I had the same problem with my 8 year old 90 lb Lab who I THOUGHT was huge. Poor guy was neglected until little man Yoshi came to live with us. I've been using DDS Dental Wipes on him (
Amazon.com: 8in1 D.D.S. Dental Wipes, 90-Count: Pet Supplies). They seem to be working. I'm on my first jar. I'm not sure if they're the best brand around, but I got them for under $10 on Amazon. I also give him one CET Oral Hygiene (
http://goo.gl/JanWb)chew a day. They have them in a petite size too for the tinies.