Little dogs are prone to really terrible teeth! You might call around and ask you local vets if they're doing anything special for Pet Dental Month which is, I think, in February. I know my vet does discounted dentals for the whole month. You might also be able to work out a payment plan.
There are natural things that can help as well. My dog has always had horrible breath. When I first got her, she'd open her mouth and literally the whole room would stink. The vet checked her, cleaned her teeth, pulled some, found nothing else wrong, but the smell persisted. I have found this stuff-
http://www.wysong.net/products/denta...supplement.php really works wonders! Its a natural blend of "dental active cheeses and minerals" I buy the 3oz bottles and for my 20 pound dog one lasts several months. They're about $8 where I live. I simply sprinkle it over her dinner at night. If we run out, I can tell within a few days because the stench returns!
Another thing I do is supplement with CoQ10. Her breed is prone to heart issues, so I give it partly for that, but also because some studies show it has some benefit in reversing gum disease and promoting dental health. The dosage for a 20 pound dog is 30mg/day. Prices vary widely, but I've found it for about $12 for 100 pills.
Finally, and the thing that I think shows the most benefit as far as teeth cleaning, is raw bones. They must be raw. Raw bones are still somewhat soft and do not splinter. And they are absolutely amazing at cleaning teeth. I've had dogs that clearly needed a cleaning, started them on raw bones (one every two weeks or so, given over a period of days until its gnawed out) and their teeth cleaned right up. You wouldn't have believed it was the same dog. You don't have to feed raw, merely give a raw bone to gnaw on. You can also try feeding raw chicken parts- backs and necks are popular, but you could substitute one meal every two weeks with drumsticks, thighs and breasts as well. So long as it is completely raw, you can feed it bones and all with no ill effects, and its great on their teeth. An extra benefit is that it also produces firm poops that naturally express their anal glands. I'm not talk about switching to a raw diet- merely providing raw recreational bones and/or the occasional raw treat. For bone choice, I much prefer beef knuckles for tooth cleaning. My local butcher has them, as does the pet store, in the freezer. I also see them at the supermarket labeled as "soup bones" Because my dog is small I buy a small one and have the butcher cut it in half for me. A raw knuckle should cost under $5.
Hope those ideas help some!