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Title: Method for preparation of dental crowns and bridges
Claims: What I claim is: 1. A method of preparing a natural tooth for the fitting of a dental crown or bridge with the use of a rotatable cutting burr supported in a handpiece and having a shading guide coextensive with, and rotatable about, said cutting burr and extending beyond the tip of said cutting burr for engagement sub-gingivally with said tooth, wherein the steps comprise fastening a block by its base, to the cusp of said tooth, said block having three pre-prepared external surfaces, a first one of said surfaces constituting said base, a second one of said surfaces being at an opposite part of said block to said base, and a third one of said surfaces being an external wall joining said first and said second surfaces; and operating said handpiece to effect progressive free-hand reduction of the tooth structure of said natural tooth until said handpiece abuts both of said second and third surfaces simultaneously with said extending part of said shading guide in contact with a sub-gingival part of said tooth thereby to provide controlled limits of said reduction. 2. The method of claim 1 comprising, before fastening of said block to said tooth, the further steps of forming means in said tooth to key said block thereto, and thereafter making an impression of the patient's jaw including at least said tooth. 3. The method of claim 1, wherein in operating said handpiece the part of said handpiece abutting said second and third surfaces is a follower fixed to said shading guide and rotatable about the axis of said cutting burr. 4. A method of producing a guide block for use in preparing a natural tooth for the fitting of a dental crown or bridge, wherein the steps comprise producing a cast from an impression of the natural tooth, creating on said cast with the use of a dental surveyor a model of the intended preparation of the natural tooth which includes a sub-gingival shoulder, temporarily attaching to the cusp of the model tooth so formed a mass of material having bottom and top surfaces and an outer face, so that said bottom surface contains an impression of the configuration of said cusp, preparing said outer face of said mass to form a side wall surface with the occlusal area of the model tooth serving as a guide, and forming said top surface on said mass corresponding contoured and parallel to a predetermined sub-gingival shoulder of the model tooth, thereby creating from said mass a block having three prepared external surfaces of which two serve as controlling limits on free-hand reduction of the natural tooth by a dental surgeon, and thence removing said block from said model tooth for supply as an aid to the dental surgeon. 5. The method of claim 4, wherein the step of preparing said side wall surface of said mass includes cutting with a cutting burr until a part of said burr maintains contact with said occlusal area of the model tooth during a full rotation of said burr around said model tooth. 6. The method of claim 4, wherein the step of forming said outer end surface on said mass includes scribing around said side wall surface of said mass a line which is parallel to said sub-gingival shoulder, cutting off the outer end of said mass beyond said line, and forming a recess in the top of said block so formed. Other info: Inventors: Marshall, Kenneth H. (Castlecrag, AU) Application Number: 744464 Filing Date: 1976-11-24 Publication_date: 1979-03-20 Assignee: Premach Pty. Limited (Sydney, AU) Primary Class(es): 433/223 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Kinsey, Russell R. Assistant Examiner: Wilson, John J. Attorney: Finnegan, Henderson, Farabow & Garrett |
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