Jaw rotation- Chapter no. 4 (Proffit) department of orthodontics

1. BY MUHAMMAD SHARIQ SOHAIL
FINAL YEAR BDS
ZIAUDDIN UNIVERSITY
ROTATION OF JAWS DURING
GROWTH AND MATURATIONAL
AND AGING CHANGES

2. OBJECTIVES
1)Rotation of jaws during growth
2)Interaction between Jaw rotation and
Tooth eruption.
3)Maturational and Aging changes.

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. Internal rotation tends to move jaw forward
and upwards.
External Rotation compensates and moves
jaw backward and downwards.
ER
IR

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.

7. 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.*

8. ▸New implant studies confirmed that changes in anterior position of
incisor teeth are a major influence on arch length.

9. 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.

10. 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.

11. CHANGES IN TEETH AND SUPPORTING
STRUCTURES
▸Changes in Pulp Chamber.
▸Change in Gingival attachment.
▸Occlusal and Interproximal wear.

12. 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.

13. 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..*

14. REFERENCE:
▸CONTEMPORARY ORTHODONTICS BY WILLAM R. PROFFIT

15. THANKS!
Any questions?