Getting The Full Picture With Cone Beam Dental Scans

Making The Invisible, Visible — The Many Advantages Of 3-D Images

(Continued)

CBCT vs. MRI: Alternate Routes To A 3-D Image

Magnetic Resonance Imaging (MRI) is another 3-D imaging method you may have heard about. Like CBCT, MRI allows a doctor to look inside your body without performing surgery. Both also use computers to assemble and interpret vast amounts of data produced during scans of a particular area of the body. But the similarities end there.

CBCT uses ionizing radiation (x-rays) to penetrate body tissues. Digital sensors measure the different levels of x-ray absorption by tissues of different densities to create a picture on a computer screen. MRI uses a powerful magnetic field and radio waves to vibrate the hydrogen atoms of the water molecules inside body tissues. The vibrations will differ depending on how much water is in each tissue. The radio frequencies of those vibrations are received and translated by a computer to form a picture. The patient is not exposed to any ionizing radiation during this process.

So why not use MRIs instead of CBCTs and avoid the x-ray exposure? The main reason is that an MRI, with its detailed views of soft tissues, doesn't give the dentist as detailed a picture as necessary of teeth and bone; and this is exactly what's needed to diagnose dental disease and plan treatment or surgery. Also, MRIs take longer, are more expensive, and involve much larger machines.

If you have any questions about which imaging method would be best for you, be sure to ask your dentist.

Applications in Dentistry

The additional information from a CBCT scan can make all the difference in some clinical situations, and remember, a doctor's treatment can be limited when he or she treats what he/she doesn't know about. Here are some examples of CBCT use for different dental applications:

Orthodontics

When teeth are straightened orthodontically (“ortho” – to straighten; “dont” – tooth) they must be moved through the bone that anchors them to the jaw. It's necessary for an orthodontist — a dentist who specializes in growth and development, and the movement of teeth — to know where and when to move them. This makes it important to have accurate information about the position of the jaws and teeth relative to the facial skeleton, and their stage of growth and development. CBCTs provide this information in 3-D, informing the orthodontist where and how the teeth can be moved effectively and safely to realign the bite.

Dental Implants

Replacing a missing tooth with a dental implant involves inserting a root replacement into the bone. Most dental implants are small titanium screw-shaped cylinders that serve as artificial tooth roots. CBCT scans allow for accurate location and visualization of vital structures like nerve canals, sinuses and the exact position of the teeth in the jaws, all critically important in treatment planning. CBCT increases the success of implant placement by allowing the precise determination of where to place the implants, in addition to exactly what that area looks like. CBCT enables the creation of surgical guides for the dental surgeon to position the implants in exactly the right position in the jawbone.

Oral Surgery

Orthognathic Jaw Surgery — CBCT scans are also tremendously helpful when both orthodontic tooth movement and orthognathic jaw surgery (“ortho” – straighten; “gnathos” – jaw) may be needed to treat a difficult malocclusion (“mal” – bad; “occlusion” – bite), and when other diseases of the jaws are best evaluated in 3-D.

Temporo-mandibular Joint (TMJ) Disease — CBCT scans can provide 3-D information for diagnosis of and treatment of facial pain by viewing the TMJs (jaw joints), teeth, sinuses and airway (windpipe) all in one scan. CBCT scans provide a unique insight into the pathology (disease) of the jaw joints and their associated structures during functional jaw movements.

Impactions — Impacted teeth that are trapped beneath the gum line, unable to grow in properly because they are pushing against neighboring teeth or other structures that block their way, are a relatively common occurrence. CBCT provides crucial information about impacted teeth and their relationship to adjacent teeth, nerve canals and sinuses.

Sleep Apnea

Imaging of the airways, nose, mouth and windpipe is also proving useful in the diagnosis and treatment of sleep apnea (“a” – without; “pnea” – breath), a dangerous condition in which the tongue and other soft tissues at the back of the mouth block the windpipe during sleep.

Root Canal Treatment

In a root canal procedure, a dentist or endodontist (root canal specialist) needs to remove the inner tooth pulp tissue that has become infected and then replace it with a sterile filling material. Some high-resolution CBCT machines even allow the dentist to look into root canals of the teeth in 3-D revealing their exact shape and branches, and to determine precisely where infection is located.

Can CBCT Help Me?

That's a question only your dentist can answer, based on his or her evaluation of your unique situation and health history. CBCT offers a fast, thorough, non-invasive means of obtaining detailed information. Remember, however, that any source of radiation exposure carries at least some small risk. The fact that today's technology is digital has reduced the exposure significantly but it should still be used only when necessary diagnostically. It's always a good idea to review the risks, benefits and alternatives to any imaging procedure with your dentist before it is performed.

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Review Date: 5/1/2013
Authored By: Jerome N. Peck, DLXT
Reviewed By: Dr. Garry A. Rayant, Editor-in-Chief, Dear Doctor, Inc.