Depends. Most foods or beverages have inherent sugar content. Cows' milk has natural sugars that can cause cavities. The length of time the teeth are exposed is the critical factor. Baby bottle caries comes from generally fruit juice mixes in the bottle that a child may ingest over many hours. Rinsing with water well, should clear the mouth of these sugars. It is the time exposed that is critical.
Yes. It can. Each time a tooth is exposed to milk, it is exposed to about an hour of acid on the teeth. Multiple exposures of acid on teeth will cause cavities. If a child sleeps for seven hours per night and that child has access to a bottle of milk, the teeth could well have seven hours of acid exposure per night! limit the number of exposures to the acids. No bottles/sipply cups in bed.