Scientists had long suspected that birds and mammals are the only vertebrates to experience rapid eye movement (REM), a sleep state in which the body is
mostly immobile but the brain is in overdrive.
While dental problems in humans are easily solved with a dental visit and the use of local anesthetics to keep pain at bay, dogs for obvious reasons can not stay
immobile with their mouths open wide while odd, loud, and
mostly scary instruments are inserted into their jaws.