Dental fear can be mild, moderate or severe.  It should not keep you from dental care.  I believe that, In the case of most dental phobias, the patient visualizes the dreaded drill, needle, extraction forceps, root canal.  They can actually "see" in their mind the whole scene (much like a person with fear of flying visualizes a crash).  So, first of all, don't go there with your mind.  Keep your eyes open and engage the world. Think about something else,  your feet. Talk to the assistant and look around the room.  I had a horrible needle phobia as a child and I frequently fainted.   From experience, I learned that I could look at something in the room and wiggle my toes hard and I could purposefully distract myself so that I felt very little and lost the fear.

For people with serious dental phobia, I recommend an anxiety drug, similar to the one you get in the IV at minor surgery.  A tablet the night before to sleep and a table an hour before the appointment gives amazing relief to the patient.  They cannot drive to the appointment though.  Remember, anxiety involves physical changes I the body.  These drugs are specific for anxiety and they are a Godsend.

Here are some things to remember:  Modern root canals rarely hurt because the tooth is numb.  Dental needles are not as big or long as they seem.  Because the anesthetic comes in individual cartridges, it is used in a stainless steel or plastic gadget that makes it seem large.  The needles are quite small in diameter, sharp and coated with a slippery surface.  They are a bit longer that the usual muscle needle in your arm because they have to be to get into the mouth.  But they don't go into the tissue far.

Some dentists are more patient than others, kinder, gentler etc.  Some dentists explain every detail and some rarely say a word. Find someone you like and be prepared to pay more for the dentist's time if you want a non-rushed relaxed appointment.  If you want more explanation, let the dentist know.  And really, don't wait too long.  The $150 easy-to-do filling can become a $2500 root canal and crown if you wait. And don't look only at the fee: the better the work, the less chance it will need to be done over!

Finally,  do not allow yourself to make excuses for your failure to get treatment.  Yes, your old dentist may have hurt you.  But that was then and this is now and inaction will make things geometrically more expensive and difficult. 

Please remember that this information on this site is not all-inclusive and it may or may not apply to your situation and you need to call your own dentist.