Metal Restorations: How Does these Effect CBVT Scans?
Dr. O. asks:
In the past there have been discussions on Osseonews concerning the effects of metal restorations and scattering and how they effect the quality and accuracy of CBVT [cone beam volumetric tomographic] scans. I have had several patients who previously have had dental implants and now have had a CBVT. As I evaluate the bucco-lingual slices it would seem that there is no bone on the facial. At the same time as I probe in those locations there does not seem to be a fenestration or dehiscence. Does the radio-opacity of the implants hide the less dense facial bone were the contrast may be less? Your experience and thoughts would be appreciated.
3 Comments on Metal Restorations: How Does these Effect CBVT Scans?
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ttmillerjr
2/16/2011
Dr.O,
A common problem in CT images is streak artifacts caused by the presence of high-attenuation objects (metals). One will see bright and dark streaks. These artifacts can make it appear as though there is bone loss when there is actually none. Here is a story for you. I am a general dentist and have had my own cbct for about three years. Another dentist in the area recently got a cbct, an oral surgeon. I had a patient who had a sinus lift and two implants placed at my office. Ideal case, she had 5mm of alveolar bone height below the sinus, in good health etc,etc. The surgery went great, and in 5 months we restored the case. I'm going to shorten the story and just say that I referred her to this oral surgeon for some complications we had concerning something else. He took a new scan and went on to tell her that she had a large v shaped area of bone loss between the implants I had placed (streak artifacts). He told her it was probably because I didn't use hip bone in the sinus. The patient was ready to sue me. We ultimately talked on the phone and he would not admit he made a mistake. I asked him if he probed or otherwise verified his suspicion, he did not and said he had taken hundreds of cbct's and he didn't need to. I told him he has only had the machine for a month, how could he have taken hundreds? I was blown away by his incredible error for one, and the fact that research has shown there are many materials that have high success rates in the sinus, not to mention the morbidity and cost of harvesting hip bone. Anyway, the answer to your question is yes, the metal will create artifacts.
Mike, an assistant
2/22/2011
You will see similar artifacts from amalgam fillings and anything else metal (including earrings!) and lesser artifacts from composite & porcelain restorations.
As Dr. O noted, proximity of multiple radiodense items has an additive effect.
Joe
11/17/2011
Vatech has a unique feature with their cbct machines called MAR. (metal artifact Remove). It doesn't remove the artifact completely, but minimizes the artifacts for better imaging.
