Issuu on Google+

DEVELOPMENT OF MANDIBLE

INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com  www.indiandentalacademy.com


Contents      

Introduction Prenatal growth Ossification Concept of remodeling Postnatal growth Clinical implications

www.indiandentalacademy.com


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? www.indiandentalacademy.com


Prenatal Growth

www.indiandentalacademy.com


Prenatal Growth

www.indiandentalacademy.com


Prenatal Growth

www.indiandentalacademy.com


Prenatal Growth

36-38 day Iul

Ectomesenchymal cells Epi. Of 1st arch www.indiandentalacademy.com

Osteogenic Memb.


Prenatal Growth

6th week

www.indiandentalacademy.com


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 www.indiandentalacademy.com

around


Prenatal Growth Fate of Meckel’s cartilage

www.indiandentalacademy.com


www.indiandentalacademy.com


Prenatal Growth New bone

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

Lamellar Lamellar bone bone ++ haversian haversian system system www.indiandentalacademy.com


Prenatal Growth

10th & 12th week Sec. accessory cartilage

www.indiandentalacademy.com


Prenatal Growth 

Secondary cartilage of coronoid process

Develop within temporalis muscle

Incorporated into IMB of ramus

Disappear before birth

www.indiandentalacademy.com


Prenatal Growth   

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

syndesmosis

synostosis

www.indiandentalacademy.com


Prenatal Growth   

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

www.indiandentalacademy.com


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

 

www.indiandentalacademy.com


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

www.indiandentalacademy.com


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 www.indiandentalacademy.com


Post Natal Growth 

Types of ossification

Mechanism of bone growth

Anatomy

Theories of growth www.indiandentalacademy.com


Types Of Ossification 

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

INTRAMEMBRANOUS

ENDOCHONDRAL

www.indiandentalacademy.com


Intramembranous Ectomesenchyme

Epithelium

Osteogenic membrane

Osteoblast Centre of ossification Osteoid matrix

www.indiandentalacademy.com


Intramembranous

www.indiandentalacademy.com


Intramembranous

www.indiandentalacademy.com


Endochondral Mesenchymal cells

osteoblast

Cart. Matrix of glycoproteins

Cart. template Blood vessels

Osteoid matrix

mineralized www.indiandentalacademy.com


Endochondral

www.indiandentalacademy.com


Endochondral

www.indiandentalacademy.com


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 www.indiandentalacademy.com


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

www.indiandentalacademy.com


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 www.indiandentalacademy.com


www.indiandentalacademy.com


Anatomy

www.indiandentalacademy.com


Theories Of Growth

www.indiandentalacademy.com


Theories Of Growth

www.indiandentalacademy.com


Other Theories

ENLOW’S “V” PRINCIPLE

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


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 www.indiandentalacademy.com


“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 www.indiandentalacademy.com


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

www.indiandentalacademy.com


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

www.indiandentalacademy.com


Post Natal Growth And Development GROWTH IN LENGTH   

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

www.indiandentalacademy.com


Post Natal Growth And Development 

Main sites of post natal growth in the Mandible

Condylar cartilage

Posterior border of the Rami

Alveolar ridges

www.indiandentalacademy.com


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. www.indiandentalacademy.com


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 www.indiandentalacademy.com


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

www.indiandentalacademy.com


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 www.indiandentalacademy.com


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 www.indiandentalacademy.com

based mainly on animal experiments


Ramus 

Moves progressively posterior by:Deposition POSTERIOR PART

Resorption

ANTERIOR PART

www.indiandentalacademy.com


Ramus Superior part of ramus below sigmoid notch

Lingual -Deposition Buccal - Resorption

Lower part of ramus below the Coronoid process

Buccal - Deposition Lingual - Resorption

www.indiandentalacademy.com


Ramus

www.indiandentalacademy.com


Ramus

www.indiandentalacademy.com


Coronoid process Posterior

Lingual surface

Superior Medially Follows ‘v’ principle

www.indiandentalacademy.com


Coronoid process ‘’V’ PRINCIPLE OF ENLOW

www.indiandentalacademy.com


Coronoid process ď Ź

Medial

ď Ź

Increases vertical length

Deposition on lingual side

Posterior Growth

Resorption - buccal surface

www.indiandentalacademy.com


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

www.indiandentalacademy.com


Ramus corpus junction

Inferior Border of junction - resorption

Forms Antegonial notch

www.indiandentalacademy.com


Antegonial notch Size depends upon ramus – corpus angle

www.indiandentalacademy.com


Lingual Tuberosity ď Ź

ď Ź

Grows posterior and medial by deposition

Resorptive field belowLingual fossa

www.indiandentalacademy.com


Alveolar Process

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

www.indiandentalacademy.com


Alveolar Process 

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

Maintains vertical height

Adaptive remodeling makes orthodontic tooth movement possible

www.indiandentalacademy.com


Alveolar Process Lingual Lingual movement movement of of anteriors anteriors

www.indiandentalacademy.com


Mental Protuberance

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

Poorly developed in infants

www.indiandentalacademy.com


Mental Protuberance ď Ź

Forms by osseous deposition during childhood

ď Ź

Prominence is accentuated by bone resorption above it

www.indiandentalacademy.com


Mental Protuberance

Reversal between 2 growth fields

Concave  convex

Reversal line could be High or low www.indiandentalacademy.com


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 www.indiandentalacademy.com


Symphysis Menti

Limited growth till fusion

No widening after fusion

www.indiandentalacademy.com


Mental Foramen

www.indiandentalacademy.com


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

www.indiandentalacademy.com


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

www.indiandentalacademy.com


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 www.indiandentalacademy.com


1. Congenital

2. Developmental

• Agnathia

Infantile cortical hyperostosis

Achondroplasia

• Macrognathia

Torus mandibularis

• Facial hemihypertrophy

Stafne’s cyst

• Facial hemiatropy

Odontogenic cyst

Odontogenic tumor

• Micrognathia

www.indiandentalacademy.com


Age Changes Of The Mandible

www.indiandentalacademy.com


References     

Craniofacial embryology – SPERBER Facial growth – ENLOW Contemporary orthodontics – PROFFIT Handbook of orthodontics – MOYERS Principles and practice of orthodontics –GRABER

www.indiandentalacademy.com


www.indiandentalacademy.com Leader in continuing dental education

www.indiandentalacademy.com


Dev of mand/ dental implant courses by Indian dental academy