My dog had oral papillomas. Why did they vanish and how to prevent?

Hello, this is associated with a papillomavirus that is also self limiting. That is, dogs can develop this and resolve on its own. The virus can be passed down from mom to offspring and the vaccine has been used to treat severe cases but does not produce immunity. The vaccine is usually considered in severe cases only where the dog may be unable to breathe. Therefore the only prevention is not to breed affected pets. Some may be carriers and not be affected by the disease.

There are several treatment modalities for papillomas, including surgery, radiation, cryotherapy, or the vaccine. Hope this helps and best of luck.