Screw head

{
  "publication_number": "US2012164600A1",
  "country": "US",
  "kind": "A1",
  "title": "Screw head",
  "abstract": "Fastening system including a screw component (10) and a seating component (20). The screw component having a shaft (12) of maximum radius R 1, a threaded section (13), and a head (14) having a bottom end (15) having a larger maximum radius R 2 than the screw shaft such that an exposed underside (18) of the screw head extends radially beyond the maximum radius of the screw shaft. The system further includes a seating component with a screw channel (21) and a planar screw seat (22) having a minimum radius R 3 which is equal to or greater than R 1. The bottom end of the screw head has an annular contact surface for abutment against the screw seat, the contact surface being formed by the distal end of at least one downwardly extending protrusion (17) on the underside of the screw head, wherein the annular contact surface has a minimum radius greater than the minimum radius of the screw seat.",
  "claims": [
    "1. A fastening system comprising a screw component and a seating component, the screw component comprising a shaft extending along a longitudinal axis and having a maximum radius R 1, said shaft comprising a threaded section, said screw component further comprising, at one end of the screw shaft, a head, the head comprising a bottom end having a larger maximum radius R 2 than the screw shaft such that an exposed underside of the screw head extends radially beyond the maximum radius of the screw shaft, the seating component comprising a screw channel comprising a planar screw seat having a minimum radius R 3, which is equal to or greater than R 1, wherein the bottom end of the screw head comprises an annular contact surface (C) for abutment against said screw seat, said contact surface being formed by the distal end of at least one downwardly extending protrusion on the underside of the screw head, the annular contact surface having a minimum radius greater than the minimum radius of the screw seat. 2. A fastening system as claimed in claim 1, wherein the annular contact surface (C) is formed by a single protrusion extending 360° about the longitudinal axis. 3. A fastening system as claimed in claim 1, wherein the annular contact surface (C) has a uniform inner radius. 4. A fastening system as claimed in claim 1, wherein the annular contact surface (C) is located in the outer half of the underside of the screw head. 5. A fastening system as claimed in claim 1, wherein the minimum radius of the annular contact surface (C) is at least 25% greater than the minimum radius R 3 of the screw seat. 6. A fastening system as claimed in claim 5, wherein the contact surface (C) is located within a range of 128-140% of the minimum radius R 3 of the screw seat. 7. A fastening system as claimed in claim 1, wherein minimum radius of the annular contact surface (C) is at least 30% greater than the maximum radius R 1 of the screw shaft. 8. A fastening system as claimed in claim 1, wherein the one or more protrusion comprises a flat distal end. 9. A fastening system as claimed in claim 1, wherein the one or more protrusion is tapered at least on its radially inner side. 10. A fastening system comprising a screw component and a seating component, the screw component comprising a shaft (12) extending along a longitudinal axis and having a maximum radius R 1, said shaft comprising a threaded section, said screw component further comprising, at one end of the screw shaft, a head, said head comprising a bottom end having a larger maximum radius R 2 than the screw shaft such that an exposed underside of the screw head extends radially beyond the maximum radius of the screw shaft, the seating component comprising a screw channel comprising a planar screw seat having a minimum radius R 3 equal to or greater than R 1, said bottom end of the screw head comprising an annular contact surface (C) for abutment against the planar screw seat, said annular contact surface being formed by the distal end of at least one downwardly extending protrusion on the underside of the screw head, said at least one downwardly extending protrusion being tapered at least on its radially inner side. 11. A fastening system as claimed in claim 9, wherein the radially inner side of the one or more protrusion tapers downwards at an angle of between 15 and 25°, most preferably 20°. 12. A fastening system as claimed in claim 9, wherein the taper is at least partially curved over a radius. 13. A fastening system as claimed in claim 9 wherein the screw component comprises an undercut at the transition between the screw shaft and the screw head, such that the taper starts radially inwards of R 1. 14. A fastening system as claimed in claim 12 wherein the screw component comprises an undercut at the transition between the screw shaft and the screw head, wherein the curve of the taper continues into and forms at least part of the undercut. 15. A fastening system as claimed in claim 1, wherein the screw component is a dental screw for attaching an abutment or other secondary component to a dental implant. 16. A screw component for use in the fastening system as claimed in claim 1. 17. A screw component comprising a shaft extending along a longitudinal axis and having a maximum radius R 1, said shaft comprising a threaded section said screw component further comprising, at one end of the screw shaft, a head, said head comprising a bottom end having a larger maximum radius R 2 than the screw shaft such that an exposed underside of the screw head extends radially beyond the maximum radius of the screw shaft, said bottom end comprising an annular contact surface (C) for abutment against a planar screw seat, said contact surface being formed by the distal end of at least one downwardly extending protrusion on the underside of the screw, said contact surface having a minimum radius greater than the maximum radius of the screw shaft. 18. A screw component as claimed in claim 17, wherein the minimum radius of the annular contact surface (C) is at least 30% greater than the maximum radius R 1 of the screw shaft."
  ],
  "description_excerpt": "This invention relates to screws, particularly those used in the dental implant field to attach secondary components, such as abutments, to a dental implant. Dental implants are used to replace individual teeth or for anchoring more complex structures, which generally replace several or even all of the teeth. Implants are often constructed in two parts, in which case they consist of an anchoring part, often referred to in isolation as the implant, and of a separate abutment. The anchoring part is either embedded completely in the bone, that is to say to the height of the alveolar crest, or protrudes by a few millimetres from the alveolar crest into the soft tissue. The abutment is mounted on the anchoring part and extends into the oral cavity to form a support for a dental prosthesis or denture. During the lifetime of the prosthesis, which can be over 20 years, the implant system will be subjected to large loads caused by mastication. The abutment must therefore be firmly fastened to the implant in order to prevent loosening and potential loss of the component. This can be achieved in numerous ways, for example, via compression fit or gluing. However, screw fit connections are generally preferred. By applying a sufficiently high torque during attachment a firm connection between the implant and abutment can be achieved.\n\nIn many systems therefore the implant comprises an internal threaded bore, while the abutment comprises a corresponding apical thread, thus allowing the abutment to be screwed directly into the implant.",
  "cpc": [
    "A61C 8/0068",
    "A61C 8/005",
    "A61C 8/0059",
    "A61C 8/0069",
    "A61C 8/0074",
    "F16B 31/00",
    "F16B 35/06"
  ],
  "ipc": [
    "A61C 8/00"
  ],
  "assignees": [
    "COURVOISIER STEPHANE",
    "STRAUMANN HOLDING AG"
  ],
  "inventors": [
    "COURVOISIER STEPHANE"
  ],
  "filing_date": "2011-11-25",
  "publication_date": "2012-06-28",
  "priority_date": "2010-12-23",
  "application_number": "US-201113304552-A",
  "family_id": "43919770",
  "citations": [
    "US2005042573A1",
    "US2006216672A1",
    "US6332778B1",
    "WO2011017733A1"
  ]
}