Dental Pantograph

This invention relates to a dental Pantograph wherein movement of the mandible with respect to the maxilla is measured along three orthogonally positioned transducers located at each hinge axis of the temporomandibular joint. Measurements are made by the movement of the transducers made in response to movement of the mandible with respect to the maxilla.

The human jaw includes the lower jaw bone, the mandible, which is pivotally mounted to the upper jaw bone, the maxilla, at the temporomandibular joint. The attachment is via a loose ball and socket type joint wherein a fossa on both the right and left side of the maxilla receives a condyle on both the right and left side of the mandible.

The fit of the condyles in the fossa is rather loose, allowing for extensive movement of the mandible with respect to the maxilla. Not only can the mandible move up and down with respect to the maxilla, but it can be moved backward and forward in a protrusive pathway and laterally, side to side. In executing the lateral movement, these condyles on the side on which the mandible is moving executes a rotation, whereas the condyle on the side away from the direction of movement executes orbiting. Accompanying the orbiting and rotation of the condyles are mandibulary side shifts. As such, the locus of movement of the individual condyle are complex in nature.

The complex movement of the mandible has been studied over the years in order to better understand the manner in which the teeth fit or occlude with respect to one another. Certain temporomandibular joint dysfunctions are the direct result of misocclusion of the teeth. Such misocclusion can lead to pain and stress and train of the various muscles which support and move the mandible.

Over the years, certain device have been constructed in order to measure and mimic the movement of the mandible. Pantographs have been constructed to measure the mandible movement and articulators have been constructed in order to mimic the movement of the mandible outside of the mouth in order to study and construct dental appliances for treatment of malocclusion and the like.

Because of the complex movement of the mandible as outlined above, many different expedients have been resorted to in construction of pantographic devices which could best trace and record the parameters of movement of the mandible. Many of these devices could be described; however, it is sufficient to say for the purposes of this discussion that for the most part, these devices were exceedingly tedious to use and the reproducibility of the devices, while slowly improving over the years, still leave much to be desired.

The dentist who utilizes such pantographs is a highly skilled professional whose time is exceedingly valuable. The trial and error use of the prior known pantographic devices was exceedingly wasteful for dentists' time. Furthermore, in those prior pantographic devices which produced condylar path tracings, not only was it necessary to spend an exceedingly protracted length of time in obtaining the tracings, it was then further necessary to follow the condylar path tracings while adjusting the articulator until such time that the movement of the articulator precisely followed the condylar path tracings.

In view of the above, it is evident that there exists a need for new and improved pantographs which eliminate the time consuming and tedious processes inherent in the existing pantographs. In view of this need, it is a broad object of this invention to provide a pantograph which provides a direct numerical readout to the operator of the same such that the readout can be directly entered to the dials of an articulator without having to attempt to follow condylar path tracings for setting the articulator. It is a further object of this invention to provide a pantograph whose use is rapid and accurate and thus further saves valuable professional time in obtaining the measurements of the condylar path movements. Additionally, it is an object of this invention to provide a pantograph which automatically records the condylar pathway during excursive movements of the mandible without necessitating extensive human readout of individual measuring devices.

These and other objects, as will become evident from the remainder of this specification are achieved in a pantograph device having a maxilla cross bow and a mandible cross bow with respective right and left side arms attaching to each of said maxilla and mandible cross bows with said respective mandible side arms moving with respect to said respective maxilla side arms in response to mandibulary movement an improvement which comprises: a right X axis scale; a right Y axis scale; a right Z axis scale; a left X axis scale; a left Y axis scale; a left Z axis scale; each of said scales being elongated and including a plurality of reference means located in a spaced array along their length; a right scale engagement means operatively connecting to one of said right side mandible and maxilla side arms, said right side scale engagement means for operatively associating said right X, Y and Z scales with said right side mandible and maxilla side arm to which said right side scale engagement means is operatively connected; a right scale orientation means operatively connecting to the other one of said right side mandible and maxilla side arms and positioned adjacent to but not in direct contact with said right scale engagement means, the one of said right scale engagement means and right scale orientation means operatively connected to the right side mandible side arm movable with respect to the one of said right scale engagement means and right scale orientation means operatively connected to said right side maxilla side arm in response to mandibulary movement, said right scale orientation means having orthogonal X, Y and Z axes, said right scale orientation means for orienting said right X, Y and Z scales with said right engagement means and for sensing said reference means on said right X, Y and Z scales; said right X axis scale operatively associated with said right scale orientation means and axially movable with respect to said right scale orientation means along said X axis and fixed against transverse movement with respect to said right scale orientation means along said Y and Z axes, said right X scale contacting said right engagement means and moving with respect to said right scale orientation means along said X axis in response to movement of said right side mandibulary side arm with respect to said right side maxillary side arm along said X axis; said right Y axis scale operatively associated with said right scale orientation means and axially movable with respect to said right scale orientation means along said Y axis and fixed against transverse movement with respect to said right scale orientation means along said X and Z axes, said right Y scale contacting said right engagement means and moving with respect to said right scale orientation means along said Y axis in response to movement of said right side mandibulary side arm with respect to said right side maxillary side arm along said Y axis; said right Z axis scale operatively associated with said right scale orientation means and axially movable with respect to said right scale orientation means along said Z axis and fixed against transverse movement with respect to said right scale orientation means along said X and Y axes, said right Z scale contacting said right engagement means and moving with respect to said right scale orientation means along said Z axis in response to movement of said right side mandibulary side arm with respect to said right side maxillary side arm along said Z axis; a left scale engagement means operatively connecting to one of said left side mandible and maxilla side arms, said left said scale engagement means for operatively associating said left X, Y and Z scales with said left side mandible and maxilla side arm to which said left side scale engagement means is operatively connected; a left scale orientation means operatively connecting to the other one of said left side mandible and maxilla side arms and positioned adjacent to but not in direct contact with said left scale engagement means, the one of said left scale engagement means and left scale orientation means operatively connected to the left side mandible side arm movable with respect to the one of said left scale engagement means and left scale orientation means operatively connected to said left side maxilla side arm in response to mandibulary movement, said left scale orientation means having orthogonal X, Y and Z axes, said left scale orientation means for orienting said left X, Y and Z scales with said left engagement means and for sensing said reference means on said left X Y and Z scales; said left X axis scale operatively associated with said left scale orientation means and axially movable with respect to said left scale orientation means along said X axis and fixed against transverse movement with respect to said left scale orientation means along said Y and Z axes, said left X scale contacting said left engagement means and moving with respect to said left scale orientation means along said X axis in response to movement of said left side mandibulary side arm with respect to said left side maxillary side arm along said X axis; said left Y axis scale operatively associated with said left scale orientation means and axially movable with respect to said left scale orientation means along said Y axis and fixed against transverse movement with respect to said left scale orientation means along said X and Z axes, said left Y scale contacting said left engagement means and moving with respect to said left scale orientation means along said Y axis in response to movement of said left side mandibulary side arm with respect to said left side maxillary side arm along said Y axis; said left Z axis scale operatively associated with said left scale orientation means and axially movable with respect to said left scale orientation means along said Z axis and fixed against transverse movement with respect to said left scale orientation means along said X and Y axes, said left Z scale contacting said left engagement means and moving with respect to said left scale orientation means along said Z axis in response to movement of said left side mandibulary side arm with respect to said left side maxillary side arm along said Z axis; right sensor means located on said right scale orientation means for sensing said reference means on said right X axis, Y axis and Z axis scales; left sensor means located on said left scale orientation means for sensing said reference means on said left X axis, Y axis and Z axis scales; each of said right sensor means and said left sensor means producing an output in response to sensing said reference means with said output indicating axial movement of said right X axis, Y axis and Z axis scales and said left X axis, Y axis and Z axis scales with respect to said right and left scale orientation means respectively in response to mandibulary movement.

Preferredly, a guide would be associated with each of the respective scales so as to guide those scales such that they can axially move with respect to the respective scale orientation means.

In the preferred embodiment, the right and left scale engagement means would each include three mutually perpendicular plates which are positioned in association with one another and with the respective guide means such that the plates are axially positioned from the guide means allowing the respective scales to move between the guide means and the plates. Further, in the preferred embodiment, the respective right and left scale orientation means would include a right and left housing with the respective guide means comprising openings located in the housing to allow the scales to move axially with respect to the housings. Further, biasing means would be associated with each of the scales with the housing means extending between the scales and their respective housings so as to bias the respective scales toward the respective plates.

In the preferred embodiment, the right and left sensor means in response to sensing the reference means would produce electrical signal corresponding to movements of their respective scales. Further, an electrical signal processing means would be operatively associated with the right and left sensor means so as to receive the electrical signals from the right and left sensor means and to produce an output corresponding to movement between the respective scale means and their associated sensor means. This movemeent is in response to mandibulary movement.

In the preferred embodiment, both the right and left sensor means would include a radiation transmitting means and a radiation receiving means each located in their respective housing and operatively associated with each other and with the reference mark on the respective scales. The radiation transmitting means would be capable of generating and propagating radiation toward the respective scales and the respective radiation receiving means would be capable of receiving this radiation and response to receipt of variations in the receipt of said radiation producing the electrical signals. The reference means, in interacting with the radiation transmitted by the radiation transmitting means would be capable, upon movement of the reference means, of causing a variation in the radiation further propagated toward the radiation receiving means.

Further in the preferred embodiment, the electrical signal processing means would include a digital logic device and a digitizing means capable of digitizing the electrical signals such that they can be processed by the digital logic device.

In the preferred embodiment, for measuring both direction of movement as well as degree of movement of each of the respective scales, each of the respective scales would include a first and a second radiation receiver associated with it. The first radiation receiver would receive radiation which has interacted with a first portion of the reference marks on any particular scale with the second radiation receiver responding to radiation which has interacted with a second portion of those reference marks. Each of the first and second radiation receivers would be capable of producing an electrical output in response to receipt of radiation. Further, the electrical outputs received from the first and the second radiation receivers associated with any particular scale would be out of phase with one another, preferredly 90 degrees out of phase.

Preferredly, the radiation is electromagnetic radiation, more preferredly in the wave length range of light radiation. As such, the radiation transmittors would preferredly comprise light emitting diodes and the radiation receivers would preferredly comprise photosensitive transistors.

Preferredly, each of the scales would be formed of a transparent material with the reference marks constituting opaque marks located along the scales. In addition, a reference scale can be associated with each of the scales with a second set of reference marks located on the reference scale. Preferredly, this second set of reference marks is divided into a first and second section, with the reference marks in the first section being displaced with respect to the reference marks in the second section.

This invention will be better understood when taken in conjunction with the drawings wherein:

FIG. 1 is an isometric view of a pantograph incorporating the principles of this invention;

FIG. 2 is an isometric view of a portion of the invention shown in FIG. 1;

FIG. 3 is an isometric view similar to FIG. 2 except taken at a different angle and with certain of the components attaching thereto exploded from the remainder of the components;

FIG. 4 is a further explosion of a portion of the components seen in FIG. 3;

FIG 5 is a side elevational view in partial section about the line 5--5 of FIG. 4;

FIG. 6 is an enlarged view of a portion of FIG. 5;

FIG. 7 is a side elevational view in partial section about the line 7--7 of FIG. 5;

FIG. 8 is an isometric view of a portion of the invention seen in FIG. 1 with certain overlaying components removed to show interaction of other components;

FIG. 9a is a representational view, including certain schematic circuit elements of operation of the invention;

FIG. 9b is a symbolic depiction of certain wave forms of certain of the elements seen in FIG. 9a with phantom lines utilized to align the wave forms; and

FIG. 9c is a symbolic depiction of certain logic states aligned with the phantom lines of FIG. 9b to correlate these states with the wave forms of FIG. 9b.

This invention utilizes certain principles and/or concepts as are set forth in the claims appended to this specification. These principles and/or concepts are capable of being utilized in a variety of embodiments differing from the exact illustrative embodiment utilized for illustrative purposes herein. For this reason, this invention is not to be construed as being limited to the exact illustrative embodiment but is only to be construed as being limited by the claims.

In FIG. 1 a dental pantograph 20 is shown. Collectively making up the dental pantograph would be a mandible cross bow 22, a maxilla cross bow 24, a right side (as viewed from the patient's head) maxilla side arm 26, a right side mandible side arm 28, a left side maxilla side arm 30 and a left side mandible side arm 32. The cross bows and side arms 22, 24, 26, 28, 30 and 32 are essentially standard in appearance and function as per existing dental articulators.

Approximate maxilla and mandible clutches, not shown or numbered, would attach to the cross bows 24 and 22 at attachment junctions 34 and 36, respectively, on the respective cross bows. Insofar as such clutches are known in the art, for brevity of this specification, they are neither shown nor described.

The maxilla side arms 26 and 30 are attached to the maxilla cross bow 24 at junction members 38 and 40, respectively, and are adjustable with respect to the cross bow 24 via knurled knobs 42 and 44, allowing for correct hinge axis alignment, as hereinafter explained, of the maxilla side arms 26 and 30. The maxilla side arms 26 and 30 are movable backward and forward via the knurled knobs 42 and 44 and can be rotated about the cross bow 24 via the junction members 38 and 40 to align components as hereinafter described along the hinge axis of the right and left temporomandibular joints of the patient.

Likewise, the mandible side arms 28 and 32 are attached to the mandible cross bow 22 via junction members 46 and 48 with backward and forward and rotational movement of these arms 28 and 32 with respect to the cross bow 22 accomplished via loosening and tightening of the junction members 46 and 48.

With the pantograph 20 correctly placed with respect to the patient's jaw and with certain components which attach to the maxilla and mandible side arms 26, 28, 30 and 32 correctly positioned as hereinafter explained, the practitioner guides the patient's jaw through standard excrusive movements to move the patients's mandible with respect to his maxilla such that the mandible movements are transferred via the above described clutches to the mandible cross bow 22. Movement of the maxilla cross bow 22 with respect to the mandible cross bow 24 results in corresponding movement of the mandible side arms 28 and 32 with respect to the maxilla side arms 26 and 30. In response to mandibulary movement the temporomandibular joint ends 50 and 52 of the respective mandible side arms 28 and 32 move in pathways which can be broken down in a three dimensional coordinate system along X, Y and Z axes.

By measuring the movement of the ends 50 and 52 (or more accurately, movement of other components as hereinafter explained attached to these ends) along the X,Y and Z axes with respect to the stationary maxilla side arms 26 and 30 (or more accurately, other components as hereinafter explained attached to these side arms 26 and 30) movement of the right and left mandibulary condyles in the respective right and left temporomandibular joints can be ascertained.

A right scale housing 54 attaches to the end 50 of the right mandible side arm 28. Likewise, a left scale housing 56 attaches to the end 52 of the left mandible side arm 32. The housings 54 and 56 are mirror images of one another. In view of this, detailed description of only one of the housings, housing 56, will suffice for describing both of the housings, with the only difference being the spatial orientation with respect to the mirror imagery between the two housings 54 and 56.

A right side X axis scale 58, Y axis scale 60 and Z axis scale 62 are slidably mounted to the housing 54. Likewise, a left X axis scale 64, Y axis scale 66 and Z axis scale 68 are movably mounted to the left scale housings 56. The right scales 58, 60 and 62 function as per the left scales 64, 66 and 68 except for the same mirror imagery which exists between the housings 54 and 56. For the same reason then, only the scales 64, 66 and 68 will be described in detail, with the function of the other scales 58, 60 and 62 working in an equivalent manner except on the right side of the apparatus 20.

A right side engagement member 70 attaches to end 72 of the right side maxilla side arm 26. Likewise, a left side engagement member 74 attaches to end 76 of the left side maxilla side arm 30. As with the housings 54 and 56, a mirror imagery exists between the engagement members 70 and 74. For this reason, only the engagement member 74 will be described in detail. The equivalent parts, except for the mirror imagery exist on the engagement member 70 but in the interest of brevity will not be described.

Referring now to FIG. 8, the member 74 is seen in detail. The member 74 is composed of a X axis plate 78, a Y axis plate 80 and a Z axis plate 82 which are integrally formed together, preferredly from a transparent resin such that the plates 78, 80 and 82 are orthogonally located with respect to one another with side edge 84 being a mutual edge between plates 80 and 78 along the X axis, side edge 86 being a mutual edge between the plates 78 and 82 along the Y axis and side edge 88 being a mutual edge between the plates 80 amd 82 along the Z axis. Together, the plates 78, 80 and 82 form three sides of a box-like structure with the angles between the edges 86, 88 and 90 being respective right angles.

A small boss 92 is located on plate 82 and projects outwardly along an X axis in a direction toward the head of the patient. A transparent protractor 94 having suitable indicia 96 located thereon is hinged about the boss 92 to the engagement member 74. The protractor 94 includes a horizontal aligning arm 98 and the plate 82 includes a reference mark 100 which is utilized in conjunction with the indicia 96. Centering indicia 102 are printed on the plate 88 about the center of the boss 92.

The right and left hinge axis of the mandible are appropriately located on the patients head utilizing normal techniques. Further, a horizontal alignment line is also located. The engagement members 70 and 74 are then positioned with respect to the right and left hinge axis as follows for the engagement member 74. The boss 92 is centered at the hinge axis mark and the horizontal alignment arm 98 is aligned with the horizontal mark. The starting angle of the maxilla side arm 30 can then be read off the protractor 94 with respect to the reference line 100.

Referring now to FIGS. 2 through 7, the housing 56 and the scales 64, 66 and 68 and other components attached thereto are shown. In FIG. 3 the housing 58 is oriented essentially as seen in FIG. 2. In moving from FIG. 3 to FIG. 2 the housing 58 has been rotated 90 degrees twice about axis which are perpendicular. For FIG. 4, certain other components which are seen in the exploded part of FIG. 3 have been withdrawn from the interior of the housing 56 and exploded with respect to one another so as to further illustrate the construction of the same. For FIG. 5 the scale 66 has then been added to these components to show the relationship of the scales to the components. A portion of FIG. 5 is then enlarged within FIG. 6 and a sectional view taken at a different angle about the line 7--7 of FIG. 5 seen in FIG. 7.

Displaced to the right hand side of FIG. 3 in phantom line is a set of coordinates showing positioning of the housing 56 with respect to an X, Y and Z axis. Along the X axis, the scale 64 fits into an X axis passageway 104 which extends through the housing 56 along the X axis. Similarly, the scale 66 fits into a Y axis passageway 106 with the scale 68 fitting into a Z axis passageway 108. In FIG. 3 one end of the passageways 104 and 106 for the scales 64 and 66 are seen, whereas the opposite end of the passageway 108 for scale 68 is seen.

The housing 56 has three hollow chambers corresponding to the X, Y and Z axes in which a set of components, one of which is illustrated in FIG. 4, are inserted. Caps 110, 112 and 114 fit over these hollow chambers with a portion of the passageways 104, 106 and 108 formed in each of the respective caps 110, 112 and 114. Three identical small ears, only one of which can be seen, ear 116, are strategically located on the housing 56. The ears 106 have a small opening, not separately identified or numbered, located therein allowing for attachment of a small rubber band, collectively identified by the numeral 118, thereto.

Each of the scales 58, 60, 62, 64, 66 and 68, have a head, collectively identified by the numeral 120 which includes a small slot 122 located thereon. The rubber bands 118 fit into the slots 122 and thus bias the respective scales toward the ears 116. Thus, in FIG. 2, for the rubber band 118 which is seen attached to the ear 116, the scale 66 is biased such that its head 120 is urged to move toward the projection 116.

Each of the respective scales further includes a positioning member 124 having an O ring 126 located therein. The respective scales slide through the positioning member 124 with the O ring 126 chosen such that it is capable of gripping along the shaft of the respective scales of fixedly hold the positioning member 124 at any position on the respective scales. The positioning member 124 can be slid along the length of the scale to which it is attached by the practitioner during initial alignment of the housing 54 or 56 with its respective engagement members 70 or 74 as hereinafter explained.

The housing 56 has an attachment projection 108 integrally molded thereon which attaches to the end 52 of the mandible side arm 32. The housing 56 further includes an elongated ear 130 which serves as a cable attachment point for connecting electrical lead lines to the housing 56.

A set of components as illustrated in FIG. 4 fit underneath each of the caps 110, 112 and 114 as previously noted. The Y axis set of the components is partly exploded out of the housing 56 in FIG. 3 and fully extended in FIG. 4. These components include a U shaped member 132, a distorted H shaped member 134 having a web 136 in its center, a small printed circuit board 138, two light emitting diodes 140 and 142, two light sensitive transistors 144 and 146 and a fixed scale or reference scale 148.

The member 132 has four recessed areas 150, 152, 154 and 156, which are sized and shaped so as to accept the components 140, 142, 144 and 146, respectively. The member 132 further includes a central channel 158. The web 136 fits into a portion of the channel 158 with the remainder of the channel 158 then forming a portion of the respective passageways 104, 106 or 108 depending upon which axis is involved.

The reference scale 148 fits into the channel 158, positioned against one of the side walls and locked in postion by having a portion of the reference scale 148 fitting into a small extension 160 of the channel 158. The appropriate diodes or transistors 140, 142, 144 or 146 are placed into the recessed areas 150, 152, 154 and 156 respectively and the reference scale 148 is placed within the channel 158 and the extension 160. The member 134 is then slid across the totality of these items to lock the diodes and transistors 140, 142, 144 and 146 in place in the member 132.

The member 134 has a plurality of holes 162 located in its cross bar which allow for extension of the electrodes collectively identified by the numeral 164 of the diodes and transistors 140, 142, 144 and 146 to project therethrough. The electrodes 164 are then appropriately soldered to the printed circuit board 138.

An optical passageway 164 is formed in the member 132 and extends between the light emitting diode 140 and the passageway 158. A similar passageway 166 which is aligned with the passageway 164 extends from the channel 158 to the light sensitive transistors 144. This allows light emitted from the light emitting diode 140 to pass through the central channel 158 and strike the light sensitive transistor 144 if nothing impedes its progress through the central channel 158 as hereinafter explained. Likewise, a passageway 168 extends from the diode 142 to the channel 158 with a corresponding aligned passageway 170 leading from the channel 158 to the transistor 146. When the member 134 is mated to the member 132, the web 136 holds the reference scale 148 in its position within the channel 158 and reduces the cross sectional area of the channel 158 such that it is just slightly larger than the cross sectional size of any of the scales 58, 60, 62, 64, 66 or 68. The remainder of the channel 158 thus left within the interior of the member 132 serves as a potion of one of the axis passageways 104, 106 or 108.

The totality of the structures shown in FIG. 4 are held in place within the housing 56 by the caps 110, 112 and 114 which are fixed with glue or the like to the housing 56 after appropriately locating components of FIG. 4 therein. In a similar manner, three identical components as seen in FIG. 4 would be located in the housing 54 for the right side of the pantographic apparatus.

An electrical cable, such as cable 172 seen in FIG. 1, is fixed to the elongated ear 130 with five individual fine electrical leads then leading to the printed circuit board 138. The light emitting diodes 140 and 142 are then connected in series utilizing two of these leads as is shown in the representational schematic of FIG. 9 with the light sensitive transistors 144 and 146 connected to a third lead serving as a common ground for both of them with the fourth and fifth leads then serving as individual output leads for the respective transistors 144 and 146. Again, this is shown in the representation schematic in FIG. 9.

The reference scale 148 includes two sets of reference marks 174 and 176 located thereon. The individual members of the set of reference marks 174 and 176 are spaced apart by the same distance with respect to one another within the sets 174 amd 176. However, the set of reference marks 176 is offset with respect to the set of reference marks 174 by one half of the width of one of the individual marks.

Each of the scales 58, 60, 62, 64, 66 and 68 also contain reference marks. As a representation of these, in FIG. 5 the scale 66 is shown. The reference marks 178 on this scale are continuously spaced at an even distance along the totality of the scale. Each of the individual reference marks of the sets 174, 176 or 178 are formed as dark, black marks on a light transparent surface, be it the reference scale 148 or any one of the scales such as the scale 66. This allows for light transmitting areas, not separately numbered to be located between any two adjacent reference marks in any of the sets 174, 176 or 178.

The two passageways 164 and 166 in combination form a pathway from the light emitting diode 140 to the light sensitive transistor 144 with this light pathway passing through both the movable scale 66 and the fixed scale on the reference scale 148 which are positioned within the central channel 158 dividing the two channels 164 and 166. Light can only be propagated from the diode 140 to the light sensitive transistor 144 by passing through this optical pathway which includes passage through both of the scales 148 and 66. Likewise, light from the light emitting diode 142 is led to the light sensitive transistor 146 in a like manner. The light from the diode 140 however, passes through the reference marks 174 on photoplast 148 and reference marks 178 on scale 66 before striking the light sensitive transistor 144, whereas the light from the light emitting diode 142 passes through the reference marks 176 on reference scale 148 and reference marks 178 on scale 66 before striking the light sensitive transistor 146.

In FIG. 6, a view down the channels 164 and 168 toward the light sensitive transistors 144 and 146 is shown. In the bottom portion of FIG. 6 the reference marks 178 on the scale 66 are essentially aligned with the reference marks 176 on the reference scale 148, whereas the reference marks 178 on the scale 66 are essentially out of alignment by one half of a reference mark with respect to the reference marks 174 on the reference scale 148 because, as noted above, reference marks 174 are offset with respect to reference marks 176. As such, for the instance depicted in FIG. 6, light passage through the channels 164 and 166 toward the light sensitive transistor 144 is inhibited and scattered to a greater extent by the combination of the reference marks 178 plus 174 than is the light passing through the channels 168 and 170 toward the light sensitive transistor 146 by the combination of reference marks 176 and 178.

As the scale 66 is moved with respect to the housing 56, the reference marks 178 on the scale 66 in conjunction with the reference marks 174 and 176 and the spaces between these reference marks, serves as a shutter to increase or decrease the amount of light being propagated toward the light sensitive transistors 144 and 146. Upon receipt of the light by the transistors 144 and 146 which is being shuttered by movement of the scale 66, the transistors 144 and 146 produce an electrical output which is sinusoidal in nature. Since the reference marks 174 are offset with respect to the reference marks 176, however, by one half a width of one of a reference marks, the sinusoidal output of the transistor 144 is out of phase with respect to the sinusoidal output of the transistor 146 by 90 degrees. This is depicted in FIG. 9B between the upper sine wave and the lower sine wave. By following the phantom lines crossing both the upper and lower sine waves, it is evident that there is a phase shift of 90 degrees.

The above sinusoidal analog outputs of the light sensitive transistors 144 and 146 are digitized as follows utilizing voltage comparative circuits. Lead 180 from transistor 144 serves as an input for voltage comparator 182. A reference voltage is fed to the voltage comparator 182 via reference input 184 connecting to adjustable pot 186. A typical twenty turn high resistance potentiometer can serve as the adjustable pot 186 with an LM339 voltage comparator serving as the voltage comparator 182.

The pot is adjusted so that the sine wave input to the voltage comparator 182 is output at 188 as a symmetrical square wave seen in the right hand side of FIG. 9B as the uppermost square wave. The square wave is either on or off depending upon whether or not the sinusoidal voltage input to the voltage comparator 182 is above or below the threshold value corresponding to the reference voltage input at 184. This is set such that the square wave is symmetrical by adjusting the reference voltage to equal one half of the amplitude of the sinusoidal wave.

In a like manner, transistor 146 is input at 190 to voltage comparator 192 having reference input 194 leading from pot 196, to yield an output at 198 which is also a symmetrical square wave, shown as the bottommost square wave in FIG. 9B.

Insofar as the sinusoidal inputs to voltage comparators 182 and 192 are 90 degrees out of phase as seen in the left hand side of FIG. 9B, the square waves output from the voltage comparators 182 and 192 are also 90 degrees out of phase as seen in the right hand side of FIG. 9B. The square waves output from the voltage comparators 182 and 192 are either in an "on", or 1, logic state, or an "off", or 0, logic state.

The square wave output from the voltage comparators 182 and 192 are fed to microprocessor 198 which could be any one of a variety of microprocessors such as an F8 Mostek microprocessor. In FIG. 9c, the on or off states of the square waves of 9b are shown at line 200 for the states output from voltage comparator 182 and line 202 for the states output from voltage comparator 192. The microprocessor 198 is such that it recognizes a change of state between the output of the voltage comparator 182 compared to the output of the voltage from comparator 192 to sense an increment of movement of one of the scales 58, 60, 62, 64, 66 or 68, and further, depending upon the pattern of change of state, senses the direction of movement of the appropriate scale. It is noted in FIG. 9c in reading line 200 over line 202 that a particular pattern of logic states exists in moving from right to left with a different pattern of logic states existing in moving from left to right. This allows the microprocessor 198 to recognize whether or not the appropriate scale which is being read is moving in one direction with respect to its housing 54 or 56 or in the other direction with respect to that same housing.

Typically, the reference marks 174, 176 and 178 are spaced apart one from another such that a change of state between the output of the voltage comparator 182 compared to the output of the voltage comparator 192 represents movement of the corresponding scale by one tenth of a millimeter. Because the reference marks 174 are offset one half of a mark with respect to the reference marks 176, as is seen schematically in FIG. 9a by comparing them to the reference marks 178, a twofold increase in resolution is achieved utilizing the two sets of reference marks 174 and 176 compared to that achievable using just a single reference mark in conjunction with a single light beam. Further, the use of the offset reference marks 174 and 176 in conjunction with two light beams being read simultaneously in response to movement of any one scale allows for detection of directional movement of that scale in an easy and convenient manner.

Referring now again to FIG. 8, the left engagement member 74 is shown with the scales 64, 66 and 68 shown in solid line positioned against it. The outline of the housing 56 is shown in phantom for clarity of location of the scales 64, 66 and 68 with respect to the member 74. For the pantographic device 20 shown, the engagement member 74 would be held fixed since it is attached to the maxilla side arm 32 and the housing 56 would be movable with respect to the engagement member 74 as the mandible side arm 28 moves with respect to the mandible side arm 32.

The rubber bands 18 bias the respective scales 64, 66 and 68 such that their ends 204, 206 and 208, respectively, opposite the ends wherein the scale heads 120 are located, contact the plates 78, 80 and 82, respectively. Those ends 204, 206 and 298 can slide along the surfaces of the plates 78, 80 and 82 as the housing 56 moves with respect to the engagement member 74. During excrusive movements, the rubber bands 118 always keep the ends 204, 206 or 208 in contact with the engagement member 74 and thus, as the housing 56 moves to response to mandibulary movement, the housing 56 moves and the scales 64, 66 and 68 move with respect to one another and the reference marks 178 on these scales then move across the reference marks 174 and 176 positioned in the light paths of the respective diode/transistor combinations described above.

Axial movement between scale 64 and housing 56 is allowed along the X axis as the scale 64 slides in passageway 106 (or, viewed differently, as passageway 106 slides along the scale 64). Transverse movement about the Y and Z axes of the scale 64 with respect to the passageway 106 in housing 56, however, is prevented because of the close fit of the scale 64 in passageway 106. Similarly, Y and Z axis axial movement is allowed between the scales 66 and 68, respectively, and housing 56 with transverse movement about Y and Z, and X and Y axes, respectively, prevented.

Movement of the housing 56 axially along the X axis with no corresponding Y or Z movement moves the housing 56 axially along the scale 64 but does not move it with respect to the scales 66 amd 68. Instead, the ends 206 and 208 of the scales 66 and 68 slide along the respective plates 80 and 82. Likewise, movement of the housing 56 along either the Y or the Z axis moves the housing 56 with respect to either the scale 66 or the scale 68.

If the housing 56 rotates about the axis of, for instance, the Y scale 66, this slides the ends 204 and 208 of the respective scales 64 and 68 along the plates 78 and 82 allowing both the scales 64 and 68 to move with respect to the housing 56 to indicate rotational movement about the Y axis. In a like manner, a complex movement which moves the housing 56 in the X, Y and Z directions simultaneously will be read simultaneously by movement of all of the scales 64, 66 or 68 with respect to the housing 56.

To facilitate alignment of the housing 56 with respect to the engagement member 74 at the start of measurement of the mandibular movement, the scales 64, 66 and 68 are slid in the housing 56 against the bias of the rubber bands 118 to disengage the ends 204, 206 and 208 from the plates 78, 80 and 82, respectively. The scales 64, 66 and 68 are then fixed in this position by sliding the positioning member 124 along the scales. The practitioner can now align the housing 58 with respect to the engagement member 74 by movement about clamp 46 to position the axial axis of the scale 68 with respect to the reference marks 102 and the axial axis of the scale 64 with respect to a reference circle 210 printed on the plate 78. The positioning members 124 are systematically withdrawn back toward the heads of the scales 120 as this alignment is done, stepwise allowing the respective scales 68, 64 and then 66 to engage the plates 82, 78 and 80. The pantographic device 20 is now ready for measurement of the mandibulary movement.

If, in executing the different movements which are being measured, the practitioner moves the patient's jaw too far, and then moves the jaw back in the opposite direction to an intermediate position, the particular scales which are involved in this movement move first in one direction with respect to their photo sensors and then back in the other direction. Insofar as the voltage comparators 182 and 192 sense direction of movement of the scales, the movement past a particular point and then back again to that point is automatically compensated for by the above noted direction detection indicated by the comparison of the change of state between the outputs of the voltage comparators 182 and 192.

If, for instance, the practitioner moved the patient's jaw such that the housing 56 moved five millimeters with respect to the scale 64, but in fact this was two millimeters too much, and then the practitioner moved the patient's jaw such that the housing 56 moved back two millimeters along the scale 64, the direction reading ability of the device 20 would sense this two directional movement and correctly read out the final position of three millimeters. This is in comparison to other devices not having this directional reading ability which would first record the five millimeter movement and then upon the subsequent two millimeter movement, add this to the five to give an erroneous readout of seven millimeters.

For the purposes of illustration herein, the engagement members 70 and 74 have been attached to the maxilla side arms 26 and 30 with the housings 54 and 56 attaching to the mandible side arms 28 amd 32. It is apparent that, instead of this physical setup, the engagement members 70 and 74 could be attached to the mandible side arms 28 and 32 and movable with respect to mandibulary movement with the housings 54 and 56 attached to the maxilla side arms 26 and 30 and fixed with respect to mandibulary movement. In this instances, the housings 54 and 56 would be stationary with respect to mandibulary movement, but the individual scales 58, 60, 62, 64, 66 and 68 would move in direct response to appropriate mandibulary movement. It is considered preferred, however, to attach the engagement members 70 and 74 to the fixed maxilla side arms 28 and 30 to facilitate alignment of the housings 54 and 56 and the engagement members 70 and 74 with respect to the temporomandibular joints.