The patent's assignee for patent number 8784021 is
News editors obtained the following quote from the background information supplied by the inventors: "Computer technology has advanced to the point where a dental prosthesis may be milled from a solid block of material based on three-dimensional digital data corresponding to a proposed shape of the dental prosthesis. All methods of production begin with a model of the patient's dentition. The dentist will first make an impression of a patient's existing dentition, including the teeth immediately above and to the side of the tooth structure to which the dental prosthesis is to be attached. After first cutting away any unwanted tooth structure, thereby preparing the tooth to which the prosthesis is to be attached, the dentist has the patient bite into an impression material forming a negative impression of the patient's dentition. The negative impression is then filled with dental die stone to make a model. This model should duplicate the occlusion surfaces between upper and lower aligned teeth and the configuration of the prepared tooth structure to which the dental prosthesis is to be attached. Currently there is a newer, less common method of creating a model of the patient's dentition utilizing a digital impression. With digital devices placed in the mouth and using cad/cam technology to produce the finished model, the need for a physical impression is no longer there. Two such systems currently in use in
"The computer aided design equipment used to make a dental prosthesis has a scanner that is used to scan the surfaces of the model. Scanning may be accomplished either with optical techniques using laser or non-laser light or tactile techniques where a probe physically contacts the prosthesis's surface. The computer aided design equipment converts the model's surfaces into three-dimensional digital data corresponding to the physical shape of the model. This original data collected during scanning is then used to create an image of the proposed shape for the prosthesis on a screen of a computer monitor. The original image displayed on the monitor screen needs to be adjusted to modify the original image to correspond to the ultimate shape of the dental prosthesis. The computer aided design equipment is programmed to allow the technician, with the aid of a mouse and employing conventional point and click techniques, to change the shape of the image.
"Because the data originally collected during scanning isn't precise enough to make the dental prosthesis directly based on this data, the technician can and does make adjustments to the data originally provided by the scanner so that the dental prosthesis, at least in theory, fits properly into the patient's mouth. After making such adjustments to the data collected by the scanner, the adjusted three-dimensional digital data is then forwarded to an automatic milling machine that then mills away the unwanted material from a work piece to form the dental prosthesis. Typically, the work piece is a block of material comprised of ceramic, titanium, or a composite plastic material. Conventional investment casting is also used to make a dental prosthesis and a wax pattern may be milled from a work piece of wax that is then used in the investment casting process."
As a supplement to the background information on this patent, NewsRx correspondents also obtained the inventors' summary information for this patent: "Our jig device and apparatus, and method of making a prosthesis, have one or more of the features depicted in the embodiments discussed in the section entitled 'DETAILED DESCRIPTION OF SOME ILLUSTRATIVE EMBODIMENTS.' The claims that follow define our jig device and apparatus and method of making a prosthesis, distinguishing them from the prior art; however, without limiting the scope of our jig device and apparatus and method of making a prosthesis as expressed by these claims, in general terms, some, but not necessarily all, of their features are:
"One, in our method a milling machine mills from a two-sided work piece a dental prosthesis essentially free of defects. The milling machine has a cutting tool that terminates at a cutting tip that has, at a start position, an exact spatial relationship with respect to a working reference plane of the milling machine. A first side of the work piece is presented to the cutting tool, and starting from the start position, the cutting tool is operated to partially cut through the first side to form in the work piece a cavity having a surface part corresponding to at least a portion of the prosthesis being made. A floor of the cavity may include the surface part corresponding to at least a portion of the prosthesis being made. The work piece may be a substantially solid block having opposed, substantially parallel, planar sides, and it may be made of wax, metal, ceramic, or a plastic.
"Two, the cavity is at least partially filled with a support material and the work piece is inverted to present to the cutting tool a second or opposite side of the work piece. The work piece is inverted in a manner so that the surface part corresponding to at least a portion of the prosthesis being made, namely, the cavity is in an exact predetermined position with respect to the working reference plane of the milling machine. Starting from the start position, the cutting tool is positioned to overlie the second side directly over and opposite an un-milled segment of the work piece that supports the surface part corresponding to the partially milled prosthesis being made. When so positioned, the cutting tool is now operated to completely cut through the second side of the work piece and form completely a prosthesis with a surface essentially free of defects. From each side of the work piece, the cutting tool may only cut into the work piece to a maximum depth corresponding substantially to an optimum point of dissection of the prosthesis being made and no further. This defect free prosthesis is supported within the work piece by the support material, and the prosthesis is separated from the work piece as the final step in our method.
"Three, a jig device may be used to hold the work piece in the milling machine at a predetermined location so the jig device and milling machine are in an exact spatial relationship to enable the milling machine to precisely mill from the work. Our jig device is detachably mounted to a planar tabletop of the milling machine and can be detached, inverted, and re-inserted after milling the first side of the work piece into the machine at the same predetermined location. The jig device and milling machine may have interactive elements that enable the jig device to be repeatedly inserted, removed and inverted, and then reinserted into the milling machine at the same predetermined location with each insertion, or reinsertion after inverting. Thus, the jig device and milling machine are always in the same exact spatial relationship to enable the cutting tool to precisely cut from the work piece a prosthesis having a surface essentially free of defects. The jig device, when inserted or reinserted into the milling machine, may be in a first plane and the cutting tool may be at a right angle to this first plane. For example, our jig device when inserted or reinserted into the milling machine may be substantially oriented in a horizontal plane and the cutting tool may be substantially oriented in a vertical plane.
"In one embodiment, our jig device is substantially symmetrical about a central longitudinal line and substantially symmetrical about a central latitudinal line. Our jig device may include a frame structure in which the work piece is seated, where the frame structure may have opposed planar parallel surfaces that are, for example, spaced apart a distance substantially from 1/2 to 2 inches. There may be clamping means along the frame that keep the work piece in a stationary position within a space in the frame structure and an alignment arrangement along the frame member that provides locating structure to enable the jig device to engage locating structure on the tabletop. The alignment arrangement may comprise aligned openings positioned to intersect and engage a pair of aligned vertical post elements projecting outward from the tabletop directly or indirectly by way of a platform fixedly attached to the tabletop. Each post element slides into an individual opening upon mounting the jig device to the tabletop. The clamping means may include a plurality of detachable members that upon being fastened to the frame hold the work piece in the stationary position.
"Four, our apparatus makes a prosthesis from a two-sided work piece, and it includes a milling machine and a holder for the work piece that enables the work piece to be inverted. Our jig device and milling machine have interactive elements that enable the jig device to be repeatedly inserted, removed and inverted, and then reinserted into the milling machine at the same predetermined location with each insertion, or reinsertion after inverting. Consequently, our milling machine may be programmed to operate so the cutting tool precisely cuts from the work piece a prosthesis having a surface essentially free of defects. The work piece is moved from a first position, presenting to the milling machine's cutting tool a first side of the work piece, to a second position presenting to the cutting tool a second side of the work piece. A drive mechanism for the milling machine is initially operated when the work piece is in the first position so the cutting tool partially cuts through the first side of the work piece, to drill away a substantial portion of material from the work piece, while avoiding penetrating through the work piece with the tip of the cutting tool. This forms in one side of the work piece a cavity having a surface part corresponding to at least a portion of the prosthesis being made. The drive mechanism may move the tabletop from the start position laterally along the working reference plane in one or the other of orthogonal directions and rotates and moves the cutting tool from the start position towards and away from the tabletop along a straight line following the tool's longitudinal centerline. The drive mechanism returns the cutting tool and the tabletop to their respective start positions after partially cutting through the one side of the work piece to enable filling the cavity at least partially with the support material. The drive mechanism is operated to completely cut through the opposite side of the work piece after filling the cavity with support material to finish making a prosthesis having a surface essentially free of defects.
"In one embodiment of our apparatus, the milling machine's planar tabletop may be mounted to move laterally in a straight line along the working reference plane in one or the other of orthogonal directions. The cutting tool may be mounted to rotate and to move towards and away from the tabletop along a straight line. The cutting tool's longitudinal centerline may be normal to the working reference plane and intersects a reference point on the working reference plane when the tabletop and cutting tool are in the start positions. A locating structure for positioning the jig device in a predetermined location is on the tabletop. The locating structure enables an operator to manually insert the jig device into the milling machine at a predetermined location so the jig device and milling machine are in an exact spatial relationship allowing the cutting tool to precisely cut from the work piece the prosthesis being made. This locating structure may comprise a detachable platform including a pair of aligned vertical post elements projecting outward from the tabletop. It may be designed to position the jig device with a surface of the jig device adjacent, and substantially parallel to, the planar tabletop.
"These features are not listed in any rank or order nor is this list intended to be exhaustive."
For additional information on this patent, see: Luksch, Derrick; Luksch,
Keywords for this news article include: Dentistry, Technology,
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