Controlling factors in craniofacial growth new/ dental implant courses by Indian dental academy

CONTROLLING FACTORS IN CRANIOFACIAL GROWTH

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com www.indiandenatalacadem y.com

INTRODUCTI ON

It is commonly said that growth is strongly influenced by genetic factors. also by

 Environment  Nutritional status  Degree of physical activity  Health or illness www.indiandenatalacadem y.com

Since need for orthodontic treatment is created by disproportionate growth of the jaws, in order to understand the the etiological processes of malocclusion,it is necessary to learn how facial growth is influenced and controlled www.indiandenatalacadem y.com

Lot of effort has been put in recent years in understanding growth control.

Exactly what determines the growth of the jaws,however remains unclear and continues to be the subject of intensive research www.indiandenatalacadem y.com

genetic factors The basic control of growth both in magnitude & timing, is located in genes.

Studies of twins have shown that

body size body shape deposition of fat patterns of growth are all more under genetic control www.indiandenatalacadem y.com

Samir bishara

Genetic factors most likely play a leading role in male- female growth differences

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Neural control It is thought that a growth center exists in the region of the hypothalamus, which keeps children on their genetically determined growth curves.

There is also evidence that the peripheral nervous system plays a part in growth control. www.indiandenatalacadem y.com

Samir bishara

Hormonal control Probably all of the endocrine glands influence growth.

Growth hormone maintains the growth from the birth onwards.

Excess of growth hormone – pituitary giant.

Pituitary deficiency – dwarf.

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moyers

Nutrition Sufficient in take of nutritious food is essential for normal growth.

Malnutrition involves deficiency in calories and required food elements.

Under nutrition tends to accentuate the normal differential growth of the body tissues. www.indiandenatalacadem y.com

Secular Trend There is considerable evidence that Children today have growing faster than they grew in the past.

Although Children are growing at a faster rate, they are stopping growth sooner.

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moyers

Season and circadian Rhythm Growth in height is faster in the spring than in the autumn.

There is evidence that growth in height and eruption of teeth is greater at night than in the day time.

The reason for this differences is probably related to fluctuations in the hormone release. www.indiandenatalacadem y.com

Samir bishara

Disease The effects of disease are similar to those of malnutrition.

After an illness, a catch up growth period usually brings the child back to the predetermined growth curve.

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Cultural factors Males of Japanese born near the middle of the century in the united States grew taller on average than groups born in Japan because of different cultural influences. www.indiandenatalacadem y.com

Samir bishara

According to moyers

Controlling factors www.indiandenatalacadem y.com

Controlling factors NATURAL  Genetics  function  general body growth  neurotrophis m

DISRUPTIVE FACTORS

• orthodontic forces • surgery • malnutrition • malfunctions

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NATURAL FACTORS

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Genetic factors

One can often say that all resemblances in families are genetic & structural.

Facial expression,mode of laughter,way of speaking may be learned as a result of living together.

The old argument about heredity versus environment has changed from the question of which is more important,how,when,and in what way does the environment alter the original form laid down by heredity www.indiandenatalacadem y.com

Intrinsic genetic factors

primary

secondary www.indiandenatalacadem y.com

There are primary controls for initiation & formation of facial structures.

Primary genetic control determines certain initial features: Tooth buds calcify in the jaws,& mandible forms in face,not legs www.indiandenatalacadem y.com

Secondarily,there are inductive local feedback & inner communication mechanisms between cells & tissues www.indiandenatalacadem y.com

Although it is argued whether or not there is simple genetic control,the end result appears to be multifactorial or poly genic. www.indiandenatalacadem y.com

function Normal function plays a role in skeletal growth.

Altered function hampers growth like  TMJ Ankylosis  Aglossia  Neuromuscular disorder www.indiandenatalacadem y.com

general body Biological maturitygrowth plays a general role in all aspects of maturation of individual.

All maturational events are influenced in individuals by a combination of factors  Genetic  Climatic  Racial  Nutritional  socioeconomic

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neurotrophism

It is known that neural activity controls muscle activity & growth.

Nervous control of skeletal growth, assumedly by transmission of a substance through the axons of the nerves has been hypothesized for years and is called neurotrophism. www.indiandenatalacadem y.com

DISRUPTIVE FACTORS

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Disruptive factors in facial growth are those which do not routinely contribute to normal variation but when they appear in the individual may be important.

They may be elective,environmental, or congenital in origin. www.indiandenatalacadem y.com

a) Orthodontic forces

Orthodontic forces are utilized to affect growth & alter tooth positions. www.indiandenatalacadem y.com

b) surgery Orthognathic surgeries are undertaken for, To correct a craniofacial anomaly To improve aesthetics in nonanomalous www.indiandenatalacadem y.com

Modern surgical techniques have improved surgeons ability • Relapse of the surgical result ,even in non growing • Effects of surgery on subsequent growth www.indiandenatalacadem y.com

C) malnutrition

Gross malnutrition affects craniofacial growth

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D) malfunctions The altered malfunction can play a role in craniofacial morphology & well documented.

(Harvold,Petrovic,Mcnamara and Carlson) www.indiandenatalacadem y.com

Controlling factors

According to Ranly

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Intrinsic genetic factors

Local epigenetic factors General epigenetic factors

Local environmental factors General environmental factors www.indiandenatalacadem y.com

Intrinsic genetic factors

Genetic factors inherent to the osseous tissues www.indiandenatalacadem y.com

bone

nucleus

Form of osseous tissue

Genetic material www.indiandenatalacadem y.com

Local epigenetic factors

Genetically determined influence originating from adjacent structures and spaces Brain eyes etc

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eyeball

orbit www.indiandenatalacadem y.com

General epigenetic factors

Genetically determined influences originating from distant structures Sex hormones

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Local environmental factors Local non-genetic influences originating from the external environment (local external pressure muscle forces etc) www.indiandenatalacadem y.com

Morphology of bone gets altered according to the functional demands placed on it www.indiandenatalacadem y.com

General environmental factors

General nongenetic influences originating from the external Food & oxygen supply etc environment www.indiandenatalacadem y.com

Determinants of facial growth www.indiandenatalacadem y.com

Three major theories in recent years have attempted to explain the determinants of craniofacial growth www.indiandenatalacadem y.com

1 Bone like other tissues is the primary determinant of its own growth.

That is genetic control is expressed at the level of the bone,& therefore its locus should be the periosteum.

Dominant view until the 1960’s has largely been discarded. www.indiandenatalacadem y.com

2

Cartilage is the primary determinant of skeletal growth,while bone responds secondarily and passively.

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3

The soft tissue matrix in which the skeletal elements are embedded is the primary determinant of growth,& both bone and cartilage are secondary followers. www.indiandenatalacadem y.com

Site versus center A site of growth is merely a location at which growth occurs.

Center is a location at which independent (genetically controlled) growth occurs.

All centers of growth also are sites,but the reverse is not true. www.indiandenatalacadem y.com

Bone ,suture, & periosteum were considered as growth centers.

It is clear now that sutures & the periosteal tissues, are not primary determinants of craniofacial growth.

Evidence which lead to this conclusion (1) When an area of the suture ,between two facial bones is transplanted to another location,the tissues does not continue to grow. www.indiandenatalacadem y.com

Lack of innate growth potential

(2) It can be seen that growth at the sutures will respond to outside influences under a number of circumstances.

If facial bones are mechanically pulled apart at the sutures,new bone will fill in.

distraction osteogenesis If a suture is compressed, growth at that site will be impeded use of head gear www.indiandenatalacadem y.com

THUS SUTURES MUST BE CONSIDERED AREAS THAT REACT-NOT PRIMARY DETERMINANTS

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Cartilage as a determinant of craniofacial growth www.indiandenatalacadem y.com

For many bones, cartilage does the growing while bone merely replaces it making this theory attractive for jaw bones.

If cartilaginous growth were the primary influence,the condylar cartilage could be considered pacemaker for growth of that bone.

Remodeling of ramus & other surface change-----secondary to primary cartilaginous growth. www.indiandenatalacadem y.com

visualize the mandible like diphysis of long bone bent into horse shoe shape with epiphyses removed. cartilage at the end should behave like a growth center.

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Long bone bent as horse shoe-shape

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Growth of the maxilla  More difficult but not impossible to explain on a cartilage theory basis.  There is no cartilage in the maxilla itself,but there is a cartilage in the nasal septum.  Proponents of cartilaginous theory hypothesize that the cartilaginous nasal septum serves as a pacemaker. www.indiandenatalacadem y.com

The cartilage is so located that the its growth could easily lead to a downward and www.indiandenatalacadem forward translation of the maxilla. y.com

two kinds of experiments have been carried out to test the idea that the cartilage serves as a true growth center. ďƒ˜ transplanting the cartilage ďƒ˜ removing the cartilage at an early age www.indiandenatalacadem y.com

Transplantation experiments demonstrate that not all skeletal cartilage acts the same when transplanted.

If a piece of the epiphyseal plate of long bone is transplanted,it will continue to grow in a new location or in culture,indicating that these cartilages do have innate growth potential. www.indiandenatalacadem y.com

ďƒ˜ Cartilage from spheno-occipital synchondrosis of the cranial base also grows when transplanted,but not as well ďƒ˜ It is difficult to obtain cartilage from the cranial base,particularly at an early age when the cartilage is actively growing www.indiandenatalacadem y.com

ďƒ˜In experiments,transplanting cartilage from the nasal septum ,sometimes it grew ,sometimes it did not ďƒ˜ In precise recent experiments ,nasal septal cartilage was found to grow nearly as well www.indiandenatalacadem y.com

Little or no growth was observed when the mandibular condyle was transplanted.

From these experiments,the other cartilages appear capable of acting as growth centers ,but the mandibular condyle does not

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Experiments to test to the effect of removing cartilage.

The impact on a growing rabbit of having a segment of cartilaginous nasal septum removed.

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ď ś In summary, it appears that epiphyseal cartilages and the cranial base synchondroses can & do act as growing centers, as can the nasal septum. ď ś Neither transplantation experiments nor experiments in which the condyle is removed lend any support to the idea that the cartilage of the mandibular condyle is an important center. ď ś Growth at the mandibular condyle is more like growth at the sutures of the www.indiandenatalacadem maxilla y.com

Functional matrix theory growth

ď ‹ If neither bone nor cartilage were the determinant for growth of the craniofacial skeleton, it would appear that the control would have to lie in the adjacent soft tissue. ď ‹ This was put forward by moss in 1960

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ď ‹ He theorizes that growth of the face occurs as a response to functional needs & neurotrophic influences, & is mediated by the soft tissue in which the jaws are embedded. ď ‹ The soft-tissue grow & both bone & cartilage react.

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example

The growth of the cranial vault is a direct response to the growth of the brain.

Microcephaly: when the brain is very small,the cranium is also very small Hydrocephaly: reabsorption of CSF is impeded ,intracranial pressure builds up which impedes development of the brain.

Another excellent example is size of the eye & size of the orbit www.indiandenatalacadem y.com

normal

Anencephaly

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conclusion Growth is a interplay between heredity and environment.In coming years we are going to witness intense research in this field ,which may lead us to control growth at will ? www.indiandenatalacadem y.com

www.indiandentalacademy.com Leader in continuing dental education

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