Brushing Buddy
Really young kids often have a hard time staying open for parents to brush their teeth properly.
One trick is to have two toothbrushes, put one toothbrush in, and when they are biting on that one, you can often sneak in a second toothbrush and brush the other side. Then, switch!
We sometimes have to use a mouth “prop”, which is a little sturdier, to keep the mouth open. We have seen this teether called the “Brushing Buddy” on Amazon, and it can be used as a teether, and it also has one side that functions as a mouth prop. It’s colorful, and non-threatening to kids. Here is an affiliate link to check it out: