|Classification and external resources|
Overbite commonly refers to a lower jaw being too far behind the upper jaw (retrognathia) or a misalignment of the teeth. Medically, the term refers to the extent of vertical (superior-inferior) overlap of the maxillary central incisors over the mandibular central incisors, measured relative to the incisal ridges.
The term overbite does not refer to a specific condition, nor is it a form of malocclusion. Rather an absent or excess overbite would be a malocclusion. Normal overbite is between 3–5 mm (or approximately 20–30% of the height of the mandibular incisors) and is commonly expressed as a percentage.
Young children commonly have a deep bite (excessive overbite), it is not resolved during the normal growth of the maxilla and the mandible and can get worse with time. If it is not corrected it may lead to trauma and shortening the length of the teeth due to wear and the biting edges.
Other terms confused with "overbite"
Overbite is often confused with overjet, which is the distance between the maxillary anterior teeth and the mandibular anterior teeth in the anterior-posterior axis.
"Overbite" may also be used commonly to refer to Class II malocclusion or retrognathia, though this usage can be considered incorrect. This is where the mesiobuccal cusp of the maxillary first molar is situated anterior to the buccal groove of the mandibular first molar; in other words, the mandible (lower jaw) appears too far behind the maxilla. A person presenting with Class II malocclusion may exhibit excessive overbite as well, or may have the opposite problem, which is referred to as openbite (or apertognathia). In the case of apertognathia, the teeth do not overlap enough or at all. The upper teeth protrude past the lower teeth.
Changing human dentition
American anthropologist C. Loring Brace, has brought forth a theory that the human overbite of Europeans is only about 250 years old and this shift was the result of the widespread adoption of the table knife and fork. Before the use of cutlery, Europeans would often clamp their teeth on a piece of meat and then cut off a piece with a knife. When Europeans started using forks and knives, the cutting was done on the plate and the overbite became much more common. Brace also researched the Chinese, who had adopted chopsticks 900 years earlier and found the instances of overbites increased about the same time the new eating method was introduced.