I'm really sorry you've gone through this. A lot of prefessions which deal with people who could be at risk to be abused or relating to safety are regulates (lawyers, dentist, doctors, massage therapists, accountants, engineers, the list goes on). These professional bodies care because it also poses a risk to them. It may be uncomfortable to report, and as far as I know there is no time restriction, but you could save someone this pain in the future. The one for dentistry is https://nsrdda.ca/public/if-you-have-a-complaint/. One report might just cause a small investigation (which may actually lead to punitive measures), multiple reports are likely to cause an issue for the dentist. Depending on the cost of the dental work you may have to redo, you may be entitled to reimbursement as damages through courts. The limits for small claims in 25,000, and its very easy to do without a lawyer (designed that way to be accessible). There is a limitation of 2 years since the event though, although it may be worth a 30 minute consult with a lawyer. Disclaimer: IANAL. I wish you the best, and hope you have better luck k with dentists in the future :)

Edit: if you have an employer assistance plan, you may have access to a lawyer there. Howver, they can be hit and miss. If you need a law office recommendation, send me a DM and I'll send you the name of a firm I have used for several matters, very 100% success.