The best thing that I have found is beef femur bones. You can get them at most butcher counters, but you may have to ask so that they can order them. Not cooked, raw. The raw bones don’t splinter and are safer for the dog.
If your dogs aren’t used to this type of food, then I would watch out for stomach upset (diarrhea) when you give them these bones.
In my experience, these works extremely well at keeping the teeth clean and healthy.
In the past I would give them raw bones from the butcher counter. The dogs loved them and they kept them quiet for hours until one wanted what the other had. 
But I stopped because I was worried about them cracking their teeth. They’ve also had every other thing that has been mentioned.
Yesterday I bought each of them their own Nylabone - bison flavored for power chewers. They actually seem to like them but the bones are really hard.
After the visit to the dental vet, I’m skittish. But it looks like everyone here gives their dogs chew bones, etc. that she would not approve of. The vet would scold all of you! 
I think I’m going to just not worry about it anymore and let them chew to their hears’ content.
I’ll look into that Bullibone for Pluto, though he hasn’t shown much interest in flavored Nylabones in the past.
He does love Dentastix, which have been good for keeping his teeth clean and breath fresh. They of course are chewed and eaten in less than a minute.
I can think of 2 or 3 people I’d like to dress up in a “bone suit” and send to your dog. LOL
All out of postal delivery people?
I forgot to mention that on the back of the Nylabone package is stated that it is veterinarian approved. And there was a picture of a woman in a white lab coat next to the statement. That’s all I needed to be convinced. The boys can now have Nylabones! 
Really sorry to be a downer, but different dogs chew at very different intensities and in different ways – gnawing vs. crushing. If you have a dog who you know breaks his teeth on hard bones, I wouldn’t give him hard bones.
Let me relate a Nylabone anecdote.
I had a Golden mix who was a big chewer. At one point, I bought her a Nylabone, and she proceeded to chew the bone “nubs” off, leaving a rectangular piece of nylon around 1/2" x 3". One day, it disappeared. We looked all over, and couldn’t find it, and figured that she had taken it out into the yard and lost it. Then, a few days later, it reappeared, in the middle of a mess of dog-puke.
That was the end of Nylabones for her…
Our previous dog had jaws that were evidently stronger than his teeth. When he was young we took him in for a regular exam and the vet noticed one of his molars was shattered - like half of it was missing (!), exposing the nerve (!!). Of course he had not led-on how much pain and discomfort that may have been causing him, so we never noticed it or how long it had been like that. After we had the rest of the tooth extracted we were more mindful of his chew toys. I think he was okay with the nylabones - he’d work-off tiny/small pieces but never break-off chunks, like @beowulff mentioned, and never had any more dental issues. We did give him bully sticks and those Greenies dental chews, which are relatively soft, but abrasive enough to somewhat clean his teeth.
I am lucky to be in a country where I can get ostrich thigh bones.
The one dog looks at them, like many things in his very simple life, in total puzzlement, but the dog that is a serious chewer loves them. About a week for one. And this is a dog that has destroyed Kongs.
This just seems wrong.
Oh, that is just awful. I need two, please.
My dog is fond of dental night guards. Tasty! I now keep mine in a box inside another box.
Ick! thanks for the memory – the Border Collie we lost two years ago just loved used wax earplugs.
That’s a much cheaper habit.
My dentist chewed me out when i broke a tooth chewing on bones. (Lamb rib bone, from a chop, since I’m sure you want to know ). Yes, i crush them. She told me not to do that, but i told her i was probably going to continue to eat bones.
Um, why yes, all my crowns are gold, not ceramic. But mostly i still have my natural teeth.
Anyway, keep an eye on your dog’s mouth, but sometimes it’s worth it to take risks.