Patent Application
20070122764
This invention relates generally to orthodontic treatments and more particularly to a bone screw for use in intra-oral orthodontic corrections.
Presently, a variety of bone screws are commercially available for use for orthodontic anchorage; however, many of these screws generally are intended for retaining tissue grafts and bone plates and to assist in the purpose of craniomaxillofacial reconstruction rather than for use as an orthodontic fixation post. Since such screw geometries were not intended for orthodontic use, they have several limitations relative to such use.
Many bone screws that are available at the present time require one to first perform a soft tissue dissection in the area that the screw will be inserted, then to drill a pilot hole at the desired location for screw insertion. This multiple step surgical procedure for preparation to insert the screws is not only cumbersome, but also it requires skills that are not usually performed by an orthodontist. In addition, by following this procedure, the orthodontist must relocate the predrilled pilot hole in order to insert the self-threading bone screw. Since most of these surgical procedures require small diameter bone screws, relocating the pilot hole prior to insertion of the bone screw can be difficult. Once inserted, these defined screws are typically under an immediate and continuous load incident to the use as an orthodontic anchor, which typically is not a design criterion of the passive retentive maxillofacial bone screw. In general, these maxillofacial screws were developed for the purpose of lag screw retention to hold multiple bone segments together in a passive loading condition, rather than that as a stand alone screw to be used for immediate orthodontic anchorage and multi-axis loading. Yet another limitation is that many maxillofacial reconstructive screws do not incorporate a desired fixation post head for orthodontic appliance attachment; in general these screws are used sub-gingivally and require a low profile head in order to prevent soft tissue irritation.
An object of the present invention is to provide an improved intra-oral craniomaxillofacial rigid fixation screw post for primary anchorage of orthodontic appliances. Another object of the invention is the provision of an orthodontic screw that overcomes the limitations noted above of using maxillofacial reconstruction bone screws for the purpose of orthodontic post anchorage and immediate multi-axis post loading. Yet another object of the invention is the provision of an orthodontic bone screw that can easily pierce and penetrate through the soft tissue and directly into the host bone without the surgical requirements for soft tissue dissection or pre-drilling of a pilot hole. Still another object of the invention is the provision of an orthodontic screw that will enable an orthodontist to insert the screw with the self-piercing and penetrating tip and self tapping locking threads in a single minimally invasive surgical operation. Another object of the invention is the provision of an orthodontic bone screw that once it is rigidly inserted into the host bone, standard orthodontic appliances can be attached to the exposed driving head of the screw. Another object of the invention is the provision of an orthodontic bone screw that does not permanently integrate with the host bone thereby allowing for removal at the completion of orthodontic treatment.
These and other objects of the invention will be apparent from the following description taken with reference to the accompanying drawings.
Briefly stated, an orthodontic, skeletal anchorage bone screw made in accordance with a preferred embodiment of the invention incorporates a sharp tissue piercing, pin-point, tack tip in series with an immediate loading, self-locking, double tapered fixation thread. Distal to the tip and body of the bone screw is a generally cylindrical, dome shaped head that incorporates features for the attachment of standard orthodontic appliances. In use, an orthodontist can easily attach the anchorage bone screw head onto a spline driver tool and insert the screw into the host bone in a single operation. Since the screw is designed for easy insertion without the requirements for soft tissue dissection or a predrilled pilot hole preparation, it is particularly beneficial for an orthodontist who may not be trained in dissection procedures. If desired, the screw thread, such as the uppermost portion thereof, can include suitable surface texturing to enhance functional stability. After the double, self-locking, tapered thread is rigidly fixated into the bone with the one-step surgical procedure, immediate attachment of a standard orthodontic appliance can occur. The invention allows an orthodontist to take advantage of the intra-oral anchorage post for orthodontic movement of the surrounding teeth. Further, the screw provides an orthodontist with a cost effective, completely patient compliant, functional alternative to extra oral orthodontic procedures.
For a more complete understanding of the present invention and further advantages thereof, reference is now made to the following detailed description of the preferred embodiment taken in conjunction with the drawings in which:
References made in the specification and claims to a particular orientation, such as upper, bottom and the like are made with respect to the orientation as shown in the drawings.
As shown in
Going from the apical end of threaded body 11, a first axial length portion 24 comprises a tapered thread having increasing minor 6 and major 3 thread diameters followed by a second axial length portion 10 of a constant (minor and major) thread diameter. The length of second axial length portion 10 varies in dependence on the overall length of bone screw 25. A third axial length portion 26 of a tapered (increasing minor 8 and major 7) thread diameter is formed adjacent to the second axial length portion 10. The tapered thread of axial length portion 26, with its increasing thread diameter, rigidly locks into the bone as the screw is driven in to seating neck 22, to be discussed.
By means of the double, self-locking emergence tapered thread, the screw can be easily inserted while maximizing crestal bone fixation. The coronal portion of the upper tapered thread geometry 26 finishes at the major diameter thread dimension 9 flush with the apical portion of seating neck 22, to be discussed, without any minor diameter thread relief geometry, to enhance the torsional strength characteristics of the screw. The screw, with its unique pin-point 2 and double, self-locking, tapered thread geometry 11, allows an orthodontist to easily and rigidly fixate the screw into a surgical site in a one-step procedure without the requirement for any soft tissue dissection. If desired, the screw thread, particularly the third axial length portion 26, can include suitable surface texturing to enhance functional stability.
The coronal end of the self-positioning and self-starting orthodontic bone screw 25 incorporates a generally cylindrical dome shaped driving head 12 that acts as an anchorage post for the attachment of standard orthodontic appliances. Central to the dome shaped head 12 are two symmetrically located cross-holes 13 that can be utilized for orthodontic wire attachment and multi-axis loading. It will be realized that, if desired, one or more other forms of openings could be provided, such as slot 13- shown in FIG. 1(a). In addition, this central area 23 incorporates symmetrical undercut grooves 20, 21, respectively, that can be used for orthodontic band attachment. Finally, this grooved area 23 has an upper snap attachment configuration 19 comprising a generally right angle circumferential shoulder formed in the upper surface adjacent to groove 20 that allows for the attachment and use of a variety of orthodontic appliances to provide tooth movement.
On the bottom side of the bone screw head 12 is a beveled seating neck 22 that acts as a seating surface when the screw is placed perpendicular to the surface of the bone or off-axis to some pre-determined angle as determined by an orthodontist. Opposite beveled seating neck 22 is a tissue compatible, smooth, cylindrical dome shaped surface 18. In the center of dome shaped surface 18 is a combined square recess 14 and cross-slots 16, providing a spline 17. This combined square and cross-slot spline is used to drive bone screw 25 in or out of the surgical site with a corresponding square block and cross-rib spline pick-up and driver tool 27. Distal to the internal features used for driving the screw is a recessed bored hole 15 used to pick up and deliver bone screw 25 to the surgical site using the corresponding tapered cylindrical tip spline pick-up and driver tool of
As noted above, to deliver orthodontic screw 25 to the host bone site,
Once bone screw 25 is inserted into and seated in the host bone, driver tip 28 can be easily detached from dome shaped driving head 12 of the bone screw by using a push-off driver sleeve 36. This is achieved by turning knurled surface 40 of push-off driver sleeve 36 on shaft 37 in a clockwise direction to axially slide driver sleeve 36 downward until it hits and pushes off of driver head 12 of the bone screw. The axial downward push-off force, which pushes off bone screw head 12, is generated by translating the rotational female thread 38 force on the driver sleeve 36 to the mating male thread 39 on driver shaft 37.
Spline drive head 32 can also be incorporated into a contra-angle driver (not shown) to allow for electrical driver insertion of screw 25.
Although the invention has been described with regards to a specific preferred embodiment thereof, variations and modifications will become apparent to those of ordinary skill in the art. It is therefore the intent that the appended claims be interpreted as broadly as possible in view of the prior art as to include all such variations and modifications.
