View source for Malocclusion

{{short description|Misalignment between upper and lower teeth as the jaws close}}
{{redirect2|Deep bite|Buck teeth|the village|Deep Bight, Newfoundland and Labrador}}
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In [[orthodontics]], a '''malocclusion''' is a misalignment or incorrect relation between the [[teeth]] of the upper and lower [[dental arch]]es when they approach each other as the [[jaw]]s close. The English-language term dates from 1864;<ref>{{oed | malocclusion}}</ref> [[Edward Angle]] (1855–1930), the "father of modern orthodontics",<ref>{{Cite journal| vauthors = Bell B |date= September 1965 |title=Paul G. Spencer |journal=American Journal of Orthodontics |volume=51 |issue=9 |pages=693–694 |doi=10.1016/0002-9416(65)90262-9 |pmid= 14334001 |doi-access= }}</ref><ref name="Mouth">{{cite journal | last = Gruenbaum | first = Tamar | name-list-style = vanc | title = Famous Figures in Dentistry | journal = Mouth – JASDA | date = 2010 | volume = 30 | issue = 1 | pages = 18 }}</ref>{{qn|date=June 2021}} popularised it. The word derives {{ety||{{linktext|mal-}}|incorrect||[[occlusion (dentistry)|''occlusion'']]|the manner in which opposing teeth meet}}.

The malocclusion classification is based on the relationship of the mesiobuccal cusp of the [[maxillary first molar]] and the [[buccal (disambiguation)|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.<ref>{{Cite journal |last= Hurt|first=Mark A. | name-list-style = vanc |date=2012 |title=Weedon D. Weedon's Skin Pathology. 3rd ed. London: Churchill Livingstone Elsevier, 2010 |journal=Dermatology Practical & Conceptual |volume=2 |issue=1 |pages=79–82 |doi= 10.5826/dpc.0201a15 |pmc=3997252 }}
</ref>
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. It is estimated that nearly 30% of the population have malocclusions that are categorised as severe and definitely benefit from orthodontic treatment.<ref>{{cite book| last1=Borzabadi-Farahani |first1=A | editor-last1=Naretto |editor-first1=Silvano  | title=Principles in Contemporary Orthodontics | publisher=IntechOpen Limited |date=2011 |pages=215–236 | chapter=An Overview of Selected Orthodontic Treatment Need Indices | doi=10.5772/19735|isbn=978-953-307-687-4 }}</ref>

== Causes ==
The aetiology of malocclusion is somewhat contentious, however, simply put it is multifactorial, with influences being both genetic<ref>{{Cite web|date=2018-11-25|title=How genetics can affect your teeth|url=https://orthodonticsaustralia.org.au/genetics-and-your-teeth/|access-date=2020-11-16|website=Orthodontics Australia|language=en-AU}}</ref>{{Unreliable source?|date=June 2023}} and environmental.<ref>{{cite journal | vauthors = Corruccini RS, Potter RH | title = Genetic analysis of occlusal variation in twins | journal = American Journal of Orthodontics | volume = 78 | issue = 2 | pages = 140–54 | date = August 1980 | pmid = 6931485 | doi = 10.1016/0002-9416(80)90056-1 }}</ref> Malocclusion is already present in one of the [[Skhul and Qafzeh hominins|Skhul and Qafzeh hominin fossils]] and other prehistoric human skulls.<ref>{{Cite journal|last1=Sarig|first1=Rachel|last2=Slon|first2=Viviane|last3=Abbas|first3=Janan|last4=May|first4=Hila|last5=Shpack|first5=Nir|last6=Vardimon|first6=Alexander Dan|last7=Hershkovitz|first7=Israel|date=2013-11-20|title=Malocclusion in Early Anatomically Modern Human: A Reflection on the Etiology of Modern Dental Misalignment|journal=PLOS ONE|volume=8|issue=11|pages=e80771|doi=10.1371/journal.pone.0080771|issn=1932-6203|pmc=3835570|pmid=24278319|bibcode=2013PLoSO...880771S|doi-access=free}}</ref><ref>{{Cite journal|last1=Pajević|first1=Tina|last2=Juloski|first2=Jovana|last3=Glišić|first3=Branislav|date=2019-08-29|title=Malocclusion from the prehistoric to the medieval times in Serbian population: Dentoalveolar and skeletal relationship comparisons in samples|url=https://pubmed.ncbi.nlm.nih.gov/31475289/|journal=Homo: Internationale Zeitschrift für die vergleichende Forschung am Menschen|volume=70|issue=1|pages=31–43|doi=10.1127/homo/2019/1009|issn=1618-1301|pmid=31475289|s2cid=201203069}}</ref> 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]]<ref>{{cite journal | vauthors = Moimaz SA, Garbin AJ, Lima AM, Lolli LF, Saliba O, Garbin CA | title = Longitudinal study of habits leading to malocclusion development in childhood | journal = BMC Oral Health | volume = 14 | issue = 1 | pages = 96 | date = August 2014 | pmid = 25091288 | pmc = 4126276 | doi = 10.1186/1472-6831-14-96 | doi-access = free }}</ref>
* 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.<ref>{{cite journal|vauthors=Klein ET|year=1952|title=Pressure Habits, Etiological Factors in Malocclusion|journal=Am. J. Orthod.|volume=38|issue=8|pages=569–587|doi=10.1016/0002-9416(52)90025-0}}</ref><ref>{{cite journal|last=Graber TM.|year=1963|title=The "Three m's": Muscles, Malformation and Malocclusion|journal=Am. J. Orthod.|volume=49|issue=6|pages=418–450|doi=10.1016/0002-9416(63)90167-2|hdl=2027.42/32220|s2cid=57626540 |hdl-access=free}}</ref>

=== Behavioral and dental factors ===
In the active [[skeletal]] [[human development (biology)|growth]],<ref>{{cite journal|vauthors=Björk A, Helm S|date=April 1967|title=Prediction of the age of maximum puberal growth in body height|url=http://www.angle.org/doi/pdf/10.1043/0003-3219%281967%29037%3C0134%3APOTAOM%3E2.0.CO%3B2|format=PDF|journal=The Angle Orthodontist|volume=37|issue=2|pages=134–43|pmid=4290545}}</ref> [[mouthbreathing]], finger sucking, [[thumb sucking]], pacifier sucking, [[nail biting|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.<ref>{{cite journal|vauthors=Brucker M|year=1943|title=Studies on the Incidence and Cause of Dental Defects in Children: IV. Malocclusion|url=http://jdr.sagepub.com/cgi/reprint/29/2/148.pdf|journal=J Dent Res|volume=22|issue=4|pages=315–321|doi=10.1177/00220345430220041201|s2cid=71368994}}</ref><ref name="pmid13806967">{{cite journal|vauthors=Calisti LJ, Cohen MM, Fales MH|date=1960|title=Correlation between malocclusion, oral habits, and socio-economic level of preschool children|journal=Journal of Dental Research|volume=39|issue=3|pages=450–4|doi=10.1177/00220345600390030501|pmid=13806967|s2cid=39619434}}</ref><ref name="pmid4583311">{{cite journal|vauthors=Subtelny JD, Subtelny JD|date=October 1973|title=Oral habits--studies in form, function, and therapy|journal=The Angle Orthodontist|volume=43|issue=4|pages=349–83|pmid=4583311}}</ref><ref name="pmid16637724">{{cite journal|vauthors=Aznar T, Galán AF, Marín I, Domínguez A|date=May 2006|title=Dental arch diameters and relationships to oral habits|journal=The Angle Orthodontist|volume=76|issue=3|pages=441–5|pmid=16637724}}</ref><ref name="pmid12956088">{{cite journal|vauthors=Yamaguchi H, Sueishi K|date=May 2003|title=Malocclusion associated with abnormal posture|journal=The Bulletin of Tokyo Dental College|volume=44|issue=2|pages=43–54|doi=10.2209/tdcpublication.44.43|pmid=12956088|doi-access=free}}</ref> Pacifier sucking habits are also correlated with [[otitis media]].<ref name="pmid11826228">{{cite journal|vauthors=Wellington M, Hall CB|date=February 2002|title=Pacifier as a risk factor for acute otitis media|journal=Pediatrics|volume=109|issue=2|pages=351–2; author reply 353|doi=10.1542/peds.109.2.351|pmid=11826228}}</ref><ref name="pmid18562333">{{cite journal|vauthors=Rovers MM, Numans ME, Langenbach E, Grobbee DE, Verheij TJ, Schilder AG|date=August 2008|title=Is pacifier use a risk factor for acute otitis media? A dynamic cohort study|journal=Family Practice|volume=25|issue=4|pages=233–6|doi=10.1093/fampra/cmn030|pmid=18562333|doi-access=free}}</ref> [[Dental caries]], [[periapical abscess|periapical inflammation]] and tooth loss in the [[deciduous teeth]] can alter the correct permanent [[tooth eruption|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.<ref>{{Cite book|last=Hamish|first=Thomsonm|title=Occlusion|date=1990|publisher=Wright|others=Parkins, B. J.|isbn=978-0723620754|edition=2nd|location=London|oclc=21226656|name-list-style=vanc}}</ref>
*Premature and congenital loss of missing teeth.

==Signs and symptoms==
Malocclusion is a common finding,<ref>{{cite journal | vauthors = Thilander B, Pena L, Infante C, Parada SS, de Mayorga C | title = Prevalence of malocclusion and orthodontic treatment need in children and adolescents in Bogota, Colombia. An epidemiological study related to different stages of dental development | journal = European Journal of Orthodontics | volume = 23 | issue = 2 | pages = 153–67 | date = April 2001 | pmid = 11398553 | doi = 10.1093/ejo/23.2.153 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Borzabadi-Farahani A, Borzabadi-Farahani A, Eslamipour F | title = Malocclusion and occlusal traits in an urban Iranian population. An epidemiological study of 11- to 14-year-old children | journal = European Journal of Orthodontics | volume = 31 | issue = 5 | pages = 477–84 | date = October 2009 | pmid = 19477970 | doi = 10.1093/ejo/cjp031 | doi-access = free }}</ref> although it is not usually serious enough to require treatment. Those who have more severe malocclusions, which present as a part of [[Craniofacial abnormality|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.<ref>{{Cite web|date=2017-09-27|title=5 reasons you should see an orthodontist|url=https://orthodonticsaustralia.org.au/5-reasons-to-see-orthodontist/|access-date=2020-08-18|website=Orthodontics Australia|language=en-AU}}</ref> The symptoms which arise as a result of malocclusion derive from a deficiency in one or more of these categories.<ref name=":2">{{cite journal| vauthors = Oliver RG |date= December 2001 |title=An Introduction to Orthodontics, 2nd edn|journal=Journal of Orthodontics|volume=28|issue=4|pages=320|doi=10.1093/ortho/28.4.320 }}</ref>

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.{{Citation needed|date=December 2018}}

==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.<ref name="Millett_2018">{{cite journal | vauthors = Millett DT, Cunningham SJ, O'Brien KD, Benson PE, de Oliveira CM | title = Orthodontic treatment for deep bite and retroclined upper front teeth in children | journal = The Cochrane Database of Systematic Reviews | volume = 2 | pages = CD005972 | date = February 2018 | issue = 3 | pmid = 29390172 | pmc = 6491166 | doi = 10.1002/14651858.cd005972.pub4 }}</ref> It has been found to occur in 15–20% of the US population.<ref>{{cite journal | vauthors = Brunelle JA, Bhat M, Lipton JA | title = Prevalence and distribution of selected occlusal characteristics in the US population, 1988-1991 | journal = Journal of Dental Research | volume = 75 Spec No | issue = 2 Suppl | pages = 706–13 | date = February 1996 | pmid = 8594094 | doi = 10.1177/002203459607502S10 | s2cid = 30447284 }}</ref>

An open bite is a condition characterised by a complete lack of overlap and occlusion between the upper and lower incisors.<ref>{{cite journal | vauthors = de Castilho LS, Abreu MH, Pires e Souza LG, Romualdo LT, Souza e Silva ME, Resende VL | title = Factors associated with anterior open bite in children with developmental disabilities | journal = Special Care in Dentistry | volume = 38 | issue = 1 | pages = 46–50 | date = January 2018 | pmid = 29278267 | doi = 10.1111/scd.12262 | s2cid = 42747680 }}</ref> In children, open bite can be caused by prolonged thumb sucking.<ref name=":3">{{cite journal | vauthors = Feres MF, Abreu LG, Insabralde NM, Almeida MR, Flores-Mir C | title = Effectiveness of the open bite treatment in growing children and adolescents. A systematic review | journal = European Journal of Orthodontics | volume = 38 | issue = 3 | pages = 237–50 | date = June 2016 | pmid = 26136439 | pmc = 4914905 | doi = 10.1093/ejo/cjv048 }}</ref> Patients often present with impaired speech and mastication.<ref name=":4">{{cite journal | vauthors = Cambiano AO, Janson G, Lorenzoni DC, Garib DG, Dávalos DT | title = Nonsurgical treatment and stability of an adult with a severe anterior open-bite malocclusion | journal = Journal of Orthodontic Science | volume = 7 | pages = 2 | date = 2018 | pmid = 29765914 | pmc = 5952238 | doi = 10.4103/jos.JOS_69_17 | doi-access = free }}</ref>

=== 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’.<ref name=":2" /><ref name=":5">{{Cite journal|last=Houston|first=W. J. B.|date=1992-02-01|title=Book Reviews|journal=The European Journal of Orthodontics|volume=14|issue=1|pages=69|doi=10.1093/ejo/14.1.69 }}</ref><ref>{{cite journal | vauthors = Hamdan AM, Lewis SM, Kelleher KE, Elhady SN, Lindauer SJ | title = Does overbite reduction affect smile esthetics? | journal = The Angle Orthodontist | volume = 89 | issue = 6 | pages = 847–854 | date = November 2019 | pmid = 31306077 | doi = 10.2319/030819-177.1 | pmc = 8109173 | doi-access = free }}</ref>

===Angle's classification method===

{{Technical|section|date=September 2023}}

[[File:Class1type2.jpg|thumb|200px|right|Class I with severe crowding and [[Commonly used terms of relationship and comparison in dentistry|labially]] erupted [[Canine tooth|canines]]]]
[[File:Class II.jpg|thumb|200px|right|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]].<ref>{{cite web |url=http://www.unc.edu/depts/appl_sci/ortho/introduction/angles.html |title=Angle's Classification of Malocclusion |access-date=2007-10-31 |archive-url=https://web.archive.org/web/20080213164657/http://www.unc.edu/depts/appl_sci/ortho/introduction/angles.html|archive-date=2008-02-13}}</ref> According to Angle, the [[Commonly used terms of relationship and comparison in dentistry|mesiobuccal cusp]] of the upper first molar should align with the [[Commonly used terms of relationship and comparison in dentistry|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-dimensional|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.<ref>Sunil Kumar (Ed.): Orthodontics. New Delhi 2008, 624 p., {{ISBN|978-81-312-1054-3}}, p. 127</ref> Thus, many attempts have been made to modify the Angle system or to replace it completely with a more efficient one,<ref>Sunil Kumar (Ed.): Orthodontics. New Delhi 2008, p. 123. A list of 18 approaches to modify or replace Angle's system is given here with further references at the end of the book.</ref> but Angle's classification continues be popular mainly because of its simplicity and clarity.{{Citation needed|date=December 2018}}

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).<ref>Gurkeerat Singh: Textbook of Orthodontics, p. 163-170, with further references on p. 174.</ref>

===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:<ref name=":2" />

*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.<ref name="Millett_2018" /> 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.<ref name="Millett_2018" />

Lack of masticatory stress during development can cause tooth overcrowding.<ref name=":6">{{cite journal |last1=Lieberman |first1=D |title=Effects of food processing on masticatory strain and craniofacial growth in a retrognathic face |journal=Journal of Human Evolution |date=May 2004 |volume=46 |issue=6 |pages=655–77 |doi=10.1016/s0047-2484(04)00051-x |pmid=15183669 }}</ref><ref name=":7">{{cite journal | vauthors = Ingervall B, Bitsanis E | title = A pilot study of the effect of masticatory muscle training on facial growth in long-face children | journal = European Journal of Orthodontics | volume = 9 | issue = 1 | pages = 15–23 | date = February 1987 | pmid = 3470182 | doi = 10.1093/ejo/9.1.15 | url = https://boris.unibe.ch/115382/1/9-1-15.pdf }}</ref> Children who chewed a hard resinous gum for two hours a day showed increased facial growth.<ref name=":6" /> 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 animals fed softer food had significantly narrower and shorter faces and thinner and shorter mandibles than animals fed hard food.<ref name=":6" /><ref name="nlm">{{cite web|url=https://www.nlm.nih.gov/medlineplus/ency/article/001058.htm|title=Malocclusion of teeth|last1=Rosenberg|first1=Jack|date=2010-02-22|website=Medline Plus|access-date=2012-02-06|name-list-style=vanc}}</ref>{{Verification failed|date=June 2023}}

A 2016 review found that breastfeeding lowers the incidence of malocclusions developing later on in developing infants.<ref>Victora CG, Bahl R, Barros AJ, França GV, Horton S, Krasevec J, Murch S, Sankar MJ, Walker N, Rollins NC (January 2016). "Breastfeeding in the 21st century: epidemiology, mechanisms, and lifelong effect". Lancet. 387 (10017): 475–90. doi:10.1016/s0140-6736(15)01024-7. {{PMID|26869575}}.</ref>

During the transition to agriculture, the shape of the human mandible went through a series of changes. The mandible underwent a complex shape changes not matched by the teeth, leading to incongruity between the dental and mandibular form. These changes in human skulls may have been "driven by the decreasing bite forces required to chew the [[processed food]]s eaten once humans switched to growing different types of cereals, milking and herding animals about 10,000 years ago."<ref name=":7" /><ref>{{cite journal | vauthors = Quaglio CL, de Freitas KM, de Freitas MR, Janson G, Henriques JF | title = Stability and relapse of maxillary anterior crowding treatment in class I and class II Division 1 malocclusions | journal = American Journal of Orthodontics and Dentofacial Orthopedics | volume = 139 | issue = 6 | pages = 768–74 | date = June 2011 | pmid = 21640883 | doi = 10.1016/j.ajodo.2009.10.044 }}</ref>

===Treatment===
Orthodontic management of the condition includes dental braces, lingual braces, clear aligners or palatal expanders.<ref name=":16" /> Other treatments include the removal of one or more teeth and the repair of injured teeth. In some cases, surgery may be necessary.<ref>{{Cite web|title=Malocclusion of teeth: MedlinePlus Medical Encyclopedia|url=https://medlineplus.gov/ency/article/001058.htm|access-date=2021-04-07|website=medlineplus.gov|language=en}}</ref>

==Treatment==
Malocclusion is often treated with orthodontics,<ref name=":16">{{Cite web|date=2020-06-29|title=Dental Crowding: Causes and Treatment Options|url=https://orthodonticsaustralia.org.au/dental-crowding-causes-and-treatment-options/|access-date=2020-11-19|website=Orthodontics Australia|language=en-AU}}</ref> such as tooth extraction, clear aligners, or dental braces,<ref>{{Cite web|date=2021-07-01|title=Can Buck Teeth Be Fixed? Causes & Treatment Options|url=https://orthodonticsaustralia.org.au/can-buck-teeth-be-fixed/|access-date=2021-10-11|website=Orthodontics Australia|language=en-AU}}</ref> followed by growth modification in children or jaw surgery (orthognathic surgery) in adults. Surgical intervention is used only in rare occasions. This may include surgical reshaping to lengthen or shorten the jaw. Wires, plates, or screws may be used to secure the jaw bone, in a manner like the surgical stabilization of jaw fractures. Very few people have "perfect" alignment of their teeth with most problems being minor that do not require treatment.<ref name=":6" />

=== Crowding ===
Crowding of the teeth is treated with [[orthodontics]], often with [[tooth extraction]], [[clear aligners]], or [[dental braces]], followed by growth modification in children or jaw surgery ([[orthognathic surgery]]) in adults. Surgery may be required on rare occasions. This may include surgical reshaping to lengthen or shorten the jaw (orthognathic surgery). Wires, plates, or screws may be used to secure the jaw bone, in a manner similar to the surgical stabilization of jaw fractures. Very few people have "perfect" alignment of their teeth. However, most problems are very minor and do not require treatment.<ref name="nlm" />

=== Class I ===
While treatment is not crucial in class I malocclusions, in severe cases of crowding can be an indication for intervention. Studies indicate that tooth extraction can have benefits to correcting malocclusion in individuals.<ref name=":8">{{Cite journal|last=Alam|first=MK|date=October 2018|title=Treatment of Angle Class I malocclusion with severe crowding by extraction of four premolars: a case report|journal=Bangladesh Journal of Medical Science|volume=17|issue=4|pages=683–687|doi=10.3329/bjms.v17i4.38339|doi-access=free}}</ref><ref>{{cite journal | vauthors = Persson M, Persson EC, Skagius S | title = Long-term spontaneous changes following removal of all first premolars in Class I cases with crowding | journal = European Journal of Orthodontics | volume = 11 | issue = 3 | pages = 271–82 | date = August 1989 | pmid = 2792216 | doi = 10.1093/oxfordjournals.ejo.a035995 }}</ref> Further research is needed as reoccurring crowding has been examined in other clinical trials.<ref name=":8" /><ref>{{cite journal | vauthors = von Cramon-Taubadel N | title = Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 49 | pages = 19546–51 | date = December 2011 | pmid = 22106280 | pmc = 3241821 | doi = 10.1073/pnas.1113050108 | bibcode = 2011PNAS..10819546V | doi-access = free }}</ref>

=== Class II ===
A few treatment options for class II malocclusions include:

# Functional appliance which maintains the mandible in a postured position to influence both the orofacial musculature and dentoalveolar development prior to fixed appliance therapy. This is ideally done through pubertal growth in pre-adolescent children and the fixed appliance during permanent dentition.<ref>{{cite journal | vauthors = Nayak KU, Goyal V, Malviya N | title = Two-phase treatment of class II malocclusion in young growing patient | journal = Contemporary Clinical Dentistry | volume = 2 | issue = 4 | pages = 376–80 | date = October 2011 | pmid = 22346172 | pmc = 3276872 | doi = 10.4103/0976-237X.91808 | doi-access = free }}</ref> Different types of removable appliances include Activator, Bionatar, Medium opening activator, Herbst, Frankel and twin block appliance with the twin block being the most widely used one.<ref>{{cite web |title=Treatment of class ii malocclusions |url=https://www.slideshare.net/seepmaano/treatment-of-class-ii-malocclusions|date=2013-11-14}}</ref>
# Growth modification through headgear to redirect maxillary growth
# Orthodontic camouflage so that jaw discrepancy no longer apparent
# Orthognathic surgery – sagittal split osteotomy mandibular advancement carried out when growth is complete where skeletal discrepancy is severe in anterior-posterior relationship or in vertical direction. Fixed appliance is required before, during and after surgery.
# Upper Removable Appliance – limited role in contemporary treatment of increased overjets. Mostly used for very mild Class II, overjet due to incisor proclination, favourable overbite.

==== Class II Division 1 ====
Low- to moderate- quality evidence suggests that providing early orthodontic treatment for children with prominent upper front teeth (class II division 1) is more effective for reducing the incidence of incisal trauma than providing one course of orthodontic treatment in adolescence.<ref name=":9">{{cite journal | vauthors = Pinhasi R, Eshed V, von Cramon-Taubadel N | title = Incongruity between affinity patterns based on mandibular and lower dental dimensions following the transition to agriculture in the Near East, Anatolia and Europe | journal = PLOS ONE | volume = 10 | issue = 2 | pages = e0117301 | date = 2015-02-04 | pmid = 25651540 | pmc = 4317182 | doi = 10.1371/journal.pone.0117301 | bibcode = 2015PLoSO..1017301P | doi-access = free }}</ref> There do not appear to be any other advantages of providing early treatment when compared to late treatment.<ref name=":9" /> Low-quality evidence suggests that, compared to no treatment, late treatment in adolescence with functional appliances is effective for reducing the prominence of upper front teeth.<ref name=":9" />

==== Class II Division 2 ====
Treatment can be undertaken using orthodontic treatments using dental braces.<ref name=":0">{{cite journal | vauthors = Batista KB, Thiruvenkatachari B, Harrison JE, O'Brien KD | title = Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children and adolescents | journal = The Cochrane Database of Systematic Reviews | volume = 2018 | pages = CD003452 | date = March 2018 | issue = 3 | pmid = 29534303 | pmc = 6494411 | doi = 10.1002/14651858.cd003452.pub4 }}</ref> While treatment is carried out, there is no evidence from clinical trials to recommend or discourage any type of orthodontic treatment in children.<ref name=":0" /> A 2018 Cochrane systematic review anticipated that the evidence base supporting treatment approaches is not likely to improve occlusion due to the low prevalence of the condition and the ethical difficulties in recruiting people to participate in a randomized controlled trials for treating this condition.<ref name=":0" />

=== Class III ===
The British Standard Institute (BSI) classify class III incisor relationship as the lower incisor edge lies anterior to the cingulum plateau of the upper incisors, with reduced or reversed over jet.<ref>{{Cite journal|last1=CLASSIFICATION OF SKELETAL AND DENTAL MALOCCLUSION: REVISITED|last2=Mageet|first2=Adil Osman|title=Classification of Skeletal and Dental Malocclusion: Revisited|journal=Stomatology Edu Journal|date=2016|volume=3|issue=2|pages=205–211|doi=10.25241/2016.3(2).11|doi-access=free}}</ref> The skeletal facial deformity is characterized by mandibular prognathism, maxillary retrognathism or a combination of the two. This effects 3-8% of UK population with a higher incidence seen in Asia.<ref>{{Cite book|title=Esthetics and biomechanics in orthodontics|date=2014-04-10|others=Nanda, Ravindra,, Preceded by (work): Nanda, Ravindra.|isbn=978-0-323-22659-2|edition=Second|location=St. Louis, Missouri|oclc=880707123}}</ref>

One of the main reasons for correcting Class III malocclusion is aesthetics and function. This can have a psychological impact on the person with malocclusion resulting in speech and mastication problems as well. In mild class III cases, the patient is quite accepting of the aesthetics and the situation is monitored to observe the progression of skeletal growth.<ref>{{cite journal | vauthors = Eslami S, Faber J, Fateh A, Sheikholaemmeh F, Grassia V, Jamilian A | title = Treatment decision in adult patients with class III malocclusion: surgery versus orthodontics | journal = Progress in Orthodontics | volume = 19 | issue = 1 | pages = 28 | date = August 2018 | pmid = 30069814 | pmc = 6070451 | doi = 10.1186/s40510-018-0218-0 | doi-access = free }}</ref>

Maxillary and mandibular skeletal changes during prepubertal, pubertal and post pubertal stages show that class III malocclusion is established before the prepubertal stage.<ref name=":10">{{cite journal | vauthors = Uner O, Yüksel S, Uçüncü N | title = Long-term evaluation after chincap treatment | journal = European Journal of Orthodontics | volume = 17 | issue = 2 | pages = 135–41 | date = April 1995 | pmid = 7781722 | doi = 10.1093/ejo/17.2.135 }}</ref> One treatment option is the use of growth modification appliances such as the Chin Cap which has greatly improved the skeletal framework in the initial stages. However, majority of cases are shown to relapse into inherited class III malocclusion during the pubertal growth stage and when the appliance is removed after treatment.<ref name=":10" />

Another approach is to carry out orthognathic surgery, such as a bilateral sagittal split osteotomy (BSSO) which is indicated by horizontal mandibular excess. This involves surgically cutting through the mandible and moving the fragment forward or backwards for desired function and is supplemented with pre and post surgical orthodontics to ensure correct tooth relationship. Although the most common surgery of the mandible, it comes with several complications including: bleeding from inferior alveolar artery, unfavorable splits, condylar resorption, avascular necrosis and worsening of temporomandibular joint.<ref>{{cite journal | vauthors = Ravi MS, Shetty NK, Prasad RB | title = Orthodontics-surgical combination therapy for Class III skeletal malocclusion | journal = Contemporary Clinical Dentistry | volume = 3 | issue = 1 | pages = 78–82 | date = January 2012 | pmid = 22557903 | pmc = 3341765 | doi = 10.4103/0976-237X.94552 | doi-access = free }}</ref>

Orthodontic camouflage can also be used in patients with mild skeletal discrepancies. This is a less invasive approach that uses orthodontic brackets to correct malocclusion and try to hide the skeletal discrepancy. Due to limitations of orthodontics, this option is more viable for patients who are not as concerned about the aesthetics of their facial appearance and are happy to address the malocclusion only, as well as avoiding the risks which come with orthognathic surgery. Cephalometric data can aid in the differentiation between the cases that benefit from ortho-surgical or orthodontic treatment only (camouflage); for instance, examining a large group of orthognathic patient with Class III malocclusions they had average ANB angle of -3.57° (95% CI, -3.92° to -3.21°).  <ref>{{cite journal | vauthors = Borzabadi Farahani A, Olkun HK, Eslamian L,Eslamipour F | title = A retrospective investigation of orthognathic patients and functional needs. | language = en | journal = Australasian Orthodontic Journal | volume = 40| pages = 111–120 | date = 2024 | doi = 10.2478/aoj-2024-0013  | doi-access = free }}</ref>

=== Deep bite ===
The most common corrective treatments available are fixed or removal appliances (such as dental braces), which may or may not require surgical intervention. At this time there is no robust evidence that treatment will be successful.<ref name=":0" />

=== Open bite ===
An open bite malocclusion is when the upper teeth don't overlap the lower teeth. When this malocclusion occurs at the front teeth it is known as anterior open bite. An open bite is difficult to treat due to multifactorial causes, with relapse being a major concern. This is particularly so for an anterior open bite.<ref name=":1">{{cite journal | vauthors = Atsawasuwan P, Hohlt W, Evans CA | title = Nonsurgical approach to Class I open-bite malocclusion with extrusion mechanics: a 3-year retention case report | journal = American Journal of Orthodontics and Dentofacial Orthopedics | volume = 147 | issue = 4 | pages = 499–508 | date = April 2015 | pmid = 25836010 | doi = 10.1016/j.ajodo.2014.04.024 }}</ref> Therefore, it is important to carry out a thorough initial assessment in order to obtain a diagnosis to tailor a suitable treatment plan.<ref name=":1" /> It is important to take into consideration any habitual risk factors, as this is crucial for a successful outcome without relapse. Treatment approach includes behavior changes, appliances and surgery. Treatment for adults include a combination of extractions, fixed appliances, intermaxillary elastics and orthognathic surgery.<ref name=":4" /> For children, orthodontics is usually used to compensate for continued growth. With children with mixed dentition, the malocclusion may resolve on its own as the permanent teeth erupt. Furthermore, should the malocclusion be caused by childhood habits such as digit, thumb or pacifier sucking, it may result in resolution as the habit is stopped. Habit deterrent appliances may be used to help in breaking digit and thumb sucking habits. Other treatment options for patients who are still growing include functional appliances and headgear appliances.

== Tooth size discrepancy ==
Identifying the presence of tooth size discrepancies between the maxillary and mandibular arches is an important component of correct orthodontic diagnosis and treatment planning.

To establish appropriate alignment and occlusion, the size of upper and lower front teeth, or upper and lower teeth in general, needs to be proportional. Inter-arch tooth size discrepancy (ITSD) is defined as a disproportion in the mesio-distal dimensions of teeth of opposing dental arches. The prevalence is clinically significant among orthodontic patients and has been reported to range from 17% to 30%.<ref name=":11">{{cite journal | vauthors = Grauer D, Heymann GC, Swift EJ | title = Clinical management of tooth size discrepancies | journal = Journal of Esthetic and Restorative Dentistry | volume = 24 | issue = 3 | pages = 155–9 | date = June 2012 | pmid = 22691075 | doi = 10.1111/j.1708-8240.2012.00520.x | s2cid = 11482185 }}</ref>

Identifying inter-arch tooth size discrepancy (ITSD) before treatment begins allows the practitioner to develop the treatment plan in a way that will take ITSD into account. ITSD corrective treatment may entail demanding reduction (interproximal wear), increase (crowns and resins), or elimination (extractions) of dental mass prior to treatment finalization.<ref name=":12">{{cite journal | vauthors = Cançado RH, Gonçalves Júnior W, Valarelli FP, Freitas KM, Crêspo JA | title = Association between Bolton discrepancy and Angle malocclusions | journal = Brazilian Oral Research | volume = 29 | pages = 1–6 | date = 2015 | pmid = 26486769 | doi = 10.1590/1807-3107BOR-2015.vol29.0116 | doi-access = free }}</ref>

Several methods have been used to determine ITSD. Of these methods the one most commonly used is the Bolton analysis. Bolton developed a method to calculate the ratio between the mesiodistal width of maxillary and mandibular teeth and stated that a correct and harmonious occlusion is possible only with adequate proportionality of tooth sizes.<ref name=":12" /> Bolton's formula concludes that if in the anterior portion the ratio is less than 77.2% the lower teeth are too narrow, the upper teeth are too wide or there is a combination of both. If the ratio is higher than 77.2% either the lower teeth are too wide, the upper teeth are too narrow or there is a combination of both.<ref name=":11" />

==Other conditions==
{{Further|Open bite malocclusion}}

[[File:Treat open bite.jpg|thumb|upright=1.35|Open bite treatment after eight months of braces.]]
Other kinds of malocclusions can be due to or horizontal, vertical, or transverse skeletal discrepancies, including skeletal asymmetries.

Increased vertical growth causes a long facial profile and commonly leads to an [[open bite malocclusion]], while decreased vertical facial growth causes a short facial profile and is commonly associated with a deep bite malocclusion. However, there are many other more common causes for open bites (such as tongue thrusting and thumb sucking) and likewise for deep bites.<ref name=":13">{{cite journal | vauthors = Harrington C, Gallagher JR, Borzabadi-Farahani A | title = A retrospective analysis of dentofacial deformities and orthognathic surgeries using the index of orthognathic functional treatment need (IOFTN) | journal = International Journal of Pediatric Otorhinolaryngology | volume = 79 | issue = 7 | pages = 1063–6 | date = July 2015 | pmid = 25957779 | doi = 10.1016/j.ijporl.2015.04.027 }}</ref><ref name=":14">{{cite book|last1=Posnick|first1=Jeffrey C.|title=Orthognatic Surgery: Principles and Practice|title-link=Orthognatic Surgery: Principles and Practice|date=September 2013|publisher=[[Elsevier]]|isbn=978-145572698-1|location=Amsterdam|pages=61–68|chapter=Definition and Prevalence of Dentofacial Deformities|doi=10.1016/B978-1-4557-2698-1.00003-4|name-list-style=vanc}}</ref><ref name=":15">{{cite journal | vauthors = Borzabadi-Farahani A, Eslamipour F, Shahmoradi M | title = Functional needs of subjects with dentofacial deformities: A study using the index of orthognathic functional treatment need (IOFTN) | journal = Journal of Plastic, Reconstructive & Aesthetic Surgery | volume = 69 | issue = 6 | pages = 796–801 | date = June 2016 | pmid = 27068664 | doi = 10.1016/j.bjps.2016.03.008 }}</ref>

The upper or lower jaw can be overgrown (macrognathia) or undergrown (micrognathia).<ref name=":14" /><ref name=":13" /><ref name=":15" /> It has been reported that patients with micrognathia are also affected by retrognathia (abnormal posterior positioning of the mandible or maxilla relative to the facial structure).<ref name=":14" />  These patients are majorly predisposed to a class II malocclusion. Mandibular macrognathia results in prognathism and predisposes patients to a class III malocclusion.<ref>{{Cite book|last=Purkait|first=S|title=Essentials of Oral Pathology 4th Edition|year=2011}}</ref>

Most malocclusion studies to date have focused on Class III malocclusions. Genetic studies for Class II and Class I malocclusion are more rare. An example of hereditary mandibular prognathism can be seen amongst the Hapsburg Royal family where one third of the affected individuals with severe class III malocclusion had one parent with a similar phenotype <ref>{{cite journal | vauthors = Joshi N, Hamdan AM, Fakhouri WD | title = Skeletal malocclusion: a developmental disorder with a life-long morbidity | journal = Journal of Clinical Medicine Research | volume = 6 | issue = 6 | pages = 399–408 | date = December 2014 | pmid = 25247012 | pmc = 4169080 | doi = 10.14740/jocmr1905w }}</ref>

The frequent presentation of dental malocclusions in patients with craniofacial birth defects also supports a strong genetic aetiology. About 150 genes are associated with craniofacial conditions presenting with malocclusions.<ref>{{cite journal | vauthors = Moreno Uribe LM, Miller SF | title = Genetics of the dentofacial variation in human malocclusion | journal = Orthodontics & Craniofacial Research | volume = 18 Suppl 1 | issue = S1 | pages = 91–9 | date = April 2015 | pmid = 25865537 | pmc = 4418210 | doi = 10.1111/ocr.12083 }}</ref>  Micrognathia is a commonly recurring craniofacial birth defect appearing among multiple syndromes.

For patients with severe malocclusions, corrective jaw surgery or [[orthognathic surgery]] may be carried out as a part of overall treatment, which can be seen in about 5% of the general population.<ref name=":14" /><ref name=":13" /><ref name=":15" />

== See also ==
* [[Crossbite]]
* [[Elastics (orthodontics)|Elastics]]
*[[Facemask (orthodontics)]]
* [[Maximum intercuspation]]
*[[Mouth breathing]]
* [[Occlusion (dentistry)]]

== References ==
{{Reflist}}

==Further reading==
* [[Peter S. Ungar]], "The Trouble with Teeth: Our teeth are crowded, crooked and riddled with cavities. It hasn't always been this way", ''[[Scientific American]]'', vol. 322, no. 4 (April 2020), pp.&nbsp;44–49. "Our teeth [...] evolved over hundreds of millions of years to be incredibly strong and to align precisely for efficient chewing. [...] Our dental disorders largely stem from a shift in the oral environment caused by the introduction of softer, more sugary foods than the ones our ancestors typically ate."

== External links ==
{{Medical resources
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{{Commons category|Malocclusion}}

{{Orthodontology}}
{{Dentofacial anomalies and jaw disease}}

[[Category:Jaw disorders]]
[[Category:Teeth]]