In the flashbacks, a dog is killed offscreen by the mirror. No blood or anything, but you hear him whining so it's distressing.
In the present, the main character attempts to prove the mirror is evil by putting a dog next to it for it to “consume.†He's in a cage that is covered by a sheet. Someone frees the dog and he runs out of the house, presumably ok. This was in my opinion a poor choice by the filmmakers, because I was no longer invested in the main character after that. You don't come back from trying to kill a dog.
A previous victim of the mirror pulled out her own teeth and placed them in a bag. An old photograph of the teeth is shown.
Another victim eats shards of a bowl which damages her teeth. She is shown eating the bowl but the shot is obscured slightly. The teeth are not seen but blood oozes from her mouth. Later in the film you can see her teeth in her mouth.
The two parents of the film's protagonists are victims of the mirror shown in the film. Through flashbacks we see how the mirror gradually possessed them. The mother is shot by the father several times, and eventually the father forces one of the protagonists to shoot him as well. These events are brought about by the mirror and it's effects, and the children are visibly distraught by the change in their parents behavior and their eventual deaths.
This is a yes, while some may not find that as apart of body dysmorphia it actually is. The mom has phobias and worries surrounding her C-section scar and the mirror uses that against her.
In the present, the main character attempts to prove the mirror is evil by putting a dog next to it for it to “consume.†He's in a cage that is covered by a sheet. Someone frees the dog and he runs out of the house, presumably ok. This was in my opinion a poor choice by the filmmakers, because I was no longer invested in the main character after that. You don't come back from trying to kill a dog.