Dental X-Rays
December, 1999

Dear Dr. Mady: My dentist takes a couple of x-rays of my teeth at least once every year. Just how much radiation do you get from a dental x-ray and how harmful is it? - Steve O.


Dear Steve: Just the mention of the word x-ray or radiation sparks up an unpleasant image for many people. People have the tendency to automatically relate it to cancer, birth defects or even reproductive sterility. What individuals don't realize is that radiation has many beneficial uses. X-rays in the practice of dentistry are used to routinely diagnose and treat an unlimited number of conditions that could not be properly diagnosed without them.

X-rays are really energy in the form of waves, exactly like visible light. Actually the only difference between x-rays and light is that x-rays have enough energy to go through the body and light cannot. Therefore, x-rays can take pictures of the inside of the body and light can take pictures of the outside of the body.

A unit of measurement called a "rem" is used to measure radiation. It is a large unit, just like a kilometer is a large unit of length. Because of this we usually use a unit called a millirem (mrem). It is much like measuring in centimeters instead of kilometers. One thousand mrem is equal to one rem.

New advances in technology of x-ray film and machines now allow your dentist to take x-rays with considerably less radiation than the old machines in the past. A typical dental x-ray exposes you to only about 0.5 to 3 mrem. The average person gets approximately 360 mrem every year from outside, background sources alone. These outside sources include but are not limited to radioactive materials in foods, on earth and in outer space. The maximum on the job yearly exposure for Canadian and American radiation workers has been set at 5,000 millirems. Low doses over a period of time are not as harmful as large doses at once because over time the body can recover.

Examples of everyday radiation that you may not realize you are exposed to include living in a brick house (about 10 mrem per year), cooking with natural gas (about 10 mrem per year), and sleeping next to someone else (about 2 mrem per year). All of us have small amounts of naturally occuring radioactive materials in our bodies. You can even get the equivalent radiation of two dental radiographs just from a short plane ride like from Windsor to Toronto and an entire day in the sun is comparable with twenty dental x-rays.

The following figures for comparison were taken from "RADIATION" , a book by radiologist Dr. Martin Ecker and the sceince writer Norton Bramesco and as you can see, dental x-rays are very low on the list in terms of the amount of radiation that they possess:

HIGH DOSE GROUP ............................ mrem

Barium enema: lower GI series .............. 875
Pelvimetry ................................. 595
Barium meal: upper GI ...................... 535
Mammography: breast examination (per breast) 500
Lumbrosacral spine ......................... 450
Small bowel series ......................... 422
IV pyelogram (kidneys, ureter, and bladder . 420
Lumbar spine ............................... 347
Thoracic Spine ............................. 247

MEDIUM DOSE GROUP

Gallbladder ................................ 168
Abdomen .................................... 147
Ribs ....................................... 143
Pelvis ..................................... 133
Skull ...................................... 78
Hip ........................................ 72

LOW DOSE GROUP

Cervical spine (neck) ...................... 52
Femur (upper leg) .......................... 21
Dental (full mouth series) ................. 9
Dental (one x-ray) ......................... 0.5

So to sum it all up, you can have approximately 10,000 x-rays taken per year by your dentist before exceeding the maximum allowable dose. Obviously you will never require this kind of exposure and since your dentist obtains very valuable information from x-rays to assist you in keeping your teeth healthy, it is NOT in your best interest to refuse dental x-rays because of the very small amount of radiation you receive from them.


This column is reprinted with the permission of the author and The Windsor Star. "Ask the Dentist" is written by Windsor dentist (and ECDS member), Dr. David Mady Jr.. The column appears the first Thursday of each month in the Windsor Star. Readers with questions can write to "Ask The Dentist", c/o The Windsor Star, 167 Ferry St., Windsor Ontario, N9A 4M5

 

 
     


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