During their first weekend at the new house with their dad, Hannah and her dad have a conversation about how Bret says she has an overbite, dad states her teeth are fine. During that same visit, when Hannah and Em are in the garage, you can see the retainer in Hannah's mouth when she tells Em she'd "...feel better if you just stopped givin' a shit" during that same 1st visit. Then during their next visit is when you learn Hannah decide to have the overbite "fixed" to fix the "disfigured" way her teeth look.
Although it's not seen directly during the MRI scene, the plot implies that Em never removes the ring. Em would have been unable to wear the ring on her hand during the MRI (magnetic resonance imaging) test. Even if it was non-ferromagnetic (like gold), it could have still interfered with the test and medical staff would have likely removed it prior to bringing her into the room.
The scene where the family is hugging Em on the Hospital floor, the ring that supposedly makes the possession continue, slip out of Em's finger. Then the ring is shown again in her finger while Tzado tries to remove the demon from Clyde and while Em hugs Clyde. Immediately after that, Tzado catches the ring on the floor, making the scene confusing.
The Hebrew writing on the side of box in the opening scene appears upside down in relation to the lid and apparently spells out "Dibbuk" backwards. The writing on the lid apparently is backwards Hebrew for "You shall see the punishment of evil".