Genetics play a role in tartar buildup/bad breath too. The PetzLife gel does work, very well. I am lucky to not have any dogs with tooth problems. I keep an eye on their teeth and every once in a while I do a little scaling, but I have never had a dog who needed a professional cleaning.
My friend with shelties has had a few in the past who had bad teeth, or had a tendency to develop plaque quickly (fed a high quality, all kibble diet with bones offered). Those dogs typically had a family history of bad teeth though. She likes the PetzLife products as well.