He’s 18 months old and fights having his teeth brushed so much. The front of the bottom are almost impossible to get and I noticed this build up recently. I’ve tried flossing and wiping it with a rag, can’t seem to get that off no matter what. Is it tartar? Is he too young for the dentist to do a proper cleaning? I’m so worried about it

Edit: he has been to the dentist before. I was asking if they will bother cleaning baby teeth. I took him in January and they barely looked in his mouth for 5 seconds. I feel like they could have caught this earlier if they looked a little better