Method and apparatus for making X-ray photographs of jaw structure

A method of apparatus for making X-ray photographs of a jaw structure which makes it possible to obtain clear and distinct images of the dental arch without superimposition of neighboring teeth and further to equalize the enlargement ratio of images to be made on the film no matter which spots of the teeth may be taken at the time of X-ray photographing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is related to a method and an apparatus for making X-ray 
photographs of a whole jaw structure for dental use. 
2. Prior Art 
As generally known, X-ray photographic units of this type are developed by 
using the tomographic technology to adapt curved planes so that the whole 
jaw structure can be closely examined. Those photographs for dental use 
have, of course, to be very clear to the teeth. 
However, the conventional units are not free from some mechanical defects. 
For example, in the case of a three-circle-composite elliptic arc, an 
X-ray photograph is taken by succeedingly shifting the camera along its 
locus from the first locus to the second and further to the third locus. 
This process requires the camera to move about three different centers of 
gyration, which makes the driving mechanism very complex and the pictures 
unclear particularly around those spots where the camera is moved into a 
different locus. The Applicant has invented a radiographic apparatus as 
described in the Japanese Application No. 53,165/72 which overcomes the 
defect mentioned above. The principal structure of this apparatus is such 
that the crossing paths intersecting at right angle to each other are 
provided on a fixed base with sliders which are movable in their own path, 
while an arm spanned between the sliders gets to swing to create an 
elliptical locus. 
Thus, the X-ray film holder disposed on one end of the arm is induced to 
shift continuously and smoothly analogous to the dental arch of the 
subject. This apparatus can produce clear and distinct pictures because 
there is no necessity for changing the center of gyration as explained 
above. However, this apparatus is not free from some problems such as 
occurrence of the superimposition of images of neighboring teeth due to 
the fact that the X-ray beam is projected in a little oblique direction to 
an individual tooth, especially in its adjacent region; and also there 
remained unsolved another question as to the difference in the enlargement 
ratio between images made on the film of each one of the teeth or even 
between both ends of one single tooth. In consideration of the above, a 
new radiography apparatus as in the Japanese Patent Application No. 
97,303/74 (Laid Open Patent No. 24,889/76) was developed. In this 
apparatus, a circular arc path and a straight-line path passing through 
the center thereof were formed on the base, and sliders shifting in these 
two paths, respectively, were provided in place of such sliders shifting 
in the directions intersecting each other at right angles alike in the 
above apparatus, thereby the X-ray film holder on the arm end being 
allowed to move continuously and smoothly analogous to the dental arch of 
the subject. In this apparatus, the X-ray beam is projected in the 
direction substantially intersecting at right angles to an individual 
tooth of the dental arch, especially to the adjacent region of them, so 
that it became possible to eliminate at least the defect of the 
superimposition of teeth neighboring each other. Nevertheless, remained 
unsolved the problem of the difference in the enlargement ratio between 
images made on the film of an individual tooth or even between both ends 
of one single tooth. 
SUMMARY OF THE INVENTION 
This invention has as its object to provide a new X-ray photographing 
method to solve the defects involved in the existing prior art method and 
also to provide a novel apparatus for producing dental X-ray photographs 
of the whole jaw structure to be used in such method. 
Description will be now directed to the X-ray photographing method 
according to the invention with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
The method used in the present invention is a method of making X-ray 
photographs of the whole jaw structure for dental use. The general concept 
of this invention is as shown in FIG. 1, in which an X-ray generator 
(hereinafter referred to as X-ray source) x and an X-ray film holder h are 
mounted on opposite sides of an arm a in such a manner as to face each 
other with reference to the axis a.sub.o of the arm a while keeping the 
relative position to each other invariable. The film holder h here is made 
to shift along a chain line S analogous to a dental arch d of a subject p, 
while maintaining the predetermined correlation between itself and the 
X-ray source x, at the same time when the focusing X-ray beam b from the 
X-ray source x is urged to be radiated continuously upon the face of the 
film f contained in the X-ray film holder h. Thus, it becomes possible to 
make tomographs of curved planes in the dental arch d. Such is the 
photographing method which adapts the principles illustrated in FIGS. 2 
and 3 or 6. 
The method based on the principles in FIGS. 2 and 3 is a method of making 
X-ray photographs of the whole jaw structure for dental use, which is 
characterized in such a construction as follows: 
Collaterally to the arm a between the film holder h and the X-ray source x, 
not less than two driving points for swinging 1 and 2 are provided 
separately in the positions which lie apart from the axis a.sub.o of the 
arm a and keep the immovable relation to the arm a. Then, to these driving 
points, swinging 1 and 2, are imparted curvilinear motions 10 and 20 
independent of each other. Through the cooperative regulation of these two 
curvilinear motions 10 and 20, the arm a is made to swing within the area 
of a plane containing the axis a.sub.o of the arm a whereby the X-ray beam 
b comes to be projected in the direction substantially intersecting at 
right angles, as a minimum, to any given neighboring point t.sub.o of each 
individual tooth t in the dental arch d, and whereby the film f to be 
exposed to the X-ray beam b is able to shift analogous to the dental arch 
d in the substantially equidistant relation to any tooth t in the dental 
arch d. (In this connection, another photographing method which adapts the 
principle illustrated in FIG. 6 will be described hereinafter.) 
As an example of the apparatus used in the above-mentioned method can be 
taken the one illustrated in FIGS. 4 and 5. In summary, the dental 
apparatus of making X-ray photographs of the whole jaw structure 
illustrated here comprises an X-ray source x and an X-ray film holder h 
both being mounted on opposite sides of an arm a in such a manner as to 
face each other relatively to the axis a.sub.o of said arm while keeping 
the relative position to each other invariable; swing sliders 11 and 21 
being provided in the immovable relation to the arm a at least each on 
either side across the axis a.sub.o of the arm a midway between the X-ray 
source x and the X-ray film holder h; curvilinear guide paths 12 and 22 
being provided on a base 3 independently of each other in order to guide 
the respective sliders 11 and 21; and a driving power source 6 being 
provided on the arm a; wherein the arm a is brought about to swing through 
the cooperative regulation of the sliders 11 and 21 which are guided in 
the curvilinear guide paths 12 and 22, in company with which the film 
holder h is made to shift analogous to the dental arch d of the subject p 
and on the other hand, the focusing beam b from the X-ray source x comes 
to incide in the direction substantially intersecting at right angles to 
any given neighboring point t.sub.o of an individual tooth t in the dental 
arch d, while the face of the films f in the holder h to be exposed to the 
X-ray beam b is induced to move in the substantially equidistant relation 
to any tooth in the dental arch d. 
The apparatus in this illustration is the one that adapts the principle and 
method illustrated in FIG. 2, as mentioned above. The swing sliders 11 and 
21 (shown in FIG. 4) of this apparatus are provided correspondingly to the 
respective vertexes B and C of the triangle ABC in FIG. 2. The reason for 
this is that it is necessary for this photographing method to have at 
least two driving points 1 and 2 for swinging in positions which are apart 
from the arm a and keep the fixed relation to the arm a. These driving 
points 1 and 2 for swinging are determined as follows: At the middle 
(median) point A' between the first two incisors is one vertex A of an 
arbitrary triangle ABC, the other vertexes B and C are set up in any 
position on either side across the axis a.sub.o and these two vertexes B 
and C are each driving points 1 and 2 for swinging. A line is drawn from 
the vertex A to the point D at which the line B-C intersects the axis 
a.sub.o of the arm a, that is, the line A-D is congruent with the axis 
therewith a.sub.o of the arm a, and further, this axis a.sub.o is also 
congruent with the X-ray beam b; therefore, the line A-D is congruent with 
the X-ray beam b. Now when the point A on the line A-C shifts along the 
standard dental line d.sub.1 of the dental arch d, the triangle ABC is 
forced to shift in such a way that the line A-D shall always be 
substantially normal to the standard dental line d.sub.1 at any given 
neighboring point t.sub.o of an individual tooth t and as shown in FIG. 2, 
the points B and C each shift successively tracing one after another the 
points B.sub.1, B.sub.2, B.sub.3 . . . or C.sub.1, C.sub.2, C.sub.3 . . . 
with the shifting movement of the point A. If these shifting points 
B.sub.1, B.sub.2 . . . or C.sub.1, C.sub.2 . . . are connected in 
succession, curved lines as indicated by the reference numerals 10 and 20 
are generated. These curved lines are equivalent to the moving locus of 
the above-mentioned curvilinear motions 10 and 20 independent of each 
other, respectively. It is apparent from the above that the curvilinear 
guide paths 12 and 22 in the above illustrated apparatus are motion guides 
for putting the above curvilinear motions 10 and 20 into operation. In 
this example, the X-ray film holder h and the X-ray source x of the 
apparatus are provided on the extension line of the line A-D of the 
triangle ABC, wherein the enlargement ratio of images depends on the 
length l from the vertex A of the triangle ABC to the face of the film f 
in the film holder h. As for the swing sliders 11 and 21 (shown in FIG. 4) 
of the apparatus in this example, they are provided each on either side 
across the axis a.sub.o of the arm a. However, the number of sliders 11 
and 21 (shown in FIG. 4) is not necessarily limited to only two pieces as 
in this case. It is permissible of course to place a plurality of sliders 
at any appropriate position together with an equal number guide paths 
associated with the respective sliders. For the same reason, the 
curvilinear guide paths 12 and 22 are also restricted in number only to 
two such as illustrated in the example and also the form of the 
curvilinear guide paths 12 and 22 (shown in FIG. 4) can vary endlessly 
depending on the arbitrary setting of the vertexes B and C of the triangle 
ABC. For example, the points B and C in FIG. 2 which forms a foundation 
also for the apparatus of FIGS. 4 and 5, are positioned asymetrically each 
on either side across the axis a.sub.o of the arm a and lie along the axis 
a.sub.o of the arm a in sliding relation to each other; therefore, their 
motion loci take a form of the reference numerals 10 and 20 in FIG. 2. In 
another modification illustrated in FIG. 3, however, curvilinear motions 
10 and 20 of the same form intersect each other, unlike the curvilinear 
motions 10 and 20 in FIG. 2, when the points B and C are located in a 
symmetrical relation each on either side across the axis a.sub.o of the 
arm a. That is, since the curvilinear guide paths are formed in accordance 
with curvilinear motions 10 and 20 of the points B and C, it is natural 
that the form of the guide paths 12 and 22 varies depending on the 
respective curvilinear motions 10 and 20 of the points B and C. It may be 
said in this connection that if the points B and C are placed too close to 
the axis a.sub.o, the smoothness of the swinging movement of the arm a 
will be expected. For this reason, it is desirable to set up the relation 
of the points B and C to the axis a.sub.o of the arm a neither too close 
nor too far away within the scope of preventing the apparatus from growing 
too large. Incidentally, though the swing sliders 11 and 21 are positioned 
within the area of the same plane with each other in the illustration, 
they can be also placed on different planes separately above and below and 
the curvilinear guide paths 8 and 9 each may be provided within their own 
planes. 
Description will be now directed to the gist of the operation and effects 
of the hitherto-mentioned apparatus with reference to FIGS. 4 and 5. By 
way of example, when the roller 6 rotates in the direction of the arrow Z 
over the sliding platform k, the arm a swings in the direction of the 
arrow a' while the swing sliders 11 and 21 fixed on the arm a on either 
side across the axis a.sub.o of the arm a shift while being regulated by 
the respective curvilinear guide paths 12 and 22. At this time, the 
curvilinear guide paths 12 and 22 is nothing less than the forms of the 
shifting loci of the points B and C of the triangle ABC, the line A-C of 
which is made to shift so as to become substantially the normal line to 
the standard dental line d.sub.1 at all times, as mentioned above. This 
means that the line A-C conforms with the direction of the X-ray beam b. 
Therefore, the X-ray beam b always incides intersecting substantially at 
right angles to the standard dental line d.sub.1, to be more precise, to 
any given neighboring point of individual teeth t, in consequence of which 
the superimposition of neighboring teeth can be avoided as far as 
possible. As for the enlargement ratio (value) of images, it depends on 
the length l from the vertex A of the triangle ABC up to the face of the 
film f in the film holder h, as described before. But the length l has 
been specified to be always constant from the beginning, so that the face 
of the film f comes to keep a certain distance from individual teeth t 
while shifting continuously analogous to the dental arch d. As a result, 
the stable enlargement ratio of images recorded on the film can be 
obtained maintaining a substantially equal value for any tooth t. And what 
is better, it is possible with this apparatus to acquire clear and 
distinct images without any distortion, on account of the fact that the 
swing sliders 11 and 21 which are provided apart from the arm a and 
maintain the immovable relation thereto, are placed in a position to shift 
continuously and smoothly in the curvilinear guide paths 12 and 22. 
The different point of the principle and method adapted in FIG. 6 from 
those in the hitherto described embodiment lies in that out of two driving 
arms a, while the other two are positioned apart from the axis a.sub.o of 
the arm a, but in the immovable relation to the arm a. In other words, 
contrary to the previous embodiment in which both of driving points 1 and 
2 are provided each apart from the axis a.sub.o of the arm a and in the 
immovable relation thereto, the difference of the principle and method in 
FIG. 6 from it resides in the provision of one out of two driving points 
on the very axis a.sub.o of the arm a. This photographing method is such a 
one of X-ray photographing the whole jaw structure for dental use wherein 
the arm a is caused to swing within the area of the plane containing the 
axis a.sub.o of the arm a itself by the cooperative regulation of the two 
curvilinear motions 10 and 20 independent of each other and different in 
form from each other which are imparted separately to the driving point 1 
for swinging positioned on the axis a.sub.o of the arm a and to the 
driving point 2 for swinging provided apart from the axis a.sub.o of the 
arm a and in the immovable relation to the arm a, thereby the X-ray beam b 
coming to be projected substantially intersecting at right angles at least 
to any given neighboring point t.sub.o of individual teeth t, and further 
thereby the face of the film f exposed to the X-ray beam b being able to 
shift in the substantially equidistant relation to any tooth t. 
The apparatus used in this method is such a type as shown in FIGS. 7, 8 and 
9, namely, a dental apparatus of making X-ray source x and an X-ray film 
holder h being mounted on opposite sides of an arm a in such a manner as 
to face each other with reference to the axis a.sub.o of the arm a while 
keeping the relative position to each other invariable; a shaft bearing 
a.sub.1 being attached to the arm a; not less than a branch arm a.sub.2 
being provided projecting in the different direction from the axis a.sub.o 
of the arm a and in the immovable relation to the arm a; a swing slider 21 
being provided on the branch arm a.sub.2 ; a base 3 being fixed above the 
arm a to suspend the arm a and having a borehole 31 in the middle part; a 
rotating plate 4 being provided on the base 3 to swing freely with a point 
of it 3 as a rotor shaft 311; a connecting means 5 connecting the rotating 
plate 4 to the arm a in the above-and-below relation and floatingly 
passing through the borehole 31; a driving power source 6 for swinging 
being equipped on the underside of the arm a; and a curvilinear guide path 
22' being provided on the bottom of the base 3 or between the base 3 and 
the arm a to guide the swing slider 21'; wherein the arm a is put into 
swing through the driving power source 6 while being regulated by the 
swing slider 21' in the curvilinear guide path 22' so as to induce the 
film holder h to shift analogously to the dental arch d of the subject p, 
thereby the focusing X-ray beam b from the X-ray source x coming to incide 
intersecting substantially at right angles successively to any given 
neighboring point of individual teeth t in the dental arch d, and further 
thereby the face exposed to the X-ray beam b of the film f in the film 
holder h being able to shift in the substantially equidistant relation to 
any tooth t in the dental arch d. 
The apparatus in this embodiment is the one which adapts the principle and 
method illustrated in FIG. 6, as mentioned above, wherein first is drawn 
the normal line h.sub.o passing through the neighboring point t.sub.o of 
the first two central incisors t.sub.1 and t.sub.1 in the dental arch d. 
This normal line h.sub.o is to be congruent with the axis a.sub.o of the 
arm a and also the X-ray beam b. On the normal line h.sub.o is taken an 
arbitrary point f.sub.o at a distance outside the point of contact t.sub.o 
of the incisors t and t. This arbitrary point f.sub.o serves as the seat 
of the face of the film f. And also at a distance inside the point of 
contact is taken on the normal line h.sub.o another arbitrary point 
g.sub.o. Now the neighboring point t.sub.o on the normal line h.sub.o is 
forced to shift along the dental arch line d.sub.1 so as to become 
substantially the normal line h.sub.o to any given neighboring point 
t.sub.o of individual teeth t on the dental arch line d.sub.1 each time of 
the shifting movement of the neighboring point t.sub.o. Then another 
arbitrary point g.sub.o shifts as g.sub.o 1, g.sub.o 2, g.sub.o 3 . . . in 
the Figure to give a translating curvilinear motion 10. On the other hand, 
a fixed line i.sub.o is drawn from the point g.sub.o rectangularly to the 
normal line h.sub.o, and an arbitrary point j.sub.o is taken on the fixed 
line i.sub.o. If the point j.sub.o is caused to translate as j.sub.o 1, 
j.sub.o 2, j.sub.o 3 . . . in the Figure, another translating curvilinear 
motion 20 will be given with the shifting movement of the normal life 
h.sub.o. 
The form of the curvilinear guide path 22 of the apparatus in the 
above-described example has been designed so as to fit exactly to the 
curvilinear motion 20 which was given by the aforesaid principle. The 
shaft bearing a.sub.1 in this apparatus is a type of radial bearing, which 
is to be placed in a hole a.sub.4 bored in an enlarged part a.sub.3 which 
is stretching from the arm a. In this embodiment, branch arm a.sub.2 is 
projecting in the rectangular direction to the axis a.sub.1 of the arm a 
and that in the immovable relation to the arm a. On the axis a.sub.21 of 
this branch arm a.sub.2 is provided a swing slider 21. The base 3 is 
provided above the arm a fixedly on the wall or ceiling of the room or 
else with the use of some suitable means. The borehole 31 provided nearly 
in the middle part of the base 3 is formed with the object of not 
obstructing shifting movement of the connecting means 5 which is provided 
to shift in proportion as the point of intersection g.sub.o of the axis 
a.sub.o of the arm a intersecting the axis a.sub.21 of the branch arm 
a.sub.2 and the axis a.sub.o of the arm a a driving point for swinging. In 
this embodiment, on the position where a driving point for swinging is 
expected to be formed, however, is not provided a slider, but exists only 
an imaginary curvilinear guide path 12' for swinging. This is for the 
purpose of aiming at the more smoothly swinging of the arm a. Accordingly, 
it may be said that the borehole 31 functions here similarly to a 
curvilinear guide path. The rotating plate 4 is for suspending the arm a 
practically. The base 3 is provided fixedly. The connecting means shifting 
within the borehole 31 provided in the base 3. In such an arrangement, the 
rotating plate 4 is designed to rotate with the rotor shaft 311 as a 
fulcrum within a sectoral sphere. It is for this reason that the 
connecting means 5 is made to pass through the borehole 31 floatingly. In 
the capacity of the connecting means 5 is employed in this illustration a 
bolt. The aforesaid driving power source 6 for swinging comprises of a 
motor M and a roller 61. The sliding platform a.sub.5 for the roller 61 is 
provided immovably below the radial bearing a.sub.1 on the front end of 
the connecting means 5. 
In this connection, the above-mentioned branch arm a.sub.2 is not limited 
to be provided projecting only in the direction intersecting at right 
angles to the arm a. There is also no limitation in the number of it; not 
only one piece but also plural ones may be set so far as they are provided 
in the immovable relation, not to speak of the possibility of providing at 
will so many corresponding guide paths independently. The guide path 22' 
in the illustration is embedded directly in the under face of the base 3, 
but a similar guide groove can be bored in plate body fixed horizontally 
between the base 3 and arm a (not shown). The reference letters R in FIGS. 
7 and 8 indicate a roller for swinging. 
With the foregoing in mind, reference will be now directed to the main 
point of operation and its working effect of the apparatus in the 
above-mentioned second example. As seen in FIGS. 7 and 8, when the arm a 
is urged to swing in the direction of the arrow a' by dint of the driving 
power source 6, the face of the film f in the X-ray film holder h shifts 
describing such a locus as S in FIG. 7, as a result of the slider 21' on 
the branch arm a.sub.2 being regulated by the curvilinear guide path 22'. 
This shifting locus is the one that is thoroughly congruent with the 
shifting locus described by the arbitrary point f.sub.o on the normal line 
derived from the principle illustrated in the previously explained FIG. 6. 
In FIG. 6, the length 1 between the neighboring point t.sub.o and the 
arbitrary point f.sub.o both lying on the normal line at any given time is 
always definite and unchangeable, so that the face of the film f shifts 
analogous to the dental arch d while keeping the substantially equidistant 
relation to any given tooth t in the dental arch d. On the other hand, 
since the form of the curvilinear guide path 22' in this apparatus has 
been determined substantially on the basis of the normal line h.sub.o 
passing through each of the neighboring points t.sub.o of an individual 
tooth t, it is evident for everybody that the axis a.sub.o of the arm a 
which swings being regulated by the above-mentioned curvilinear guide path 
22', that is, the very X-ray beam b comes to incide intersecting 
substantially at right angles to any given neighboring point t.sub.o of 
individual teeth t. Hence, like the case of the apparatus in the first 
example, in the apparatus in this second example, also, it is made 
possible to obtain clear and distinct images having a constant and stable 
enlargement ratio without any superimposition. Into the bargain, not more 
than a single slider will do in this apparatus, as a result leading to the 
guarantee of the more smooth swinging movement of the arm a. 
As understood clearly from the above-mentioned, the method and apparatus 
according to the invention may be said to be an excellent one which has 
succeeded in solving at a stroke the controversial points hitherto in 
question. 
Having described our invention as related to the embodiment shown in the 
accompanying drawings, it is our intention that the invention be not 
limited by any of the details of description, unless otherwise specified, 
but rather be construed broadly within its spirit and scope as set out in 
the accompanying claims.