Dentistry – Apparatus – Hand manipulatable implement
Reexamination Certificate
2000-10-12
2002-07-02
O'Connor, Cary E. (Department: 3732)
Dentistry
Apparatus
Hand manipulatable implement
Reexamination Certificate
active
06413088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an instrument for removing dental restorations, e.g. a crown restoration, a temporary crown, a post, a core, and a bridge, attached to natural teeth, artificial teeth, etc.
2. Description of Background Art
Conventional instruments for removing dental restorations are disclosed in Japanese Patent Application Unexamined Publication (KOKAI) Numbers [hereinafter referred to as “JP(A)”] 8-56960 and 7-100150.
JP(A) 8-56960 discloses a forceps- or pliers-like instrument having a pivot shaft. The instrument has a rod-shaped auxiliary member coaxially connected to the pivot shaft with a universal joint provided therebetween. To remove a dental restoration, slits are made in the dental restoration. Then, the jaws of the instrument are inserted into the slits to grip the dental restoration, and the distal end of the auxiliary member is axially tapped or pulled to thereby remove the dental restoration.
JP(A) 7-100150 discloses an instrument having a pair of levers each bent at the joint between a horizontal portion and a vertical portion in the shape of a 90-degree rotated L. Annular proximal end portions of the levers are pivotably connected together by a connecting stem. The levers have a pair of wedges projecting from the distal ends of the vertical portions so that the wedges face each other. The wedges are tapered toward each other's distal ends. The horizontal portions are connected at intermediate positions thereof by a rotating bolt so that the two bent levers can be opened or closed through threaded engagement between the rotating bolt and the horizontal portions, thereby allowing the spacing between the opposing ends of the wedges to be enlarged or reduced. To remove a dental restoration from a tooth, outer symmetric surfaces of the joint between the dental restoration and the tooth are cut to form wedge-shaped recesses with a slitter. Then, the wedges are inserted into the recesses, and the rotating bolt is rotated to reduce the spacing between the opposing ends of the wedges, thereby forcing the wedges into the recesses toward the center of the joint. By virtue of the taper formed on the wedges, when forced into the recesses, the wedges produce force acting on the tooth obliquely downward and force acting on the dental restoration obliquely upward. Consequently, the dental restoration is removed from the tooth.
However, the above-described conventional dental restoration removing instruments require that a dental restoration to be removed should be provided with slits (JP (A) 8-56960) or wedge-shaped recesses (JP (A) 7-100150) for engagement with the instrument in advance of the removal of the dental restoration. In other words, it is impossible to remove the dental restoration unless it is drilled or destroyed. Accordingly, a great deal of time is needed to remove the dental restoration, and the patient must bear the pain for an unfavorably long period of time. In addition, it takes the dentist a great deal of labor to remove the dental restoration. With the conventional dental restoration removing instruments, dental restorations once removed cannot be reused, which is unfavorable from the viewpoint of cost. Moreover, both the conventional instruments suffer from the problem that the arrangement of the instruments is completed, and the production cost is undesirably high, and further the operation is complicated.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, an object of the present invention is to provide a dental restoration removing instrument free from the above-described problems with the prior art.
To attain the above-described object, the present invention provides a dental restoration removing instrument, e.g. a forceps or a pair of pliers, of the type wherein a pair of jaws at the distal end of the instrument grip an object in response to an operation of closing a pair of handles. The pair of jaws have distal ends that can be wedged into the boundary between a tooth and a dental restoration from both sides thereof. The distal end of each jaw has an angle whereby the tooth can be pushed downward and the dental restoration can be pushed upward. The instrument has an opening angle adjusting device for adjusting the opening angle between the jaws so that the distal ends of the jaws will not bite into the boundary between the tooth and the dental restoration more than a predetermined amount.
The angle is provided at the distal end of each jaw allows the jaws of the instrument to be wedged into the boundary between the tooth and the dental restoration without the need to provide slits or recesses in the dental restoration. Therefore, the instrument can be engaged with the dental restoration without destroying the latter. In addition, the dental restoration can be removed with the instrument without a possibility of undesirably pulling out the tooth together with the dental restoration, and without applying such a force that destroys the tooth or the dental restoration when the object is gripped with the instrument.
Further, because the opening angle of the instrument can be set in conformity to the tooth under treatment by adjusting the opening angle adjusting device, there is no possibility that the jaws will excessively bite into the boundary between the tooth and the dental restoration, causing the tooth or the dental restoration to be damaged.
Preferably, the distal end of each jaw has a wedge-like shape with a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration. The angle is so determined that the distal end of each jaw is disposed perpendicularly to the axis of the tooth.
By virtue of the above-described arrangement, it is possible to insert the distal ends of the jaws into the boundary between the tooth and the dental restoration while wedging the boundary by applying an upward pushing force to the dental restoration without a possibility of undesirably pulling the tooth together with the dental restoration and without applying unnecessary force to the tooth. Accordingly, the distal ends of the jaws can be readily wedged into the boundary between the tooth and the dental restoration without damage to the tooth even if the dental restoration is not provided with slits or recesses for engagement with the distal ends of the jaws.
When the instrument is gripped to remove the dental restoration, force is applied to the tooth from the outer slant portions contacting the tooth. In this case, however, the inclination angle of each outer slant portion causes the force to be applied to the tooth obliquely in a dispersed state from an upper portion at each side of the tooth toward a lower central portion thereof. Therefore, it is unlikely that the tooth, which is not very resistant to force applied vertically, will be damaged. On the other hand, strong force is applied to the dental restoration so as to push it up. Accordingly, the joint portion of the dental restoration is smoothly disengaged from the tooth, and thus the dental restoration is removed from the tooth.
Preferably, the distal end of each jaw has an inner slant portion, a first outer slant portion adapted to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The predetermined angle of the distal end of each jaw is as follows. When the distal ends of the jaws are disposed perpendicularly to the axis of the tooth, the inner slant portion has an inclination angle of about 20±5 degrees with respect to a horizontal plane perpendicular to the axis of the tooth. The first outer slant portion has an inclination angle of about 35±5 degrees with respect to the horizontal plane. The second outer slant portion has an inclination angle of about 1±1 degrees with respect to the horizontal plane.
The opening angle adjusting device may be a screw th
Greenblum & Berstein P.L.C.
O'Connor Cary E.
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