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Etiology of Malocclusion:Etiology of Malocclusion:--Local FactorsLocal FactorsEtiology of Malocclusion:Etiology of Malocclusion:--Local FactorsLocal Factors

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The local factors responsible formalocclusion:-

Anomalies in number of teeth

- supernumerary teeth

-missing teeth Anomalies of tooth size

Anomalies of tooth shape

Abnormal labial frenum Premature loss of deciduous teeth

Prolonged retention of deciduous

teeth

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Delayed eruption of permanent teeth

Abnormal eruptive path Ankylosis

Dental caries

Improper dental restorations

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Anomalies in number of teeth:-

supernumerary teeth:- Teeth that areextra to the normal complement aretermed supernumerary teeth.These arehaving abnormal morphology.

A frequently seen supernumerary tooth ismesiodens which occurs in maxillarymidline

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Missing teeth:- most commonly missingteeth are-third molars, maxillarylateral incisors, mandibular 2nd

premolars, mandibular incisors,maxillary 2nd premolars.

Absence of teeth cause spacing in the

arch and causes mesial migration ofdistal tooth.

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Anomalies of tooth size:-

In order to have normal occlusion thereshould beharmony between tooth size& arch length & also between toothpresent between in each arches.

An increase in tooth size causes crowdingin the arch & decrease in teeth sizecauses spacing in the arch

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Anomalies of tooth shape:-

-presence of peg shaped lateral incisors-presence of abnormally large cingulumon a maxillary incisors.

-mandibular 2nd premolar may rarelyhave an additional lingual cusp.

-congenital syphilis may be associatedwith abnormal tooth form;peg shaped

laterals and mulberry molars.-dilaceration, fusion, gemination.

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Abnormal labial frenum:-

abnormalities of maxillary labial frenumarequite often associated with amaxillary midline spacing.

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Prolonged retention of deciduous teeth

- undue retention of deciduous teeth

beyond the usual eruption age of theirpermanent successors.

- it results in lingual or labial/buccaleruption of permanent teeth.

Reasons for delayed retention ofdeciduous teeth is :- Absence of

underlying permanent teeth,endocrinaldisturbances, non vital deciduous teeth

that do not resorb.

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Delayed eruption of permanent teeth

Reasons that causes delayed eruption ofpermanent teeth are;

congenital absence of teeth, presence ofsupernumerary tooth in the path of

permanent teeth, presence of heavymucosal barrier, endocrinal disturbancesand presence of non vital deciduous teeth

that are not resorb.

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Abnormal eruptive path

one of the cause of malocclusion is anabnormal eruptive path of eruptionwhich could be due to arch lengthdeficiency, presence of supernumerary

teeth retained root fragments orformation of bony barrier.

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Ankylosis:- Is a condition wherein apart or whole of the root surace isdirectly fused to the bone withabsence of intervening periodontalmembrane.

Dental caries:- proximal caries thatnot restored causes mesial migration

of distal teeth and lead into decreasein arch length.

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Improper dental restoration:-

Over contour

ed occlusal r

estoration maylead to premature contacts leading to

functional shift of mandible during jawclosure.

Under contoured may causeeruption ofantagonist tooth