By Lee Ann Brady, DMD The fabrication of occlusal appliances is probably the most variable dental treatment I can think of. The type of appliance, fabrication technique, occlusal scheme, and fee are different from practice to practice. You may be thinking, we should come to a consensus or that there are appliances that are “better” than others. I embrace the variety, but the determination of which appliance design to use should be based on exam findings and diagnosis from patient to patient — not from office to office.ALSO BY DR. LEE ANN BRADY | Choosing the right all-ceramic material There are more named appliance designs than I can list, but the good news is that they are all based on a small number of designs. The design of the appliance, specifically the occlusion it creates, is what determines how and when it works. There are two ways we alter the patient’s occlusion with an appliance. First, we change intercuspal position. In doing so, we impact muscle force and engagement, joint loading, and condylar position. Appliances also create a new anterior guidance relationship. In turn, this relationship affects muscle force and engagement and joint loading. The activation and engagement of the elevator muscles is controlled by tooth contacts. We know from the literature that the further back in the arch we have tooth contact, the greater the muscle engagement and the potential force delivered across the system. When we look at occlusal designs that include second molar contact vs. only anterior teeth, you can get five to eight times the total force created. Whether in ICP or excursive movements, our goal is to reduce or minimize the force, so we eliminate posterior tooth contacts. Reducing the force and engagement of the elevator muscles should reduce muscle tension and tenderness and minimize the destruction of the teeth during parafunction. Joint loading is a function of the position of the tooth contacts in the arch and total force. Occlusal designs that include posterior teeth deliver approximately 15% of the total force through the joint. When we eliminate the posterior teeth from the occlusal scheme, the ratio changes to 65% of the total force being delivered through the joint. The key is that in both scenarios it is a percentage of the total force the joint receives. If we can minimize the force across the system by eliminating posterior tooth contacts significantly enough, then we are reducing the actual joint load. For instance, if the total force with all teeth contacting is 100lb/cm2, the joint receives 15% or 15 lb/cm2. In the same patient, if we temporarily eliminate the posterior contacts on an appliance (ICP or excursions) and reduce the total force to 20lb/cm2, the joint receives 65% or 13lb/cm2. The relationship between joint loading and muscle engagement has to be managed based on the patient’s exam findings. All occlusal appliances alter vertical dimension, which in turn will cause a reduction in total muscle force. The challenge is that this reduction is often temporary and adaptation to the new vertical occurs in about 90 days. Appliances can also be used to alter condylar position, whether for therapeutic or restorative purposes. I use five appliance designs in my practice: Anterior Only, Posterior Only, Full-Coverage Flat, Full-Coverage Anatomic, and Full-Coverage Soft.Anterior-only appliances eliminate posterior tooth contacts in both intercuspal position and excursive movements. The intention is to decrease muscle engagement and force. If the total force is dropped enough (patient dependent), this appliance design will also decrease joint loading. I use these appliances for patients with healthy joints that have muscle signs and symptoms and to find a seated condylar position. The risk is tooth movement (anterior intrusion or posterior super-eruption), although there are alternative designs that cover all the upper and lower teeth.
Anterior bite plane appliancePosterior-only appliances maintain posterior tooth contact in intercuspal position and excursive movements. The intention is to minimize joint loading in all mandibular positions. These appliances are used for patients with disc displacements and pain on loading. As with anterior only, this appliance design presents a risk of tooth movement (anterior super-eruption and posterior intrusion); additionally muscle activity can increase.Full-coverage flat appliances create anterior-only tooth contacts in excursives, minimizing muscle force due to the absence of posterior tooth contact and the low interincisal angle. In intercuspal position, even contacts are created around the arch using the teeth to absorb the majority of the load. These appliances can be used to find seated condylar position if adjusted over time as the muscles release. I use full-coverage flat plane appliances for patients with symptomatic muscles who also have joint signs or symptoms.
Full-coverage flat plane applianceFull-coverage anatomic appliances also create anterior-only tooth contacts in excursions with even intensity intercuspal contacts around the arch. The main difference between this and a flat plane appliance is we use the surface of the appliance to create a new occlusal scheme. We determine on the plastic it works, stabilizes joints, muscles and dentition and then we can copy it to the teeth in the final treatment plan. In my practice this is my pre-restorative or pre-orthodontic appliance of choice because of the information gathered.
Full-coverage anatomicFull-coverage soft appliances are designed much like a posterior only to create contacts around the arch in both intercuspal position and excursive movements. This design has the teeth taking the majority of the load across the system. Both the posterior tooth contacts and the squish factor can have some patients significantly increase muscle activity and load in this style of appliance. I utilize this design for patients with an acute lateral pterygoid spasm, following acute injury that resulted in joint inflammation or who have chronic joint pain on excursive loading due to a disc displacement. All of these appliances have a place in your practice based on the individual patient you are treating. They all have multiple fabrication techniques that can be done in-office or at a laboratory. When it comes to fees, I encourage that you look at your time and number of adjustment appointments as well as the cost of fabrication and determine an individual fee for each patient. So we are back to where we started, I am an advocate of variety in appliance therapy.
Dr. Lee Ann Brady earned her DMD degree from the University of Florida College of Dentistry. Her practice experience has been rich and varied. For 17 years, she worked in a variety of practice models from small, fee-for-service offices to large, insurance-dependent practices as an associate and a practice owner. She was invited to join The Pankey Institute in January 2005 as its first female resident faculty member and was promoted to clinical director within a year. She was asked by Dr. Frank Spear to join him in the formation of Spear Education and the expansion of his curriculum in September 2008 as executive vice president of clinical education. This year, Dr. Brady launched her website, www.leeannbrady.com, to offer clinical and practice content daily. In addition to being a dedicated educator, she maintains a private practice in Glendale, Ariz.
