Having discussed Metal Crowns and its Biocompatibility, let's discuss about Metal crowns and MRI Compatibility.
MRI is a powerful and essential tool in the world of medical diagnosis. MRI stands for Magnetic resonance imaging.
Here’s a little-known fact: Objects like oxygen tanks, IV poles, stretchers, and wheelchairs aren’t allowed in the room with an MRI machine. That’s because the magnet in the machine is powerful enough to pull them in at high speeds. For the same reason, patients must remove all metal jewelry.
If a dental crown contains magnetic material, there is a chance that it could literally be pulled off the tooth. These Projectile accidents with dental crowns and MRI are by far the most frightening.
This can be painful and dangerous for a patient undergoing MRI. Even if a crown is not pulled out, it can be damaged by the strong magnetic field of the MRI machine causing it to vibrate. This vibration can move, bend, or break dental restorations.
At times crown may not be pulled out, but can be risk as the energy created by the magnetic field can heat the metal enough to cause Thermal burns on the nearby tissue.
Artifacts-is the term used when metal distorts or obscures the image produced by the MRI machine. While not dangerous to the patient, “artifacts” can be problematic when dental crowns and MRI interact.
They may show up as blurry areas on the image. The lack of a clear image can make accurate diagnosis difficult at times.
Artifacts 👆 in magnetic resonance imaging: How it can really affect diagnostic image quality and confuse clinical diagnosis- pic courtesy ResearchGate.
Dentists should know what the implant or prostheses (crown or bridge) is made up of and advise their patients of the facts.
Mostly they are
Ferromagnetic
Paramagnetic
Diamagnetic
In order for a material to interact with a magnetic field, the material needs to have a property known as ferromagnetism.
Titanium is not ferromagnetic so, should not interact with magnetic fields.
Common materials that are ferromagnetic include iron, nickel, cobalt and alloys of these metals (including stainless steel), many of which are found in materials used in dentistry.
These will disrupt local magnetic fields produced by the MR imaging system in the area, and may cause sizeable artifacts on the images.
It also causes prosthesis like crown or (FPD) Fixed partial dentures, Complete denture with metal denture base. Cast partial denture, Implants dislodgement.
Failure of magnets used in overdentures, magnetic keepers, etc., and deflection of orthodontic wires are possible.
As magnetic fields become stronger, the interaction with a ferromagnetic substance may cause vibration and potentially dislodgement of the material which could be very dangerous in or around MRI equipment.
Based on the magnetic field strength:
Low-field MRI scanners (0.23 T-0.3 T): They are typically identified as open MRI scanners. Low-field MRI scanners have decreased image quality and require a longer scan time compared to high-field MRI scanners.
High-field MRI scanners (1.5 T to 3.0 T): These are typically identified as closed MRI scanners. A 1.5 T MRI scanner provides great image quality, fast scan times, and the ability to evaluate how certain structures in the body function. The 3.0 T MRI scanner is great for visualizing very fine detail, such the vessels of the brain or heart.
Ultra-high field MRI scanners (7.0 T to 10 T): It is not widely available and is typically used for research.
T Stands for tesla, a unit of measurement
Here I wish to share another very interesting case with the reader, where a patient had come with a complaint of "burning pain in mouth".
There were no symptoms of BMS, Xerostomia nor any patches of LP or puffy bleeding gums or periodontal issues or Aphthous Ulcers/stomatitis...not even any sign of redness...
On examination I could notice Metal fused to Porcelain crowns and on eliciting history, I found these Crowns made at different time and with different materials!
There were also certain Amalgam fillings too.
On examination with silver foil...it was Dental galvanic shocks as I suspected!
Oral galvanism is a term for the association of oral symptoms to either toxic effects of amalgam fillings/ cheap metals...or electric currents between different metals in dental restorations and electrolytes in saliva or dental pulp.
A similar tingling/burning sensation may be also felt, while flying at high altitude, which is termed as "Barodontalgia"
Basically, when you bite on Ag foil, you set up a battery in your mouth and the electrical current stimulates nerve endings in your tooth and the brain interprets the impulse as pain.
Once the old fillings were replaced with Composites and Metal crowns replaced with Medical grade Biocompatible crowns patient was relieved instantly of the said burning pain
Guide lines to Follow for MRI
Removable appliances/prosthesis is not a problem, since patient can remove it.
Treat all material as MR unsafe, if the dentist is not sure about the type of prosthesis/appliance.
It is advisable to remove the prosthesis/appliances prior to MRI.
If patients are concerned about dental work interfering with an MRI, they have a number of options for future restorations (cavities they have to get filled.)
Zirconia, Porcelain and Resins are popular choices because they can be made to match the color of natural teeth, making them less noticeable than Silver Amalgam fillings.
An MRI of 1.5 T is known to be safe for amalgam restorations. However, research indicates that MRI is not completely devoid of any effects on amalgam restorations. Exposure to ultra-high-strength MRI may release toxic mercury from amalgam fillings in teeth, according to a new study appearing online in the journal Radiology. The effect was not seen, however, in the lower strength, more commonly used 1.5-Tesla (T) MRI.
Maintain Medical records of Dental work done
Ask for written Metal Warranty not time warranty.
Evaluate and be sure that previous procedures didn’t leave any metal in the body, just as cardiac pacemakers and aneurysm clamps and make a note of it as in emergencies one may not be focused on such things in Anxiety.
Keep track of all future dental procedures and consult with the dentist about the materials that are being used, Get it written and keep records safely.
Summary
It’s impossible to predict whether an MRI may be needed at some future date.
Materials for prosthetic restoration should be selected based not only on their biological compatibility and functional and esthetic qualities, but also on whether or not they are MRI Compatible and do they least generate minimum artifacts in MRI.
To Get your Crowns evaluated, or to find an alternative and If there is any doubt about the materials used in your Prosthesis, Please book your slot at our website dentistlotusclinics.com
Issued in Public Interest
Disclaimer: Lotus Clinics claims no credit for certain images / Videos featured on our blog site taken from web, unless otherwise noted. This is written for Educational purposes and to bring awareness among public, with case Study pics of my Patients with their written /Audio/ Video Consent
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