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• Growth is a general term implying an increase in magnitude. Development is a maturational process.It is important for us to know and understand this biologic process of growth &development because at some point of time we manipulate growth by intervening the course of the control process of growth by giving func- appliance & orthopedic devices. Morphogenesis- ie growth controlwww.indiandentalacademy.com process tends to achieve a
balance between growing parts. But as development progress balance can never be actually achieved because itself creates ongoing.This process starts at childhood, to adult-hood & goes on till old age,but the process is slowed down as age increases
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• Facial growth operates with two basic kinds of growth movementa) remodeling b) displacement • The process of remodeling is placed by the composite of soft tissue relating to each of the bones. • Displacement: As bone enlarges it is carried away from other bones. This creates space with in which bony enlargement takes place called “Displacement” also called www.indiandentalacademy.com translation.
VARIOUS GROWTH THEORIES THAT HAVE BEEN PROPOSED • • • • •
Genetic control theory (Bordie 1941) Cartilage directed growth theory (Scott 1953) Sutural theory functional matrix theory (Moss 1960) Servo system theory (Petrovic 1974)
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• Functional matrix theory(Moss 1960) proffit Moss says if neither bone nor cartilage were determinant for growth of craniofacial skeleton,the control would lie in the adjacent soft tissues.He theorizes that growth of the face occurs as a response to functional needs & is mediated by the soft tissues in which it is embedded. HE theorizes that growth of the maxilla & mandible occurs due to enlargement of nasal& oral cavities www.indiandentalacademy.com
• FMT (Graber & Petrovic) Regional & local factors play a role in cranio facial morphogenesis. It says that the growth of bone & cartilage seems to be a compensatory response to FM growth.the functional matrix include muscles, nerves,glands, teeth,blood vessels etc. The growth of functional matrix is primary; the growth of skeletal unit is secondary www.indiandentalacademy.com
FUNCTIONAL CRANIAL ANALYSIS Composed of two parts • a functional matrix • a skeletal unit Skeletal unit - micro skeletal unit - macro skeletal unit Functional matrix - periosteal matrices - capsular matrices www.indiandentalacademy.com
PERIOSTEAL MATRICES • For eg-functional cranial component consisting of temporalis muscle &the coronoid process. • Experimental removal of the temporalis muscle results in an actual diminution of coronoid process size &shape. • Also hypertrophy or hyperactivity of the temporalis muscle produced increased size www.indiandentalacademy.com of coronoid process
CAPSULAR MATRICES Functional matrices plus skeletal units are organized in the form of cranial capsules. 2 cranial capsules -neuro cranial capsule & oro facial capsules . The expansion of the neurocranial capsule is always proportional to the increase in neural mass www.indiandentalacademy.com
ORO FACIAL MATRICES • All functional cranial component of the facial skull arise, grow and are maintained with in the oro facial capsule. This capsule surronds & protects the oro-nasopharyngeal functioning spaces.It is the volumetric growth of these spaces which is the primary morphogenetic event in facial skull growth www.indiandentalacademy.com
• For the demonstration of the integrated activity of periosteal & capsular matrices in facial growth, mandibular growth is taken • it is a combination of the morphologic effects of both capsular & periosteal matrices. Capsular growth causes an expansion of the capsule as a whole.the enclosed macro skeletal unit is passively & secondarily translated in space to successively new positions.the periosteal matrices related to these mandibular microskeletal units also respond to this www.indiandentalacademy.com volumetric expansion
GENETIC, EPIGENETIC &CAUSATION • Combination of genomic &epigenetic factors is a necessary cause of cranio facial growth • Biologically causation is produced by 1.a set of cells & X”tra cellularsubstance{material 2 a program encoded in the genome [format 3 an immediately antecedent, epigenetic event[efficient] 4 some consequent use {final} www.indiandentalacademy.com
EPIGENETIC HYPOTHESIS • The term epigenetic is used to describe the sum of all bio mechanics, bio electrical, bio chemical & bio physical parameters produced by functioning cells ,tissues, organs &organisms • these factors are thought to act on the genome to regulate all developmental process www.indiandentalacademy.com
FM HYPOTHESIS -REVISITED I • Mechano transduction is a process of cell signal transfer • Biologic network theory explains the net work of bone cells & how they interact to the signals. • There are several mechano transductive processmechanoelectrical & mechanochemical which ever used,bone adaptation requires the subsequent intercellular transmission of the transduced www.indiandentalacademy.com signals.
• Mechano sensing processes enable a cell to sense and to respond to extrinsic loadings by using the processes of mechano reception and of the mechano transduction. Mechano transduction transmits the extra cellular physical stimulus into a receptor cell where as the mechano reception transforms the stimulus’s energetic and/or informational content into an intracellular signal. • Osseous mechano transduction • ionic or electrical process www.indiandentalacademy.com • mechanical process
THE ROLE OF AN OSSEOUS CONNECTED CELLULAR NETWORK FMH REVISITED 2 • All bone cells except osteoclasts, are extensively inter connected by gap junctions that form an osseous CCN • Gap Junctions are found where the plasma membrane of a pair of markedly overlapping canalicular process meet.They also connect superficial osteocytes to periosteal & endosteal osteoblasts . www.indiandentalacademy.com
• Mechano transductively activated bone cells eg osteocytes, can intiate membrane action potentials capable of transmission through interconnecting gap junctions • In net work theory the cells are arranged into “layers”,an intial input, a final output & a more intermediate or “hidden”layers.Each cell in any layer may simultaneously receive several “weighted” inputs (stimuli) • When an intra cellular signal is generated it is transmitted identically to all the hidden layer cells to which each intial layer cell is connected by Gap www.indiandentalacademy.com junction.
• The similar processes of weighted signal summation, comparison & transmission occur in the intermediate layers until the final layer cells are reached . The out put of these anatomically superficial cells determines the site, rate, direction, magnitude and duration of the specific adaptive response; ie deposition, resorption and\or maintenance,of each cohort of osteoblast • CCN show oscillation. Gap junctions, permitting bidirectional flow of information, are the cytological basis for the oscillatory behavior of CCN www.indiandentalacademy.com
A skeletal CCN displays the following attributes • Developmentally, it is an untrained selforganised &self-adapting and epigenetically regulated system. • Operationally,it is a stable, dyanamic system that exhibits oscillatory behavior permitting feedback • Structurally, an osseous CCN is non modular www.indiandentalacademy.com
FMH REVISITED-3 THE GENOMIC THESIS • According to this theory,the whole series of operations to be carried out, the order and site of synthesis and their co-ordination are all written down in the nucleic acid message • this thesis holds that from the moment of fertilization,the genome contains all information necessary to regulate - 1. The intra nuclear formation &transcription of RNA . 2.With out any external factor regulate intracellular &intercellular activities of cell tissues and organs & all phenotypic www.indiandentalacademy.com features are expressed by DNA
FMH Revisited 4 EPIGENETIC ANTI THESIS AND THE RESOLVING SYNTHESIS • The epigenetic anti thesis,detailing both processes & mechanisms,integrative,seeking to clarify the causal chain between genome and phenotype. Its goal is to identify & 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 &operational complexity. www.indiandentalacademy.com
EPIGENETIC PROCESSES AND MECHANISMS • Loading • Extra cellular matrix deformation • Cellshape changes
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A RESOLVING SYNTHESIS BETWEEN GENETIC & EPIGENETIC THEORIES • Individually both are necessary causes, but neither are sufficient causes alone. Together they provide both the necessary and sufficient causes for the control of morphogenesis.Nevertheless,epigenetic processes and events are the immediately proximate causes of development, and as such they are the primary agencies. www.indiandentalacademy.com
CONCLUSION www.indiandentalacademy.com
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