Abstract:
A cover for a working cast makes it extremely easy to mount and dismount a working cast to and from an articulator, improves workability, and keeps the working cast as pollution-free as possible. An articulator is also proposed. The articulator has a base and a support member each carrying a rotatable and pivotable retainer plate. Each retainer plate can be fixed in position by turning a knob. Each retainer plate has a magnet plate on its outer surface. On the other hand, a base portion of a master model having a tooth portion is kept covered with the cover when molded. The cover has on its bottom surface a magnet plate. By magnetic attraction between the magnet plates of the cover and one of the retainer, the master model can be mounted on the articulator. On the other hand, a tooth portion of an antagonist model is fixed to a base member. The antagonist model is mounted on the articulator by magnetic attraction between a magnet plate provided on the bottom of the base plate and the magnet plate on one of the retainer plates.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a working cast which can be easily attached to and detached from an articulator, a cover for a working cast which also serves as a mold, and an articulator to which the working cast can be mounted. 
     To manufacture a crown restoration, a working cast is manufactured first. Then a master model and an antagonist model are mounted on an articulator to adjust the occlusion between the master model and the antagonist model. 
     As shown schematically in FIG. 20, such an articulator comprises a base  1  having a column  1   a , and a support arm  3  pivotally mounted to the top of the column  1   a  by a pin  2 . To mount a working cast, as shown in FIG. 21, plaster paste S 1  is heaped on the base  1 , and plaster paste S 2  is also heaped on the top of a master model M 1  whose bite with respect to an antagonist model M 2  has been fixed by wax beforehand, and further a small amount of plaster paste S 3  is optionally applied to the bottom of the support arm  3 . Then, the models M 1  and M 2  are placed together on the paste S 1 , the support arm  3  is pivoted onto the master model M 1 , and positions of the models M 1 , M 2  are adjusted in this state. Any excess plaster paste protruding from the outer periphery is removed by fingers or a knife. 
     It is thus extremely troublesome to mount a working cast on an articulator. It is also very time-consuming and low in efficiency to remove the model after the plaster has hardened. It is also necessary to remove plaster stuck on the bottom of the model. 
     An environment where crown restorations are manufactured is usually scattered with dust including plaster powder, metallic and ceramic powder and wax chips and thus extremely messy. Such dust tends to adhere to the models, thus necessitating cleaning of the models. 
     An object of this invention is to simplify the attaching and detaching of a working cast to and from an articulator, thereby markedly improving work efficiency. 
     Another object of this invention is to keep working casts as dust-free as possible. 
     SUMMARY OF THE INVENTION 
     According to this invention, there is provided a cover for a working cast which also serves as a mold, the cover comprising an outer surface protective member having a substantially semioval bottom wall, an end wall and a peripheral wall, a gripper having a pair of gripper plates and having an open end, and an engaging means for engagement with an articulator, the gripper being detachably mounted in the outer surface protective member such that the open end faces toward a tip of the outer surface protective member. 
     The engaging means may be a magnetic member. Also, the outer surface protective member should be formed with a through hole so that the gripper can be pushed out of the protective member by pushing through the hole. The gripper should have a partitioning plate extending to the tip of the outer surface protective member to form a cover for a one-side jaw model. 
     A positioning means should preferebly be provided on the bottom wall of the outer surface protective member for positioning of the cover on the articulator. 
     For an antagonist model, a base member having an engaging means and a positioning means is provided. The master model with the cover and the antagonist model with the base member are mounted on the articulator which has retaining plates for retaining the cover and the base member. The retaining plates each have a magnetic member which attracts a magnetic member of the cover and the base member. The retaining plates also have positioning means for positioning the cover and the base member with respect to the articulator. 
     Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a full jaw cover according to this invention; 
     FIG. 2 is a plan view of an outer surface protective member of the cover; 
     FIG. 3 is a vertical sectional view of the cover; 
     FIG. 4 is a plan view of the cover; 
     FIG. 5 is a bottom view of the cover; 
     FIG. 6A is a plan view of a cover for an anterior tooth portion; 
     FIG. 6B is a vertical sectional view of the same; 
     FIG. 7A is a plan view of another cover for an anterior tooth portion; 
     FIG. 7B is a vertical sectional view of the same; 
     FIG. 8A is a plan view of a cover for one-side jaw model; 
     FIG. 8B is a vertical sectional view of the same; 
     FIG. 9 is a vertical sectional view of an article molded using a cover for a; 
     FIG. 10 is a plan view of the same; 
     FIG. 11 is a vertical sectional view showing how the model is taken out of the cover; 
     FIG. 12 is a partially cutaway side view of an articulator; 
     FIG. 13 is a plan view of a retainer plate of the articulator; 
     FIG. 14 is a side view of a base member of an antagonist model; 
     FIG. 15 is a back view of the same; 
     FIG. 16 is a partial enlarged vertical sectional view of a different base member; 
     FIG. 17 is a side view of the cover in use; 
     FIG. 18 is a side view showing the model mounted on the articulator together with the cover; 
     FIG. 19 is a partial enlarged vertical sectional view of a different articulator; 
     FIG. 20 is a side view of a conventional articulator; and 
     FIG. 21 is a side view showing how it is used. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of this invention is now described with reference to FIGS. 1-19. FIGS. 1 through 5 show a cover for protecting a base of a full jaw model. This cover also serves as a mold. As shown in FIGS. 1 and 2, a cover  100  for a full jaw model has an outer surface protective member  110 , and a gripper  120  for gripping the bottom of the base. The outer surface protective member  110  comprises a bottom wall  111  having a substantially semioval shape, and a peripheral wall  112  and an end wall  113  provided along the edge of the bottom wall  111  so as to completely surround the wall  111 . The peripheral wall  112  and the end wall  113  are of a substantially uniform height over the entire circumference, but are preferably tapered slightly outwardly. Formed in the middle of the end wall  113  is a vertical recess  113   a  for receiving an end plate of the gripper  120 . Contiguous with the recess  113   a,  the bottom wall  111  is formed with a tapered recess  111   a  with a round tip and a through hole  114  near the tip (FIG.  2 ). 
     As shown in FIGS. 1 and 3, the gripper  120  comprises a lower gripper plate  121  complementary in shape and height to the recess  111   a  of the bottom plate  111  of the protective member  110 , a tongue-shaped upper gripper plate  122 , and an end plate  123  connecting the upper and lower plates  121 ,  122  together. The lower gripper plate  121  carries on its bottom a magnet plate  124  adapted to fit in the through hole  114 . As seen in FIGS. 3 and 4, the gripper  120  can fit snugly in the recesses  111   a  and  113   a  of the outer surface protective member  110  so that the tops of the bottom wall  111  and the lower gripper plate  121  are flush with each other. 
     Referring to FIGS. 3 and 5, ribs  115  having a triangular section are formed on the back of the outer surface protective member  110  along centerlines crossing each other at an angle of 90°. The functions of the ribs are described below. The upper gripper plate  122  is recessed like a tray so that it fits in the base of the full jaw model. 
     FIGS. 6A-7B show a mold/cover used for the manufacture of an anterior tooth model. Structurally, FIGS. 6A-7B are the same as the cover  100  for full jaw model except the range of its anterior tooth portion. In the figures, a mold/cover  200  has an outer surface protective member  210 , a bottom wall  211 , a semioval recess  211   a,  a peripheral wall  212 , an end wall  213 , a vertical recess a through hole  214 , ribs  215 , a gripper  220 , a lower gripper plate  221 , an upper gripper plate  222 , an end plate  223 , and a magnet plate  224 . 
     FIGS. 8A and 8B show a mold/cover  300  for use in the manufacture of a one-side jaw model. As shown, the cover  300  comprises an outer surface protective member  310  and a gripper  320 . The former comprises a substantially semioval bottom wall  311 , and a peripheral wall  312  and an end plate  313  surrounding the bottom wall  311 , and is shaped like a container. The end plate  313  has a vertical recess  313   a.  Contiguous with the recess  313   a,  the bottom wall  311  is formed with a tapered recess  311   a  having its tip extending to a vertical recess  312   a  formed in the inner surface of the peripheral wall  312  at its tip. 
     The gripper  320  comprises a lower gripper plate  321  adapted to fit in the tapered recess  311   a,  and a tongue-shaped upper gripper plate  322 . The gripper plates  321  and  322  are connected together by an end plate  323  and a partitioning plate  325 . The plate  325  extends along the center line of the gripper plates  321 ,  322 , and has at its tip an engaging piece  326  received in the vertical recess  312   a  of the peripheral wall  312 . The protective member  310  further has a through hole  314  formed in the bottom wall  311  and ribs  315  provided on the bottom of the bottom wall  311 . A magnet plate  324  is secured to the bottom of the lower gripper plate  321 . 
     Description is now made of how a working cast is manufactured using the cover  100 . As shown in FIGS. 9 and 10, a release agent is applied to the inner surface of the cover  100  in the state of FIG. 3, and plaster paste S 4  is poured into the cover  100 . A tooth portion T 1  formed beforehand is then pressed so that its bottom becomes flush with the edge of the cover  100 . Of course, dowel pins provided in the tooth portion T 1  beforehand are buried completely in the plaster paste S 4  in the cover  100 . Any excess paste S 4  is removed by a finger or a knife and the paste is allowed to harden. 
     When the paste hardens, the assembly is handled without removing the cover  100 . But if desired, the molded base portion B is removable from the outer surface protective member  110  together with the gripper  120  by pushing the magnet plate  124  upward as shown in FIG.  11 . The gripper  120  is also removable by pulling it rightwardly in FIG. 11 as shown by an arrow. 
     The cover  200  for an anterior tooth model and the cover  300  for a one-side jaw model are also used in the same manner, except that in the case of the cover  300 , plaster paste is poured into only one of two spaces defined on opposing sides of the partitioning plate  325 . 
     An articulator on which the thus molded working cast is to be mounted is now described with reference to FIGS. 12 and 13. As shown in FIG. 12, a support column  1 a extends substantially perpendicularly from one end of a base  1 . A support arm  3  is pivotally mounted to the top end of the support column  1   a  by a pin  2 . The support arm  3  has an integral stop piece  4  extending in the opposite direction to the arm  3 . A support piece  5  extends from the top end of the support column  1   a  in the same direction in which the stop piece  4  extends. A threaded pin  6  is threaded into the support piece  5  with its tip in abutment with the stop piece  4 , thus limiting the pivoting motion of the support arm  3 . Thus, by turning the threaded pin  6 , it is possible to pivot the support arm  3  toward and away from the base  1 . The threaded pin  6  is held in position by a nut  7  threaded onto the pin  6 . 
     Retainer plates  10  are mounted to the bottom of a support member  8  provided at the tip of the support arm  3  and to the top surface of the base  1 . As shown in FIGS. 12 and 13, the retainer plates  10  are semioval members having a flat top and a flat bottom respectively formed with a recess  11  in the center. A magnet plate  12  is secured in each recess  11 . Each retainer plate  10  has four retaining grooves  13  having a triangular section and extending radially from the recess  11  and spaced at equal angular intervals of 90°. The grooves  13  extend to the edges of the retainer plates  10 . They are complementary in shape and position to the ribs  115 ,  215  and  315  formed on the bottoms of the covers  100 ,  200  and  300 . 
     Each retainer plate  10  carries on its back a stem  14  extending from the center of the plate  10  and having a ball  15  at the tip. The ball  15  is received loosely in a socket  16  formed in the base  1  and the support member  8  so as not to come out of the socket. The retainer plates  10  are thus rotatable and pivotable relative to the base  1  and the support member  8 . Each socket  16  is a threaded hole into which is threaded a bolt  17 . The bolt  17  has at its tip a spherical recess  18 . By turning the bolt head  19  in one direction, the ball  15  is pushed by the bolt  17  and pressed against the edge of the bottlenecked opening of the socket  16  to keep the ball unmovable. In this state, the support plate  10  can neither rotate nor pivot, but is fixed in position. By turning the bolt head  19  in the opposite direction, the ball  15  can be moved away from the socket edge, so that the plate  10  is now rotatable and pivotable. 
     A base member  20  for mounting an antagonist model on the articulator is now described. As shown in FIGS. 14 and 15, the base member  20  is a substantially semioval, flat plate having a recess  21  in the center of the back. A magnet plate  22  is secured in the recess  21 . Four ribs  23  extend radially from the recess  21 , spaced at angular intervals of 90°. These ribs  23  are complementary in shape and position to the retaining grooves  13  of the retainer plates  10  of the articulator. 
     To the surface of the base member  20 , a tooth portion of an antagonist model is secured by means of an adhesive in general and an instantaneous adhesive in particular, or by applying an adhesive beforehand. 
     As shown in FIG. 16, a plurality of adhesive layers  24  and release paper sheets  25  may be alternately laminated. By peeling the outermost release paper sheet before bonding each antagonist model, this laminate can be used a plurality of times. Numeral  26  designates tabs of the release paper sheets  25 . 
     The master model and the antagonist model may be mounted on the articulator e.g. in the following manner. Of course, the order of mounting steps is not limited to that shown. First, as shown in FIG. 17 the, bite of the tooth portion T 2  of the antagonist model with respect to the master model formed in FIG. 9 with the cover  100  on the master model is fixed with wax. The base member  20  of FIGS. 14,  15  is fixed to the underside of the tooth portion T 2 . Then, as shown in FIG. 18, the magnet plate  124  provided on the back of the cover  100  is attracted to the magnet plate  12  provided on the retainer plate  10  of the articulator. 
     At this time, the retainer plate  10  and the cover  100  are positioned relative to each other by the engagement of the ribs  15  of the cover  100  in the grooves  13  of the retainer plate  10 . The upper and lower retainer plates  10  are not fixed but kept rotatable and pivotable. In this state, the magnet plate  12  of the retainer plate  10  on the base  1  is attracted to the magnet plate  22  provided on the base member  20  of the antagonist model with the ribs  23  engaged in the retaining grooves  13 . The base member  20  is thus fixed in position relative to the retainer plate  10 . The models are then moved (this is possible because the upper and lower retainer plates  10  are still rotatable and pivotable) so that the tooth portions T 1  and T 2  of the master model and the antagonist model are substantially parallel to the base  1  and the support member  8 , respectively. They are then fixed in position by turning the upper and lower bolt heads  19 . 
     The base member  20  may be firstly fixed to the retainer plate  10  on the base  1  without fixing the base member  20  to the tooth portion T 2  of the antagonist model beforehand. Also, adjustment may be made after the master model and the antagonist model have been mounted on the upper and lower retainer plates  10  without fixing the bite between the master model and the antagonist model beforehand. 
     The anterior tooth model with the cover  200  and the one-side jaw model with the cover  300  are also mounted in the same manner. The order of mounting steps is not limited. 
     FIG. 19 shows an embodiment in which the socket for rotatably and pivotably retaining the stem  14  of each retainer plate  10  is vertically movable. A socket member  16   a  is threaded into a threaded hole  8   a  formed in the support member  8  (or a base  1 ) so as to be vertically movable. The socket member  16  is fixed in position by a nut  16   b.    
     In the above embodiment, as means for detachably mounting the cover  100  and the base member on the articulator, magnet plates are attracted to each other. Of course, one of the magnets may be replaced with a ferromagnetic member. Further, the mounting means may be a press-fit member such as a snap button or an adhesive. Such means may be provided on either of the gripper and the outer surface protective member. As positioning means, ribs and grooves are used in the embodiment, but any other combination of male and female elements may be used. 
     According to this invention, as described above, it is possible to mold a base portion of a working cast using a cover having also the function as a mold and to handle the working cast without removing the cover. Thus, it is possible to form a working cast and also protect it using a single cover. The working cast can thus be kept clean and undamaged. Since there is no need to use plaster to mount the working cast on the articulator, to remove plaster thereafter, and to clean the articulator and the model, workability improves dramatically, and the amount of plaster needed decreases, which leads to a cost reduction. Work environments also improve because no plaster powder flies up in the air during cleaning. 
     Also, dowel pins of the tooth portion of the working cast will not be pushed up by plaster when the working cast is mounted on the articulator.