Plastic laminar digitally indexed dental die system

A device for construction of removable dental dies fabricated from type IV dental die stone poured into non-rigid impression materials. The device eliminates the need for a two pour system necessitated when individual pins are used, provides large surface area for positive seating of the individual dies, and in general eliminates the complicated alignment problems associated with other systems in common use. The invention comprises a polymer sheet having projections on both sides for embedment in dental store of the date of the die and base.

The present invention provides a means of both indexing and separating 
removable dental stone dies from the adjacent portions of a quadrant or 
full arch dental stone model. 
The device consists of a twin sheet of polymer plastic having round conical 
projections on one side and round inverted conical projections on the 
opposite side. The projections are uniform in size and shape and spaced at 
regular intervals.

The device may be manufactured in the configuration indicated in FIG. 2 
using conventional molding techniques if a flexible mold is used. This is 
necessitated to facilitate removal of the undercut projections from the 
mold. If on the other hand a rigid mold is used, the plastic sheet would 
be produced as indicated in FIG. 3 and in the enlarged view FIG. 4. The 
undercuts on the retentive side are then either machined into the 
projections or the projections are heated and depressed to produce the 
configuration indicated in the side view of FIGS. 5-2. 
FIG. 6 is a cross sectional view illustrating the use of the die system 
with a conventional impression and model pouring technique. The impression 
tray 3, containing a non-rigid impression 7 is prepared for pouring with 
stone die material. The illustration in FIG. 6 indicates the commonly 
employed "beading and boxing" of the impression with beading wax 6 and 
boxing wax 4. A section of the is cut which will fit the width and length 
of the portion of the impression from which the dies are to be fabricated. 
The prepared section of the indexing sheet is then affixed to the 
impression material in such a manner as to be perpendicular to the desired 
path of withdrawal of the removable die. Wax or any suitable luting agent 
5 is used to secure the indexing sheet to the impression material. The 
sheet is oriented so that the retentive side 2 faces the impression 
material 7 and the indexing side 1 will face the base of the completed 
model FIGS. 7-11. 
FIG. 7 indicates the poured die model after separation from the impression 
and illustrates the submerged indexing sheet 10. The broken lines 9 
indicate the path of the saw cuts which will be made to separate the 
prepared tooth 8 from the completed die model. 
FIG. 8 indicates the removal of the die 8 with the index 10 attached to its 
base after saw cuts have been completed. The conical projections on the 
index 10 provide for accurate replacement of the die 8 into the model 11. 
The system eliminates many pitfalls inherent in the other commonly used 
methods of die construction. 
I. The most common method involves the use of dowel pins, which consists of 
a tapered conical brass pin having one side flattened. The retentive end 
of the pin is knurled so as to be mechanically retained in the dental die 
stone. This pin must be alaigned and held into place over the impression 
of the prepared tooth during the initial pour. Sufficient die stone is 
poured into the impression so as to engulf only the knurled end of the 
pin. A separating medium must then be placed on the exposed portion of the 
stone which overlies the prepared tooth, and a second pour is made to 
engulf the conical portion of the pin. Provisions must be made to insure 
that the second pour of stone is retained to the first except in the 
vivinity of the portion that represents the prepared tooth. Saw cuts are 
then made to release the die. This method requires two pours of stone, 
necessitates time consuming alignment of the pins, and the finished die is 
prone to inaccuracy because of the limited surface area on the flattened 
portion of the pin which is intended to prevent rotation of the die. 
II. The so-called die-lock tray requires that the die model be poured and 
trimmed to fit the tray. A second pour is then required to adapt the die 
model to the tray. The tray is then separated, the die portion of the 
model is sawed, and the pieces are re-oriented and replaced in the tray. 
Problems associated with this method involve the need for tedious trimming 
of the die model for adaptation to the tray as well as inaccuracies 
associated with reassembly of the constituent parts after they have been 
sawed apart. 
III. The pindex and pin mate systems both involve the use of a pin 
arrangement which is retained in the die portion of the model as a 
precision sleeve into which the pin fits. The sleeve is retained by a 
second pour of stone, and in both cases, complicated measures are 
necessary for alignment of the pins and a second pour is necessary to 
retain the sleeve portion of the system. The surface area which provides a 
positive seat for vertical orientation of the die is limited, which 
reduces the accuracy of the system. In addition, a separating medium must 
be employed to insure separation of the die model. 
IV. The "Logix" system involves the use of a plastic tubular insert which 
is affixed to the impression. The tube becomes submerged in the die stone, 
and serves as both the separating medium and the indexing device. The 
problems associated with this system include the fact that the plastic 
tube is difficult to locate within the substance of the stone model in 
order to make saw cuts for separation. The method produces a die which is 
very fragile, difficult to separate, and has an extremely limited surface 
area to provide a positive vertical seat. 
V. The present system, avoids the necessity for two pours. The laminar 
nature allows it to function as both the separating medium and the 
indexing system. The flat sheet interspersed between the conical 
projections provides a large surface area to insure a positive vertical 
stop which insures accurate removal and replacement of the die portion of 
the model. The fact that the system utilizes numerous conical projections 
rather than a single pin precludes rotational inaccuracies in the 
fabrication of the die. Because the sheet can be cut to the desired size 
and easily oriented and affixed to the impression, it eliminates many of 
the time consuming aspects of die fabrication. The location of the 
indexing system within the substance of the stone is easily determind 
because the laminar sheet extends to the facial and lingual aspects of the 
impression. The numerous undercut projections on the retentive side 
preclude failure of the mechanical bond between the stone and the 
retentive end of conventional pin systems. The need to use adhesives for 
retention of the pins is also eliminated.