Abstract:
An o-ring attachment system with opposed convex circumferential surfaces for removable dentures to be attached to a natural or an implanted fixed root system. The o-ring attachment system can be screwed into an implanted root using a manipulating means interposed between o-ring abutment and an attachment screw. In connection therewith, a tool is provided for implanting the o-ring attachment system, the tool having a captured toroidal spring for gripping the attachment system.

Description:
FIELD OF INVENTION 
     My invention relates to removable dentures attached to a natural or an implanted fixed root system. Specifically, I have invented an o-ring attachment system with opposed convex circumferential surfaces to reduce implantation stresses in an o-ring. I have also invented an o-ring attachment system which can be screwed into an implanted root using manipulating means interposed between an o-ring abutment and an attachment screw. In connection therewith, I have invented a tool for implanting the o-ring attachment system. 
     BACKGROUND OF THE INVENTION 
     Artificial teeth and dentures are frequently secured to a patient&#39;s jaw with apparatus which permits dentures to be removed. Some of these apparatus comprise o-rings for attaching a removable denture to a natural or an implanted fixed root system. Such an apparatus is disclosed, for example, in U.S. Pat. No. 4,193,194 to Dalise. An another apparatus is disclosed in U.S. Pat. No. 4,681,542 to Baum. In both of these systems an o-ring is introduced into a concave retainer cavity. The concave surfaces in the retainer cavity form a relatively sharp edge between the cavity and the rest of an o-ring abutment. Since it is contemplated that the denture may be attched and removed multiple times, excess stress and unwanted wear may be produced in the o-ring as the denture is either attached or removed. 
     SUMMARY OF MY INVENTION 
     I have invented an o-ring attachment system for dental prostheses having an o-ring abutment formed with convex surfaces. Convex abutment surfaces allow one to place an o-ring on the abutment with less potential damage to the o-ring. Because of the convex surfaces, when the o-ring is distended as it is placed on the abutment, the slope of the adjacent surface of the abutment is small relative to the direction of motion of the o-ring and the o-ring can be placed on the abutment more easily. On the other hand, when the o-ring is seated on the abutment, the adjacent surfaces have a relatively steep slope and the o-ring is securely placed on the abutment. 
     I have also invented an apparatus for implanting the abutment onto an implanted root or other structure. My implantation apparatus comprises manipulating means, preferably a male hexagonal section, interposed between the o-ring abutment and a screw. I have invented a seating tool having a captured toroidal spring for driving the o-ring abutment into the implanted root. The seating tool has a female hexagonal segment which is held against the male hexagonal segment when the toroidal spring engages the o-ring abutment. 
     It is an object of my invention, to provide an o-ring attachment system which reduces undesirable wear and stresses in an o-ring during attachment or removal of a dental prosthesis or denture. 
     Another object of my invention is to provide such an o-ring attachment system having convex surfaces on an o-ring abutment. 
     It also an object of my invention to provide an o-ring attachment system with means for manipulating the o-ring abutment, the manipulating means comprising the male hexagonal segment interposed between the o-ring abutment and a screw. It is also an object of my invention to provide an apparatus for manipulating the o-ring abutment which can be sterilized. 
     A further object of my invention is to provide the manipulating means having means adapted to co-operate with the seating means on the o-ring abutment and a toroidal metal spring for engaging the o-ring abutment in lieu of the elastomeric o-ring. 
     These and other objects of my invention will be apparent from the following description taken with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an o-ring attachment system according to my present invention. 
     FIG. 2 is plan view and partial through-section of the o-ring attachment system taken along line 2--2 of FIG. 1. 
     FIG. 3 is a perspective view of a seating tool for use with the attachment system of FIG. 1. 
     FIG. 4 is an inverted perspective view of the tool of FIG. 3. 
     FIG. 5 is a through-section of the seating tool taken along line 5--5 of FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     I will now describe my preferred embodiment of my invention by reference to the accompanying drawings. Like numerals designate like parts in each of the figures. 
     FIG. 1 illustrates an o-ring attachment system, generally designated 10, according to my present invention. The attachment system comprises an implanted root 12, an o-ring abutment or post 14, an elastomeric o-ring 16, and a retainer 18. The root 12 can be securely implanted in a mandible of a patient, as is known in the art. After implantation of the root, a period for healing and incorporation of the root into the mandible structure may be needed. Thereafter, the o-ring abutment 14 can be attached to the root. I prefer to use a threaded screw 20, but other attachment mechanisms are known and can be employed in connection with my invention. In my invention, the o-ring abutment comprises a hemispherical base 22 and a spherical end 24 separated by a cylindrical spacer 26. The spherical end 24 and the hemispherical base 22 form opposing convex surfaces 28, 30, respectively, adapted to retain the elastomeric o-ring 16. The retainer 18 fits over the o-ring 16 and provides an attachment surface 32 which can be connected to a dental prosthesis or denture, as is known in the art. 
     The convex surfaces on the on-ring abutment or post permit one to place the o-ring on the o-ring abutment without excessive stress or wear in the o-ring. The o-ring can also be removed from the abutment in a similar fashion. As the o-ring 16 passes over the spherical end 24 it will be stretched. As the distention of the o-ring increases, the slope of the surface of the spherical end adjacent the o-ring decreases with reference to the direction of motion of the o-ring. The rate of distention of the o-ring is, consequently, relatively reduced and there are no abrupt changes in stress or relatively sharp edges which might damage the o-ring, reducing its structural integrity. When the o-ring is seated on the o-ring abutment and adjacent the cylindrical spacer, the surfaces of the spherical end and the hemispherical base present relatively steep angles to axial motion of the o-ring. Consequently, the o-ring attachment system can secure the dental prosthesis from undesirable removal. 
     In my preferred embodiment, the implanted root 12 comprises a cylinder 34 having a hemispherical tip 36. As is known in the art, attachment of the root 12 to the bone of the mandible can be promoted by a coating of hydroxyapatite. Through bores 38, 40 can be provided for additional bony ingrowth. A threaded bore 42 is provided to receive the threaded screw 20 of the o-ring abutment. 
     The threaded screw 20, comprises a threaded shank 44 and a tapered seat 46 so that the abutment 14 can be tightly attached or screwed into the root 12. Between the hemispherical base 22 and the tapered seat 46, I have placed a male hexagonal section 48 for screwing the abutment into the root. A seating tool, which I will describe hereafter, grips the o-ring abutment and engages the male hexagonal section. 
     After the o-ring abutment is attached to the root, the o-ring 16 can be placed on the abutment. Alternatively, the o-ring may be placed in the retainer 18 which should already be encased within the denture or dental prosthesis and the assembly of the denture, retainer and o-ring can be placed on the abutment as a single unit. 
     In my referred embodiment, the retainer 18 comprises a ring 50 with a concave grove 52 on the inside thereof. Interior upper and lower edges 54,56 respectively, should be rounded to minimize or prevent damage to the o-ring. An outer surface 58 of the retainer may be textured to enhance mechanical coupling between the denture and the retainer. 
     To install the o-ring abutment 14 on the implanted root 12, I have invented a seating tool 60 shown in exploded perspective view in FIG. 3. The seating tool 60 comprises a knurled handle 62 with a shaft 64. A distal end 66 of the shaft 64 has a smaller diameter to receive a sleeve 68. As can be seen in FIG. 4, there is a counter bore 70 in a distal end 72 of the shaft 64. A toroidal coil spring 74 is placed against the distal end 72 of the shaft. The toroidal spring acts like the elastomeric o-ring and can grip the o-ring abutment near the cylindrical spacer 26 to hold the o-ring abutment in the seating tool 60. Because the toroidal spring is metal, the tool can be sterilized in an autoclave. Moreover, the spring does not tend to weaken or degrade as an elastomeric o-ring might under repeated use. 
     With the spring 74 in place, the sleeve 68 is placed over the spring and press fit onto the shaft 64. The sleeve 68 has a hexagonal female bore 76 at a distal end 78 thereof. The hexagonal bore 76 is adapted to engage the male hexagonal section 48 on the o-ring abutment, so that the o-ring abutment can be screwed into the root 12. The sleeve 68 defines a partial bore 80 which encloses the spring 74 and into which the shaft 66 is pressed. This bore 80 should be slightly larger in diameter than the largest dimension of the hex bore 76 so that a lip 82 is formed which retains the spring 74 inside the sleeve 68. A distal end 84 of the sleeve is chamfered 86. 
     My invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is considered in all respects to be illustrative and not restrictive, the scope of my invention being indicated by the appended claims, rather than the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.