Growth pattern of mandible /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
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The dynamics of the growth of bones is a complex process.
The growth pattern of the mandible has been assessed by
the application of various methods described for the study
of the growth of bones.
The use of any one of these methods will reveal certain
information.
With the use of two or more of them - accurate information
can be obtained.
John Hunter's classical descriptions was more than 200 years
ago, today refinement of older methods and the
development of newer ones have come up.



To date, serial cephalometric roentgenography in concert with
radiopaque implants, which serve as fixed reliable markers, is the
most accurate method to determine the growth pattern of the
mandible.



To this armamentarium, digital subtraction radiography,
computerized tomography, and magnetic resonance imaging may
be methods that will offer more detailed and accurate
information.




Any study of growth of bones concerns itself with :
What is the pattern of growth? What are the sites? What are
the amounts? What are the rates? Do they vary? When? What are
the directions? What are the changes in proportion? What factors
are influential?

One approach might yield information about the sites of growth,
another about the rate, and still another about direction.
A combination of methods, however, potentially will yield more
information, and in certain instances more accurately, than one
alone
Two types of bone growth occur in the following principal regions.
One is continuous appositional/resorptive with differential bone
remodeling at various periosteal and endosteal surfacess.
In the ramus the posterior border is a particularly active site of bone
apposition, whereas the anterior border is a particularly active site
of bone resorption.


The second type of mandibular bone growth is at the condyle, where
cartilage is replaced by bone.
Growth of the condyle and ramus, prolific sites, is generally in a
superior and posterior direction. Because the condyle articulates
with the mandibular fossa of the temporal bone, the final effect of
growth there is a downward and forward displacement of the
mandible.


Two random age levels the mandibular outlines were
superposed so that the surface fields of resorption and
deposition are expressed. The mandible enlarges predominantly
posteriorly and superiorly.

METHODS OF ASSESSING
GROWTH OF BONES
Direct measurements
Anthropometry : can be performed on either the living or
dried subject specimen.
In spite of the accuracy of the anthropometric apparatus, exact
measurements of growth are extremely difficult to obtain.
When performed on the living, the measuring instruments must
be placed on the soft tissues overlying the bony landmarks,
thereby precluding minute www.indiandentalacademy.com
accuracy of measurements.

Hunter was one of the first to apply anthropometry using the
mandible In his study of four human mandibles, ranging from 5
years of age (with the complete primary dentition) to adulthood
(with the complete secondary dentition), were aligned along the
symphyseal and lower borders of the mandible.( No reason was
noted for this choice of reference planes).
Hunter described that
(1) resorption was as characteristic of bone growth as deposition,
(2) the body of the mandible gained in height principally by
growth of alveolar bone,
(3) the shedding of teeth was always accompanied by resorption
of alveolar bone, whereas eruption of teeth was always
accompanied by growth of alveolar bone, and
(4) the deciduous second molar and permanent first, second, and
third molars erupted in the same relation to the mandibular ramus.

Vital staining
Madder feeding : Madder is a plant that possesses a deeply red
colored root.
Belchier in 1736 was one of the first to give an accurate account of
the staining of bone of animals fed madder
Duhamel (1742) demonstrated that only newly formed bone was
stained by madder and from his studies described the manner of
growth of bones.
Hunter reported on the growth of the mandible in the pig. He also
demonstrated the wide alternate red and white layers
(corresponding to the prolonged periods when madder was fed
and withheld) in longitudinal and transverse sections of long
bones.

ALIZARIN RED INJECTIONS. Alizarin is one of the principal
tinctorial agents found in madder and is available in synthetic
form.
sharp vital staining of calcifying substances may be obtained by a
single intraperitoneal or intravenous injection of a 2% solution
of alizarin red S
Ground sections (25 to 50 µm thick) under higher magnification
and strong transmitted illumination, the red lines (5 to 20 µm in
width) are readily counted and the distance between them can
be accurately measured with a micrometer eyepiece.
They also have been used in studies of calcification in other
conditions such as healing of fractures, kidney casts, calcified
placques of an atheromatous aorta, and calcified scars. The egg
shell, the shell of the turtle, and the dentin of teeth are also
stained by alizarin red S.



Although growth of bones is greatest in the young, nevertheless
bone tissue is in a state of continuous change throughout life as
a result of an interplay of formation and destruction.



In areas where bone is being apposed, osteoblasts are found
arranged in a continuous single layer like cuboidal epithelium
on the surface of the bone. Osteoclasts are found in areas where
bone is being destroyed or resorbed.



The osteoclasts are multinucleated giant cells of varying size
and shape and are found in shallow hollows (Howship's
lacunae) on the surface of the bone trabeculae.

Enlow, on the basis of extensive histologic studies, has
reconstructed gross patterns of bone formation and destruction
In response to the question of what reference points were used to
superpose the two mandibular outlines, Enlow stated, "No
actual points were utilized. Rather, registration was based on
the 'typical' distribution of surface resorptive and depository
fields, thus showing the endosteal and periosteal directions of
cortical remodeling.
Histochemical studies are also of value in obtaining further
information about the nature of bone formation. By this
method, for instance, the importance and the localization of
various enzymes, particularly alkaline acid phosphatase and
other substances such as glycogen and glycoproteins, have
been determined.

Implants. Implants as reference markers have been used in the
study of growth of bones as early as 1742 by Duhame

Hunter inserted two pellets along the length of the shaft of the
tarsus of a young pig and measured the distance between the
pellets. When the tarsus was fully grown, he found that the
distance between the pellets had remained exactly the same and
that the bone had increased in length at the ends.
This experiment proved that there was no interstitial growth of
bone

Implantation of gold, silver, dental silver amalgam, stainless steel,
vitallium, and tantalum in the form of screws, pegs, pins, clips,
or wires within a single bone can be used for the study of total
amount of bone growth by measuring the increase in distance
between the implants and the outer borders of the bone.
Humphry, by placing wire loops around the ramus of the pig
mandible, demonstrated that there was resorption on the anterior
border and deposition of bone on the posterior border of the
ramus.


Impressions and casts. Duplication of various parts of the
body (skull, face, orbit, maxillary sinus, teeth and dental arches,
extremities) is possible by taking impressions with plaster of
paris, hydrocolloid, Thiokol rubber, low fusing metal, stone, or
other material.
Individual or sectional impressions may be necessary, depending
on the size, shape, and contour of the particular part that is to be
duplicated.
The impression serves as the negative and by filling it with a
material such as plaster of paris, an accurate positive or
duplication of the part can be obtained.

Photographs. The effects of disease on the face, jaws, teeth, and
the human constitution have been shown by means of
photographs.


Photographs taken under controlled conditions with the subjects
placed against a graduated grid have permitted a morphologic
classification.



Sheldon, Stevens, and Tucker used such grids for establishing
somatotypes.
Although this method does not lend itself to accurate
measurements of growth of individual bones, it does permit the
study of growth of selected regions or the entire subject.

Radioautographs. A radioautograph is obtained by placing the
tissues of an animal injected with a radioactive substance in close
contact with a photographic emulsion for a suitable exposure
period.
Alpha or beta rays from the radioactive material affect the silver
bromide crystals or a photographic emulsion in a manner similar
to that of light.
After development and fixation of the-film, darkened areas will be
found that correspond to the distribution of the radioactive
material.

Radioisotopes have already yielded considerable fundamental
information previously unobtainable on the growth and
development of animals.
A radioactive isotope of an element will behave in exactly the same
manner biologically and chemically as the stable isotopes of the
same element as long as the radiations from the radioactive
isotope are not sufficiently intense to produce pathologic changes.
Radioactive phosphorus deposited in bone will behave like ordinary
phosphorus
Some other radioisotopes used are sodium, calcium, strontium,
fluorine, chlorine, iodine, carbon, plutonium, uranium, americium,
and gallium.

Roentgenographs. Roentgenography is a reliable indirect method
of studying growth of bones.
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In 1912, Tandler suggestd the use of x-ray films in
anthropometry of the skull.

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In 1931, Broadbent and Hofrath simultaneously but
independently described a technique of cephalometric
roentgenography.



In 1937, Broadbent reported his findings gained from studies of
growing children.

A refinement in the cross-sectional method was made by the use of
roentgenography and the superpositioning of roentgenographic
tracings over various supposedly stable bony landmarks to obtain
the pattern of growth.

Symons, in studying the angular relationship of the occlusal plane
of the lower teeth with the body proper of the human mandible,
superposed tracings of roentgenographs of adult human
mandibles on a line joining the center of the head of the
condyle to the inferior dental foramen.
Scott by this same method correlated tooth eruption with
mandibular growth in superposed roentgenographs of pig
mandibles of different ages.
He observed little resorption at the anterior border of the ramus.
The disadvantages of this method were
1.
the same living animal was not studied,
2.
the base line or points for superpositioning the
roentgenographic tracings varied with different animals, and
3.
the base changed with www.indiandentalacademy.com
growth.

Brodie in 1941, was the first to apply Broadbent's method to a
longitudinal growth study of human males from the third
month to the eighth year of life.
The accuracy of this method depends on standardization of
technique. Selection of a stable anatomic base, however, for
superposing the roentgenographic tracings is the key to
reliable findings because any shift of the area used as a
baseline distorts the true direction of growth.
It permits a dynamic study of the growing child— that is, the
increase in size and the change in proportion of the same
growing bone (as the mandible) or group of bones forming a
bone complex (as in the middle third of the face).
It reveals the rate, the amount, and relative direction of bone
growth. It does not, however, reveal either the sites or the
mode of growth of bones.

Method of superposing in examining growth stages of the
mandible.

In serial studies on the growth of the human mandible, Brodie,
superposed tangents to the lower border of the mandible as a
baseline for the serial roentgenographic tracings
The angle formed by this line with a tangent to the posterior border
was bisected to locate gonion, the point of superposition.
However, this method was predicated on the fact that there was
minimal growth or no growth at the lower border.
Moyers and Bookstein, however, have reported that conventional
cephalometrics fails to capture the curving of form and its
changes and thus misrepresent growth.


Serial cephalometric roentgenography and implantation.
Use of a combination of serial roentgenography and radiopaque
implants is a more accurate and reliable approach for a dynamic
longitudinal study of the growth of bone
a stable base for superpositioning the serial roentgenographic
tracings is obtained by inserting two or more radiopaque
implants into the mandible.
Thus, the ensuing growth can be accurately determined and
measured by superpositioning roentgenographic tracings over
the images of the metallic implants.
Measurements between implants and the outer borders of an
individual bone are valid only after verification that with growth
of the bone the implants remained within bone tissue and were
not extruded into the surrounding soft tissues. To avoid
foreshortening, implants must lie in a plane parallel to the x-ray
film.

Another advantage of combined method is
The ability to measure the amount of new bone formation and
resorption that occurred from one period to another without
killing or reoperation of the animal.
There is also no interference with the normal diet such as occurs
in madder-fed animals.
A disadvantage is that the roentgenograph demonstrates the sum
total of apposition and resorption at that particular time without
the detailed intervening changes as shown with vital markers
and histologic sections

In 1963, Björk reported on the growth pattern of the human
mandible. This was a longitudinal roentgenographic study with
tantalum implants initiated in 1951 on more than 100 children.
He pointed out that the lower border of the mandible was
unsuitable for a reference plane.
In the analysis of lateral mandibular growth, the two profile
roentgenographs to be compared were oriented so that the
implants in the mandible were superposed.
Examples were given of the individual differences in the
development of the mandible


For the most part, the anterior aspect of the chin underwent no
visible remodeling. Beneath the chin there was some periosteal
growth in many cases, accentuated during adolescence.
The most pronounced remodeling occurred beneath the angulus
region. Here resorption was usual, but periosteal apposition was
also seen.
The direction of growth at the condyles in the sagittal plane varied
widely with an average direction slightly forward in relation to
the posterior tangent to the ramus.

digital subtraction radiography, computerized tomography, and
magnetic resonance imaging may be methods that will offer
more detailed and accurate information.

SUMMARY
The growth pattern of the mandible has been studied and described
in this report in the pig, monkey, and human by use of
anthropometry, vital stains, histology, serial roentgenography,
and serial roentgenography combined with radiopaque
implants. The last method gives the most accurate information
about the gross growth pattern of the mandible.

Growth pattern of mandible /certified fixed orthodontic courses by Indian dental academy

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