EVOLUTION OF
THEORIES
•
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indian...
Craniofacial biology as “Normal
Science”
David S. Carlson

The Structure of Scientific Revolutions – Thomas Kuhn (1970)
NO...
paradigm
 Model or concept
 A conceptual scheme that encompasses individual theories and
is accepted by a scientific com...
 SCIENTIFIC COMMUNITY – group characterized by its
consensus about a paradigm & commitment to relate that
paradigm to the...
www.indiandentalacademy.com

5
Changing paradigms
INTRINSIC GENETIC FACTORS

FUNCTIONAL FACTORS
EPIGENETIC FACTORS

www.indiandentalacademy.com

6
1920-1940
 Study of craniofacial skeleton with no consideration to
function –
- Anthropologic craniometry
-Racial analysi...


Studies based on –
Comparative anatomy,
Craniometrics,
Radiographic cephalometrics



Anatomic intuition & extrapolati...
Genomic paradigm
 Genetically determined – so growth pattern invariant.

 “norms” or “standards”
 Treatment of bones of...
1940-1960


Increase in experimental animal research.



Methodologic change- Technological developments:1.

Use of Radi...
www.indiandentalacademy.com

11


The end of 1950’s – 2 approaches within genomic
paradigm (Krogman – 1974) –

1. COMPREHENSIVE APPROACH
2. STRUCTUROFUNT...
Structurofunctional Approach:

 Experimental & analytic
 Concentrated more on “cause and effect
relationships”
 Effect ...
 The end of 1950’s -genomic paradigm put into question

 Periosteal and sutural bone growth - removed from
genomic parad...
1960-1980
 Early 1960s- ‘period of Revolution’.

 Development of alternative paradigm mostly
associated with – Melvin Mo...
www.indiandentalacademy.com

16
 “Functional Matrix Hypothesis”- a topic of
theoretical debate involving people likeMoorrees(1972)
Koski(1972)
Wayne Wats...
www.indiandentalacademy.com

18
 2 Paradigms :

1. Genomic--Exists primarily on the strength of the
belief that facial growth and form should be encoded
...
Theories of growth
 Different theories differ in the location at which
genetic control is established.
 3 major theories...
Growth site versus growth centre
Cranial growth centers: Facts or fallacies? – Koski
AJO-DO 1968 Aug (566-583)
BAUME:
Grow...
Growth site: regions of periosteal or sutural bone
formation and modeling resorption adaptive to
environmental influences....
Sutural dominance theory
 SICHER – studies using vital dyes – sutures caused
much of growth
 “….the primary event in sut...
 Sicher ascribes equal value – osteogenic tissues,
cartilage, sutures & periosteum.

www.indiandentalacademy.com

24
www.indiandentalacademy.com

25
 2 differing views concerning the structure of the
sutures –
1. Three-layer structure:
- Connective tissue between the tw...
2. Five-layer structure :
-Each bone at the suture has its own two-layer
periosteum covering + opposing surfaces of the
bo...
Evidence against sutural theory
1. Subcutaneous autotransplants of the
zygomaticomaxillary suture area in the guinea pig h...
CONCLUSION:

 Sutures are growth sites not centres.
 Adaptive, compensatory or secondary growth.

www.indiandentalacadem...
Cartilaginous theory
SCOTT’S HYPOTHESIS:

 Intrinsic growth-controlling factors in cartilage &
periosteum.
 Sutures are ...
www.indiandentalacademy.com

31
Cranial base synchondroses

 Removal of spheno-occipital synchondrosis - results in an
arrest of growth in length of the ...
Endochondral cranial base – lesser response to brain
growth than intramembranous cranial vault.
Primary centres of growt...
 Endochondral ossification at the synchondrosesonly a response to external stimuli?
 Cartilage- lacks same amount of ind...
Nasal septal cartilage
 Scott- primary cartilage in nasal septum – primary
mechanism for growth of nasomaxillary complex....
 Histologic examination - endochondral ossification at the septoethmoidal junction and area of proliferation at the vomer...
 Experimental excision of the nasal septum affects the growth
of the upper face considerably - due to trauma.
 Nasal sep...
 Arrhinencephalic 9-month-old child (with the septum
missing) - resorption and apposition processes in the
bony palate no...
Condylar cartilage
 Growth of the condylar cartilage is responsible for the
anteroposterior growth of the mandible- prima...
 Scott- growth of the condylar cartilage enables the
condyle "to grow upwards and backwards so as to
maintain the contact...
www.indiandentalacademy.com

41
 Studies involving the use of metallic implants - actual
growth of the condyle is sometimes upward and
backward and somet...
www.indiandentalacademy.com

43
Thank you

For more details please visit

www.indiandentalacademy.com

www.indiandentalacademy.com

44
Upcoming SlideShare
Loading in …5
×

Theories /certified fixed orthodontic courses by Indian dental academy

506 views

Published on


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
0091-9248678078

Published in: Education
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
506
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
5
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

Theories /certified fixed orthodontic courses by Indian dental academy

  1. 1. EVOLUTION OF THEORIES • INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com 1
  2. 2. Craniofacial biology as “Normal Science” David S. Carlson The Structure of Scientific Revolutions – Thomas Kuhn (1970) NORMAL SCIENCE: “Research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges as supplying the foundation for its further practice.” www.indiandentalacademy.com 2
  3. 3. paradigm  Model or concept  A conceptual scheme that encompasses individual theories and is accepted by a scientific community as a model and foundation for further research. www.indiandentalacademy.com 3
  4. 4.  SCIENTIFIC COMMUNITY – group characterized by its consensus about a paradigm & commitment to relate that paradigm to the rest of the natural world.  Conflict between scientific communities.  SCIENTIFIC REVOLUTION – Change in paradigm brought about by inconsistencies within the old scheme or by technologic developments that permit scientist to ask new questions & gain new data. www.indiandentalacademy.com 4
  5. 5. www.indiandentalacademy.com 5
  6. 6. Changing paradigms INTRINSIC GENETIC FACTORS FUNCTIONAL FACTORS EPIGENETIC FACTORS www.indiandentalacademy.com 6
  7. 7. 1920-1940  Study of craniofacial skeleton with no consideration to function – - Anthropologic craniometry -Racial analysis for socioeconomic structure of western Europe  Krogman- ‘static approach’  Moss(1982)1. Pre-radiologic phase - craniometry 2. Radiologic phase – no conceptual change www.indiandentalacademy.com 7
  8. 8.  Studies based on – Comparative anatomy, Craniometrics, Radiographic cephalometrics  Anatomic intuition & extrapolation from other parts of body- growth immutable & genetically pre-determined.  Moss- “Classic Triad” 1. Sutures are primary growth sites 2. Growth of the cranial vault occurs only by periosteal deposition and endosteal resorption. 3. All cephalic cartilages are primary growth centers under direct genetic control www.indiandentalacademy.com 8
  9. 9. Genomic paradigm  Genetically determined – so growth pattern invariant.  “norms” or “standards”  Treatment of bones of face ignored – heredity & unmodifiable  Focus on the more plastic dentoalveolar area.  If not alter facial growth – acceptable dental alignment. www.indiandentalacademy.com 9
  10. 10. 1940-1960  Increase in experimental animal research.  Methodologic change- Technological developments:1. Use of Radioopaque Implants. 2. Vital Dyes. 3. Autoradiography. 4. In-vivo and In-vitro transplantations.  Conceptual change- too many variations in growth to be genetically determined; affected by modifying influences  Mid to late 1950s- PRE-REVOLUTIONARY www.indiandentalacademy.com 10
  11. 11. www.indiandentalacademy.com 11
  12. 12.  The end of 1950’s – 2 approaches within genomic paradigm (Krogman – 1974) – 1. COMPREHENSIVE APPROACH 2. STRUCTUROFUNTIONAL APPROACH Comprehensive approach:  descriptive  continued craniometrics with more sophisticated hardware -radiographs, cephalostats and software (statistical models). www.indiandentalacademy.com 12
  13. 13. Structurofunctional Approach:  Experimental & analytic  Concentrated more on “cause and effect relationships”  Effect of altered or abnormal function on form www.indiandentalacademy.com 13
  14. 14.  The end of 1950’s -genomic paradigm put into question  Periosteal and sutural bone growth - removed from genomic paradigm - given the status of secondary, compensatory or adaptive phenomena  Lack of evidence- genomic paradigm remained dominant  Alternative view-“Function” plays a major role continued to gather momentum. www.indiandentalacademy.com 14
  15. 15. 1960-1980  Early 1960s- ‘period of Revolution’.  Development of alternative paradigm mostly associated with – Melvin Moss  ‘Functional Matrix Hypothesis’- some consider it to be an alternative paradigm itself.  David Carlson- major component of ‘FUNCTIONAL PARADIGM’  Daniels & Kremanak – “has probably both stimulated & inhibited thinking & experimentation. It may be harmful in thinking.” www.indiandentalacademy.com 15
  16. 16. www.indiandentalacademy.com 16
  17. 17.  “Functional Matrix Hypothesis”- a topic of theoretical debate involving people likeMoorrees(1972) Koski(1972) Wayne Watson(1982) Johnston(1976)  Alexander Petrovic and associates(1975)- proposed the ‘Cybernetic theory’. www.indiandentalacademy.com 17
  18. 18. www.indiandentalacademy.com 18
  19. 19.  2 Paradigms : 1. Genomic--Exists primarily on the strength of the belief that facial growth and form should be encoded genetically. 2. Functional--Includes the Functional Matrix Hypothesis and its extension-The epigenetic hypothesis  At present - a confluence of these two paradigms is seen until a new one is proposed. www.indiandentalacademy.com 19
  20. 20. Theories of growth  Different theories differ in the location at which genetic control is established.  3 major theories explaining primary determinant of craniofacial growth – 1. Bone 2. Cartilage 3. Soft-tissue matrix www.indiandentalacademy.com 20
  21. 21. Growth site versus growth centre Cranial growth centers: Facts or fallacies? – Koski AJO-DO 1968 Aug (566-583) BAUME: Growth Centre- site of endochondral ossification with tissue-separating force, contributing to the increase of skeletal mass. i.e. location at which independent (genetically controlled) growth occurs. www.indiandentalacademy.com 21
  22. 22. Growth site: regions of periosteal or sutural bone formation and modeling resorption adaptive to environmental influences. i.e. merely location at which growth occurs. www.indiandentalacademy.com 22
  23. 23. Sutural dominance theory  SICHER – studies using vital dyes – sutures caused much of growth  “….the primary event in sutural growth is the proliferation of the connective tissue between the two bones. If the sutural connective tissue proliferates it creates the space for oppositional growth at the borders of the two bones.”  Connective tissue in sutures of nasomaxillary complex & vault – separated bones like synchondrosis & epiphyseal plate www.indiandentalacademy.com 23
  24. 24.  Sicher ascribes equal value – osteogenic tissues, cartilage, sutures & periosteum. www.indiandentalacademy.com 24
  25. 25. www.indiandentalacademy.com 25
  26. 26.  2 differing views concerning the structure of the sutures – 1. Three-layer structure: - Connective tissue between the two bones - same as cartilage at the base of the skull, epiphyses, and articular surfaces of long bones - "spreading" of the suture, initiated by the proliferation of the middle layer cells of the sutural tissue. -"tissue-separating force" in the sutural tissue. www.indiandentalacademy.com 26
  27. 27. 2. Five-layer structure : -Each bone at the suture has its own two-layer periosteum covering + opposing surfaces of the bones -fifth layer between these periosteal layers - allows for slight adjustments between the bones during growth active proliferating role - layers of the periosteums of each bone.  Histologic specimens of sutures examined same – interpretation different. www.indiandentalacademy.com 27
  28. 28. Evidence against sutural theory 1. Subcutaneous autotransplants of the zygomaticomaxillary suture area in the guinea pig have not been found to grow – lack of innate growth potential. 2. Growth of sutures – respond to external stimuli. 3. Extirpation of facial sutures - no appreciable effect on growth of the skeleton. 4. Shape of sutures - depends on functional stimuli 5. Closure of sutures -extrinsically determined. 6. Sites of sutures -www.indiandentalacademy.com . not predetermined 28
  29. 29. CONCLUSION:  Sutures are growth sites not centres.  Adaptive, compensatory or secondary growth. www.indiandentalacademy.com 29
  30. 30. Cartilaginous theory SCOTT’S HYPOTHESIS:  Intrinsic growth-controlling factors in cartilage & periosteum.  Sutures are secondary & dependent on extrasutural influences.  Cartilaginous part of skull must be recognised as primary centres of growth, with nasal septum being a major contributor in maxillary growth, per se.  Sutural growth – responsive to synchondrosis proliferation & www.indiandentalacademy.com factors. local environmental 30
  31. 31. www.indiandentalacademy.com 31
  32. 32. Cranial base synchondroses  Removal of spheno-occipital synchondrosis - results in an arrest of growth in length of the cranial base .  Pressure & tension – little effect on cartilage.  Intramembranous bone- immediate response. www.indiandentalacademy.com 32
  33. 33. Endochondral cranial base – lesser response to brain growth than intramembranous cranial vault. Primary centres of growth – Sarnat, Burdi, Baume, Petrovic & others. www.indiandentalacademy.com 33
  34. 34.  Endochondral ossification at the synchondrosesonly a response to external stimuli?  Cartilage- lacks same amount of independent growth potential as transplants of epiphyseal cartilage under similar experimental conditions.  Spheno-occipital synchondrosis appears to close much earlier than is usually stated in the textbooks 11 to 16 years of age www.indiandentalacademy.com 34
  35. 35. Nasal septal cartilage  Scott- primary cartilage in nasal septum – primary mechanism for growth of nasomaxillary complex.  Latham- ligament extending from nasal septal cartilage to to anterior premaxillary region – SEPTOPREMAXILLARY LIGAMENT.  This is an important relation between midfacial & nasal septal growth – especially before birth. www.indiandentalacademy.com 35
  36. 36.  Histologic examination - endochondral ossification at the septoethmoidal junction and area of proliferation at the vomeral edge of the cartilage  In the palatal area - resorption on the nasal side and apposition on the oral side of the bony palate. www.indiandentalacademy.com 36
  37. 37.  Experimental excision of the nasal septum affects the growth of the upper face considerably - due to trauma.  Nasal septum - central support for the upper facial area, and its loss results in a predictable collapse in the area. www.indiandentalacademy.com 37
  38. 38.  Arrhinencephalic 9-month-old child (with the septum missing) - resorption and apposition processes in the bony palate normal.  Height of the upper face not greatly affected, although the sagittal development of the middle third of the face was retarded  In recent experiments – growth as well in culture as epiphyseal plate cartilage. www.indiandentalacademy.com 38
  39. 39. Condylar cartilage  Growth of the condylar cartilage is responsible for the anteroposterior growth of the mandible- primary growth centre. www.indiandentalacademy.com 39
  40. 40.  Scott- growth of the condylar cartilage enables the condyle "to grow upwards and backwards so as to maintain the contact at the temporomandibular joint as the mandible is carried downwards and forwards by the growth of the upper facial skeleton."  If the condylar cartilage is transplanted to a relatively nonfunctional site, such as the subcutaneous or brain tissue, it does not maintain its structure and does not behave like the condylar cartilage in situ.  Bilateral condylectomy, congenital absence of the rami- no appreciable effect on the growth of the rest of the mandible in humans. www.indiandentalacademy.com 40
  41. 41. www.indiandentalacademy.com 41
  42. 42.  Studies involving the use of metallic implants - actual growth of the condyle is sometimes upward and backward and sometimes upward and forward. www.indiandentalacademy.com 42
  43. 43. www.indiandentalacademy.com 43
  44. 44. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com 44

×