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INDIAN DENTAL ACADEMY
Leader in continuing dental education
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 Introduction
 Normal histology of bone
 Normal histology of TMJ
 Normal histology of sutures
 Bone dynamics
 Differ...
Past 20 years have seen an increasing awareness of
the potential of functional appliances as a valuable
tool in armamentar...
 Improvement in orthopedic capabilities is

attributed to –
 Increased understanding of the biologic

principals of dent...
The goal of dentofacial orthopedic appliances is to
elicit a proprioceptive response in the stretch
receptors of the orofa...
 Osteoprogenitor cells :
 Stem cells of

mesenchymal origin.
 In adults these are
present over bone
surface ( on both
p...
 Osteoblast :

 Bone forming cells derived from

osteoprogenitor cells.
 They are found lining on growing
surface of th...
 Osteocyte :

 Cells of the mature bone.
 Lie in the lacunae of the

bone.
 Eosinophilic or light
basophilic cytoplasm...
 Osteoclast :
 Bone removing cells

essential for
maintaining proper
shape of the growing
bone.
 Large cells (20 to 100...
 Bone lining cells :
 These cells form a continuous epithelium like layer on

the bony surfaces where active bone deposi...
 Dense outer sheet of compact bone
 Central medullary cavity (bone marrow).

Haversian System
Haversian Canal
Osteocytes...
 Periosteum:
 Outer layer.
 Covered the entire surface of the

bone.
 Endosteum:
 Inner layer
 This membrane consist...
 A strong, highly

organized, well-mineralized
tissue, makes up more than
99% of the adult human
skeleton.
 The full str...
 It’s a newly formed bone.
 The collagen fibers are present

in bundles that appears to run
randomly in different
direct...
 Composite bone is an osseous tissue formed by the

deposition of lamellar bone within a woven bone lattice, a
process ca...
 The condyle of mandible

is composed of cancellous
bone covered by a thin
layer of compact bone.
 The trabeculae is
gro...
 During the period of

growth a layer of
hyaline cartilage lies
underneath the fibrous
covering of the
condyle. This
cart...
 Articular fibrous covering :
 The condyle as well as articular

trabeculae is covered by a
thick layer of fibrous tissu...
 Articular disc :

In young individuals the articular disc is composed of
dense fibrous tissue. The interlacing fibers ar...
 Articular capsule :
 Consists of an outer fibrous layer.
 The articular capsule is lined by synovial membrane

consist...
www.indiandentalacademy.com
Five Layer Vs Three Layer
Concept of suture
 Pritchard et al 1956
During Suture formation, there
are five layers i.e. cel...
Enlow 1968, Latham
1971, Kokich 1976
-Single fibrous
membrane
-No evidence of any
definitive layers

www.indiandentalacade...
Julius Wolff 1892, presented the law of bone transformation
which illustrates form and function relationship
Wolff stated,...
Culmann 1866 developed a
mathematical “trajectorial
theory” of bone
architecture based on the
principle of stress
directio...
Frost 1964, Parfitt 1979 defined pathways of remodeling
process by Quantum Theory
 Replacement of bone occurs in quantize...
Basset 1965 –
Bent bone can be straightened if bone is removed
from the tensile side and added to the compression
side. Th...
Frost 1964 - Flexural Neutralization Theory (FNT)
 Remodeling is not controlled by the polarity of tangential

wall stres...
Lanyon and Smith 1969
 First method of quantification of bone adaptation to

mechanical loading.
 The principle orientat...
Accurate assessment of the orthodontic or
orthopedic response to applied loads requires time
markers (bone labels) and phy...
1.
2.
3.
4.
5.

6.
7.
8.
9.

Mineralized sections
Polarized light
Fluorescent labels
Microradiography
Autoradiography
Nucl...
Mineralized sections
 Effective means of preserving structure and

function relationships accurately.
 Less processing d...
Polarized light


Detects the preferential
orientation of collagen fibers
in the bone matrix.



Loading conditions at t...
Fluorescent labels
 Permanently mark all sites

of bone mineralization at a
specific point of time.
 Histomorphometric a...
They fluoresce at different wavelengths (colors), six bone
labels can be used:
(1) tetracycline (10 mg/kg, bright yellow);...
Microradiography
 Assesses mineral

density patterns.
 Provides information

about the growth and
adaptation of the
skel...
Autoradiography
 Specific radioactive labels for

proteins, carbohydrates, and
nucleic acids are injected at a
known inte...
Nuclear volume morphometry
 Used for assessing the mechanism of osteogenesis

in orthodontically activated PDL’s
 Measur...
Cell kinetics
 Increase in nuclear size (A' to C) that occurs as

committed osteoprogenitor cells (A' cells) differentiat...
Finite element modeling (FEM)
 To assess stresses and strains within mechanically

loaded structures.
 The estimates of ...
Microelectrodes
 Detect electrical potential changes associated with

mechanical loading.
 Used to measure changes in el...
Modeling and Remodeling
Form and Function Relationship

www.indiandentalacademy.com
 Modeling :

In bone
modeling, independent
sites of resorption &
formation change the
form of bone (size or
shape or both...
Mineralized
bone surface
Mineralization

Mat
ure
oste
oclas
t

Osteoid

Preosteo
blast

www.indiandentalacademy.com
 Cutting & filling cones

The cutting /filling cone has a head of osteoclasts that cut through the bone
& a tail of osteo...
Harmonal & Metabolic
influences

Lamellar bone

MES – Minimum Effective Strain
www.indiandentalacademy.com

Woven
bone(rep...
Form and Function relation
Melvin Moss in 1960’s suggested that function of
soft tissues surrounding the dentofacial skele...
Factors Controlling Bone Remodeling
 Metabolic
 Growth harmone :
 Acts directly on human osteoblast like cells.
 Impor...
 IL 6 :
 The multifunctional cytokine IL 6 is involved in bone

remodeling.
 The regulation of growth factor interleuki...
 Cortisol :
 Involve in bone remodeling.
 Complex effect on bone tissue & bone cells.
 Increase cortisol level

Collag...
 Mechanical
 Peak load in microstrain<1000 uE, more remodeling
 Peak load in microstrain>2000 uE, less remodelling
(Whe...
www.indiandentalacademy.com
www.indiandentalacademy.com
The new bone formation appeared to be localized in
the primary attachment area of the posterior fibrous
tissue of the arti...
The posterior part of the articular disc, between the
postglenoid spine and the posterior part of the
condyle shows increa...
EXPERIMENTAL
•F in articular layer.
•M parallel to
articular surface.
•O are randomly
packed, and lacunae
are small, which...
Experimental
Pull-oriented
(arrow) and
stretched
fibroblasts
(F)

•Proliferation of F
and M
•O are packed
in large lacunae...


Mandibular protrusion resulted in the
osteoprogenitor cells being oriented in the
direction of the pull of the posterio...
Histologically :
 Marked resorptive activity of the compressed
zygomaticomaxillary and zygomaticotemporal sutures.
 Endo...
Jackson et al 1979
Sample – 4 Macaca nemestrina
Significant remodeling of all circummaxillary sutures
occured
Interimplant...
Histologically :
 Substantial widening with

deposition at the bony
margins and the long
collagenous bundles
traversing t...
Continuous Vs Intermittent
Brousseau and Kubisch 1977

Sample – 7 monkeys prepared with implants
headholders, splints and ...
 In both the groups, nearly all the dental changes relapsed
 Sutures simply began to show bone deposition with

downward...
Sox 9:
It is a high mobility group
type transcription factor
that
controls
the
differentiation
of
mesenchymal cells in
cho...
Hypertrophy and hyperplasia
of the prechondroblastic and
chondroblastic layers of the
condylar cartilage
Deposition of new...
Effects of Mandibular Retrusion
A mandibular retrusion by chin cup therapy in the
animal study revealed a reduced thicknes...
Control

Experimental
www.indiandentalacademy.com
Control

Experimental

3 days

7 days

www.indiandentalacademy.com

14 days
Dentofacial orthopedic appliances have been designed
 to affect neuro-muscular and functional pattern
 to impede or enha...
www.indiandentalacademy.com
www.indiandentalacademy.com
 The A-R-F remodeling cycle

The entire sequence from activation to formation phase is called SIGMA, &
www.indiandentalac...
Thank you
www.indiandentalacademy.com
Leader in continuing dental education

www.indiandentalacademy.com
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Histological changes in dentofacial orthopaedics1 /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.


Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
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Histological changes in dentofacial orthopaedics1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3.  Introduction  Normal histology of bone  Normal histology of TMJ  Normal histology of sutures  Bone dynamics  Different methods of studying bone dynamics  Factors affecting remodeling  Histological changes in dentofacial orthopaedics  Conclusion www.indiandentalacademy.com
  4. 4. Past 20 years have seen an increasing awareness of the potential of functional appliances as a valuable tool in armamentarium of orthodontist. They are important weapons in the arsenal and can accomplish results which are not possible with mechanical appliances. www.indiandentalacademy.com
  5. 5.  Improvement in orthopedic capabilities is attributed to –  Increased understanding of the biologic principals of dentofacial growth and development  Improved mechanical capability to effect skeletal change  Improvement in diagnostic techniques www.indiandentalacademy.com
  6. 6. The goal of dentofacial orthopedic appliances is to elicit a proprioceptive response in the stretch receptors of the orofacial muscles, ligaments and in sutures, and as a secondary response, to influence the pattern of bone growth corresponding to support a new functional environment for the developing dentofacial complex www.indiandentalacademy.com
  7. 7.  Osteoprogenitor cells :  Stem cells of mesenchymal origin.  In adults these are present over bone surface ( on both periosteal & endosteal aspect).  They can proliferate & convert themselves into osteoblast whenever there is need for bone formation. www.indiandentalacademy.com
  8. 8.  Osteoblast :  Bone forming cells derived from osteoprogenitor cells.  They are found lining on growing surface of the bone.  Nucleus is ovoid & euchromatic.  The cytoplasm is basophilic because of the presence of rough endoplasmic reticulum.  Osteoblast is responsible for laying down the organic matrix of bone (glycosaminoglycanes, proteoglyca ns) including collagen fibers.  Also responsible for calcification of matrix. www.indiandentalacademy.com
  9. 9.  Osteocyte :  Cells of the mature bone.  Lie in the lacunae of the bone.  Eosinophilic or light basophilic cytoplasm.  Function : I. Maintain the integrity of lacunae and canaliculi. Thus keep the channels open for diffusion of nutrition. II. Removal or deposition of matrix and calcium when required. WB – Woven bone LB – Lamellar bone ER – Endoplasmic reticulum www.indiandentalacademy.com
  10. 10.  Osteoclast :  Bone removing cells essential for maintaining proper shape of the growing bone.  Large cells (20 to 100 µm).  Numerous nuclei (upto 20 or more). www.indiandentalacademy.com
  11. 11.  Bone lining cells :  These cells form a continuous epithelium like layer on the bony surfaces where active bone deposition or removal is not taking place.  These cells are flattened.  Present on periosteal as well as endosteal surface. www.indiandentalacademy.com
  12. 12.  Dense outer sheet of compact bone  Central medullary cavity (bone marrow). Haversian System Haversian Canal Osteocytes www.indiandentalacademy.com
  13. 13.  Periosteum:  Outer layer.  Covered the entire surface of the bone.  Endosteum:  Inner layer  This membrane consists of a layer of loose connective tissue, with osteogenic cells that physically separates the bone surface from the marrow within www.indiandentalacademy.com
  14. 14.  A strong, highly organized, well-mineralized tissue, makes up more than 99% of the adult human skeleton.  The full strength of lamellar bone is not achieved until approximately 1 year after completion of active treatment. www.indiandentalacademy.com
  15. 15.  It’s a newly formed bone.  The collagen fibers are present in bundles that appears to run randomly in different directions , interlacing with each other . That’s why it is called woven bone.  It is compacted to form composite bone, remodeled to lamellar bone, or rapidly resorbed if prematurely loaded. www.indiandentalacademy.com
  16. 16.  Composite bone is an osseous tissue formed by the deposition of lamellar bone within a woven bone lattice, a process called cancellous compaction.  Composite bone is an important intermediary type of bone in the physiologic response to orthodontic loading. www.indiandentalacademy.com
  17. 17.  The condyle of mandible is composed of cancellous bone covered by a thin layer of compact bone.  The trabeculae is grouped in such a way that they radiate from the neck of mandible & reach the cortex at right angles. Thus giving maximum strength to the condyle. www.indiandentalacademy.com
  18. 18.  During the period of growth a layer of hyaline cartilage lies underneath the fibrous covering of the condyle. This cartilaginous grows by apposition from the deepest layer of the covering connective tissue . At the same time deepest layer is replaced by bone. www.indiandentalacademy.com Fibrous covering Reverse cell zone Secondary cartilage Bone trabeculae
  19. 19.  Articular fibrous covering :  The condyle as well as articular trabeculae is covered by a thick layer of fibrous tissue.  The fibrous layer covering the articular surface of temporal bone is thin in articular fossa & thickened rapidly in the posterior slope of articular trabeculae.  It has two fibrous layer : o Inner layer – fibers are arranged in right angle to bony surface. o Outer layer - fibers are arranged parallel to bony surface. www.indiandentalacademy.com Bone Inner fibrous layer Outer fibrous layer Upper joint space Articular disc
  20. 20.  Articular disc : In young individuals the articular disc is composed of dense fibrous tissue. The interlacing fibers are straight & tightly packed. www.indiandentalacademy.com
  21. 21.  Articular capsule :  Consists of an outer fibrous layer.  The articular capsule is lined by synovial membrane consists of internal cells which are of three types: o First : rich in RER & is called fibroblast like cell or B cell. o Second : rich in golgi complex contains little or no RER called macrophage like cell or A cells. o Third : this has a cellular morphology between A & B cells. www.indiandentalacademy.com
  22. 22. www.indiandentalacademy.com
  23. 23. Five Layer Vs Three Layer Concept of suture  Pritchard et al 1956 During Suture formation, there are five layers i.e. cellular and fibrous layer of both bones and additional intervening loose mesenchymal layer.  Weinman & Sicher (1955) and Moss (1957) – Three layered concept i.e two interconnecting fibrous layer with a highly cellular middle zone www.indiandentalacademy.com
  24. 24. Enlow 1968, Latham 1971, Kokich 1976 -Single fibrous membrane -No evidence of any definitive layers www.indiandentalacademy.com
  25. 25. Julius Wolff 1892, presented the law of bone transformation which illustrates form and function relationship Wolff stated, every change in form and function of bone, or in there function alone, is followed by certain definite changes in their internal architecture and equally definitive secondary alterations in their external conformation in accordance with mathematical laws www.indiandentalacademy.com
  26. 26. Culmann 1866 developed a mathematical “trajectorial theory” of bone architecture based on the principle of stress directions in more homogeneous materials Rodan and Martin 1981, Komn et al and Erickson 1988 - osteoclast differentiation may require interaction with osteoblast or their precursors www.indiandentalacademy.com
  27. 27. Frost 1964, Parfitt 1979 defined pathways of remodeling process by Quantum Theory  Replacement of bone occurs in quantized packets through the coordinated action of organized cellular units.  These units were called basic multicellular unit or BMU. www.indiandentalacademy.com
  28. 28. Basset 1965 – Bent bone can be straightened if bone is removed from the tensile side and added to the compression side. This implies that remodeling is controlled by the polarity of the tangential wall stress: tensile stress favor osteoclastic activity while compression stress favor osteoblastic activity. www.indiandentalacademy.com
  29. 29. Frost 1964 - Flexural Neutralization Theory (FNT)  Remodeling is not controlled by the polarity of tangential wall stress (i.e. compression or tension) but by the tendency of the applied load to alter the relative curvature of the surface  Increased surface convexity stimulate osteoclastic activity and decreased surface convexity favored osteoblastic activity www.indiandentalacademy.com
  30. 30. Lanyon and Smith 1969  First method of quantification of bone adaptation to mechanical loading.  The principle orientations of trabeculae coincides with the principle compressive and principle tensile strain directions. This was the first quantitative experimental demonstration of “Wolff’s law” www.indiandentalacademy.com
  31. 31. Accurate assessment of the orthodontic or orthopedic response to applied loads requires time markers (bone labels) and physiologic indices (deoxyribonucleic acid [DNA] labels, histochemistry, and in situ hybridization) of bone cell function. www.indiandentalacademy.com
  32. 32. 1. 2. 3. 4. 5. 6. 7. 8. 9. Mineralized sections Polarized light Fluorescent labels Microradiography Autoradiography Nuclear volume morphometry Cell kinetics Finite element modeling (FEM) Microelectrodes www.indiandentalacademy.com
  33. 33. Mineralized sections  Effective means of preserving structure and function relationships accurately.  Less processing distortion occurs.  The inorganic mineral and organic matrix can be studied simultaneously.  Even without bone labels, micro radiographic images of polished mineralized sections provide substantial information about the strength, maturation, and turnover rate of cortical www.indiandentalacademy.com bone.
  34. 34. Polarized light  Detects the preferential orientation of collagen fibers in the bone matrix.  Loading conditions at the time of bone formation dictates the orientation of the collagen fibers to best resist the loads to which the bone is exposed. www.indiandentalacademy.com
  35. 35. Fluorescent labels  Permanently mark all sites of bone mineralization at a specific point of time.  Histomorphometric analysis is an effective method of determining the mechanisms of bone growth and functional adaptation www.indiandentalacademy.com
  36. 36. They fluoresce at different wavelengths (colors), six bone labels can be used: (1) tetracycline (10 mg/kg, bright yellow); (2) calcein green (5 mg/kg, bright green); (3) xylenol orange (60 mg/kg, orange); (4) alizarin complexone (20 mg/kg, red); (5) demeclocyclin (10 mg/kg, gold); and (6) oxytetracycline (10 mg/kg, greenish yellow) www.indiandentalacademy.com
  37. 37. Microradiography  Assesses mineral density patterns.  Provides information about the growth and adaptation of the skeletal sites most affected by orthodontic and facial orthopedic treatment. S : Remodeled secondary osteons www.indiandentalacademy.com
  38. 38. Autoradiography  Specific radioactive labels for proteins, carbohydrates, and nucleic acids are injected at a known interval before tissue sampling is done.  3H-thymidine labeling of cells synthesizing DNA (S phase cells)  3H -proline labeling of newly formed bone matrix. O – original bone P – PDL N – New bone www.indiandentalacademy.com → - Radioactive labels
  39. 39. Nuclear volume morphometry  Used for assessing the mechanism of osteogenesis in orthodontically activated PDL’s  Measuring the size of the nucleus is a cytomorphometric procedure for assessing the stage of differentiation of osteoblast precursor cells. www.indiandentalacademy.com
  40. 40. Cell kinetics  Increase in nuclear size (A' to C) that occurs as committed osteoprogenitor cells (A' cells) differentiate to preosteoblasts (C cells) is the rate-limiting step in osteoblast histogenesis.  A localized mechanical stimulus (orthodontic force), creates a reciprocal pulse of A - A’ and C - D waves that generate huge numbers of osteoblasts. www.indiandentalacademy.com
  41. 41. Finite element modeling (FEM)  To assess stresses and strains within mechanically loaded structures.  The estimates of initial stress have been useful for defining the mechanical conditions for initiating orthodontically induced bone resorption and formation. www.indiandentalacademy.com
  42. 42. Microelectrodes  Detect electrical potential changes associated with mechanical loading.  Used to measure changes in electrical potential in the extracellular space of the PDL during the initial response to orthodontic force.  Widened areas of the PDL have a more negative electrical potential, and compressed areas have a more positive electrical potential. www.indiandentalacademy.com
  43. 43. Modeling and Remodeling Form and Function Relationship www.indiandentalacademy.com
  44. 44.  Modeling : In bone modeling, independent sites of resorption & formation change the form of bone (size or shape or both).  Remodeling : In bone remodeling a specific coupled sequence of resorption & formation occurs to replace previously existing bone www.indiandentalacademy.com
  45. 45. Mineralized bone surface Mineralization Mat ure oste oclas t Osteoid Preosteo blast www.indiandentalacademy.com
  46. 46.  Cutting & filling cones The cutting /filling cone has a head of osteoclasts that cut through the bone & a tail of osteoblasts that form a new secondary osteon. www.indiandentalacademy.com
  47. 47. Harmonal & Metabolic influences Lamellar bone MES – Minimum Effective Strain www.indiandentalacademy.com Woven bone(repair)
  48. 48. Form and Function relation Melvin Moss in 1960’s suggested that function of soft tissues surrounding the dentofacial skeleton (i.e. Functional Matrix) determines the form of the underlying Skeletal Units. Many orthopedic appliances used in Functional Jaw Orthopedics, alter the function of various function matrices resulting in the alteration in form of skeletal units www.indiandentalacademy.com
  49. 49. Factors Controlling Bone Remodeling  Metabolic  Growth harmone :  Acts directly on human osteoblast like cells.  Important in determining in longitudinal bone growth & bone remodeling.  Stimulate the proliferation of cultured OB, some (not all) studies says that GH regulate the differentiation of cultures OB.  IGF-I :  Important in bone remodeling.  It is embedded in the bone matrix & can act as a coupling factor between bone formation & resorption. www.indiandentalacademy.com
  50. 50.  IL 6 :  The multifunctional cytokine IL 6 is involved in bone remodeling.  The regulation of growth factor interleukin 6 (IL-6) may be critical for the control of bone resorption during menopause.  IL-6 is needed for the production of osteoclasts.  Effect of Oestrogen on GH :  Decrease in oestrogen level after cessation of ovarian function leads to postmenopausal osteoporosis.  Estrogen – increases activation frequency www.indiandentalacademy.com
  51. 51.  Cortisol :  Involve in bone remodeling.  Complex effect on bone tissue & bone cells.  Increase cortisol level Collagen expression Collagenase expression Degradation of Type I collagen Decrease bone formation  PTH :  Increases osteoblastic activation frequency. www.indiandentalacademy.com
  52. 52.  Mechanical  Peak load in microstrain<1000 uE, more remodeling  Peak load in microstrain>2000 uE, less remodelling (Where uE represents percent deformation X 10-4) The mechanostat concept of Frost as defined by Martin & Burr (1990) The peak strain history determines whether www.indiandentalacademy.com atrophy, maintenance, hypertrophy, fatigue failure occurs.
  53. 53. www.indiandentalacademy.com
  54. 54. www.indiandentalacademy.com
  55. 55. The new bone formation appeared to be localized in the primary attachment area of the posterior fibrous tissue of the articular disc in the direction of tension exerted by the stretched fibers of the posterior part of the disc. www.indiandentalacademy.com
  56. 56. The posterior part of the articular disc, between the postglenoid spine and the posterior part of the condyle shows increased in thickness and active cellular and connective tissue response associated with numerous enlarged fibroblasts in active stage. This response stabilize the anterior condylar displacement www.indiandentalacademy.com
  57. 57. EXPERIMENTAL •F in articular layer. •M parallel to articular surface. •O are randomly packed, and lacunae are small, which indicates old bone F in articular layer become oriented toward pull (arrow) F and M are all dragged towards pull (arrow). F are obviously flattened and lengthened by stretching pull. CONTROL 3rd Day 7th Day 14th Day F : Fibroblast , M : Mesenchymal cells, O : Osteocytes www.indiandentalacademy.com F and M are arranged in orderly fashion F & M are arranged parallel to articular surface
  58. 58. Experimental Pull-oriented (arrow) and stretched fibroblasts (F) •Proliferation of F and M •O are packed in large lacunae, indicates bone deposition. F and M remain oriented in direction of pull Control 14th day 21th day 30th day www.indiandentalacademy.com Fibroblasts are round and randomly packed F&M arranged in line with articular surface Cells are still packed parallel to articular surface
  59. 59.  Mandibular protrusion resulted in the osteoprogenitor cells being oriented in the direction of the pull of the posterior fibers of the disc and also resulted in a considerable increase in bone formation (wolfs law) in the glenoid fossa . www.indiandentalacademy.com
  60. 60. Histologically :  Marked resorptive activity of the compressed zygomaticomaxillary and zygomaticotemporal sutures.  Endosteal and periosteal compensatory deposition. Control Experimental IRREGULAR PATH OF SUTURE REGULAR PATH OF SUTURE www.indiandentalacademy.com
  61. 61. Jackson et al 1979 Sample – 4 Macaca nemestrina Significant remodeling of all circummaxillary sutures occured Interimplant distance showed 3 – 5 times separation in the sutures www.indiandentalacademy.com
  62. 62. Histologically :  Substantial widening with deposition at the bony margins and the long collagenous bundles traversing the sutural space  Retaining the increased sutural width allowed bone to fill in at the sutural margins, narrowing the sutural gap and providing more stable result. Control Experimental www.indiandentalacademy.com
  63. 63. Continuous Vs Intermittent Brousseau and Kubisch 1977 Sample – 7 monkeys prepared with implants headholders, splints and headgears Amount of skeletal change was greater in animals with continuous force Inter-implant distance in continuous growth showed 2.4 times more skeletal change and about 2 times more dental changes than the intermittent group www.indiandentalacademy.com
  64. 64.  In both the groups, nearly all the dental changes relapsed  Sutures simply began to show bone deposition with downward and forward growth of maxilla  The greater the retraction of maxilla achieved during the treatment, the greater the net retraction maintained in post-treatment phase www.indiandentalacademy.com
  65. 65. Sox 9: It is a high mobility group type transcription factor that controls the differentiation of mesenchymal cells in chondrocytes by directly activating gene expression for Type II Collagen www.indiandentalacademy.com
  66. 66. Hypertrophy and hyperplasia of the prechondroblastic and chondroblastic layers of the condylar cartilage Deposition of new bone also occurred along the anterior surface of the postglenoid spine. www.indiandentalacademy.com
  67. 67. Effects of Mandibular Retrusion A mandibular retrusion by chin cup therapy in the animal study revealed a reduced thickness of the prechondroblastic zone and a decrease in the number of dividing cells. Chin cup treatment had a retarding effect on mandibular growth. www.indiandentalacademy.com
  68. 68. Control Experimental www.indiandentalacademy.com
  69. 69. Control Experimental 3 days 7 days www.indiandentalacademy.com 14 days
  70. 70. Dentofacial orthopedic appliances have been designed  to affect neuro-muscular and functional pattern  to impede or enhance growth vector or growth magnitude  to achieve tooth movement .  “ The growth of the pattern is proportional. This means that the disharmony is present from before birth ; it becomes neither better nor worse. It cannot be changed by treatment. The teeth and the alveolar process constitute the only area of the face whose change may be expected or induced.” Brodie,1946 www.indiandentalacademy.com
  71. 71. www.indiandentalacademy.com
  72. 72. www.indiandentalacademy.com
  73. 73.  The A-R-F remodeling cycle The entire sequence from activation to formation phase is called SIGMA, & www.indiandentalacademy.com requires about 4 months in humans.
  74. 74. Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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