Dr. Ryan Swain Printer Friendly Version

Moving Beyond "Occlusion Confusion"

Over the last five years I’ve been on a pursuit to understand occlusion and simplify the topic in a new and insightful manner. As is oftentimes the case, taking a big step back and looking at this complicated subject in a simple and pragmatic fashion will allow us to see some basic truths that perhaps were previously hidden from us.

I’d like to start by stating two easily observable and scientifically proven facts about occlusion:

1. Teeth do not touch with any significant force during normal mastication
2. Canine guidance and protrusive guidance are never used during normal mastication

When I state these ideas during my lectures, I can feel the skepticism in the room. It’s an interesting moment. Based on what I understand, many of the dentists are thinking “those statements aren’t true” and others are thinking “I’ve never thought of that before.” I pause for a few seconds and savor the awkward atmosphere before moving on to an effective little exercise. We pass out a hard piece of candy to all of the attendees and ask them to eat the candy. As the room fills with the sound of crunching candy, I ask the attendees to follow my instructions. “Raise your hand when your teeth touch or when you are utilizing canine or protrusive guidances.” In four years, I have never had a single attendee raise their hand.

Many studies over the years such as those by Gibbs and Lundeen have shown clearly that our teeth do not touch during the normal chewing process. But, unlike most scientific studies, we can very easily test these findings by observing what happens in our own mouths. I’m continually amazed at how few of us actually use our own personal chewing experiences to think critically about the topic of occlusion. In many ways, this is quite ironic. We are highly trained dental professionals; we analyze and repair teeth on a daily basis but many of us haven’t taken the time to consider how or when our own teeth, muscles and oral structures actually function. I encourage you to take my “when do teeth touch?” challenge the next time you enjoy a meal. You’ll notice that your muscles of mastication pull your mandible towards your maxilla so that your upper and lower teeth can pulverize the bolus of food. This pattern continues until the bolus is broken down to a certain point. At this point, when upper and lower teeth are just about to touch, you stop chewing and you swallow the bolus. As you swallow you may notice that there is some light tooth contact but what you should also notice is that the force with which this contact occurs is extremely light.

If teeth do not touch during normal mastication, then it is important ask “when do they touch?” The answer is relatively simple. The only time that teeth touch with significant force is during parafunctional events. During these events, food is not present in the mouth. So, although teeth are primarily used to aid in our nourishment, they are essentially only damaged significantly through parafunction and trauma. When we understand this clearly, our treatment becomes more focused and effective.

Many dentists wonder why they can place a restoration in one patient’s mouth and it will endure for years while a similar restoration in a different patient’s mouth fails in just a few months. Dr. Frank Spear has described two categories of patients: high responders and low responders. High responders are the patients we see who seem to wear, crack and break anything that is placed in their mouths. These are also the patients who have extreme sensitivity to occlusal disharmonies that can be created when new restorations are placed. Low responders are the patients that rarely have dental problems and seem to adapt to just about any kind of dentistry that is performed in their mouths. What it boils down to is that the high responders are the only people who are actually putting their teeth together with any significant force. They are the clenchers and bruxers.

When we understand these relatively simple concepts we are able to cut through much of the fog that seems to hang around the area of occlusion and hone in on the most important aspects of helping our patients protect their teeth and restorations. Recognizing the signs associated with parafunction becomes a primary focus for us as clinicians. Educating the patients whom demonstrate these signs about their parafunctional habits becomes a significant part of our patient communication. Understanding the best methods and materials for parafunctional control also becomes imperative.

There are many types of guards and splints that can be used to help soften the blow of bruxing events. My personal choice for effective parafunctional control is the NTI-TSS device. The NTI-TSS (Neuro-Trigeminal Inhibition Tension Suppression System) provides a remarkably effective and easy way for dentists to help their patients protect their teeth and joints. The NTI device is a small and robust guard that is usually made to be worn on the lower incisors. The NTI provides for incisor-only contact which minimizes maximum biting force and muscle activity by approximately 65%. When patients cannot contact with canines or posterior teeth in any excursive movements, the masseter and temporalis muscles can only fire with a minimal amount of force. This provides many benefits for our patients including muscle tension suppression and decreased load to the TMJ’s. Since there is no tooth-to-tooth contact while wearing the NTI, there is no opportunity for tooth abrasion to occur as the result of bruxism.

Full arch nightguards have been fabricated and used successfully for many years. However, because of the size of a full arch splint, patient compliance is extremely poor. Additionally, adjusting a full arch splint can be quite cumbersome if any muscle relaxation and compensatory condylar seating occurs. Another negative characteristic of a full arch nightguard that many dentists haven’t considered is that a patient can still clench with 100% bite force while wearing even the most accurately adjusted full mouth orthotic.

The NTI can be easily fabricated chairside by a dental auxillary and adjustments are relatively easy because the incisors are the only teeth that come in contact with the guard. After making our NTI’s chairside for many years, we now submit these cases to Keller Laboratories for laboratory NTI-TSS fabrication. There is a slight increase in expense but the saved chairtime and increased quality in the finished device provide plenty of value for me, my staff and my patients.

I encourage you to consider some of the ideas that I have presented here. As dental professionals, our desire is to be experts in our field and use that expertise to benefit our patients. Occlusion poses an obstacle for many dentists because of the wide variety of opinions and conflicting evidence. I’m certain that if we take a step back and try to see the big picture, some of the topics within occlusion can become less complicated. If we stay focused on the science and also utilize our own experiences and pragmatism, we can move forward and progress beyond a state of “occlusion confusion.”

Dr. Ryan Swain is a graduate of the University of Florida College of Dentistry. He practices in Rochester, NY and focuses on Short Term Ortho and other conservative cosmetic dental procedures. He is president and chief clinical instructor for Six Month Smiles. Dr. Swain is a pioneer in the field of Short Term Ortho and constantly on the forefront of GP orthodontics. He has trained dentists internationally and prides himself on de-mystifying orthodontics for GPs. 

Dr. Swain can be reached at Drswain@thedentistsnetwork.net

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