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The invention relates to a process for at least two-dimensional
determination of the relative movement between an upper jaw and a lower
jaw and to a measuring arrangement for embodying this process.
In dental technology and dental medicine it is often necessary to measure
the movement of the lower jaw relative to the upper jaw and to store the
data obtained. This is especially necessary when the jaw movement is to be
simulated in a so-called "articulator," for which to start with it is
necessary to determine the respective position and movement of the lower
jaw relative to the upper jaw of a patient and to transfer the values thus
determined to the articulator or to compare them with the simulated
movements in this articulator.
For the determination of the relative movement between the human lower jaw
and the human upper jaw, devices have already been suggested which are
designed in principle so that on both sides of a patient's skull, in the
region of the jaw joints, measuring arrangements are placed which each
consist of two transmitter elements, one of which is connected with the
upper jaw and one with the lower jaw, and in each measuring arrangement
the relative movement between the two transmitter elements is determined
in three axial directions. These known devices or measuring arrangements
have the disadvantage, among others, that due to the system the measuring
results obtained with these arrangements are not error-free, the placement
of the transmitter elements, especially on the lower jaw of a patient, is
not without problems and, above all, due to cumbersome equipment the
natural movement of the lower jaw relative to the upper jaw is
practically, at least psychologically, hindered.
The object of the invention is thus to demonstrate a process for at least
two-dimensional determination of the relative movement between an upper
jaw and a lower jaw and a measuring arrangement for embodying this process
which, with simple means, leads to substantially more precise results and
above all makes possible the direct determination of the relative movement
between the lower jaw and the upper jaw.
To solve this task, a process according to the invention corresponding to
the characterizing section of claim 1 and a measuring arrangement for
embodying this process corresponding to the characterizing section of
patent claim 15 is designed.
In the process according to the invention, the at least two-dimensional
determination of the relative movement between the upper jaw and the lower
jaw occurs preferably in that, on the side of this jaw facing the
optoelectric device in a two-dimensional determination of the movement at
least two, and in a three-dimensional determination of the movement at
least three or four spatially staggered reference marks are placed on each
jaw and in the latter case the mutual position the reference marks exhibit
on each jaw and the position of the reference marks on one jaw relative to
the reference marks on the other jaw, as well as the changes in these
positions, are optically detected and from this, preferably by using a
computer (computer-aided), the relative movement of both jaws is
determined.
In one embodiment of the invention the optical detection of the mutual
position of the reference marks and the change in this position occurs
with the aid of at least one video camera, preferably with at least one
color video camera and in the electrical frames provided by this camera,
preferably after intermediate storage in an image storage device, the
available reference marks and their mutual positions are determined and
the data which describe the position of the reference marks for the
determination of the relative movement between the jaws are evaluated in a
computer according to a preset program.
The localization of the reference marks in the electrical frames can thus
occur, for example, in that these frames are each scanned by line and
column according to the reference marks which stand out prominently from
the remaining video signal or frame contents. As a criterion for the
localization of the reference marks in the frames, a particular brightness
and/or a particular coloration of the reference marks are suitable.
In another embodiment of the invention, the optical detection of the mutual
position of the reference marks and the change in this position occurs
with the aid of at least one laser device which emits at least one laser
beam and with this laser beam the measuring area formed by the reference
marks is scanned by line and column. Only when the scanning laser beam
strikes a reference mark does the reference mark reflect a part of the
laser beam on a light detector provided on the optoelectric device. From
the solid angle exhibited by the scanning laser beam each time it
intersects a beam reflected on the light detector relative to an original
position, optionally using additional remote measurement between the laser
device and the respective reference mark, the position of this reference
mark is determined and stored in a memory. From stored data of all
reference marks, the relative position which the reference marks or both
jaws exhibit toward each other and the relative movement of these jaws can
be determined. Especially in the determination of the relative movement
between the lower jaw and the upper jaw, at least four of the reference
marks are formed on each reference element.
"At least two-dimensional determination of the relative movement" means a
determination of the relative movement in at least two space axes which
run perpendicular to each other. "Observation axis" means the axis in
which the measuring area formed by the reference marks is detected by the
optoelectric device.
Further developments of the invention are the subject of the subclaims.
The invention will be further explained in the following based on the
figures on one embodiment. Shown are:
FIG. 1 A diagrammatic drawing of the design of a measuring arrangement for
three-dimensional determination of the relative movement between the human
upper jaw and the lower jaw in a side view using a video camera;
FIG. 2 The reference marks of the measuring arrangement placed on the front
teeth or incisors of a human upper or lower jaw according to FIG. 1 in the
viewing direction of arrow A in FIG. 1;
FIG. 3 A diagrammatic drawing of a measuring arrangement using two video
cameras;
FIG. 4 A diagrammatic drawing of a measuring arrangement using a laser
device;
FIG. 5 A diagrammatic drawing of a measuring arrangement using two laser
devices;
FIG. 6 A diagrammatic drawing of a further embodiment of the measuring
arrangement with laser device;
FIGS. 7 to 9 A diagrammatic drawing of further embodiments of the measuring
arrangement.
The measuring arrangement shown in FIG. 1 is for three-dimensional
measurement of the relative movement between the upper jaw and the lower
jaw of a patient, and because of the simpler drawing only a single incisor
1 or 2 each is shown from the upper jaw and the lower jaw. On the front
side of the existing incisors 1 of the upper jaw, a striated, curved
holding element 3, preferably one made of thermoplastic material, is
fastened by gluing or by another suitable way. A similarly designed
holding element 4 is fastened on the front side of incisors 2 on the lower
jaw. On the surface side facing away from incisors 1 or 2, each holding
element 3 or 4 has a rodlike element 5 or 6, which extends outward with
its free end above the holding element concerned, lies longitudinally
perpendicular to the surface sides of the holding element involved and is
connected, on its free end, to one vertex 7 or 7' of a pyramidlike body 11
or 12 which exhibits a total of four vertices 7, 8, 9, and 10 or 7', 8',
9', and 10'. Pyramidlike body 11 with vertices 7-10 forms, together with
rodlike element 5 and holding element 3, the one reference element 13 and
pyramidlike body 12 with vertices 7'-10', together with rodlike element 6
and holding element 4, forms the other reference element 14 of the
measuring arrangement. Both reference elements 13 and 14 are designed so
that, due to rodlike elements 5 or 6, pyramidlike bodies 11 or 12 are
placed with all their vertices outside the oral cavity in front of the
lips, vertices 7 or 7' exhibit a smaller distance from incisors 1 or 2 and
vertices 8, 9, and 10 or 8', 9', and 10' each exhibit a larger distance
from incisors 1 or 2 and further, in the embodiment shown, the axis of
rodlike elements 5 or 6 intersects the triangular surface opposite
vertices 7 or 7' and delineated by vertices 8, 9 and 10 or 8', 9' and 10'
at an angle of about 90.degree.. Pyramidlike bodies 11 and 12 are
furthermore placed so that the triangular surface delineated by vertices
8-10 or 8'-10' each exhibits an upper, essentially horizontal lateral
length between vertices 8 and 10 or 8' and 10' with vertex 9 or 9' placed
below this lateral length. Pyramidlike bodies 11 and 12 consist of rodlike
elements 15 or 16 connected to each other at vertices 7-10 or 7'-10' and
each of the same length in the embodiment shown so that even the
respective rear vertex 7 or 7' in the viewing direction (arrow A) is
completely visible. On rodlike element 16 of reference element 14
connecting vertices 7' and 9' a light source 17 is fastened, which emits a
focused light beam 18 vertically upward which, in the measuring
arrangement shown, strikes a mirror 19 placed in the plane of vertices 7,
8, and 10 of reference element 13 or fastened to rodlike element 15 there
and light beam 18 is reflected forward on this mirror, as indicated by
reflected light beam 18'. Since mirror 19 is slanted relative to a
horizontal axis in whose direction the axes of rodlike elements 5 and 6
are approximately in the embodiment shown, the reflected light beam shifts
upward or downward during a horizontal movement of the lower jaw relative
to the upper jaw in this horizontal axial direction (double arrow H), as
indicated in FIG. 1 with dotted line 18", and this shift is a measure of
the relative movement of the lower jaw and upper jaw in the direction of
double arrow H.
Vertices 7-10 or 7'-10' are, compared with the other parts of reference
element 13 or 14, designed to be prominent in contrast or in brightness
and/or in coloration and preferably exhibit a coloration which is markedly
different from facial color, but also from the color of the lips.
The measuring arrangement furthermore consists of a video camera 20, which
is placed at a present distance from the patient sitting on a stool, for
example, and is aimed with its lens in viewing direction (arrow A) at the
mouth of the patient or at reference elements 13 and 14 fastened on
incisors 1 and 2. With the video camera, movement of reference elements 13
and 14 or the displacement of vertices 7-10 and 7'-10' and the change in
position of reflected light beam 18' produced during a relative movement
between the lower jaw and the upper jaw (chewing, etc.) is recorded. The
corresponding video signals are then stored in an image storage device 21,
which for example is formed at least partially by a video recorder. With
the aid of an electronic switch 22, the frames stored in image storage
device 21 can be scanned by line and column and a signal is transmitted to
a memory 23 if, during this scanning, one of the prominently designed
vertices 7-10 or 7'-10' or reflected light beam 18', especially prominent
due to its brightness, is detected. From the respective scanning phases
results the position of the vertex or of reflected light beam 18' detected
each time so that the electrical signals or data characteristic of this
position can be stored in memory 23. The data stored in memory 23 can then
be fed to a computer 24 which, from this data, determines the relative
movement between the upper jaw and lower jaw according to a suitable
program. The data thus obtained can then be channeled to the various
further purposes, or for use in the most diverse applications, for example
for optical display of the relative movement between lower and upper jaw,
for expressing the chronological progress of the various movement
components of this relative movement, etc. Furthermore, this data can also
be stored and used later for comparison with the relative movement between
lower and upper jaw simulated in a dental articulator.
In FIG. 3 a further measuring arrangement is shown, which differs from the
measuring arrangement according to FIG. 1 essentially in that in addition
to video camera 20 another video camera 25 with associated image storage
26 and associated electronic switch 27 is provided. Image storage device
26 and electronic switch 27 correspond in their function to image storage
device 21 and electronic switch 22. Video camera 25 is, in the same way as
video camera 20, placed at a preset distance from the patient sitting on a
stool, for example, and its lens is aimed in viewing direction (arrow A')
at the mouth of the patient or at reference elements 13 and 14 fastened to
incisors 1 and 2; however in the embodiment shown in FIG. 3 the optical
axes (arrows A and A') of both video cameras 20 and 25 together enclose an
angle of 45.degree. which opens toward the side of the measuring
arrangement facing video cameras 20 and 25, i.e., opened to the left side
in the representation chosen for FIG. 3. The video signals provided by
video camera 25 are stored in image storage device 26 which, for example,
is in turn at least partially made with a video camera. Of course, another
suitable memory can be used for image storage device 26 and image storage
device 21. With the aid of electronic switch 27 the frames stored in image
storage device 26 can be scanned by line and column and a signal is always
transmitted to memory 23 also connected to electronic switch 27 when
during this scanning one of the prominently designed vertices 7-10 or
7'-10' which form the reference marks during measurement is detected. From
each scanning phase results the position of the vertex determined in turn
by video camera 25, so that this position, together with the position of
the vertices picked up by video camera 20, can be stored in memory 23. The
data stored in memory is then fed to computer 24 which, from this data, in
turn determines according to a suitable program the mutual position
exhibited by vertices 7-10 or 7'-10' on each reference elements 13 or 14
and the position occupied by individual reference marks 7-10 of reference
element 13 relative to reference marks 7'-10' of reference element 14 thus
determining the relative movement between the upper jaw and the lower jaw.
The embodiment shown in FIG. 3 has the advantage that, for movement in the
direction of double arrow H, light source 17 and mirror 19 are not
necessary, rather the direction of movement in this horizontal axis can be
determined by the optical axes, slanted toward each other, of video
cameras 20 and 25.
Of course it is also possible in the embodiment shown in FIG. 3 to connect
both video cameras 20 and 25 to a single image storage device exhibiting
two channels or memories whose output signal is then evaluated with a
single electronic switch in the multiplex process, specifically in an
initial period at first the video signal of video camera 20 and in a
subsequent period the video signal of video camera 25. Independently of
this, in the embodiment according to FIG. 1 and in the embodiment
according to FIG. 3, image storage devices 21 or 26 can of course be
eliminated and then the signal provided respectively by video camera 20 or
25 is evaluated immediately in a corresponding electronic switch 22 or 27
in the way described above. Independently of this it is further possible
to conduct the evaluation of the signals provided by video cameras 20 or
25 or the determination of the position of vertices 7-10 or 7'-10' in
such a way that the position of vertices 7-10 or 7'-10' described in the
video pictures of video cameras 20 or 25 is compared with a preset optical
or electronic grid and, from this comparison, the actual position of the
named vertices is determined. This can also occur, for example, in that in
electronic switch 22 or 27 an electronic grid is generated such that
during the line and column scanning or detection by the corresponding
video signal the distance appearing during scanning of the signal
corresponding to the one vertex 7-10 or 7'-10' is detected by line and
column by a preceding or subsequent grid signal and from this, taking into
account this grid signal which defines a certain position, the actual
position of the vertex 7-10 or 7'-10' involved is determined. Especially
with a correspondingly fine grid division an especially great accuracy in
the determination of the actual position of vertices 7-10 or 7'-10' can be
achieved in this way.
The measuring arrangement shown in FIG. 3, in which reference elements 13
and 14 are viewed from two viewing directions (A, A') which together
enclose an angle, can also be made with a single video camera when the
reference marks are viewed with this camera through a mirror device
alternating each time from the one viewing direction and next from the
other viewing direction, so that in chronological sequence such signals
from both viewing directions are fed to the image storage device or to the
electronic switch for evaluation of the video signals.
FIG. 4 shows an embodiment in which the determination of the position of
vertices 7-10 or 7'-10' occurs not with the aid or one or more video
cameras, but with the aid of a laser device 28. This device consists of a
laser 29 which emits a point-shaped or highly focused light beam 30 of a
preset wavelength, of a deflection or scanning device 31 exhibiting two
deflection mirrors for light beam 30, of light detector 32 and of an
electronic measuring and evaluation device 33 whose output is in turn
connected to memory 23 for computer 24. Laser device 28 is placed at a
predetermined distance from the patient sitting on a stool, for example,
in such a way that light beam 30' deflected with the deflection device
scans by line and column, in two axial directions running mutually
perpendicular, for example in the vertical axis and in the transversal
axis running perpendicular to the plane of the drawing, the measuring area
formed by vertices 7-10 and 7'-10' of reference elements 13 and 14. Light
beam 30" thus reflected on light detector 32 is converted in this detector
into an electrical signal which is fed to measuring and evaluation device
33, specifically together with a signal derived from deflection device 31
and this signal accounts for the respective spatial angle exhibited by
light beam 30', for example, relative to a reference axis. From these
signals and optionally from another signal derived from laser 29 or a
control device not further shown (based on the respective angular
deviation of light beam 30' and on the distance exhibited by reference
marks 7-10 or 7'-10' from laser device 28 in horizontal axial direction H)
the actual position of these reference marks is determined in the
measuring and evaluation device and the corresponding values are
transmitted by the measuring and evaluation device to memory 23. The
distance measurement necessary for the determination of the position of
the reference marks is carried out in the measuring arrangement shown in
the same way as is customary with corresponding distance measurement
devices which operate with a laser light beam. For this distance
measurement the transit time between emitted light beam 30 and the light
beam striking detector 32 can, for example, be used in a pulsed laser 29.
For the determination of the distance, an angle measurement between
vertices 7-10 or 7'-10' each placed on reference elements 13 and 14 at a
preset distance to one another can also be used. Furthermore, an
interference measurement to determine the distance is also possible.
FIG. 5 shows, in simplified form, a further embodiment of the measuring
device which differs from the embodiment according to FIG. 4 in that two
laser devices 28 are provided which each synchronously scan the measuring
area, i.e., the vertices 7-10 or 7'-10' with a light beam 30', but
preferably with various wavelengths. Both laser devices 28 are placed at a
spatial distance from each other so that scanning light beams 30' emitted
by these laser devices each enclose an angle with each other and thus,
from the signals provided by the measuring and evaluation devices 33 of
laser devices 28, the respective position of vertices 7-10 or 7'-10' or
the change in this position in the horizontal axial direction can be
determined without the necessity of the distance measurement by laser
device 28 as described above in connection with FIG. 4.
The rotation or movement of scanning light beam 30' can of course in the
embodiments according to FIGS. 4 and 5 also be achieved in that laser 29
or a part of the particular laser device 28 exhibiting this laser can be
mutually rotated in two spatial axes perpendicular to each other.
Furthermore it is also possible, in principle, in the embodiment shown in
FIG. 5 to achieve both scanning light beams 30' in that one light beam
emitted from a single laser 29, for example, is divided into both light
beams 30' using a semitranparent mirror and in this case both laser
devices 28 at least partially form a common device.
FIG. 6 shows a simplified representation of a further embodiment of a
measuring device operating with a laser beam. This has a laser 34 which in
turn is placed at a distance from the measuring area, i.e., from reference
elements 13 and 14 and which emits a focused light beam 35. The method of
operation of this measuring arrangement is based essentially on the fact
that one of the two bodies whose relative movement is to be measured is
stationary and only the other body is moving. Light beam 35 is aimed in
this measuring arrangement at a prominent reference mark of the moving
body, i.e., for example at vertex 7' of reference element 14 fastened to
the lower jaw. The latter occurs either by manual adjustment of laser 34
or by rotating this laser first for achieving a line- and column-scanning
movement of light beam 35 and then, when light beam 35' is reflected on
light detector 36 by the prominent reference mark, i.e., by vertex 7', the
rotation movement of laser 34 is interrupted by a signal generated by this
light detector and laser 34 next maintains the most recent position
assumed. During movement of vertex 7' laser 34 is carried along or turned
so that light beam 35 constantly strikes vertex 7' so that from this
turning movement, which laser 34 performs while being carried along, the
movement of vertex 7' in the vertical and transversal axial direction,
i.e., in the plane perpendicular to the plane of the drawing in FIG. 6,
can be very precisely determined. The control criterion for carrying along
laser 34 is light beam 35' striking detector 36, i.e., by an automatic
electric control driven by detector 36, laser 34 is correspondingly guided
so that light beam 35' reflected on detector 36 generates a maximum signal
at the output of this detector. To achieve a direction select during the
tracking of laser 34, the measuring device exhibits a means which sets the
direction of movement of vertex 7' in the respective axial direction. This
is, for example, possible by using a photodiode with limiting illuminated
field or also by having laser 34 perform, in addition to the tracking
movement, an oscillating movement around both axial directions, around
which laser 34 is rotated during tracking so that then from the point at
which, in this oscillating movement, the maximum of the signal provided by
detector 36 strikes, the direction of movement of vertex 7' in both axial
directions can be determined.
In connection with a distance measuring device the movement of vertex 7' in
the horizontal axial direction can be determined with the measuring device
according to FIG. 6. Without this distance measuring device, the measuring
arrangement of FIG. 6 is usable when a movement of the reference mark or
vertex 7' is to be anticipated in only one plane. The measuring device
according to FIG. 6 can, however, also be combined with other previously
described measuring devices.
A further embodiment is shown in FIG. 7. In this embodiment, on the upper
and lower jaw of head 37 of a patient only the three respective reference
marks 8-10 or 8'-10' are provided, which again are spatially staggered and
form the vertices of a triangle. Reference marks 8-10 or 8'-10' are formed
each on a reference element 38 or 39 and each reference element is
provided for fastening on the upper or lower jaw or on the rows of teeth
there on a biting fork. To make possible a three-dimensional determination
of the relative movement between upper jaw and lower jaw, in this
embodiment two optoelectronic devices 40 and 41 are provided, which are
placed spatially staggered so that they cover the measuring area formed by
reference marks 8-10 and 8'-10' from two different axial directions
(viewing axes).
FIG. 8 shows a similar embodiment as in FIG. 7 and in the embodiment
according FIG. 8, on the lower jaw there are however two pairs of three
reference marks each, formed by reference marks 8'-10' and reference marks
8"-10", and reference marks 8'-10' or 8"-10" of each pair are spatially
staggered so that they again form the vertices of a triangle, and both
triangles are placed like mirror images at a middle plane M which is
vertical and perpendicular to the front side of head 37 and reference
marks 10' and 9' or 10" and 9", which form the sides of the triangle
adjacent to middle plane M, are each provided in a vertical direction
above one another. Reference marks 8'-10' are provided on a reference
element 39' and reference marks 8"-10" on a reference element 39". Both
reference elements 39' and 39" are fastened separately on the lower jaw,
specifically, for example, with the aid of parts 44 and 45 or a two-part
biting fork 46, and reference marks 8'-10' are provided on part 44 and
reference marks 8"-10" on part 45. This embodiment has the advantage that,
with devices 40 and 41, not only is a three-dimensional detection or
measurement of the relative movement between the upper jaw and the lower
jaw possible, but with these devices, deformations of the lower jaw which
occur during movement of the lower jaw or in chewing can be detected. In
the embodiment shown in FIGS. 8 and 9 a total of six reference marks
8'-10' and 8"-10" are provided. In principle, a total of five reference
marks would be enough. If the deformation of the upper jaw is to be
detected, reference marks 8-10 are provided on the lower jaw and reference
marks 8'-10' and 8"-10" on the upper jaw.
In the embodiments shown in FIGS. 7 and 8, reference marks 8-10, 8'-10' or
8"-10" are each placed so that the sides of the triangles formed by the
reference marks face devices 40 and 41, viewing axes 42 and 43 of these
devices placed at a distance from the front side of head 37 form an angle
with the side of these triangles.
The invention was explained above based on embodiments. It is understood
that changes and modifications are possible without leaving the basic idea
of the invention. Thus it is for example also possible that instead of
using the reference marks formed by vertices 7-10 or 7'-10' on reference
elements 13 and 14, at least on one of the two bodies, for example on the
head or skull of the patient, such reference marks can be used which are
placed there directly. The light detectors 32 and/or 36 used in the
invention are photodiodes or photodiode arrangements or other suitable
photoelectric converters which generate an electrical signal when struck
by light, as for example phototransistors or photoresistors.
To simplify the localization and/or identification of the reference marks
during the determination of the relative movement, these reference marks
can also be formed from light-emitting elements (light diodes, for
example), which then, for example, emit respectively light of different
coloration and/or brightness and/or wavelength and/or modulated light,
i.e., intensity-modulated light, and here it can be advantageous for the
identification of the individual reference marks that the light emitted
from at least a part of the reference marks differs in modulation
frequency from the light of the other reference marks.
Of course, prominent points or lines made on reference elements or bodies
can also be used as reference marks.
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