Toothaches and Biomechanics
I spend lots of time trying to relieve patients from painful teeth. Of course, there are numerous causes of tooth pain, but today, I want to focus on a prevalent and typically easy-to-treat one that has to do with the forces we place on our teeth called hyperocclusion. Hyperocclusion is when we generate forces that exceed the ability of our teeth and supporting structures. As I always say, teeth should glide together, not collide together. I will speak more about it later, but first, I should warn you that this post is not intended to diagnose or treat any condition, so if you have a painful tooth, please see your dentist immediately. To understand hyperocclusion, I need to give a little background.
Biomechanics
In humans, biomechanics often refers to the study of how the skeletal and musculature systems work under different conditions. In biomechanics, more generally, scientists try to apply physics and other mathematically based forms of analysis to discover the limits and capabilities of biological systems. I promise not to use math in this post, so don't worry. 1
Occlusion
The general term for the way teeth enmesh and function is called occlusion. But occlusion goes beyond the way the teeth fit together. Instead, occlusion is more comprehensively defined biologically as the coordinated functional interaction between the various cell populations forming the masticatory system as they differentiate, model, remodel, fail, and repair. 2 To be clear, most of us don't have ideal occlusion, but our teeth, gums, ligaments, and jaws have adapted and are symptom-free.
Hypo-occlusion
I may have coined the term hypo-occlusion because I could find no reference to it online. But I use the term to define forces that are too weak to stimulate the proper development and function of the supporting structures called the periodontium. The periodontium is collectively the outer layer of the root called cementum, the periodontal ligament that cushions and holds the tooth to the bone, the bone surrounding the root (alveolar bone), and the gums (gingiva). Too weak forces cause thinning of the periodontal ligament, atrophy of the fibers, alveolar bone osteoporosis, and bone height reduction. The reasons for insufficient forces include:
An open bite where some teeth are apart when others are closed together.
Loss of the opposing tooth.
Chewing on one side exclusively.
Chewing soft food
The most apparent reason, at least to me, is our soft modern diet. I wrote about our modern diets regularly, primarily how it has caused most of us to have smaller jaws than our ancestors here. The jaws in their entirety are not considered part of the periodontium, but the forces of biting influence the entire jaw, skull, and muscles. 3
Malocclusion
After cavities (caries) and gum disease (periodontitis), teeth that fit poorly together (malocclusion) is the third most significant problem I see. The World Health Organization states that the prevalence of malocclusion is anywhere from 39 to 93%. 1 The range varies due to geographic variation because malocclusions are more prevalent among people who eat western diets. So the number of people with teeth that fit together poorly in my practice is closer to 93%. I have written about the classifications of occlusion and malocclusion before, so if you want more information, see this post. I must restate that the bite can be severely off, but the patient may still have no symptoms, pain, or inability to chew.
Proprioception
Proprioception, or kinesthesia, is the sense that lets us perceive the location, movement, and action of parts of the body. It encompasses a complex of sensations, including the perception of joint position and movement, muscle force, and effort. These sensations arise from signals of sensory receptors in the muscle, skin, teeth, and joints and from central signals related to motor output. 4 Although not technically part of biomechanics, proprioception allows us to sense unwanted forces before they become problematic.
Traumatic Occlusion
When teeth don't meet correctly, the forces generated from chewing are misdirected. If the misdirection is symptom-free because it is insignificant, or the patient does not bite very hard, it is not considered traumatic. So we must be careful to differentiate malocclusion from traumatic occlusion, which is the pain resulting from teeth not fitting together correctly. Other terms are occlusal disharmony, functional imbalance, or occlusal dystrophy. Once again, no matter how bizarre the occlusal relationship may appear is not traumatic if the supporting structures adapt to it without pain or damage. 4 We have four different kinds of teeth designed for differing tasks, some of which overlap. For more information on the subject, see this post. For example, if we try to use our front teeth to crush our food, it won't work, nor can we use our back teeth to slice foods like our front teeth. When we routinely misuse teeth, we can cause trauma. In short, scissors are not hammers and vice versa.
Hyperocclusion
Hyperocclusion occurs when opposing teeth don't meet correctly, and the excessive or misdirected force becomes painful. Hyperocclusion defines single pairs of opposing teeth. A broader definition where multiple teeth are involved is called traumatic occlusion. Once a force exceeds the reparative capacity of the tissues, it will remain traumatic and potentially painful. Hyperocclusion is so common that it is one of the main reasons why people want my attention, and it has many causes, so let me describe them:
Drifting teeth
Teeth can naturally shift throughout life. Things contributing to drift are missing teeth, broken teeth, habits like thumb shucking, incorrect lip, cheek, and tongue position and motion, and natural forward drift known as mesial migration.
Orthodontic Movement
When teeth are intentionally being moved, as with orthodontia, they can transiently hit incorrectly while on their way to a better position. Luckily this condition is temporary but may require attention while it occurs. Additionally, when teeth are done moving, the bite often requires adjustments. When the dentist does this, it is known as occlusal equilibration.
New and Old Dental Work
When teeth are repaired, materials are added, potentially causing the bite to change. As mentioned earlier, the patient will perceive the difference when the teeth hit in new ways due to the proprioception. I often need to leave the tooth in a lighter state of occlusion so that the patient does not leave the office suspecting the bite is not correct. This is normal; the bite will adjust quickly due to natural tooth migration. However, sometimes the new work will cause hyperocclusion, either because the bite is too heavy, the force is in the wrong spot, the force is in the wrong direction, or any combination. Conversely, old dental work can also cause a problem. Old fillings and dentures can loosen, causing the bite to shift.
Clenching, Bruxism, and Chewing Gum
Patients often clench or grind while working, working out, concentrating, or sleeping. Dental clenching is known as bruxism. Additionally, gum and ice chewing can place undue pressure on teeth and result in pain and inflammation. A significant cause of clenching and grinding is poor breathing while sleeping because the brain sends signals to the jaw to move to take the tongue with it and help widen the airway.
Malocclusion
When the teeth don't function harmoniously because they are misaligned, improper forces arise. If the forces are in the wrong direction, on the wrong part of the teeth, or are too strong, the tissues can become traumatized, causing pain.
Trauma and Other Pathology
Sometimes, trauma can cause hyperocclusion. For example, when the jaw is fractured, it can shift how the teeth fit, causing hyperocclusion. Also, teeth can be knocked out of position, resulting in it. Finally, growths and infections can alter the bite. Untreated cysts commonly push teeth into new positions, potentially causing hyperocclusion.
Ectopic Eruptions
Sometimes teeth grow into the mouth in the wrong place. Small jaws won't allow some teeth, particularly lower anterior teeth, to erupt correctly, sometimes causing one to be outside the line of the dental arches. When this happens, the teeth may collide with each other every time the teeth come together.
Where Does the Pain Come From?
The tooth's connection to the jaw is a kind of joint called a gomphosis. The ligamental connection allows a tiny bit of movement to cushion the bite. But it has limitations. The pain occurs because the ligament holding the tooth to the jaw either gets compressed beyond its capacity or the pressure is in the wrong direction, both of which cause inflammation. Additionally, the nerve in the tooth can be irritated, causing temperature sensitivity, mostly to cold liquids. Muscle pain, joint pain in the jaw joint (temporomandibular joint or TMJ), headaches, ringing in the ears, and dizziness can also result.
The Treatment
Simple treatment involves slightly reshaping the offending tooth; as mentioned earlier, this is called equilibration. However, teeth may move again due to their natural tendency to do so, and the problem may recur. This is more likely to happen with malocclusion, missing teeth, worn dentition, or broken teeth. Constant equilibration can leave the enamel thin and cause sensitivity, so it is not a viable treatment option. Depending on the specific problems the patient presents with, replacing teeth, moving teeth, fixing teeth, making an occlusal guard for clenchers, making an apnea appliance for people with poor airways, or even removing teeth may be a more long-lasting solution.
Conclusion
Simple hyperocclusion is common; a minor bite adjustment will do the trick in most instances. But because of the complexities I mentioned in this post, you must never assume that an achy tooth is from hyperocclusion. For example, the pressure from an abscess will push the tooth up out of the socket, causing hyperocclusion. Obviously, adjusting the bite will never correct for the infection. Additionally, only a qualified dentist can assess the stability of a tooth's position to know if a simple equilibration will succeed. Lastly, the dentist should be able to determine all the factors resulting in hyperocclusion and provide comprehensive treatment strategies for the long-term health and function of your teeth.