Quick facts
- A bite block is the part of an intraoral X-ray positioning system that the patient bites on to hold the receptor steady at a fixed angle to the beam.
- United States: the positioning device is filed as a dental x-ray film holder, a Class I device under 21 CFR 872.1905, defined as a device intended to position and to hold x-ray film inside the mouth, and it is exempt from premarket notification procedures subject to the limitations in the part.
- Canada: Health Canada's Safety Code 30 (2022) is the national guidance on radiation protection in dentistry, covering the installation, use and control of dental X-ray equipment.
- Ontario applies the Healing Arts Radiation Protection Act with the X-ray safety code in R.R.O. 1990, Reg. 543, which sets out equipment construction, operator protection and exposure limits including a table of maximum entrance exposure for posterior bitewing projections.
- Positioning is a radiation-protection control, not a comfort accessory. A holder that keeps the receptor parallel to the beam and the patient steady is what makes a retake unnecessary.
A bite block is the intraoral positioning device a dental team uses to hold an X-ray receptor in a fixed relationship to the beam while the exposure is made. It looks like a small piece of plastic, and it is bought in boxes of a hundred, but it sits at the intersection of two rulebooks: the device rules that decide what the product is, and the radiation protection rules that decide how the exposure is taken and documented. Canada and the United States organise those two rulebooks differently, and the difference shows up in what a clinic files and what it records.
What is a bite block, and what does it do in an intraoral exposure?
The positioning system has three parts that work together: the bite block the patient closes on, the arm or aiming ring that fixes the beam direction, and the receptor holder that keeps the film or sensor parallel to the tooth.
Each part solves a specific problem.
The bite block stabilises. Patient movement between positioning and exposure is one of the ordinary causes of a blurred image. A block the patient can close on steadily removes most of that movement.
The holder sets the geometry. Positioning the receptor parallel to the long axis of the tooth and aiming the beam perpendicular to both is what produces an image with minimal distortion. A holder that cannot repeat that geometry produces images that cannot be compared with the previous set.
The aiming ring sets the angle. Where the system includes one, it removes the guesswork from the cone position, which matters for the bitewing projections where the beam has to pass between the teeth.
| Component | Function | Failure mode when missing |
|---|---|---|
| Bite block | Stabilises the receptor in the patient's mouth | Movement blur on an otherwise correct exposure |
| Receptor holder | Keeps the receptor parallel to the tooth | Elongation and foreshortening |
| Aiming ring or arm | Fixes the beam angle | Cone cut and repeated exposure |
| Barrier sleeve | Infection control between patients | Cross-contamination and a failed audit finding |
The last row is the one clinics forget to order. The holder is a semi-critical item because it contacts mucous membranes, so it needs a barrier or a reprocessing routine between patients, exactly like other intraoral items.
Is a bite block regulated as a device, and in which class?
In the United States, the answer is written plainly in the regulation. A dental x-ray film holder is "a device intended to position and to hold x-ray film inside the mouth", and it is a Class I device under 21 CFR 872.1905. The same section states that the device is exempt from the premarket notification procedures in subpart E of part 807, subject to the limitations in the part, and that if the device is not labelled or otherwise represented as sterile it is also exempt from quality management system requirements except for records and complaint files.
The X-ray source itself is a different device. An extraoral source X-ray system, defined in 21 CFR 872.1800 as an AC-powered device that produces x-rays and is intended for dental radiographic examination and diagnosis of diseases of the teeth, jaw and oral structure, follows its own pathway through the FDA classification database and, where required, premarket notification.
In Canada, a positioning device is an accessory to diagnostic imaging equipment and is placed on the market under the Medical Devices Regulations (SOR/98-282), where the class determines the pathway: a Class I device through an application under section 45 for an establishment licence that authorises the holder to sell or import the device, and a Class II, III or IV device through an application under section 32 for a device licence.
| Item | Canada | United States |
|---|---|---|
| What the positioning device is | Accessory to diagnostic imaging equipment | Dental x-ray film holder |
| Classification | Class determined under the Medical Devices Regulations | Class I under 21 CFR 872.1905 |
| Market pathway | Establishment licence for Class I; device licence for higher classes | Exempt from premarket notification, subject to the part's limitations |
| The X-ray source | Device under the Medical Devices Regulations | Extraoral source x-ray system under 21 CFR 872.1800 |
| Public record | Health Canada establishment licence register | FDA classification, registration and listing databases |
The practical consequence for a buyer is modest but real. A Class I exempt positioning device does not come with a 510(k) clearance number, and asking a supplier for one produces a blank look rather than a document. In Canada, the question is whether the seller holds the establishment licence for a Class I article.
What do the radiation protection rules require, and how do the two countries differ?
This is where the two systems diverge most, because the United States runs radiation control mainly at state level while Canada has national guidance plus provincial law.
Canada's national document is Safety Code 30, published by Health Canada as Radiation protection in dentistry: safety procedures for the installation, use and control of dental X-ray equipment, in the 2022 edition. It is guidance directed at the safe installation, use and control of dental radiographic equipment, and it is the reference a Canadian dental office works to when it writes its radiation protection procedures.
Ontario adds statute and regulation above that national guidance. The Healing Arts Radiation Protection Act governs the use of X-ray equipment in the healing arts, and the X-ray safety code in R.R.O. 1990, Reg. 543 sets out requirements for equipment construction and operation, including a warning sign at the control panel or exposure switch location stating that unauthorised use is prohibited and that hazardous radiation is emitted when the machine is activated. The regulation also carries exposure tables; for posterior bitewing projections it lists maximum entrance exposure values against peak kilovoltage settings, from 550 milliroentgens at 50 kVp down to 220 milliroentgens at 90 kVp.
In the United States, dental radiography is regulated through the FDA's device framework for the equipment itself, through guidance from the American Dental Association on radiographic practice, and through state radiation control programmes that licence equipment and set operator requirements. The ADA's oral health topics library is the practical starting point a US practice uses, and the FDA device classification database is where the positioning device and the X-ray source are recorded.
| Item | Canada | United States |
|---|---|---|
| National guidance | Health Canada Safety Code 30 (2022) | FDA device framework and ADA guidance |
| Provincial or state layer | Ontario: HARP Act with R.R.O. 1990, Reg. 543 | State radiation control regulations |
| Device record | Health Canada establishment licence register | FDA classification, registration and listing databases |
| Exposure table example | Posterior bitewing maximum entrance exposure set against peak kVp | Set by state regulation and equipment design |
| Positioning device status | Accessory to diagnostic imaging equipment | Class I dental x-ray film holder, exempt from premarket notification |
| Infection control | Semi-critical item requiring a barrier or reprocessing | Semi-critical item requiring a barrier or reprocessing |
The part of the divergence that costs money is the fourth row. A retake is not free: it is a second exposure for the patient and a second unit of chair time. Parallel positioning with a holder is the lowest-cost way to reduce retakes, which is why the box of bite blocks is a radiation protection purchase rather than a stationery purchase.
How should positioning devices be handled between patients?
The device contacts mucous membranes, so it sits in the semi-critical category and needs a defined routine.
- Barrier sleeves. Where the design allows, a disposable sleeve over the holder and a fresh sleeve per patient is the quickest compliant routine.
- Reprocessing where required. Some designs are cleaned and sterilized to the clinic's validated cycle rather than sleeved, and the choice has to match the manufacturer's instructions.
- Single-use bite blocks. A disposable block removes the reprocessing question entirely and is the usual choice in high-volume practices.
- Hand hygiene and gloves. The positioning sequence is a patient contact, so it belongs inside the clinic's hand hygiene routine rather than outside it.
- Documentation. If the clinic claims a barrier routine, the audit trail has to exist: what is sleeved, what is reprocessed, and who checks the stock.
What else belongs in the radiography consumable line?
The positioning items travel with a small cluster of consumables that run out at the same time: dental bibs for the patient, barrier sleeves, surface disinfectant wipes for the tube head and control panel, gloves, and the masks and eye protection the operator wears for every exposure. Holding them on one standing order is what keeps a room available on a busy afternoon.
For a multi-chair practice, standardising on one positioning system across rooms also simplifies training, because the geometry staff learn in one room is the geometry they use in the next.
Sources
- 21 CFR 872.1905, Dental x-ray film holder
- 21 CFR 872.1800, Extraoral source x-ray system
- Health Canada, Safety Code 30 (2022), Radiation protection in dentistry
- Healing Arts Radiation Protection Act, R.S.O. 1990, c. H.2
- R.R.O. 1990, Reg. 543, X-ray safety code
- RCDSO, Infection prevention and control: instrument categories and reprocessing principles
- RCDSO, Standards and guidance
- RCDSO, News and standards updates
- Medical Devices Regulations, SOR/98-282
- FDA, Medical device classification database
- FDA, Device registration and listing database
- FDA, Premarket notification 510(k) database
- American Dental Association, Oral health topics
- American Dental Association, Oral health topics, fluoride
- Canadian Dental Association
- FDI World Dental Federation
- Public Health Ontario, PIDAC provincial guidance for cleaning, disinfection and sterilization in health care settings
Ordering for a dental clinic, group or care home? Wholesale and multi-site ordering covers account setup and case pricing, and the B2B wholesale collection lists the lines stocked for institutional buyers. Sites that also run an in-house sterilizer can start with the biological indicator 5-pack trial.
Related reading
- Dental dam isolation materials: which rules apply in Canada
- Case review: how a multi-chair dental clinic recovered from a failed sterilization audit
- Medical supplies Ontario: a procurement guide for clinics
Frequently Asked Questions
What is a dental bite block used for?
It is the part of an intraoral positioning system the patient bites on to hold the X-ray receptor steady while the exposure is made. It stabilises the receptor, the holder keeps it parallel to the tooth, and an aiming ring fixes the beam angle.
Is a bite block a regulated medical device?
In the United States it is filed as a dental x-ray film holder, a Class I device under 21 CFR 872.1905, and it is exempt from premarket notification procedures subject to the limitations in that part. In Canada a positioning device is an accessory to diagnostic imaging equipment placed on the market under the Medical Devices Regulations, with the class determining whether an establishment licence or a device licence applies.
What does 21 CFR 872.1905 say a dental x-ray film holder is?
It defines the device as one intended to position and to hold x-ray film inside the mouth, classifies it as Class I with general controls, and states that it is exempt from the premarket notification procedures in subpart E of part 807 subject to the limitations in § 872.9.
What is Safety Code 30?
It is Health Canada's guidance document on radiation protection in dentistry, subtitled safety procedures for the installation, use and control of dental X-ray equipment, in its 2022 edition. It is the national reference a Canadian dental office works to when it documents its radiographic procedures.
Does Ontario regulate dental X-rays separately?
Yes. Ontario applies the Healing Arts Radiation Protection Act together with the X-ray safety code in R.R.O. 1990, Reg. 543, which sets requirements for equipment construction and operation and includes exposure tables, such as maximum entrance exposure values for posterior bitewing projections at specified peak kilovoltage settings.
How should bite blocks be handled between patients?
As semi-critical items, because they contact mucous membranes. The usual routines are a single-use block, or a disposable barrier sleeve over a reusable holder, or cleaning and sterilization where the manufacturer's validated instructions call for it. Whichever routine is chosen has to be documented.
Why does a positioning system reduce radiation dose?
Because a retake is a second exposure. When the receptor is parallel to the tooth and the beam angle is fixed, the image is diagnostic first time more often, and the number of repeated exposures falls. That is why a holder is a radiation protection purchase rather than a comfort accessory.
CliniEco Medical supplies dental bibs, positioning accessories, barrier and surface consumables, gloves and the wider clinic consumable lines described in this article. Health Canada MDEL #35334. This article is written for dental, clinic and procurement professionals and is not clinical guidance; radiographic technique and radiation protection decisions belong to the treating dentist and the clinic's radiation protection officer.
0 comments