It is about 1/250 chewed bones, but don't think it'll happen in 250 bones, could be thousands before you get one.
As a drop from Mithril dragons, its not likely. There are no recorded videos of people getting a Dragon Full Helm as a drop from Mithril Dragons.
Chewing gum
Yes, but it had a rather solid foundation. Wales holds loads and loads of fossils, and they are often exposed naturally by erosion along the coastlines. The bones of some dinosaurs would easily feed a dragon myth. A few hundred years of fossil "explanations" can build a rather compelling creature in myths and legends, and as Wales had loads of bones and storytellers the dragon myth became very, very strong.
Before chewing gum became popular, children often chewed on natural substances like tree sap, particularly from the spruce tree, which was used by Indigenous peoples. Additionally, they chewed on various types of resin or mastic from plants. In some cultures, kids also chewed on licorice root or other herbal materials for flavor and enjoyment.
A betel nut is the seed of an areca palm and is often consumed and chewed in a betel leaf.
When not chewed, they are often not digested, similar to the seeds of some other fruits.
Dogs should have bones all of the time.
no, they often fight over territory
A dragon with hair is often referred to as a "wyvern."
Comminuted Fracture.Often seen in the brittle bones of the elderly
Kalphite Queen drops Dragon Chain pretty often, if you're lucky 1/50.
There are often sesamoid bones at the interphalangeal joints resembling the petella in the knee
A non-example of something gnawed would be a pristine pencil. Pencils are often chewed on incessantly as a nervous habit.