[anonymously]

How about a whole raw carrot? You could even freeze it first, the cold would be soothing to his teeth. Don’t be alarmed if you see carrot chunks in his feces, they don’t digest carrots well, but it doesn’t hurt them (one carrot per day).
I would start brushing his teeth once a day to get him used to it. Small breeds tend to have lousy teeth and you may be able to avoid a professional cleaning or two.
I like Petrodex 6.2 oz tube (chewy.com) and a medium brush, see YouTube for how to videos.