My toothache started nearly a month ago . The pain's been keeping me awake . Would you please have a look ?   Open your mouth , please . Which one ?   The one right at the back .   I'm afraid we can ’ t save that one . It will have to come out .   Will it hurt much ?   I'll give you an injection , then you won't feel pain .   ( 5 minutes later ) OK , it's all over . Spit there and bite the cotton ball tightly in place for half an hour . 