Oh, and to the OP: Congrats on the dental report! Reminds me of all the years when I took my son to the dentist and there were no cavities!!
I remember being SO happy about that.
I have a couple of yorkies that can actually go almost 2 years without a dental...the others need them every year.
My vet says that not only are small dogs prone to bad teeth because of their tiny mouths, but she says that breeding and genetics also come into play.