CRANIAL GROWTH CENTRES FACT OR FALLACY
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The term growth centre has been widely used with skeletal growth phenomina to the extent that it has been used to cover up many growth sites. ď Ž Baume- proposed that the term skeletal growth centre can be used to describe places of endochondral ossification with tissue seperating force. ď Ž
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Time factor is also brought into conideration wherein growth centre should mean a place where the growth of a skeleton takes place for a sufficient length of time to make a real contribution to the increase in skeletal mass. KOSKI has tried to examine some of these alleged growth centres using the definition given by BAUME as the criterion. BAUME also defined growth sites as regions of periosteal or sutural bone formation and modelling resorption adaptive to environmental influences. www.indiandentalacademy.com
SUTURES There are two schools of thought regarding the growth at sutures 1. Sutures are 3 layered structures having two layers of connective tissue seperated by a single layer of connective tissue. The connective tissue layer acts as the proliferatng zone. Implies tissue seperating forces in the sutural tissue.
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2.Sutures are 5 layered with the 2 bones on either side havin 2 layers of periostium with a 5th intevening connective tissue layer. www.indiandentalacademy.com
ď Ž
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Question is whether the growth is primary or secondary in nature. Evidence in favour of dependant role appears to be accumulating1. Trabecular pattern -changes with age 2. Removal of sutures-appears to have no effect on growth of the skeleton. 3. Shape of sutures-determined by functional stimulus.
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4.Closure of sutures-appears to be determined extrinsically. 5.External force application-by using clips can actually halt the growth at the sutures. 6.Parrallelism of sutures-only superficial -zygomatico-maxillary sutures grow laterally -direction of growth varies
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ď Ž
Conclusion -unlikely that there are tissue seperating forces -they are unlikely to be growth centres.
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Cranial base ď Ž
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Cranial base synchondrosis especially the spheno-occipetal synchondrosis has been considered to be a growth centre. Evidence in favour1.structural similarity to the epiphyseal plates. 2.reaction to biochemical stimuli similar to epiphyseal growth plates.
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ď Ž Evidence against
1.no tissue seperating forces. 2.transplants
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Conclusion ď Ž
There seems to be no direct evidence to support the claim that they are growth centres.
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NASAL SEPTAL CARTILAGE The general concensus – nasal septal
cartilage provides thrusting force to carry maxilla forward and downward during growth.
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ď Ž
Evidence in favour 1. endochondral ossification -is seen histologically. 2. vomeral-edge -is an area of proliferation 3. on palatal -surfacesresoption on nasal and deposition on oral side. 4.excision-affects growth. 5.arrhincephalic patient-normal vertical -retarded saggital mid face www.indiandentalacademy.com
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Evidence against 1.excision-retards growth(may be due to trauma,early excision does not affect)
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Conclusion May be a growth centre in post natal life.
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CONDYLAR CARTILAGE ď Ž
There is a general belief that growth at the condyles moves the mandibular body forward and downward and this opens the space below the cranial base into which the mandibular and maxillary processes grow and teeth errupt.
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ď Ž
Evidence against 1.Structural - Is a secondary cartilage.Latecomer, not even from the same precursor as the as epiphyseal cartilage. -Does not grow interstitially like epiphyseal cartilage but appositionally from deepest layersof connective tissue covering the condyle. -The cells that divide are the intermediate layer cells and not cartilage cells, these are like undifferentiated mesenchymal cells -Structural organization is lacking www.indiandentalacademy.com
-non hypertrophic cartilage cells-the layer is very narow and change into hypertrophic layer very soon. -the whole hypertrophic area seems to be in a state of mineralization whereas in the epiphyseal plates only the degenerative zone is mineralizing. -spongiosa always seen in long bones is lacking
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2.Functional Resposive to mechanical stimulus respond differentially from epiphyseal cartilages to various hormonal and chemical agents. 3.Transplants only when transplanted with adjacent bone does it grow,but even then the structure is not maintained as beautifully. www.indiandentalacademy.com
4. Tissue culture studies demonstrates lack of cartilage growth 5.Surgical bilateral condylectomy showm to have no appreciable effect on the growth. 6.Implant direction of growth seems to vary considerably.sometimes upwards and backwards and sometimes upwards and forwards. www.indiandentalacademy.com
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FINAL CONCLUSION The existance of growth centres have not been demonstrated beyond doubt. We should keep an open mind and look for explainations and theories that agree with all well known facts.
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