Growth and Development of Mandible / orthodontic courses by Indian dental academy

GROWTH AND DEVELOPMENT OF MANDIBLE INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.com

INTRODUCTION

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


prenatal growth of mandible


PRENATAL GROWTH OF MANDIBLE


prenatal growth of mandible

°Nerve→osteogenesis(Neurotrophic factors)

Ectomesenchyme

interacts(36-38days iul)

Epi of 1st Arch

Osteogenic Memberanewww.indiandentalacademy.com

1 centre of ossification(6th week)

Inferior Alv Nerve Incisive branch

around below

Trough for acc dev Tooth buds


prenatal growth of mandible• spread of IM ossification

dorsally and ventrally →body and ramus of the mandible

presence of neuromuscular

bundle→Mandibular foramen and canal and mental foramen


Fate of Meckel`s cartilage



SECONDARY ACC CARTILAGES (10TH -14TH WEEK I U L)

-condylar cartilage

-coronoid cartilage

-Mental ossicle cartilage



• Secondary cartilage of coronoid process

• Develop within temporalis muscle

• Incorporated into IMB of ramus

• Disappear before birth



• 1/2 Cartilages

Mental ossicles

Intramembranous bonesyndesmosis

→ synostosis

Ossify (7th month of IUL)



• CONDYLAR CARTILAGE(10TH WEEK IUL)

• Grow interstitially and oppositionally


CONDYLAR CARTILAGE• 1ST Evidence of endochondral bone (14th week iul)

• Much of cartilage replaced with Bone by middle of fetal life

• Upper end →Growth cartilage and Articular cartilage

• Changes Mand position and form

• Growth ↑ at puberty peak b/n 12 ½ -14yrs

• Ceases →2o yrs of life


NEONATAL MANDIBLE

Ramus→Low & wide

coronoid→large & above the condyleBody→open shell containing tooth buds

Mand canal→low in the body


DIFFERENTIAL GROWTHDuring fetal life8weeks - MANDIBLE>

MAXILLA11weeks -MANDIBLE= MAXILLA13-20weeks-MAXILLA>MANDIBLE AT BIRTH

Mandible tends to be retrognathicEarly postnatal life -orthognathic


POST NATAL GROWTH & DEVELOPMENT OF

MANDIBLE


MECHANISMS OF GROWTH

Growth Of The Mandible Primarily Involve Bone remodeling Process Of Bone Deposition And Resorption Cortical drift Combination of bone deposition and resorption resulting

in growth movement towards deposition surface

Displacement Movement of whole bone as a unit I) Primary displacement II) Secondary displacement


THEORIES OF GROWTH

• GENETIC THEORY

Bone ̶ primary determinent

Cartilage̶ primary determinent

The soft tissue matrix www.indiandentalacademy.com

SUTURAL THEORY

• Craniofacial growth→sutures

• Suture transplanted

• Sutures pulled apart

• Sutures compressed

• Sutures are sites that react ̶ not primary dereminants


CARTILAGINOUS THEORY

• Growth of maxilla ̶ Nasalseptum cartilage• Transplantation Epiphyseal plate Nasalseptal cartilage Condylar cartilage

Removal of condyle


FUNCTIONAL MATRIX THEORY OF GROWTH

• Skeletal growth occur as a response to functional needs & mediated by the soft tissue in which it is embedded


ENLOW’S EXPANDING ‘V’ PRINCIPLE

The growth movement & enlargement of these Bones occur towards the wide ends of the ‘V’ as a result of differential deposition & selective resorption


ENLOW’S COUNTERPART PRINCIPLE

• The growth of any given facial /cranial part relates specifically to other structural & geometric ‘counterparts’ in the face & cranium

Diff parts & counter parts Maxillary & Mandibular arches Middle cranial fossa breadth of Ramus


Parts of Mandible derived From

1. INTRAMEMBRANOUS OSSIFICATION * Whole body of mandible except the anterior part * Ramus of mandible as far as mandibular foramen

2 . ENDOCHONDRAL OSSIFICATION * Anterior portion of the mandible (symphysis) * Part of ramus above the mandibular foramen * Coronoid process * Condylar process


Timing of growth

• Growth in width is completed 1st then growth in length finally growth in height


Growth in width

• Intercanine width does not ↑ much after 12yrs

• Both molar & bicondylar width show small ↑ until the end of growth in length

• Ant width stabilize earlier


Growth in length

• Continues through the period of puberty Girls – 14 -15 yrs Boys – 18 yrs


POST NATAL GROWTH OF MANDIBLE

• Mandible – Developmentally & Functionally divisible into skeletal subunits


• Mandible undergoes largest amt of growth postnatally and exhibits largest variability in morphology

• The main sites of postnatal growth

At condylar cartilages٭ Posterior border of rami ٭ Alveolar ridges٭


THE RAMUS

• Key role of ramus in placing the corpus &

dental arch into ever changing fit with growing maxilla & the faces limitless strl variations

• By Remodeling adjustments in Ramus length & Ant post width.


THE RAMUSRelocates postly Deposition posteriorly

Resorption anteriorly


LINGUAL TUBEROSITY• Direct Anatomic equivalent of Max tuberosity

• Inaccessible to cephalometric studies

• Major Growth & Remodeling site

• Effective boundary b/n Ramus & corps


LINGUAL TUBEROSITY• Deposition Postly & Medially• Resorption Below (Lingual fossa )


Lingual Tuberosity

Remodels in post direction with slight lateral shift

Lingual shift of Ant part of Ramus

↑ Length of corpus


Ramus to carpus Remodeling

• Making room last Molar


Ramus to carpus Remodeling

Growth direction fallows‘V’PRINCIPLE ‘X’ arrows

Remodeling activity does not occur onlyon ant & post barderwww.indiandentalacademy.com

Coronoid process• Propellar like twist• Lingual side faces posteriorly superiorly medially


Coronoid process

Fallows ‘V’ PRINCIPLE

‘V’ oriented vertically


Coronoid process

‘v’ PRINCIPLE

‘V’Oriented horizontally


Coronoid process Coronoid process → medially to become post part of carpus

Buccal side → Resorptive


Ramus

• Superior part of ramus the area below sigmoid

notch


Ramus


Antigonial notch

Size of the notch ↑ed – downward rotation Of carpus relative to the Ramus


The size of the notch depends upon Ramus – Carpus junction


Post edge Ramus is a major growth site

Condyle grows obliquely upward & backward

The angle of growth is variable

The gonial region is Anatomically variable


Mand Foramen – midway b/nAnt & post borders of Ramus


The Mandibular condyle

• Secondary cartilage

• not a primary center of growth, but rather * Secondary in Evolution * Secondary in Embryonic origin * Secondary in adaptive responses


condyle

• Cartilage is special nonvascular tissue

• firm matrix – unyielding to the pressure

• Endochondral growth mechanism


• Provides pressure tolerant articular contact

• Multidimensional growth capacity in response to ever changing developmental conditions & variations


• Capsular layer of poorly vascularised connective tissue –highly cellular

• Chondroblasts –cellular proliferation

• Chondroblasts – hypertrophy

• Zone of resorptive & Bone deposition


• Proliferative process produces upward & backward growth movement

• Multidirectional proliferative capacity- the arrangement of daughter cells does not reflect direction of growth


• The cortical layer of IMB continues on to the condylar neck

Ant margin of condylar neck – depository

grows supe’ly

post margin - depository grows on to post barder of ramus


• Lingual & Buccal sides - Resorptive


• V-shaped cone of condylar neck growing towards its wider end


• The condyle can’t play king pin role of “Master center” in pace-setting the growth Bilaterally condyle-lacking mand occupy

normal Anatomic position

Condylar remodeling acts with displacement as co-participants but not as driving force


Current concept• Condylar cartilage does have some intrinsic genetic

programming

• But extracondylar factors are needed to sustain this activity 1)Intrinsic & extrinsic biomechanical forces 2)physiologic inductors

ENLOW; ↑amt of pressure – inhibit the growth ↓ amt of pressure – stimulate the growth


• Mandible is less responsive to orthopedic forces than maxilla

• Mand orthopedics must modify growth signals targeted at both ramus & condyle to

be maximally effective


MENTAL FORAMEN


ALVEOLAR PROCESS

Adds ht & thickness to the body of the Mand

Teeth absent fails to develop

Resorbs after tooth extraction


Alveolar process

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

• Maintains vertical height

• Adaptive remodeling makes orthodontic tooth movement possible


Lingual movement of anteriors


Mental protuberance

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

Poorly developed in infants


Mental protuberance

Forms by osseous deposition during childhood

Prominence is accentuated by bone resorption above it

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


Factors Affecting GrowthSystemic Factors Genetic Hormonal imbalance Nutrition Systemic illness or chronic illness Localized alteration/ diseases of uterus Systemic illness in mother Drugs


1. Vascular abnormality2. Lymphatic disturbance3. Neurologic disease4. Local infection5. Ear infection or mastoiditis6. Ankylosis7. Trauma or fracture8. Birth injury9. Habits

B) Local factors


Anomalies of mandibleSome of the syndromes associated with

mandibular abnormality 1)Down’s syndrome 2)Marfan’s syndrome 3)Turners syndrome 4)Kleinfelter’s syndrome 5) Pierre-robin syndrome 6) Treacher- collin syndrome


Congenital• Agnathia• Micrognathia• Macrognathia• Facial hemihypertrophy• Facial hemiatropy


Developmental

• Infantile cortical hyperostosis

• Achondroplasia

• Torus mandibularis

• Stafne’s cyst

• Odontogenic cyst

• Odontogenic tumorwww.indiandentalacademy.com

Age changes of MandibleAt birth Adult Old age

1 Mental foramen

2 Angle of the mandible3 coronoid & condyloid processes

4 Mandibular canal

5 Symphysis menti

Near the lower border

Obtuse (180)

Coronoid is larger & above condyle

Runs little above the mylohyoid linePresent;two halves united fibrous tissue

Midway b/n upper & lower border

Right angle

Condyle is above the coronoid

Runs parallel to the mylohyoid line

Reprasented by faint ridge only in the upper part

Near the upper border

Obtuse (140)

Condyle is above the coronoid but in extreme old age –bent backwardsRuns close to the upper border

Not recognisable or absent


References

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


Thank you

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Growth and Development of Mandible / orthodontic courses by Indian dental academy

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Transcript of Growth and Development of Mandible / orthodontic courses by Indian dental academy