Amazon offers Prime members the Vet's Best Enzymatic Dental Gel Toothpaste for Dogs for $8.66 with free shipping. (Non-members can order via Subscribe & Save to bag free shipping.) That's the lowest price we could find by $5. It comes with a toothbrush.

If you're ordering via Subscribe & Save, be sure to cancel your subscription once your order ships to avoid being billed for further shipments.