Sometimes I think no backstory is better than knowing the reality. This is one of those occasions.
I don’t know how our friend managed to create a set of dentures out of his own upper teeth, but it is seriously one gruesome wound. If you look at a model skull, or real skull if you have one, you can see that the maxilla, the bone which extends from below the orbits and houses the teeth, is a rather vulnerable structure. This is especially true of the section which flares from below the nasal opening.
This guy appears to have sheared off his maxilla at that point, ending up with his upper teeth and the plate forming the roof of his mouth in one bloody, detached disk of meat and teeth. It almost looks like a wagon wheel which can bite back.
For American and third world readers, a wagon wheel in this context is a delicious biscuit with marshmallow and a covering of chocolate, not a wheel for a wagon. A quick search of the web will bring you up to speed.
How this injury occurred is anyone’s guess, but I’m thinking blunt trauma rather than say a machete. The wound appears too rough to be a blade entry and there is significant bruising around his face.
I hope that some decent medical assistance found him. I couldn’t imagine having free reign of my nasal cavities with my tongue, the flu would be particularly unpleasant.