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Etiology of Malocclusion II
 

Etiology of Malocclusion II

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Introduction to Orthodontics

Introduction to Orthodontics
Fifth Year

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    Etiology of Malocclusion II Etiology of Malocclusion II Presentation Transcript

    • Ninth Lecture Etiology of Malocclusion
    • General Causes 1.Evolution: 2. Congenital malformation: 3. Endocrinal disturbances: 4. Nutritional deficiency 5. Pathological Conditions: March 5, 2012 Dr. Ahmed Basyouni 2
    • Continue B. Local Causes Local Causes 1. Congenital missing teeth: 2. Supernumerary teeth: 3. Teeth of abnormal size and form: 4. Abnormal path of eruption: 5. Abnormal labial frenum: 6. Abnormal pressure habits: a. Thumb sucking: b.Tongue thrusting: c. Nail biting: d. Abnormal swallowing: e. Mouth breathing: March 5, 2012 Dr. Ahmed Basyouni 3
    • Continue B. Local Causes  Premature loss of decid. Teeth: In general, effects of premature loss of teeth depend on dentoalveolar disproportion & also on muscle environment. March 5, 2012 Dr. Ahmed Basyouni 4
    • B. Local Causes 7. Premature loss of decid. Teeth: a. Premature loss of decid. Incisors: In the maxilla, it is not followed by impaction of the permanent incisors, but will develop tongue thrust to provide anterior seal during swallowing. While in the mandible, it will result in lack of forward stimulation & crowding of permanent incisors and deep overbite. March 5, 2012 Dr. Ahmed Basyouni 5
    • B. Local Causes 7. Premature loss of decid. Teeth: b. Premature loss of decid. canines: It is frequently followed by interference with eruption of permanent canine bec. of its later eruption and longer period allowed for shifting of adjacent teeth. March 5, 2012 Dr. Ahmed Basyouni 6
    • B. Local Causes 7. Premature loss of decid. Teeth: c. Premature loss of decid. First molar: Loss, of upp. Ds, rarely followed by impaction of first premolar, bec. Of relatively their early eruption and premolars are smaller than their predecessors. Loss, of low. Ds, causes collapse of the lower labial segment. March 5, 2012 Dr. Ahmed Basyouni 7
    • B. Local Causes 7. Premature loss of decid. Teeth: d. Premature loss of decid. Second molar: Loss of decid. Second molars is the most serious as there is a forward shift of first permanent molars & collapse of lower labial segment. March 5, 2012 Dr. Ahmed Basyouni 8
    • B. Local Causes 7. Premature loss of decid. Teeth: d. Premature loss of decid. Second molar: Main effects will be: 1. Forward shift and mesial tilting of the lower first permanent molar & forward shift and mesial rotation of upp. First permanent molar, resulting in impaction of second premolars in both arches. If they are extracted before eruption of first permanent molars, first permanent molars erupt well forward with less rotation & tilting. 2. Flattening of lower anterior segment (collapse), and if unilateral loss, central line may shift toward affected side. There will be increase in overbite. There may be crowding of upp. Incisors due to loss of splinting effect by the lower arch. March 5, 2012 Dr. Ahmed Basyouni 9
    • B. Local Causes 7. Premature loss of decid. Teeth: e. Premature loss of both upper and lower decid. molars: It is a predisposing factor in the production of prenormal occlusion. As the child will try to bring lower arch forward to be in contact with upper, so he will protrude the mandible. This is called false Class III or pseudomesiocclusion. March 5, 2012 Dr. Ahmed Basyouni 10
    • B. Local Causes 7 Premature loss of decid. Teeth: e. Premature loss of both upper and lower decid. molars: It is distinguished from prenormal occlusion by: a. Manual retrusion of the mandible. b. When teeth are occluded, condyles are out of glenoid fossae. c. There may be labial inclination of lower incisors due to pulling action of the muscles to retrude mandible to its original position. March 5, 2012 Dr. Ahmed Basyouni 11
    • B. Local Causes 8. Prolonged retention of decid. Teeth: Causes: a. Incomplete root resorption. b. Ankylosis of decid. Teeth. c. Absence of permanent teeth. March 5, 2012 Dr. Ahmed Basyouni 12
    • B. Local Causes 8. Prolonged retention of decid. Teeth: Causes: d. Abnormal path of eruption of permanent teeth. e. Endocrine disturbances e.g. Hypothyroidism. f. Cleidocranial dysostosis. g. Nutritional disturbances. March 5, 2012 Dr. Ahmed Basyouni 13
    • B. Local Causes 8. Prolonged retention of decid. Teeth: In the incisor region, delayed root resorption may cause lingual eruption of lower incisors, while upp. Incisors may be displaced either lingually or labially. Retained decid. Should be extracted after the presence of permanent successors are confirmed. In absence of permanent successors, decid. Tooth may serve some years. March 5, 2012 Dr. Ahmed Basyouni 14
    • B. Local Causes 8. Prolonged retention of decid. Teeth: Ankylosis results in retention of decid. Tooth, while neighboring teeth will continue to erupt leaving this tooth behind, this retained tooth called “submerged” and is seen usually in decid. Molars. They are causing malocclusion and stagnation of food, so such tooth should be removed, or crowned in case of absence of permanent successor. March 5, 2012 Dr. Ahmed Basyouni 15
    • 9. Delayed eruption of permanent teeth: B. Local Causes Causes: a. Presence of supernumerary or Odontomes. b. Eruption cyst. c. Retained decid. Teeth. d. Malformation of the tooth e.g. dilaceration. March 5, 2012 Dr. Ahmed Basyouni 16
    • B. Local Causes 9 Delayed eruption of permanent teeth: Causes: e. Ectopic position of the tooth. f. Infection of tooth germ. g. Systemic diseases such as dietary, metabolic, or endocrine disturbances. Removal of cause before closure of root apex would be followed by eruption. If not, tooth has to be exposed surgically & brought down by appliance. March 5, 2012 Dr. Ahmed Basyouni 17
    • B. Local Causes 10. Loss of permanent teeth: a. Incisor teeth: Loss of upp. Central & lateral incisors will result in collapse of anterior part of the dental arch (space being closed by adjacent teeth). Loss of a lower incisor is followed by a similar collapse and loss of intercanine width. March 5, 2012 Dr. Ahmed Basyouni 18
    • B. Local Causes 10. Loss of permanent teeth: b. Canine teeth: Loss of an upp. Canine tooth may affect appearance of the face (Lack of canine eminence) and if unilateral will produce an asymmetry. March 5, 2012 Dr. Ahmed Basyouni 19
    • B. Local Causes 10. Loss of permanent teeth: c. Premolar teeth: First premolars are the teeth most frequently extracted to relieve incisor crowding and in the treatment of Angle’s Class II & III malocclusions. Second premolars are not so often chosen bec. Resulting contact between first premolars and first permanent molars is not usually so good as that between canines and second premolars. Unilateral loss of a premolar may cause a shift of the midline. March 5, 2012 Dr. Ahmed Basyouni 20
    • B. Local Causes 10. Loss of permanent teeth: d. First molars: The most commonly lost teeth by caries are the first permanent molars. i. Effects of early loss of upper first molars: 1.The space is filled most by forward movement of second molar and also to a less extent by distal movement of second premolar and teeth in front of it. This tends to reduce the incisor overbite. March 5, 2012 Dr. Ahmed Basyouni 21
    • B. Local Causes 10. Loss of permanent teeth: d. First molars: 2. If unilateral there may be a shift of the midline to the affected side. 3. Upper second molar tends to rotate forward rather than tilt. It rotates around palatal root. March 5, 2012 Dr. Ahmed Basyouni 22
    • B. Local Causes 10. Loss of permanent teeth: d. First molars: ii. Effects of early loss of lower first molars: 1. The space is filled by mesial tilting of second molar and distal moving second premolar. There is a lack of forward development of anterior teeth which may cause collapse and result in a class II incisor relationship (increased overjet & overbite). 2. If unilateral the lower midline will shift to the affected side. March 5, 2012 Dr. Ahmed Basyouni 23
    • B. Local Causes 10. Loss of permanent teeth: d. First molars: 3. lower second molar tends to tilt rather than rotate forwards. 4. If lost before eruption of lower second premolar, this tooth drift backwards or fail to develop forwards leaving large space between it and the lower first premolar. 5. Opposing maxill. First permanent molars may overerupt. The earlier the loss of the first molars, the less the tilt or rotation of the second molars, when they erupt forward. March 5, 2012 Dr. Ahmed Basyouni 24
    • B. Local Causes 10. Loss of permanent teeth: e. Second molars: These teeth are sometimes extracted in the treatment of certain malocclusions. The third molars must be present on radiographs and of good size and position. March 5, 2012 Dr. Ahmed Basyouni 25
    • B. Local Causes 10. Loss of permanent teeth: f. Third molars: Third molars will be extracted by the oral surgeon if they become impacted. March 5, 2012 Dr. Ahmed Basyouni 26
    • B. Local Causes 11. Trauma: Children are prone to accidents and upp. & low. Incisors are most likely affected from blows on the mouth. Generally, direct trauma to jaws and associated parts may cause: 1. Loss of decid. Teeth & effects will be similar to those arising from premature loss. March 5, 2012 Dr. Ahmed Basyouni 27
    • B. Local Causes 11. Trauma: 2. Permanent incisors may be: a. Dilacerated. b. Displaced in the alveolus which may be fractured. c. Fractured. d. Completely lost. March 5, 2012 Dr. Ahmed Basyouni 28
    • B. Local Causes 11. Trauma: 3. Trauma to TMJ may result in damage & limitation of its movement. 4. Malunion that may follow fractured jaws result in severe degree of malocclusion. Trauma March 5, 2012 Dr. Ahmed Basyouni 29
    • B. Local Causes 12. Local pathological factors: Cysts, Odontoms, Tumors These include: a. Cysts or tumors in jaws may displace neighboring teeth creating malocclusion. b. Scar tissues resulting from burns of lips & cheeks may contract & upset balance of musculature. March 5, 2012 Dr. Ahmed Basyouni 30
    • B. Local Causes 12. Local pathological factors: c. Inflammatory conditions causing ankylosis of TMJ may cause damage of condylar cartilage (main growth center), mandible become deficient in affected side, ascending ramus become short & resulting malocclusion is severe. March 5, 2012 Dr. Ahmed Basyouni 31
    • Summary General Causes 1.Evolution: 2. Congenital malformation: 3. Endocrinal disturbances: 4. Nutritional deficiency 5. Pathological Conditions: March 5, 2012 Dr. Ahmed Basyouni 32
    • B. Local Causes Summary Local Causes 1. Congenital missing teeth: 2. Supernumerary teeth: 3. Teeth of abnormal size and form: 4. Abnormal path of eruption: 5. Abnormal labial frenum: 6. Abnormal pressure habits: a. Thumb sucking: b. Tongue thrusting: c. Nail biting: d. Abnormal swallowing: e. Mouth breathing: March 5, 2012 Dr. Ahmed Basyouni 33
    • B. Local Causes Summary 7. Premature loss of decid. Teeth: 8. Prolonged retention of decid. Teeth: 9. Delayed eruption of permanent teeth: 10. Loss of permanent teeth: 11. Trauma: 12. Local pathological factors: March 5, 2012 Dr. Ahmed Basyouni 34
    • March 5, 2012 Dr. Ahmed Basyouni 35