Wisdom Teeth Removal Imaging
It is common practice for dentists to use an orthopantomogram or panorex to obtain a panoramic x-ray of the upper and lower jaw. The view is accomplished by rotating the x-ray machine around your head for around 10 seconds. This machine is most commonly used to see if your wisdom teeth are impacted or not.
The problem is, is that dental x-ray machines produce images of poor quality. This is because in an effort to cut costs dentists purchase cheaper equipment that has been tuned down. Common costs of high quality MRI scanners are over 1 million dollars for each machine. X-ray scanners that dentists use cost in the tens of thousands of dollars. This is signficantly different than that of an MRI scanner.
Newer better equipment is currently available. A cone beam CT-scan (CBCT) produces three-dimensional views of impacted molars, not just two-dimensional images. Further it determines more precise tooth position. This is important to visualize impaction within the alveolar bone, location relative to adjacent teeth, and proximity to vital structures, such as the nerve canal, sinus walls, and cortical borders.
CBCT can in some cases be justified when assessing wisdom teeth especially in those patients who have increased risk for nerve injury such as the inferior alveolar nerve which could occur from removal. 
Both a panoramic x-ray and a cone beam CT-scan (CBCT) use ionizing radiation which have negative biological and health effects. Please see the wisdom teeth page for more details on specifics of radiation exposure with these two techniques.
1. American Institute of Physics. http://www.aip.org/
2. Imaging Sciences International. http://www.imagingsciences.com/
3. Gerold Eyrich and et al. 3-Dimensional Imaging for Lower Third Molars: Is There an Implication for Surgical Removal? J Oral Maxillofac Surg. 69. pages 1867-1872. 2011.