Let me summarize.
In the US, an undergraduate degree is not completely specialized. Students study lots of things outside their "major". So, graduate programs don't expect as much specialized knowledge of an incoming student as might be typical in other places.
As most places, psychiatry is a medical profession and the normal path is to get a medical degree, say an M.D., and then specialize in psychiatry beyond that. Medical schools might require a number of science courses for entry, however, especially chemistry and biology. A dentistry undergraduate degree might already include those. Otherwise you have a deficit and a harder path. And the path is quite long in any case. In the US, a psychiatrist would require a license as well as a degree in order to practice. I don't know what that entails, but probably at least an examination. But a researcher, as opposed to a practitioner, might not need a license.
I think the Canadian educational system is similar in some ways to the US system, but I'm not sure it is similar enough to help in your case, especially for medical school. But it might be worth an initial search to discover the options.
But look for medical schools that have an option for a psychiatry specialization.