It has become increasingly common to use three-dimensional x-rays, known as CBCT, to assess the position of the wisdom tooth in the mandible. But reducing the radiation dose for such X-rays, or using panoramic X-rays, provides at least as good a basis for treatment, new research shows.
When a patient has wisdom teeth problems, a common treatment is to remove all or part of the tooth. In the lower jaw, a nerve runs close to the roots of the teeth and during the operation there is a risk of damage to the nerve, which can lead to loss of sensation. Therefore, an X-ray should be taken to assess the position and relationship of the problem tooth and nerve.
Even with the low dose, nerve and root anatomy could be seen clearly, making it a useful method in the vast majority of cases.
Josefine Cederhag
A panoramic radiograph, where all the teeth are seen in one image, is a common method in this case, however, CBCT scans, which provide three-dimensional images of the tooth and surrounding tissue, have also become increasingly common.
“It has an advantage because it gives more accurate images of the position of the tooth and nerve, which can create more certainty before a surgical removal. But CBCT, which gives a much higher dose of radiation than other methods, is also used in cases where it is not needed,” says Josefine Cederhag, PhD student at the School of Dentistry.
Her thesis consists of four separate studies: in the first, the researchers looked at panoramic images of more than 400 people to see how useful the method is in assessing how the wisdom tooth sits in relation to the nerve.
“In more than half of the cases, we could clearly see how the wisdom tooth roots were above the nerve canal. This means that a panoramic image is sufficient to use as a base from this perspective.”
In the second study, oral surgeons, oral surgery specialists and general dentists answered a survey. Of the more than 170 respondents to the survey, most said they used panoramic images more often than CBCT or intraoral images, where only part of the mouth is seen.
“Respondents stated that panoramic images and CBCT provided more information than intraoral images, and the majority felt that CBCT also reduced the risk of complications after tooth extraction. But regardless of the method used, the decision to remove the tooth was not affected.”
The last two studies of the thesis focus on radiation dose in CBCT examinations. Partly by comparing different methods for measuring radiation and partly by testing whether it was possible to reduce the radiation dose without impairing image quality. A clinical study involved 48 people with a total of 62 wisdom teeth. They underwent scans with the usual CBCT settings and at a lower dose. Image quality was then assessed between the two scans.
“Even with the low dose, the nerve and root anatomy could be seen clearly, making it a useful method in the vast majority of cases. What was less clearly visible was the very small connection between the tooth and the bone, so sometimes the usual dose of radiation is still needed,” says Cederhag.
“I hope the thesis can help get more people thinking about different methods and how they are best used,” he adds.
Text: Anna Dahlbeck & Adrian Grist
