It is routine to see patients with lower incisal edges that are worn into the dentin. The wear can be from attrition or from erosion, and is often a combination of the two. When dentin is exposed and the wear is progressing at a rate that is not age appropriate I want to do something to protect these teeth and slow the progression of the damage. When I think about possible restorative options I want to do what is appropriate, stay conservative if possible and manage the restorative challenges that are present with lower incisors due to their size and shape. These factors combined with the fabulous properties of our new composites have me using direct composite more and more in these situations.
Last week teaching a hands on equilibration course one of the participants told a story about a new patient to his office who was in active appliance therapy and frustrated because the former dentist wouldn’t move to the next step of the treatment plan and the patient felt “stuck” in the appliance. His question to me was whether it was wise to move ahead with definitive restorative therapy. So when is appliance therapy complete? The answer to that question hinges on your reasons for placing a patient in an appliance.
I know even the mention of the words centric relation probably has some readers bristling, as this is a much argued over topic. With that said the research by Lundeen and Gibbs at the University of Florida shows that we do seat our condyles into the fossa during the chewing stroke. This seated condylar position is often used as a reference position to treat patients whether as part of reorganizing their occlusion to alleviate TMD symptoms or for restorative or orthodontic treatments. The next question is do people seat their condyles other than during normal function as part of the chewing stroke. I believe the answer is yes. One of the pieces of evidence is the number of patients that I have with wear facets that correspond exactly to their first point of contact with their condyles seated. These same patients do not mark this area with articulating paper in intercuspal position or when following their excursives.
Blunting or shortening of the roots of teeth that have been moved orthodontically is commonly seen. In reviewing the orthodontic literature I learned that there is a distinction between mild root resorption and significant. If we look at any loss of root length using radiographs the number of cases where it presents is very high, estimated in some studies to be upwards of 70%. However this loss of a fraction of a millimeter of root length is not clinically impactful and often not noted on radiographs unless measurements are taken. Significant root resorption, which has clinical implications of mobility and potential premature loss of the tooth, is much less common. Studies show varying frequencies from 4-18%, depending on factors like pre-op root shape, the orthodontic mechanics used, presence of congenitally missing teeth, extraction etc.
Over the years, I have treated numerous patients with “significant” root resorption and have always found managing the occlusal forces to be a critical factor. Mobility is one of the classic findings on incisors with significant resorption, and can be very concerning to the patient as well as the dental team. One of the first things I want to do when this situation presents is an occlusal analysis. The existing functional occlusion needs to be understood in intercuspal position, end to end and excursive movements to assess the force on the mobile teeth. The next question is how you might alter the functional occlusion to reduce the forces. If I believe I can improve the mobility through altering the patients occlusion I will test this with an appliance. Based on positive results we can then make those same occlusal changes to the teeth.
One of the ways I work together with the orthodontist is to diagnose root resorption and the need to manage the occlusion prior to the removal of the brackets. I have been truly amazed with the resolution of mobility and the longevity of incisors with very severe root resorption once the forces are exquisitely controlled.
Are you willing to make adjustments to an occlusal appliance that you did not make? Over the years I have met dentists who “never” adjust an appliance that was made by another dentist, and others who are willing to. In my experience either way it is a challenging situation and a challenging discussion with the patient. One of the key pieces I have learned over the years is whether I made the occlusal appliance or not, the instant I adjust it I am fully responsible for it. That means if it works I win, but if the patient continues to have problems, or no resolution of symptoms I am responsible. Challenge number two, is that without a complete joint, ,muscle and occlusal exam I am not fully versed in the patient’s condition and the goals of appliance therapy. therefore I do not know how the appliance should be adjusted to gain maximum benefit. The last piece of the puzzle is figuring out a fair fee for adjusting an appliance.
A critical piece of joint diagnosis is being able to differentiate the sounds we hear using auscultation. Based on the way load is applied in varying positions we know that in a seated condylar position and through rotation the load is on the medial aspect of the condyle/disc assembly. During translation the load moves out to the lateral aspect. By listening to the joint during rotation, which is the first 10mm or so of opening and the condylar movement on the working side during an excursive we can get information about the disc position. Translation occurs when listening on the balancing side during an excursive or during the rest of the opening movement.
In a previous post this year I talked about patients who are at risk of developing a “pop or click” and the importance of identifying this risk. This video clip is a segment of the first session of “Occlusal Diagnosis: Identifying Risk”, a six credit hour online seminar I offer once a year. In this segment I discuss the concept of ligament laxity, the anatomic condition that contributes to it, and the steps in diagnosis.
In Part two I continue the conversation about the relationship between the joint load and the occlusal contacts we create when we design an occlusion. That occlusion can be transitional on an appliance or final, created using an equilibration or restorative dentistry. Joint load is one of three considerations when designing an occlusion for a patient with a history of TMD or wear. We need to think about the relationship of the contacts to the joint load, the muscle engagement and the force across the teeth. An upcoming hands on program
Designing the occlusion for a patient with a history of joint issues can be challenging. Understanding where the disc is in relation to the head on the condyle in intercuspal position and excursions is a critical piece of diagnostic information, as well as inflammation and discomfort in different positions. One of the ways we can stabilize the Temporomandibular joint and minimize or eliminate inflammation and symptoms is by managing joint loading. In this first of two videos I look at the concept of joint loading and how we can use occlusal contacts to alter it. An upcoming hands on program I will be teaching at The Pankey Institute addresses restoring the occlusally compromised patient, whether the compromise is joints, muscles or wear.
In yesterday’s post I discussed the factors that impact wear resistance in modern composite materials. The great news is that we only have to think about the wear resistance of composite in areas of direct occlusal contact. The second piece of good news is that very few composite restorations are replaced because of excessive wear. The majority of restorations succumb to marginal breakdown and leakage, secondary caries or other forms of bond failure. Now, the bad news is that bond failure and bond degradation is accelerated under extreme occlusal load. With all of this in mind it makes sense to manage excessive forces and material selection to increase longevity of our restorations.