FUNCTIONAL MATRIX THEORY
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INTRODUCTION: A discussion of the regulation of craniofacial growth seems an appropriate place to outline the conceptual milieu within which the functional matrix hypothesis originated & exists. The hypothesis derives from the century old work of His & Roux and is compatible with recent epigenetic concepts associated with Waddington, Bleschmidt and Lovtrup. The hypothesis serves as a conceptual bridge between the concepts of function and epigenesis. www.indiandentalacademy.co m Jump to first page
BASIS FOR DEVELOPMENT OF THEORIES It is a truism that growth is strongly influenced by genetic factors, but it also can be significantly affected by the environment, in the from of nutritional status, degree of physical activity, health or illness and a number of similar factors. Since a major part of the need for orthodontic treatment is created by disproportionate growth of the jaws, it is necessary to learn how skeletal growth is influenced and controlled to understand the etiologic processor of malocclusion and dentofacial deformity. Great strides have been made in recent year in improving the understanding of growth control. Exactly, what determines the growth of the jaws, however remained www.indiandentalacademy.co m unclear and continues to be the subject of intensive research. Jump to first page
DEFINITIONS GROWTH Growth is defined as a change in size or shape or spatial position of any living tissue or organ. Krogman defined it as increase in size, change in proportion and progressive complexity. Todd defined it as an increase in size, and the development as progress towards maturity. DEVELOPMENT It refers to all the naturally occurring unidirectional changes in life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death. It encompasses the normal sequential events between fertilization and death. www.indiandentalacademy.co m So development = growth +differentiation+translocation. Jump to first page
DIFFERENTITATION It is a change from generalized cells or tissues to more specialized kind during development. It is change in quality or kind. TRANSLOCATION It is the change in position eg. Chin point moves downward and forward for more than any growth. MATURATION Qualitative changes which occurs with ripening or aging.
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GROWTH SITES VS GROWTH CENTRE A site of growth is merely a location at which growth occurs, whereas a Centre is a location at which independent (genetically controlled) growth occurs. In general all centres of growth also are sites but the reverse is not true. In cartilage, cells of growth plate are capable of creating a tissue separating force by virtue of interstitial expansion. When such units are transplanted to subcutaneous sites the dimensions continue to increase. The cells of suture however are not capable of generating a tissue separating force. When transplanted to subcutaneous site the transplant no longer grow-apart. So Baume called growth centers are endochondral ossification with tissue separating force contributing to increase of skeletal mass and growth sites are www.indiandentalacademy.co regions ofm periosteal or sutural bone formation and modeling resorption adaptive to environmental influences. Jump to first page
EPIGENETICS Epigenetics, as defined here, includes (1) all of the extrinsic (extra oraganismal) factors impinging on vital structure, including importantly mechanical loadings and electro electric states and (2) all of the intrinsic (intraoraganismall) biophysical, biochemical and bioelectric micro environmental events occurring on, in, and between individual cells and cells and extracellular substances. HIERARCHY Biological structures are hierarchically organized, with structural and functional complexity increasing “upward” from the ever – expanding family of subatomic particles to protons, electrons, atoms, molecules, subcellular organelles and on cells, www.indiandentalacademy.co m tissue, organs and organisms. Jump to first page
EMERGENCE It consist of the appearance, at each successively higher and structurally and/or operationally more complex level, of new attributes or properties, not present in the lower levels, whose existence or functions could not in any way be predicated even from a complete knowledge of all the attributes and properties of any or all of the preceding lower organizational levels. This phenomenon occurs in all natural hierarchies. For example, full knowledge of all the attribute and properties of an osteocyte does not permit prediction of the attributes and properties of any type of bone tissue. And full knowledge of all attributes and properties of all constituent bone tissue types does not permit prediction of the form (size and www.indiandentalacademy.co shape), growth or functions of a macroscopic “bone�. m Jump to first page
FUNCTIONAL MATRIX THEORY Based on the “functional cranial component theory� of Van der Kjaauw hi own experimental work and that of others combined with clinical interpretations and experiences MELVIN L:MOSS in 1960 has formulated the functional matrix theory. This theory can be described as follows. It claims that origin, growth & maintenance of skeletal tissues & organs are always secondary, compensatory and mechanically obligatory responses to temporally & operationally prior events and processes occurring in related non-skeletal tissues, organs and functioning spaces (eg. Functional matrices either periosteal or capsular. www.indiandentalacademy.co m Jump to first page
There is no direct genetic influence on the size, shape or position of skeletal tissues only the initiation of ossification. All genetic skeletogenetic activity is primarily upon the embryonic functional matrices. In a softer view, neither the cartilage of the mandibular condyle nor the nasal septum cartilage is a determent of jaw growth. Instead he theorizes the growth of the face occurs as a response to functional needs and is mediated by soft tissue in which the jaws are embedded. In a conceptual view, the soft tissues grow, and both and cartilage react. www.indiandentalacademy.co m Jump to first page
Moss stresses the dominance of nonosseous structures of the craniofacial complex over the bony part. Moss claims that the growth of the skeletal components, whether endochondral or intramembranous in origin, is largely dependent on the growth of the functional matrices. The growth of the functional matrix is primary, that of a skeletal unit secondary. This hypothesis has initiated many experimental and clinical investigations but also has given rise to fruitful controversy (Johnston 1976).
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FUNCTIONAL CRANIAL ANALYSIS Moss says, “the head is a composite structure, operationally consisting of a number of relatively independent functions olfactions, respiration, vision, digestion, speech, audition, equilibration and neural integration. Each function is carried out by a group of soft tissues which are supported and/or protected by related skeletal elements. Soft tissues and skeletal element related to a single function are termed FUNCTIONAL CRANIAL COMPONENT. Thus the component handling speech would consist of the lips, teeth,tongue,oral cavity, nasal cavity etc., any aspect of the head that enables a person to speak is part of this functional component. www.indiandentalacademy.co m Jump to first page
The totally of all the skeletal element associated with a single function is termed SKELETAL UNIT. The totally of all the soft tissues associated with single function is termed FUNCTIONAL MATRIX origin, growth and maintenance of the skeletal unit depend almost exclusively upon its related functional matrix.
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Micro and Macro skeletal units: Skeletal units may be composed variably of bone, cartilage (or) tendinous tissues. When such a bone consist of a number of skeletal units, we call them micro skeletal units. Both maxilla and mandible are formed of a number of such contiguous micro skeletal units. When adjoining portions of a number of neighboring bones are united to function as a single cranial component, we term this a macro-skeletal unit. eg: endocranial surface of the calvaria. www.indiandentalacademy.co m Jump to first page
THE FUNTIONAL MATRIX One Function Functional cranial component Functional matrix
skeletal unit
Periosteal Matrix------affects--------------1.Microskeletal Capsular Matrix--------affects----------ďƒ 2.Macroskeletal .Masses .Functioning Spaces www.indiandentalacademy.co m Jump to first page
Mandible is a macroskeletal unit. Capsular matrices act on the macroskeletal unit that is whole mandible and they bring about translation or passive growth. They do so by changing the volume of the capsule within which the functional cranial components are embedded. Moss speak of the mandible as a group of microskeletal units. Thus the coronoid process is one skeletal unit under the influence of temporalis muscle. The alveolar bone is under the influence of teeth. Teeth are also a functional matrix, indeed most orthodontic therapy is based firmly on the fact that when this functional matrix grows or is moved, the related skeletal unit ( the alveolar bone) responds appropriately to this morphogenetically primary demand. www.indiandentalacademy.co m Jump to first page
FUNCTIONAL CRANIAL COMPONENT (eg: mandible)
Skeletal Unit
Microskeletal
Macroskeletal
Eg : coronoid eg : mandible
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Functional Matrices
Capsular Matrices
Periosteal Matrices
eg : oral capsule eg : muscles Act on macro Act on Macro Skeletal Unit.
Skeletal Unit.
Bring about
Bring About
Passive Growth or Translation
Active growth or Transformation Jump to first page
There are two basic types of functional matrices .Periosteal matrix . Capsular matrix PERIOSTEAL MATRIX This term relates the matrix to those tissues that influence the bone directly through the periosteum. Muscles are attached to the periosteum & consequently are examples of this kind of matrix.
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Periosteal matrix affect a microskeletal unit meaning that the spare of influence is usually limited to a part of muscles most of its action on the coronoid process - a micro unit of the mandible. Coronoid process first arises within the earlier from of anlage of the temporalis muscle whose contractile abilities are well developed in prenatal stages. It, subsequent growth also occurs within this muscular matrix..
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The experimental removal of the temporalis muscle or its denervation invariably result in the actual diminution of the size and shape of the coronoid process or even its total disappearance. Similarly established hyperactivity of the temporalis muscle produces increase in the size and shape of the coronoid process Figure showing the dependence of the coronoid process (skeletal unit) upon the demands of its functional matrix (temporalis muscle) is shown in these alterations in size and shape following www.indiandentalacademy.co unilateral muscle resection. m
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The total growth change of the coronoid process are at all times a direct compensatory response to morphogenetic and functional demand as of the temporalis muscle function. All responses of the osseous portion of the skeletal units to periosteal matrices are brought about by the complementary and interrelated process of osseous deposition and resorption. The resultant effect of all such skeletal unit responses to periosteal matrices is to alter their size and / or their shape. A tooth is responsible for the alveolar bone that supports it; Extraction of tooth causes disappearance of microskeletal unit (alveolar process) In addition to muscles, blood vessels, nerves and glands also produce morphologic changes in their related skeletal www.indiandentalacademy.co units in a completely homologous manner. m
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CAPSULAR MATRIX Included in this class of matrix are those masses and spaces that are surrounded by capsules. All the functional cranial components (functional matrices together with the skeletal units) organize in the form of cranial capsules. .Neurocranial capsules .Orofacial capsule
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Each of these capsules is an envelope which contains a series of functional cranial components which are two covering layer. In the neurocranial capsule, the covers consists of skin and duramater. Figure showing the neurocranial and orofacial capsular matrices are shown. The neural capsular matrix consists of the entire neural mass, including the dura matter, while the orofacial capsular matrix consists of these functioning spaces. In both cases the skeletal units exist completely within their respective capsules. www.indiandentalacademy.co m Jump to first page
Orbital mass is surrounded by the supporting tissues of the eye. Any enlarged eye or small eye will cause a corresponding change in the size of orbital cavity. Here eye is functional matrix.
In the orofacial capsule skin and mucosa form the limiting layers. Spaces intervening between the functional components themselves and between them and the www.indiandentalacademy.co capsule are filled with indifferent loose connective m tissues. Jump to first page
Each capsule surrounds and protects capsular functional matrix – in one case, the neural mass which consists of brain plus leptomeninges and, most important, cerebrospinal fluid; in the second case, the oranoasopharyngeal functioning spaces. The common factor in both cases is that the capsular matrices exist as volumes.
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NEUROCRANIAL CAPSULE In the case of neural skull, it is quite easy to visualize the calvarial bones as lying within a neurocranial capsule. The composition of this capsule in the adult is easily stated; these are so called “five layers� of the scalp, then the bone itself; and, finally, the two-layer duramatter.
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The calvarial bones consist of a number of contiguous skeletal units; outer table, inner table, diploid space (and variably sinuses). Each of these microskeletal units obviously has its specific periosteal matrix, muscles and vessels being good examples.
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It has been demonstrated repeatedly that it makes little difference whether or not this neural mass contains a “normal� amount of brain tissue. It is the total neural mass volume which is morphogenetically significant. The expansion of this enclosed and protected capsular matrix volume is the primary event in the expansion of the neurocranial capsule. The response of the capsule as a whole, is to expand in a compensatory manner. All of the included and enclosed functional cranial components that the preinstall matrices and their microskeletal units, are then obligatorily carried outward within the capsule in a totally passive manner. www.indiandentalacademy.co m Jump to first page
It is extremely important to note here that such translations occur without the necessity of involving the processes of selective periosteal apposition and resorption. Admittedly, in “normal� growth it is difficult to determine this point by superficial analysis, since the activity of periosteal matrices on their respective micro skeletal units goes on simultaneously.
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It is only when we examine these pathologic, or experimentally produced, situations in which periosteal matrices have been prevented from exerting their morphogenetic activity that we can observe clearly the passive, non periosteal, translative growth produced by the capsular matrices. The expansion of neurocranial cranial capsule is always proportional to increase in neural mass. The neural skull does not grow first and thus provide space for the secondary expansion of the neural mass. Rather, the expansion of the neural mass is the primary event which causes the secondary and compensatory growth of the neural skull. www.indiandentalacademy.co m Jump to first page
This phenomenon can be seen readily in humans in two experiments of nature. .when the brain is very small, the cranium is also very small ad the condition of “MICROCEPHALY� result. In this case the size of the head is an accurate representation of the size of the brain.
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.HYDROCEPHALY: in this case reabsorption of the cerebro spinal fluid is impeded, the fluid accumulates and intracranial pressure builds up, which impeded, the development of the brain. So the hydrocephalic may have small brain and enormous growth of the cranial vaultcranium two or three times its normal size with enlarged frontal, parietal and occipital bones.
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OROFACIAL CAPSULE As the calvarial bones are embedded in a neurocranial capsule and are translated here by, so are the oronasomaxillary bones embedded in the orofacial (splanchno cranial) capsule.
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The primary expansion of functioning oronasopharyngeal spaces on a morphogenetic stimulus brings about secondary, compensatory expansion of the orofacial capsule. The facial bones are passively carried outward by primary expansion of the enclosed orofacial matrices (orbital, Nasal and oral matrices). In addition essential growth of the sinuses and spaces perform important functions.
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Where the role of functional matrix becomes most difficult to visualize is, in development of the face. According to moss, the nasal cartilage and the condyles of the mandible are growth sites and therefore incapable of tissue separating force. As a consequence, the translation of the middle and the lower face downward and forward must be accomplished by the oral-nasalpharyngeal capsules. The soft tissues of these capsules are of necessity the determinant of their size and position in space. The skeletal units only respond, offering continually adapting biomechanical support. The factor that dictates the size of the facial capsules is the volume of the functioning spaces. The patency and adequacy of oronasal tubes are so fundamental that nature programs their size and guarantees that the increased www.indiandentalacademy.co demands of somatic growth are met by craniofacial expansion. m
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Moss contends, then, that all the loci of new bone formation (sutures, periosteum, spheno-occipital synchondrois, nasal cartilages and condyles) are growth sites and not growth centers. None of these sites contain genetic information that can determine their ultimate form; all of them are at the disposal of the functional matrices related to them.
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MANDIBULAR GROWTH Mandibular growth demonstrates the integrated activity of periosteal and capsular matrices in facial growth. Since the condylar cartilages are not primary sites of mandibular growth but loci with secondary, compensatory periosteal growth. Bilateral condylar cartilage removal does not inhibit the spatial translation of contiguous mandibular functional components. Nor does the condylectomy inhibit the changes in the form of their microskeletal units as their microskeletal units as their individual matrices alter function demands. www.indiandentalacademy.co m Jump to first page
If there are no condylar processes how does the mandible alter its spatial position? No combination of periosteal growth changes of microskeletal unit form is capable of explaining this. It is only by considering that the orofacial capsule expands in response to the morphogenetically previous volumetric expansion of the orofacial functioning spaces that we can comprehend the observed translation in space.
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Mandibular growth is seen now to be a combination of the morphologic effects of both the capsular and periosteal matrices. The capsular growth causes an expansion of the capsule as a whole. The enclosed and embedded macroskeletal unit (the mandible) is passively and secondarily translated in space to successively new position. Under normal conditions then the periosteal matrices related to the constituent mandibular micro skeletal unit also respond to this volumetric expansion. Such alteration in spatial position inevitably causes them to grow. This calls for direct alteration in the size and shape of the microskeletal unit. www.indiandentalacademy.co m Jump to first page
Moss (1973) termed this change in size and in shape during growth as TRANSFORMATION and the change in spatial position as Translation. the sum of translation plus transformation comprise the totality of mandibular growth. Only a small percentage of the bone growth in the facial skeleton is due to pure transformation or pure translation. A combination of both types of growth is usually involved, although translation almost always result in bone transformation. www.indiandentalacademy.co m Jump to first page
REGULATION & CONTROL OF FUNCTIONAL MATRICES Functional matrices are controlled by neurotrophic processes. NEUROTROPHISM It is a “non-impulse transmittive neuro function, involving axoplasmic transport, providing, for the long term interaction between neurons and innervated tissues which homeostatically regulates the morphological, composition and functional integrity of those tissues. The nature of the neurotrophic substances and the process of their introduction are unknown at present. Moss does indicates that there are three general categories. .Neuro-epithelial
www.indiandentalacademy.co m .Neuro-visceral
.Neuro-muscular
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NEURO-EPITHELIAL TROPHISM It is a quality rather than type of reinnervating axons that determines whether regeneration will occur. As example amphibian limb regeneration is initiated only after intimate neuroepithelial contact. The mitotic activity necessary for normal epithelial turnover of taste buds the maintenance is being, the expression of their genomic potential in such processes as DNA and enzymatic synthesis are all under the direct and continuous afferent gustatory neurotrophic control.
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Neuro visceral trophism Periosteal functional matrices regulate the size and shape of specifically related skeletal unit. It is apparent that genetic control of structural functional and chemical attribute of these same matrices can not reside in the matrices them selves, but rather reflect constant neurotrophically regulated homeostatic control of genome. It is also clear that similar trophic control probably exits for capsular matrices which passively regulate position of both skeletal unit and periosteal matrices. Some degree of visceral neurotrophic control is probable. Eg: salivary glands among other spalanchnocranial viscera are trophically regulated atleast partially. www.indiandentalacademy.co m Jump to first page
Neuro muscular trophism Moss indicated that skeletal muscle ontogenesis normally requires motor neuron innervation to proceed past the stage of myotubes. Nerve influences give expression in the cell. A qualitatively different myosin that resemble that of muscle formerly innervated by the nerve is synthesized in cross innervated muscle, which indicates species of protein it has been synthesized. Experiments show that significant morphologic, biochemical and functional parameters of reinnervated muscle, come to more closely resemble those of the muscle formerly innervated by the new ectopically implanted nerve. DISCULESCU et al state, “The complex chain of events leading to particular expression of the genetic embryonic potential is not www.indiandentalacademy.co wholly within the cell but also includes informational elements m contributed by the nerve�. Jump to first page
SAMAHA et al writes, “A new species of protein has been synthesized and we there fore suggest that the nerve influence gene expression of the cell�. Moss feels the periosteal matrices reflect constant neurotrophically regulated homeostatic control of the genome. Similar trophic control probably exits for capsular functional matrices, which passively regulates the position of both the skeletal units and the periosteal matrices. If some degree of visceral neurotrophic control is probable then we are close to knowing their ultimate stimulus for growth. Assuming such role of neurotrophism (neural nourishment) dictates that at no time any of the nerves is subject to torsion, compression, tension and shear. Hence with respect to inferior alveolar nerve with Foramen ovale into the mandibular canal out of mental foramen, its integrity is never threatened by growth or www.indiandentalacademy.co functioning of the lower jaw. m
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GENETICS, EPIGENETICS AND CAUSATION It can be shown that the combination of genomic and epigenetic factor is a necessary cause of craniofacial growth. A review of some recent literature serves to clarify this conclusion which is of potential clinical use therapeutic intervention is always an epigenetic event. Clinical scientists suggest that “the post fertilization genome does not contain sufficient information to regulate all subsequent development. It is postulated that the additional necessary epigenetic information is self – generated concomitant with the attainment of increasing structural and functional complexity”. In this view the interaction of both genomic and epigenetic factors is required to regulate (or “cause”) development. The genome is not viewed as containing some prewww.indiandentalacademy.co existent blueprint that merely requires an appropriate environment m within which it can become phenotypically expressed. Jump to first page
As unconformable as the epigenetic hypothesis may seem to commonly accepted clinical views, Moss suggest that many of the difficulties are diminished after analysis of the term causation and after a review of some pertinent data and concept.
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CAUSATION There are four principal causes of ontogenesis. .Material (what is acted upon?) .Formal (by what set of rules?) .Efficient (how?) .Final (why?) These may be categorized as either intrinsic (material & formal) and extrinsic (efficient): final cause i.e. exiting before the creation of some specific state or structure. Efficient cause is proximate: i.e., its operation immediately causes the creation of a new state or attribute. Material and formal causes are intrinsic. Because they reside within vital structure (either intracellularly or intercellularly). www.indiandentalacademy.co (efficient causes are extrinsic – they represent the entire spectrum m of epigenetic processes, mechanisms and events capable of Jump to first page being imposed on vital structures.
In biology material, without reference to any specific structural (anatomical) arrangement. Formal cause is the genomic code. They act at the molecular level to regulate the initial creation of the constituents of material cause. Efficient causes are the epigenetic factors, whose actions immediately regulate the next development branching point. In ontogenesis, genomic (intrinsic, and epigenetic (extrinsic, proximate) factors are each a necessary cause, but neither alone is a sufficient cause. Only the interaction of both provides both the necessary and sufficient cause of morphogenesis.
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Epigenetics involves the production of new information during development as structure and function became increasingly complex. Both structure and function evolve alterations in the biomechanical, biochemical, biophysical and bioelectrical parameters of the developing organism both intra and intercellularly. These alteration of state(new information) act significantly to regulate subsequent development stages, as well as to result genomic reaction to these –altered environmental states. In the hypothesis “environment� is not just permissive and supportive but also regulative.
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EPIGENETIC EVENTS AND PROCESSES 1. The functional matrix hypothesis has demonstrated repeatedly that the presence, and growth changes in size, shape and location of all craniofacial skeletal attribute are epigenetically regulated. In summary from, the functional matrix hypothesis explicitly claims that the origin, growth and maintenance of all skeletal tissues are always secondary, compensatory and obligatory responses to temporally and operationally prior events or processes that occur in specifically related non-skeletal tissues, organs or functioning spaces (functional matrices). In this view, development could be described as a hierarchical series of proximate, efficient, extrinsic and necessary causes. www.indiandentalacademy.co m Jump to first page
2. Hierarchical arrays is a description of the way, increasing structural complexity arises in a developing organism. Any arbitrary developmental state of an organism may described by certain attributes. The next higher, more complex state not only incorporates all of the attributes of the several lower states but creates newer complexity. Despite an apparently continuous and uninterpreted developmental process, deeper consideration reveals marked discontinuities between hierarchical levels. Thus the phenotype is not merely a surface manifestation of the genotype which later suffices to regulate development. Rather the phenotype is the result of a hierarchy of self-regulatory processor that integrates epigenetic genomic factors into an orderly sequence of increasingly structured ontogenetic changes. www.indiandentalacademy.co m Jump to first page
3. Position or location of a cell within a developing organism is significant source of epigenetic information. Here instructive interactions between cells and the length of time a cell or cell mass occupies a specific location are among the factors held capable of locally providing epigenetic information and regulating genomic expression of cells in the immediate neighborhood. 4. Neurotrophic regulation of the muscle cell genome is another type of epigenetic information. Recently in studies of skeletal muscle fiber, following motor denervation, marked changes in many of the RNA sequences present in the muscle cell were noted. These data give strong support to the hypothesis that the motoneurons are able to control gene-expression of muscle www.indiandentalacademy.co fibers. m
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Development of Functional Matrix Hypothesis Periodic incorporation of advances in the biomedical, bioengineering and computer science allow the creation of increasingly more comprehensive revisions of the functional matrix theory. Recent work on two topics.
1. Cellular transduction of informational signals. 2. Biologic cellular network theory. Permit the presentation of this latest revision. www.indiandentalacademy.co m Jump to first page
The conceptual and anatomic basis of revised functional matrix hypothesis (FMH) More precisely the FMH claims that epigenetic, extraskeletal factors and processes are the prior, proximate, extrinsic and primary cause of all adaptive, secondary responses of skeletal tissues and organs. It follows that the responses of the skeletal unit (bone and cartilage) cells and tissues are not directly regulated by informational content of the intrinsic skeletal cell genome per se. Rather, this additional, extrinsic epigenetic information is created by functional matrix operations. This new version deals only with the responses to periosteal matrices and includes the molecular and cellular www.indiandentalacademy.co processes underlying the triad of active skeletal growth m processes deposition resorption and maintenance. Jump to first page
CONSTRAINTS OF THE FMH Initially FMH provided only qualitative narrative descriptions of the biologic dynamics of cephalic growth at the gross anatomic level. It had two explanatory constraints; 1. Methodologic constraint: Macroscopic measurements which are the techniques of point mechanics and arbitrary reference frames e.g. roentgenographic cephalometry permitted only method specific descriptions that cannot be structurally detailed. This constraint was removed by the continuum mechanic techniques of the finite element method (FEM) and of the www.indiandentalacademy.co related macro and boundary element methods. m Jump to first page
2. Hierarchical constraint; Even that versions descriptions did not extend “downward” to processes at the cellular, subcellular or molecular structural domains or extend “upwards” to the multicellular process by which bone tissues respond to lower level signals. All prior FMH version were “suspended” or “sandwiched” between these two hierarchical levels. FMH could not describe how extrinsic, epigenetic, functional matrix stimuli are transduced into regulatory signals by individual bone cells. How individual cells communicate to produce coordinated multi-cellular responses.
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Experimental and theoretical studies of bone adaptation consider only the unicellular, unimolecular or unigenomic levels and their results generally are not extensible to higher multicellular tissue levels. Significant disjunctions exist between the descriptions at each of the several levels of bone organization. In hierarchical theory the attributes of successively higher levels are not simply the sum of all lower attributes e.g. sum of all lower attributes of a bone cell cannot predict the higher attributes of a bone tissue. www.indiandentalacademy.co m Jump to first page
This newest FMH version presented herein transcends some hierarchical constraints and permits seamless descriptions at and between the several levels of bone structures and operation from the genomic to the organ level by the inclusions of two complementary concepts. 1. 2.
Mechanotransduction occurs in single bone cells. Bone cells are computational elements that function multicellularly as a connected cellular network.
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MECHANO TRANSDUCTON All vital cells are irritable and respond to alterations in their external environment. Mechanosensing processes enable a cell to sense and to respond to extrinsic loadings by using the processes of 1. Mechanoreception 2. Mechanotransduction Mechanoreception process: It transmits an extracellular physical stimulus into a receptor cell. MechanoTransduction process : It transduces or transform the stimulus’s energetic and/or informational content into an intracellular signal. www.indiandentalacademy.co Eg. Mechanoelectrical, mechanoechemical. m Jump to first page
Osseous MechanoTransduction When an appropriate stimulus parameter exceeds threshold values, the loaded tissue responds by the triad of bone cell adaptation processes like deposition, resorption and maintenance. Both osteocytes and osteoblasts are competent for intracellular stimulus reception and transduction and for subsequent intercellular signal transmission. Osteoblasts directly regulate bone deposition and maintenance and indirectly regulate osteoclastic resorption.
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This osseous mechano transduction is unique in four ways 1. Most other mechano sensory cells are cytologically specialized but bone cells are not. 2. One bone loading stimulus can evoke three adaptational responses whereas non-osseous processes generally evoke one. 3. Osseous signal transmission is aneural but all other use some afferent neural pathways. 4. The evoked bone adaptational responses are confined within each “bone organ” independently so there is no necessary “interbone” or organismal involvement. www.indiandentalacademy.co m Jump to first page
Osseous mechanotransduction translates the information content of a periosteal functional matrix stimulus into a skeletal cell signal, for eg. it moves information hierarchically downward to the osteocytes. There are two skeletal cellular mechano transduction processes.
1. Ionic
2. Mechanical
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IONIC OR ELECTRICAL PROCESSES This involves some processes of ionic transport through the bone cell (osteocytic) plasma membrane. Subsequent intercellular transmission of the created ionic or electrical signals which are computed by the operation of an osseous connected cellular network (CCN). The network’s output regulates the multicellular bone cell responses. Osteocytic, ionic MechanoTransduction may involve several possibly parallel cellular processes. Stretch Activated channel Plasma membrane stretch activated ion channels, a structure found in bone cells, which activated in strained osteocytes permit passage of certain sized ions or set of ions including K+, ca++, Na+, and Cs+. This ionic flow initiates intracellular electrical www.indiandentalacademy.co m as modulating membrane potentials as well as Ca++ events such ion flux. Jump to first page
Electrical Processes It includes. 1. Electromechanical - involving the osteocytic plasma membrane, contains voltage activated ion channels and transmembrane ion flow. Such ionic flows generate osteocytic action potentials capable of transmission through gap junctions. 2. Electrokinetic Bound and unbound electrical charges, many associated with the bone fluids in the several osseous spaces or compartments. Electrical effects fluid filled bone are electrokinetic i.e. streaming potential (SP). SP is a measure of the strain generated potential (SPG) of convected electric charges in the fluid flow of deformed bone. SPG of +-2millivolts can initiate both www.indiandentalacademy.co osteogenesis and osteocytic action potentials. m Jump to first page
Electric Field Strength Bone responds to exogenous electrical fields in an effective range of 1 to 10 micro volts per/cm strength that are on the order of those endogenously produced in bone tissue during normal (muscle) activity. MECHANICAL PROCESS Mechanical properties of the extracellular matrix influence cell behaviour. Loaded mineralized bone matrix tissue is deformed or strained. A series of extracellular macromolecular mechanical levers exits capable of transmitting information from the stained matrix to the bone cell nuclear membrane. www.indiandentalacademy.co m Jump to first page
The basis of this mechanism is the physical continuity of the transmembrane molecule integrin. This molecule is connected extracellular with the macromolecular collagen of the orgain matrix and intracellularly with the cytoskeletal actin. The actin’s molecules in turn are connected to the nuclear membrane at which site the action of the mechanical lever chain initiates a subsequent series of intra nuclear processes regulatory of genomic activity. www.indiandentalacademy.co m Jump to first page
Such a cytoskeletal lever chain connecting to the nuclear membrane can provide a physical stimulus able to activate the osteocytic genome. It is by such an interconnected physical chain of molecular levers the periosteal functional matrix activity may regulate the genomic activity of its strained skeletal unit bone cell including their phenotypic expression.
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THE ROLE OF BONE AN OSSEOUS CONNECTED CELLULAR NETWORK (CCN). All bone cells, expect osteoclasts are extensively interconnected by gap junctions that form an osseous CCN. Gap junction are found where the plasma membranes of a pair of markedly overlapping canalicular processes meet. Gap junctions also connect superficial to periosteal and endosteal osteoblast. All osteoblasts are similarly interconnected laterally. Vertically gap junctions connect periosteal osteoblasts with preosteoblastic cells and these in turn are similarly interconnected. Each CCN is a free www.indiandentalacademy.co synctium min a very real sense bone “hard wired�.
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Gap junctions permit intercellular transmission of ion and small molecules and electrical and fluorescent dye transmission. Gap junctions are electrical synapses- they permit bi-directional signal traffic e.g. biochemical, ionic. Mechanotransductively activated bone cells e.g. osteocytes can initiate membrane action potentials capable of transmission through interconnecting gap junctions. A CCN is operationally analogous to an “artificial neural network” in which massively parallel or parallel– distributed signal processing occurs. It computationally processes in a multi–processor network mode, the intercellular signal created by an electrical type of mechanotransduction of periosteal functional matrix stimulus. Subsequently, the computed network output informational signals move hierarchically “upward” to regulate the skeletal unit adaptational responses of the osteoblasts. www.indiandentalacademy.co m Jump to first page
In network theory these cells are organized into “Layers” an initial input, a final output, and one or more intermediate or hidden layers. Regardless of the actual physiological stipulatory process, each cell in any layer may simultaneously receive several “weighted’ inputs (stimuli). In the initial layer these represent the loadings within each cell independently all the weighted inputs are then summed. This sum is then compared within the cell against some liminal or threshold value. If this value is exceeded, an intracellular signal is generated i.e. successful mechanotransduction occurs. This signal is then transmitted identically to all the “hidden” layer cells (adjacent osteocytes) to each initial layer cell is connected by gap junctions. www.indiandentalacademy.co m Jump to first page
Next similar processes of weighted signal summation, comparison and transmission occur in these intermediate layers until the final layer (osteoblasts) cells are reached. The output of these anatomically superficial cells determines the site, rate, direction, magnitude and duration of the specific adaptive response i.e. deposition, resorption and/or maintenance of each cohort of osteoblasts. Information is not stored discretely in a CCN, rather it is distributed across all or part of the network and several types of information may be stored simultaneously. The instantaneous state of CCN is a property of the state of all its cells and of all their connections. Accordingly, the informational representational of CCN is assuring that the network is fault or error tolerant i.e. one or several inoperative cells causes little or no noticeable loss in network operations� matter of useful clinical significance. www.indiandentalacademy.co m Jump to first page
The CCNs show oscillation, i.e. iterative reciprocal signaling (feedback) between layers. This attribute enables them to adjustively self-organize, this behavior is related to the fact that biologic CCNs are not preprogrammed; rather they learn by unsupervised or epigenetic “training� a process probably involving structural or conformational changes in the cytoskeleton. The structurally more complex network attributes and behavior of a CCN gradually or epigenetically self-organize and emerge during operation. Gap junctions permitting bi-directional flow of information are the cytological basis for the oscillatory behavior of CCN. A skeletal CCN displays the following attributes:
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1. Developmentally, it is an untrained self-organized, selfadopting and epigenetically regulated system. 2. Operationally, it is a stable, dynamic system exhibits oscillatory behavior permitting feedback. 3. Structurally, an osseous CCN is non-modular i.e., variation in its organization permit discrete processing of different signals.
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THE ROLE OF PERIOSTEAL FUNCTIONAL MATRICES:- NEW INSIGHT The Morphogenetic primary of periosteal functional matrices on their skeletal unit is consensually accepted. As a muscular demand alters, e.g., myectomy, myotomy, neurectomy, exercise, hypertrophy, hyperplasia, atrophy, augmentation, or repositioning, the triad of active bone growth processes correspondingly adapts the form of its specifically related skeletal unit. Presently excluding the stimulation of neural afferents in muscle, tendon, and periosteum, extrinsic physical loading tend to deform bone tissue and to invoke skeletal unit (bone) adaptation responsive processes. A classic example is the regulation of coronoid process form by the temporalis muscle. The tension in www.indiandentalacademy.co the tendon of this contracted muscle, transmitted through m intertwined periosteal fibers inserted into subjacent bone, deforms Jump to first page the loaded skeletal unit.
Although some periosteal osteoblasts may be directly stimulated, extant data suggest osteocytic primary in mechano sensory processes. Their three dimensional array of extensive canalicular cell processes is architecturally well suited to sense deformation of the mineralized matrix. Strain plays a primary role in all bone adaptational or remodeling responses and is a competent stimulus. Skeletal muscle contraction is typical periosteal functional matrix loading event and frequency is one of its critical parameters. Of particular significance to the FMH is the close similarity of muscle stimulus frequencies to bone tissue response frequencies.
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MECHANO TRANSDUCTION: A TENTATIVE SYNTHESIS Ability of periosteal functional matrices to regulate the adaptive response of their skeletal units by ionic mechanotransduction processes is related to several factors. These are. 1. Normal muscle function strains attached bone tissue intermittently. 2. The dynamics of skeletal muscle contraction fit rather nicely with the energetic requirements for bone responsiveness. 3. The range of specific strain frequency harmonics of muscle dynamics are also those found to be morphogenetically competent (i.e. osteo-regulatory). www.indiandentalacademy.co m Jump to first page
4. Normal skeletal muscle activity produces intra osseous electric fields on the order of extrinsic fields to be similarly morphogenetic. 5. Bone cells may be stimulated by two mechanism – directly by strain activated plasma membrane channels and indirectly by electro kinetic phenomena. These factors strongly suggest that bone appears to be closely tuned to skeletal muscle i.e., skeletal units are tuned to their periosteal functional matrices.
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When both the ionic membrane and the mechanical (molecular lever) transductive processes are conceptually and operationally combined with the data of both electric field effects and of contraction frequency energetics, they provide a logically sufficient biophysical basis of support for the hypothesis of epigenetic regulation of skeletal tissue adaptation. These two processes share a common final pathway, i.e. they eventually produce signals regulatory of osteoblastic activity.
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THE GENOMIC THESIS The initial version of the FMH claiming epigenetic control of morphogenesis was based on macroscopic (gross) experimental, comparative and clinical data. Recently revised it now extends hierarchically from gross to microscopic (cellular and molecular) levels and identifies some epigenetic mechanisms capable of regulating genomic expression. The epigenetic or genomic problem is a dichotomy and dialectics is one analytical method for its resolution. The method consist of the presentation of two views, a thesis and an antithesis and of a resolving synthesis. www.indiandentalacademy.co m Jump to first page
The genomic thesis holds that the genome, from the moment of fertilization, contains all the information necessary to regulate (cause, control, direct). 1. The intra nuclear formation and transcription of mRNA and 2. Importantly, without the later addition of any other information, to regulate also all of the intracellular and intercellular processes of subsequent and structurally more complex cell, tissue, organ and organismal morphogenesis: Succinctly “all (Phenotype) features are ultimately determined by the DNA: sequence of the genome. www.indiandentalacademy.co m Jump to first page
In this thesis, morphogenesis is the predetermined readingout of an intrinsic and inherited genomic organismal blue print where, in addition to molecular synthesis, the genome also regulates the geometric attributes of cell, tissue, organ and organismal size, shape and location. The genomic thesis originated with classical (Chromosomal) Mendelian genetics. Recently molecular (gene) genetics extended the claims of the thesis to regulation of all aspects of Ontogeny (i.e. growth and development).
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The Genomic thesis in orofacial biology
Genomic thesis claims that prenatal cranio facial development is controlled by two inter related, temporarily sequential processes: 1. Initial regulatory (Homeobox) gene activity. 2. Subsequent activity of two regulatory molecular groups: growth factor families and steroid/thyroid/retinoic acid super family.
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For example “homeobox genes coordinate the development of complex craniofacial structures” and in “both normal and abnormal development much of the regulation of the development of virtually all of the skeletal and connective tissue of the face is dependent on a cascade of overlapping activity of homeobox genes”. It is claimed that regulatory molecules can (1) alter the manner in which homeobox genes coordinate cell migration and subsequent cell interactions that regulate growth (2) be involved in the “genetic variations causing, or contributing to the abnormal development of relatively common cranio facial malformations… perhaps modifying box gene activity”. www.indiandentalacademy.co m Jump to first page
Specific orthodontic implications of the genomic thesis includes claims that “poorly coordination- ordinated control of form and size of structures or group of structures (e.g. teeth, jaws) by regulator genes should do much to explain the very frequent mismatches found in malocclusions and other dentofacial deformities”. And “single regulatory (Homeobox) genes can control the development of complex structures… indicating that single genes can determine the morphology of atleast some complex structures” including “How characteristic noses or jaws are inherited from generation to generation”. In the genomic thesis morphogenesis is reduced to molecular synthesis. It proposes no pathways from molecules to morphogenesis. www.indiandentalacademy.co m Jump to first page
EPIGENETIC ANTITHESIS AND THE RESOLVING SYNTHESIS DEFINITIONS PROCESS: It is a series of actions or operations that lead toward a particular result. MECHANISM : It is the fundamental physical or chemical process involved in, or responsible for an action, reaction or other natural phenomenon. Mechanism underlie processes specific steps of the activation and deactivation of appropriate portions of the bone cell genome, associated with the triad of possible osteoblastic responses to loading (deposition, resorption or maintenance of bone tissue) are epigenetic mechanisms that control the genome. www.indiandentalacademy.co m Jump to first page
EPIGENETIC ANTITHESIS The genomic thesis is denied because it is both reductionist and molecular; that is descriptions of the causation (control, regulation) of all hierarchically higher and structurally more complex morphogenetic processes are reduced to explanations of mechanisms at the molecular (DNA) level. For example the genomic thesis of craniofacial ontogenesis passes directly from molecules to morphogenesis: directly from DNA molecules to adult morphology, ignoring the roles of the many epigenetic processes and mechanism competent to control (regulate, cause) the large number of intervening and increasingly more structurally complex, developmental stages particularly, and www.indiandentalacademy.co there are additional similarly reductionist views of odontogenesis. m Jump to first page
The epigenetic antithesis detailing both processes and mechanisms seeking to clarify the casual chain between genome & phenotype. Its goal is to identify and describe comprehensively the series of initiating biological processes and their related underlying (biochemical, biophysical) responsive mechanisms that are effective at each hierarchical level of increasing structural and operational complexity.
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CRANIOFACIAL EPIGENETICS Epigenetics refers to the entire series of interactions among cells and cell products, which leads to morphogenesis and differentiation. Thus all cranial development is “epigenetic� by definition. This views is supported here, despite continued expressions of genomic regulation of craniofacial morphogenesis. Epigenetic factors include 1. All of the extrinsic extra organismal macro environmental factors impinging on vital structures including mechanical loadings and electromagnetic fields. www.indiandentalacademy.co E.g. food,mlight, temperature Jump to first page
2. All of the intrinsic, intra organismal, biophysical, biomechanical, biochemical and bioelectric micro environmental events occurring on, in & between individual cells, extracellular materials and cells and extracellular substances. In terms of clinical of orthodontics, and of the FMH all therapy is applied epigenetics, and all appliances act as prosthetic functional matrices. Clinical therapeutics includes a number of epigenetic processes whose prior operations evoke a number of corresponding epigenetic mechanism. These in turn, underlie the observed processes of tissue adaptation by both skeletal unit and functional matrices.
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EPIGENETIC PROCESSES AND MECHANISM LOADING: - Among the numerous epigenetic factors influence the vertebrate face is mechanical loading. It is useful to consider epigenetic process of loading and some of the epigenetic mechanisms this process evokes is as follows. Loading per se While clinical observations usually are macroscopic, the loading, act microscopically, at molecular, and or cellular levels. Loadings are able to regulate several alternative molecular synthetic pathways of many tissues including bone. Mechanical loading is known to influence gene expression. Of FMH interest, extrinsic muscle skeletal loading can rapidly change 1) both articular cartilage intercellular molecular syntheses and mineralization. 2) Osteoblastic (skeletal unit) gene expression. www.indiandentalacademy.co Epigenetic loading process include gravitational variations that m evoke unique mechanism of molecular synthesis. Jump to first page
EXTRA CELLULAR MATRIX (ECM) DEFORMATION Musculoskeletal tissue loading inevitably deforms an extra cellular matrix (ECM) that is not developmentally inert. In several ways ECM regulates the formation, development and maintenance of all its included cells that synthesize the ECM. ECM can regulate multicellular tissue morphogenesis and contribute to genomic regulation of its enclosed cells. Cell – shape changes: - tissue loading can alter the cell shape and deforms intracellular constituents including cytoskeleton. The epigenetic process of changing cell shape invokes the epigenetic mechanisms of mechanotransduction of biophysical forces into genomic and morphogenetically regulatory signals. www.indiandentalacademy.co m
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Cells shape change process can also activate other epigenetic mechanisms, for eg stretch – activated ion channels in cartilage and other mechanically initiated cell signaling mechanisms. Cell shape change may lead to nuclear shape deformation which is a mechanism that can directly cause a consequent alteration of the mechanisms of genomic activity. Epigenetic cell signaling processes: - Can regulate genomic expression.
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Chains of intracellular molecular levers A second epigenetic cellular process begins with deformation of ECM. This matrix has an epigenetic regulatory role in morphogenesis, by virtue of integrin molecules that physically interconnect the several molecular components of the intra cellular and the extra cellular environment. The epigenetic mechanism evoked consists of a physical array of intracellular macromolecular chains, acting as levers, extending from the cell membrane to multiple specific sites on each chromosome. The molecular chain acts as an information transfer system between the extra cellular environment and the genome, transmitting signals generated by deformations of the ECM directly to the intra nuclear genome. Such informational www.indiandentalacademy.co transfer between cells and ECM is dynamic, reciprocal and m continuous. Jump to first page
EPIGENETIC LEVELS
REGULATION
OF
HIGHER
STRUCTURAL
At the tissue level, there are several causal, strain specific differences in bone tissue microstructure. Closely similar epigenetic mechanisms and processes are observed in the adaptational responses of all connective tissue, including cartilage, to loading. At the organ level, the ability of the processes of motion and of articular function to regulate joint morphology and physical activity processes regulate organismal skeletal adaptational responses. Other epigenetic processes affecting bone tissue include local vascular factors. www.indiandentalacademy.co m Jump to first page
REGULATION OF FUNCTIONAL MATRICES Mechanical loads regulate skeletal muscle (periosteal functional matrix) phenotype: and chronic muscle stimulation can change its phenotype. For muscle as for bone, mechanical epigenetic factors termed function (or exercise) significantly control musculoskeletal development and maintenance of structural and physiological attributes.
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A RESOLVING SYNTHESIS The fundamental argument of this resolving synthesis based on an analysis of causation argues that morphogenesis is regulated (controlled, caused) by the activity of both genomic and epigenetic processes and mechanisms. Both are necessary causes; neither alone are sufficient cause; and only their integrated activities provides the necessary and sufficient causes of growth and development. Genomic factors are considered as intrinsic and prior causes; epigenetic factors are considered as extrinsic and proximate causes. . www.indiandentalacademy.co m Jump to first page
COMPLEXITY AND SELF ORGANIZATION
Epigenetic processes and mechanisms are best explained as examples of Complexity theory (CT). CT provides description of the behaviour of complex biological systems that exist as “ensembles� of several tissues and organs and not as clusters of individual cells and extracellular substances. Such an ensemble (identical to a functional cranial component in the FMH) is termed here as a complex adaptive system (CAS). CT provides compact statistical descriptions of the collective growth behavior of such CAS continuity. www.indiandentalacademy.co m Jump to first page
An algorithm for control of such a CAS requires that it is able to alter itself in response to the epigenetic information produced by the system it is trying to control. In a CAS, minor changes in the epigenetic input can cause huge fluctuations in the morphological output. CT, as it utilized information theory, assumed that CAS processes information both genomic and epigenetic in a parallel, not a serial, manner, where most previous biological theories of development were based on the deterministic (genomically predetermined) classical mechanics, information theory and CT are probabilistic (epigenetically self organized and emergent) and are based www.indiandentalacademy.co on mthe methods of statistical mechanics. Jump to first page
The highly ordered morphological properties of adult complex biological system (e.g.; functional matrices and skeletal units) result from the operation of a series of spontaneous and self-organizing events can create phenotypic variability under constant genetic and other extra organismal epigenetic conditions. The operation of complexity can be suggested as follows: “ Environmental factors thus play a decisive role in all ontogenetic process. But it is the organism itself that, as an integrated system, dictates the nature of each and every developmental response. The living organism selforganizes on the basis of its own internal structuring, in continuous interaction with the environment in which it finds www.indiandentalacademy.co itself�. m Jump to first page
CURRENT CLINICAL FUNCTIONAL MATRIX
APPLICATIONS
OF
THE
Orthodontic therapy involves a change in 1.
Periosteal matrix(Teeth)
Skeletal Unit (Alveolar bone)
And/or 2. Capsular matrix (Orofacial Orthopedics)
Several Skeletal Units (The Jaws)
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Forces exerted on teeth or jaws do influence their functional matrices; and there are skill other matrices that determine the stability of the corrected malocclusions. To modify one functional matrix at the expense of another invites trouble. Relapse or perpetual retention is often the choice following orthodontic therapy.
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The following is a list of current clinical practices that reflect some aspect of functional matrix modification. 1. Frankels appliance:The larger part of the Frankels appliance is confined to the oral vestibule. The buccal shields and lip pads hold the buccal and labial musculature away from the teeth and investing tissues, eliminating any possible restrictive influence from the functional matrix.
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Frankels conceives his vestibular constructions as an artificial “ought-to-be” matrix that allows the muscles to exercise and adapt. It the buccinator - mechanism pressures are screened from the dentition significant expansion may occur in the intecanine dimension. This relieves the crowding often seen in the lower anterior segment which often leads to the removal of four first premolars in a fixed multi attachment mechanotherapy. The Frankel Regulator buccal shields prevent the pressure of the buccinator being exerted on the dento alveolar area both during deglutition and at rest. The net effect is outward expansion to the “ought-to-be” acrylic shield functional matrix.
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2. Enucleated orbit: The replacement of eyes with prostheses that are periodically replaced by larger versions promotes growth of the orbit. 3. Widening mid palatal sutures a form or orofacial orthopedics. 4. Repositioning of the maxillary segments of cleft patients—involve the change in macro units.
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5. Bilateral condylectomy—when anklosis of the condyles occurs in the growing child, condylectomy removes the restrains and allows the maximum development of the mandible in space. 6. Oblique bite plane – intra oral devices that hold the mandible in a protruded position for the purpose of stimulating condylar growth. 7. Monobloc functional therapy: Intra oral appliance used in conjunction with bone grafting to stimulate mandibular bone remodeling following subtotal mandibular resection. www.indiandentalacademy.co m Jump to first page
Conclusion: Using a popular phrase genomic and epigenetic processes are “apples and pears�. More correctly they are the examples of totally different types of causation-genomic formal cause and epigenetic efficient cause. Individually both are necessary causes but neither are sufficient causes alone. Together they provide both necessary and sufficient causes for the control (regulation) of morphogenesis.
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