I also have tightly packed teeth and can barely use interdental brushes on just some of them. What works well however are dental floss sticks, you can get them with pretty thin floss(es?) and they're way easier to use than plain floss.

The only interdental brush I find I can use is Piksters. All the others bend so easily.

I wish they were cheaper.

my dentist recommends the waterpik instead of flossing, he says floss can damage tissue if this is the case.

I can get floss in between mine, but my dentist says that tighter together teeth get less food stuck in there (although I'm sure there are different levels where it can start to be bad)

Try the pink interprox ones. They are the thinnest ones.

Otherwise ask your dentist if they can show you how to use them. Just because your teeth are really tight together doesn't mean that there won't be any buildup of food or other things.

Oral b pro glide works well. Pay for the more expensive floss and you won't have this issue as much.

There are other forms of flossing strings for this problem. Have the same problem and i would never go back to normal string again