Nerve exposure almost always leads to the need for root canal treatment. The sooner you can get to the dentist the better. Do not touch the pink pulp as bacterial contamination is the enemy. Keep your mouth as clean as possible. Brush all the other teeth, tongue, and use piksters to keep area hygienic. The aim is to remove plaque from the mouth, not to stir it around. Rinse the tooth brush frequently. Do not brush the broken tooth but rather use a fine toothpick to gently scratch the plaque off the tooth near the gum line. Do not touch the pulp or anywhere near the pulp (within 5mm). Saliva is good to cover the exposed pulp, provided the saliva is not full of bacteria. Mouthwash may traumatise the pulp, although it is a good idea for the rest of your mouth. Dipping the piksters in mouthwash may be effective. Eat away from the broken tooth. Keep it as clean as possible, and dont let it dry out. Avoid sugary foods. Keep the tongue clean (brush it after every meal) as it will sit against the pulp the most. Get to the dentist ASAP.