GROWTH OF MAXILLA AND CRANIAL BASE AND THEIR CLINICAL IMPLICATIONS
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CONTENTS • • • • • • • •
INTRODUCTION PRENATAL GROWTH OF MAXILLA POSTNATAL GROWTH OF MAXILLA PRENATAL GROWTH OF CRANIAL BASE POSTNATAL GROWTH OF CRANIAL BASE CLINICAL CONSIDERATIONS CONCLUSIONS REFERENCES www.indiandentalacademy.com
INTRODUCTION • Orthodontists are heavily involved in the development of not just the dentition but the entire dentofacial complex, a conscientious practitioner may be able to manipulate facial growth for the benefit of the patient. • This is not possible to accomplish without thorough understanding of the pattern of normal growth and the mechanisms that underlie it , hence it is essential to study growth. www.indiandentalacademy.com
WHAT IS GROWTH? • Growth is physiochemical process of living matter by which organism becomes larger
• Quantitative aspect of biologic development per unit time :moyers
• Increase in size, change in proportion & progressive complexity: krogman
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MAXILLA
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MAXILLA • The maxilla is the second largest bone of the facial skeleton, the first being the mandible. It is a pneumatic bone that is paired and forms the upper jaw. • Either of a pair of irregularly shaped bones of the skull, fusing in the midline, supporting the upper teeth, and forming part of the eye sockets, hard palate, and nasal cavity; upper jaw. www.indiandentalacademy.com
Parts of maxilla The body of the maxilla has four surfaces: • Anterior or facial surface • Posterior or infratemporal surface • Superior or orbital surface • Medial or nasal surface. • Maxillary sinus is present within the body It has four processes: • Frontal • Zygomatic • Alveolar • Palatine. www.indiandentalacademy.com
Articulations • Two of the cranium: the frontal and ethmoid • Seven of the face: the nasal, zygomatic, lacrimal, inferior nasal concha, palatine, vomer, and the adjacent fused maxillary bone. • Sometimes it articulates with the orbital surface, and sometimes with the lateral pterygoid plate of the sphenoid.
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PRENATAL GROWTH OF MAXILLA
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Around 4th week of intra uterine life five branchial arches form in the region of future head and neck. The first branchial arch called the mandibular arch plays an important role in nasomaxillary complex development www.indiandentalacademy.com
Maxilla develops from: • Frontonasal process :mesoderm covering the forebrain which proliferates and forms a downward projection overlapping upper part of stomodeum. • Maxillary processes: mandibular arches give bud from its dorsal end called maxillary processes www.indiandentalacademy.com
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The two maxillary processes grow ventro medially and fuse with frontonasal process to give rise to maxilla. The anterior part of the maxilla and part of the nose develop from the frontonasal process. At the end of 3rd week of intra-uterine life, this process grows downwards to meet the maxillary processes of the first branchial arch, which grow forward. These processes unite at the end of the 4th week I.U. to form the maxillary jaw. www.indiandentalacademy.com
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Ossification of maxilla • The maxilla is ossified in membrane(intramemranous). It is ossified from two centers only, one for the maxilla proper and one for the premaxilla.
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• At 6 ½ weeks I.U., the future body of the maxilla constitutes the main mass and its frontal, zygomatic, alveolar and palatal processes. • In the 7 ½ week I.U., the lamella begins to grow forward, backward and downward to form the frontal process and alveolar wall. • After the 3rd month I.U., there is generalized enlargement of the face in all directions. www.indiandentalacademy.com
Âť The maxillary sinus appears as a shallow groove on the nasal surface of the bone about the fourth month of fetal life, but does not reach its full size until after the second dentition.
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Development of palate Palate develops from : • Maxillary process • Palatal shelves of maxillary process • Frontonasal process
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Development of the bony palate. • Frontonasal process gives rise to premaxilla while palatal shelves form the rest of the palate. • Initially the palatal shelves grow vertically downwards towards the floor of the mouth sometime during 7th week of intra uterine life they change to horizontal position. • By 8 ½ weeks of intra uterine life the palatal shelves begin to fuse. www.indiandentalacademy.com
• At 9 weeks, the shelves are in near contact and the premaxillary – maxillary ossification centers appear. • At 10 weeks, the soft tissue of the palate has fused and ossification centers of the premaxilla – maxilla grow medially.
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Palate ossifies from single centre. The anterior part of the palate undergoes intra membranous type of ossification . Posterior palate doesnot ossify – forms soft palate. At 14 weeks, the premaxillary bone supports the incisors and the maxillary bone supports the cuspids and first molars.The palatine bone supports the second molars. www.indiandentalacademy.com
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Mid palatal suture Ossifies by 12 to 14 years Mid palatal suture • 10 1/2 weeks-fibrous layer in the midline. • infancy Y shape in coronal section •childhood - T shape •adolescence - Interdigitated www.indiandentalacademy.com
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POST NATAL GROWTH OF MAXILLA
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Growth of maxilla involves mainly of these processes which occur simultaneously and in an interdependent way. •
Remodelling which occurs in posterior direction.
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Apposition of bone at sutures
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Displacement which moves the maxilla forward and downward. www.indiandentalacademy.com
• Hypothesis OF GROWTH OF MAXILLA • Additions of new bone on the posterior surface of the elongating maxillary tuberosity "push" the maxilla against the adjacent muscle supported pterygoid plates. This presumably would cause a resultant shove of the entire maxilla anteriorly because of its own posterior bone growth activity. • Reason for aborting this theory was that bones osteogenic membrane is pressure sensitive hence tissue necrosis will occur in case of pressure www.indiandentalacademy.com
Sutural theory • Growth at sutures pushes apart bones with resultant thrust of whole maxilla anteriorly • Sutural connective tissue is not adapted to a pressure related growth process,sutures are tension adapted tissues hence this idea was also aborted.
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Nasal septum theory: scott • Basis of the “septal theory” is that pressure accomodating expansion of the cartilage in the nasal septum provides a source for the physical force that displaces the whole maxilla anteriorly and inferiorly,setting up fields of tension in maxillary sutures which enlarge in response to the tension created by displacement process. • There is no actual genetic determinants within the septal cartilage (blueprint for growth of
maxilla)
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Black : bone Stippled:cartilage
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• "Multiple assurance" (Latham and Scott, 1970). • The processes and mechanisms that " function to carry out growth are virtually always multifactorial. Any one determinant of the growth process become inoperative (as by pathology or by experimental deletion of an anatomic part), other morphologic components in some instances have the capacity to "compensate." • That is, they provide an alternative means to achieve more or less the same developmental and functional end result, although perhaps with some degree of anatomic distortion. www.indiandentalacademy.com
Functional matrix theory :Melvin moss ďƒź This theory states that :origin form position growth and maintenance of all skeletal tissue and organs are always secondary compensatory and necessary response to chronological and morphological prior events or processes that occur in specifically related nonskeletal tissue organs or funtioning spaces www.indiandentalacademy.com
• Melvin Moss (AJODO1969) has described two basic types of matrices are there: periosteal and capsular. • Periosteal matrices act upon skeletal units in a direct fashion by the process of osseous deposition and resorption ,their net effect is to alter the form of their respective skeletal units. • Capsular matrices act upon functional cranial components as a whole in a secondary and indirect manner by altering the volumes of the capsular matrices within which they are embedded . • The effect of such growth is to cause a passive translation of these cranial components in space. www.indiandentalacademy.com
ď śCalvarial
bones are embedded in neuro cranial capsule and are translated thereby ,so are the nasomaxillary bones embedded in the orofacial capsule . The primary expansion of the functioning oronasopharyngeal spaces on a morphogenetic stimulus brings about secondary compensatory expansion of the orofacial capsule. www.indiandentalacademy.com
Servosystem theory :petrovic • STH-somatomedin, testosterone and estrogen play primary roles in extrinsic control of post natal growth of the upper jaw. • They have direct and indirect effects.
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Direct effects • Represents almost the entire influence of the hormones on growth of spheno-occipital synchondrosis and nasal septal cartilage. • Small part of the effect of hormones on growth of cranial sutures is direct. Effects the responsiveness of preosteoblasts to regional and local factors, stimulating the skeletal cell multiplication.
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Indirect effect • Forward growth of nasal septal cartilage. 1.Thrust effect 2.Septomaxillary ligament traction effect. 3.Labionarinary muscle traction effect.
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Thrust effect ď Ž growth of septal cartilage-thrust on premaxilla-stimulates growth of premaxillomaxillary suture and maxillopalatal suture.
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Septopremaxillary ligament traction effect • Forward growth of nasal septal cartilage has a traction effect on the premaxillary bone through the septo premaxillary ligament.
Labionarinary muscle traction effect• Septal cartilage growth produces traction on premaxilla through this muscle causing forward growth of upper jaw. www.indiandentalacademy.com
Growth of maxilla : amount and direction
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Maxillary height • The classical studies by Bjork and skieller confirm that maxillary height increases because of sutural growth toward the frontal and zygomatic bones and appositional growth in the alveolar process. • Apposition also occurs on the floor of the orbits with resorptive modeling of the lower surfaces,simultaneously the nasal floor is resorped while apposition occurs on the hard palate. www.indiandentalacademy.com
Maxillary width • Growth in the median suture is most important for increase in maxillary width. • Growth increase in median suture follows general growth curve for body height. • Mutual transverse rotation of the two maxillae results in separation of the halves more posteriorly than anteriorly
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Maxillary length • Length increases in the maxilla after about the second year by apposition on the maxillary tuberosity and by sutural growth toward the palatine bone.Surface resorption occurs anteriorly • The maxilla rotates forward in the relation to anterior cranial base.
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Extensive remodeling occurs throughout the nasomaxillary complex (B and C) as the entire region un-dergoes inferior (and anterior) www.indiandentalacademy.com displacement (D).
Enlow & Bang (AJO 1965) studied the
complete right halves of the maxillary bones from twelve well-preserved human skulls, all with either deciduous or mixed dentition.
Due to the complex shape and contours of the maxilla, the entire bone was divided into several sections and the growth of each part was studied individually.
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The Maxillary Tuberosity • Maxilla grows horizontally by remodelling of maxillary tuberosity.Deposition occurs on the posterior facing periosteal surface of the tuberosity,endosteal surface is resorptive. Cortex moves posteriorly and little www.indiandentalacademy.com laterally.
Maxillary tuberosity is major GROWTH SITE of maxilla in posterior region. Primary displacement of maxilla occurs due to deposition at tuberosity. The amount of forward movement is equal and opposite to the posterior lengthening . This functions to lengthen the dental arch and to enlarge the anterioposterior dimensions of the entire maxillary body.
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Growth proceeds along the entire inner side of the arch as well as along its posterior margin,resorptive removal occurs from the outer cortex of the premaxillary area and anterior surface of zygomatic process. Apparent direction of growth which results from www.indiandentalacademy.com anterior thrust of the maxillary body
The whole maxilla undergoes a simultaneous process of primary displacement in an anterior and inferior direction as it grows and lengthens posteriorly & superiorly. www.indiandentalacademy.com
The malar process of maxilla •
Coordinated with tuberosity growth is the movement of entire zygomatic process in posterior direction.The posterior side of the malar protuberance within the temporal fossa is depository. Together with a resorptive anterior surface, the cheekbone relocates posteriorly as it enlarges.
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The zygoma becomes displaced anteriorly and inferiorly in the same direction and amount as that of maxilla ,malar protuberance is a part of maxilla and is carried with it www.indiandentalacademy.com
• As the malar region grows and becomes relocated posteriorly, the contiguous nasal region is enlarging in an opposite, anterior direction. This draws out and greatly expands the contour between them, resulting in a progressively more protrusive appearing nose and an anteroposteriorly much deeper face. • This is a major topographic maturational change in the childhood-to-adult face. i.e the depth of the face increases. www.indiandentalacademy.com
Growth of zygomatic bone and malar process of maxilla :posterior surface depository anterior www.indiandentalacademy.com resorptive.
The Nasal Region • The nasal area of the maxilla together with its separate nasal bones ,also faces in similar lateral,anterior and superior directions. • Growth proceeds in these directions by surface bone deposition ,thereby increasing the internal size of nasal cavity by an elongation and expansion of its vertical and horizontal dimensions.
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• The bony cortex lining the inner surface of the nasal cavity undergoes periosteal surface removal of bone as its endosteal surface receives simultaneous deposits of new bone. • Bone is removed from floor of nasal cavity and a compensatory bone deposition occurs on the palatal side. www.indiandentalacademy.com
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The breadth of the nasal bridge in the region just below the frontonasal sutures does not markedly increase from early childhood to adulthood . More inferiorly in the interorbital area, however, the medial wall of each orbit expands and balloons out considerably in a lateral direction in conjunction with the considerable extent of lateral enlargement www.indiandentalacademy.com of the nasal chambers.
The Maxillary Sinus • The inner cortical lining of the sinus is resorptive in nature. • This contributes to enlargement of the sinus during maxillary growth by resorption from the inside and regional deposition on the various outer surfaces.
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Palatine process of maxilla • Grows in a generally downward direction by a combination of surface deposition on the entire oral side of the palatal cortex with resorptive removal from the opposite nasal side,as well as from periosteal labial surfaces of the anterior maxillary arch. • It follows the V principle of growth and hence grows inferiorly by remodelling and expands laterally www.indiandentalacademy.com
The growth of palate by the V principle www.indiandentalacademy.com
Premaxilla • The premaxillary part of the maxilla grows in a downward direction. The surface orientation of this area is such that downward movement is brought about by resorptive removal from the periosteal surface of the labial cortex which faces away from the direction of growth. The endosteal side of its cortex and the periosteal surface of the lingual cortex receive new bone deposits. This growth pattern also produces a slight recession of the incisor area in a posterior direction.
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Orbital surface of maxilla • Orbit also follows the growth by v principle • Sutural bone growth occurs at the many sutures within and outside the orbit, the orbital floor is displaced and enlarges in a progressive downward and forward direction along with the rest of the nasomaxillary complex.
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• The floor of the orbit offsets this by remodeling upward as the whole maxilla displaces inferiorly. Deposition takes place on the intraorbital (superior) side of the orbital floor and resorption on the maxillary (inferior) sinus side . • This sustains the orbital floor in proper position with respect to the eyeball above it. • The nasal floor, in contrast, approximately doubles the amount of displacement movement by additional downward cortical remodeling. • Thus, the orbital and nasal floors are necessarily displaced in the same direction because they are; parts of the same bone, but they undergo remodeling relocation movements in opposing directions. www.indiandentalacademy.com
The floor of the nasal cavity in the adult is positioned much lower than the floor of the orbital cavity www.indiandentalacademy.com
The orbits relocates anteriorly by the V principle ,which itself serves to enlarge the orbital size Also, the multiple parts of the whole orbit become displaced out and away from each other at the same time in association with bone deposition at the various orbital sutures www.indiandentalacademy.com
Alveolar part of maxilla • Deposition occurs on the alveolar part of maxilla as teeth begin to erupt • Following eruption, teeth undergo a process of vertical drift in which the whole socket remodells in downward direction along with the tooth :intra memranous remodelling
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Vertical remodelling of socket
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• The horizontal and, especially, the vertical distances moved by the socket, its tooth, and the periodontal membrane can be substantial. By harnessing the vertical drift movement, the orthodontist can more readily guide teeth into calculated positions, thereby taking advantage of the growth process ("working with growth"). www.indiandentalacademy.com
vertical drift of each tooth in its own alveolar socket passive carrying of the maxillary dental arch
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The Key Ridge • Major changes occur in surface contour along the vertical crest just below the malar protruberance :key ridge.A reversal occurs here Area (b) anterior to the reversal line the external surface of maxilla is resorptive Area (a) grows downward by periosteal deposition www.indiandentalacademy.com
Surface a is resorptive b is depository.arrow indicates the area of reversal used as point A in cephalometrics www.indiandentalacademy.com
Lacrimal suture :key factor for maxillary growth • The lacrimal bone is a diminutive flake of a bony island with its entire perimeter bounded by sutural connective tissue contacts separating it from the many other surrounding bones. • As all these other separate bones enlarge or become displaced in many directions and at different rates and different times, the sutural system of the lacrimal bone provides for the "slippage" of the multiple bones along sutural interfaces with the pivotal lacrimal as they all enlarge differentially. This is made possible by collagenous linkage adjustments
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• The lacrimal sutures make it possible, for the maxilla to "slide" downward along its orbital contacts. This allows the whole maxilla to become displaced inferiorly, a key midfacial growth event, even though all the other bones of the orbit and nasal region develop quite differently and at different times, amounts, and directions. • Without this adjustive developmental "perilacrimal sutural system," a developmental "gridlock� would occur among the multiple developing parts. The lacrimal bone and its suture is a developmental hub providing key traffic controls.
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• The growing child's facial topographic profile undergoes a characteristic clockwise rotation. Several developmental relationships underlie the maturational change • The two-way combination of (1) forward remodeling of the nasal region and superior orbital rim together with (2) backward remodeling growth of the inferior orbital rim and the malar area, and (3) the essentially straight downward remodeling of the premaxillary region, all combine to produce a developmental rotation in the alignment of the whole www.indiandentalacademy.com of these middle and upper facial regions
Facial topographic profile undergoes a www.indiandentalacademy.com characteristic clockwise rotation.
Sutural growth of maxilla • New bone is added at the frontomaxillary, zygotemporal, zygosphenoidal, zygomaxillary, ethmo maxillary, ethmofrontal, nasomaxillary, naso-frontal, frontolacrimal, palatine, and vomerine sutures. • The displacement of the bone is caused by the expanding soft tissues ,sutural growth occurs as a response to it ….multiple sutural deposits are not the pacemaker of growth. www.indiandentalacademy.com
• The suture are all oblique and more or less parallel to each other . This allows downward and forward repositioning of maxilla as growth occurs. www.indiandentalacademy.com
As the whole maxillary complex is displaced downward and forward, or as it remodels by deposition and resorption, it undergoes a frontal slide at sutural junctions with the lacrimal, zygomatic, nasal, and ethmoidal bones. ďƒ˜
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Summary diagram of maxillary remodeling. Growth directions involving surface resorption are represented by arrows entering the bone surface. Directions of growth in-volving surface deposition are shown by arrows emerging from the bone surface.
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3 dimensional growth of the maxilla as revealed by the implant method Arne Bjork and V. Skieller (BJO 1977),
described the growth of the maxilla studied by the implant method with the help of lateral and PA cephalograms, in nine 4 year old boys with normal primary occlusion who were followed annually up to the age of 21 years.
The tantalum pins inserted in the zygomatic process of the maxilla at 4 years of age were referred to as the lateral implants. The implants placed in the anterior aspect of the maxilla after full eruption of permanent incisors (10-11yrs) were referred to as anterior implants. www.indiandentalacademy.com
Maxillary width • Bjork showed that growth in the suture continues until puberty. • By measuring the distance of separation between the lateral implants on the frontal cephalogram over time, it was shown that sutural growth was the most important factor in the development of the width of the maxilla. • The mean transverse growth in the median suture, measured between the lateral implants, from childhood to adulthood was 6.9mm. • The curves for cumulative growth in the width of the median suture from year to year followed the same pattern as the curves for the growth in body height. www.indiandentalacademy.com
Transverse mutual rotation of the two maxillae: • Comparison of increase in width between the anterior and the lateral implants showed that increase in width between the lateral implants was on average, 3.5 times greater than that between the anterior implants.(3 mm and 0.9 mm respectively). • This indicates that the two maxillae rotate in relation to one another in the transverse plane, which results in decreased length of the maxilla in the mid sagittal plane. www.indiandentalacademy.com
• Mutual transverse rotation of maxillae also results in greater separation of lateral segments of dental arch posteriorly, than anteriorly. • There is thus, greater increase in intermolar width than intercanine width, and also a corresponding decrease in arch length. • Thus, shortening of arch length is related to transverse growth of the maxilla. www.indiandentalacademy.com
A drawing of the upper dental arch in occlusal view from photographs in natural size illustrates the marked sagittal shift since the age of 10 years of the lateral segments of the dental arch on the jaw base amounting to 5 mm in relation to the anterior implant, while the forward drift of the incisor segments was 2.5 mm. www.indiandentalacademy.com
Vertical rotation of the maxillary complex. • Downward and forward displacement of the maxilla during growth is associated with varying degrees of forward rotation. • The inclination of the nasal floor to the anterior cranial base is however maintained as a result of compensatory differentiated resorption. www.indiandentalacademy.com
• Forward rotation of the maxilla is associated with greater resorption of the nasal floor anteriorly than posteriorly. • Forward rotation of the face occurs because of greater facial growth posteriorly than anteriorly, associated with development in height of the cranial base. www.indiandentalacademy.com
• E.L. Korn S. Baumrind (JDR 1990) did similar study using longitudinal data on transverse widening of maxilla from sample of normal subjects (11 males 20 females) with metallic implants. Measurements were done annually between 8.5 to 15.5 yrs on frontal and lateral cephalograms . • Results showed transverse widening was greater in posterior then anterior part of maxilla • Widening continued through out the studied duration with no tapering or cessation of growth in the area as conventionally accepted. www.indiandentalacademy.com
Stanley Braun et al (A O 1999) C-axis: A growth vector for the maxilla • Nanda and Merill proposed M-point, a constructed point representing the center of the largest circle that is tangent to the superior, anterior, and palatal surfaces of the maxilla as seen in the sagittal plane.
• The C-axis, defined by sella-M-point, permits the quantification of a complex maxillary growth process in cephalometric terms relative to various craniofacial structures in the sagittal plane.
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• In the study 172 serial lateral cephalograms of 20 females and 174 serial lateral cephalograms of 19 males were taken. • The results were as follows: the rate of c axis increase in males was from a mea n of 41.69 degrees at 7.6 yrs to 45.5 degrees at 18.6 yrs for females it increased from 42.21 degrees at 7.4 yrs to 44.47 degrees at 18.75 yrs. • The study showed that growth along the c axis tends to decrease in females by age of 16. www.indiandentalacademy.com
• Jiuhui Jiang et al ( angle ortho 2007) did a proportional analysis of longitudinal craniofacial growth using modified mesh diagrams • Cephalograms selected from among 900 candidates were taken at 13 yrs then at 18 yrs of age. • Elaborate mesh diagrams were developed using 90 anatomic landmarks and additional 172 interpolated points www.indiandentalacademy.com
Modified mesh diagram www.indiandentalacademy.com
• Results of the study showed that mesh diagrams can provide a quantitative method of assessing craniofacial growth. • From 13 to 18 yrs ,two sexes with normal occlusion displayed different growth patterns ,in females most craniofacial regions exhibited growth proportional to mesh core rectangle . In males there was an upward enhanced shift of the anterior cranial base and a downward enhanced shift of mandible . www.indiandentalacademy.com
Mesh diagram for girls superimposition
Mesh diagram for males superimposition www.indiandentalacademy.com
CRANIAL BASE
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The cranial base or basicranium, the ventral part of the cranium, is the most complex structure of the skeleton. Its main function is to protect and support the brain and to provide a platform for facial growth. The cranial base is important in integrated craniofacial development and growth – especially the anterior cranial base, which has direct connections with upper-middle face and integrates with the facial elements into a growth complex (ethmomaxillary complex) www.indiandentalacademy.com
Âť The cranial base is mainly a midline structure composed of basioccipital, sphenoid, ethmoid and frontal bones in the midline and temporal bones laterally.
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Significance of cranial base • The housing for the brain impacts directly on many aspects of the developing facial complex. • The basicranium is involved in this fundamental and important relationship because the ectocranial side of the cranial floor is the interface with the face suspended beneath it. • The perimeter, alignment, and configuration of the basicranium prescribes a "template" that establishes the growth fields within which both the mandible and nasomaxillary complex www.indiandentalacademy.com develop.
PRE NATAL GROWTH OF CRANIAL BASE
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• The earliest evidence of cranial base formation is seen in the post or late somitic period : 4th_ 8th week of intra uterine life. • During this period mesenchymal tissue derived from primitive streak,neural crest and occipital sclerotomes condenses around developing brain: Ectomeningeal capsule • From around 40th day ectomeningeal capsule slowly starts converting to cartilage :chondrocranium www.indiandentalacademy.com
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This chondrification occurs in 4 regions Parachordal Hypophyseal Nasal Otic
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• The chondrification centers are– Parachordal cartilagesaround notochord – Sclerotomal cartilagesoccipital bone parts – 2 Hypophyseal cartilages-fuse to form basisphenoid cartilage – 2 presphenoid cartilagesbody of sphenoid – Orbitosphenoid and Alisphenoid- wings of sphenoid – Mesoethmoid cartilagewww.indiandentalacademy.com fused presphenoid
• Around 3rd month chondrocranium consists of mass of cartilages shaped like a capsule. • Bones which form from cartilage are lower occipital ,spheniod, petrous and mastoid,portions of temporal bone,styloid process of temporal bone,inferior turbinate bone and ethmoid. www.indiandentalacademy.com
• Chondrocranium reaches highest development at 3rd month of intrauterine life. • It includes axila region of the skull and olfactory capsule orbital wings and bases of temporal wings of sphenoid occipital condyles and tectum pecterius which lies dorsolaterally to occipital and temporal regions. • Except for nasal and basilar fibro cartilage it gets replaced by bone. www.indiandentalacademy.com
Ossification of cranial base • Described by Scott to appear from behind forward as follows: A centre for basioccipital portion at about middle of 3rd month 2-4 centre for post sphenoid 4 th month 2 centres for presphenoid 4 to 5 th month Single centre for mesethmoid 1st year after birth www.indiandentalacademy.com
• Growth of anterior cranial base completes between 8 to 10th year • Post cranial base grows to adulthood
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Flexure of the cranial base • During the embryonic and early fetal period, the cranial base becomes flexed in the region between the pituitary fossa and the sphenooccipital junction. • The face is hence tucked under the cranium. This flexure of the cranial base is accompanied by a corresponding flexure of the developing brain stem. • Thus the spinal chord and the foramen magnum which during the early stages of development were directed backwards now become directed downwards. www.indiandentalacademy.com
Flexure of the cranial base -arrow indicating the direction of the foramen magnum
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• This downward directed foramen magnum is an adaptation seen in man who, unlike animals, stands erect. • This flexure of the cranial base aids in increasing the neurocranial capacity. • Another consequence of the flexure is the predominant downward rather than forward displacement of the face during its growth from the cranial base. • At around the 1Oth week of intra-uterine life, the flexion of the base is about 65°. This flattens out a bit at the timewww.indiandentalacademy.com of birth.
Post natal growth of cranial base
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Post Natal Growth Of Cranial base •
The cranial base grows post natally by complex interaction between –
1. Extensive cortical drift & remodelling. 2. Elongation at Synchondrosis. 3. Sutural growth. www.indiandentalacademy.com
This combination provides: 1. Differential growth enlargement between the cranial floor and calvaria. 2. Expansion of confined contours in the various endocranial fossae. 3. Maintenance of passages and housing for vessels and nerves. www.indiandentalacademy.com
Basicranium • The cranial floor is the template from which the face develops hence what happens in the floor of the cranium affects the structure, dimensions, angles, and placement of the various facial parts • The endocranial surface of the basicranium, is characteristically resorptive in most areas. since the alignments of the sutures do not have the capacity to provide for the multiple directions of enlargement and the complex magnitude of remodeling required. www.indiandentalacademy.com
Circumcranial reversal line
(Darkly shaded)- The lining (Lightly shaded)- The endocranial bony surface of the whole surface of the calvaria, is predominantly depository; note the cranial floor is indicated by the arrow predominantly resorptive www.indiandentalacademy.com
Schematically represents an enlarged human basicranial fossa with sutures located at 1 and 2. These produce unidirectional sutural growth as indicated by the arrows. However, the two sutures present cannot produce the growth for the other directions also needed to accommodate brain expansion www.indiandentalacademy.com
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Fossa enlargement is accomplished by direct remodeling, involving deposition on the outside with resorption from the inside. This is the key remodeling process that provides for the direct expansion of the various endocranial fossae in conjunction with sutural and also synchondrosis growth.
- = Resoptive + = Depository www.indiandentalacademy.com
• The various endocranial compartments are separated from one another by elevated bony partitions . The middle and posterior fossae are separated by the petrous elevation ,the olfactory fossae by crista galli, the right and left middle fossae by midline sphenoidal elevation and the left and right anterior and posterior fossae are divided by midline bony ridge. All these elevated parts are depository in nature. www.indiandentalacademy.com
Resorptive & Depository Areas At The base Of Skull
Crista galli
Petrous Elevation
Midline bony ridge
www.indiandentalacademy.com Darkly shaded areas are resorptive areas
• The midventral segment of the cranial floor grows more slowly than the laterally located fossae. This accomodates the slower development of the medulla ,pons,hypothalamus ,optic chiasma etc. ,in contrast to the massive rapid expansion of the hemispheres.
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• A markedly
decreasing and tapering gradient of sutural growth occurs to provide for the varying extents of expansion required among the different midline parts themselves and between the midline parts and much faster growing lateral regions. www.indiandentalacademy.com
• The differential remodelling process maintains the propotionate placement of the spinal cord ,even though the floor of the posterior cranial fossa ,which rims the cord ,expands to greater extent than the circumference of the foramen magnum. www.indiandentalacademy.com
Synchondreal growth • The midline part of the basicranium is characterized by the presence of synchondroses They are a retention left from the primary cartilages of the chondrocranium after the endochondral ossification centers appear during fetal development. A number of synchondroses are operative during the fetal and early postnatal periods. •
Mid-sphenoidal synchondrosis
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Spheno-ethmoidal synchondrosis- Juvenile period
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Intra Occipital synchondrosis
- Perinatal fusion.
Spheno-occipital synchondrosis – Active-12-15 years Fuses -20 years -
Fuses -3-5 years
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Spheno occipital synchondrosis
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Structure • The basicranial synchondrosis can be characterized structurally as bipolar growth cartilages ,it is involved in endochondral ossification in two opposing directions. • The structure is similar to the basic plan for all “primary cartilages” • The synchondrosis is composed of wellorganised cell bands.
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From middle to distal ends, 3 zones are present: 1. A resting zone composed of chondrocyte precursors which direct formation and organization of the synchondrosis. 2. Proliferation zones 3. Hypertrophic zones. www.indiandentalacademy.com
• R – resting zone • Pr – proliferating zone • H – hypertrophic zone
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Synchondrosis is like two epiphyseal plates put back to back And separated by common zone of reserve cells. www.indiandentalacademy.com
• The sphenooccipital synchondrosis is the principal growth cartilage of the basicranium. • As with all growth cartilages associated directly with bone development, the sphenooccipital synchondrosis provides a pressure adapted bone growth mechanism. • This is in contrast to the tension adapted sutural growth process of the calvaria, lateral neurocranial walls, and the endocranial fossae. www.indiandentalacademy.com
• Endochondral bone growth by the sphenooccipital synchondrosis relates to primary displacement of the bones involved. The sphenoid and the occipital bones become sieved apart by the primary displacement process and at the same time, new endochondral bone, is laid down by the endosteum within each bone. www.indiandentalacademy.com
The posterior boundary of the maxillary complex is developmentally positioned to exactly coincide with, the boundary between, the anterior and middle cranial fossae, a like amount of forward displacement of both the anterior cranial fossa and the nasomaxillary complex suspended beneath it occurs.
The direction of sphenooccipital Synchondrosis is upwards it therefore carries the midface forward and downward.
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• The enlarging middle cranial fossa does not in itself push the mandible, anterior cranial fossa, and maxillary complex forward. The temporal and frontal have fibrous attachments to the middle and anterior cranial fossae, respectively. As both expands, these two fossae are thus pulled away from each other, but both also being moved together in a protrusive direction. www.indiandentalacademy.com
• This sets up tension fields in the various frontal, temporal, sphenoidal, and ethmoidal sutures, and this presumably triggers sutural bone responses (in addition to direct basicranial remodeling ). • Both fossae are thus enlarged, and the nasomaxillary complex is carried along anteriorly with the floor of the anterior cranial fossa from which it is suspended. www.indiandentalacademy.com
• The anterior fossae and the maxillary complex are carried anteriorly by the frontal lobes ,which is moved forward because of temporal lobe enlargement behind it.
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(I)Deposition on the orbital face of the sphenoid and in the. sphenofrontal suture (2)Forward displacement of the anterior cranial, fossae as the frontal lobes are displaced anteriorly (3)The petrous elevation (4)Deposition on the endocranial surface, and lengthening of the clivus occurs by growth at the sphenooccipital synchondrosis (5)The foramen magnum is progressively lowered also contributes to the lengthening of the clivus (6) The perimeter of the foramen enlarges (7) Addition to growth at the basicranial sutures.
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1) A decreasing gradient of sutural growth occurs approaching the midventral part of the basicranium is schematized (lightly shaded areas) (2)The endocranial fossae enlarge by a corresponding gradient of direct cortical remodeling, as shown by the darkly shaded areas (3)The clivus lengthens by endochondral bone growth at the sphenooccipital synchondrosis Also by direct downward remodeling of the basicranial floor.
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• Each anterior cranial fossa enlarges in conjunction with the expansion of the frontal lobes. Whereever suture are present ,they contribute to the increase in the circumference of the bones involved. Sphenofrontal,frontotemporal,sphenoethmoidal,f rontoethmoidal, and frontozygomativ sutures all participate in a closely coordinated ,traction adapted growth response to brain and other soft tissue enlargements. www.indiandentalacademy.com
• The bones all get displaced away from each other:primary displacement • Together with this ,the bones also enlarge outward by ectocranial deposition and endocranial resorption.
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•As long as the frontal lobes of cerebrum enlarge ,the inner table of the forehead correspondingly remodels anteriorly. • When frontal lobe enlargement slows and largely ceases sometime before about the 6th year, the growth of the inner table stops with it.. The outer table, however, continues to remodel www.indiandentalacademy.com anteriorly
• Arndt Klocke (Ajodo 2002) did a study in which two groups of untreated subjects were formed on the basis of a small and large cranial base angle N-S-Ar at the age of 5 years: the large cranial base angle group consisted of subjects with an N-S-Ar angle larger than 125° and the small cranial base angle group included subjects with an N-S-Ar angle of less than 120° Cephalometric data of the 2 groups were analyzed at subject ages 5 and 12 years. www.indiandentalacademy.com
• The presence of a large or small cranial base angle N-S-Ar had a rather limited effect on the development of sagittal jaw discrepancies during the longitudinal follow-up. In subjects with a large cranial base angle, the individualized ANB angle indicated a skeletal Class II tendency at the initial observation and at the longitudinal follow-up. • On the basis of variables SNB, S-Ar, S-N, and Ar-N, at the age of 12 years, it was possible to classify 88.1% of the initial large and small cranial base angle subjects, indicating a constancy of the skeletal pattern during the longitudinal follow-up. The relationship between cranial base flexure and skeletal pattern of the jaws seems to be established before the age of 5 years. www.indiandentalacademy.com
Melvin moss (Angle ortho 1955) conducted a study on 151 randomly seleted human crania to study the post natal growth of cranial base. Additionally 28 cases of class 2 and 21 cases of class 3 were abtained. On the tracings 3 angles were marked and measured. 1) Orbital angle formed by roof of the orbit 2) Cribriform angle formed by cerebral surface of cribriform plate of ethmoid 3) The palatal angle
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The results of the study were as follows The uniformity of the cribriform angle indicate that the median areas of the skull base are essentially stable while the lateral areas undergo prolonged change indicated by the orbital angle which shows progressive alterations Class 3 group shows significant alterations from the normal in the spatial relations of the medial pre sella portion of the skull base which has a greater downward inclination relative to the www.indiandentalacademy.com clivus.
• Frans P.G.M. Vander Linden (Angle ortho,1972) studied the growth of anterior cranial base on 80 human skulls ,the endocranial surface was studied in detail. A short brass wire was glued in transverse direction to the sphenoid bone to mark its most anterior median point. The distance between marker and midpoint between the wings of the anterior base level was evaluated. The latter has been indicated as SE by Enlow and by Knott as pt W. s
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Results of study showed: Point W forms an adequate representation of the anterior outline of the middle cranial fossae and can be used for a demarcation of the head in the anterio posterior direction . Distance between sella and pt W is constant from 6 to 15 yrs of age.
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Cranial base and maxilla: mutual interdependence
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• Growth of cranial base has direct effect on placement of midface,as anterior cranial base and cranial fossa elongate underlying space occupied by enlarging nasomaxillary complex pharynx and ramus increases corresponding . The spheno occipital complex elongate displacing entire midface anteriorly. www.indiandentalacademy.com
• Forward and downward inclined middle cranial fossamaxillary protrusive
mandibular retrusive • Maxilla- offset anteriorly • Mandible- down and back • Class II molar relationship
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• Upwards and backward inclined middle cranial fossa • Maxilla- placed backward • Mandible-rotates in a protrusive position. • Class III molar relationship
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Hunter enlow growth equivalent concept • a : anterior cranial base • b :spehno occipital complex • c : nasomaxillary complex • d : mandible
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CLINICAL CONSIDERATIONS
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Orthodontist an applied biologist • It is essential that the orthodontist be an applied biologist. The traditional overconcern with the alignment of teeth must be subordinated to a broader appreciation of bone system and neuro muscular system involved • Surveys have shown that two thirds of the cases seen for orthodontic therapy involve types of malocclusion in which growth and development play a significant role in the success or failure of mechanotherapy. www.indiandentalacademy.com
Growth spurts :important clinical consideration • Differential growth (different organs grow at different rates) and growth spurts are of vital importance to the orthodontist who must schedule his therapy so that it coincides with the most favorable growth period. Differential growth is time linked • Cranial base grows quite rapidly and attains adult size considerably before the face . Growth in cranial depth is most rapid ,with growth of width and height following in same order. www.indiandentalacademy.com
• In the face ,height shows the greatest change ,followed by depth and width. In the differential growth of various parts ,the height of the cranium and width of the face are closest to the adult size at birth. • Growth is essentially completed first in the head, then in width of the face and last in depth of the face.
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• Milton I Houpt (AJODO 1975)investigated changes in craniofacial complex in human fetuses between 12 to 19 weeks.(31 male and 38 female fetus were studied) • The growth rates of components of craniofacial complex is constant between 12 to 19 weeks, no significant gender differences were seen • With exception of mandible the components of craniofacial complex grow faster in length than height or width, the rate of growth of cranium is two to four times greater than the face. www.indiandentalacademy.com
• Sex linked nature of growth with female pubertal spurt occurring ahead of that of male has been shown (Bjork and helm 1967)
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• Woodside (1969) ,in his study of Burlington group • Points out that growth spurts are really possible and sex linked. • The greatest increment of growth are actually at the 3 year age level. The second peak is from 6 to 7 years in girls and 7 to 9 years in boys. The third peak is 11 to 12 yrs in girls and 14 to 15 yrs in boys. The tendency is for boys to show two or three peaks and girls largely show only two peaks. www.indiandentalacademy.com
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• The clinical implications are obvious for the orthopedic correction of maxillomandibular malrelationships. Pubertal increments offer the best time for large number of cases. • Very few girls show mixed dentition growth spurt and jaw change objectives are more likely to be successful during this period among boys.
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Monique Henneberke Birte Prahl-Andersen (AJODO 1994.) Growth changes of the cranial base (S-N, N-Ba, and S-Ba) were evaluated. The cranial base displayed sexual dimorphism in the timing and amount of growth. All dimensions measured in girls were significantly smaller than in boys (p < 0.05). No adolescent growth spurts were found in girls; boys showed adolescent growth spurts for S-N and N-Ba. Adolescent growth velocities were significantly greater for boys than for girls. www.indiandentalacademy.com
â&#x20AC;˘ Similarly if an orthodontist is looking for growth in width of denture area ,he is likely to be disappointed after the fifth or sixth year of life since little change occurs then in the width of the dental arch anterior to the first permanent molars. In the mandibular arch the inter canine width is complete by nine to ten years of age in both sexes. www.indiandentalacademy.com
â&#x20AC;˘ In the maxilla the intercanine width is complete by 12 yrs in females and continues till 18 yrs in males. The clinical implications are quite obvious here .The final horizontal growth increments in the mandible ,particularly in the males cause a forward movement of the mandibular base. This basal change eliminates any persisting flush terminal plane tendencies,however the bodily mandibular thrust forward is unmatched by the comparable maxillary horizontal growth changes. Hence, the maxillary intercanine dimensions serves as a â&#x20AC;&#x153;safety valve â&#x20AC;&#x153; for this basal discrepancy.
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â&#x20AC;˘ Another variable to be considered is direction of growth . â&#x20AC;˘ Since both maxilla and mandible grow downward and forward at a more rapid rate then the cranium after 4 and 5 th yr ,an orthodontist can modulate growth ,stimulate deficient maxillary growth or retard and redirect its growth. www.indiandentalacademy.com
• Orthodontist is literally an “orthopedic surgeon” and channeling of growth offers the greatest hope to the orthodontist at present. • Head gear and face mask have been successfully used to redirect growth of maxilla and modify the skeletal malocclusions. www.indiandentalacademy.com
â&#x20AC;˘ Jeremy J et al (AO ;2003)have conducted study to prove that various orthopedic therapies including head gear ,facemask and functional appliances may induce sutural strain ,leading to modification of otherwise natural suture growth. â&#x20AC;˘ Mechanical stresses induced by the appliances are capable of modulating the sutural growth, because mechanical stresses transmit through bone their effects are experienced in a hierarchial manner sequentially as tissue level bone strain, interstitial fluid flow that in turn induces cell level strain on bone cells and subsequently anabolic or catabolic effects. www.indiandentalacademy.com
Head gear : â&#x20AC;˘ Forces applied on to the maxilla can be used to restrict its downward and forward growth. The distal force in this case is applied through the centre of resistance of the maxilla .Forces in range of 350 -450 gms on each side for a minimum of 12 to 14 hrs /day are required. â&#x20AC;˘ This effect can be best tapped during the www.indiandentalacademy.com pre adolescent period.
â&#x20AC;˘ Kazuo Tanne(angle ortho 1996) in his article on association between the direction of orthopedic headgear force and sutural responses in the nasomaxillary complex has shown the stress distribution in the sutures produced by orthopedic appliances. â&#x20AC;˘ Finite elements analysis was employed using a 3 d model of the craniofacial complex that consisted of 2918 nodes and 1776 solid elements. The model also included 18 sutural systems in the complex www.indiandentalacademy.com
• When 30° inferior, parallel, and 30° superior forces were applied, considerable variation in normal stresses at the sutural interfaces was observed in association with substantial shear stresses. • In loading with forces in 52.4° and 60° superior directions, compressive stresses were similarly generated in most anatomic areas and both the normal and shear stresses reduced and exhibited a convergence to a certain level. • As the force direction approached that of the CRe, mean principal stresses approached a uniform level of compressive stress www.indiandentalacademy.com
Face mask or reverse head gear â&#x20AC;˘ Given when anterior protractory force is required on the maxilla. â&#x20AC;˘ Amount of force required to bring skeletal change is about 450 gms per side /day for 12 to 14 hrs with a 15 to 20 degree downward pull to the occlusal plane to produce a pure forward translatory motion of the maxilla ,if the line of force is parallel to the occlusal plane ,a forward translation as well as upward rotation takes place. www.indiandentalacademy.com
Patients wearing face mask
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â&#x20AC;˘ Gregory A. Vaughn et al (AJO 2005) has shown through randomised trial study that early face mask therapy is effective to correct the skeletal class 3 malocclusions. â&#x20AC;˘ If face mask therapy is preceded by rapid maxillary expansion the effect is greater compared to face mask therapy without rapid maxillary expansion www.indiandentalacademy.com
• Gautam P., Valiathan A. (AJODO 2007) evaluated stress distribution along craniofacial sutures and displacement of various craniofacial structures with rapid maxillary expansion (RME) therapy. • They concluded that : • RME facilitates expansion of the maxilla in both the molar and the canine regions. It also causes downward and forward displacement of the maxilla and thus can contribute to the correction of mild Class III malocclusion. The downward displacement and backward rotation of the maxilla could be a concern in patients with excessive lower anterior facial height. High stresses along the deep structures and the various sutures of the craniofacial skeleton signify the role of the circummaxillary sutural system in downward and forward displacement of the maxilla after RME. www.indiandentalacademy.com
Maxillary expansion â&#x20AC;˘ The inter maxillary and interpalatine sutures make up the mid palatal suture. Rapid maxillary expansion should be initiated prior to ossification of this suture to bring about skeletal type of expansion in maxilla. â&#x20AC;˘ The opening of the midpalatal suture is fan shaped with the maximum opening occuring at the incisor region and gradually diminishing towards the posterior part of the palate. www.indiandentalacademy.com
â&#x20AC;˘ An increase of 10 mm can be achieved by RME ,rate of expansion is 0.2 to 0.5 mm per day. Rapid palatal expander www.indiandentalacademy.com
â&#x20AC;˘ John f Cleall et al (angle ortho 1965 ) conducted a study on rhesus monkeys to study the effect of expansion on mid palatal suture. It was seen that the forces disrupted the mid palatal suture and resulted in increase in maxillary width ,the resultant defect is rapidly and completely healed following restoration of normally growing suture. www.indiandentalacademy.com
Growth anomalies and role of orthodontist
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CLEFT PALATE â&#x20AC;˘ Cleft palate is a condition in which the two plates of the skull that form the hard palate (roof of the mouth) are not completely joined. Cleft palate occurs in about one in 700 live births worldwide. â&#x20AC;˘ Palate cleft can occur as complete (soft and hard palate, possibly including a gap in the jaw) or incomplete (a 'hole' in the roof of the mouth, usually as a cleft soft palate. It occurs due to the failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine processes (formation of the secondary palate).
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Patients with cleft palate www.indiandentalacademy.com
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Orthodontic intervention â&#x20AC;˘ One role of orthodontic intervention is to minimize the severity of the growth disturbance. Interventions vary according to the type of cleft. â&#x20AC;˘ In CL/P, orthodontic appliances can be used to realign the premaxilla into a normal position prior to lip closure. Orthodontic interventions in patients with cleft palate are frequently aimed at maxillary arch expansion, correction of malocclusion, and correction of an often developing class III skeletal growth pattern. The most beneficial period for orthodontic interventions in isolated cleft palate may be during the mixed dentition period.
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Other syndromes involving mid facial anomalies • • • • • • • •
Pre-maxillary aplasia or hypoplasia Median Cleft face syndrome Treacher Collins' syndrome Aperts syndrome Achondroplasia, Stickler syndrome Crouzon syndrome The main role of an orthodontist is to minimize the gross deficiency by early orthopedic interventions as well as later fixed appliance therapy to correct dental malocclusions. www.indiandentalacademy.com
Conclusion â&#x20AC;˘ No craniofacial component is self contained and self regulated . Growth of a component is not an isolated event unrelated to other parts: it is a composite change of all components â&#x20AC;˘ Meaningful insight into all this underlies the basis for clinical diagnosis and treatment planning . The direct target for clinical intervention must be the control process regulating the biology of growth and development. www.indiandentalacademy.com
REFERENCES •
1)Enlow DH, Bang S. Growth and remodelling of the human maxilla. Am J Orthod. (1965, 51: 446-464).
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2)Bjork A, Skieller V. Growth of the maxilla in three dimensions as revealed radiographically by the implant method. Br J Orthod. 1977, 4: 5364.
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3)Enlow DH. Handbook of facial growth. 3rd Ed.,1996, W. B. Saunders Company.
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www.indiandentalacademy.com 4)Melvin L.Moss Postnatal Growth Of Human
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5)Stanley Braun, Robert T. Rudman, Hugh J. Murdoch, Shaun Hicken, Russell Kittleson, Donald J. Ferguson, C-axis: A growth vector for the maxilla AO 1999:69;539-42.
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6)Kazuo Tanne; Susumu Matsubara, Association between the direction of orthopedic headgear force and sutural responses in the the nasomaxillary complex ( A O 1996;66(2):125-130.)
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7)Moyers RE. Handbook of orthodontics. 4th Ed., 1988, Year Book Medical Publishers. www.indiandentalacademy.com
• 8)Graber TM. Principles and practice of orthodontics. 3rd Ed.,1966. • 9)Proffit WR. Contemporary orthodontics. 3rd Ed., 2000, Mosby, Inc. • 10)Salzmann JA. Practice of orthodontics vol.1. 2nd Ed., 1966, J. B. Lippincott Co. www.indiandentalacademy.com
• 11) Sadler TW. Langman’s medical embryology. 9th Ed., 2004, Lippincott, Williams & Wilkins • 12)Jeremy J. Mao, Xin Wang, Ross A. Kopher: Biomechanics of Craniofacial Sutures: Orthopedic Implications(Angle Orthod 2003;73:128–135.)
• 13)J.J. Mao Mechanobiology of Craniofacial SuturesJ Dent Res 81(12):810-816, 2002 • 14)John F Cleall et al ,expansion of the mid palatal suture in the rehus monkey (angle ortho 1965,23 -34 ) www.indiandentalacademy.com
• 15)Melvin moss, The primary role of functional , matrices in facial growth ;(AJODO,1969 55:566 577) • 16)Gregory A. Vaughn , The effects of maxillary protraction therapy with or without rapid palatal expansion ;a prospective randomised trial ; AJODO,2005 :299 to 309 • 17)E.L.Korn S. Baumrind, Transverse development of the human jaws between ages 8.5 and 15.5 studied longitudinally with use of implants ( JDR 1990, 69:1298 to 1306) www.indiandentalacademy.com
• 18)Nie X. Cranial base in craniofacial development: Developmental features, influence on facial growth, anomaly, and molecular basis. Acta Odontol Scand. 2005, 63: 127-135. • 19)S. Eugene Coben ,The spheno-occipital synchondrosis: The missing link between the profession’s concept of craniofacial growth and orthodontic treatment(AJODO1998;114:709-12) • 20)Kristine S.West, and James A. McNamara, Changes in the craniofacial complex from adolescence to midadulthood: A cephalometric study (AJODO 1999;115:521-32) www.indiandentalacademy.com
• 21)Surender K. Nanda, Differential growth of the female face in the anteroposterior dimension A O 1992: 62;23-34
• 22)Sejrsen B, Jakobsen J, Skovgaard LT, Kjaer I. Growth in the external cranial base evaluated on human dry skulls, using nerve canal openings as references. Acta Odontol Scand. 1997, 55:356-364.
• 23)Toshio Deguchi , Very early face mask therapy in Class III children(angle orthod, Vol. 69, No. 4, pp. 349–355. • 24)Arndt Klocke,,, Ram S. Nanda,, Bärbel ,Role of cranial base flexure in developing sagittal jaw discrepancies ,Ajodo 2002 122 (4) :386 391 www.indiandentalacademy.com
• 25)Bjork ,Helm,Prediction of age of maximum pubertal growth in body height. (angle ortho 1967 ,37:134-143) • 26)Milton I. Houpt,growth of craniofacial complex of the human fetuses (AJODO 1975,58:4;373378 ) • 27)Gautam P. ,Valithan A. , Adhikari R., Stress and displacement patterns in the craniofacial skeleton with rapid maxillary expansion: a finite element method study. (Ajodo 2007,july 132;1:111) www.indiandentalacademy.com
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