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Concept
Overjet
Summary
Overjet is the extent of horizontal (anterior-posterior) overlap of the maxillary central incisors over the mandibular central incisors. In class II (division I) malocclusion the overjet is increased as the maxillary central incisors are protruded.
Class II Division I is an incisal classification of malocclusion where the incisal edge of the mandibular incisors lie posterior to the cingulum plateau of the maxillary incisors with normal or proclined maxillary incisors (British Standards Index, 1983). There is always an associated increase in overjet.
In the Class II Division 2 incisal classification of malocclusion, the lower incisors occlude posterior to the cingulum plateau of the upper incisors and the upper central incisors are retroclined. The overjet is usually minimal but it may be increased.
Benefits associated with orthodontic treatment include a reduction in the susceptibility to caries, periodontal disease and temporomandibular joint dysfunction, whilst also improving speech and masticatory function. However, the supporting evidence is equivocal.
It may be assumed that correction of an increased overjet will potentially reduce the risk of trauma, as it has been shown that individuals with an overjet greater than are twice as likely to suffer injury to their upper incisors.
Table showing the relationship between size of overjet and prevalence of traumatised anterior teeth
{| class="wikitable"
|-
! Overjet (mm) !! Incidence (%)
|-
| 5 || 22
|-
| 9 || 24
|-
| >9 || 44
|}
The meta-analysis undertaken in a recent Cochrane review found that 'early orthodontic treatment for children with prominent upper front teeth is more effective in reducing the incidence of incisal trauma than providing one course of orthodontic treatment when the child is in early adolescence'. A number of studies have found that the presence of malocclusion can have a significant impact on an individual’s quality of life and result in reduced self-esteem.
Official source
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