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Cannabis: When Are You Considered Legally Impaired?

Dr. Aaron Burry is Associate Director of Professional Affairs here at the Canadian Dental Association; and my colleague on the cannabis file. In an effort to round up the perspectives and the implications of the legalization of Marijuana on the dental profession, Aaron and I thought of bringing this conversation to the attention of our audience: you the dentist. It is important to know when to refrain from treating patients and when a patient is not a good candidate for treatment due to substance impairment. 

We hope you benefit from this conversation. We would like to hear from you and know your thoughts and questions about the legalization of cannabis. If you wish to reach us, it’s quite easy: email us at oasisdiscussions@cda-adc,ca or call our toll-free number 1-855-716-2747.

Until next time!

Chiraz Guessaier, CDA Oasis Manager


When is a dentist considered legally impaired and do we have guidelines or standards to say, here is where and when I shouldn’t treat a patient or here’s where, when I’m not supposed to practice?

It’s been a long-standing element of most ethical guidelines for practice that practicing while under the influence or being intoxicated is considered inappropriate and would be professional misconduct. the question is now that cannabis will be legal, what is the level of consumption that would be constitute impairment? And with a combination of alcohol and cannabis, the question becomes what are the different levels of impairment for that combination?

What should a dentist do if he or she suspects that a patient is impaired? How should they communicate with the patient and would it be considered as a refusal of treatment if I opt not to treat the patient? 

You should develop an approach where you start with a conversation. Rather than relying on medical histories, you should fill out the medical history together with the patient which should give you a good sense of where they’re at cognitively. You should establish a rapport with the patient in a non-judgmental and open way that will allow them to disclose any information that may have an impact on treatment, such as cannabis consumption. 

If a patient has had a fair amount of cannabis that may impact treatment, you should advise that treatment should be deferred. This does not constitute refusal of treatment. rather, you are advising the patient of a potential health risk and requesting that they come back at a later time for treatment. 

Interview Transcript

Cannabis: When Are You Considered Legally Impaired? (PDF)

Oasis Moment (3.09″)


Full Conversation (10.54″)



  1. Simi Silver July 6, 2018

    When will dentists be able to prescribe cannabis for pain?

  2. Simi Silver July 18, 2018

    Again I must speak up. To focus on the impairment and not on the AMAZING benefits of cannabis is dreadful and a disservice as healthcare providers. Also to refer to some “24 hour” rule is like referring to the “3 second” rule for eating food that has dropped on the floor; ie, it is not a rule and has no basis in any science.


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