Dentistry – Apparatus – Having static product shaping surface
Reexamination Certificate
2000-11-15
2002-07-30
Wilson, John J. (Department: 3732)
Dentistry
Apparatus
Having static product shaping surface
Reexamination Certificate
active
06425759
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the dental industry and, more particularly, to dental tools which are used in the production of dental cast models.
In the dental industry, technicians commonly construct dental models. A dental model of the entire mouth of a patient typically comprises an upper jaw model and a lower jaw model which are affixed to one another by an articulator. An articulator is a device comprising upper and lower mounting platforms which are connected to the upper and lower jaw model elements. The articulator enables for centric, lateral and protrusive movement of the upper jaw model relative to the lower jaw model in order to closely simulate the relationships and the actual movement, or bite, of the mouth of the patient.
Various types of devices and procedures have been used in the art for creating dental models.
One method for manufacturing dental models which is well known and commonly used in the art involves molding the dental model using a casting material. Specifically, one or more impression trays are filled with rubber based impression material. Each impression tray is then urged into the mouth of the patient so as to create a negative impression of the teeth of the patient into the rubber based impression material. If necessary, excess impression material is trimmed from the impression tray after the negative impression is formed.
After the negative impression has been formed, the impression tray is typically transported to a dental laboratory where the dental cast model is manufactured. Specifically, the negative impression created in the impression tray is filled with a soft casting material, such as dental stone, plaster or epoxy. The impression tray is then inverted and mounted upon a pre-formed mounting device, such as a dental cast tray or base. After the casting material has had an opportunity to harden, the impression tray is removed so that the casting material forms a positive dental impression on the mounting surface.
Molded dental models are often used to manufacture crowns, bridges, inlays, dentures and other dental prosthetics outside of the mouth of the patient. The construction of dental prosthetics typically necessitates the ability to remove one or more individual model teeth from its spatial physical relationship relative to the remainder of the dental cast model for the purpose of constructing accurate margins and contours. In the event that two or more individual units of bridgework are to be joined, it is necessary that the working model segments be accurately and repeatedly returned to their original relationships precisely as they existed prior to any cutting, separations or disassembly of the model.
In order to effectively remove an individual model segment from the remainder of the dental model, the entire jaw model is typically removed from the mounting device and positioned upon a flat cutting surface, such as a table. A cutting device, such as a saw, can then be used to separate the desired model teeth from the remainder of the dental model. After the technician has completed manufacture of the dental work, the dental model can be re-assembled onto the mounting device.
It should be noted that during the re-assembly of the dental cast model, it is essential that precise registration and desired alignment be maintained between the working model segments and the remainder of the molded dental cast model.
In U.S. Pat. No. 5,393,227 to W. H. Nooning, there is disclosed a dental impression handling tool consisting of two base structures shaped to approximate two opposite quadrants of a full dental arch, and two similarly-shaped inserts that snap fit into the base structures. Each base includes a wide, upward facing trough approximating the placement and curvature of teeth within a dental quadrant. The upper surface of each insert is attached to a positive dental mold by means of protrusions that extend from the top horizontal surface of the insert, the protrusions being encased within the mold material. Positive positional relationship is maintained between each base and its mating insert by the use of an interlocking and non-recurring geometric pattern that is carried by the internal vertical walls of the trough in the base, and by a matching geometric pattern that is carried by the outer vertical walls of two vertically downward extending ribs on the underside of the insert. A second deeper, narrow and centrally located trough is formed in each base. This second trough mates with a third center rib that protrudes from the bottom surface of each insert. The insert's center rib contains a retainer bead along both vertical side walls. This bead provides a snap-lock fit into a corresponding negative indentation formed along the vertical side walls of the center trough of in each base. The center rib in each insert contains cylindrical cavities which allow the insertion of standard dental dowels or suitable substitutes.
Dental impression handling tools of the type described above in Nooning have been found to be experience numerous drawbacks.
As a first drawback, dental impression handling tools of the type described above in Nooning are undesirable in that the base comprises an elongated slot into which debris, such as plaster, can collect. As a result, it has been found that the insert is often unable to secure a proper fit within the base structure, thereby precluding proper alignment, which is highly undesirable.
As a second drawback, dental impression handling tools of the type described in Nooning are undesirable in that the bottom surface of the each insert includes various sized ribs, thereby creating a bottom surface which is highly unstable. As a result, when the insert is placed upon a laboratory table in order to cut the desired model teeth from the remainder of the dental cast model, the non-flat and unstable nature of the bottom surface of each insert renders the cutting process extremely difficult, which is highly undesirable.
Accordingly, in U.S. Pat. No. 6,106,284 to R. J. Cronin et al., there is disclosed, in one embodiment, a dental cast tray assembly used to form a dental cast model which comprises a base and a tray removably mounted on the base. The base includes a top surface, a flat bottom surface, a front wall, a rear wall and a plurality of projections formed on its top surface in a non-recurring, random pattern. Each of the plurality of projections is generally cylindrically-shaped and includes a convex free end. The tray includes a top surface adapted to support the dental cast model, a flat bottom surface, a front wall, a rear wall, a retention bar formed on its top surface and a plurality of openings formed in its bottom surface in the same non-recurring, random pattern in which the plurality of projections are disposed on the base. Each of the plurality of openings is defined by four sidewalls and is generally hourglass shaped in lateral cross-section. Two of the four sidewalls which define each of the plurality of openings include an elongated rib. In use, the tray is mounted on the base such that the bottom surface of the tray abuts against the top surface of the base and so that the front wall of the tray is flush with the front wall of the base. With the tray mounted on the base, one projection in the base projects into an associated opening in the tray, the elongated ribs serving to retain each projection within its associated opening with limited retention.
Although highly effective in constructing a dental cast model, the dental cast tray assembly described in Cronin et al. suffers from a couple notable drawbacks.
As a first drawback, the dental cast tray assembly described in Cronin et al. is difficult to manufacture due to the T-shape of the retainer bar. Specifically, the undercuts of the T-shaped retainer bar are difficult to create using conventional molding processes, thereby increasing the overall cost to manufacture the dental cast tray assembly, which is undesirable.
As a second drawback, utilization of the dental cast tray assembly describe
Bumgarner Melba
Kriegsman & Kriegsman
Wilson John J.
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