The Angle Orthodontist
`
`VoL.l
`
`No. 2
`
`APRIL, 1931
`A magazm.e established by the co-workers o j
`Edward H. Angle, in his memory.
`
`A NEW X-RAY TECHNIQUE
`and
`ITS APPLICATION TO ORT,HODONTIA
`BY B. HOLLY BROADBENT D.D.S., Director of the Bolton Study, Anatomical
`Lahoratory_, Western R eserve University, Cleveland, Ohio.
`R ead before the Orthodontia Sectio11 of the Mid-Winter .Meetitig of the Chicago Dental
`Society, Febrnary 4, 1931.
`DURING the last few years numerous scientific papers have been presented
`before orthodontic societies by men in the field of physical anthropology.
`These men have made us realize the value of their precise methods of meas(cid:173)
`uring biological problems_ and made us hope that we might learn to apply
`anthropometric technique to our orthodontic practices. Most orthodontists
`still measure dental and facial deformities very
`largely by
`the
`inter(cid:173)
`relations of the teeth and jaws both before and after treatment.
`Recently we have made a decided advance, by the application of
`cephalometric methods to record and measure the changes in the jaw in
`relation to the rest of the head. Careful and detailed analytic studies on
`this problem bear the names 01 Todd, Keith, Hellman, Krogman, Lewis,
`Simon, Dewey, Stanton-and others whose names merit but space does not
`It is in the light of contributions made by these workers
`permit mention.
`to the accumulated common understanding that the method about to be
`described has been developed. Previous methods use landmarks in the
`skull of the living child which unfortunately have to be approached through
`the skin and soft tissues. The uncertainty of such technique led the author
`to search for a means of recording craniometric (hard tissue) landmarks on
`the living child as accurately as it is done with a craniostat in measuring the
`dead skull.
`
`THE ANGLE ORTHODONTIST
`
`45
`
`001
`
`Align EX1014
`Align v. 3Shape
`IPR2022-00145
`
`
`
`VoL.l
`
`No. 2
`
`APRIL, 1931
`A magazm.e established by the co-workers o j
`Edward H. Angle, in his memory.
`
`A NEW X-RAY TECHNIQUE
`and
`ITS APPLICATION TO ORT,HODONTIA
`BY B. HOLLY BROADBENT D.D.S., Director of the Bolton Study, Anatomical
`Lahoratory_, Western R eserve University, Cleveland, Ohio.
`R ead before the Orthodontia Sectio11 of the Mid-Winter .Meetitig of the Chicago Dental
`Society, Febrnary 4, 1931.
`DURING the last few years numerous scientific papers have been presented
`before orthodontic societies by men in the field of physical anthropology.
`These men have made us realize the value of their precise methods of meas(cid:173)
`uring biological problems_ and made us hope that we might learn to apply
`anthropometric technique to our orthodontic practices. Most orthodontists
`still measure dental and facial deformities very
`largely by
`the
`inter(cid:173)
`relations of the teeth and jaws both before and after treatment.
`Recently we have made a decided advance, by the application of
`cephalometric methods to record and measure the changes in the jaw in
`relation to the rest of the head. Careful and detailed analytic studies on
`this problem bear the names 01 Todd, Keith, Hellman, Krogman, Lewis,
`Simon, Dewey, Stanton-and others whose names merit but space does not
`It is in the light of contributions made by these workers
`permit mention.
`to the accumulated common understanding that the method about to be
`described has been developed. Previous methods use landmarks in the
`skull of the living child which unfortunately have to be approached through
`the skin and soft tissues. The uncertainty of such technique led the author
`to search for a means of recording craniometric (hard tissue) landmarks on
`the living child as accurately as it is done with a craniostat in measuring the
`dead skull.
`
`THE ANGLE ORTHODONTIST
`
`45
`
`001
`
`Align EX1014
`Align v. 3Shape
`IPR2022-00145
`
`
`
`The problem then was first, to design and build a headholder along the
`lines of the skull holders, and second, to find a means of recording precisely
`the craniometric as well as the cephalometric landmarks of the face and
`cranial base of the living head.
`
`Fig. 1 Special Reserve Craniostat built for roentgenographic studies of skulls.
`
`With the Reserve craniostat as a basis, and with the help of our machin(cid:173)
`ist, the first part of our problem was promptly accomplished. Then the
`greater problem of registering the internal landmarks of the face and cranial
`base was solved through the perfection of a roentgenographic technique that
`records these points accurately on the photographic film. The films, like
`orthodiagraphic tracings, permit accurate measurement with drafting in(cid:173)
`struments. Many experiments were made over a period of several years to
`test its accuracy and to bring this technique to its present state of usefulness.
`These experiments were first made with skulls on the specially constructed
`craniostat illustrated by Figure 1.
`The skulls were prepared by drilling a minute hole at many of the in(cid:173)
`ternal and external cranial landmarks and inserting very small pieces of lead
`that would register their exact position on the photographic film. Similar
`bits -of lead were placed on dental and facial points. The skulls were then
`clamped in the instrument with the under surface of the upper side of the
`
`46
`
`THE ANGLE ORTHODONTIST
`
`002
`
`
`
`ear holes (external auditory meatus) resting on the supports R and L,
`Figure 1, and the skull fixed in the Frankfort relation with its left orbital
`point at E in the horizontal plane when Eis level with Rand L. The pointer
`E can be moved vertically, laterally, and antero-posteriorly. The vertical
`scale V ( Figure 2) gives us the distances above and below the Frankfort hor(cid:173)
`izontal in a sagittal plane. The horizontal scale (AH) records the antero(cid:173)
`posterior distances in the ~agittal plane while the lateral distances in the
`
`Fig. 2 Skull in the craniostat in the Frankfort Plane. Note rnme of the sites
`of the lead pieces have been accentuated and enclosed in small circles
`for illustration.
`
`frontal planes are registered on the lateral scale (LH) on the upper surface of
`the pointer carriage. Points in the interior of the skull can be reached with
`curved pointers ( Figure S) when the calvarium is removed. These readings
`were then plotted on millimeter cross section paper in frontal _and sagittal
`planes.
`After the sites of the lead pieces were plotted in graphic projection in
`the sagittal plane and their relationships defined by measurement, the skulls
`were x-rayed for the lateral picture. Each skull was then rotated ninety
`
`THE ANGLE ORTHODONTIST
`
`47
`
`003
`
`
`
`degrees and measured in the frontal plane, the graph made, and the frontal
`x-ray picture taken. Superimposing these roentgenograms upon their re(cid:173)
`spective graphs gave us a measure of technical precision and clearly in(cid:173)
`dicated that a reliable method of recording internal as well as external
`craniometric points had been successfully accomplished.
`
`Fig. 3 Skull in the craniostat. Note that the pointer has been moved to Nasion.
`
`The sagittal planes are at right angles to the Frankfort plane and to the
`Frontal planes, while the Frontal planes are at right angles to Frankfort
`and parallel to a line joining the tops of the ear posts R and L ( Figure 1) ,
`i.e. a line passing through the right and left Porion points.
`Figure 4 shows the cassette ( film holder) in place for the lateral picture.
`The film is supported in a sagittal plane at right angles in all directions to a
`line through the top of the right and left ear supports. The distance of
`the film from the median sagittal plane of the instrument is determined on
`the lateral scale, and recorded along with the distance of the x-ray source
`from this plane.
`Two relations are necessary to produce two or more identical x-ray
`
`48
`
`THE ANGLE ORTHODONTIST
`
`004
`
`
`
`Fig. 4 Skull in the craniostat with the cassette in place for the lateral
`roentgenogram.
`
`Fig. SA Diagram of the relation of the Anode Target to the craniostat secured
`with the aid of a projection lens.
`Fig. SB Diagram of the relation of the Anode Target to the craniostat illustrat(cid:173)
`ing the pat!\ of the rays and relation of the size of the picture to the skull.
`
`THE ANGLE ORTHODONTIST
`
`.49
`
`005
`
`
`
`pictures of a skull ; first, that of the skull to the instrument; and second,
`the relation of the source of the x-rays to the instrument. The mechanical
`adjustments of the instrument makes the placing of the skulls in the Frank(cid:173)
`fort horizontal very simple and certain.
`In order to relate the source of the x-rays at the anode target of the
`tube to the instrument, advantage was taken of the fact that light generated
`
`Fig. 6 Craniostat with cassette in contact with left post. Note the white opaque
`letters R and L mounted on the right and left ear posts and their
`shadows R and L on the cassette.
`
`by the cathode filament is reflected from the anode target along the path of
`the central ray when the x-rays are generated. This permitted us to mount
`temporarily a projection lens ( Figure SA) in front of the x-ray tube with
`the anode target in the optical axis of the lens. After the craniostat is leveled
`with a spirit level, the path of the central ray is brought to the level of the
`Frankfort plane as indicated by the light projected through the lens. Ex(cid:173)
`periments convince us that the most useful pictures were those made when the
`path of the central ray coincided with the line joining the tops of the
`two ear supports, and
`the
`tube placed S feet or more
`from
`the
`middle of the craniostat. This was easily done by measuring the distance
`
`so
`
`THE AN GLE ORTHODONTIST
`
`006
`
`
`
`from a point midway between the ear posts of the craniostat and directing
`the path of the central ray, as indicated by the projected light, towa'rd this
`point and at the same horizontal level.
`The cathode filament is heated in incandescence with a low tension current
`of about 6 volts from a toy transformer.
`'With a cassette in place in · the
`craniostat ( Figure 6) the shadows of the right and left ear supports can be
`
`Fig. 7 Craniostat as shown in Figure 6 after being rotated in a horizontal plane
`until the shadows of R and L and their respective posts coincide. This
`indicates the desired relation of the craniostat to the path of the ray.
`
`seen on its surface. For illustration small white opaque letters R and L
`were mounted in identical relation to their respective posts. These throw
`their dark shadows on the cassette. The instrument is rotated in the hor(cid:173)
`izontal plane until these shadows register one on th·e other as may be seen in
`It will be seen th_at the shadows of the tops of the ear posts
`Figure 7.
`coincide and this places them in the desired relation to the path of the
`central ray and consequently in the proper relationship to the path of the
`x-rays.
`We have demonstrated to our satisfaction that, after dismantling the
`
`THE ANGLE 0RTH0!JONTIST.
`
`51
`
`007
`
`
`
`apparatus, the skull can be set up anew and pictures taken identical with
`those previously made in dimensions and in inter-relationship of predeter(cid:173)
`mined points.
`The relationships of the sites defined by the shadows of the lead markers,
`as well as the relationships of the other predetermined points to the projected
`shadows of the ear posts are dependent upon two factors. These are, first,
`the target distance at which the pictures are taken and secondly, the dis-
`
`PROFILE XRAYS
`
`SKULL 404
`AG[ II Yl'.S ,
`W.JI .U,
`
`79 M .M.
`
`_.Lo:_ .. _ -
`,. ..
`
`-
`
`-
`
`1,• VPIA.'f
`
`v;::.,
`
`Fig. 8 Tracings of these different roentgenograms of skull 404 WRU superposed in
`Frankfort horizontal with. Porion points in register. Note the increase
`in size of the pictures as the distance decreases although
`the
`pQSition of the film
`remains fixed.
`
`lance of the film from the median sagittal plane of the craniostat or head
`holder. Since, the x-rays are not parallel as they approach the skull or head
`but diverge from a common point in the form of a cone, the size of the
`image on the film is slightly larger than the object projected. When the
`target distance is lessened and the film remains at a fixed distance from the
`object the size of the image increases. Figure SB is a diagram of these
`relationships, and this eff~ct is clearly shown in Figure 8 by superimposing
`tracings of three successive roentgenograms of a skull, the Frankfort plane,
`with Porion, being registered in each tracing. When the target distance
`remains fixed and the distance of the film from the median sagittal plane
`increased, a similar change in the size of the image is produced. Since our
`technique predetermines the target distance, five feet, and the film distance
`is measured when the picture is taken we can easily compute the actual
`
`52
`
`THE AN.CLE ORTHODONTIST
`
`008
`
`
`
`dimensions of the face and head with these figures along with those recorded
`in the finished picture.
`If, for example, we want to know the distance MD, ( Figure SB) we
`measure its shadow BC on the film , and add the scale reading for EF noted
`at the time the picture was made, to the known target distance AE. With
`the two altitudes AE and AF and the base BC known, we can figure the other
`In our studies of the
`unknown base MD of the triangles ABC and AMO.
`
`Fig. 9 Frontal and lateral roentgenograms in µlace for measurement on a trans-
`illuminated drafting table fitted with the Universal drafting machine.
`development of the face of the growing child it has not been necessary to
`compute mathematically these many relationships. The variable factors
`are the same for the same child and subsequent pictures superimposed on
`the first picture clearly reveal t4e changes in growth and development and
`likewise show results of orthodontic treatment.
`The roentgenograms are measured with the aid of a Universal Drafting
`machine fitted with millimeter scales. The lateral view is mounted on the
`transit:uminated drafting table as shown in Figure 9 with the line passing
`through Porion and left Orbital points parallel to the horizontal scale. The
`frontal view is then mounted beside its lateral view with a line passing
`through the right and left Porion points coinciding with the horizontal line
`projected from the lateral view. The lateral picture is then in Frankfort
`relation and points may be projected from this view to the frontal view and
`their positions measured in three planes of space.
`
`THE ANGLE ORTHODONTIST
`
`53
`
`009
`
`
`
`The head holder ( Figure 10) was designed on the working principles of
`the craniostat and built for use in conjunction with the standard junior
`dental chairs. Through the generosity of Mrs. Chester C. Bolton and her
`son Mr. Charles B. Bolton the head holder and x-ray equipment shown in
`Figure 11 was built and installed in the Anatomical Laboratory of Western
`Reserve Medical School, for a study of the developing face of the growing
`child.
`
`Fig. 10 The Broadbent Head Holder for roentgenographic studies of the living
`bead. Built in the Anatomical Laboratory Western Reserve University for
`the Bolton Study of the development of the face of the growing child.
`
`The Bolton study has been under way _about eighteen months. During
`this time we have had 1700 children between the ages of nine months and
`twenty years. Many of these have been x-rayed at six month intervals and
`will be followed through a five year period. Most of the younger ones are
`x-rayed every three months during periods of rapid change in dentition.
`The head holder is supported on its fixed base A (Figur.e 11) above a
`child's size dental chair that has had the usual head rest removed. The
`chair does not come in contact with the head holder but may be raised
`or lowered to permit comfortable adjustment of the child's head to the in(cid:173)
`strument. Like the relation of the skull to the craniostat, the head rests
`on the uppermost side of. the rods that are inserted into the ear holes
`
`54
`
`THE ANGLE ORTHODONTIST
`
`010
`
`
`
`the Anatomical Laboratory of
`in
`Fig. 11 The Bolton Room
`School at Western Reserve University, Cleveland.
`
`the Medical
`
`THE ANGLE ORTHODONTIST
`
`55
`
`011
`
`
`
`(Figures 10, 12, 13). These rods are calibrated and allow the head to be
`centered between the ear supports. The left ear support is constructed
`so that the cassette may be inserted and held dose to the left side of the head
`as in Figure 12 and 13. The distance of the film from the middle of the
`instrument is read on a millimeter scale at the back of the cassette support.
`
`Fig. 12 The Head Holder with cassette in its place for lateral roentgenogram.
`
`After the head has been centered, the chair is lowered or the child
`instructed to settle down so that the under surfaces of the superior border
`of the ear holes are resting on the upper sides of the ear rods. Then the
`head is rotated on this Porion axis by lifting or lowering the face until the
`lowest point on the inferior bony border of the left orbit is at the level of
`the top of the ear supports as indicated by the Orbital marker at E (Figure
`14) . The front attachment F (Figure 10) which supports the frontal
`cassette and impression tray, also carries a rest for the root of the nose at
`N (Figure 10). This rest is in the midline of the head bolder and may be
`raised or lowered in a frontal plane and moved toward the ear posts in a
`horizontal plane by moving the entire front attachment. Placing this rest
`against the root of the nose clamps the head firmly in the instrument (Figures
`13 and 16).
`Imbedded in the side of the support (N) toward the face, is a
`small piece of lead, just large enough to register clearly on the films. The
`exact relation of this lead point to the ear posts is recorded from the miili(cid:173)
`meter scale on the instrument at the time the first pictures are taken. These
`readings help in adjusting the head to the instrument when subsequent pic(cid:173)
`tures and models are made. The lead J?Oint is used too, when models of
`
`56
`
`THE ANGLE ORTHODONTIST
`
`012
`
`
`
`the mouth are made in a known relation to the roentgenograms. The im-..
`pression and model technique is not a part of this presentation and is described
`in detail separately. The technique of making the roentgenograms of the
`living head in the head holder is identical in principle to that just described
`for the skuJls and craniostat.
`With the head clamped firmly in the head holder as described above,
`
`Fig. 13 The child's head adjusted to the head holder. Note the cassette in
`place for the lateral roentgenogram.
`
`the cassette for the lateral roentgenogram is placed in its support beside the
`head ( Figures 12 and 13) and exposed. This cassette is then remDved and
`another cassette placed in the groove on the front attachment F (Figure 15)
`and this film exposed for the frontal roentgenogram. After removing the
`frontal cassette a tray of impression plaster may be placed in the mouth and
`aliowed to set. The universal joint support at U (Figures· 10 and 16) is
`then locked on the handle of the tray T to secure the relationship of the tray
`to the right and left ear posts and the lead· point in N, and consequent-ly
`to the craniometric points found in the roentgenograms.
`The head cannot be rotated on a vertical axis through 90 degrees and
`therefore we use two x-ray tubes, one for the lateral picture and another for
`the frontal picture. The illustration (-Figure l l) of the Bolton Room shows
`
`THE ANGLE ORTHODONTIST
`
`013
`
`
`
`these two tubes at B and C mounted on special tube stands, each placed 5
`feet from the center of the head holder A at the level of the ear supports.
`They are controlled by the single control stand E through the ceiling switch
`S. This switch permits the operator to direct the current from the high
`tension transformer T to either tube at will. Above the door at L is housed
`the toy transformer that delivers about 6 volts to each tube, for use in orient(cid:173)
`ing the tubes to the head holder as previously described, for the lateral pie-
`
`Fig. 14 The child's head centered in the Head Holder on the ear rods. Note
`the lowest point on the inferior border of the left bony orbit is leveled with
`t.l\e top of the ear rods after wh ich tho front support for the
`head is attached.
`ture with the craniostat. The back tube B is oriented to the head holder
`. with the path of its central ray in the mid-line of the head holder and its
`anode target S feet from the earpost axis. The central rays of the two tubes
`~re in the same horizontal (.Frankfort) plane and at right angles to each
`other. The resulting pictures register precisely the . desired craniometric
`landmarks of the cranial base and face in three planes of space.
`The pictures contain much of the soft tissue detail, especially the facial
`profile, which has eliminated in our studies the need of photographing the side
`view of the face. With sufficient illumination it can be seen in the lateral
`ro~ntgen.ogram and studied and measured in life size along with the teeth and
`
`~8
`
`THE ANGLE ORTHODONTIST
`
`014
`
`
`
`Fig. 15 The Head Holder with cassette in its place on the front attachment F.
`
`Fig. 16 The Head Holder with impression tray and clamp U in place on the
`front attachment for securing a model of the mouth oriented to the
`roentgenograms.
`
`THE ANGLE ORTHODONTIST
`
`S9
`
`015
`
`
`
`tracings of
`the frontal
`lo
`Fig. 17 Diagram of the relations of the lateral
`rotinlgenograms made in the Bolton Study for measuring facial
`development and growth .
`
`Fig. 18 Lateral and Frontal Roentgenograms of a child with a developing Class
`III mal-occlusion. Note that this craniornetric technique applied to
`the living eliminates the uncertainty oi measuring through soft
`tissue as it is done in cephalometric methods.
`
`60
`
`THE ANGLE ORTHODONTIST
`
`016
`
`
`
`bones that support it. The wide range of half tones in the Diaphax films that
`represent the hard and soft tissues are easily seen with varying intensities of
`transillumination, but difficult to show in a single half tone illustration.
`Tracings are made of these films by three workers and these checked by a
`fourth person before the figures are accepted for stalistical purposes .
`
`}
`
`' \
`I
`' ' I
`' •
`
`A
`
`../
`' '
`
`I / 10,
`'~ --
`
`F
`
`Fig. 19 Tracings from roentgcnograms of the same child shown in Figure 18
`taken two years apart. Note thQ relations of the teeth and jaws to the
`anterior-posterior base planes, PF, PN, SN, and to the vertical
`planes
`through P and 0.
`
`Figures 17 and 18 show the Frankfort horizontal, the median sagittal
`plane and the vertical Porion plane as well as some of the other planes which
`we have found useful in our studies of facial and cranial relationships.
`By the end of the first year of our study the subsequent pictures of the
`same children taken at three and six mon.th intervals, clearly pointed out
`many significant observations, no traces of which are to be found in the
`data collected from dead skulls. One very significant fact had an immediate
`application to the interpretation of the developmental growth of the face of
`those youngsters whose dentition presented an orthodontic problem. Sub(cid:173)
`sequent pictures at certain ages have revealed areas of non-growth in
`the cranial base. These areas in which there had been no change per(cid:173)
`mitted us to precisely relate the pictures and measure the changes in the
`
`THE ANGLE ORTHODONTIST'
`
`61
`
`017
`
`
`
`IOI
`
`Fig. 20 Tracings A and B shown in Figure 19 superposed in Frankfort relation
`with Porion (P) registered. Note the amount and direction of change
`indicated by this common method of superimposing.
`
`F
`
`IOI
`
`Fig. 21 Tracings A and B of Figure 19 superposed on the Porion-Nasion Plane
`(PN) with their distances registered at their mid-point. Compare
`with Figures 20, 22, 23 and 24.
`·
`
`62
`
`THE ANGLE ORTHODONTIST
`
`018
`
`
`
`other parts. The next series of illustrations are tracings of two pictures of
`the same child about two years apart. The tracing A ( Figure 19) is from
`the first picture taken at the age of 6 years and 2 months while the tracing
`In B will be seen the
`B in solid lines is at the age of 8 years and S months.
`
`F
`
`,o,
`
`Fig. 22 Tra1.:ing A am.I B of Figure 19 superposed with Porion (P) registe red
`and with Nasion (N) of tracing B falling on a line projected from
`Nasion (N) of tracing A parallel to the Frankfort plane
`(F) of tracing A. This is Krogman's method of
`superimposing tracings. Compare with
`Figures 20, 21, 23 and 24.
`
`upper and lower incisors and first permanent molars and upper cuspid.
`These teeth are shown in A along with the second deciduous molars and
`deciduous central incisors. The deciduous incisors had been shed before
`the second picture B was taken.
`In Figure 20 the tracings of this developing
`Class 111 malocclusion are placed in Frankfort relation with Porion register(cid:173)
`ed. This method of relating tracings is the one most frequently illustrated
`in our literature. Although these tracings are of tJ1e same head and not of
`skulls of different individuals is it safe to assume that Porion is relatively
`the most fixed point and that the rest of the face and cranial base are under(cid:173)
`going the changes indicated? Shifting the tracings so that they are super(cid:173)
`posed along lhe Nasion-Porion plane (NP Figure 2 I) with the mid-point
`of each plane registered, one will secure a somewhat different interpretation
`
`THE ANGLE ORTHODONTIST
`
`63
`
`019
`
`
`
`of the changes in which we are interested. The next Figure 22 shows another
`method of relating these two tracings with Porion registered and Nasion of
`tracing B falling on a line projected from Nasion in tracing A parallel to
`the Frankfort plane. Compare this with Figure 20. Reverse this relation(cid:173)
`ship and superimpose Nasion (Figure 23) allowing Porion of tracing B to
`fall along the Frankfort Plane of tracing A and then observe the effect on the
`other parts.
`
`p
`
`IOI
`
`Fig. 23 Tracings A and B of Figure 19 superposed according to Todd with
`Nasion (N) registered and Porion P of tracing B allowed to fall on the
`Frankfort plane of tracing A. This method of superimposing
`is opp_osite to that of Krogman shown in Figure 22 .
`Compare with Figures 20, 21, 22 and 24.
`
`As valuable as these several methods of superposing orthodiagraphic
`tracings for measuring facial growth may be, it would seem to the author
`that the areas in the cranial base that have not changed, offer a more
`precise basis for relating tracings and consequently a more accurate method
`of measuring growth and development in the living head. Therefore when
`we have an unchanged base. common to two or more subsequent pictures of
`the same child, like the area including Sella Turcica and Nasion of this series,
`In the last Figure 24, the trac(cid:173)
`we superimpose them on these landmarks.
`'ing A and B have been superimposed with their planes SN coinciding. The
`
`64
`
`THE ANGLE ORTHODONTIST
`
`020
`
`
`
`relation of N to S has not changed between the time these two pictures were
`taken and the Figure 24 shQws the greatest increase in growth between S
`and P and along the lower border of the mandible and the posterior border of
`the ascending ramus.
`
`F
`
`101
`
`Fig. 24 Tracing A and B of Figure 19 superposed by the authors method of
`using unchanged areas for superimposing. Note that in both A and B
`the relation of the Sella Turdca Nasion area has not changed and is
`therefore common to both drawings. This figure shows these
`two tracings superposed with Sella Turcica (S) and Nasion
`registered. Compare
`this with Figures 20, 21,
`(N)
`22, and 23.
`
`This roentgenographic method has the added advantage of disclosing
`changes, not only of the teeth that have erupted, but it clearly shows the
`rate and amount of growth and path of eruption of the unerupted teeth.
`With the opportunity to record the structural changes along with means of
`measuring increase in size, we have a morphological as well as a quantitive
`study. This technique has a direct and immediate application to Ortho(cid:173)
`dontia as a means of measuring tooth and facial changes, while the results of
`the Bolton Study are adding to our understanding of the principles of de(cid:173)
`velopmental growth of the living face which forms the foundation of our
`specialty.
`
`THE ANGLE ORTHODONTIST
`
`65
`
`021
`
`
`
`As a summary of these observations I would emphasize the following:
`( 1) That the application of precise methods of measurement used by
`Physical Anthropologists to Orthodontic practice is a decided advance toward
`a more scientific solution of our orthodontic problems.
`( 2) By means of a head holder and a standardized roentgenographic tech(cid:173)
`nique it is possible to make accurate determinations of changes in the living
`head that may be due to developmental growth or orthodontic treatment.
`( 3) Such a technique permits changes in the same individual to be measured
`and studied. This eliminates the uncertainty of measuring such changes
`by a comparison of dimensions of different individuals of successive ages.
`( 4) This roentgenographic technique registers the craniometric landmarks of
`the face and cranial base of the living head which heretofore have only been
`measured on dead skulls with a craniostat.
`( 5) Our present standards compiled from measurements of skulls of children
`are largely a measure of defective material. A dead child is usually a
`defective one.
`( 6) Cephalometric methods of measuring facial changes while a decided
`advance, do not permit us to record the landmarks beyond the face in the
`cranial base.
`( 7) This Craniometric technique has the decided advantage of not having
`to determine the site of the hard tissue landmarks of the face through the
`covering of soft tissue of uncertain thickness.
`(8) Subsequent roentgenograms have revealed areas in the cranial base that
`show no change between certain ages. These areas offer a more stable
`base for relating our tracings and afford a very accurate method of measuring
`changes in the teeth, jaws and face.
`
`66
`
`THE ANGLE ORTHODONTIST
`
`022
`
`
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