Interesting / most difficult / most frightening / most challenging / unforgettable/ potentially fatal

Every dentist examines a number of  patients each day and gains more and more the clinical skills required for diagnosis and gains insight to distinguish between the conditions that appear very similar to each other clinically and are confusing to a neophyte in the field of dentistry.

You must have heard the saying "The eyes only see what the head knows" as a student which is true indeed. A good knowledge of the condition, its manifestations, signs and symptoms are vital to make a differential diagnosis pointing towards the correct direction. Even the general public these days believe that  older the doctor, the lesser the lab investigations he needs and demands before making a diagnosis. What are your opinions about that ?

Please Share your interesting / most difficult / most frightening / most challenging / unforgettable/ potentially fatal cases you've managed so far and share your feelings during the procedure, after completing it, and the lessons you learnt. You can share as many as you like. Have a nice time. Thank You !!!