The invention relates to implements or instruments for extracting bridges, crowns and/or other dental restorations or prostheses from the mouths of dental patients.
Extraction of bridges, crowns and similar prostheses is a task which must be carried out by a physician or by a skilled technician. The implements which are presently available for the performance of such tasks are not entirely satisfactory. As a rule, a presently known implement includes or constitutes a hook which is caused to engage the edge bounding an opening of the bridge or crown adjacent the gums of the wearer, and the implement is thereupon pulled, either steadily or in stages or steps, in a direction to lift the crown or the bridge off the material which bonds the prosthesis to the tooth or teeth of the patient. The crowns or bridges are normally made of a metallic material or a metal-ceramic compound. Removal of such prostheses is necessary in the event of damage, excessive wear, inflammation or infection of the gums or teeth and/or damage to the material which bonds the prosthesis to the tooth or teeth.
A drawback of an implement which employs or constitutes a hook is that it is highly likely to damage the gums of and to cause great discomfort to the wearer of a prosthesis. Moreover, and since the wall of a crown or bridge is normally extremely thin (as a rule, the thickness is in the range of 0.2 mm), the hook is likely to damage the edge which is engaged thereby and which is acted upon by the hook during separation of the prosthesis from the bonding material within and/or around it. Still further, the hook is highly likely to tilt the prosthesis and to thus cause even more damage as well as to encounter greater resistance as the extracting operation proceeds. Such tilting causes extensive damage to the tooth or teeth and to the bonding material between the tooth or teeth and the prosthesis. The situation is not changed if the extraction takes place in stages, e.g., by resorting to a hammer which repeatedly strikes an anvil at that end of the handle for the hook which is remote from the prosthesis. Injury to the gums as a result of engagement of a hook with the edge of a bridge or crown can cause inflammation or infection which must heal before the removed prosthesis or a fresh prosthesis can be inserted into the mouth.
Any, even slight, damage to a crown or bridge during extraction must be attended to subsequent to extraction at a considerable cost. The damage arises not only at the edge which is engaged by the hook but also at the ceramic coating (if any), and additional damage is observable on the bonding material.
German Utility Model No. G 88 108 805.8 of (published Dec. 1988) discloses a looped wire the ends of which are held in a housing and which is to be placed around a connection between two joined crowns of a bridge. The housing carries a guide for a reciprocable hammer which is caused to repeatedly strike an anvil in order to loosen the bridge preparatory to complete extraction from the mouth of a wearer. The implement of the German Utility Model exhibits the drawback that it is difficult to secure the looped wire to the housing subsequent to placing of the wire around the connection between two crowns of a bridge.
USPTO Backgrounds
USPTO Backgrounds