Rishiraj College of Dental Sciences BhopalDEPARTMENT OF PEDIATRIC DENTISTRYClick to edit Master subtitle style SEMINAR POST NATAL DEVELOPMENT OF MANDIBLE

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SUBMITTED BY Samarth Vajpayee BDS final Year 2010- 11

Introduction

Conte nts

Theories of growth Pre-natal development of mandible Post natal growth Age changes in mandible Factors affecting growth Abnormalities Conclusions References9/3/12

INTRODUCTION In all biological sense development is a process of continuous

changes occurring in predetermined order.

Development is an increase in complexity. (Todd 1931)

Development is used to indicate an increase in skill and complexity of

function.

(Lowrey 1951)

Development refers to all naturally occurring unidirectional changes in

life of an individual from its existence as a single cell to its elaboration as multifunctional unit terminating in death. (Moyer 1981)

The act or process of natural progression from a previous, lower or

embryonic stage, to a later, more complex or adult stage . (stedman 1990)

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Theories of Growth

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OTHER THEORIES

ENLOWS V PRINCIPLE

The growth and enlargement of bones occur towards wide end of v due to differential deposition and resorption

ENLOWS COUNTERPART PRINCIPLE

Growth of any facial or cranial part relates specifically to other structural and geometric counterparts

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Brief Overview Of Prenatal Development Of Mandible Mandible is the derivative of the first pharyngeal arch

Dorsal portion is known as maxillary process

Ventral portion known as mandibular process or Meckels

cartilage

Development of mandible starts at 4th week i.U.L

Center of face formed by stomodeum, surrounded by first

pair 9/3/12 of pharyngeal arches

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4 week embryo

POST NATAL GROWTH GROWTH TIMING

Growth of width of mandible is completed first, then growth in length and finally growth in height

WIDTH OF MANDIBLE

Growth in width is completed

before adolescent growth spurt intercanine width does increase 9/3/12

GROWTH IN HEIGHT

Continues in both the sexes for longer period

Growth increase occurs with concomitant eruption of teeth and continues to increase through out life and decreases in adult life

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1. RAMUS OF MANDIBLE

Ramus moves progressively posterior by a combination of deposition and resorption Resorption occurs on the anterior part and the deposition occurs on the posterior part---drift

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2. BODY OF THE MANDIBLE The increase in width of the mandible occurs primarily due to resorption on the inside and deposition on the outside

Increase in length occurs due to drift of the ramus posteriorly

Increase in height occurs cue to eruption of the teeth

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3. ANGLE OF THE MANDIBLE On the lingual side, resorption takes place on posteroinferior aspect,while deposition occurs on anterosuperior aspect

the the

On the buccal side ,resorption occurs on anterosuperior part while resorption occurs on posteroinferior

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4. ALVEOLAR PROCESS

Develops in response to presence of tooth buds It increases in height as the teeth erupts

This increases the heigth and thickness of the body of mandible 5.CHIN Prominence of the mental protruberance is accentuated by bone resorption that occurs above the alveolar processcreating a concavity

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6.CONDYLE

It has been recognized as an important growth site There are two schools of thought

I) growth at the condyle pushes it towards the cranial base, this leads to displacement of the mandible forwards and downwards

RAYMOND.C.BERNABEI AND LYSLE.E.JOHNSTON (1978) FOUND THAT CONDYLAR CARTILAGE IS NEEDED FOR NORMAL GROWTH

II) it is now believed that growth of soft tissues surrounding the mandible carries it away from the cranial base and growth occurs at condyle to maintain constant contact

ROSARIO.BERRAQUERO et al (1992) FOUND THAT CONDYLAR CARTILAGE IS A SECONDARY GROWTH CENTER AND NOT A PRIMARY GROWTH CENTER

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RONNING.O OBSERVED THAT THERE WAS NO GROWTH OF THE CONDYLAR CARTILAGE AFTER INTRACEREBRAL IMPLANTATION

JANSEN.H.W AND DUTERLOO.H.S (1986) STATED THAT CONDYLAR CARTILAGE SHOWED SIGNIFICANTLY LESS GROWTH THAN OTHERS, SO THE CONDYLE DOES NOT ACT AS A GROWTH CENTER

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7. CORONOID PROCESS

It follows enlarging v principle

In longitudinal section, deposition occurs on lingual side of both left and right coronoid process

General growth is posteriorly, superiorly and medially

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GROWTH ROTATIONi) ii)

REMODELLING DISPLACEMENT The ramus undergoes remodeling rotation to decrease the gonial angle---this produces displacement rotation of the mandible as a whole

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BJORK AND CO-WORKERS DESCRIBED TWO TYPES Rotation that occurs around the core of the mandible that surrounds the inferior alveolar nerve

1. INTERNAL ROTATION

i)

MATRIX ROTATION ROTATION AROUND THE CONDYLE INTRAMATRIX ROTATION ROTATION AROUND THE BODY

ii)

2. EXTERNAL ROTATION9/3/12 SURFACE CHANGES DUE TO RESORPTION AND

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Overall changes in orientation of jaw results from the combination of internal and external rotation

The core of mandible during growth rotates in such a way that tends to decrease the mandibular plane angle i.E. Up anteriorly and down posteriorly

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The rotation is considered forward if growth is more posteriorly than anteriorly

The rotation is backward if anterior growth is more than posterior

Individuals of short face type have excessive forward growth of mandible. They have decreased mandibular and gonial plane angle square jaw

Long face individuals have excessive backward rotation of mandible and have increased mandibular plane angle

In general, males have slight forward growth mandibular plane angle

and decreased

Females have slight backward rotation of mandible and increased mandibular plane angle9/3/12

Age Changes of Mandible

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Mandible At Birth

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Changes Produced in the Mandible by Age At birth The body of the bone is a mere shell, containing the sockets

of the two incisor, the canine, and the two deciduous molar teeth, imperfectly partitioned off from one another.

The mandibular canal is of large size, and runs near the

lower border of the bone; the mental foramen opens beneath the socket of the first deciduous molar tooth.

The angle is obtuse (175), and the condyloid portion is

nearly in line with the body.

The coronoid process is of comparatively large size, and9/3/12 projects above the level of the condyle.

Mandible in Childhood

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The two segments of the bone become joined at the

symphysis, from below upward, in the first year; but a trace of separation may be visible in the beginning of the second year, near the alveolar margin.

The body becomes elongated in its whole length, but more

especially behind the mental foramen, to provide space for the three additional teeth developed in this part.

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The depth of the body increases owing to increased growth

of the alveolar part, to afford room for the roots of the teeth, and by thickening of the subdental portion which enables the jaw to withstand the powerful action of the masticatory muscles; but the alveolar portion is the deeper of the two, and, consequently, the chief part of the body lies above the oblique line.

The mandibular canal, after the second dentition, is situated

just above the level of the mylohyoid line; and the mental foramen occupies the position usual to it in the adult. The angle becomes less obtuse, owing to the separation of the jaws by the teeth; about the fourth year it is 140.9/3/12

Adult Mandible

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The alveolar and subdental portions of the

body are usually of equal depth.

The mental foramen opens midway between

the upper and lower borders of the bone, and the mandibular canal runs nearly parallel with the mylohyoid line.The ramus is almost vertical in direction, the

angle measuring from 110 to 120.9/3/12

Fully Developed Adult Mandible (Outer aspect)9/3/12

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Fully Developed Adult Mandible (inner aspect)

Mandible in Old Age

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The bone becomes greatly reduced in size, for with the loss

of the teeth the alveolar process is absorbed, and, consequently, the chief part of the bone is below the oblique line.

The mandibular canal, with the mental foramen opening

from it, is close to the alveolar border.

The ramus is oblique in direction, the angle measures about

140, and the neck of the condyle is more or less bent backward.

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FACTORS AFFECTING GROWTHA)

SYSTEMIC FACTORS

1. 2. 3. 4.

Genetic Hormonal Imbalance Nutrition Systemic Illness Or Chronic Illness Localised Alteration/ Diseases Of Uterus Systemic Illness In Mother Drugs

5.

6. 7.

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B) LOCAL FACTORS1.

Vascular Abnormality

2. Lymphatic Disturbance 3. Neurologic Disease 4. Local Infection 5. Ear Infection Or Mastoiditis 6. Ankylosis 7. Trauma Or Fracture9/3/12

8. Birth Injury 9. Habits

Abnormalities

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Abnormalities

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Abnormalities

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SUMMARY Mandible develops from first

pharyngeal arch There are two phases of

development of mandible pre and post natal. Several changes occur in the

mandible during the developmental period Any disturbance during the normal

growth of the mandible reflects as a anomaly.

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REFERENCES: Contemporary Orthodontics William R. Proffit. Textbook of Pedodontics Shobha Tandon Textbook of Pedodontics S. G. Damle Textbook of Oral Pathology William Shaffer, 4th Edition Textbook Of Anatomy Gray Growth in situ of isolated mandibular segments.

Raymond.c.Bernabei AJO-1978;73-74;24-35 Role of condylar cartilage in mandibular growth-Rosario.

Berraquero et al AJO-1992;102;220-69/3/12

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RCDS & RC,

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