Radiation concern: How many dental xrays are too much?

I had my wisdom tooth taken out about 1 month and almost 2 weeks ago. It was a pretty rough extraction, being that my jaw bone was extremely thin. They were able to get the tooth out without fracturing the jaw. I have had to go back to the dentist almost once every week , or sometimes once every 2 weeks to get xrays done so that they can make sure that my jaw is healing fine. I have had about 5 xrays within that time frame. I am very concerned with all the radiation this might be causing, being that I am only 25 years old. I would like to know how much I should be concerned about this, or if I should have any concern at all? I only ask this because I know that recently they had some studies done that dental xrays may cause brain tumors.