GROWTH AND DEVELOPMENT OF MANDIBLE
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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
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Prenatal Growth
It’s the most dynamic phase and is divided as
•Preimplantation period •Embryonic period •Fetal period
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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.
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th 4www.indiandentalacademy.com week
4 www.indiandentalacademy.com week embryo
Contents of each arch
Skeletal element Striated muscle Nerve Artery
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Internal view of pharyngeal floor and cut arches www.indiandentalacademy.com
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Mandibular Arch
Meckel’s cartilage Musculature Mandibular nerve Artery- maxillary and external carotid
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Meckel’s cartilage
41th- 45th day of I.U.L Provides a template Extends from Otic capsule –Midline or Symphysis
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Ossification of Meckel’s cartilage ď Ž
Mandibular division of trigrminal nerve
Neurotrophic factor
Osteogenesis
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Ossification of Meckel’s cartilage
In 6th week IU
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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
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Secondary cartilage of coronoid process
Develop within temporalis muscle
Incorporated into intramembranus bone of ramus Disappear before birth
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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
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Intramembranous bone formation
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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
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Endochondral bone formation
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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
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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
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Theories of growth
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Theories of growth
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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
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Anatomy
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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
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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
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Main sites of post natal growth in the Mandible
Condylar cartilage
Posterior border of the Rami
Alveolar ridges
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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
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Age changes in mandible
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Ramus
Moves progressively posterior by:POSTERIOR PART Deposition Resorption
ANTERIOR PART
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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
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Coronoid process ď Ž
Deposition on lingual side
ď Ž
Resorption on buccal surface
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Coronoid process ‘’V’ PRINCIPLE OF ENLOW
Lingual surface
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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
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Ramus corpus junction
Inferior Border of junction - resorption Forms Antegonial notch
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Antegonial notch Size depends upon ramus – corpus angle
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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
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Alveolar Process Lingual Lingual movement movement of of anteriors anteriors
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Mental Protuberance
Formed by mental ossicles from accessory cartilage and ventral end of Meckel’s cartilage Poorly developed in infants
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Mental Protuberance ď Ž
ď Ž
Forms by osseous deposition during childhood Prominence is accentuated by bone resorption above it
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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
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Symphysis Menti
Limited growth till fusion
No widening after fusion www.indiandentalacademy.com
Mental Foramen
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Growth rotation ď Ž
The ramus undergoes remodeling rotation this produces displacement rotation as a whole
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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
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Radiographs of midsagital section’s of mandible Pre-extraction
High well-rounded
Post-extraction
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Knife edge
Low well rounded With out cortical layer on crest
Low well rounded with cortical layer on crest
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ANOMALIES OF MANDIBLE
Syndromes associated with mandibular abnormality •Pierre-Robin’s syndrome •Treacher-collins syndrome
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Pierre-Robin’s syndrome
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Treacher-collins syndrome
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ANOMALIES OF MANDIBLE
Congenital •Agnathia •Micrognathia •Macrognathia
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ANOMALIES OF MANDIBLE
Developmental •Torus Mandibularis •Achondroplasia •Stafne’s cyst •Odontogenic cyst
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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 
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Orthodontics art and science-
Bhalajhi,3rd edition Human embryology- Inderbir singh,7th edition
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