Depending on the sagittal relations of teeth and jaws,<unk> s can be divided mainly into three types according to Angle's classification system published 1899. However, there are also other conditions, e.g. crowding of teeth, not directly fitting into this classification. Many authors have tried to modify or replace Angle's classification. This has resulted in many subtypes and new systems (see section below: Review of Angle's system of classes). A deep bite (also known as a Type II<unk>  is a condition in which the upper teeth overlap the lower teeth, which can result in hard and soft tissue trauma, in addition to an effect on appearance. It has been found to occur in 15–20% of the US population. An open bite is a condition characterised by a complete lack of overlap and occlusion between the upper and lower incisors. In children, open bite can be caused by prolonged thumb sucking. Patients often present with impaired speech and mastication. Overbites This is a vertical measurement of the degree of overlap between the maxillary incisors and the mandibular incisors. There are three features that are analysed in the classification of an overbite: * Degree of overlap: edge to edge, reduced, average, increased * Complete or incomplete: whether there is contact between the lower teeth the opposing teeth/tissue (hard palate or gingivae) or not. * Whether contact is traumatic or atraumatic An average overbite is when the upper anterior teeth cover a third of the lower teeth. Covering less than this is described as ‘reduced’ and more than this is an ‘increased’ overbite. No overlap or contact is considered an ‘anterior open bite’. Angle's classification method labially erupted canines Class II molar relationship Edward Angle, who is considered the father of modern orthodontics, was the first to classify<unk> . He based his classifications on the relative position of the maxillary first molar. According to Angle, the mesiobuccal cusp of the upper first molar should align with the buccal groove of the mandibular first molar. The teeth should all fit on a line of occlusion which, in the upper arch, is a smooth curve through the central fossae of the posterior teeth and cingulum of the canines and incisors, and in the lower arch, is a smooth curve through the buccal cusps of the posterior teeth and incisal edges of the anterior teeth. Any variations from this resulted in<unk>  types. It is also possible to have different classes of<unk>  on left and right sides. *Class I (Neutrocclusion): Here the molar relationship of the occlusion is normal but the incorrect line of occlusion or as described for the maxillary first molar, but the other teeth have problems like spacing, crowding, over or under eruption, etc. *Class II (Distocclusion (retrognathism, overjet, overbite)): In this situation, the mesiobuccal cusp of the upper first molar is not aligned with the mesiobuccal groove of the lower first molar. Instead it is anterior to it. Usually the mesiobuccal cusp rests in between the first mandibular molars and second premolars. There are two subtypes: *Class II Division 1: The molar relationships are like that of Class II and the anterior teeth are protruded. *Class II Division 2: The molar relationships are Class II but the central are retroclined and the lateral teeth are seen overlapping the centrals. *Class III: (Mesiocclusion (prognathism, anterior crossbite, negative overjet, underbite)) In this case the upper molars are placed not in the mesiobuccal groove but posteriorly to it. The mesiobuccal cusp of the maxillary first molar lies posteriorly to the mesiobuccal groove of the mandibular first molar. Usually seen as when the lower front teeth are more prominent than the upper front teeth. In this case the patient very often has a large mandible or a short maxillary bone. Review of Angle's system of classes and alternative systems A major disadvantage of Angle's system of classifying<unk> s is that it only considers two dimensions along a spatial axis in the sagittal plane in the terminal occlusion, but occlusion problems can be three-dimensional. It does not recognise deviations in other spatial axes, asymmetric deviations, functional faults and other therapy-related features. Angle's classification system also lacks a theoretical basis; it is purely descriptive. Its much-discussed weaknesses include that it only considers static occlusion, it does not account for the development and causes (aetiology) of occlusion problems, and it disregards the proportions (or relationships in general) of teeth and face. Thus, many attempts have been made to modify the Angle system or to replace it completely with a more efficient one, but Angle's classification continues be popular mainly because of its simplicity and clarity. Well-known modifications to Angle's classification date back to Martin Dewey (1915) and Benno Lischer (1912, 1933). Alternative systems have been suggested by, among others, Simon (1930, the first three-dimensional classification system), Jacob A. Salzmann (1950, with a classification system based on skeletal structures) and James L. Ackerman and William R. Proffit (1969). Incisor classification Besides the molar relationship, the British Standards Institute Classification also classifies<unk>  into incisor relationship and canine relationship. Class I: The lower incisor edges occlude with or lie immediately below the cingulum plateau of the upper central incisors Class II: The lower incisor edges lie posterior to the cingulum plateau of the upper incisors Division 1 – the upper central incisors are proclined or of average inclination and there is an increase in overjet Division 2 – The upper central incisors are retroclined. The overjet is usually minimal or may be increased. Class III: The lower incisor edges lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed. Canine relationship Class I: Mesial slope of upper canine coincides with distal slope of lower canine Class II: Mesial slope of upper canine is ahead of distal slope of lower canine Class III: Mesial slope of upper canine is behind to distal slope of lower canine
Malocclusion
Splenosis
Venous leak
Inspissation
Needle remover
Defecation
Anaplasia
Subluxation