In the context of dentistry, occlusion refers to the contact between the teeth, specifically the upper and lower rows of teeth. Static occlusion is the term used to refer to the contact made between the rows of teeth when the jaw is closed and unmoving, while dynamic occlusion is the term that refers to contact made between the rows of teeth when the jaws are moving, as in the act of chewing. The system involved in chewing, also known as the masticatory system, involves these rows of teeth, along with the jaw and the temporomandibular joint, the gums, and the neuromusculature of the jaws and mouth. In order to understand occlusion and its mechanics, it is helpful to understand the surrounding anatomical components.
There are 32 permanent teeth in an adult human’s mouth; the top row of teeth is called the maxillary arch, and the bottom row of teeth is called the mandibular arch. The teeth rest in the alveolar bone in each arch. Each tooth is made up of the crown, which is the portion of the tooth that is visible above the gumline, and the root, which is the portion of the tooth that rests in the alveolar bone and cannot be seen beneath the gums. The teeth roots are attached to the alveolar bone by a ligament, called the periodontal ligament, which also protects the bone from forces applied to the teeth while chewing. The maxillary and mandibular jaws are connected by the temporomandibular joint, and various muscles and ligaments hold the masticatory system in place, protecting the elements and allowing the system to function effectively.
When the baby teeth begin emerging, they are molded into place by the tongue, the cheeks, and the lips, which help the teeth emerge in proper alignment and to occlude properly. As the jaws continue to grow, the amount of space around individual teeth increases, which provides sufficient space for the permanent teeth to erupt properly, with correct occlusion. If there is an overbite or underbite present, or if the occlusion is otherwise mechanically sub-optimal, this is known as malocclusion. There are many sub-classifications of malocclusion and occlusal interference, which is any tooth contact that interferes with proper mechanics. The classifications of malocclusion and occlusal interference are important in orthodontic diagnoses and treatments. Occlusal interferences may also be created by dental restorations, like fillings; if the filling is not filed down completely, it may affect the bite and cause pain or discomfort in the muscles of the jaw. These occlusal interferences can usually be easily repaired by a dentist. Each person has their own ideal or perfect occlusion, which is best defined as when the upper and lower teeth work together, and rest together, harmoniously and painlessly. Most people can adapt easily to small changes in occlusion and can self-adjust.
If a patient experiences pain or excessive wear of the teeth or notices the teeth drifting in place, an occlusal examination is recommended. Occlusal examinations are also necessary before any major restorative treatment is planned, as minor occlusal discrepancies may lead to symptoms in the jaw joint or other areas of the mouth once restorations are placed. Occlusal examinations gauge the bite of the patient from within the mouth, using a set of dental tools, and they also require the observation of the facial symmetry of the patient. Dentists will also assess the masticatory muscles during an occlusal examination, along with other muscles in the area of the jaw, to determine whether there is any temporomandibular dysfunction. Major occlusal adjustments may require oral surgery, orthodontic treatment, or a combination of the two, while simple occlusal adjustments can often be made by minor reshaping of certain teeth. Occlusal adjustments improve patient comfort, increase the stability of the teeth and of the occlusion, help maintain the life of dental restorations, and provide the optimal aesthetic result.