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Prenatal and Postnatal Growth of Midface

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CONTENTS 

Anatomy of Midface and associated structures.

Prenatal embryology

Origin of malformations

Post natal Development

Theories of growth www.indiandentalacademy.com


ANATOMY OF MAXILLA AND ASSOCIATED STRUCTURES. ď Ž

Consists of 5 parts 1. Body 2. Zygomatic 3. Frontal 4. Alveolar 5. Palatine process

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BODY OF THE MAXILLA ď Ž

Four parts 1. Anterior 2. Infra temporal 3. Orbital 4. Nasal

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ZYGOMATIC PROCESS    

Anterior Posterior Superior Inferior

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FRONTAL PROCESS     

Lateral Medial Superior border Anterior border Posterior border

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ALVEOLAR PROCESS

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PALTINE PROCESS    

Superior Inferior Lateral Medial

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MAXILLARY SINUS   

Largest sinus Pyramidal in shape 4 walls Apex Base Roof Floor www.indiandentalacademy.com


PALATINE BONE 

2 plates Horizontal Perpendicular 3 process Pyramidal Orbital Sphenoidal www.indiandentalacademy.com


NASAL BONE 

2 surfaces External Internal 4 borders Superior Inferior Lateral Medial

R

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L


LACRIMAL BONE 

2 surfaces Lateral Medial 4 borders Anterior Posterior Superior Inferior www.indiandentalacademy.com


ETHMOID BONE ď Ž

3 parts Cribriform plates Perpendicular plate Ethmoidal labyrinths

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VOMER BONE •Midline structure •2 surface- lateral •4 borders Anterior Posterior Superior Inferior www.indiandentalacademy.com


ZYGOMATIC BONE  

Quadrangular in shape Parts 3 surfaces 5 borders 2 process

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Nasal cavity

Lateral wall Medial wall

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Nasal Cartilages

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Prenatal Embryology

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Outline      

Formation of Branchial Arches Development of Lip Development of palatal shelves Development of maxillary complex Sagittal and transverse Growth of Nasomaxillary complex Midface before birth – Changes in the facial propotions www.indiandentalacademy.com


Formation of Branchial Arches 

1- 4 weeks – Ovum

Zygote

Blastocyst

Gastrula

Neurulation

4- 5 weeks – Formation of 6 arches Face develops from 1 and 2 branchial arches

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Origins of mid face at 5 weeks 

  

Appearance of nasal pits by thickening of the ectoderm ( ecto – ectodermal interactions) Forward and downward growth of the face Formation of medial and lateral nasal process Migration of neural crest cells

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Face at 6 – 8 weeks  

Change In the optical axes Fusion of the medial nasal processes and maxillary process giving rise to – Lip Philtrum Primary palate Fusion of the facial primordias www.indiandentalacademy.com


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Development of Lip ď Ž ď Ž

Occurs during the 5th week during the fusion of maxillary and medial nasal process. Occurs in 3 stages 1. Contact of the epithelia 2. Fusion of the epithelial process 3. Invasion of the connective tissues

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Development of the palate  

5 weeks – palatine process of the maxilla Separated by the tongue

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 

6 weeks – growth of the palatine shelves caudally 7 weeks – descend of the tongue caudally.

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Elevation of the palate  

Region specific synthesis and accumulation of the hyaluronan It binds with water by more than 1000 times of its own weight causing swelling and expansion of the shelves Alignment of the collagen fibrils and the cells of the mesenchyme (contraction)

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   

The process occurs when there is maximum growth of the height of the head Length of the meckels cartilage Maxillary cranial base angle – 84 deg Fusion occurs late in females - 7 days

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Woo 1949– Separate center of ossification for each premaxilla and maxillary centers of ossification near the canine fosse Two centers on either side have fused to form the corpus There is no longer any morphologically separate premaxilla at the end of 8th week

Bertram Kraus (J. D. Res. 1960) – 7 morphological levels www.indiandentalacademy.com


The 7 Stages

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1st stage 

Fusion of Premaxilla and maxilla

Radiation of the trabecule from the future canine alveolus

K-shaped configuration

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1st stage

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2nd stage – 9 weeks 

Begins with ossification of the alveolar crypts of the central and lateral incisors.

Thin trabecularized network of bone of the palate

Vomer bones have appeared www.indiandentalacademy.com


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3rd stage – 10 weeks   

Appearance of the infravomerine processes Separate centers and fuse quickly Appearance of various bony trabeculae for the formation of the palate and the palatine bone Formation of the first primary molar

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4th stage – 11 weeks  

Increase in depth of alveolar sockets A pointed bony process midway on the lingual alveolar border of the central and lateral incisors Anterior bony margin of the incisive suture

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5th stage - 13 weeks ď Ž

ď Ž

Left and right palatal processes of the maxilla and palatine bones have reached almost to the mid-line and have achieved their maximum overlap. Divided into three zones Anterior - deeply stained trabeculae of the maxilla Middle - superior layer of palatine bone and an inferior layer of maxillary bone Posterior - horizontal trabeculae of the palatine bone www.indiandentalacademy.com


Buccal alveolar borders of the incisors, canine, and primary first molar have now assumed their characteristically curved shape Posterior portion of the medial edge of palate is rounded – absence of PNS

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6th stage - 14 weeks ď Ž

ď Ž

Two halves of the palatal processes are in apposition. at the mid-line, although no fusion has taken place and the two processes are generally not in contact. Formation of Posterior nasal spine

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7th stage – 15 week

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Development of the maxillary complex

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Sagittal and transverse Growth of Nasomaxillary complex from 12 – 24 weeks 

Alphonse Burdi ; J. Dent. Res. 1965

Landmarks – Nasion (N) Sella (S) Basion (Ba) Crista galli (CG) Septal point (SP) Anterior nasal spine (ANS) Posterior nasal spine Uvular point (UP).

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Transverse growth 

Palatal Breadth To Palatal Length:

The mean value is around 82 per cent for adults. In fetuses this relationship begins with 167 per cent and decreases to 125 per cent. This decrease is achieved by a constantly increasing rate of acceleration of palatal length relative to that of palatal breadth.

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Midface before birth – Changes in the facial propotions CHANGES FROM 12TH – 36 WEEKS  Length – 18mm > 120mm  Width – 12mm > 74 mm  Height – 20 mm > 100mm

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 

Prior to the 5th month the increase in height is the greatest Cranial vault : face > 40 : 1- embryo > 5 : 1 – 4 months > 8: 1 – birth > 2 : 1 - adult

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“ And

the end of all our exploring Will be to arrive where we started And know the place for the first time�

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