malocclusion malocclusion in orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. the english-language term dates from 1864; edward angle (1855-1930), the "father of modern orthodontics", popularised it. the word "malocclusion" derives from occlusion, and refers to the manner in which opposing teeth meet (mal- + occlusion = "incorrect closure"). malocclusionmalocclusion in 10-year-old girlspecialtydentistry look up bucktooth in wiktionary, the free dictionary. the malocclusion classification is based on the relationship of the mesiobuccal cusp of the maxillary first molar and the buccal groove of the mandibular first molar. if this molar relationship exists, then the teeth can align into normal occlusion. according to angle, malocclusion is any deviation of the occlusion from the ideal. however, assessment for malocclusion should also take into account aesthetics and the impact on functionality. if these aspects are acceptable to the patient despite meeting the formal definition of malocclusion, then treatment may not be necessary. causes the aetiology of malocclusion is somewhat contentious, however, simply put it is multifactorial, with influences being both genetic and environmental. malocclusion is already present in one of the skhul and qafzeh hominin fossils and other prehistoric human skulls. there are three generally accepted causative factors of malocclusion: skeletal factors – the size, shape and relative positions of the upper and lower jaws. variations can be caused by environmental or behavioral factors such as muscles of mastication, nocturnal mouth breathing, and cleft lip and cleft palate. muscle factors – the form and function of the muscles that surround the teeth. this could be impacted by habits such as finger sucking, nail biting, pacifier and tongue thrusting dental factors – size of the teeth in relation to the jaw, early loss of teeth could result in spacing or mesial migration causing crowding, abnormal eruption path or timings, extra teeth (supernumeraries), or too few teeth (hypodontia) there is not one single cause of malocclusion, and when planning orthodontic treatment it is often helpful to consider the above factors and the impact they have played on malocclusion. these can also be influenced by oral habits and pressure resulting in malocclusion. behavioral and dental factors in the active skeletal growth, mouthbreathing, finger sucking, thumb sucking, pacifier sucking, onychophagia (nail biting), dermatophagia, pen biting, pencil biting, abnormal posture, deglutition disorders and other habits greatly influence the development of the face and dental arches. pacifier sucking habits are also correlated with otitis media. dental caries, periapical inflammation and tooth loss in the deciduous teeth can alter the correct permanent teeth eruptions. primary vs. secondary dentition malocclusion can occur in primary and secondary dentition. in primary dentition malocclusion is caused by: underdevelopment of the dentoalvelor tissue. over development of bones around the mouth. cleft lip and palate. overcrowding of teeth. abnormal development and growth of teeth. in secondary dentition malocclusion is caused by: periodontal disease. overeruption of teeth. premature and congenital loss of missing teeth. signs and symptoms malocclusion is a common finding, although it is not usually serious enough to require treatment. those who have more severe malocclusions, which present as a part of craniofacial anomalies, may require orthodontic and sometimes surgical treatment (orthognathic surgery) to correct the problem. the ultimate goal of orthodontic treatment is to achieve a stable, functional and aesthetic alignment of teeth which serves to better the patient's dental and total health. the symptoms which arise as a result of malocclusion derive from a deficiency in one or more of these categories. the symptoms are as follows: tooth decay (caries): misaligned teeth will make it more difficult to maintain oral hygiene. children with poor oral hygiene and diet will be at an increased risk. periodontal disease: irregular teeth would hinder the ability to clean teeth meaning poor plaque control. additionally, if teeth are crowded, some may be more buccally or lingually placed, there will be reduced bone and periodontal support. furthermore, in class iii malocclusions, mandibular anterior teeth are pushed labially which contributes to gingival recession and weakens periodontal support. trauma to anterior teeth: those with an increased overjet are at an increased risk of trauma. a systematic review found that an overjet of greater than 3mm will double the risk of trauma. masticatory function: people with anterior open bites, large increased & reverse overjet and hypodontia will find it more difficult to chew food. speech impairment: a lisp is when the incisors cannot make contact, orthodontics can treat this. however, other forms of misaligned teeth will have little impact on speech and orthodontic treatment has little effect on fixing any problems. tooth impaction: these can cause resorption of adjacent teeth and other pathologies for example a dentigerous cyst formation. psychosocial wellbeing: malocclusions of teeth with poor aesthetics can have a significant effect on self-esteem. malocclusions may be coupled with skeletal disharmony of the face, where the relations between the upper and lower jaws are not appropriate. such skeletal disharmonies often distort sufferer's face shape, severely affect aesthetics of the face, and may be coupled with mastication or speech problems. most skeletal malocclusions can only be treated by orthognathic surgery. classification depending on the sagittal relations of teeth and jaws, malocclusions 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 malocclusion) 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 and 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 class i with severe crowding and labially erupted canines class ii molar relationship edward angle, who is considered the father of modern orthodontics, was the first to classify malocclusion. 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 malocclusion types. it is also possible to have different classes of malocclusion 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 malocclusions 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 malocclusion 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 by ricketts 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 crowding of teeth dental crowding is defined by the amount of space that would be required for the teeth to be in correct alignment. it is obtained in two ways. 1) by measuring the amount of space required and reducing this from calculating the space available via the width of the teeth. or 2) by measuring the degree of overlap of the teeth. the following criterion is used: 0-4mm = mild crowding 4-8mm = moderate crowding >8mm = severe crowding causes genetic (inheritance) factors, extra teeth, lost teeth, impacted teeth, or abnormally shaped teeth have been cited as causes of crowding. ill-fitting dental fillings, crowns, appliances, retainers, or braces as well as misalignment of jaw fractures after a severe injury are also known to cause crowding. tumors of the mouth and jaw, thumb sucking, tongue thrusting, pacifier use beyond age three, and prolonged use of a bottle have also been identified. lack of masticatory stress during development can cause tooth overcrowding. children who chewed a hard resinous gum for two hours a day, showed increased facial growth. experiments in animals have shown similar results. in an experiment on two groups of rock hyraxes fed hardened or softened versions of the same foods, the