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Jaw rotation(ortho)

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Jaw rotation(ortho)

  1. 1. BY MUHAMMAD SHARIQ SOHAIL FINAL YEAR BDS ZIAUDDIN UNIVERSITY ROTATION OF JAWS DURING GROWTH AND MATURATIONAL AND AGING CHANGES
  2. 2. OBJECTIVES 1)Rotation of jaws during growth 2)Interaction between Jaw rotation and Tooth eruption. 3)Maturational and Aging changes.
  3. 3. ROTATION OF JAWS DURING GROWTH INTERNAL ROTATION: 1)Rotation occurs in the core of jaw bone. 2) Two types of Internal Rotation. A)Matrix Rotation-Rotation Around Condyle(25%) B)Intra Matrix Rotation– Rotation Centered within mandible(75%). 3)Produces 15 degrees of Internal Rotation. EXTERNAL ROTATION: 1)Rotation due to surface Changes. 2)In Remaining parts of mandible like Alveolar process, Muscular process. Condylar process. 3)Produces 11-12 degrees of External Rotation. TOTAL ROTATION= INTERNAL- EXTERNAL ROTATION= 3-4 DEGREES
  4. 4. Internal rotation tends to move jaw forward and upwards. External Rotation compensates and moves jaw backward and downwards. ER IR
  5. 5. CLINICAL ASPECT SHORT FACE TYPE (LOW ANGLE CASE) •More Anterior Rotation/Growth •Reduced Lower Facial Height. •Almost Horizontal Palatal Plane. •Low Mandibular Plane Angle. •Prominent Goneal notch. •A deep Bite Malocclusion and Crowded Incisors. REASON: Normal Internal Rotation but reduced External Compensation. HIGH FACE TYPE (HIGH ANGLE CASE) •More posterior Rotation/Growth. •Increased Lower Facial Height. •Palatal Plane down Posteriorly. •High Mandibular Plane Angle. •Not such Prominent. •Anterior Open Bite Malocclusion and Mandibular Deficiency. REASON: Excessive Backward Rotation or lack of Forward Rotation.
  6. 6. INTERACTION BETWEEN JAW ROTATION AND TOOTH ERUPTION ▸Jaw Rotation Influences the direction of eruption and ultimate Antero-Posterior position of Incisor teeth. ▸MAXILLARY TEETH: a)The path of eruption of maxillary teeth in Downward and somewhat forward. b)Normally maxilla rotates few degress forward but frequently rotates slightly backward(which keep teeth in upright postion and decrease their prominence). c)Translocation and True Eruption ; Translocation contributes about half the total Maxillary tooth movement during aldolescent growth. ▸MANDIBULAR TEETH: a)The path of eruption of Mandibular teeth is upward and forward. b)Normal Internal Rotation caries Mandible carries jaw upward and infront. C)This alters eruption pathway and make incisor uprightMolars migrate mesially and decrease in Arch length. *Internal Rotation is more in mandible than maxilla that’s why decrease in mandibular arch length is greater than maxillary arch length.*
  7. 7. ▸New implant studies confirmed that changes in anterior position of incisor teeth are a major influence on arch length.
  8. 8. MATURATIONAL AND AGING CHANGES Maturational changes affect both soft and hard tissues of face and jaws with greater long term changes in soft tissue. ▸Changes in Facial Soft tissue. ▸Changes in Teeth and Supporting structure. ▸Changes in Alignment and Occlusion. ▸Facial Growth in Adults.
  9. 9. CHANGES IN FACIAL SOFT TISSUE Changes in facial soft tissue continue with aging,they are much larger in magnitude than changes in the hard tissue of the face and jaws. ▸The lips and other soft tissues of the face, Sag downward with aging. ▸Lips become progressively thinner with less vermillion display.
  10. 10. CHANGES IN TEETH AND SUPPORTING STRUCTURES ▸Changes in Pulp Chamber. ▸Change in Gingival attachment. ▸Occlusal and Interproximal wear.
  11. 11. CHANGES IN ALIGNMENT AND OCCLUSION ▸The alveolar bone bends during heavy mastication, allowing the teeth to move relative to each other. THEORIES OF INCISOR CROWDING: ▸Lack of Normal Attrition in modern diet. ▸Pressure from Third Molars. ▸Late Mandibular Growth.
  12. 12. FACIAL GROWTH IN ADULTS ▸There is an increase in essentially all of the facial dimensions, but both size and shape of Cranio facial complex altered with time. ▸Vertical Changes in Adult life were more prominent than anteroposterior changes, where as width were least evident. ▸In general, Males showed a net rotation of the jaws in a forward direction, slightly decreasing Mandibular plane angle, where as Females had a tendency toward backward rotation, with an Increase in the Mandibular plane angle. But due to compensatory changes were noted in Dentition so that occlusal relationship largely were maintained.. ▸The soft tissue changes involved an 1)Elongation of the Nose(significantly longer during adult). 2)Flattening of the Lips. 3)An augementation of the Chin. *There is not adequate data available that whether growth rates are greater in early in late adult life, but even if they are, skeletal growth comes much closer to being continues throughout life..*
  13. 13. REFERENCE: ▸CONTEMPORARY ORTHODONTICS BY WILLAM R. PROFFIT
  14. 14. THANKS! Any questions?

Hinweis der Redaktion

  • Posterior ramus resorption nd anterior lower border remain unchanged or undergoes slight apposition. Forward movement and given negative sign backward movement positive sign
  • Centre of Rotation: Forward : condylar head lower premolars lower incisal edges distal occluding molars Backwards: condylar head distal occluding molars
  • Mandibular deficiency because chin rotates back as well as down.
  • Snmp 32 +/- 4 uisn 102 +/- 4 impa 90+/- 4
  • Lips length by 3.2mm thinned 3.6mm with an average of 1.4 mm in late adult life
  • 1)Decrease xposure of upper teeth and increase show of lower teeth.it is important in ortho treatment that vertical relationship of the lip to the teeth will change because of the soft tissue change.Leaving the upper incisors somewhat more exposed than the ideal adult relationship is necessary in treatment is necessary in treatment of an aldolescent. 2)teeth should be placed to supprot lips in aldolececnt, if the lips are not somewhat prominent when treatment ends in aldolescent, they are likely to appear too thin in the years to come.This must be kept in mind when retraction of protuding incisors is planned.
  • Late mandibular growth--- later obserevd that even after extraction of premolar teeth there was crowdig preset so this theory was failed.. 1)Mandible is displaced distally accompaned by distortion of tmj function and displacemtn of disc 2)upper incisors flare forward opening space between these teeth. 3)the lower incisors displace distally decreasing intercanine distance and become crowded. Anterior Open bite pateints---backward rotation high----thursting of lips against incisors---lips push it backwards and make crowding…
  • 1)An apparent deccelaration of growth in females n the late teens was followed by a resumption of growth in females in the late teens was followed by a resumption of growth during twenties. 2)It appears that a womans first pregnancy often produces some growth of her jaws.

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