Every time you go to the dentist it's always the same.  You walk in, tell the receptionist you've arrived and s/he hands you a stack of papers to fill out.  And they always say the same thing.  They ask for your name, personal information, address, contact information, and your medical history.  Honestly, why does the dentist care if your Grandma had cataracts in her left eye?  And why does it matter if you were once hospitalized for a concussion 4 years ago?  Why does the dentist ask all those questions about medical history?  It's not that important, is it?

Ah, but it IS important. 

First of all, your dentist needs to know your personal history (medical aspects aside) because any medical professional needs to be aware of your personal stats.  Knowing your weight, height and age tells your dentist certain things that should be expected in your oral health.  An overweight, middle aged man will have very different dental health than a young vegetarian.  Obviously, the dentist asks for things like your address and phone number for emergency and billing purposes. 

The most important reason that your dentist needs to know your medical history is in case of a medical emergency.  Imagine this: you're sitting in the dentist's chair, just about to have a minor cavity filled.  The dental assistant gives you a few shots of Novocain to numb the area that the dentist will be working on.  For a few moments everything is normal.  Then, all of a sudden, you go into convulsions, thrashing around, flailing your arms, and foaming at the mouth.  What the dentist didn't know was that you are severely allergic to Novocain.  If s/he had this piece of information, you would have been given a different form of pain killer and avoided a very dangerous situation. 

Another reason that your dentist needs to know your medical history is found in your current health conditions.  If you've recently gotten over cancer, your dental health is likely to be in a different condition than it would if you had never had cancer.  If you had seizures as a child but haven't had one in 10 years, your dentist needs to know that in case you suddenly go into a seizure again.  With this information your dentist will know how to react to each situation that may be thrown at him/her.  Without it, dangerous situations may be allowed to occur.

Fourthly, your dentist needs to know if you are or recently have been pregnant.  For example, if you are pregnant and have had morning sickness, you have probably been vomiting fairly frequently.  If this is the case, your teeth may appear in a much unhealthier state than would seem likely (it might look like you are bulimic).  The acid found in your stomach can seriously damage the enamel on your teeth.  Your dentist will need to use greater care when working on your mouth if you are pregnant. 

Finally, if your dentist needs to prescribe any pain killers or other form of medication, knowing your medical history is vital.  S/he will need to know any medications you are currently on and what they're for, so that s/he does not prescribe something that could interfere with your medicine.  Also, knowing your medical history will enable your dentist to know what types of medication you might be allergic to or what medications are the most or least affective.