Measuring and testing – Instrument proving or calibrating – Dynamometer
Reexamination Certificate
1999-05-27
2001-03-27
Raevis, Robert (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Dynamometer
Reexamination Certificate
active
06205837
ABSTRACT:
The present invention relates to a novel support device and system for use in fabricating and supporting a dental prosthesis, and a novel method of installing the same into a patient, utilizing a previously implanted hollow implant device.
BACKGROUND INFORMATION
Implant systems consisting of an implant or root portion embedded in a patient's bone or tissue and a post or support device for receiving a prosthesis are widely used. They are used most often in implanting permanent teeth or crowns into the jawbones and surrounding tissue of patients.
Existing devices and methods often result in an incorrect fit of the prosthesis with the anchoring device and surrounding tissue. Another problem with certain previous systems was the inability to fabricate a closely fitting permanent prosthesis without time-consuming and unwieldy procedures such as removing and reassembling the components of the implant and post or fabricating a permanent prosthesis by taking laborious and often inaccurate measurements of a temporary cap after the implant, post and temporary cap had been installed in the patient.
Yet another problem in some implant devices was the tendency for the gum tissue (gingiva) to grow inward over the top of the implant before installation of the permanent prosthesis, so that the tissue had to be cut away from the top of the implant before a prosthesis could be secured to the implant or post, thus resulting in trauma to the patient and ultimately a poor fit between the implant, post and prosthesis. The poor fit also resulted in food particles becoming wedged between the prosthesis and the cap or implant, leading to decay.
Another problem with certain previous implants was the inability to keep a support post firmly anchored in a receiving device already implanted in the patient's bone without cross-threading or stripping either or both of the support post and receiving device.
Another problem with installing certain previous implant devices was the difficulty associated with calibrating and applying a correct amount of torque to the post so as to attach it firmly to the implant device, e.g., without rotating the implant device, and thus damaging or traumatizing the patient and surrounding bone and tissue.
Certain previous torque wrenches for use with dental implant devices depended on the user noticing when slippage of the wrench occurred against the prosthesis or post. Some previous torque wrenches had a linear scale along their body to indicate the torque value set, which was hard to read. In spring-based wrenches the torque indication became inaccurate as the spring constant of varied with use and/or metal fatigue. Utilizing other wrenches depended on the user's skill in noticing changes in the connection between the wrench and the implant or post. This resulted in stripping the screw threads inside the implant when the practitioner's judgment was flawed, or rotating the implant and causing patient trauma. In some designs, the wrench deformed when a predetermined torque was reached.
Many previous methods of calibrating a wrench to a specific torque relied upon a variable, spring-based standard. This method had at least two drawbacks: first, the torque amount varied as the spring experienced metal fatigue and/or eventual change in the spring constant, and second, the torque wrench typically could only be set infrequently. Many previous calibration devices for torque wrenches relied on complex machinery to calibrate a measuring device which in turn was itself used to calibrate a torque wrench, or alternatively relied on magnets to calibrate torque.
Accordingly, it would be advantageous to provide a device for implanting and securing prostheses which results in a precise degree of fit between the support device and the implant, the support device and the surrounding tissue, and the support device and the prosthesis. It would be advantageous to provide a method for installing the support device utilizing a non-spring based torque setting for a torque wrench for inserting the support device into the implant. It would also be advantageous to provide a device for fabricating a permanent prosthesis whose shape closely reproduced the support device for the prosthesis, so as to eliminate tedious measurements of the prosthesis in the patient's mouth, and provided for a more precise fit between the prosthesis and the support device.
SUMMARY OF THE INVENTION
A novel and useful invention relates to fabricating and/or installing a prosthesis into patients. The prosthesis is usually a temporary healing cap or permanent dental crown. A hollow receiving device or “implant” is implanted into a patient, usually into the patient's jaw bone (alveolar). A support device or “post” is fined into the implant and extends upwardly away from the jaw bone for receiving a healing cap and/or a permanent prosthesis.
In one embodiment, the support device has three portions, a distal root portion, a middle collar portion and an upper post portion. The distal root portion may additionally have external screw threads located above a smooth lower surface. The distal root portion extends into the implanted receiving device and is initially fitted into the receiving device by manually inserting the smooth end into the implanted receiving device. The smooth end functions as a lead so that the support device initially fits loosely in the implanted receiving device but is substantially axially aligned (e.g. to avoid cross-threading), awaiting tightening to a predetermined torque setting.
In one embodiment, various sizes of the middle collar portion are provided to accommodate different tissue thicknesses and/or prosthesis size.
In one embodiment, the top of the support portion of the post has a breakaway feature effected by a weakened (e.g.,, lesser diameter) section. In yet another embodiment, the topmost portion of the post has external threads which allow connection with a temporary healing cap. The healing cap may then be broken off prior to installation of the permanent prosthesis without damage to the rest of the post, implant, bone or tissue. Alternatively, the permanent prosthesis may be seated directly on the healing cap.
In one embodiment of the invention, the uppermost portion of the post is tapered to provide a secure fit with the prosthesis and lessen the possibility of splintering of the prosthesis.
In one embodiment, the external surface of the upper part of the support device has a hexagonal wrench-engaging surface. The surface may be used to fit the post into the implant with a torque wrench. The surface may be used by the practitioner to index the prosthesis to the post.
Another feature of the invention is the use of a replica of the post as a mold or analogue to fabricate a temporary healing cap or permanent prosthesis. This feature allows fabrication without dissembling and reassembling the post and/or implant from the patient's mouth and increases the degree of fit and compatibility between the prosthesis and post.
One embodiment of the invention utilizes a non-spring based torque wrench to install the support member. The wrench is set at a predetermined torque level using a non-spring, non-variable, weight-based calibration device and results in installation of the support device without rotation of the implant or damage to the surrounding tissue or bone.
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Hughes Richard L.
Raevis Robert
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