GROWTH AND DEVELOPMENT OF MANDIBLE INDIAN DENTAL ACADEMY
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INTRODUCTION
âThe 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.â
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prenatal growth of mandible
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PRENATAL GROWTH OF MANDIBLE
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prenatal growth of mandible
°Nerveâosteogenesis(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
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prenatal growth of mandible⢠spread of IM ossification
dorsally and ventrally âbody and ramus of the mandible
presence of neuromuscular
bundleâMandibular foramen and canal and mental foramen
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Fate of Meckel`s cartilage
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PRENATAL GROWTH OF MANDIBLE
SECONDARY ACC CARTILAGES (10TH -14TH WEEK I U L)
-condylar cartilage
-coronoid cartilage
-Mental ossicle cartilage
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PRENATAL GROWTH OF MANDIBLE
⢠Secondary cartilage of coronoid process
⢠Develop within temporalis muscle
⢠Incorporated into IMB of ramus
⢠Disappear before birth
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PRENATAL GROWTH OF MANDIBLE
⢠1/2 Cartilages
Mental ossicles
Intramembranous bonesyndesmosis
â synostosis
Ossify (7th month of IUL)
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PRENATAL GROWTH OF MANDIBLE
⢠CONDYLAR CARTILAGE(10TH WEEK IUL)
⢠Grow interstitially and oppositionally
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CONDYLAR CARTILAGE⢠1ST Evidence of endochondral bone (14th week iul)
⢠Much of cartilage replaced with Bone by middle of fetal life
⢠Upper end âGrowth cartilage and Articular cartilage
⢠Changes Mand position and form
⢠Growth â at puberty peak b/n 12 ½ -14yrs
⢠Ceases â2o yrs of life
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NEONATAL MANDIBLE
RamusâLow & wide
coronoidâlarge & above the condyleBodyâopen shell containing tooth buds
Mand canalâlow in the body
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DIFFERENTIAL GROWTHDuring fetal life8weeks - MANDIBLE>
MAXILLA11weeks -MANDIBLE= MAXILLA13-20weeks-MAXILLA>MANDIBLE AT BIRTH
Mandible tends to be retrognathicEarly postnatal life -orthognathic
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POST NATAL GROWTH & DEVELOPMENT OF
MANDIBLE
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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
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THEORIES OF GROWTH
⢠GENETIC THEORY
Bone Ěś primary determinent
CartilageĚś primary determinent
The soft tissue matrix www.indiandentalacademy.com
SUTURAL THEORY
⢠Craniofacial growthâsutures
⢠Suture transplanted
⢠Sutures pulled apart
⢠Sutures compressed
⢠Sutures are sites that react ̜ not primary dereminants
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CARTILAGINOUS THEORY
⢠Growth of maxilla ̜ Nasalseptum cartilage⢠Transplantation Epiphyseal plate Nasalseptal cartilage Condylar cartilage
Removal of condyle
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FUNCTIONAL MATRIX THEORY OF GROWTH
⢠Skeletal growth occur as a response to functional needs & mediated by the soft tissue in which it is embedded
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ENLOWâS EXPANDING âVâ PRINCIPLE
The growth movement & enlargement of these Bones occur towards the wide ends of the âVâ as a result of differential deposition & selective resorption
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ENLOWâS COUNTERPART PRINCIPLE
⢠The growth of any given facial /cranial part relates specifically to other structural & geometric âcounterpartsâ in the face & cranium
Diff parts & counter parts Maxillary & Mandibular arches Middle cranial fossa breadth of Ramus
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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
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Timing of growth
⢠Growth in width is completed 1st then growth in length finally growth in height
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Growth in width
⢠Intercanine width does not â much after 12yrs
⢠Both molar & bicondylar width show small â until the end of growth in length
⢠Ant width stabilize earlier
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Growth in length
⢠Continues through the period of puberty Girls â 14 -15 yrs Boys â 18 yrs
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POST NATAL GROWTH OF MANDIBLE
⢠Mandible â Developmentally & Functionally divisible into skeletal subunits
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⢠Mandible undergoes largest amt of growth postnatally and exhibits largest variability in morphology
⢠The main sites of postnatal growth
At condylar cartilagesŮ Posterior border of rami Ů Alveolar ridgesŮ
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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.
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THE RAMUSRelocates postly Deposition posteriorly
Resorption anteriorly
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LINGUAL TUBEROSITY⢠Direct Anatomic equivalent of Max tuberosity
⢠Inaccessible to cephalometric studies
⢠Major Growth & Remodeling site
⢠Effective boundary b/n Ramus & corps
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LINGUAL TUBEROSITY⢠Deposition Postly & Medially⢠Resorption Below (Lingual fossa )
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Lingual Tuberosity
Remodels in post direction with slight lateral shift
Lingual shift of Ant part of Ramus
â Length of corpus
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Ramus to carpus Remodeling
⢠Making room last Molar
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Ramus to carpus Remodeling
Growth direction fallowsâVâPRINCIPLE âXâ arrows
Remodeling activity does not occur onlyon ant & post barderwww.indiandentalacademy.com
Coronoid process⢠Propellar like twist⢠Lingual side faces posteriorly superiorly medially
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Coronoid process
Fallows âVâ PRINCIPLE
âVâ oriented vertically
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Coronoid process
âvâ PRINCIPLE
âVâOriented horizontally
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Coronoid process Coronoid process â medially to become post part of carpus
Buccal side â Resorptive
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Ramus
⢠Superior part of ramus the area below sigmoid
notch
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Ramus
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Antigonial notch
Size of the notch âed â downward rotation Of carpus relative to the Ramus
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The size of the notch depends upon Ramus â Carpus junction
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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
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Mand Foramen â midway b/nAnt & post borders of Ramus
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The Mandibular condyle
⢠Secondary cartilage
⢠not a primary center of growth, but rather * Secondary in Evolution * Secondary in Embryonic origin * Secondary in adaptive responses
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condyle
⢠Cartilage is special nonvascular tissue
⢠firm matrix â unyielding to the pressure
⢠Endochondral growth mechanism
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⢠Provides pressure tolerant articular contact
⢠Multidimensional growth capacity in response to ever changing developmental conditions & variations
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⢠Capsular layer of poorly vascularised connective tissue âhighly cellular
⢠Chondroblasts âcellular proliferation
⢠Chondroblasts â hypertrophy
⢠Zone of resorptive & Bone deposition
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⢠Proliferative process produces upward & backward growth movement
⢠Multidirectional proliferative capacity- the arrangement of daughter cells does not reflect direction of growth
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⢠The cortical layer of IMB continues on to the condylar neck
Ant margin of condylar neck â depository
grows supeâly
post margin - depository grows on to post barder of ramus
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⢠Lingual & Buccal sides - Resorptive
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⢠V-shaped cone of condylar neck growing towards its wider end
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⢠The condyle canât play king pin role of âMaster centerâ 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
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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; âamt of pressure â inhibit the growth â amt of pressure â stimulate the growth
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⢠Mandible is less responsive to orthopedic forces than maxilla
⢠Mand orthopedics must modify growth signals targeted at both ramus & condyle to
be maximally effective
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MENTAL FORAMEN
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ALVEOLAR PROCESS
Adds ht & thickness to the body of the Mand
Teeth absent fails to develop
Resorbs after tooth extraction
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Alveolar process
⢠Maintain occlusal relationship during differential mandibular & midfacial growthâ buffer zones
⢠Maintains vertical height
⢠Adaptive remodeling makes orthodontic tooth movement possible
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Lingual movement of anteriors
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Mental protuberance
Formed by mental ossicles from accessory cartilage and ventral end of Meckelâs cartilage
Poorly developed in infants
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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
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Factors Affecting GrowthSystemic Factors Genetic Hormonal imbalance Nutrition Systemic illness or chronic illness Localized alteration/ diseases of uterus Systemic illness in mother Drugs
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1. Vascular abnormality2. Lymphatic disturbance3. Neurologic disease4. Local infection5. Ear infection or mastoiditis6. Ankylosis7. Trauma or fracture8. Birth injury9. Habits
B) Local factors
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Anomalies of mandibleSome of the syndromes associated with
mandibular abnormality 1)Downâs syndrome 2)Marfanâs syndrome 3)Turners syndrome 4)Kleinfelterâs syndrome 5) Pierre-robin syndrome 6) Treacher- collin syndrome
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Congenital⢠Agnathia⢠Micrognathia⢠Macrognathia⢠Facial hemihypertrophy⢠Facial hemiatropy
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Developmental
⢠Infantile cortical hyperostosis
⢠Achondroplasia
⢠Torus mandibularis
⢠Stafneâs 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 âbent backwardsRuns close to the upper border
Not recognisable or absent
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References
* Craniofacial embryology â SPERBER * Facial growth â ENLOW * Contemporary orthodontics â PROFFIT * Handbook of orthodontics â MOYERS * Principles and practice of orthodontics âGRABER
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