chemical exposure. Before shipment, clean and disinfect items according to their compatible method. Use a container that prevents leakage and protects the item from damage. Communicate whether the item was decontaminated, the method used when the laboratory needs that information, and any remaining hazard.

The receiving laboratory should treat unclear items as contaminated and contact the sender rather than guess. The laboratory also decontaminates patient-contact items before return when its processing may have contaminated them. A biohazard label is used when required for a package containing blood or OPIM; it is not a routine substitute for cleaning and disinfection. Follow carrier, OSHA, state, and local rules for any regulated shipment.

Worker Protection

Laboratory work can create projectiles, acrylic monomer vapor, metal or silica-containing dust, and contaminated splatter. The exposure-control and hazard-communication programs identify needed ventilation, local exhaust, guards, SDS precautions, and PPE. Utility gloves suit cleaning or contaminated-sharp handling; task-appropriate eye/face protection is needed at lathes and trimmers. Select respiratory protection through the hazard assessment, and implement an OSHA respiratory-protection program when respirators are required.

The exam-safe rule is a two-way barrier: decontaminate before transfer, communicate status, prevent laboratory cross-contamination, and decontaminate again before patient use when needed.