Tooth preparation instrument and system of its use

[0002] The present invention consists of a tooth preparation instrument and system that creates a tapered conical shape from a tooth, with pre-determined dimensions, making it possible for a lab technician to independently and simultaneously create a crown that exactly fits the prepared tooth. The crown is ready for permanent placement on the prepared tooth at the time of preparing the tooth. Use of the invention saves considerable time and effort as compared with current methods.

[0003] Currently, a tooth is prepared for a crown in the following manner. First, during an initial office visit, the dentist makes an impression of the portion of the mouth in which the tooth is located, with upper and lower occusal surfaces. From this impression a lab technician will later create a stone study model.

[0004] The dentist then removes tooth material with a high-speed drill, relying on eyesight and expertise to create a form on which a crown will be cemented. This form begins with a narrow shoulder at the gum line and tapers inward as it rises to a flattened top that ends just below the lowest level of the tooth's original biting surface.

[0005] The dentist then makes an impression of the prepared tooth and sends it to the lab technician along with the tooth impression, prepared prior to removal of tooth material. The dentist makes and installs a temporary crown for the prepared tooth.

[0006] Using the impression of the prepared tooth, the lab technician produces a crown that matches the dentist's color and material specifications and sends it to the dentist. At the patient's second visit, the dentist tests and adjusts the crown as necessary before cementing it in place.

[0007] By the present invention, the following steps will be performed. At an initial office visit, the dentist makes an impression of the portion of the mouth in which the tooth is located, with upper and lower occusal surfaces. From this impression the lab technician will later create a stone study model.

[0008] The dentist, at a second office visit or, in a preferred embodiment, during the same office visit when a lab technician is available in the office for simultaneous creation of the crown, presses a surface contour tool against the biting surface of the tooth to determine the depth settings for at least one burr in a surface tool that will remove the upper surface of the tooth and create a working surface for the material removal device.

[0009] The dentist inserts at least one burr with the proper length in this tool so that when the tool is lowered onto the tooth, a flat surface will be created. It is essential that this surface be aligned perpendicular to the center line of the tooth. The dentist also calculates the center of the tooth and sets the depth of the burr that will drill the center hole for guiding the material removal device.

[0010] The flat surface tool and the center hole drilling burr are operated with a device that locks onto the tooth and ensures that the top surface of the tooth will be perpendicular to the central line of the tooth. The dentist makes two calculations. First, the distance in 0.1 mm increments between a predetermined point below the lowest level on the tooth's biting surface (beginning level) and the gum line (ending level). This will be the height of the prepared tooth. The second calculation is the distance from the center of the tooth's biting surface to a predetermined point inside the narrowest part of the tooth at the gum line (the shoulder). This will be the radius at the shoulder of the prepared tooth. The dentist inserts tapered burrs of predetermined lengths and a guide pin of the required length into the material removal device and feeds the calculations into a computer processor which will control the material removal device. A print out of the calculations is forwarded to the technician for confirmation of the requirements for the prepared crown or a bridge.

[0011] To initiate operation of the material removal device, a center hole is drilled. A flat surface tool is used to remove tooth material, smoothing the surface as necessary. The dentist inserts the guide pin of the material removal device in the center hole and begins to remove material from the side of the tooth. Each cycle around the tooth removes 0.1-0.5 mm. The various burrs are tapered and may be diamond burrs to create the required chamfer on the sides of the tooth.

[0012] The device has four computer controlled lights to guide the dentist. A green light indicates that the device is level with the top surface. A blue light is activated when a desired depth is achieved as also limited by the length of the burr. Two lights (one red and one yellow) warn the dentist that the device is tilted so that it is creating an undercut (red) or drilling too far toward the outer edge of the shoulder (yellow).

[0013] After each cycle, the dentist moves the depth setting another 0.1-0.5 mm until the required depth is reached. The burrs on the device, ranging in number from one to six, are preset so that they cannot be extended beyond the depth that has been calculated by the dentist.

[0014] While the dentist has been removing tooth material the lab technician has independently and simultaneously, if the technician is immediately available produced a crown or bridge that will fit the prepared tooth. The prepared crown will have the same internal dimensions as the prepared tooth and also the same characteristics (color, shape) as the original tooth.

[0015] Some of the advantages of the invention are that a dentist can prepare a tooth knowing that the crown will fit precisely, because the prepared tooth will have the same exterior dimensions as the interior opening on the crown so that the crown will precisely fit the prepared tooth. In addition, only one office visit is necessary to prepare the tooth and install a permanent crown. A patient will not require a temporary crown. The dentist will not have to make an impression of the prepared tooth and wait for the technician to produce the crown.

[0016] Alternatively, a series of pre-prepared crowns of various shapes and colors may be available to the dentist. Since the tooth will be prepared to a predetermined truncated cone size, pre-formed crowns having a similar pre-formed internal truncated conical recess may be available to the dentist. This would insure immediate accurate crown installation during a single office visit.

[0017] Accordingly, it is an object of the present invention to provide a tooth preparation instrument and system of its use including preparing an impression of a portion of a mouth in which a diseased tooth is located and simultaneously preparing or using a pre-formed permanent crown during the same office visit during which the impression was made with the crown having a predetermined internal recess calculated to exactly match a predetermined prepared tooth size so that the crown may be permanently secured to the prepared tooth during a single office visit.

[0018] It is another object of the present invention to prepare a tooth based upon a predetermined internal recess of the crown so that the internal recess of the crown will match the prepared tooth for permanently securing the crown during a single office visit.

[0019] It is yet another object of the present invention to control the preparation of a tooth for receipt of a crown so that the external dimensions of the prepared tooth coincide with the internal dimensions of the crown and the exterior surface of the crown matches the original shape of the tooth prior to preparation, including taking an impression of the tooth, preparing the crown and installing the crown during a single office visit.

[0020] These and other objects of the invention, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.

[0021] FIG. 1 is a perspective view of a tooth to be treated by the method, apparatus and system of the present invention.

[0022] FIG. 2 is a perspective view of a tooth having a flat surface ground on the top of the tooth and a round pattern disk being placed on top of the flat surface.

[0023] FIG. 3 is a perspective view of a tooth having an upper portion ground into a cylindrical configuration approximating the diameter of the disk placed on top of the tooth as shown in FIG. 2.

[0024] FIG. 4 is an exploded view of a compass grinder and a drill bit located in a hand piece providing a rotating force to the drill bit.

[0025] FIG. 4A is an alternate embodiment of a drill bit.

[0026] FIG. 4B is another alternate embodiment of a drill bit.

[0027] FIG. 5 illustrates the use of the compass grinder of the present invention to impart a predetermined angle of taper to a side wall of a prepared tooth.

[0028] FIG. 6 is a side view illustrating application of a predetermined angle to a predetermined depth into a cylindrically formed upper portion of a tooth.

[0029] FIG. 7 is a side view illustrating the predetermined angle imparted to an upper portion of a prepared tooth.

[0030] FIG. 8 illustrates the process of monitoring the drilling process and alerting a dentist to the correctness of the desired depth and angle of removal of tooth material.

[0031] In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

[0032] With reference to the drawings, in general and to FIGS. 1 through 5, in particular, the method, apparatus and system embodying the teachings of the subject invention is shown. With reference to FIG. 1, a tooth 10 is shown located between two adjacent teeth 12 and 14, extending below a gum line 16.

[0033] In FIG. 2, after an impression has been made of the tooth, the tooth 10 has had its upper surface 18 ground into a flat surface 20 which is approximately at a depth of the lowest indentation 19 projecting downwardly from the upper surface 18 in the pretreated tooth 10. The flat surface 20 will provide a reference plane for further treatment of the tooth 10 by attaching a crown to the tooth.

[0034] A perfectly round pattern disk 22 of paper, plastic or other disposable material of an appropriate size for each tooth so as to form a complete circle within the confines of all lateral edges of the flat surface 20 of the tooth is selected and placed on top of the flat surface 20 of the tooth 10. A bottom surface of the disk.22 includes an adhesive to maintain the positioning of the disk 22.

[0035] The pattern disk 22 is used as a guide to grind the sides of a tooth 10 to a nearly perfect cylindrical shape as shown in FIG. 3. A shoulder 24 of the tooth is maintained at the bottom of the cylindrically shaped portion, adjacent to the gum line 16. At the flat surface 20 of the tooth is drilled a hole 26 of an approximate depth of ⅛ of an inch and having a diameter of approximately {fraction (1/32)} of an inch.

[0036] In FIG. 4, a compass grinder guide 30 is shown having a tapered pin 32 at one end of the compass grinder guide for engaging the hole 26 on the top of the tooth. A radially extending bar portion 34 interconnects the pin 32 with an annular drill bit holder 36 having a hollow portion 38 for receipt of a drill bit.

[0037] A drill bit 40 has one end 42 mechanically anchored by a snap connection in a drill head 45. The drill head 45 is connected to a drive shaft 46 which extends through a handle portion 48 of a dentist drill. The shaft 46 and drill head 45 impart high speed rotational force to drill bit 40.

[0038] The drill head 45 may be air or battery driven. Alternatively the drill head and the shaft are removable from the handle portion 48 so as to limit the portion of the instrument that would need to be sterilized between different patients.

[0039] An internal lubrication system may be used to minimize drag on the drive mechanism of the drill bit. An edible oil, such as peanut oil, may be used to lubricate parts of the drill as necessary.

[0040] At the opposite end 44 of the drill bit 40 is located a tapered drill portion 46. The angle of taper and length of the drill portion 46 is varied depending upon the inclination and depth desired for the tooth prepared to receive a crown.

[0041] In FIG. 4A, an alternate drill bit 41 is shown. In this drill bit, a radially extending plate 43 located above the drill portion 45 provides a limit or stop to the depth of drilling possible by the drill portion 45. The plate 43 will engage the top of the prepared tooth to prevent further downward drilling.

[0042] In FIG. 4B, drill bit 47 includes a narrowed diameter shank 49 as compared to larger diameter drill portion 51. The shank 49 visually alerts the dentist to desist from further drilling due to having reached a predetermined depth as measured by the height of drill portion 51.

[0043] As shown in FIGS. 5 and 6, the compass grinder guide 30 is anchored in the upper surface 20 of a prepared tooth after removal of the pattern disk 22. The pin 32 engages in the hole 26 of the upper surface of the tooth. The drill bit 40 extends through the hollow portion of the bit holder 36. The drill bit 40 is set into the bit holder 36 to a predetermined depth so that the drill bit 46 will project from below a bottom surface 50 of the bit holder 36 to a predetermined depth.

[0044] By anchoring the pin 32 in the hole 26 and rotating the drill handle about the hole 26, using the hole 26 as a central axis, the grinding away of the tooth, as shown in FIG. 5, produces a truncated cone portion 52 as shown in FIGS. 6 and 7. Depending upon the angle of taper of the drill bit 46, the angle α, preferably between 1 and 10°, and more preferably between 3 and 8°, as shown in FIG. 7, will be varied to impart a predetermined taper to the upper portion of the tooth being prepared to receive a crown.

[0045] Simultaneously with and in preparation of securing a crown to a tooth, a crown is prepared by a lab technician having an internal recess of a predetermined base diameter, a predetermined depth and a predetermined diameter at the uppermost portion of the recess of the crown. The internal recess of the crown will exactly fit on the truncated conical portion 52 of the tooth 10 simultaneously prepared by the dentist, as shown in FIG. 7.

[0046] As shown in FIG. 8, the grinding of the tooth 10 may be monitored by a television camera 60 having an optic fiber cable 62 secured to the handle 48 of the drill by a band 64. The cable transmits an image of the grinding operation to a monitor 66 and a computer controller 68 by line 78. The computer controller 68 activates a series of four lights 70, 72, 74 and 76 by line 80 depending upon the accuracy of the procedure being performed.

[0047] For example, a green light 70 would be activated to indicate that the compass grinder is positioned parallel to the upper surface 20 of the tooth. A blue light 72 would indicate that a desired depth or inclination is being achieved by the drill bit as also limited by the length of the burr. Alternatively, different sized burrs can be used to change the depth of penetration into the tooth. A red light 74 would warn that the drill bit is tilted creating an undercut whereas a yellow light 76 would indicate that an outward tilting of the drill bit is occurring to create an increased diameter portion of the truncated conical portion 52 or that the desired cutting depth is close to being achieved.

[0048] These lights as controlled by controller 68 will ensure an accurate mating of the prepared tooth with the simultaneously prepared crown which is made on the basis of an impression of the original tooth configuration as shown in FIG. 1. Based upon the knowledge that the upper surface of the prepared tooth will be flat at the deepest groove of its original surface and that a predetermined drill bit will be used to introduce a predetermined angular inclination of a tapered conical portion, to a predetermined depth, a crown can be prepared so that the crown may be secured to the tooth at the time of preparation of the tooth without a need for a subsequent office visit by the patient.

[0049] The foregoing description should be considered as illustrative only of the principles of the invention. Since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.