What's best for Shih Tzu teeth: dog toothpaste or dental chew treats?

Hello, and thank you for using PetCoach. It's great that you're thinking about Teddy's oral health! It is best to brush Teddy's teeth daily using a toothpaste formulated for dogs. There are lots of good options, so try a few out and see what flavors Teddy likes, but I recommend an enzymatic toothpaste. Here's an example:
https://www.petco.com/shop/en/petcostore/product/sentry-petrodex-enzymatic-toothpaste-for-dogs-5000644--1

It's also beneficial for Teddy to chew on things that are meant to massage his gums and help work tarter off his teeth. I prefer rawhides that are coated in enzymes to help combat tarter, such as these:
VIP-_-92700027187667220&kwid=p27187667220&device=c&gclid=EAIaIQobChMI2PLt-eSv1wIViLrACh0JkwyJEAQYASABEgLS3PD_BwE

My own opinion is that providing good products for dogs to chew on does the most to help their teeth - but the combination of chewing and regular tooth brushing will benefit Teddy's oral health the most. Also, some dogs are less enthusiastic about chewing, which makes brushing the teeth even more important.

Of course, all of these are measures to help slow tarter production - but nothing completely replaces regular dental care from your veterinarian. Just as we humans brush daily and still need regular dental care, our pets need the same. Hope this helps!