question: Hello there - my 5 year old daughter has a grey/blue/black mark about 4mm wide and long directly underneath her bottom front tooth (this is an adult tooth that came through about 6 months ago) and the gum looks lower than the tooth next to it... Have a dentist appointment booked for next Thursday but I m a bit worried... what could it be? she is fit and healthy but possibly doesn t have the best oral hygiene but we re trying.... thanks