It is considered a dental emergency when your tooth breaks, cracks, becomes loose or is knocked out completely. If a tooth is knocked out, handle the tooth by the crown portion, not the root surface.
Keep the tooth moist; gently rinse the tooth and then place it in your mouth between your cheek and gum, or immerse it in milk or saline solution, try to see a dentist within one hour. If a tooth is loose and pushed out of position you can try to reposition it with light finger pressure, but do not force it, see the dentist as soon as possible. Broken teeth range from small chips to severe fractures.
Small chips can often be smoothed and do not require an emergency appointment, larger fractures should be seen as soon as possible. If you experience trauma to your teeth, and there is no visual damage or pain, at your next appointment let your dentist know so that it can be recorded in your dental history.
Tooth pain that involves swelling is a sign of infection and should be evaluated by your dentist as soon as possible. Many sport related traumatic injuries can be prevented by wearing a properly fit mouthguard.