if there’s a periodontal reason you need four cleanings per year (I’m assuming it has something to do with your gums) then your dentist should be able to make the argument that it’s preventive maintenance to the insurer and get the other two visits covered. if your dentist can’t or won’t do that it’s probably a sign that they’re not good patient advocates and you should find someone else.

no insurer will cover four cleanings a year unless your dentist fights for it, because private insurance is a Ponzi scheme that doesn’t work and needs to die.