When Dexter first talks to the receptionist she says "Coral Island" but a moment later says "Palm Island" while referring to the same place.
When Dexter is making enquiries at Coral Island retirement home you can see a stack of leaflets on the desk as he faces the receptionist. As the camera switches to face Dexter they are gone.
The Tooth Fairy is said to take the left lateral incisor (the far left of the front four teeth) as a trophy, because he lost it due to abuse from his mother. However, when Dexter finds the trophy teeth in the storage locker, there are bicuspids and molars in the box, as well as incisors.
When Batista's Trans Am breaks down, he gets out and opens the hood and the scoop is attached to the hood. On real Trans Ams the scoop is mounted to the air filter housing which is attached to the engine, and the hood would have a hole in it for the scoop to protrude through.
When Batista drives down the street behind the ambulance there is a Florida license plate on the front of the Trans Am. Florida doesn't use 2 plates, only one in the back.
The "Tooth Fairy" is supposed to have removed his victims upper left lateral incisors, yet when we see the contents of the box in Walter Kenny's lockup, it contains a whole mix of teeth including molars and premolars (bicuspids). Looks like only one, or possibly two lateral incisors in there.
When the "corpse" is rolled over, she repositions her leg on her own.
Dexter and his father assume that a serial killer from the 1980s would be in his 70s now. If the killer was only 20 years old and the events were as early as 1981, the killer would only be 51 now.
When Dexter notices that Walter Kenney's upper left lateral incisor is missing, in the voice-over he says that Kenney wears a dental implant, but what Kenney has is a partial denture which he moves up and down with his tongue, attracting Dexter's attention: an implant would be immobile and not at all obvious.