Jenny asks an important question. Because every office handles the transfer of records a little bit differently it's hard to know what to expect.
You do have a right to your dental records including dental xrays.
The dentist is also required to keep a copy of your records for a certain time. Most often the dental office keeps the originals and gives you a copy. Some ask that you request your records in writing, sign a release or pay a copying fee.
It's an annoying process and one that many times doesn't work well.
Previous x-rays and records can be a big source of stress when changing dentists.
You do have a right to them but, depending on how recently your X-rays have been taken, you may not need them.
Most dentists take a full set of xrays (FMX) every 3-5 years and a smaller set called bitewing xrays once a year.
The full set (18-20 individual xrays) is worth taking with you if it is less than 5 years old. Since bitewings are taken every year, they are not as important to get.
Sometimes it is helpful to have older dental X-rays and records for comparison but most dental problems can be diagnosed and treated with current xrays.
Digital vs Film
Unless they are digital, copies of xrays lose some of the quality and are not as easy to read.
Dentists who have digital xray equipment prefer to have digital xrays and may not want to use your previous x-rays if they are taken with film vs digital sensors because the quality is not as good and they are much more difficult to read.
Ask your new dentist to request your records
Once you find a new dentist, ask them to request your records. If your old X-rays and records are recent enough they can be mailed or emailed to the new dentist.