Why Don’t Dentists Use Rectangular Collimation for Intraoral X-Rays?

The ADA just recommended that dentists use rectangular collimators on intraoral x-rays.  Why do the states disagree?

A rectangular collimator is typically an adapter that can be placed over the round cone of a dental intraoral x-ray source that limits the radiation being emitted to a smaller rectangular shape.  The purpose is to reduce patient radiation by limiting the x-ray to only the radiation that will hit the sensor (or film).

In February, the Journal of the American Dental Association published new recommendations aimed at enhancing radiation protection in dental radiography and cone-beam computed tomography (CBCT). They did this in partnership with the FDA. 

(see more detail here)

One of the recommendations is to use rectangular collimation for intraoral imaging because it has been shown to reduce effective dosage to patients “by more than 40%”.

But there is only one problem.

Dentists can’t get rectangular collimators.

At the time that the ADA published their report, there was only one state that required rectangular collimation on dental x-ray machines:  Colorado.  Ironically, that same month, the Colorado Board of Health rescinded this requirement.

The reason?     “…distributors and manufacturers have universally indicated that the add-on collimator devices envisioned by the current rule have been discontinued, are no longer being manufactured, and are not available for purchase on the open market. While some web sites continue to advertise the devices, the reality is that they are not available.”

The main reason that offices have stopped using them is that rectangular collimators can make it harder for the staff to take consistently diagnostic images.  This is because a rectangular collimator results in less margin for error in capturing the desired anatomy.  There is a higher probability of cone cut because the x-ray source must be more precisely aimed to hit the receptor.