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

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

The local factors responsible for malocclusion:-

• 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

• Delayed eruption of permanent teeth

• Abnormal eruptive path• Ankylosis• Dental caries• Improper dental restorations

• Anomalies in number of teeth:- supernumerary teeth:- Teeth that are

extra to the normal complement are termed supernumerary teeth. These are having abnormal morphology.

A frequently seen supernumerary tooth is mesiodens which occurs in maxillary midline

Missing teeth:- most commonly missing teeth are-third molars, maxillary lateral incisors, mandibular 2nd premolars, mandibular incisors, maxillary 2nd premolars.

Absence of teeth cause spacing in the arch and causes mesial migration of distal tooth.

• Anomalies of tooth size:- In order to have normal occlusion

there should be harmony between tooth size & arch length & also between tooth present between in each arches.

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

• Anomalies of tooth shape:- -presence of peg shaped lateral

incisors -presence of abnormally large

cingulum on a maxillary incisors. -mandibular 2nd premolar may rarely

have an additional lingual cusp. -congenital syphilis may be associated

with abnormal tooth form;peg shaped laterals and mulberry molars.

-dilaceration, fusion, gemination.

• Abnormal labial frenum:- abnormalities of maxillary labial

frenum are quite often associated with a maxillary midline spacing.

• Prolonged retention of deciduous teeth

- undue retention of deciduous teeth beyond the usual eruption age of

their permanent successors. - it results in lingual or labial/buccal

eruption of permanent teeth.Reasons for delayed retention of

deciduous teeth is :- Absence of underlying permanent teeth,endocrinal disturbances, non vital deciduous teeth

that do not resorb.

• Delayed eruption of permanent teeth Reasons that causes delayed eruption

of permanent teeth are; congenital absence of teeth, presence

of supernumerary tooth in the path of permanent teeth, presence of heavy mucosal barrier, endocrinal disturbances and presence of non vital deciduous teeth that are not resorb.

• Abnormal eruptive path one of the cause of malocclusion is an

abnormal eruptive path of eruption which could be due to arch length deficiency, presence of supernumerary teeth retained root fragments or formation of bony barrier.

• Ankylosis:- Is a condition wherein a part or whole of the root surace is directly fused to the bone with absence of intervening periodontal membrane.

• Dental caries:- proximal caries that not restored causes mesial migration of distal teeth and lead into decrease in arch length.

• Improper dental restoration:-Over contoured occlusal restoration

may lead to premature contacts leading to functional shift of mandible during jaw closure.

Under contoured may cause eruption of antagonist tooth