Abstract:
A model and die system has a working quadrant of parallelepiped construction and a opposing quadrant of the same construction. The working quadrant has an upper flat surface disposed in confronting relation to a lower flat surface of the opposing quadrant. Pin-receiving bores are formed in the working quadrant and mounting members depend from the opposing quadrant. Each cast tooth supported by the working quadrant has a pin depending from it and is fully seatable against the upper flat surface. Each cast tooth mounted on the upper flat surface is secured to a mounting post that depends from the upper flat surface. In a first embodiment, the quadrants are held in spaced apart, adjustable vertical relation to one another by a pair of parallel guideposts. In a second embodiment, an articulated hinge performs that function. In a third embodiment, a semicircular base opposes a semicircular top member.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   This invention relates, generally, to dentistry. More particularly, it relates to a model and die system for making casts of dental impressions for the shaping of crowns and dentures. 
   2. Description of the Prior Art 
   The use of triple trays is now the most common technique for taking impressions. Also known as dual-arch trays, they capture the area to be restored, the opposing area, and the bite relationship. Errors can arise, however, when a bite registration is transferred from a triple tray impression to an articulation hinge such as a VertexÂ®, OrbizÂ®, QuickulatorÂ®), or to a generic metal articulation hinge. 
   The current method for transferring a bite registration from a triple tray to an articulation hinge includes the initial step of mixing dental stone powder to make a batch of liquid dental stone and pouring the liquid dental stone into the impression on the prep side first. The stone is allowed to cure for about thirty (30) minutes. Another batch of liquid stone is then poured into the opposing side of the impression and allowed to cure for about thirty (30) minutes at which time the model of the teeth is removed. 
   The model with the prepared teeth is then ground on a model trimmer. The bottom of the model must be completely flat all the way across. A router or a hand piece and burr are then used to bevel the model edges. The model is then dried and cleaned. 
   Holes are then drilled in the bottom of the model in registration with the preps and other sections of the working model. The model is then cleaned again. 
   Next, dowel pins are glued into the holes. Typically, there are two dowel pins for each section. The glue is allowed to set and dry. A separating agent is then sprayed onto the bottom of the model. After the separating agent has dried at least slightly, a batch of working quadrant stone is then prepared and poured into a working quadrant former. Model pins are then inserted into the working quadrant former. The working quadrant stone is allowed to set in accordance with the manufacturer&#39;s suggested time, which is usually around thirty (30) minutes. The model teeth are then removed from the working quadrant with the pins exposed. The bottom of the working quadrant is ground to expose the die pinholes. The holes are then cleaned of debris and the model is cut into sections using a hand piece and disc or a die saw. The dowel pins are then cleaned because the separating medium leaves a film on the dowel pins that can hinder the die section and other sections of the model from seating down all the way in the working quadrant. The crown or denture being prepared will not fit the patient if the sections and dies do not seat all the way flat into the working quadrant stone. 
   The opposing arch is then removed from the impression. It is trimmed on a model trimmer and placed in a working quadrant former. A batch of stone is mixed and poured into the working quadrant former to hold the opposing arch. After the stone has set for about thirty (30) minutes, the technician then articulates both arches. 
   Articulation is currently performed by hand and eye to try and “guess” where the correct centric bite is located. A hinge is then glued into place to maintain the bite that has been deemed to be the correct bite. This completes the working model and the case is ready to proceed with fabrication of the restoration. 
   This method is very labor-intensive and mistakes at any step can result in a substandard working model. For example, it is difficult to always achieve the optimal water and powder ratio to produce the working quadrant stone. Further steps that are difficult to optimize include the grinding of the model, the placement and gluing of the dowel pins, and the articulation of the models to produce proper occlusion in the mouth. Further difficulties include breaking the model during drilling or trimming of holes which necessitates re-starting the process from the beginning, and the optimization of many other variables not expressly mentioned herein but well-known to those who work in this field. 
   Several techniques have been developed in an effort to improve the above-described process. Some technicians, for example, have developed their own articulation hinges in an attempt to avoid use of the above-mentioned commercially available articulation hinges. Moreover, the model has been placed in the center of the tray but this technique has the disadvantage of making the prep hard to reach and hard to see. 
   Most of the known systems prevent the technician from determining whether or not the dies are completely seated. Moreover, in all of the known systems it is difficult to put in and take out the dies from the working quadrant. Most known systems do not provide good centric opposing quadrants for occlusion nor do they provide a free and centric opposing quadrant. Nor does any known system employ double dowel pins to stabilize dies. 
   What is needed, then, is a system that is much less labor intensive than the known systems. The needed system would reduce the amount of guesswork, artistry, and skill required under the known systems. It would therefore standardize the procedure and enable a technician to work with ease and accuracy. The resulting models would be superior to the models made under the current system. 
   More particularly, an optimal system would enable a technician to use any of the commercially-available articulation hinges. In an optimal system, the dies would always be placed in a labial position so that they would be easy to reach and see. An optimal system would provide a flat working quadrant with no obstructions so that it can be determined whether or not the dies are properly seated. Each die and model section should be double dowel-pinned and each die should have an exact, easy path of insertion. Movement should always be solid, never centric. The improved system should also provide a complete mesial or distal centric opposing quadrant. 
   U.S. Pat. No. 4,382,787 to Huffman discloses a dental model articulator for mounting and holding dental model casts necessary for the correction or alteration of teeth. The articulator includes two mirror-image brackets, connected together through a hinging mechanism, that are attached to a mounting means. Huffman further discloses a mechanism including a working quadrant with an opposing element for securing dental molds. This ensures that the bite between the lower and upper casts is optimal. Huffman does not include pin-receiving bores in a working quadrant nor does Huffman disclose elevated mounting members located in an opposing quadrant. 
   U.S. Pat. No. 6,471,513, also to Huffman, discloses a dental model working quadrant assembly having preformed apertures for securing or reconstructing a dental model. The supporting working quadrant includes apertures situated in two rows located between indexing studs. Two rows of apertures are contained in the support structure, with the external aperture row being offset from and adjacent to the internal aperture row. These apertures are designed to receive tapered pins. The working quadrant may be attached to an articulator either through an articulator plate or through the use of a latch and a slot located on the mounting working quadrant. 
   A mechanism with lower and upper support means that produces a more accurate recreation of restorative work is disclosed in U.S. Pat. No. 5,466,152 to Walter. The support means is connected at one end through the use of an anti-rotational guide located at a hinged end. A plurality of indexing holes are situated throughout the surface of the support member. The dental model is affixed to the support member through the attachment of indexing pins corresponding to predetermined indexing holes. A hinge and indexing pins stabilize the support working quadrant and opposing structure and thus produce a fairly accurate representation of a dental restoration model. There are no offset, preformed bores that enables the efficient trimming of excess casting material. 
   In view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the current systems could be improved. 
   SUMMARY OF INVENTION 
   The long-standing but heretofore unfulfilled need for improvements in die and model systems is now met by a new, useful, and nonobvious invention. 
   In a first embodiment of this invention, the novel model and die system includes a base, known in the industry as a working quadrant, of generally straight, parallelepiped construction having a flat upper surface. The system further includes a top member, known in the industry as an opposing quadrant, of generally straight, parallelepiped construction having a flat lower surface. The working quadrant and the opposing quadrant are disposed in vertically spaced apart registration with one another. The working quadrant and the opposing quadrant have a common predetermined longitudinal extent, a common predetermined transverse extent, and a common predetermined height. 
   In the first embodiment, a pair of upstanding guideposts is mounted to the working quadrant, there being one guidepost at each end of the working quadrant. A pair of guidepost-receiving throughbores is formed in opposite ends of the opposing quadrant. Each guidepost of the pair of guideposts is slideably received within an associated throughbore so that the space between the working quadrant and opposing quadrant is adjustable by sliding the opposing quadrant along the length of the upstanding guideposts. The guideposts also maintain the vertically spaced apart registration between the working quadrant and opposing quadrant as the opposing quadrant is displaced. 
   The working quadrant is solid beneath part of the flat upper surface. A first row of bores is formed in the working quadrant in closely spaced apart relation to a preselected longitudinally extending edge of the working quadrant. A second row of bores is formed in the working quadrant in parallel relation to the first row of apertures. The second row of bores is spaced further from said preselected longitudinally extending edge than is said first row of bores, i.e., said first row of bores is spaced between said second row of bores and said longitudinally extending edge. 
   The working quadrant is hollow beneath that part of the flat upper surface where no bores are formed. Each bore is adapted to receive a pin that depends from a cast tooth and gum segment. Thus, the solid part beneath the flat upper surface has a depth sufficient to receive a pin but said depth may be less than the height of the sidewalls of the working quadrant. 
   A thin metallic foil overlies the flat upper surface of the working quadrant so that dental stone does not flow from bores that are not in use, as will become more clear as this description proceeds. 
   Each cast tooth of a plurality of cast teeth supported by the working quadrant has a pair of pins depending from it. Moreover, a pair of cast teeth, or perhaps a group of three teeth, may be formed as a unit and each unit has a pair of pins depending therefrom. Each pin is snugly received within a preselected bore of the plurality of bores formed in the working quadrant. More specifically, each pair of pins includes a first pin that is received with a bore of the first row of bores and a second pin that is received within a bore of the second row of bores. A pin punctures the foil mentioned above when a cast tooth is mounted on the working quadrant in a manner disclosed hereinafter. 
   At least one cast tooth having a pair of pins depending therefrom and snugly received within associated bores of said first and second rows of bores formed in the working quadrant is positioned so that a leading surface of the at least one cast tooth is substantially flush with the preselected leading edge of the working quadrant. This minimizes trimming of excess materials. 
   The opposing quadrant is an essentially hollow structure, including a flat lower surface and sidewalls projecting upwardly from a periphery thereof. A plurality of apertures is formed in the flat lower surface. The plurality of apertures includes a plurality of sets of apertures where the sets of apertures are arranged in a longitudinally-extending row. More particularly, four apertures arranged in circumferentially spaced relation to one another collectively form one set of apertures. In a commercial embodiment of the invention, there are ten (10) sets of said apertures. 
   A mounting member in the form of a mounting post is associated with each set of apertures so that in said commercial embodiment there are ten (10) of said mounting posts. Each mounting post is centered with respect to its associated set of apertures, each mounting post is fluted, and each mounting post depends from the lower flat surface of the working quadrant. 
   Each mounting post has four semicircular flutes, each of which is in registration with an associated aperture and the depth of each flute is substantially equal to the radius of its associated aperture. In this way, no part of the mounting post occludes any of its four associated apertures. 
   The flutes extend from the flat lower surface to a point about two-thirds of the extent of each mounting post. Accordingly, about the lower third of each mounting post is not fluted, thereby forming a disc-shaped head at the bottom of each mounting post. Thus, there is an undercut formed in each post where a flute meets the head. 
   In the commercial embodiment where each set of apertures has four apertures and where each post has four flutes, the number of undercuts in each post is four. The number of apertures and hence the number of flutes and hence the number of undercuts may be increased or decreased. Four (4) is merely considered to be an optimal number but other numbers of apertures per set of apertures and hence other numbers of flutes and undercuts are within the scope of this invention. 
   This arrangement of sets of apertures where each set of apertures has a mounting post associated with it and where each mounting post is fluted as described and surmounted by an unfluted head to create a plurality of undercuts is provided to hold the cast teeth that depend from the lower flat surface of the opposing quadrant. The dental stone used to make the gums associated with the cast teeth fills the apertures and the flutes. The respective heads of the posts support the dental stone because the posts depend from said flat lower surface. 
   Thus, there are no pins associated with the cast teeth that depend from the opposing quadrant. It should be understood that if the opposing quadrant were provided with the pin-receiving bores of the working quadrant, any pins placed into said bores would fall out under the influence of gravity. The fluted posts that depend from the lower surface of the opposing quadrant are secured to the flat lower surface and cannot separate therefrom. Accordingly, when dental stone hardens in said flutes and undercuts, the cast gums and teeth associated with the opposing quadrant cannot fall under the influence of gravity after the dental stone has cured. 
   In the first embodiment, a bite between the at least one cast tooth mounted to the working quadrant and the at least one cast tooth mounted to the opposing quadrant is checked by sliding the opposing quadrant toward the working quadrant until the cast teeth abut one another. 
   In a second embodiment, the guideposts of the first embodiment are eliminated and the quadrants are interconnected to one another by a hinge. 
   In a third embodiment, the working quadrant has a semicircular configuration and therefore represents an entire set of lower teeth, not just a quadrant thereof. It is therefore referred to as the working base. Similarly, the opposing quadrant has a semicircular configuration and therefore represents an entire set of upper teeth, not just a quadrant thereof. It is therefore referred to as the opposing top member. However, in all other respects, the semicircular working base has the same structure as the straight working quadrant and the semicircular opposing top member has the same structure as the straight opposing quadrant. 
   An important object of this invention is to provide an improved model and die system that lowers the level of skill required to produce a good set of model teeth. 
   A closely related object is to provide an improved system that substantially reduces the time required to produce a good set of model teeth. 
   These and other important objects, advantages, and features of the invention will become clear as this description proceeds. 
   The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
       FIG. 1  is a diagrammatic view of the first embodiment; 
       FIG. 2A  is a top plan view of a working quadrant of said first embodiment; 
       FIG. 2B  is a bottom plan view of the working quadrant; 
       FIG. 2C  is a side elevational, partially cut-away view of the working quadrant depicting a cast tooth spaced apart therefrom; 
       FIG. 2D  is a side elevational, partially cut-away view of the working quadrant depicting the cast tooth of  FIG. 2C  in its engaged configuration; 
       FIG. 3  is a perspective view of a second embodiment; 
       FIG. 4  is a side elevational view of the second embodiment; 
       FIG. 5  is a view taken along line  5 — 5  in  FIG. 4 ; 
       FIG. 6  is a sectional view taken along line  6 — 6  in  FIG. 5 ; 
       FIG. 7  is a sectional, enlarged view taken along line  7 — 7  in  FIG. 6 ; 
       FIG. 8A  is a top plan view of a third embodiment; 
       FIG. 8B  is a side elevational view of the third embodiment; and 
       FIG. 8C  is a top plan view of said third embodiment when unfolded. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , it will there be seen that the reference numeral  10  denotes an illustrative embodiment of the present invention as a whole. 
   The first embodiment of novel system  10  includes a working base or quadrant  12  and an opposing top member or opposing quadrant  14  having essentially the same structure as working quadrant  12 . More particularly, working quadrant  12  and opposing quadrant  14  share a generally straight, parallelepiped configuration having a predetermined length, width, and height. 
   Working quadrant  12  has a flat upper surface  12   a  and opposing quadrant  14  has a flat lower surface  14   a . Flat upper surface  12   a  is disposed in confronting relation to lower flat surface  14   a.    
   In a first embodiment, a pair of upstanding guideposts, collectively denoted  16 , interconnects working quadrant  12  and opposing quadrant  14 . The respective lowermost ends of guideposts  16  are secured to working quadrant  12  by any suitable means, near opposite ends thereof. Two longitudinally spaced apart throughbores  18  are formed in opposing quadrant  14  to slidingly receive said posts so that opposing quadrant  14  may be easily moved toward or away from working quadrant  12  as indicated by double-headed directional arrow  20 . 
   Posts  16 ,  16  are snugly received within their respective bores  18 ,  18  so that friction maintains opposing quadrant  14  in any position of functional adjustment along the length of posts  16 ,  16 . Moving opposing quadrant  14  therefore requires the application of manual force to said opposing quadrant. 
   A first row of bores, where each bore is denoted  22 , is formed in working quadrant  12  in closely spaced apart relation to longitudinally-extending leading edge  13  of working quadrant  12 . A second row of bores, where each bore is denoted  23 , is formed in parallel relation to the first row of bores. The first row of bores is positioned between the second row of bores and said longitudinally-extending edge. 
     FIG. 1  further depicts a plurality of metal pins, collectively denoted  24   a ,  24   b  and a plurality of cast teeth and gums, collectively denoted  26 . Each bore  22  is adapted to snugly receive a metal pin  24   a  and each bore  23  is adapted to snugly receive a metal pin  24   b . The provision of two pins prevents each cast tooth and gum or set of cast teeth and gum from rotating. 
   Upper surface  12   a  of working quadrant  12  is perfectly flat. It is therefore easy to see if each cast tooth  26  is perfectly seated, i.e., with its pins  24   a ,  24   b  fully seated within its associated bores  22 ,  23 , respectively. 
   Working quadrant  12  is hollow except in the region below bores  22  and  23 . As indicated in the more realistic bottom plan view of  FIG. 2B , a solid material  27  is provided within which bores  22 ,  23  are formed. In a preferred embodiment, all parts of the working quadrant, including the material within which the bores are formed, are formed of a high impact plastic. The use of metallic or other materials is also within the scope of this invention. 
   As depicted in  FIG. 2A , apertures  22  are positioned in offset relation to longitudinally-extending edge  13  of working quadrant  12  as mentioned above so that the forward edge  26   a  of each cast tooth  26  is substantially flush with said longitudinally-extending edge. This minimizes the amount of trimming that must be performed. In the example of  FIG. 2A , the only areas of working quadrant  12  that needs to be trimmed of excess cast material on the labial side of teeth  26  are collectively denoted  28 . As further indicated in  FIG. 2A , most of working quadrant  12  is removed. The removed area in this particular example is denoted  30 . However, a relatively large area, denoted  32 , may be left in place because area  32  is hidden from view behind teeth  26  and therefore need not be removed. This saves time and also reduces abrasion to cast teeth  26 . 
   When the excess cast material has been removed, opposing quadrant  14  is simply lowered until cast teeth  26  carried thereby engage cast teeth  26  mounted on working quadrant  12 . If the bite is optimal, the upper and lower cast teeth are detached from opposing quadrant  14  and working quadrant  12 , respectively, and hinged together using any one of the above-listed commercially available hinge articulators. 
   A thin metallic film or foil  25 , depicted in the more realistic views of  FIGS. 2C ,  2 D, and  4 , overlies flat upper surface  12   a  and covers bores  22 ,  23 . The foil is punctured by pins  24   a ,  24   b  when the novel structure is used as perhaps best understood from  FIGS. 2C and 2D . Foil  25  prevents dental stone from entering the bores  22 ,  23  that are not used, i.e., the bores that do not receive pins  24   a ,  24   b  remain covered by said foil  25  and thus flat upper surface  12   a  remains flat. In the absence of foil  25 , some of the dental stone could enter into the unused bores and cause bumps or other uneven spots on surface  12   a , thus preventing teeth  26  from seating cleanly thereagainst. 
   There is no corresponding plurality of pin-receiving bores  22 ,  23  formed in opposing quadrant  14 . 
     FIGS. 3–8C  also provide a more realistic view of the novel two-piece model and die system. In those Figures, guideposts  16 ,  16  of the first embodiment are eliminated and working quadrant  12  is interconnected to opposing quadrant  14  by an articulation hinge  34  ( FIGS. 3 and 4 ) having a first part  34   a  connected to working quadrant  12  and a second part  34   b  connected to opposing quadrant  14  as best depicted in  FIG. 4 . This hinged embodiment is the second embodiment of the invention. 
   Adjustment rod  35  ( FIGS. 3 and 4 ) is slideably and snugly received within a throughbore formed in opposing quadrant  14 . Its flat lowermost end  35   a  abuts flat upper surface  12   a  of working quadrant  12  and thus serves as a stop means for hinge  34  when working quadrant  12  and opposing quadrant  14  are disposed in optimal juxtaposition with one another as depicted ion  FIG. 3 . 
   It should be understood that quadrants  12  and  14 , depicted diagrammatically in  FIGS. 1 and 2A  in connection with the guidepost embodiment of the invention, actually have the structure as depicted in  FIGS. 2B ,  2 C,  2 D, and  3 – 7 . Accordingly, the more detailed description of said quadrants as made hereinafter also applies to the quadrants of  FIGS. 1 and 2A . 
   As best understood in connection with  FIG. 3 , opposing quadrant  14  is an essentially hollow structure, including the aforesaid flat lower surface  14   a  and sidewalls  36  projecting upwardly from a periphery thereof. A plurality of sets of apertures is formed in flat lower surface  14   a  and the sets of apertures are arranged in a row as best depicted in  FIG. 5 . Each set of apertures is denoted  38  in said  FIG. 5 . An enlarged view of one set of apertures  38  is provided in  FIG. 7 . 
   More particularly, as best depicted in said  FIG. 7 , four apertures  38   a ,  38   b ,  38   c , and  38   d  arranged in circumferentially spaced relation to one another collectively form one set of apertures. In a commercial embodiment of the invention, there are ten (10) sets of said apertures. 
   A mounting post  40 , depicted in  FIGS. 4 and 6 , is associated with each set of apertures so that in said commercial embodiment there are ten (10) of said mounting posts. Each mounting post  40  is centered with respect to its associated set of apertures, each mounting post is fluted, and each mounting post depends from lower flat surface  14   a  of working quadrant  14  as best understood from  FIG. 4 . 
   More particularly, each mounting post  40  has four semicircular flutes, collectively denoted  42  in  FIG. 7 , each of which is in registration with an associated aperture and the depth of each flute is substantially equal to the radius of its associated aperture. In this way, no part of a mounting post  40  occludes any of its four associated apertures as clearly depicted in said  FIG. 7 . 
   Flutes  42  extend from flat lower surface  14   a  to a point about two-thirds of the extent of each mounting post. Accordingly, about the lower third of each mounting post is not fluted, thereby forming a disc-shaped head  44  at the bottom of each mounting post. Thus, there is an undercut  46  formed in each mounting post  40  where a flute  42  meets head  44 . 
   In the commercial embodiment where each set of apertures  38  has four apertures  38   a ,  38   b ,  38   c , and  38   d , and where each mounting post  40  has four flutes  42 , the number of undercuts  46  in each mounting post is four. The number of apertures and hence the number of flutes and hence the number of undercuts may be increased or decreased. Four (4) is merely considered to be an optimal number but other numbers of apertures per set of apertures and hence other numbers of flutes and undercuts are within the scope of this invention. 
   This arrangement of sets of apertures  38  where each set of apertures has a mounting post  40  associated with it and where each mounting post is fluted as described and surmounted by an unfluted, disc-shaped head  44  to create a plurality of undercuts  46  is provided to hold the cast teeth  26  and associated gums that depend from lower flat surface  14   a  of opposing quadrant  14 . The dental stone used to make the gums and teeth fills the apertures and the flutes. The respective heads  44  of the mounting posts  40  support the dental stone because the mounting posts depend from said flat lower surface. 
     FIGS. 8A ,  8 B, and  8 C depict a third embodiment where a working base  50  has the same structure as working quadrant  12  but is semicircular in configuration. As such, it represents a full lower set of teeth and not just a quadrant as in the first two embodiments. Opposing top member  52  also has the same structure as opposing quadrant  14  in all respects except that said opposing top member is semicircular and represents a full set of upper teeth and not just a quadrant as in the first two embodiments. The same reference numerals are used in view of the common structure of the three embodiments. 
   The novel structure thus removes much of the guesswork associated with prior art techniques. Thus, the level of skill required to make a good set of model teeth is substantially reduced. Much less time is required as well. A lab equipped with the novel system will also become known for its consistency and reliability. Moreover, patient complaints about ill-fitting crowns and dentures will diminish. 
   It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
   It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween. 
   Now that the invention has been described,