Etiology of Malocclusion PDF

Etiology of malocclusion General Local factors factors  Hereditary Congenital Environmental General Predisposing metabolic climate and disease factors Dietary problems (nutritional deficiency)...

Etiology of malocclusion General Local factors factors  Hereditary Congenital Environmental General Predisposing metabolic climate and disease factors Dietary problems (nutritional deficiency) Abnormal pressure habits and function ectodermal dysplasia  Thumb and finger sucking Tongue thrust Lip and nail biting Abnormal Abnormal swallowing habits (improper deglutition) pressure Speech defects habits Respiratory abnormalities, like and mouth breathing, Tonsils and adenoids function Posture Trauma and accidents.  Local factors Anomalies of number Anomalies of tooth size Anomalies of tooth shape Premature loss of deciduous teeth Prolonged retention of deciduous teeth Delayed eruption of permanent teeth Abnormal labial frenum Dental caries Improper dental restorations Ankylosis Abnormal eruptive path. Orthodontic tooth movements Pure translation Pure rotation Combined rotation and translation  Intrusion Pure Extrusion translation Bodily movement of tooth  Around the long axis of the tooth is called rotation. Pure Rotation Around a facio-lingual axis is called tipping. Around a mesiodistal axis is called torque.  Tipping Combined Bodily movement Rotation and Torque Translation Intrusion Extrusion. Rotation  Tipping is perhaps the simplest type of tooth movement and the one most readily carried out. Tipping A single force applied at one movement point of the crown of a tooth causes the crown to move in the direction of the force and the root in the opposite direction.  The term ‘torque’ in orthodontics refers to the differential movement of one part of a tooth, while physically Torque restraining any movement of the movement other parts. The term is often applied to movement of root without the movement of crown.  Intrusion of the tooth involves resorption of bone, particularly around the apex of the tooth. Intrusion In this movement, the whole of supporting structures are under pressure with virtually no areas of tension  Extrusion of the teeth from its socket can be achieved without much resorption of Extrusion bone, bone deposition being required to reform the supporting mechanism of the tooth.  The movement of the tooth around its long axis is termed as rotation in orthodontics Pure rotation of a tooth in its socket requires the Rotation application of a force couple. A couple is created by applying equal and opposite forces to the different areas of the tooth