We’ve heard it a million times: “a picture is worth a thousand words”. My question for you is this: how much is a sound worth? That’s right – how much is a sound worth? Recently, I was working on a patient when it occurred to me that in dentistry, a profession where visualization is paramount, how much I rely on sound and what I hear. And I don’t mean what I hear when I’m in conversation with patients and my teammates, which is obviously important, but more about what we hear when we are performing the craft of dentistry.
The rotation of the bur during contouring of composite is just one example. There is a certain frequency that the spinning bur makes that experienced clinicians know is ‘just right’ without even knowing the RPM’s. You hear it, and you know it. You know intuitively that when you place the bur to the tooth or material, there will be an expected outcome. The bur will cut precisely and as anticipated. You can’t measure the speed of the bur by visualization – it spins so quickly, but you know that sound. And with a gentle release, or a little more pressure on the rheostat, you do what you’ve done countless times before with precision-- just by hearing the spin of the bur. Another example of how sound plays a role in our dental worlds is that many of us listen to the patient as they ‘tap-tap’ after placing a restoration or when performing an equilibration. We look to see where to adjust using articulating paper, but we know when we are done adjusting, by listening. Do the teeth hit in unison, or is there the unmistakable sound of the porcelain crown hitting in isolation? Tap-tap. We know the sound, the resonance of even simultaneous contacts – all teeth hitting in harmony.
Today’s blog, and
the videos that accompany this blog ,
are specifically about using Doppler to listen to your patient’s TM joints. It seems that dentists too often under value the relationship of the TM Joints to the teeth during restorative treatment. Dentists must acquire a thorough understanding of the TM Joint to have predictability in their dental treatment. In over 30 years of treating patients, I have found that sometimes, one of our restorative patients becomes the dreaded TMJ patient. Anyone who has been practicing dentistry for a little while has experienced the phone call from the frantic patient who, all of a sudden, is not able to open their mouth. Maybe they woke up and now their bite is off. Any number of clinical realities that demonstrate that we can’t keep our heads buried in the ground as clinicians – we must come to terms that we need to understand the TM Joints.
One of the screening tools that I use when evaluating TMJ Health is Doppler Auscultation.
The use of a Doppler in dentistry was developed in the 1980’s by Dr. Mark Piper and is used to help dentists determine if the patient’s TM joints sound normal.
The doppler is basically a stethoscope with a microphone that projects the sounds from within the joint. I tell my patients that the doppler is a stethoscope, like what their MD would use to listen to their breathing or their heart, but with a speaker so that we can all hear the sounds. When the doppler is positioned appropriately, the dentist, and the patient, can listen to the sounds from within the joint space when the patient moves their jaw.
As we all learned in dental school,
there is a disc that separates the head of the condyle from the inferior border of the skull. The disc is there to prevent the bones from rubbing together during jaw movement. As many of us remember, there are two essential movements of the mandible in function:
rotation then translation. In the first 20 millimeters or so of opening, the condyles rotate within the joint space. Beyond the initial opening, if we need to open wide, or to protrude our lower jaw, then the condyle must ‘translate’. Also, when we move our jaw to the side that we are examining, this is called a ‘working’ motion. In a working motion, the condyle remains in the socket and only rotation occurs. When the jaw moves to the opposite side, the ‘balancing side’ the condyle must translate or move out of the jaw socket.
Why is this important that we talk about rotation and translation of the condyle?
This difference between the two movements of the condyle is important to understand when a TM disc displaces. When displacement occurs, the TM disc commonly only partially displaces. In a partial displacement, the disc is positioned only over the inside portion of the condyle, what is referred to as the ‘medial pole’. We are all familiar with the patient that has the ‘clicking’ joints – the clicking occurs when the patient moves their jaw. The ‘clicking’ sound is caused by the disc sliding back into a normal position to cover the condyle, and then clicking again as the disc partially ‘pops’ off the lateral pole of the condyle. The slipping of the disc onto and off of the lateral pole does not occur with all patients. Many patients will have a partial displacement without the disc returning to normal position. This ‘non-reduction’ of the disc simply means that the patient functions with the disc in the TM joint covering only a portion of the head of the condyle.
When we listen with the doppler, if the disc is fully in position when the patient opens wide, and the mandible rotates, there should not be any noticeable sound. The lubricated disc protects the bones from rubbing together. Conversely, if the disc is not in position, there will be friction as the bones rub together. As a result, a grinding sound will be heard. What is interesting is that we can often hear when a disc is partially displaced, and that is why we need to differentiate between rotation and translation of the condyle. We want to differentiate if we hear the ‘grinding’ sounds when the patient is only translating (meaning a lateral pole displacement) or the friction sounds in both rotation (medial pole displacement) and in translation? I have never witnessed a medial pole displacement without a lateral pole displacement. I have been taught that it is not possible because if there is a medial pole displacement there is always a full displacement of the disc.
Listening to the patient’s joints, with the patient listening as well, has been invaluable in helping patients understand their TMJ situation. It helps the conversation with the patient about what might be happening in the joint and why imaging, such as an MRI, would be helpful to get a better understanding of the joints.
It is important to remember that the doppler is only one of the tools used to evaluate the health of the TM joints. Oral examination, muscle evaluation, imaging, and radiographic findings from CT scans and MRI’s are all essential in making full assessments.
The doppler that I use is from Great Lakes Dental, a company that makes a number of different materials that I use in my dental practice. The model that they offer today is an update of the model that I have used for many years in practice. If you are interested in seeing the doppler ‘in-action
’ check out our video series in our clinical ‘mini-tip’ section.
→ Send me your questions on our social page. Yours for better dentistry,
