Required - No (unless you absolutely want to practice in NY or DE - the only 2 states which do mandate a post-doc residency). As a side note, I am pretty sure if you ask this same question again in 5-10 years, you will get a different answer (Yes).
Dental post-graduate residencies can be divided into:
1. General Parctice residencies (GPR + AEGD)
2. Specialty programs (your Endodontists -root canals-, Periodontists -gums-, Maxillofacial -trauma cancer plastic-, Orthododntists -braces-, ....).
The number of graduates who go onto each of those categories significantly varies year to year and even among schools themselves.
Roughly, I would put the percentage of fresh dental graduates who go onto some sort of post-graduate residency at;
1. General practice - 25%
2. Specialty programs - 40 %
That's obviously a guess, at best.
I'm actually a 1st year med student, but a friend of mine and I had a discussion the other day about dentistry. I know that in order to specialize in a particular field, you need to do residency in that field. But what about general practice? I know that you CAN do residency in general practice (I believe it's 2 or 3 years) after you obtain your dds. But are you REQUIRED to do residency? Is residency in general dentistry OPTIONAL for those that want to be more competent in this field? If it is optional, how many general dentist do you think actually obtain postprofessional education?