Alot of it is by the dog, I would not recommend them for someone with a large dog, as there is a chance with a heavy chewer to break off a piece and choke. I don't see much of a issue with that in the case of a shih tzu.
If you are doing this for the dog's teeth health a raw meaty bone is a far better choice. For a small dog like this I would get beef or pork neck bones. Separate them and freeze them. Give your puppy a frozen neck bone 1x a week. Teeth will stay far healthier with a raw bone than with any of the commercial dental chews. You can give neck bones now and no need to wait until older. He is likely teething and the cold will feel good on his gums.