Quick facts
- Impressions, prostheses, appliances and the items used to make them are treated as contamination risks in their own right: the Ontario standard of practice requires them to be handled "in a manner that prevents exposure of patients, OHCWs or the office environment to infectious agents".
- The obligation starts at the chair. Impressions, prostheses or appliances must be cleaned and disinfected as soon as possible after removal from the patient's mouth, before blood or other organic debris dries.
- A "wet" impression or appliance must be placed in an impervious bag before it is transported to a commercial dental laboratory.
- Heat-tolerant items used in the mouth, such as impression trays and face-bow forks, must be sterilized after each patient use.
- United States guidance adds the documentation step that is most often missing: when a case is sent off-site, the office should provide written information about the disinfectant and the exposure time used, and the laboratory should return the case in a tamper-evident container with the same information.
- Waste separates into three practical streams — general office waste, biomedical waste released to an approved carrier, and mercury-containing material that Ontario Regulation 347 names specifically for dental practices.
Most infection control writing stops at the operatory door. The laboratory side of the chain — the impression that leaves the chair, the prosthesis that returns, the bench that grinds and polishes, the gypsum, the burs and the mercury — has its own obligations, its own common failures and its own record fields. This article maps the dental laboratory chain link by link, with the obligation and its source for each step, and separates what the sending office owes from what the receiving laboratory owes.
Which items actually travel in this chain?
The chain is longer than most staff assume, because it includes items that never touch a patient directly but become contaminated anyway. Ontario's standard of practice names prostheses, appliances and the items used in their fabrication — impressions, occlusion rims and bite registrations — and extends the list to articulators, case pans, and the bench items used during adjustments: burs, polishing points, rag wheels, laboratory knives and dental lathes.
| Item | Departure point | What the source requires |
|---|---|---|
| Impression, occlusion rim, bite registration | Chairside | Cleaned and disinfected as soon as possible, before blood or organic debris dries; wet items bagged in an impervious bag for transport |
| Prosthesis or appliance being delivered | Laboratory or office | Delivered free of contamination, achieved with an appropriate low-level disinfectant by either the commercial laboratory or the office |
| Impression tray, face-bow fork | Chairside | Heat tolerated in the mouth; sterilized after each patient use |
| Articulator, case pan | Laboratory | Cleaned and disinfected according to the manufacturer's instructions |
| Burs, polishing points, rag wheels, laboratory knives, lathes | Laboratory | Cleaned and sterilized, cleaned and disinfected, or discarded after use, per the manufacturer's recommendations |
| Extracted tooth sent for shade or size comparison | Chairside | Cleaned and surface disinfected with an appropriate low-level disinfectant before it is sent |
Two features of that table drive most laboratory problems. The first is that heat tolerance, not patient contact, decides the route: a tray that never touches mucosa still has to be sterilized because it can survive the process. The second is that disinfection happens twice in the chain unless it is coordinated — once at the chair and once on arrival — and the standards explicitly warn against unnecessary duplication, because over-exposure damages impression materials and distorts the model the clinician depends on.
What has to happen before a case leaves the dental office?
The Ontario standard of practice is unambiguous about timing and about the reason for it. Impressions, prostheses or appliances must be cleaned and disinfected as soon as possible after removal from the patient's mouth, before the drying of blood or other organic debris; the manufacturer's instructions regarding the stability of specific materials during disinfection should be consulted; and wet impressions or appliances should be placed in an impervious bag prior to transportation to a commercial dental laboratory. The standard also sets the purpose of the whole exchange: effective communication and coordination between the office and the laboratory ensures that appropriate cleaning and disinfection happen at one end or the other, that materials are not damaged or distorted by excessive disinfectant exposure, and that disinfection is not needlessly repeated.
United States guidance covers the same ground and adds the two items Canadian staff most often have to reconstruct from memory. The CDC recommends that prostheses and prosthodontic materials — impressions, bite registrations, occlusal rims and extracted teeth — be thoroughly cleaned, disinfected with an EPA-registered hospital disinfectant having at least an intermediate-level activity (that is, a tuberculocidal claim), and thoroughly rinsed before being handled in an in-office laboratory or sent to an off-site laboratory. It then adds the documentation requirement: when a laboratory case is sent off-site, the office should provide written information about the methods used to clean and disinfect the material, naming the type of disinfectant and the exposure time.
| Step | The obligation | The step that gets missed | Record field it should produce |
|---|---|---|---|
| Immediately after removal | Clean and disinfect before debris dries | Waiting until the end of the appointment, or until the end of the day | Case identifier, time of removal, time of disinfection |
| Before transport | Seal wet items in an impervious bag | Sending wet impressions in an open tray or an unsealed bag | Transport method, bag type, whether the item was wet at dispatch |
| With the case | Provide written disinfection information when the case goes off-site | Assuming the laboratory already knows the office's protocol | Disinfectant name, concentration, exposure time, date |
| On return | Confirm who performed final disinfection | Neither party disinfects, on the assumption the other did | Tamper-evident container reference, party responsible for final disinfection, date received |
| At delivery to the patient | Ensure the finished prosthesis or appliance is free of contamination | Handling the finished item barehanded before it reaches the patient | Disinfection performed by, time, product used |
The CDC also describes what happens when the hand-off breaks down. If the laboratory staff performs the final disinfection, the client is to be provided with acceptable documentation of the disinfection method, and the item placed in a tamper-evident container before being returned to the office. If that documentation is not provided, the dental office is responsible for the final disinfection procedures. That single sentence is the reason the hand-off record matters more than the cleaning log: an undocumented step is an unperformed step in the judgment of whoever inspects the chain later.
What does the laboratory owe when the case arrives?
PPE comes first, and it stays on until disinfection is finished. The CDC recommends using PPE when handling items received in the laboratory until they have been decontaminated, and states that whether the work happens in the office or the laboratory, PPE should be worn until disinfection is complete. The same guidance sets the arrival sequence: before items are handled in the laboratory, clean, disinfect and rinse all dental prostheses and prosthodontic materials. Only after that does the technician work on them.
Three further laboratory-side obligations come from the same recommendations and are easy to lose in a busy bench workflow. Manufacturers must be consulted about the stability of specific materials, such as impression materials, relative to disinfection procedures. Heat-tolerant items used in the mouth, including metal impression trays and face-bow forks, must be cleaned and heat-sterilized. And item contamination on the bench is not exempt: burs, polishing points, rag wheels, articulators, case pans and lathes must follow the manufacturers' instructions for cleaning and sterilizing or disinfecting, and where those instructions are unavailable the fallback is to clean and heat-sterilize heat-tolerant items, or to clean and disinfect using a product with an appropriate level of activity for the degree of contamination.
| Laboratory-side exposure | Source of the obligation | Practical failure mode |
|---|---|---|
| Receiving and unpacking | PPE until items are decontaminated | Gloves removed before the bag is opened, or the same gloves carried to the bench |
| Pre-handling | Clean, disinfect and rinse prosthesis and prosthodontic materials | Disinfecting without cleaning first, so bioburden shields the surface |
| Materials advice | Consult manufacturers on material stability during disinfection | Choosing a disinfectant by habit rather than by compatibility with the impression material |
| Bench items | Clean and sterilize, clean and disinfect, or discard, per manufacturer instructions | The same rag wheel used across several cases in a day |
| In-office laboratory housekeeping | No eating or drinking in the in-office laboratory; hand hygiene after contact with laboratory materials and equipment | A coffee cup on the model bench, and hand hygiene treated as a patient-contact rule only |
Ontario's standard of practice also folds the in-office laboratory into the office's general rules: eating and drinking in operatories, instrument reprocessing areas and in-office dental laboratories is prohibited, and hand hygiene applies after contact with dental laboratory materials or equipment — a trigger that has nothing to do with a patient being present.
What is worth knowing about what survives on a model?
The clinical concern is not theoretical. CDC's 2003 guidance records that prostheses and impressions brought into the laboratory can carry bacteria, viruses and fungi, that the movement of oral organisms onto dental casts has been demonstrated, and that certain microbes have been shown to remain viable within gypsum cast materials for less than seven days. Incorrect handling of contaminated impressions, prostheses or appliances therefore offers an opportunity for transmission. Those citations are the reason the timing rule — disinfect before drying — is written as an imperative rather than as a convenience.
Reprocessing standards reinforce the same boundary from the device side. Provincial guidance for cleaning, disinfection and sterilization in all health care settings applies across settings that include dental offices, classifies devices such as dental handpieces as critical equipment that enters sterile tissue, and expects that staff involved in any aspect of reprocessing hold education and training specific to the device being reprocessed. Nothing in that scope exempts an appliance that travels between a clinic and a laboratory; the device simply changes hands.
Where does dental laboratory waste go?
The Ontario standard of practice divides waste from a dental office into two categories — biomedical waste and general office waste — and this is where a laboratory workflow generates streams that a purely chairside mental model does not anticipate. Biomedical waste is treated as hazardous waste, must not be placed with regular garbage, must be stored in colour-coded containers marked with the universal biohazard symbol, and must be released to an approved biomedical waste carrier. Anatomical waste, such as human tissue, is collected in a red liner bag labelled with the biohazard symbol and handled in accordance with Ontario Regulation 347. Non-anatomical waste, including sharps such as needles, scalpel blades and clinical glass, goes into a yellow puncture-resistant, leak-proof container labelled with the biohazard symbol, and only to an approved carrier once it reaches capacity.
| Stream from a laboratory workflow | Where it belongs | Source |
|---|---|---|
| Disposable trays, used impression material | General waste, provided it does not fall into a regulated category | CDC dental laboratory waste guidance |
| Burs, disposable blades, orthodontic wires | Puncture-resistant sharps container | CDC dental laboratory waste guidance |
| Extracted tooth without amalgam, being discarded | General office waste | RCDSO standard of practice |
| Extracted tooth containing amalgam | Mercury-containing waste | RCDSO standard of practice |
| Extracted tooth sent to a laboratory for shade or size comparison | Cleaned and surface disinfected before dispatch | RCDSO standard of practice |
| Discarded material containing mercury from a dental procedure | Common mercury waste under Ontario Regulation 347 | Ontario Regulation 347, definition of common mercury waste |
Ontario Regulation 347 defines common mercury waste to include discarded material that contains mercury from dental procedures carried out by a member of the Royal College of Dental Surgeons of Ontario, alongside mercury-containing switches, thermostats, lamps, thermometers and barometers. The same regulation sets out which wastes are hazardous waste, which are liquid industrial waste, and requires that syringes and other sharps at a waste facility be stored indoors in puncture-resistant containers that prevent exposure or spilling of the contents. Two practical consequences follow for a laboratory workflow: amalgam-contaminated scrap and disposable items belong to a named stream rather than to general waste, and the disposal routes for mercury, silver, lead and other chemicals are governed by provincial regulations and municipal bylaws rather than by clinical preference. The College publishes flowcharts for those streams on its own site; a laboratory that generates the scrap should be able to name the stream it uses and the carrier that collects it.
How is the laboratory chain different from the clinical chain?
The difference is one of custody, not of principle. In the clinical chain, the same team holds the instrument from contaminated to sterile and the record stays in one room. In the laboratory chain, the contaminated item crosses an organisational boundary — sometimes a legal one, when the commercial laboratory is a separate business — and the disinfection step can be performed by either party. That is why both the Ontario standard and the CDC guidance spend their words on the hand-off rather than on the chemistry: the failure mode is a gap between two parties who each believed the other had done it.
| Question | Sending dental office | Receiving dental laboratory |
|---|---|---|
| Who cleans first? | The office, as soon as possible after removal from the patient | — |
| Who disinfects before the technician works? | — | The laboratory, before any handling on the bench |
| Who documents the method? | The office, when a case goes off-site | The laboratory, on return, with documentation and a tamper-evident container |
| Who disinfects the finished appliance? | Either party, by agreement, with an appropriate low-level disinfectant | Either party, by agreement |
| Where do records live? | With the clinical record for the case | With the case file and the waste manifests |
A final wrinkle is jurisdiction. The weekly or daily language that surrounds sterilizer monitoring belongs to the sterilizer, not to the laboratory chain, and it differs by province and by country: in Ontario the standard of practice requires a biological indicator on each day the sterilizer is used and for each type of cycle used, and the weekly cadence familiar from United States guidance such as CDC and ANSI/AAMI ST79 is the United States comparison baseline rather than the Ontario requirement. A laboratory that also runs its own sterilizer sits under the same instrument-reprocessing expectations as the clinic it serves, and the appliances it produces are not exempt because they are made off-site.
Consumables are the part of the chain a laboratory reorders rather than redesigns: nitrile examination gloves for receiving and bench work, ASTM Level 3 procedure masks for the same tasks, an enzyme ultrasonic cleaning solution, 4 L concentrate where the laboratory cleans instruments alongside appliances, and Class 4 dual-indicator sterilization pouches for the items that return heat-sterilized. Facilities that want to see an indicator lot and its paperwork before standardising a monitoring routine can start with a five-pack indicator trial, and practices that run several chairs can compare case quantities through the CliniEco wholesale programme. Reselling? become a distributor.
Hand-off records and laboratory logs. The compliance log centre collects the printable records this chain depends on, including a case hand-off sheet, a daily biological indicator log and a waste stream checklist that can be printed and kept with the case file. Download the laboratory hand-off templates.
Check the chain against your own workflow. The same centre carries a self-check that walks each custody step from chairside removal to final delivery, so a gap between two parties shows up as a missing field rather than as an assumption. Run the laboratory chain self-check.
Have a question about your own facility? Send it in and you will get a written answer specific to your setup, with the regulation or standard it is based on cited. Ask your compliance question.
Related reading
- The full infection control chain in a dental clinic: sterilization, PPE, waste and surface disinfection in one map
- Dental laboratory disinfection: cleaning impressions without damage
- Case review: pouch seal failures at a dental laboratory
- Ultrasonic cleaner cross-contamination at a dental laboratory
Frequently Asked Questions
Who cleans and disinfects an impression, the clinic or the laboratory?
Both ends have an obligation, and they are different ones. The sending office must clean and disinfect the impression as soon as possible after it is removed from the patient's mouth, before blood or other organic debris dries, and must place a wet impression in an impervious bag before transport. The laboratory must clean, disinfect and rinse prostheses and prosthodontic materials before they are handled in the laboratory. Standards warn against unnecessary duplication, so the two parties have to agree where each step happens.
Do impressions need to be sterile?
No, and the distinction matters because sterilising an impression would destroy it. Ontario's standard directs that impressions, prostheses and appliances be cleaned and disinfected, with a disinfectant chosen with reference to the manufacturer's instructions on material stability. When an item does have to be sterile, it is the heat-tolerant hardware that carries the requirement, such as impression trays and face-bow forks, which must be sterilized after each patient use.
What documentation should travel with a case sent to an outside laboratory?
Written information about the cleaning and disinfection methods used, naming the type of disinfectant and the exposure time. United States guidance is explicit about this, and pairs it with the return journey: where the laboratory performs the final disinfection it should document the method and return the item in a tamper-evident container, and where that documentation is not provided the dental office is responsible for the final disinfection procedures.
How should extracted teeth be handled when they are sent to a laboratory?
They travel with the case, not with the sharps. Ontario's standard directs that an extracted tooth sent to a dental laboratory for shade or size comparison be cleaned and surface disinfected with an appropriate low-level disinfectant. Where a tooth is discarded rather than sent, one without amalgam may go into general office waste, while one with amalgam fillings is treated as mercury-containing waste. United States guidance additionally directs that extracted teeth containing amalgam not be placed in regulated medical waste intended for incineration, and that teeth cleaned for transport to an educational institution or a dental laboratory be kept hydrated in a leakproof container labelled with a biohazard symbol.
Are the burs, rag wheels and lathes on the bench subject to the same rules as instruments?
Yes, in substance. Ontario's standard of practice lists burs, polishing points, rag wheels, laboratory knives and dental lathes among the items that frequently become contaminated during adjustments, and requires that they be cleaned and sterilized, cleaned and disinfected, or discarded after use, as the manufacturer recommends. United States guidance reaches the same result and adds a fallback for the case where manufacturer instructions cannot be obtained, which is to clean and heat-sterilize heat-tolerant items or to disinfect at a level appropriate to the degree of contamination.
Can compliance be demonstrated without a separate laboratory record system?
It can, but not without fields that capture custody. The gaps that inspections and internal audits tend to surface are not chemical — they are the case identifier, the time the item left the patient, the disinfectant and exposure time used, the party responsible for final disinfection, and the waste stream used for the scrap. Those five fields can live inside an existing case file; what they cannot do is live only in staff memory.
Do the same rules apply in every province and in the United States?
The principles travel; the citations do not. Ontario's obligations come from the College's standard of practice and from Ontario Regulation 347 for mercury and other regulated wastes. United States guidance comes from CDC's dental infection control recommendations, which reference the EPA-registered disinfectant categories and, for undecanted materials shipped off-site, United States Department of Transportation rules on infectious substances. Facilities that work across a border should cite the instrument that applies to the physical location of the step, not the location of the head office.
Sources
- RCDSO, Standard of Practice: Infection Prevention and Control in the Dental Office, v3, including the dental laboratory asepsis and waste sections (PDF)
- RCDSO, infection prevention and control standards and advisories index
- CDC, Guidelines for Infection Control in Dental Health-Care Settings, 2003, MMWR 52(RR-17) (PDF)
- CDC, Guidelines for Infection Control in Dental Health-Care Settings, 2003 (web edition)
- Ontario Regulation 347, General — Waste Management, current consolidation via the Ontario e-Laws data service
- Public Health Ontario, provincial guidance for cleaning, disinfection and sterilization in all health care settings (PDF)
- ISO 17664-1:2021, information to be provided by the medical device manufacturer for the processing of medical devices, preview (PDF)
- ISO 17665:2024, moist heat sterilization, preview (PDF)
- CSA Group, CAN/CSA-Z314, medical device reprocessing in all health care settings
- ANSI/AAMI ST79, comprehensive guide to steam sterilization and sterility assurance in health care facilities
- CDC, Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008
- CliniEco Medical, dental compliance hub
CliniEco Medical supplies infection control consumables to Canadian dental practices and dental laboratories under MDEL #35334.
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