Dentistry – Apparatus – Work support
Reexamination Certificate
2000-11-10
2001-11-20
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Apparatus
Work support
C433S060000, C433S213000
Reexamination Certificate
active
06318998
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to low cost, glue-free dental model articulators and methods of making them.
BACKGROUND OF THE INVENTION
A dental articulator is used to connect dental models of upper and lower sets of teeth and to simulate the movement of the patient's jaw. Early articulators were large, cumbersome devices, usually made of metal, and the teeth models were attached to them with plaster. The next generation of articulators were also metal, but they were smaller and easier to manipulate. The models still attached to them with plaster, however, and the process of articulation remained time-consuming and messy. The most common articulators currently used in the field are made entirely of plastic. Models are attached to the articulators with super glue instead of plaster, and they are much easier to handle and work. The current system, however, does offer opportunities for improvement.
The VERTEX articulator system sold by Ceramco of Burlington, N.J., represents the type of articulators currently used in the art. See FIG.
1
. The VERTEX system consists of three parts: plastic sockets (
1
), plastic hinges (
2
) having mounted plastic balls (
3
) matching the plastic sockets and rubber base molds (
4
and
5
). The rubber base mold is customarily in the form of a half mold (
4
) which allows the modeling of an entire set of upper or lower teeth, or a quarter mold (
5
), which allows only modeling of one half of a set of upper or lower teeth. Plaster is poured into the rubber base mold (
4
or
5
), model teeth (not shown) are anchored in the upper surface of the uncured plaster and then the plaster is allowed to set. After curing, the upper teeth hardened base and lower teeth hardened base containing the model teeth are removed from their respective rubber molds. The plastic sockets (
1
) are then glued to the ends of an upper teeth hardened base and a lower teeth hardened base. The plastic balls (
3
) on the hinges (
2
) are then inserted into the sockets (
1
) and the model teeth in the molds are aligned to match the natural bite (occlusion) of the subject. Once the model teeth are properly aligned, the balls (
3
) are glued into place in the sockets (
1
) to fix them in that alignment, while the hinges (
2
) are left freely moving to represent opening and closing of the mouth.
This system suffers from several drawbacks. The super glue used (cyano acrylate) is hazardous and unpleasant to work with. The entire hinge unit, including the sockets, easily breaks off of the hardened base, and the rubber base molds accumulate bits of hardened plaster over time, particularly in its corners, which mar the surface of the base units made in them and makes removal of the hardened base unit increasingly difficult over time.
Accordingly, it is an object of this invention to provide a low cost, plastic, dental-model articulator which is less likely to break away from the dental model base.
It is a further object of this invention to provide a low-cost, plastic, dental-model articulator which does not require the use of glue to assemble the finished, articulated dental model.
It is yet another object of this invention to provide a method of forming an articulated dental model with fewer mold marks and improved strength in the attachment of the articulating hinge to the upper and lower teeth bases.
It is still another object of this invention to provide a significant improvement in the physical protection of the model base and the model teeth.
SUMMARY OF THE INVENTION
The foregoing objects are achieved by the dental articulator and method of articulating a dental model described below. The dental articulator of the instant invention is constructed of a pair of substantially inflexible bands for encircling the upper and lower dental model bases, a pair of spheres with attached mechanical means for securing them to one of several attachment sites formed on the outer surface of the substantially inflexible bands, and a hinge assembly formed of a pair of elastic arcuate arms joined at their ends by a hinge mechanism and having at their apexes opposing grips for clamping one of the spheres between them. The grips can be spread enough to admit the sphere between them by flexing the arcuate arm, and after the flexion is released, the grips clamp the sphere with sufficient force to prevent relative motion between the sphere and the clamps. By attachment of the sphere to different attachment sites on the substantially inflexible band and rotation between the hinge assembly and the upper and lower dental model bases allowed by adjusting the clamping location on the sphere, an articulation which mimics the bite of the patient can be achieved.
Advantages of the instant articulator include the avoidance of toxic and messy glue, which has previously been necessary to attach an attachment site to the dental model bases and to fix the attachment of the hinges to the attachment site; the ability to readjust the articulation at any time, which was impossible with glue use; a lower incidence of breakage in the articulator; and improved durability, appearance and strength of the dental model bases, the plaster of which is now protected by the band that surrounds it.
The pair of substantially inflexible bands is provided for encircling the upper and lower plaster bases of the dental model. The substantially inflexible bands include a retaining means for extending into the plaster base and securing the substantially inflexible bands to the plaster base. Preferably, this retaining means is a protrusion, such as a rib, on the interior surface of the band, and the plaster base of the dental model is formed by placing the substantially inflexible band on a base mold cap to form a mold, pouring uncured plaster into the mold and allowing it to cure, thereby embedding the protrusion in the plaster. Alternatively, the substantially inflexible band can be placed around an already formed plaster base and any known retaining means can be used to attach them together, such as nails or screws. The band provides a durable cover for the plaster base and a smooth, attractive side for the plaster base, absent the mold marks encountered with prior art articulators. The substantially inflexible bands also provide at least one attachment site for the sphere on their outer surface. Preferably, the attachment site is a molded form which mechanically mates with a molded form on the sphere to firmly attach the sphere to the band. Alternatively, the attachment site could simply be an outer surface on the substantially inflexible band to which the sphere can be attached by mechanical means such as a nail, screw or rivet attached to the sphere. The bands must be substantially inflexible so that they form a good mold for pouring plaster into and so that they form a secure anchor site.
The sphere has an attached mechanical means for securing the sphere to the attachment site on the substantially inflexible band. Preferably, the mechanical means is a molded part which mates with the molded form of the attachment site to provide a secure, glueless attachment. Alternatively, the mechanical means could be a means of attaching to the band by penetrating it, such as a nail, screw or rivet. The surface of the sphere is preferably textured, in order to increase the friction and reduce the chance of relative motion between it and the working clamp.
The hinge assembly is composed of two elastic arcuate arms connected to each other at their ends by a hinge mechanism. At the apex of the convex side of each arcuate arm is a pair of opposing grips which are sized and shaped to clamp the sphere between them. By compressing the two ends of an arcuate arm toward each other, the arc is flexed and the opposing grips will be separated sufficiently to place them around the sphere. Once the flexing of the arc is released, the elastic arc returns to a position in which the opposing grips are forced together to clamp the sphere with sufficient pressure to prevent relative rotation of the sphere between the grips. Preferably, th
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