Dental implant thread
A dental implant includes a threaded portion extending along a central longitudinal axis from an apical end to a coronal end. The threaded portion includes a core from which threading extends radially outwards, the threading including an apical flank, a coronal flank and a lateral surface connecting the apical and coronal flanks, the lateral surface defining the radially outermost surface of the threading. The threading extends along the length of the threaded portion in a helical manner and the thread width narrowing in the radially outwards direction such that the threading is widest where it contacts the core and narrows towards the lateral surface. The core diameter of the threaded portion is defined by the outer diameter of the core and the outer diameter of the threaded portion is defined by the lateral surface of the threading.
1 . A dental implant comprising
a threaded portion extending along a central longitudinal axis from an apical end to a coronal end,
the threaded portion comprising a core from which threading extends radially outwards,
the threading comprising an apical flank, a coronal flank and a lateral surface connecting the apical and coronal flanks, the lateral surface defining the radially outermost surface of the threading, the threading extending along a length of the threaded portion in a helical manner and a thread width narrowing in the radially outwards direction such that the threading is widest where it contacts the core and narrows towards the lateral surface,
a core diameter of the threaded portion being defined by an outer diameter of the core and an outer diameter of the threaded portion being defined by the lateral surface of the threading,
wherein:
over at least a section of an axial extent of the threaded portion, a thread profile of the apical and coronal flanks of the threading is formed of exactly three sub-segments arranged sequentially in the radial direction, the sub-segments comprising a middle sub-segment, a radially innermost sub-segment, and a radially outermost sub-segment,
in each sub-segment, the apical and coronal flanks taper towards one another at a constant angle, the middle sub-segment having a taper angle that is greater than the taper angles of the radially innermost and radially outermost sub-segments, the taper angle formed between the apical and coronal flanks in the radially outermost sub-segment being less than 30°, and
the thread width at the core is constant along a full axial extent of the threaded portion, the thread width being a linear distance measured between the coronal flank and the apical flank, the thread depth along said threaded portion changes, resulting in changes in a width of the lateral surface, and the thread depth is a dimension of the threading extending from the core to the lateral surface and is transverse to the width of the lateral surface.
2 . The dental implant as claimed in claim 1 , wherein the core diameter of the threaded portion tapers radially inwards in the apical direction over the full axial extent of the threaded portion.
3 . The dental implant as claimed in claim 1 , wherein the outer diameter of the threaded portion tapers radially inwards in the apical direction within at least an apical half of the threaded portion along the central longitudinal axis.
4 . The dental implant as claimed in claim 3 , wherein:
the threaded portion comprises an apical section and a main body section,
within the apical section, the taper angle of the outer diameter of the threaded portion, relative to the central longitudinal axis, is always greater than 20°, the taper angle of the core diameter relative to the central longitudinal axis being less than the taper angle of the outer diameter at all axial locations of the apical section, such that a thread depth in the apical section continuously decreases in an apical direction, the apical section having an axial length of less than 2 mm, and
within the main body section, the taper angle of the outer diameter of the threaded portion, relative to the central longitudinal axis, is always less than 5°.
5 . The dental implant as claimed in claim 4 , wherein within the main body section, the width of the lateral surface of the threading is never less than 0.08 mm and never greater than 0.45 mm.
6 . The dental implant as claimed in claim 4 , wherein the thread profile of the threading is formed by said three sub-segments over at least one quarter of the axial extent of the main body section.
7 . The dental implant as claimed in claim 4 , wherein the thread profile of the threading is formed by said three sub-segments at an axial location within an apical most half of the main body section along the central longitudinal axis.
8 . The dental implant as claimed in claim 4 , wherein the taper angle of the outer diameter of the threaded portion in the main body section is always less than 2.5°.
9 . The dental implant as claimed in claim 4 , wherein the outer diameter of the threaded portion tapers radially inwards over at least the apical half of the main body section along the central longitudinal axis.
10 . The dental implant as claimed in claim 5 , wherein the main body section comprises an apical segment, in which the outer diameter of the threaded portion tapers radially inward in the apical direction, and a coronal segment, in which the outer diameter of the threaded portion has a taper angle of 0° and thus defines a cylindrical surface.
11 . The dental implant as claimed in claim 5 , wherein within the main body section, the core comprises at least two adjacent segments, the core diameter of each segment tapering at a different angle relative to the central longitudinal axis of the threaded portion.
12 . The dental implant as claimed in claim 4 , wherein in the main body section at every axial location, the taper angle of the core diameter is greater than the taper angle of the outer diameter of the threaded portion, such that the thread depth in the main body section continuously increases in the apical direction and a width of the lateral surface continuously increases in the coronal direction.
13 . The dental implant as claimed in claim 1 , wherein the angle between the apical and coronal flanks in the radially outermost sub-segment is between 20° and 29°.
14 . The dental implant as claimed in claim 1 , wherein the taper angle of the middle sub-segment is at least twice the taper angle of the radially outermost sub-segment.
15 . The dental implant as claimed in claim 1 , wherein the taper angles of the radially inner and outermost sub-segments are substantially the same.
16 . The dental implant as claimed in claim 1 , wherein the thread profile of the threading is formed by said three sub-segments over at least one quarter of the axial extent of the threaded portion.
17 . The dental implant as claimed in claim 1 , wherein the thread profile of the threading is formed by said three sub-segments at an axial location within an apical most half of the threaded portion along the central longitudinal axis.
18 . The dental implant as claimed in claim 1 , wherein the threading comprises a double start thread.
19 . The dental implant as claimed in claim 1 , wherein the threaded portion comprises, at its coronal end, a thread run out section in which the outer diameter of the threaded portion tapers radially inwards in the coronal direction such that, at the coronal end of the run out section, the outer diameter of the threaded portion is equal to the core diameter.
20 . The dental implant as claimed in claim 1 , wherein the threaded portion comprises at least two flutes which extend in a helical manner along the full axial extent of the threaded portion.
21 . The dental implant as claimed in claim 20 , wherein the cross-section of the flutes within the threading, in a plane perpendicular to the central longitudinal axis, comprises a circular arc and two opposing straight sections located adjacent to the radially outer ends of the circular arc, said straight sections tapering towards one another in the radially outwards direction.
22 . The dental implant as claimed in claim 21 , wherein the threaded portion comprises an apical section and a main body section, and said straight sections are present in the threading over 15-100% of an axial length of the main body section along the central longitudinal axis.
23 . The dental implant as claimed in claim 21 , wherein the cross-section of the flutes further comprises adjacent each straight section, transition surfaces which connect the radially outer ends of the straight sections to the lateral surface of the threading, the lateral surface of the threading having a greater radius than the outer end of the straight sections such that the leading cutting edge of the flute is located radially inward of the lateral surface.
24 . The dental implant as claimed in claim 1 , further comprising a neck portion coronal of the threaded portion, the neck portion being circular cylindrical with an external diameter which is less than the maximum outer diameter of the threaded portion.
25 . The dental implant as claimed in claim 1 , further comprising, coronal of the threaded portion, a head portion arranged to extend, in use, into the soft tissue of a patient.
26 . The dental implant as claimed in claim 25 , wherein the head portion comprises a flared out section which extends radially outward in the coronal direction, wherein the diameter of the coronal end of the flared out section is greater than the maximum outer diameter of the threaded portion.
27 . A plurality of the dental implants as claimed in claim 1 , at least two of the plurality of implants having different maximum outer diameters of the threaded portion, within the range from 3 mm-8 mm, and at least two of the plurality of implants having different axial lengths, within the range from 5 mm to 25 mm.
28 . The plurality of implants as claimed in claim 27 , wherein a pitch of the threading of the threaded portion of each implant varies depending on the maximum outer diameter and axial length of the implant, wherein for a given maximum outer diameter of threaded portion, the pitch of the threading in the threaded portion increases with the axial length of the threaded portion and for a given length of threaded portion, the pitch of the threading in the threaded portion increases with the maximum outer diameter of the threaded portion.