As is evident in fossils that have withstood centuries of wear, tooth enamel is one of the hardiest parts of the human body.  However, teeth still have their breaking point.  If you were to receive a hard hit to the mouth, chances of damaging a tooth are great. 
Some breaks can be classified as cosmetic problems, but others are true emergencies.  Breaking a tooth can be painful, but not taking the proper steps to care for it can also be dangerous. Knowing what to do in the event of a broken tooth is not something you often think about, but can be very important.
Tooth breaks can range anywhere from minor chips to major fractures.  There are three layers to a tooth which are the enamel, dentin and the pulp.  The enamel is the hard outer coating.  The main part of the tooth is the dentin and the fleshy nerve center of the tooth is what is known as the pulp. 
Generally when people chip a tooth, they have just knocked off a chunk of the enamel.  These breaks are not normally painful but are more of a cosmetic problem.  However, if enough enamel breaks off, the dentin can be exposed.  This break is not often painful either, but it can cause the tooth to be extremely sensitive to cold.  The worst breaks expose the pulp and are extremely painful and cause bleeding from the tooth.
If you have a minor chip in your tooth, this is not considered an emergency and you are not in any danger of losing your tooth.  You will want to make an appointment to get in to see your dentist within the next week or so.  If you experience any discomfort, you can take an over-the- counter painkiller such as ibuprofen. 
If your tooth is fractured, you can consider it a dental emergency since exposed nerve tissue could become infected.  First, rinse your mouth with warm water and call your dentist to get in to see them right away.  Take a painkiller (not aspirin which can increase the risk of heavy bleeding), and put an ice pack or cold compress on your mouth to reduce the swelling, control bleeding and ease the pain. 
If your tooth has been knocked out, you should get to your dentist immediately, because chances are, they may be able to reimplant the tooth.  To perform a successful implant though, the tooth still needs to be "alive", so you will need to take good care in transporting the tooth and do so quickly.  When handling the tooth, only touch the chewing end, not the root.  You can use any of the following options to transport the tooth.
    Put the tooth back in the socket. Bite down on gauze or a wet tea bag to help keep it in place.
    Store the tooth in a small container covered with a small amount of whole milk or saliva.
    If you cannot get it into the socket, the tooth can be carried between the lower lip and lower gum or under the gum. (Be careful not to swallow the tooth.)
    Special devices called Save-a-Tooth and EMT Tooth Saver, which contain a case and a special fluid to use if a tooth is knocked out, may be available from your dentist to keep in your first-aid kit.
Once you get in to see the dentist, depending on the severity of your break, your dentist will take different approaches.  Minor chips usually don't require treatment unless cosmetic.  If you don't like the way it looks, your dentist can either smooth out the chip or fill it in with a composite material.
If the dentin has been exposed during the break, your dentist can cover it with a hard, enamel-like coating.  If the pulp is still healthy, the tooth can usually be completely fixed with a permanent crown.  However, if the pulp is damaged a root canal treatment may need to be performed in order to remove all or part of the damaged pulp before putting on a crown.
Your dentist will probably want to follow up to make sure your tooth is healing well.  You will want to go easy on that tooth for a while and keep it clean and safe.  Make sure to brush and floss every day and wear a mouthguard when you play sports. 

There are many different mouth injuries that can happen at inopportune times, so it is important to know how to handle them.  The best thing you can do is to prevent injuries by knowing how most dental emergencies happen.  When you are participating in any kind of sport or physical activity, it is very smart to wear a mouth guard.  Mouth guards will protect your teeth in case of falling or extreme impact.  You can also prevent teeth injuries by avoiding chewing ice, popcorn kernels, hard candy, or anything that could crack or chip your teeth.  Also, never use you teeth to cut tape, string, or thread; always use scissors.  Regardless of taking necessary steps, you can never fully prevent injuries, so prepare yourself with the knowledge of how to handle specific situations

    A bitten lip or tongue
If any part of the mouth is bitten and cut open, gently clean the injured with a clean cloth and rinse with warm water.  Apply cold compresses to reduce or prevent swelling.  Generally this injury doesn't need medical attention, however, if the bleeding will not stop, you will want to go to the emergency room

    Broken/chipped tooth
Rinse the mouth with warm water.  Put cold compresses around the area to prevent swelling and call your dentist immediately.  Even if the tooth does not hurt, be sure to make an appointment with your dentist to avoid further complications.

    Broken jaw
Get to a dentist or an emergency room immediately.  Do not move the jaw.  Use a towel, tie, scarf, or anything to wrap around the head to keep the jaw stable and immobile.  Apply cold compresses.

    Knocked out tooth
Hold the tooth by the crown, never touch the roots.  Rinse the tooth if it's dirty, but do not scrub it or remove any attached tissue fragments.  If at all possible, gently hold the tooth in the socket.  If it is not possible, put the tooth in a glass of saliva or milk, or even water.  Take the tooth with the patient to the dentist as soon as possible.

    Lost filling or crown
If you have lost a filling, don't try to put it back in the tooth, however, if possible take the remaining piece to the dentist.  He may be able to determine why it fell out and may even be able to recement it in the tooth.  Cover the tooth with a temporary material, such as dental wax, and get to the dentist as soon as possible.
If you lost a crown, try to salvage it.  If possible, use a temporary adhesive to put the crown back in place.  You can use vaseline, denture adhesive, or a temporary dental cement, and then get to the dentist as soon as possible.

    Object stuck between teeth
Gently try to dislodge the item stuck between the teeth by flossing.  Avoid the gums so you don't cut them.  Never use any kind of sharp instrument to try to get the object out.  If you cannot get the object out by flossing, contact your dentist and get in as soon as possible.

    Toothache
Rinse your mouth with warm water to clean it out and floss to dislodge any debris that may be causing the toothache.  Take over the counter medication in the recommended dosages to ease the pain.  Continue to take the pain pills at the correct time intervals even if the pain eases to prevent it from returning.  Never put any pain killers directly against the tooth because it can burn the gum tissue.  If the toothache persists, contact your dentist.

Dental emergencies are sure to happen no matter how much you try to prevent it.  However, knowing what to do in each situation will save a lot of time and energy because you will be prepared to handle it.

There are many different mouth injuries that can happen at inopportune times, so it is important to know how to handle them.  The best thing you can do is to prevent injuries by knowing how most dental emergencies happen.  When you are participating in any kind of sport or physical activity, it is very smart to wear a mouth guard.  Mouth guards will protect your teeth in case of falling or extreme impact.  You can also prevent teeth injuries by avoiding chewing ice, popcorn kernels, hard candy, or anything that could crack or chip your teeth.  Also, never use you teeth to cut tape, string, or thread; always use scissors.  Regardless of taking necessary steps, you can never fully prevent injuries, so prepare yourself with the knowledge of how to handle specific situations

?    A bitten lip or tongue
If any part of the mouth is bitten and cut open, gently clean the injured with a clean cloth and rinse with warm water.  Apply cold compresses to reduce or prevent swelling.  Generally this injury doesn't need medical attention, however, if the bleeding will not stop, you will want to go to the emergency room

?    Broken/chipped tooth
Rinse the mouth with warm water.  Put cold compresses around the area to prevent swelling and call your dentist immediately.  Even if the tooth does not hurt, be sure to make an appointment with your dentist to avoid further complications.

?    Broken jaw
Get to a dentist or an emergency room immediately.  Do not move the jaw.  Use a towel, tie, scarf, or anything to wrap around the head to keep the jaw stable and immobile.  Apply cold compresses.

?    Knocked out tooth
Hold the tooth by the crown, never touch the roots.  Rinse the tooth if it's dirty, but do not scrub it or remove any attached tissue fragments.  If at all possible, gently hold the tooth in the socket.  If it is not possible, put the tooth in a glass of saliva or milk, or even water.  Take the tooth with the patient to the dentist as soon as possible.

?    Lost filling or crown
If you have lost a filling, don't try to put it back in the tooth, however, if possible take the remaining piece to the dentist.  He may be able to determine why it fell out and may even be able to recement it in the tooth.  Cover the tooth with a temporary material, such as dental wax, and get to the dentist as soon as possible.
If you lost a crown, try to salvage it.  If possible, use a temporary adhesive to put the crown back in place.  You can use vaseline, denture adhesive, or a temporary dental cement, and then get to the dentist as soon as possible.

?    Object stuck between teeth
Gently try to dislodge the item stuck between the teeth by flossing.  Avoid the gums so you don't cut them.  Never use any kind of sharp instrument to try to get the object out.  If you cannot get the object out by flossing, contact your dentist and get in as soon as possible.

?    Toothache
Rinse your mouth with warm water to clean it out and floss to dislodge any debris that may be causing the toothache.  Take over the counter medication in the recommended dosages to ease the pain.  Continue to take the pain pills at the correct time intervals even if the pain eases to prevent it from returning.  Never put any pain killers directly against the tooth because it can burn the gum tissue.  If the toothache persists, contact your dentist.

Dental emergencies are sure to happen no matter how much you try to prevent it.  However, knowing what to do in each situation will save a lot of time and energy because you will be prepared to handle it.