Source: http://www.google.com/patents/US5591029?dq=U.S.+Patent+
Timestamp: 2016-08-26 06:43:09
Document Index: 349815502

Matched Legal Cases: ['art 74', 'art 74', 'art 75', 'art 33', 'art 35', 'art 188']

Patent US5591029 - Dental implant system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA dental implant assembly is provided, as well as a system and method for exposing an embedded implant after osseointegration has taken place. The implant assembly comprises an implant member for embedding in the jaw and a rest factor member for securing to the implant member, the rest factor member...http://www.google.com/patents/US5591029?utm_source=gb-gplus-sharePatent US5591029 - Dental implant systemAdvanced Patent SearchPublication numberUS5591029 APublication typeGrantApplication numberUS 08/102,353Publication dateJan 7, 1997Filing dateAug 5, 1993Priority dateNov 14, 1989Fee statusPaidAlso published asDE69415240D1, DE69415240T2, EP0641549A2, EP0641549A3, EP0641549B1Publication number08102353, 102353, US 5591029 A, US 5591029A, US-A-5591029, US5591029 A, US5591029AInventorsMax ZuestOriginal AssigneeZest Anchors, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (29), Referenced by (90), Classifications (9), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetDental implant system
34. The assembly as claimed in claim 24, wherein the upper end portion of the implant member comprises an annular ring and an inwardly tapering rim projecting upwardly from the annular ring.
35. The assembly as claimed in claim 24, including a wrench element projecting from the upper end portion of said insert member for engagement with a tool for inserting the implant member, the wrench element having a bore aligned with the central bore of said insert member.
36. The assembly as claimed in claim 35, wherein the wrench element has a twelve-sided outer wrench engaging surface.
37. The assembly as claimed in claim 24, including a plurality of implant members in a range of different heights from 2 to 13 mm.
38. A dental implant assembly for embedding in the jawbone of patient, comprising:an implant member for embedding in and osseointegrating with the jawbone of a patient at a selected site; an attachment member for securing to the implant member after osseointegration; the implant member having an upper end portion with a central bore, the attachment member and central bore of the implant member having interengageable securing means for releasably securing the attachment member to the implant member, and a stem portion depending downwardly from the upper end portion for engagement with a recess in the jawbone of shape and dimensions matching those of the stem portion; the stem portion having an annular indent at its lower end; and the attachment member comprising a rest factor member having an upper rest surface for supporting, but not being connected to, overlying portions of a denture anchored elsewhere in the jaw, the rest factor member having an upper, dome-shaped portion and a downwardly depending stem portion for engagement in said implant member bore, the rest surface comprising the upper end of said dome-shaped portion. 39. The assembly as claimed in claim 38, including a plurality of rest factor members having dome-shaped portions of different heights in the range from 1.5 mm. to 3.5 mm.
40. The assembly as claimed in claim 39, in which said rest factor members have total heights in the range from 2 mm. to 4.5 mm.
41. The assembly as claimed in claim 38, wherein said dome-shaped portion has a hex indent at its upper end for engagement with a hex tool for insertion of the rest factor member into an implant member bore.
42. An implant member for embedding in a patient's jawbone for attachment to other dental devices, the member comprising:a generally cylindrical body having an upper end portion for projecting above the jawbone and a lower stem portion for insertion in a recess prepared in a patient's jawbone; the upper end portion having a central bore for insertion of a portion of a dental device to be attached to the implant member; and the lower end portion having an outer cylindrical surface and a plurality of multiple lead threads projecting outwardly from the outer surface. 43. The implant member as claimed in claim 42, wherein the upper end portion includes a cylindrical ring portion of diameter greater than said cylindrical surface of the lower end portion, and an inwardly tapered rim portion projecting upwardly from said ring portion.
44. The implant member as claimed in claim 43, wherein said ring portion has a diameter equal to the diameter of said threads.
45. The implant member as claimed in claim 43, wherein said upper end portion has a height less than that of the lower end portion.
This application is a Continuation-In-Part of application Ser. No. 07/861,183 filed Mar. 31, 1992, abandoned, which was a Continuation of application Ser. No. 07/751,661 filed Aug. 22, 1991, now U.S. Pat. No. 5,254,005, which was a Continuation of application Ser. No. 07/436,432 filed Nov. 14, 1989 (now abandoned).
According to a first aspect of the present invention, a dental implant assembly is provided which comprises a first, implant member for implanting in the distal region of the jaw bone, and a second member or rest factor for attachment to the implant member. The two members have cooperating releasable securing devices for releasably securing them together, preferably comprising a screw threaded bore in the implant member and a corresponding threaded portion on the rest factor member. The rest factor member projects up to just above the level of the tissue overlying the jaw bone and has an upper surface opposing an overlying portion of a prosthesis anchored elsewhere in the jaw to form a rest for the prosthesis which accepts down pressure only, and which acts as a support to prevent or restrict bone erosion. The implant member has a selected height less than the depth of the mandibular nerve at the implant site, so that it can be embedded in the bone without risk of interference with the nerve. At the same time, the implant member is as wide as possible, and preferably has the maximum diameter possible according to the width of the patient's alveolar ridge at the implant site. The implant member diameter is preferably selected to be 1 mm less than the available alveolar ridge or bone width at the implant site. Implant members in a range of different heights and diameters are preferably provided to meet the requirements of a range of patients. Preferably, implant members with heights of 2 mm, 4.5 mm, 7 mm and 10 mm are provided, to allow for patients whose jawbone is already eroded to some extent. Implant members with diameters ranging from about 4 mm to 6 mm may be provided.
Since the implant member is of relatively large diameter, it has a relatively large surface area resisting downward forces. In a preferred embodiment of the invention, the implant member has a generally cylindrical body with an upper end portion and downwardly depending stem portion which engages in a corresponding recess drilled out in the bone. Preferably, at least part of the stem portion at the lower end of the implant member has an annular recess forming an outer rim and central boss. This engages a corresponding annular recess drilled out in the bone to resist sideways movement of the implant. This will resist sideways movement of the implant during osseointegration, and also provides additional depth for securing the rest factor to the implant member. A bore of corresponding shape to the undersurface of the implant member is drilled out in the jawbone at the implant site, so that when the implant member is positioned in the bore, the peripheral rim will provide stabilization of the member against lateral movement during the osseointegration period. The shape of the undersurface of the implant provides a large area of bone to implant contact for osseointegration, and significant resistance to both lateral and downward forces both during and after the osseointegration period. Preferably, at least two separate or double lead threads are provided, and triple or quadruple threads may be provided for added retention. Bone grows into the gaps between threads.
The outer surface of the stem portion of the implant preferably has threads to provide additional surface area for bone attachment. Bone grows into the area above and below the threads to resist loosening of the implant.
The implant system and method described above provides a rest surface for an overlying cantilevered bridge or denture which is anchored elsewhere in the jaw, on which the denture can rest and which accepts down pressure from the denture, reducing tissue trauma. Rest surfaces may be provided wherever needed, in conjunction with the conventional implants and anchors used for securing the denture or prosthesis in the jaw. The improved implant recovery tool and method produces minimal trauma when exposing a previously embedded implant for subsequent connection to either a rest factor or to a conventional anchor or magnet abutment.
FIG. 1 is a perspective view of the separated implant and healing screw components of an implant assembly according to a preferred embodiment of the invention;
FIG. 7 is a similar view illustrating the final counter-boring operation for an implant;
FIG. 17 is a similar view illustrating the finishing step in the boring operation;
FIG. 18 is a similar view illustrating the implant and healing screw in place and enclosed under tissue for the osseointegration period;
FIG. 19 is a perspective view of a rest factor according to another embodiment of the invention;
FIG. 20 is a perspective view, partially cut away, of one example of an implant for the rest factor of FIG. 19;
FIG. 21 is a side elevation view, partially cut away, of another implant with triple retaining threads;
FIG. 22 is a side elevation view of a further implant with quadruple threads;
FIG. 23 is a top plan view of FIG. 20;
FIG. 24 is a view similar to FIG. 7, showing the addition of a shallow counter-bore;
FIG. 25 is a similar view showing the cutting of threads to receive an implant;
FIG. 26 is a similar view showing insertion of the implant;
FIG. 27 is a similar view showing attachment of the rest factor;
FIG. 28 is a side elevation view, partially cut away, of another modified implant having an alternative wrench element; and
FIG. 29 is a top plan view of the implant of FIG. 28.
FIGS. 1--3 and 5 of the drawings illustrate an implant assembly 10 according to a preferred embodiment of the present invention, as well as a preferred method of installing the assembly in the jaw. As best illustrated in FIG. 5, the implant assembly 10 basically comprises an implant 12 for insertion into a suitably prepared bore 14 in the jawbone 16, where it is secured in place by osseointegration as is known in the field of implant dentistry, and an extension member or rest factor 18 secured to the implant 12 and extending up to slightly above the level 20 of the tissue or gum 21 to form a rest surface 22 for an overlying denture or bridge 24 which is anchored elsewhere in the jaw.
As best illustrated in FIGS. 1 and 3, implant 12 comprises a thin, annular member 26 having a central spigot or downward extension 28 projecting from one of its faces and an annular peripheral rim 30 projecting from the same face. A central bore 32 extends from the opposite face into the spigot 28, as illustrated in FIG. 4. The bore 32 has a larger diameter upper portion 33 having internal screw threads 34 extending along its length with a taper 37 at its upper end for added strength to hold the threaded engagement. The lower end of bore 32 comprises a smaller diameter lower portion 35 extending into spigot 28 for centering parts mating with implant 12 and preventing cross-threading of the threaded engagement. The implant will be of metal or any suitably rigid material as is normally used for dental implants, for example surgical titanium alloy. The implant may have spaced, short grooves or indents 29 on its outer surface for resisting rotation. These are preferably of the order of 1 mm in length.
Also illustrated in FIG. 1 is a healing screw 70 for insertion in the implant member during the osseointegration process. Healing screw 70 has a relatively short head portion 72 and downwardly depending shaft portion 73 for engagement in the bore 32 of implant 12. Portion 73 has a screw threaded larger diameter upper part 74 for threaded engagement in bore portion 33, the upper part 74 having a taper 71 at its upper end matching the taper 37 at the upper end of the implant bore 32 for support and seating of the screw 70 in bore 32. The lower end of portion 73 comprises a smaller diameter, cylindrical lower part 75 for fitting into lower portion 35. The upper end face of the head portion has a central, tool receiving bore 76 for receiving the end of a suitable tool for inserting the arrangement in the bore in the jawbone, and for subsequently receiving the end of a locating or removing tool as will be explained in more detail below. If desired, the upper end face of screw 70 may have a concave or dish-shaped depression 79 surrounding bore 76. The bore corresponding to bore 76 is illustrated in FIG. 11 and has a screw threaded upper portion 77 and a downwardly depending cylindrical centering extension 76 corresponding to extension 75 in FIG. 1. The threads in upper portion 77 are of opposite hand to those of screw threaded portion 74. In the embodiment illustrated in the drawings, portion 74 has a right hand thread while portion 77 has a left hand thread. The healing screw may be provided in a range of sizes, but in each case the height of the head portion is of the order of 1 mm or less.
The extension or rest factor member 18 as it appears prior to installation in the jaw is illustrated in FIG. 2. The member comprises a generally cylindrical boss 36 having a projecting shaft 38 at one end dimensioned for mating engagement in the bore 32 of implant 12. Shaft 38 has an upper, larger diameter portion 39 having external screw threads for threaded engagement with the internal screw threads 34 in the upper part 33 of bore 32, and a lower, smaller diameter cylindrical extension 40 for fitting into the lower part 35 of bore 32, as illustrated in FIG. 11. The upper end of shaft 38 has a taper 41 matching the taper 37 at the upper end of the implant bore 32. Member 18 has a curved, slightly convex rest or support surface 42 at its upper end, and an external hex formation 43 for securing it to a suitable tool for insertion into the implant. The member 18 will also be of a suitable dental material such as titanium alloy.
Member 18 may alternatively be formed with a concave support surface (not illustrated), or with any suitably shaped upper rest or support surface. Member 18 will be made in a range of heights to allow the dentist to select the appropriate size rest factor for a particular patient's tissue level. The rest factor is selected to project only to a distance of the order of 1/2 to 1 mm above the tissue level when installed in the jaw, and is preferably kept as low as possible so that it acts to accept biting pressures but will not interfere with normal jaw motions.
The implant assembly with the rest surface 42 is used to form a rest or support surface in implant dentistry for a prosthesis anchored elsewhere in the jaw, for example, as illustrated in FIGS. 12 and 13. The implant assembly is designed to be relatively short or thin so that it can be installed in distal jaw regions to the rear of line 160 in FIGS. 12 and 13, which extends between the first and second bicuspids 161 and 162 and corresponds to the approximate location where the mandibular nerve 163 exits the jawbone. The mandibular nerve extends through the jawbone to the rear of the first bicuspid, making the installation of long implants in this region difficult or impossible without the assistance of a dental surgeon. Thus, unsecured dentures are common, resulting in bone erosion from biting impacts. This rest factor assembly avoids or reduces such problems. The implant has a relatively large diameter as compared to its height, providing good implant to bone contact and integration, while having only a short penetration into the jawbone. In the preferred embodiment illustrated, the penetration into jawbone is only between 2 to 4.5 mm, depending on the patient's bone depth, and there is thus no risk of interference with the mandibular nerve.
FIGS. 12 and 13 illustrate the assembly implanted in the jaw for cooperation with an overlying denture anchored elsewhere. In FIGS. 12 and 13, a full denture or prosthesis 164 is illustrated, secured to a patient's lower jaw 165 via a pair of anchors 166, 167 mounted in the anterior regions of the patient's jaw, and seated on implanted rest factors 168, 170 in the posterior or distal jaw region below the former second molar at each end of the denture. In practice, the rest factor assembly may be installed anywhere between the region corresponding to the former second molar (line 171) and the first bicuspid (line 160). The area to the rear of the line 171 has too many muscles for insertion of an implant. As illustrated in FIG. 13, the rest factors may be provided or preformed with a slightly convex or ball-shaped head 42 which projects from around 1/2 to 1 mm above the tissue level, although support surfaces of a different shape may be provided. The prosthesis or denture is preferably provided with a corresponding concave surface or depression for seating on the opposing rest factors or surfaces 168 and 170.
Most typical denture anchors allow a limited degree of pivoting or side-to-side motions of the denture with jaw motions so as to reduce stress in the jaw bone areas to which the denture is positively anchored. With relatively long partial or full dentures which extend into the posterior jaw regions, tilting or rotation of the denture about the anchor points with jaw or biting motions will apply pressure or biting force to the underlying tissue and jawbone, causing discomfort and trauma to the underlying bone and tissue, and ultimately resulting in significant bone erosion. The rest surface or surfaces avoid or reduce this problem by accepting down or biting pressure from the denture. Since the rest surfaces are not positively anchored to the denture, they will not be pulled up or from side to side as a result of jaw motions, and will therefore be less likely to cause bone erosion or damage. The implant assembly is therefore intended to be used at appropriate locations in the jaw which would otherwise be subject to considerable down pressure and potential trauma from an implant such as a full or partial denture or cantilevered bridge. The rest factor surface will be shaped to ensure that it can accept down pressure from an overlying denture in various possible orientations, whatever the angle of the patient's jaw. The support surface prevents excessive force on the tissue, and thus protects the gum tissue from impacting forces which could cause soreness and trauma. Additionally, the rest or support surface prevents or reduces bone erosion by providing support to the distal end of the denture and resisting biting forces.
The implant assembly is designed for implantation at any position in the jaw where a rest factor or surface for a full or partial denture or bridge is needed. Normally, this will be in the posterior jaw, for example in between the first bicuspid and the second molar area, as illustrated in FIGS. 12 and 13, but a rest surface may also be advantageous in other areas. The dimensions of the assembly 10 are selected according to the dimensions of the jaw in the area where the implant is to be used. A range of implant assemblies of different dimensions may be provided for fitting patients having different jaw dimensions. The implant member is designed to provide sufficient anchoring area with the jawbone when embedded in the jaw, while not extending too deeply into the jaw where it might otherwise interfere with the nerve. The implant member has a relatively large diameter, larger than typical straight cylindrical implants, but is shorter in length than such implants, preferably having an overall length in the range from 2 mm to 4.5 mm. In one specific example, several different size implants were provided with annular members of 4.25 mm, 5 mm, and 6 mm outer diameter, respectively. The rest factor may have a diameter of 4 mm. The extension or spigot 28 may also be provided in different sizes according to the position in the jaw where it is to be embedded. Central spigots of length between 1 mm and 3 mm may be provided. Also, the central spigot may be omitted in some cases where very little depth is available in the jawbone for embedding the implant. In this case, the rest factor 18 will also have no projection 40. Rest factors having heads in a range of different sizes are also provided, for example, 3 mm, 4 mm and 5 mm. Generally, the overall implant assembly is very short, extending only from 2 to 4.5 mm into the jawbone, while the implant is shaped to have a relatively large bone to implant contact area, as best illustrated in FIG. 5.
As can be seen in FIG. 5, after osseointegration has taken place, there will be a relatively large area of bone to implant integration even though the penetration into the jaw bone is very short. The implant has first, circumferential surfaces 180, 182 which resist sideways movements of the dentures, while the second, lower surfaces 184, 185, 186 of the outer rim 30, upper face, and boss 28 resist vertical movements. The two surfaces combine to provide maximum rest factor to bone contact with a relatively short distance of penetration into the jawbone. The grooves 29 in the outer surface will resist rotational movements of the implant. Thus, the implant surfaces resist lateral and vertical loosening movements, and the implant effectively becomes fully integrated with the bone.
The method of inserting the implant 12 in the jaw will now be described with reference to FIGS. 6-11 of the drawings. This can easily be done by a dentist or dental surgeon. First, a bore shaped to correspond to the shape of member 12 must be cut out. This is done using a series of special cutting burrs. A first water cooled burr or cutter (not illustrated in the drawings) is used to drill a cylindrical guide hole or pilot dimple at the center of a selected site, for example under the second molar area or at the distal end of a cantilevered bridge. The width of the alveolar crest with equal distance on both sides of the pilot dimple is then measured. The largest diameter rest factor implant which will fit within the available width while allowing at least 1/2 mm of bone on each side of the implant is selected. An internally irrigated implant body drill 44 of diameter matching that of the selected rest factor implant is then selected. Burr 44, illustrated in FIG. 6, has a smaller diameter pilot drill 46 for cutting out a cylindrical bore 48 and a larger diameter portion 50 having an end cutter 52 for drilling out the larger diameter upper end 56 of the bore. The cylindrical portion 50 may be provided with suitable markings or a scale (not shown) so that the dentist can control the depth the drilled bore. However, in the preferred version, the height of portion 50 matches the height of implant member 12. The length of the pilot drill 46 will correspond to the length of spigot 28 of the implant, so that spigot 28 will fit in bore portion 48. The dentist determines the optimum angle and drills in to the bone to a point where the larger diameter portion 50 ends.
The tissue or gum 21 is then secured over the implant and healing screw with conventional flap sutures 80. Since the head portion of the healing screw projecting above the implant member is relatively short, little or no bulge will be apparent when the tissue is sewn up. The site is left to heal for several months to allow the implant to osseointegrate, or bond with the surrounding bone. At this time, a special locating tool 82, best illustrated in FIGS. 4A, 9 and 10, is used to locate the implant.
FIG. 14 of the drawings illustrates an alternative embodiment of the implant assembly which is much thinner than that of FIGS. 1-3 and 5 and which will therefore project only a minimal distance into the jawbone, further reducing the risk of interference with the nerve. This implant assembly is useful for providing a rest surface at a desired location in any patient's jaw, whether or not previous bone erosion is a factor, but is particularly useful in patients having significant bone erosion where very little depth is available for implants.
FIG. 14 illustrates an implant member 180 and healing screw 182 of an implant assembly according to a second, modified embodiment of the invention. FIG. 18 illustrates the implant member 180 and healing screw 182 of FIG. 14 implanted in the jawbone during the osseointegration process, while FIGS. 15-17 illustrate a modified method of forming a bore in the jawbone for receiving the implant.
As illustrated in FIGS. 14 and 18, implant member 180 is a flat disc-like member having an undersurface of similar shape to the undersurface of member 12 in the first embodiment. However, the peripheral rim 184 and central spigot 186 are approximately the same length in this embodiment, so that the spigot 186 does not project downwardly below the lower end of rim 184. Preferably, member 180 has a total height of around 2 mm while its peripheral rim 184 projects around 1 mm below the undersurface of disc part 188. The member 180 is provided in a range of diameters, preferably 4.25 mm, 5 mm and 6 mm, for patients having varying alveolar ridge widths. As in the first embodiment, the maximum diameter possible implant member is selected for the patient dependent on the available space, i.e., the alveolar ridge width. The rim 184 is relatively thin, and in one particular example had a thickness of the order of 0.4 mm.
The member 180 has a recess 190 in its upper surface with a taper 191 extending around the outer periphery of the recess. A central, straight cylindrical bore 192 extends from the center of recessed area 190 into the spigot 186, and bore 192 has screw threads 193 extending along its length. Member 180 is made of the same material as the implant 12 of the first embodiment. As in the first embodiment, circular or rounded indents 194 are provided on the outer surface of member 180 to resist rotational movement after implantation. Between six and eight equally spaced indents may be provided, for example.
Healing screw 182 has a relatively short head portion 195 and a downwardly depending, screw threaded shaft portion 196 for mating engagement in the bore 192 of implant member 180, as illustrated in FIG. 18. The undersurface of head portion 195 seats in recessed area 190 and has a tapered annular surface portion 197 for seating on taper 191 around the recessed area 190, for accurate seating of the screw in bore 192. The upper surface of head 195 has a central, tool receiving bore 198 for receiving the end of a suitable tool for inserting the arrangement in a previously prepared bore in the jawbone, and also for receiving the end of locating tool 82 as described above in connection with the first embodiment of the invention. Bore 198 is of hexagonal cross-section, and is designed to be removed by a suitable removal tool having a hexagonal end after location by tool 82.
The modified method of inserting insert member 180 in the jaw will now be described with reference to FIGS. 15-17 of the drawings. This procedure can easily be carried out by a dentist, although a dental surgeon may also perform the procedure if desired. After the tissue overlying the implant site has been cut, a pilot dimple is formed at the center of the selected site. The width of the alveolar crest or ridge at the implant site is measured, and the largest possible diameter implant which will fit within the available width while leaving at least 1/2 mm of bone on each side is selected.
The finished bore of FIG. 17 is cut to very precise dimensions by the series of cutting drills so that the implant member can be accurately seated in the bore as illustrated in FIG. 18 after suitable treatment of the surfaces and application of bonding agents. The gap below spigot 186 does not affect the integration process and will soon fill in with bone. The accurate, close fitting of peripheral rim 184 into recess 228 provides great stability and resistance against any sideways movement during the three-month or more osseointegration period, so that a good bone-to-implant bond can be produced in spite of the minimal length of the implant.
In both of the embodiments described above, the shape of the undersurface of the implant ensures that there will be little or no side sway either during or after the osseointegration period. This results from the downwardly projecting peripheral rim, having inner and outer circumferential surfaces which combine to resist any sideways forces. This resistance to side-sway is enhanced by the spigot 186 which also acts to resist sideways movement. The relatively large diameter of the implant provides a large area of downwardly facing surfaces which together resist downward forces on the implant assembly, further increasing the stability of the implant and acting to absorb biting pressures. The implant is selected to be of the maximum possible diameter according to the bone width available for implantation in a particular patient. The indents 29, 194 will act to resist rotational movements during and after osseointegration. The combined effect of the shape of the undersurface of the implant and its relatively large surface area is to produce a very stable implant with minimal penetration into the bone.
Although the implant member is illustrated as implanted so that its upper surface is at the bone level, it may be implanted to a lesser depth if the patient has a large amount of bone erosion or resorption. For example, if there is only 1 mm bone depth available for implantation without fear of interference with the nerve, the implant is simply installed to 1 mm in depth so that approximately 1 mm projects above the bone level. However, it will still have sufficient holding power to remain in position since the undersurface, and particularly the peripheral rim, will position the implant during osseointegration and bond to the surrounding bone to resist sideways and downwards forces. Since it is not anchored to any overlying body, upwards forces do not have to be resisted. Thus, sufficient bonding area is provided to resist any loosening during normal wear.
FIG. 19 illustrates a rest factor 250 according to another embodiment of the invention. The rest factor 250 is generally cylindrical and has an upper, dome-shaped portion 252 and a downwardly depending, threaded stem portion 254. The dome portion 252 has hex bore 256 formed in its upper end for gripping by a hex tool on installing or removing the rest factor 250, as will be explained in more detail below. The hex bore will be relatively small, preferably of the order of 0.050", and may be filled with a temporary sealant after installation.
FIGS. 20, 21 and 22 illustrate three alternative types of implant for implanting in the jaw bone at a selected site to receive rest factor 250 or other denture fitting devices Such as denture anchors or magnetic abutments of a conventional type. The implant 260 of FIG. 20 is relatively short and has a body of generally cylindrical shape having an upwardly tapering upper end portion 262 and a downwardly depending stem portion 264. A threaded bore 266 extends downwardly from the upper end of the implant for receiving the threaded stem portion of the rest factor 250. An eight-sided cut 268 extends through the threads, as illustrated in FIGS. 20 and 23. The outer diameter of the implant at its upper end 270 is dimensioned to match the outer diameter of the dome portion of the implant at its lower end 272.
The stem portion 264 of the implant 260 has an annular recess 274 extending upwardly from its lower end to a position close to but offset downwardly from the lower end of the recess 268. Recess 274 forms an outer annular rim 276 and a central boss 278 at the lower end of the implant, and provides an area for bone growth and osseointegration upwardly into the implant. Thus, the implant is generally cup-shaped at its lower end, with a central protrusion in the cupped area. A triple lead screw having a first lead or thread 279, a second thread 280, and a third lead or thread 282 is formed around the outside of the stem portion 264. The threads 279, 280, 282 are preferably of square cross-section and project out a predetermined distance from the surface of the stem portion 264. The threads may each extend around approximately 180� and preferably do not overlap, although they may overlap in alternative embodiments.
FIG. 21 illustrates another implant 284 which is longer than that of FIG. 20. Again, the implant is generally cylindrical and has a relatively thin upper annular portion 286 with a short, upwardly projecting and tapered rim 288 and a downwardly depending stem portion 290 of reduced diameter. A bore 292 projects downwardly from the upper end of the implant 284 and has a threaded portion 294 for receiving the threaded stem of a rest factor member. A ten-sided or decagon cut 296 is formed through the threads, and preferably extends about halfway down the bore 292. In this version, the bore 292 projects downwardly into the stem portion of the implant, since the upper portion 286 and rim 288 are shorter than those of implant 260.
A triple lead thread having first, second and third threads 297, 298 and 299 is formed around the outer surface of stem portion 290. Preferably, the threads 297, 298 and 299 start at equally spaced intervals around the periphery of the stem portion adjacent its upper end but spaced downwardly a distance below the annular ring portion 286. The threads extend around the stem portion towards its lower end and terminate at a location spaced above the lower end of the stem portion. As in the version of FIG. 20, the stem portion 290 has an annular recess 300 at its lower end forming an annular rim 302 and central boss 304. As in the previous embodiment, the upper end 306 of the implant is of diameter matching that of the lower end of the rest factor.
FIG. 22 illustrates another, longer implant 310 which is similar to that of FIG. 21, apart from the fact that the stem portion 312 is longer and a quadruple lead screw is provided on the stem portion. The implant of FIG. 22 is otherwise identical to that of FIG. 21 and like reference numerals have been used for like parts. The implant has a bore identical to that of implant 284 extending downwardly from its upper end, and an annular recess at its lower end which is identical to the recess of implant 284. As in the previous two embodiments, the upper end 304 of the implant has a diameter matching that of the lower end of the dome portion of the rest factor.
A series of four separate threads 314, 316, 318 and 320 is provided around the periphery of the stem portion 312. The threads start at equally spaced intervals around the periphery of the stem at a location close to but spaced slightly below the upper end of the stem portion, to leave a gap between the annular ring 286 and the threads. The gap is in the range from 1 mm to 2 mm.
The pitch or angle of the thread is preferably relatively steep and is preferably in the range from around 9� to 17�. The spacing between adjacent threads is preferably at least 1 mm. It has been found that this is the minimum spacing required to ensure significant bone growth and osseointegration in the gaps between threads. The threads preferably project out around 1/2 mm from the surface of the stem portion of the implant, and they are about 1/2 mm in height. Thus, the gaps between the threads are twice as wide as the threads themselves. This provides good blood supply to the bone between the threads, and provides a greater bone thickness and stronger shelf of bone between the threads.
Both the implants and the rest factor are all made in a range of lengths and diameters to fit the size of different patient's jaws. Implants will be provided in a range of lengths. Preferably, the lengths are of the order of 2 mm, 4.5 mm, 7 mm, 10 mm and 13 mm. The 2 mm length implant will be of the type illustrated in FIG. 20, while the 4.5 mm implant will be of the type illustrated in FIG. 21 and the 7 mm, 10 mm and 13 mm implants will be as illustrated in FIG. 22. Each of the different implants will be provided in a range of different outer diameters, preferably 4 mm, 5 mm and 6 mm. Preferably, the height of the tapered rim of the implant 260 or 310 is as short as possible, for example around 0.5 mm.
The method of installing implants 260, 284 and 286 will be similar with appropriate changes in the dimensions of the drilled bore to accommodate the different length stem portions and numbers of threads. The method will therefore be described for the implant 260 only, by way of example. The implantation method is similar to that illustrated in FIGS. 6-11 and described above.
The first step in the implant procedure is to select the site in the jaw at which the implant is to be installed. The appropriate height and diameter implant member is selected dependent on the bone depth, tissue height, and jaw thickness at the selected site. The minimum bone depth required is 1 mm between the bottom end of the installed implant and the mandibular nerve canal or maxillary sinus space. Thus, the total bone depth required for installing the 2.5 mm implant is only 3.5 mm, while the longer implants can be installed where a greater bone depth is available. The minimum bone width required to place a rest factor implant is 1/2 mm each on the lingual and facial sides of the implant, requiring a 5.0 mm total ridge width for the 4.0 diameter implant, 6.0 mm ridge width for the 5.0 mm diameter implant, and 7.0 mm ridge width for the 6.0 mm implant. Based on these dimensions, the appropriate implant can be selected.
Once the appropriate implant has been selected, a bore shaped and dimensioned to correspond to the shape and dimensions of the implant is cut out. This is done in a series of steps. First, a mesio-distal incision is made through the tissue or gum 321 along the alveolar mid-crest at the selected site, typically the area of the second molar. A bone plateau is created which is made as flat as possible by removing ridges or other bone irregularities. At this point, the width of the alveolar crest can be measured to determine the largest diameter rest factor implant which can be fitted within the available width and still allow at least 1/2 mm of bone on each side. The implant is placed as close as possible to the lingual side while still allowing the 1/2 mm of bone on the lingual side.
At this point, a pilot burr is used to drill out a pilot hole of appropriate depth at the center of the insertion site, as illustrated in FIG. 15 above. The pilot hole diameter will be substantially identical to the diameter of the implant central boss 278. An appropriate depth limiting sleeve is used with the pilot burr in order to limit the depth of the pilot hole to match the implant height. Thus, depth limiting sleeves will be provided for each of the four different implant heights, and the appropriate sleeve will be selected on installation. The lower end of a previously drilled pilot hole 322 in jawbone 323 can be seen in FIG. 24, which illustrates a subsequent step in the procedure.
After alignment, a spot-face drill (not illustrated) is used to make a shallow, 360� shoulder or seat 324 into the crest of the bone. This seat is used to assist in engaging of a bone tap in a later stage of the procedure. The drill is withdrawn several times during site preparation to remove bone buildup between the flutes of the drill. An implant body drill is used to drill out the main recess 328 for receiving the implant. This drill will be similar to drill 44 illustrated in FIG. 6, above, and will have a diameter corresponding to that of the stem portion of the selected implant. Thus, the drill will have a diameter equal to the implant diameter less the thickness of the threads, or 4.0 mm in the case of a 5.0 mm implant, for example.
A series of three guided hand taps (starting tap, intermediate tap and finish tap) are used to make a multiple lead tapped preparation into the drilled hole 328. It will be understood that the triple and quadruple leads will be made in a similar manner. One of the thread taps 336 is illustrated in FIG. 25. Each tap has a tap guide pin 338 which engages the pilot bore to keep the tap centered on the recess. Optionally, a tap guide template (not illustrated) may be secured across the recess via pins secured on opposite sides of the implant site. This can be used to provide better support for the bone tap if the patient has spongy, cancellous bone. The tap 336 has triple lead cutting flutes 340 for forming a thread matching that on the insert. The starting tap has a machined line indicating the start of the double cutting edge of the bone tap. The starting tap is positioned into the drilled recess and the cutting flutes are engaged into the cortical bone, with the machined line on the tap positioned perpendicular to the longitudinal axis of the ridge. The implant site is then hand tapped and threads 342, 343 and 345 are tapped into the recess. The tap is backed off a quarter of a turn several times during the process to clear bone chips. In this way, the tap is worked down to the bottom of the drilled recess 328.
An octagonal wrench 344 is used to place the implant into the prepared implant recess, as illustrated in FIG. 26. The octagonal end of wrench 344 will engage in the octagon 268 cut through the threads 266 and will not damage the threads in bore 266. The implant is completely seated with the implant threads completely engaged in the bone threads and the tapered upper portion of the implant projecting above the level of the bone, as illustrated in FIG. 26. If the implant is set in correctly, the stem portion 264 will have its upper end located 1/2 to 1 mm below the top of the bone, as illustrated in FIG. 26.
A healing screw is then threaded into the implant to protect the internal threads of the implant during the osseointegration period. The healing screw is similar to the healing screw 70 of the first embodiment but with a threaded stem matching bore 266 and a hex hole in place of threaded hole 76 at the upper end of the screw. The flap of gum 321 is sewn down over the implant site, in a similar manner to that illustrated in FIG. 8 above, after installation of the healing screw.
The implant is then left for a healing period to allow the bone to osseointegrate with the surface of the implant. A healing period of not less than 4 1/2 months should be used. The bone will grow over and osseointegrate into the gaps between the threads, providing a greater osseointegration surface area and better retention of the implant. The cup-shaped design of the lower end of the implant, along with the multiple lead threads, increases bone to surface contact and helps to withstand posterior occlusal load.
After the minimum period required for osseointegration, an incision is made over the implant for access to the healing screw. Radiographic charts and finger palpation may be used to locate the general area of the implant. The incision may be made in a conventional manner, but preferably a guided tissue punch 82 is used as in the previous embodiments. The tissue is pierced with the sharp point or probe 91 of the tissue punch, and the implant site is probed until the point 91 locates a hex hole provided on the top of the healing screw. The guided tissue punch 92 is then turned down on the guide with firm pressure until it punches an opening through the tissue or gum. The tissue punch will engage the outside diameter of the healing screw, and will cut out a plug of tissue directly over the center of the implant, as illustrated in FIG. 10 above.
The implant is now exposed for attachment of the dome-shaped rest factor 250 as illustrated in FIG. 27. The implant may alternatively be attached to other dental devices, such as implant anchors or magnetic abutments for dentures. The dimensions of the selected rest factor will depend on the implant dimensions and also the tissue height of the patient. The height of the implant should be such that the top of the dome is at the tissue level or only slightly above it. The dome portion of the rest factor selected should therefore have a height substantially equal to the tissue or gum thickness. If the gingival layer has a height substantially greater than the largest dome portion, tissue reduction must be used to reduce the gingiva thickness to a maximum of 3 mm at the implant site.
Once the correct size rest factor has been selected, a hex wrench 346 having a hexagonal shaft 348 is used to engage the hex bore 256 at the upper end of the dome-shaped upper end portion 252 of the rest factor. The rest factor is then threaded into the bore of the implant, as illustrated in FIG. 27. The tissue is then sewn back around the implant dome, as indicated in dotted lines in FIG. 27, and the dome is left in place for around 4-6 weeks to allow for a period of reduced implant loading during gingival healing. The patient's denture should be fitted to the dome top with a soft reline material to maintain proper occlusion during the gingival healing period. This is done by taking a full arch reline impression including the exposed metal tip of the rest followed to prepare a master cast of the jaw including the exposed tip of the dome. The denture base is relined using this cast in the normal manner.
FIGS. 28 and 29 illustrate a modified insert 350 for use with a rest factor 250 in an equivalent manner to that described above. However, rather than having a multi-faceted cut for receiving a wrench in the threaded bore 352 of insert 350, an external, twelve-sided wrench element 354 is secured to the upper end of insert 350. Element 354 has an outer twelve-sided surface 356 for engaging a wrench with a corresponding internal bore, and a through bore 358 coaxial with threaded bore 352 but of larger diameter. Element 354 is preferably formed separately from insert 350 and then pressure bonded or welded to it. A conventional hex wrench may also be used to engage the element 354.
Apart from threaded bore 352 and wrench element 354, insert 350 is otherwise identical to that of FIG. 21 and like reference numerals have been used as appropriate. It will be understood that a wrench element 354 may also be provided on the insert of FIG. 20 or FIG. 22 in place of the multi-sided internal cut. This avoids the need for a precision machined cut extending through the threads, where the cut must be of precise dimensions between those of the inner and outer diameter of the threads to avoid damaging the threads.
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ANCHORS, INC., CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MAXZUEST;REEL/FRAME:006660/0055Effective date: 19930729Jan 7, 1999ASAssignmentOwner name: CORE-VENT CORPORATION, NEVADAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ZEST ANCHORS, INC.;REEL/FRAME:009693/0700Effective date: 19981222Mar 2, 1999RFReissue application filedEffective date: 19990107Aug 1, 2000REMIMaintenance fee reminder mailedJan 4, 2001FPAYFee paymentYear of fee payment: 4Jan 4, 2001SULPSurcharge for late paymentFeb 25, 2003ASAssignmentOwner name: CENTERPULSE DENTAL INC., CALIFORNIAFree format text: CHANGE OF NAME;ASSIGNOR:SULZER DENTAL INC.;REEL/FRAME:013782/0090Effective date: 20020930Owner name: SULZER CALCITEK, INC., CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CORE-VENT CORPORATION;REEL/FRAME:013782/0109Effective date: 20010108Owner name: SULZER DENTAL INC., CALIFORNIAFree format text: CHANGE OF NAME;ASSIGNOR:SULZER CALCITEK, INC.;REEL/FRAME:013782/0080Effective date: 20010105RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services