Issuu on Google+

GROWTH AND DEVELOPMENT OF MANDIBLE

www.indiandentalacademy.com


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

www.indiandentalacademy.com


www.indiandentalacademy.com


CONTENTS      

DEFINITIONS PRENATAL GROWTH POSTNATAL GROWTH FACTORS AFFECTING GROWTH AGE CHANGES IN MANDIBLE ANOMOLIES IN DEVELOPMENT MANDIBLE REFERENCES www.indiandentalacademy.com


What is Growth?  

Growth refers to increase in size- Todd Growth usually refers to an increase in size and number – Proffit Self multiplication of living substance – J.S. Huxley Entire series of sequential anatomic and physiologic changes taking place from the beginning of prenatal life to senility Meridith www.indiandentalacademy.com


What is Development? ď Ž

ď Ž

It is the progress towards maturity – Todd Development refers to all the naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death Moyers www.indiandentalacademy.com


•PRENATAL •POSTNATAL

www.indiandentalacademy.com


Prenatal Growth 

It’s the most dynamic phase and is divided as

•Preimplantation period •Embryonic period •Fetal period

www.indiandentalacademy.com


Formation of the Pharyngeal Arches ď Ž

The mesoderm of the lateral plate of the ventral foregut becomes segmented to form a series of five distinct bilateral mesenchymal swelling called as the Pharyngeal Arches.

www.indiandentalacademy.com


th 4www.indiandentalacademy.com week


4 www.indiandentalacademy.com week embryo


Contents of each arch

   

Skeletal element Striated muscle Nerve Artery

www.indiandentalacademy.com


Internal view of pharyngeal floor and cut arches www.indiandentalacademy.com


www.indiandentalacademy.com


Mandibular Arch

   

Meckel’s cartilage Musculature Mandibular nerve Artery- maxillary and external carotid

www.indiandentalacademy.com


Meckel’s cartilage   

41th- 45th day of I.U.L Provides a template Extends from Otic capsule –Midline or Symphysis

www.indiandentalacademy.com


Ossification of Meckel’s cartilage ď Ž

Mandibular division of trigrminal nerve

Neurotrophic factor

Osteogenesis

www.indiandentalacademy.com


Ossification of Meckel’s cartilage 

In 6th week IU

www.indiandentalacademy.com


Ossification of Meckel’s cartilage Trough Trough for for dev. dev. teeth teeth

1°centre 1°centre of of ossification ossification below

Infr Infr alv. alv. Nerve Nerve && Incisive Incisive branch branch www.indiandentalacademy.com

around


Ossification of Meckel’s cartilage 

Ossification spreads dorsally and ventrally •Body •Ramus Ossification stops at the site that will become mandibular lingula www.indiandentalacademy.com


Fate of Meckel’s cartilage   

 

Meckel’s cartilage lacks enzyme phosphatase It disappears by 24th week of conception A small part transforms into sphenomandibular and anterior malleolor ligaments Ventral end forms accessory endochondral ossicles Meckel’s cartilage dorsal to mental foramen gets resorbed on the lateral surface. Immediately lateral to resorbing cartilage,intramembranus bony trabeculae are being formed. www.indiandentalacademy.com


Fate of Meckel’s cartilage

Woven Woven bone bone 55thth month month

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


Fate of Meckel’s cartilage Coronoid cartilage

Condylar cartilage

10th & 14th week Sec. accessory cartilage

Angular cartilage Mental ossicle

www.indiandentalacademy.com


Secondary cartilage of coronoid process

Develop within temporalis muscle

Incorporated into intramembranus bone of ramus Disappear before birth

www.indiandentalacademy.com


 

Secondary cartilage at Mental region 1 or 2 small cartilage ossify mental ossicles(7th month) in fibrous tissue of symphysis It gets incorporated into intramembranous bone symphysis menti 1st postnatal year

synostosis syndesmosis 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


Types Of Ossification 

Mandible is the first bone to be ossified (6th week) There are two types of ossification :

INTRAMEMBRANOUS

ENDOCHONDRAL www.indiandentalacademy.com


Intramembranous bone formation Mesenchyme

Collagen fibre

Osteoblast

Osteoid matrix Calcium salts

Osteoblasts www.indiandentalacademy.com Bone lamella


Intramembranous bone formation

www.indiandentalacademy.com


Intramembranous bone formation

www.indiandentalacademy.com


Endochondral bone formation Mesenchymal cells

Hyaline cartilage Alkaline phosphatase

Primary areolae

Calcified Blood vessels

Secondary areolae

osteoid www.indiandentalacademy.com

Lamella of bone


Endochondral bone formation

www.indiandentalacademy.com


Endochondral bone formation

www.indiandentalacademy.com


ENDOCHONDRAL 

Cartilage template is replaced by endochondrial bone

INTRAMEMBRANOUS 

Direct deposition of osseous tissue in periosteal membrane

Indirect bone growth

Direct bone growt

Slow expansion

Rapid expansion

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


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


Neonatal mandible 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 

Mechanism of bone growth

Theories of growth

Anatomy www.indiandentalacademy.com


Mechanisms Of Bone Growth Growth Of The Mandible Primarily Involve

1. Bone remodeling 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


Theories of growth

www.indiandentalacademy.com


Theories of growth

www.indiandentalacademy.com


Other theories for growth 

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


Anatomy

www.indiandentalacademy.com


Growth timings 

The overall growth of mandible takes place at different stages. First there is increase in its  Width  Length  Height www.indiandentalacademy.com


Width 

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


Growth in length 

 

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

www.indiandentalacademy.com


Growth in height 

CONTINUES IN BOTH THE SEXES FOR A LONGER PERIOD GROWTH INCREASE OCCURS WITH CONCOMITANT ERUPTION OF TEETH AND CONTINUES TO INCREASE THROUGH OUT LIFE AND DECREASES IN ADULT LIFE

www.indiandentalacademy.com


Main sites of post natal growth in the Mandible 

Condylar cartilage

Posterior border of the Rami

Alveolar ridges

www.indiandentalacademy.com


Condylar cartilage Site of growth for ramus and body of mandible Dual function articular articular

growth growth Not a primary Centre of growth but rather site of growth 2° 2° in in evolution evolution 2° 2° in in embryonic embryonic origin origin 2°to 2°to adaptive adaptive changes changes www.indiandentalacademy.com


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

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

based mainly on animal experiments

www.indiandentalacademy.com


Age changes in mandible

www.indiandentalacademy.com


Ramus 

Moves progressively posterior by:POSTERIOR PART Deposition 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


Coronoid process ď Ž

Deposition on lingual side

ď Ž

Resorption on buccal surface

www.indiandentalacademy.com


Coronoid process ‘’V’ PRINCIPLE OF ENLOW

Lingual 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


Body of mandible

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 Ž

ď Ž

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

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 Ž

ď Ž

Forms by osseous deposition during childhood 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 

Protrusive chin is unique human trait

More prominent in male

Less prominent in female

www.indiandentalacademy.com


Symphysis Menti 

Limited growth till fusion

No widening after fusion www.indiandentalacademy.com


Mental Foramen

www.indiandentalacademy.com


Growth rotation ď Ž

The ramus undergoes remodeling rotation this produces displacement rotation as a whole

www.indiandentalacademy.com


Rotation is of two type ď Ž

Internal rotation Intramatrix

ď Ž

External rotation www.indiandentalacademy.com

Matrix


Growth rotation 

 

 

The rotation is considered forward if growth is more posteriorly than anteriorly. The rotation is considered backward if growth is more anteriorly than posteriorly. Short face -forward growth Long face -backward growth Males-slight forward growth Females-slight backward growth 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 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 www.indiandentalacademy.com


Age changes in mandible

www.indiandentalacademy.com


Radiographs of midsagital section’s of mandible Pre-extraction

High well-rounded

Post-extraction

www.indiandentalacademy.com


Knife edge

Low well rounded With out cortical layer on crest

Low well rounded with cortical layer on crest

www.indiandentalacademy.com


ANOMALIES OF MANDIBLE 

Syndromes associated with mandibular abnormality •Pierre-Robin’s syndrome •Treacher-collins syndrome

www.indiandentalacademy.com


Pierre-Robin’s syndrome

www.indiandentalacademy.com


Treacher-collins syndrome

www.indiandentalacademy.com


ANOMALIES OF MANDIBLE 

Congenital •Agnathia •Micrognathia •Macrognathia

www.indiandentalacademy.com


ANOMALIES OF MANDIBLE 

Developmental •Torus Mandibularis •Achondroplasia •Stafne’s cyst •Odontogenic cyst

www.indiandentalacademy.com


Torus mandibularis www.indiandentalacademy.com


Stafne’s cyst www.indiandentalacademy.com


REFERENCES 

Oral histology, development, structure and function – A.R. Ten Cate, 4th Edition The essentials of facial growth – Enlow and Hans, 1st Edition. Orthodontics principles and practice – Graber, 3rd edition Craniofacial Embryology- GH Sperber, 4th edition Textbook of oral pathology– William Shafer, 5th Edition www.indiandentalacademy.com


REFERENCES 



Orthodontics art and science-

Bhalajhi,3rd edition Human embryology- Inderbir singh,7th edition

www.indiandentalacademy.com


Thank you www.indiandentalacademy.com Leader in continuing dental education

www.indiandentalacademy.com


Growth and development of mandible kiran/ dental implant courses by Indian dental academy