As far as I know, there is no language requirement to apply for the equivalency process (AFK, ACS & ACJ). You can see that here is no mentioning for such a requirement on NDEB website.
I think after passing those tests (which seems to be very tough), you are required to prove English proficiency as a condition to be registered as a dentist and the type of the required english test (IELTS, Tofel, etc....) differs according to the regulations being effective in the province where you intend to practise.