Have you looked at the ingredient list on Greenies? Ew. Here is an inexpensive way to make dental chews for you dog that they will love. Also, the gelatin is great for joint and hip care so you don't have to waste your money on poor quality pet supplements. These will keep for a week or two in the fridge so if you have only one small dog, you might want to half the recipe. If you have a Great Dane, double or triple the recipe and get really large molds.
I use Great Lakes gelatin that I buy on amazon. This is the recipe i use to make broth:
http://balancedbites.com/2011/04/easy-recipe-mineral-rich-bone-broth.html. If you want to make a batch specifically for pets, leave out the garlic. When I'm done making broth, I separate the bones from the garlic. I grind the bones that are falling apart or break easily and I save the ones that are still hard and reuse them in another batch of broth. I use a meat grinder attachment for the Kitchen Aid Stand Mixer to grind the bones. If you're not using the ground bones right away, you can freeze them. I separate some of the bones into half cup portions so I don't have to thaw the whole batch to make these.
1 cup broth
4 Tbsp Gelatin
2 Tbsp dried mint
1/2 cup ground bones (optional)
Heat broth in sauce pan on low to medium heat. Add gelatin and stir in until completely dissolved. When it starts to boil, turn flame down to low. Stir in the mint and let it steep for about 5-10 minutes, then add ground bone and mix completely. Continue to simmer on low for 15-30 minutes or more, depending on how gummy or how hard you want the chew to be.
Pour into silicon ice cube trays and chill. Keep refrigerated.
People often ask me how to cook Brussels Sprouts. It's pretty simple. 
