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INDIAN DENTAL ACADEMY Leader in continuing dental education 

Contents      

Introduction Prenatal growth Ossification Concept of remodeling Postnatal growth Clinical implications

Introduction Measurements in the ceph show the results of Growth of something, somewhere, at some time, But of what? Why? And in response to which Biologic stimuli or energies?

Prenatal Growth

Prenatal Growth

Prenatal Growth

Prenatal Growth

36-38 day Iul

Ectomesenchymal cells Epi. Of 1st arch

Osteogenic Memb.

Prenatal Growth

6th week

Prenatal Growth Trough Trough for for dev. dev. teeth teeth

1째centre 1째centre of of ossification ossification below

Infr Infr alv. alv. Nerve Nerve && Incisive Incisive branch branch


Prenatal Growth Fate of Meckel’s cartilage

Prenatal Growth New bone

Woven Woven bone bone 55thth month month i.i. u. u.

Lamellar Lamellar bone bone ++ haversian haversian system system

Prenatal Growth

10th & 12th week Sec. accessory cartilage

Prenatal Growth 

Secondary cartilage of coronoid process

Develop within temporalis muscle

Incorporated into IMB of ramus

Disappear before birth

Prenatal Growth   

Sec. cartilage at Mental region 1 or 2 small cartilage mental ossicles(7th IUL) Incorporated into IMB



Prenatal Growth   

Sec. Condylar cartilage (10th week of IUL) Grow interstitially & appositionally 14th week 1st evidence of Endochondral bone formation

Condylar cartilage 

Serves as a growth site

Brings changes in the mandibular position and form

Growth increases during puberty Peak 12 – 14 years Ceases by 20 years

 

Neonatal mandible   

Ascending Ramus low and wide Large Coronoid process Body – open shell containing tooth buds and partially formed deciduous teeth Mandibular canal that runs low in the body

Differential growth During During fetal fetal life life 88 weeks weeks -- mandible mandible >> maxilla maxilla 11 11 weeks weeks -- mandible mandible == maxilla maxilla 13 13 –– 20 20 weeks weeks maxilla maxilla >> mandible mandible At At Birth Birth Mandible Mandible tends tends to to be be retrognathic retrognathic Early Early post post natal natal life life -- orthognathic orthognathic

Post Natal Growth 

Types of ossification

Mechanism of bone growth


Theories of growth

Types Of Ossification 

Mandible is the second bone in the body to be ossified There are two types of ossification :



Intramembranous Ectomesenchyme


Osteogenic membrane

Osteoblast Centre of ossification Osteoid matrix



Endochondral Mesenchymal cells


Cart. Matrix of glycoproteins

Cart. template Blood vessels

Osteoid matrix




Clinical significance 

     

In postnatal life distinction b/w two is of no significance:# of intramembranous bone Surface remodelling of endochondral bone Prenatal life – congenital defects Achondroplasia – Endochondral bone Cleidocranial dysostosis – Intramembranous bone Osteogenesis Imperfecta – both type

Parts Of Mandible Derived From 1. INTRAMEMBRANOUS OSSIFICATION i) Whole body of mandible except the anterior part

ii) Ramus of mandible as far as mandibular foramen 2 . ENDOCHONDRAL OSSIFICATION i)

Anterior portion of the mandible (symphysis)

ii) Part of ramus above the mandibular foramen iii) Coronoid process iv) Condylar process

Mechanisms Of Bone Growth Growth Of The Mandible Primarily Involve

1. Bone remodelling Process Of Bone Deposition And Resorption

2. Cortical drift Combination of bone deposition and resorption resulting in growth movement towards deposition surface

3. Displacement Movement of whole bone as a unit

I) Primary displacement II) Secondary displacement


Theories Of Growth

Theories Of Growth

Other Theories


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

Enlow’s Counterpart Principle 

‘The growth of any given facial or cranial part relates

specifically to other structural and geometric “counter” parts in the face and cranium’. Eg. Maxillary arch is counter part of mandibular arch. Regional Regional part part

counter counter part part

Balanced Balanced growth growth

“The “The human human mandible mandible has has no no one one design design for for life. life. Rather Rather it it adapts adapts and and remodels remodels through through the the seven seven stages stages of of life, life, from from the the slim slim arbiter arbiter of of things things to to come come in in the the infant, infant, through through aa powerful powerful dentate dentate machine machine and and even even weapon weapon in in the the full full flesh flesh of of maturity, maturity, to to the the pencil pencil thin, thin, porcelain porcelain like like problem problem that that we we struggle struggle to to repair repair in in the the adversity adversity of of old old age.” age.” D.E. D.E. Poswillo, Poswillo, 1988 1988

Post Natal Growth And Development GROWTH TIMING Growth of width of mandible is completed first, then growth in length and finally growth in height

Post Natal Growth And Development WIDTH OF MANDIBLE 

Growth in width is completed before adolescent growth spurt

Intercanine width does increase after 12 years

Both molar and bicondylar width shows small increase until growth in length ends

Post Natal Growth And Development GROWTH IN LENGTH   

Growth in length continues through puberty Girls—14-15 years boys---18-19 years

Post Natal Growth And Development 

Main sites of post natal growth in the Mandible

Condylar cartilage

Posterior border of the Rami

Alveolar ridges

Condylar cartilage Secondary cartilage Dual function

articular articular

growth growth Not a pri. Centre of growth but rather 2° 2° in in evolution evolution 2° 2° in in embryonic embryonic origin origin 2°in 2°in adaptive adaptive responses responses to to changing changing dev. dev.

Is the Condylar cartilage the principle force that produces the displacement of the mandible ?

For many years considered primary growth center FMH - Condyle absent yet mandible positioned normally Considered secondary cartilage -no intrinsic growth potential

Petrovic et al - Role of hormones Experiments involving transplantation of the condyle Johnston et al - Detached condyle from the body of mandible in guinea pigs Injection of papain - Inhibition of chondrogenesis Koski et al - Periosteal tension in condylar neck-lateral pterygoid- controls condylar growth

Condylar cartilage and functioning muscles translate the mandible and in the absence of one the other does best to compensate

Integrity of periosteum is important

When environment is changed compensatory contributions are enhanced

Current Concept 

Condylar cartilage does have a measure of intrinsic genetic programming But extra condylar factors are needed to sustain this activity

Physiologic inductors

Intrinsic and extrinsic biomechanical forces

ENLOW : Increase pressure – growth inhibition Decrease pressure – stimulates growth

based mainly on animal experiments

Ramus 

Moves progressively posterior by:Deposition POSTERIOR PART



Ramus Superior part of ramus below sigmoid notch

Lingual -Deposition Buccal - Resorption

Lower part of ramus below the Coronoid process

Buccal - Deposition Lingual - Resorption



Coronoid process Posterior

Lingual surface

Superior Medially Follows ‘v’ principle

Coronoid process ‘’V’ PRINCIPLE OF ENLOW

Coronoid process ď Ź


ď Ź

Increases vertical length

Deposition on lingual side

Posterior Growth

Resorption - buccal surface

Body of 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 due to eruption of the teeth

Ramus corpus junction

Inferior Border of junction - resorption

Forms Antegonial notch

Antegonial notch Size depends upon ramus – corpus angle

Lingual Tuberosity ď Ź

ď Ź

Grows posterior and medial by deposition

Resorptive field belowLingual fossa

Alveolar Process

Adds to the height and thickness of the mandibular body Teeth absent fails to develop Teeth extracted resorbs

Alveolar Process 

Maintain occlusal relationship during differential mandibular & midfacial growth– buffer zones

Maintains vertical height

Adaptive remodeling makes orthodontic tooth movement possible

Alveolar Process Lingual Lingual movement movement of of anteriors anteriors

Mental Protuberance

Formed by mental ossicles from accessory cartilage and ventral end of Meckel’s cartilage

Poorly developed in infants

Mental Protuberance ď Ź

Forms by osseous deposition during childhood

ď Ź

Prominence is accentuated by bone resorption above it

Mental Protuberance

Reversal between 2 growth fields

Concave  convex

Reversal line could be High or low

Chin ď Ź

Protrusive chin is unique human trait

ď Ź

More prominent in male

ď Ź

Less prominent in female

Under Under dev. dev. Of Of chin chin -- microgenia microgenia

Symphysis Menti

Limited growth till fusion

No widening after fusion

Mental Foramen

Factors Affecting Growth A) Systemic Factors 1. Genetic 2. Hormonal imbalance 3. Nutrition 4. Systemic illness or chronic illness 5. Localized alteration/ diseases of uterus 6. Systemic illness in mother 7. Drugs

B) Local factors 1. Vascular abnormality

2. Lymphatic disturbance 3. Neurologic disease 4. Local infection 5. Ear infection or mastoiditis 6. Ankylosis 7. Trauma or fracture 8. Birth injury 9. Habits

Anomalies of mandible  Some of the syndromes associated with mandibular abnormality i) Down’s syndrome i) Marfan’s syndrome ii) Turners syndrome iii) Kleinfelter’s syndrome iv) Pierre-robin syndrome v) Treacher- collin syndrome

1. Congenital

2. Developmental

• Agnathia

Infantile cortical hyperostosis


• Macrognathia

Torus mandibularis

• Facial hemihypertrophy

Stafne’s cyst

• Facial hemiatropy

Odontogenic cyst

Odontogenic tumor

• Micrognathia

Age Changes Of The Mandible

References     

Craniofacial embryology – SPERBER Facial growth – ENLOW Contemporary orthodontics – PROFFIT Handbook of orthodontics – MOYERS Principles and practice of orthodontics –GRABER Leader in continuing dental education

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