Dentistry – Apparatus – Hand manipulatable implement
Patent
1986-09-03
1988-02-16
Wilson, John J.
Dentistry
Apparatus
Hand manipulatable implement
433120, 433150, 433153, A61C 308
Patent
active
047252332
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device with the characteristics recited in the preamble to claim 1. The device is accordingly employed to remove crowns, overlays, bridges, etc. secured with cement to the stumps of one or more teeth.
A device of this type is known from U.S. Pat. No. 3,889,376. Two opposing jaws are positioned in an extraction frame and are designed and intended to act on the surface of the crown, bridge, or other structure in such a way as to gently remove it from the stump. The device also includes a mechanism for applying an extracting force to the extraction frame in a direction opposite the one that the device is inserted in. The mechanism consists of a bridge that spans the jaws and of a screw that can be screwed into a thread in the bridge. To remove the crown it is necessary to drill through it first to allow the screw to rest against the stump when the extracting force is applied. This damages the crown, which cannot be employed again. The jaws consist at least partly of rapidly hardening plastic that adapts to the surface of the crown.
A device with two jaws suspended on parallel axes of rotation in an extraction frame and capable of being pivoted toward or away from each other is known from page 66 of the periodical ZWR 11 (1980). Using the device presupposes that the jaws will catch or can be engaged beneath a projecting edge of the crown. The motion of the jaws can generally be counteracted or eliminated with a nut to prevent them from coming loose from the crown that is to be removed. This device as well can only be employed in conjunction with drilling a hole through the masticatory surface of the bridge for a spindle to rest against the stump through. The spindle is secured in the extraction frame by means of a thread. A sort of ratcheted wrench is employed to apply the requisite extracting force by twisting the spindle in relation to the extraction frame. The force develops over the thread very slowly, however, which is a drawback because the only way to release the crown is to break up the cement that attaches it or to overcome the force of the cement. Furthermore, this known device can often not be employed at the side of the oral cavity because the ratcheted wrench takes up a lot of space vertically when applied to the spindle. There must also be a lot of space available for rotating the wrench. There are various embodiments of the jaws to allow adaptation to various types of crowns, bridges, etc. Using this device presupposes that the crown has a projecting edge and accordingly differs in design from that demanded in contemporary dentistry. When the stumps of the teeth are prepared to below the edge of the gums, the gum must be forced away, especially to make it possible to apply the jaws, which is especially hard on the sleeve of the neck of the tooth and can eventually lead to the loss of the stump. This known device does, however, entail the advantage that the force that is employed is already oriented against the direction that the crown, bridge, etc. is inserted in, assuming that the jaws allow engagement in a position or at an angle corresponding to the direction of insertion.
Another device, known from U.S. Pat. No. 3,690,007 consists essentially of two jaws that are connected to each other in such a way that they can be pivoted, enabling them to be positioned together at the bridge or between two tooth stumps being spanned by the bridge. In the operating position the motion of the jaws can be restricted or blocked by a screw. One of the jaws has a perforation that a conventional crown remover, especially one in the known shape of a shepherd's crook, can be inserted into. Attempts can then be made to remove the crown, bridge, or similar structure by hammering on the other end of the crook. This device is practically impossible to use in the distal area of the rows of teeth due to its overall height. It also demands considerable skill to use. Even so, there is still a danger that the applied force will not be exerted on the bridge in opposition to the direction of inser
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Fogiel Max
Wilson John J.
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