Dental occlusion refers to the contact between the teeth of the upper jaw, or maxillary teeth, and the teeth of the lower jaw, or mandibular teeth. Static dental occlusion refers to the contact between teeth when the jaw is at rest and dynamic occlusion occurs when the jaw moves, as happens during chewing, or mastication. Proper occlusion is important for dental health and general health.
When the mandibular teeth’s cusps come to full interaction with the cusps of the upper teeth, the occlusal position is called maximum intercuspation. The cusps of a tooth are the protruding parts at the top of the tooth, as opposed to the center groove at the top of the tooth. The natural position achieved during maximum intercuspation is called centric occlusion, or the habitual bite. This occlusion may also be called the bite of convenience, or intercuspation position (ICP), and in simple terms, means the natural position of the teeth when the teeth fully bite. Dental occlusion depends on bone structure, muscles, nerves, teeth structure, and sometimes posture.
A proper habitual bite means that there is no underbite, overbite, or crossing of teeth. In a young person with an ideal bite, all teeth should make contact. If that patient shifts the jaw to one side, the eye tooth, or lower canine should slide over the upper canine so that the posterior, or back, teeth no longer touch and the lower jaw drops slightly. This is called canine guidance. Anterior guidance in an ideal bite occurs when the person pushes his jaw forward and the lower front teeth slide up over the front teeth, so that the back teeth do not touch.
An ideal bite should also have proper centric relation, the resting position of the temporomandibular joint (TMJ), or jaw joint. This means that the ball of the joint is in a central location in the socket. The individual positions of the teeth may vary from person.
A malocclusion occurs when the teeth and jaws are misaligned in the habitual bite. Though most people have a slight degree of malocclusion and do not require treatment, this condition can cause health issues in the temporomandibular joint, teeth, jaw muscle, and gums. Malocclusions are normally categorized with Angle’s classification method, set up by Edward Angle, a prominent orthodontist of the late 19th and early 20th centuries. The classifications are based on the position of the maxillary first molar in relation to the rest of the occlusion.
Class I has normal molar occlusion, but other teeth may have crowding or eruption over or under its intended place. A common example of an over eruption occurs when the canine tooth pushes through the gum labially, above the primary tooth. Class II is commonly known as an overbite, in which the upper teeth are place too far forward. Class III includes patients with underbites, in which the anterior mandibular teeth come in front of the upper anterior teeth. Worn down teeth, from overactive jaw muscles, grinding, and eventual lack of canine guidance, can also cause malocclusion to occur. These conditions can be treated with dental braces, tooth extraction, and sometimes orthognathic, or jaw, surgery.