Abstract:
A modified dental implant fixture designed with a multiple of three or more thread or groove patterns which provide adequate wall thickness for a deep female conical connection such that the threads or grooves transition from smaller to larger moving in the apical direction along the long axis of the dental implant.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    None. 
       ABSTRACT 
       [0002]    A modified dental implant fixture designed with a multiple of three or more thread or groove patterns such that the threads or grooves transition from smaller to larger moving in the apical direction along the long axis of the dental implant body. Such a modified implant maintains adequate wall thickness for a deep conical connection. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present disclosure relates generally to dental implants, and more specifically to a dental implant having a deep female conical connection which can result in limited wall thickness. By combining an innovative thread or combination of thread and groove patterns that transition from smaller coronal to larger and deeper apical threads, which are helpful in providing greater primary stability, a dental implant that maintains adequate wall thickness, when a deep conical connection is utilized, is achieved. 
         [0004]    Dental implants are used in place of missing natural teeth to provide a base of support for single or multiple teeth prosthetics. These implants generally include two components, the implant itself and the prosthetic mounting component referred to as an abutment upon which the final prosthesis is installed. The implant has apical and coronal ends, whereby the coronal end accepts the base of the prosthetic abutment using connection mechanisms of different designs. One such mechanism is a deep female conical receptor with an internal alignment or anti-rotational component such as a hex, double hex, spline or other single/multi-sided arrangement used for prosthetic alignment and anti-rotation stability. Deep female conical connections have been shown to prevent micro movement between the implant body and the abutment when loaded but can have the disadvantage of limited wall thickness especially if the implant is of a tapered design. 
         [0005]    In practice, the implant body is surgically inserted in the patients jaw and becomes integrated with the bone. More specifically, the implant body is screwed or pressed into holes drilled in the respective bone. The surface of the implant body is characterized by macroscopic and microscopic features that aid in the process of osseointegration. Once the implant is fully integrated with the jaw bone, the abutment is ready to be mounted. For two-stage implant designs, the abutment passes through the soft tissue that covers the coronal end of the implant after healing and acts as the mounting feature for the prosthetic device to be used to restore oral function. Implants of the single-stage design extend at least partially through the soft tissue at the time of surgical insertion. The coronal end of the implant body acts as part of a built-in abutment design with the margin of the coronal collar usually being employed as the margin of attachment for the prosthesis used to restore oral function. 
         [0006]    Both single and two stage implants are characterized by a central bore hole at their coronal ends that is generally threaded to accept a central screw to hold the abutment securely to the implant body. The exception would be some implants where the abutment is friction fit into the central bore hole and no screw is required. In any event, the implant, abutment, and screw are typically fabricated from titanium or a titanium alloy. Some implants are zirconia based, alumina based or sapphire based ceramics, and, in regions of high esthetic demands, the abutments are zirconia based. In some instances, ceramics and metals are combined to make a single component, though this is usually limited to the abutment component of the implant system. There is also promising research on the use of titanium zirconia alloys as well. 
         [0007]    One of the original implant designs was the so-called Branemark type implant characterized by an external hex. The hex was originally used to insert the implant and later utilized as an external anti-rotational and alignment element. This design usually displays a bone loss pattern described as a cupping of the bone at the coronal end of the implant once loaded with occlusal forces. This cupping pattern usually stabilizes after about one year of function with vertical bone loss of approximately 2 mm. By that time, loss of bone critical to the predictable support of overlying soft tissue is lost. As implant designs evolved internal connections utilizing an internal hex became much more common. For example, Astra Tech Inc. (“Astra”) was one of the first companies to introduce a deep conical design and use a double hex as their internal orientation element. 
         [0008]    In addition to having a more stable implant connection (deep female conical connection), Astra has also addressed the coronal bone loss by introducing micro threads at the coronal aspect of the implant body. This further modification is designed to distribute and transfer forces to the surrounding bone. However, clinicians are increasingly demanding dental implants with macro designs that achieve higher insertion torque values that generally translate to high initial implant stability. Prior Astra implants with a coronal flair had a single lead micro thread of 0.185 mm combined with a single lead apical thread of about 0.6 mm. To increase primary stability the micro threads were increased to 0.22 mm and made triple lead so as to be timed, together with having the same pitch, as the apical threads. This dramatically increased the required insertion torque and primary stability. Accordingly, in order to have more aggressive/deeper apical threads with wider spacing in combination with coronal micro threads of a similar dimension and still allow for adequate wall thickness for the deep female conical connection, an additional transitional thread pattern(s) of intermediate thread size(s) between the coronal micro threads and the larger apical threads is disclosed herein. However, the same thread pattern with inherent advantages can be utilized with any implant and is not limited to one with a deep conical connection. 
         [0009]    Another advantage to a larger apical thread, in addition to increasing primary stability, is to increase surface area particularly on larger diameter implants when wall thickness is less of an issue. While apical threads in the size range of 0.6 to 0.66 may be ideal for implants in the 3.0 to 4.5 mm diameter, larger diameter implants have adequate distance between the central bore hole and the outer wall to allow for deeper apical threads. The resulting increase in surface area is particularly beneficial for large diameter, shorter implants which, depending on the clinical circumstances, would allow surgeons to avoid the maxillary sinus in the upper posterior region of the mouth. 
         [0010]    More recent Astra implants have moved away from using an untimed micro thread of approximately 0.185 mm paired to a single lead apical thread of 0.6 mm, and now use a triple lead micro threads of about 0.22 mm timed to a single apical thread of approximately 0.66 mm. Meanwhile, U.S. Pat. No. 7,677,891 to Niznick (incorporated herein by reference) proposes quadruple lead (i.e.4X) coronal threads spaced 0.3 mm apart and timed to double lead (i.e. 2X) apical threads spaced 0.6 mm apart with the 4X coronal threads being spaced considerably greater than 0.22 mm. Referring to  FIG. 1 , the implant  10 , includes a tapered body  12  with two externally-threaded regions  14  and  16 . Proximal, externally-threaded region  14  includes V-shaped X 4  lead threads all of which have the same pitch. Distal portion  16  includes V-shaped X 2  lead threads. This type of implant design has a couple of disadvantages. First, in soft bone, the apical threads are limited to approximately 0.6 mm because coronal micro threads cannot be any larger than 0.3 mm and maintain crestal bone. Perhaps more critical, is the fact that a 2X apical thread increases the insertion speed. Specifically, if a sloped topped (e.g. U.S. Pat. No. 6,655,961) or asymmetric (e.g. copending application U.S. Ser. No. 12/494,510) coronal configuration is utilized, controlling the speed of the implant advancement into the host bone is essential. Accordingly, and as disclosed herein, the most apical thread should be a single thread (i.e. X 1 ). 
         [0011]    There is considerable prejudice among dentists and manufactures as to the benefits of tapered or straight walled implant designs. Some, like Astra, even combine a tapered coronal aspect with a parallel walled apical portion of the implant. Most now agree that some type of tapered apical cutting end, even on the parallel walled design, is desirable. This is demonstrated on Astra&#39;s recently introduced TX (tapered apex) design. Referring to  FIG. 2  in particular, the implant  20 , includes a straight walled body  22  with two externally-threaded regions  24  (proximal) and  26  (distal). The tapered apex  28  has been added to make initial installation, into holes drilled in the respective bone, easier. 
         [0012]    However, both straight, tapered or a combination of tapered and straight bodied dental implants have their place in the field of implant dentistry depending on bone type and clinical application. For example, in the upper arch the bone is softer and the apical ends of adjacent teeth are closer together than in the lower arch. Therefore, a tapered design (that with a smaller apical end) fits between the roots of adjacent teeth more suitably while the tapered design compresses the softer maxillary bone upon insertion thus increasing implant primary stability at the time of placement. In the lower arch the bone is denser and root proximity is less of an issue so implants with parallel walls are considered more suitable by many clinicians. 
         [0013]    A tapered implant with a truly more concave profile has not been utilized in the dental implant field. While Astra does transition from a straight apical end to a 6 degree flared coronal design, the transition is abrupt. What is proposed herein is a 2 and then a 5 degree concave flare (or any like progressive) transition be utilized. Besides allowing adequate wall thickness, another advantage, when combined with the proposed herein combination of thread sizes, is to increase implant primary stability as measured by resonance frequency analysis while possibly lowering the amount of torque required to seat the implant. 
         [0014]    Accordingly, it is a general object of this dosclosure to provide a series of thread or a combination of groove and thread patterns that transition in spacing, size, pitch and depth such that adequate wall thickness for a deep internal female conical connection is maintained while allowing for an apical macro tread design that will result in greater primary stability for the dental implant while still keeping the rate of insertion within the limits that allow for either a sloped or asymmetric coronal configuration. 
         [0015]    It is a another object of this disclosure to enable implants with a tapered implant body to maintain adequate wall thickness when utilizing a deep female internal conical connection and still allow for a macro tread design that will result in greater primary stability while still keeping the rate of insertion within the limits that allow for either a sloped or asymmetric coronal configuration to be aligned with the surrounding bony topography. 
         [0016]    It is a further object of this disclosure to enable implants with a concave tapered implant body profile to maintain adequate wall thickness when utilizing a deep female internal conical connection and still allow for a macro thread design that will result in greater primary stability while still keeping the rate of insertion within the limits that allow of either a sloped or asymmetric coronal configuration to be aligned with the surrounding bony topography. 
         [0017]    It is a more specific object of this disclosure to enable a large diameter, shorter length implants with deeper apical threads with increased surface area while maintaining adequate wall thickness for a deep conical connection and coronal micro threads. 
         [0018]    These and other objects, features and advantages of this disclosure will be clearly understood through a consideration of the following detailed description. 
       SUMMARY OF THE INVENTION 
       [0019]    According to an embodiment of the present invention, there is provided a dental implant for implanting within a human jawbone having an implant body with an outer surface, a longitudinal axis, a coronal end and an apical end. The coronal end includes a deep female conical receptor that creates a wall thickness between the outer surface of the implant body and the receptor. At least three differently sized threaded regions are positioned on the outer surface of the implant body with each region transitioning from smaller to larger in the apical direction along the axis. 
         [0020]    There is also provided a dental implant for implanting within the human jawbone having a longitudinal implant body with an outer surface, an apical end and a coronal end. A series of three or more thread patterns that start near the coronal end are in series with each one becoming progressively larger, deeper and/or wider in size when moving in the apical direction along the implant body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a side elevational view of a prior art implant. 
           [0022]      FIG. 2  is a side elevated view of a prior art implant having a tapered apex. 
           [0023]      FIG. 3  is a cross-sectionals side elevated view of a prior art implant without thread timing or a tapered apex. 
           [0024]      FIG. 4  is a cross-sectional side elevational view a prior art implant with thread timing and a tapered apex. 
           [0025]      FIG. 5  is a cross-sectional side elevational view of an implant according to the principles of an embodiment of the present invention. 
           [0026]      FIG. 6  is a cross-sectional side elevational view of an alternate embodiment of an implant. 
           [0027]      FIG. 7  is a cross-sectional side elevational view of an alternate embodiment of an implant. 
           [0028]      FIG. 8  is a cross-sectional side elevational view of an alternate embodiment of an implant. 
           [0029]      FIG. 9  is a cross-sectional side elevational view of an alternate embodiment of an implant. 
           [0030]      FIG. 10  is a cross-sectional side elevational view of an implant. 
           [0031]      FIG. 11  is a side elevated view of an implant according to the principles of an embodiment of the present invention. 
           [0032]      FIG. 12  is a side elevated view of an alternate embodiment of an implant. 
           [0033]      FIG. 13   a  is a side elevated view of an alternate embodiment of an implant. 
           [0034]      FIG. 13   b  is a cross-sectional side elevational view of the implant of  FIG. 13   a.    
           [0035]      FIG. 13   c  is a top plan view of the implant of  FIG. 13   a.    
           [0036]      FIG. 13   d  is a perspective view of the implant of  FIG. 13   a.    
           [0037]      FIG. 13   e  is a detailed view of the variable thread form detail of  FIG. 13   a.    
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    An embodiment of the subject invention will now be described with the aid of numerous drawings and included measurement designations. Unless otherwise indicated, such measurements are used for explanatory purposes only and they are not deemed to be limiting of the disclosed embodiments herein. The purpose of describing these measurements is to illustrate that the concept of using three or more thread or groove patterns while maintaining adequate wall thickness for a deep conical connection can be utilized for a wide variety of implant sizes and designs. 
         [0039]    In any event, turning now to the Figures, and in particular  FIG. 3 , a prior art dental implant  30  is illustrated. This implant  30  is 11 mm long and has a step-wise diameter taper from 4.5 mm at its coronal end to 3 mm at its apical end. Two 60° thread patterns, at 1X to 1X are used on this implant  30 . The coronal threads  32  are 0.185 mm apart with grooves 0.1 mm deep, while the apical threads  34  are 0.6 mm apart with grooves 0.325 mm deep. The deep female conical connection  36  is the space within the implant  30  denoted by the dotted lines. This design provides for an upper wall thickness  38  of 0.303 mm and a lower wall thickness  40  of 0.440 mm. 
         [0040]    The prior art implant  50  of  FIG. 4  is the next generation Astra design of  FIG. 3  and is again 11 mm long, but instead of having a step-wise diameter taper from 4.5 mm to 3 mm ( FIG. 3 ), it utilizes a tapered apex (similar to  FIG. 2 ) going down to 2 mm. While such a tapered apex makes installation of the implant easier, the thread pattern needed to be adjusted in an attempt to increase wall thickness for the deep conical connection. Specifically, two 80° thread patterns, at 1X to 3X, are used on this implant  50 . With 80°, the resulting reduced thread depth will increase the wall thickness. The coronal threads  52  are 0.22 mm apart with grooves 0.082 mm deep, while the apical threads  54  are 0.66 mm apart with grooves 0.246 mm deep. The deep conical connection  56  has an upper wall thickness  58  of 0.321 mm and a lower wall thickness of 0.519 mm. The change to 0.22 mm 3X coronal thread timing dramatically increases implant primary stability while the change to 80 degree threads increases all thickness for both the coronal threads  52  and the apical threads  54 . 
         [0041]    It has become apparent that an implant having a deep female conical connection is preferred to prevent micro movement between the implant and the abutment. In order to have both deeper apical threads that increase primary stability and coronal micro threads or grooves that better distribute force to the surrounding bone, an embodiment of the present invention adds at least one intermediate or middle thread to the pattern. This additional thread provides the necessary wall thickness to prevent implant breakage during function. 
         [0042]    There have been studies claiming that certain thread timing patterns are more ideal than others. Specifically, that a 2X to 4X combination allows for the micro threads to follow partially in the path of the major apical thread with only a new middle thread being cut. However, Astra&#39;s 1X to 3X thread does much the same thing where the transition to 3X from 1X merely adds one smaller thread above and one below the major thread which itself transitions to a micro thread following the prior path of the major thread. While the 2X to 4X pattern avoids cross cutting the major apical threads, the 1X to 3X Astra pattern does essentially the same thing. Accordingly, in one of the solutions disclosed herein, a 1X to 2X to 3X thread pattern, there would be cross cutting for the 2X apical threads but not for the most coronal 3X micro thread. However, as long as the same thread pitch is maintained in a tapered implant design or one with a slightly concave coronal profile cross cutting is inconsequential as the bone is being compressed and expanded outward. 
         [0043]    Cross cutting may be avoided for either a straight walled or tapered body implant using a 1X to 2X to 4X combination. However, bone gap jumping of up to 0.5 mm is clinically proven upon the immediate implant placement and therefore the only possible benefit might be for the ease of implant insertion as bone healing will fill in any cross threaded area in the bone. Taken to the extreme, and taking a 1X to 3X to 5X combination as an example, only the 5X portion would start to cross cut the 3X threads and only for the most coronal 20-25% or less. Furthermore, with a 1X to 2X to 4X, or a 1X to 3X to 6X no cross cutting would take place. For those knowledgeable in multiple lead thread timing this is well understood. 
         [0044]    The utilization of a middle thread to the pattern will now be described. An example thereof is first shown in  FIG. 5 . In particular, this implant  70  is 11 mm long and has a step-wise diameter taper from 4.5 mm at its crown to 2 mm at its apex and is shown with 5° of coronal taper  72  and 2° of mid wall taper  74 . Three thread patterns, 80° at 1X to 80° at 2X to 80° at 4X, are used on this implant  70 . The coronal threads  76  are 0.22 mm apart with grooves 0.082 mm deep, the middle threads  78  are 0.44 mm apart with grooves 0.164 mm deep and the apical threads  80  are 0.88 mm apart with grooves 0.476 mm deep. The deep conical connection  82  has a mid wall thickness  84  of 0.372 mm and a lower wall thickness  86  of 0.607 mm, both of which exceed the parameters for prior art  FIGS. 3 and 4 . 
         [0045]    While the straight walled apical diameter  88  has increased to 3.868 mm due to the increased thread depth in that region, the implant will go into the same diameter bone site as the prior art implant of  FIG. 4 . Further, since the apical wall thickness has been increased to 0.607 mm, the parallel walled region could become slightly tapered with a minimal apical wall thickness equal to or greater than 0.519 mm shown in  FIG. 4 . It should be noted that the implant of  FIG. 4  does not allow the parallel walled section to become tapered because the apical threads were changed from 60° to 80° from the prior art of  FIG. 3  in order to increase wall thickness for additional strength. 
         [0046]    It will be appreciated that merely adding an intermediate or middle or transitional thread to any implant will not create the acceptable wall thickness. For example, implant  90  of  FIG. 6  differs from  FIG. 5  by using 6° of coronal and 3° of mid wall taper and again all three thread patterns are at 80° and the apical thread  92  depth is 0.328 mm. This allows a mid wall thickness  94  of only 0.304 mm and a lower wall thickness  96  of 0.518 mm. The lower wall thickness is acceptable but the middle wall thickness is less than prior art  FIG. 4  and the parallel wall section could not become slightly tapered as for the implant shown in  FIG. 5  as it is already 0.001 mm below minimum dimension per  FIG. 4 . Accordingly, the implant described in  FIG. 5  is preferable to the implant of  FIG. 6 . 
         [0047]    Three or more thread patterns can also be used on larger implants. For example, 11 mm long with step-wise diameter taper from 5 mm to 2.5 mm implants are shown in  FIGS. 7 and 8 . Referring first to  FIG. 7 , the implant  100  has a thread pattern of 60° at 1X to 80° at 3X to 80° at 5X. The coronal threads  102  are 0.2 mm apart with grooves 0.074 mm deep, the middle threads  104  are 0.33 mm apart with grooves 0.123 mm deep and the apical threads  106  are 1 mm apart with grooves 0.541 mm deep. The deep conical connection  108  has a mid wall thickness  110  of 0.595 mm and a lower wall thickness  112  of 0.553 mm. 
         [0048]    The implant  120  of  FIG. 8  has all three thread patterns at 80° with a 1X to 3X to 6X pitch. The coronal threads  122  are 0.2 mm apart with grooves 0.074 mm deep, the middle threads  124  are 0.4 mm apart with grooves 0.149 mm deep and the apical threads  126  are 1.2 mm apart with grooves 0.447 mm deep. The deep conical connection  128  has a mid wall thickness  130  of 0.569 mm and a lower all thickness  132  of 0.647 mm. 
         [0049]    Referring now to  FIG. 9 , this implant  140  is 11 mm long and has a step-wise diameter taper from 4.5 mm at its crown to 2 mm at its apex. Three thread patterns, 80° at 1X to 80° at 2X to 80° at 3X, are used on this implant  140 . The coronal threads  142  are 0.22 mm apart with grooves 0.082 mm deep, the middle threads  144  are 0.44 mm apart with grooves 0.164 mm deep and the apical threads  146  are 0.66 mm apart with grooves 0.246 mm deep. The deep conical connection  148  has a mid wall thickness  150  of 0.372 mm and a lower wall thickness  152  of 0.689 mm. 
         [0050]    The slightly more tapered implant  160  of  FIG. 10  has the same thread pattern and measurements of  FIG. 9 . However, as discussed with regard to  FIG. 6 , and due to the implant  160  dimensions, acceptable wall thickness is not created. While the deep conical connection  162  has a lower wall thickness  164  of 0.599 mm, the mid wall thickness  166  is merely 0.304 mm. Accordingly, the implant described in  FIG. 9  is preferable to the implant of  FIG. 10 . 
         [0051]      FIG. 11  shows a dental implant  170  with multiple thread patterns in profile. In this case, the deep apical threads  172  are followed by middle threads  174  and then coronal threads  176  up to the unthreaded portion  178  and top surface  180 . 
         [0052]      FIG. 12  shows a dental implant  190  with an addition set of threads. In particular, the deep apical threads  192  are followed by middle threads  194  and coronal threads  196  leading to parallel groove threads  198  before reaching the unthreaded portion  200  and the top surface  202 . It will be appreciated that two or more parallel groove patterns may be employed. 
         [0053]    One of the more advantageous uses for the present invention is to allow for wider diameter dental implants; the same can be said of shorter and wider diameter implants. For example,  FIG. 13   a  shows an implant  210  that is 6.50 mm long and has a diameter taper from 5.50 mm at its crown to 4.75 mm at its apex. Three thread patterns, a 1X to 2X to 3X all at 60°, are used on this implant  210 . The coronal threads  212  are 0.25 mm apart with grooves 0:14 mm deep and the middle threads  214  are 0.375 mm apart with grooves 0.20 mm deep. As for the apical threads  216 , they are shown with the apical minor diameters progressively being lowered, which results in the most apical thread having a more aggressive cutting profile (see  FIG. 13   e ). Conversely, allowing the minor diameter to migrate coronally will result in a most apical buttress thread. The deep conical connection  218  of this shorter implant  210  is shown in  FIG. 13   b - d . The combination multiple thread pattern of this design maintains the necessary wall thickness  220  between the deep conical connection  218  and the grooves of the thread patterns. 
         [0054]    Alternatively, 60° 1X, 2X, 4X threads could be used with the coronal threads  212  being 0.22 mm apart and 0.12 mm deep and the middle threads  214  being 0.44 mm and 0.24 mm while the apical threads would be spaced 0.88 mm apart and be variable or of consistent depth. 
         [0055]    The present disclosure addresses the issue of limited wall thickness associated with a deep conical connection. However, there are other advantages inherent in the design that could equally be applied to the implant with a different abutment connection Accordingly, while particular embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the invention if its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the present invention.