BY MUHAMMAD SHARIQ SOHAILFINAL YEAR BDS ZIAUDDIN UNIVERSITY

ROTATION OF JAWS DURING

GROWTH AND MATURATIONAL

AND AGING CHANGES

OBJECTIVES

1)Rotation of jaws during growth

2)Interaction between Jaw rotation and Tooth eruption.

3)Maturational and Aging changes.

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

Internal rotation tends to move jaw forward and upwards.

External Rotation compensates and moves jaw backward and downwards.

ER

IR

CLINICAL ASPECTSHORT 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.

INTERACTION BETWEEN JAW ROTATION AND TOOTH ERUPTION

▸Jaw Rotation Influences the direction of eruption and ultimate Antero-Posteriorposition 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 uprightMolars 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.*

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

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.

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.

CHANGES IN TEETH AND SUPPORTING STRUCTURES

▸Changes in Pulp Chamber.

▸Change in Gingival attachment.

▸Occlusal and Interproximal wear.

CHANGES IN ALIGNMENT AND OCCLUSION

▸The alveolar bone bends during heavy mastication, allowing the teeth to moverelative to each other.

THEORIES OF INCISOR CROWDING:

▸Lack of Normal Attrition in modern diet.▸Pressure from Third Molars.▸Late Mandibular Growth.

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 aswidth were least evident.

▸In general, Males showed a net rotation of the jaws in a forward direction, slightly decreasingMandibular 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..*

REFERENCE:▸CONTEMPORARY ORTHODONTICS BY WILLAM R. PROFFIT

THANKS!

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