Device for Bone Distraction and Tooth Movement

The present invention relates to a device for performing bone distraction and/or tooth movement, and more particularly to a widening or contracting device which is capable of effecting bone distraction in more than one plane of space simultaneously.

Bone distraction and the associated osteogenesis is a process by which bone growth is promoted by cutting a bone and separating it in a controlled manner. As the separation of the bone at the fracture site takes place, new bone is formed in the intervening space created by the separation. Originally, this technique was developed for lengthening the long bones in the body, but was later broadened and is now applied to many parts of the body including the bones in the craniofacial area.

In particular, promoting bone growth in the jaw (mandible) has been under investigation and development for several years to address known deformities associated with the lack of bone in that region. Various surgical procedures have been developed to address bone growth in the craniofacial area and likewise, various appliances have been devised for bone distraction in the craniofacial area.

One of the most common techniques presently in use is cutting the mandible at the apex of the arch and installing a rapid palatal expander (RPE) by affixing its legs to one or more teeth on opposite sides of the palatal arch. Alternatively, the legs of known RPE's can be attached directly to the mandibular bone, or a combination of teeth and bone. The patient (or clinician) then regularly activates the device with a key (pin) which is turned a desired amount daily to achieve the widening effect. One drawback to this technique of utilizing RPE's currently on the market is that the device operates strictly in a linear manner by spreading the cut mandibular bone linearly. This linear spreading may cause the condyles to move laterally out of their sockets, which is highly undesirable. Additionally, many RPE's currently available are bulky and cannot be easily accommodated in patients who have narrow jaws, which is the reason they are undergoing the distraction osteogenesis to begin with. Furthermore, RPE's typically have sharp edges and are not designed to come into direct contact with the soft tissues of the patient's oral cavity. Moreover, the overall rigidity of the RPE may be compromised when the bone is completely distracted. Lastly, the required daily activation of the device can be particularly difficult when the device is affixed in the posterior section of the mouth.

Therefore, what is needed is an expansion (or contraction) device for patients undergoing bone distraction or tooth movement having a smooth finish and a lack of sharp edges such that it can be placed in contact with the soft tissue while expansion (or contraction) is taking place. It is further desired to have a device for use in bone distraction or tooth movement where the movement created is simultaneously in more than one plane of space.

In its broadest aspects, the present invention is a device that can be used for bone distraction or osteogenesis, as well as tooth movement, which includes an expandible (or contractible) member for affixation in the oral cavity of a patient. The device is adapted to provide distraction of a selected craniofacial bone, such as the mandible, or movement of teeth, simultaneously in more than one plane of space. The expandible (or contractible) member includes a mechanism for expanding (or contracting) the expandible (or contractible) member to achieve the desired distraction of the selected bone or movement of selected teeth. Hereinafter, references to expanding, expandible and expand should be considered to also include contracting, contractible, and contract, since the device can be used for expansion or contraction.

In one embodiment, the expanding mechanism comprises a rack and pinion and the expandible member includes a housing that is slidably engaged with the rack. Both the rack and the housing include portions which are adapted to be affixed in the oral cavity of a patient. These portions may be affixed directly to a patient's teeth, to adjacent sections of a craniofacial bone of the patient, or to combinations of a patient's tooth and the craniofacial bone of the patient.

The device has a substantially smooth finish such that it can be placed in contact with the patient's soft tissue without causing undue discomfort to the patient. This means the device may be on the lingual or labial side of the teeth, whichever is the most expedient for the given treatment.

The ability of the device to provide distraction simultaneously in more than one plane of space is due to the fact that the expandible member is either curved (singly or compound) or that the expanding mechanism itself provides movement of the device in more than one plane of space simultaneously. This latter result can be achieved, for example, by a combination rack and rotating pinion in which the interengaging teeth of the rack and pinion are non-parallel (such as conical) and therefore rotation of the pinion causes movement along a compound curve in more than a single, linear plane of space. This results in expansion along a curved line, such as the jaw line, which may take the strain off of the condyle joints of the mandible.

As an alternative to conical or other non-parallel teeth on the rack, the entire device can be curved (in one or more different planes) such that activation of the expanding mechanism causes relative movement of the selected craniofacial bone in more than one plane of space. The gear teeth on the rack and pinion may be helical, or another appropriate design, to improve the engagement and performance of the device.

These and other features and advantages of the present invention will become apparent to persons skilled in the art upon reading the more detailed description which follows, in conjunction with the drawings.

FIG. 1 is a perspective view of one embodiment of the present invention;

FIG. 2 is a top plan view showing the embodiment of FIG. 1 affixed to a patient;

FIG. 3 is a top plan view of a prior art expansion device;

FIG. 4 is a partial cross-sectional view taken on lines 4-4 of FIG. 1;

FIG. 5 is a front elevation of one embodiment of the present invention affixed to the mandible of a patient;

FIG. 6 is a partial rear plan view of an alternative embodiment of the present invention;

FIG. 7 is a perspective view of an alternative embodiment of the rack portion of the present invention;

FIG. 8 is a perspective view of yet another embodiment of the rack portion of the present invention; and

FIG. 9 is still another embodiment of the rack portion of the present invention.

Various features of specific embodiments of the present invention are shown in the accompanying drawings. As stated previously, descriptions herein of expansion and expanding members should also be considered to describe contraction and contracting members.

A preferred embodiment is shown in perspective view in FIG. 1. Generally speaking, the bone distraction device 10 of the present invention includes an expandible member 12 which itself consists of a housing 14 that is slidably engaged with an expanding mechanism 16. The expanding mechanism as shown in FIG. 1 comprises a rack 18 and pinion 20, although other mechanisms can be used. Both the rack 18 and the housing 14 are designed to be affixed in the oral cavity of a patient as for example by depending tabs 22a and 22b. Through-holes 24a and 24b facilitate affixing the housing 14 and rack 18 to a selected craniofacial bone, such as the mandible, by virtue of screws (not shown). FIGS. 2 and 5 show top and front views, respectively, of a device according to the present invention affixed to the mandible 28 of a patient. In those Figures, screws 30a and 30b are shown affixing the device to the patient's mandible.

With reference again to FIG. 1, the pinion 20 engages the teeth 32 of rack 18. This is shown in more detail in FIG. 4. A separate hex wrench 34 may be used by the patient or clinician to actuate the pinion by engaging hex head 36 which is integral with the shaft of pinion 20. By rotating hex head 36 with hex wrench 34, pinion 20 engages rack teeth 32 thereby causing expansion of the expandible member 12 by the sliding engagement between rack 18 and housing 12. By rotating in the proper direction, the expansion of the device is effectuated and by virtue of being affixed to the selected craniofacial bone of a patient, which has previously been split by an appropriate surgical technique, widening or expansion at the split in the bone is accomplished. The device of the present invention permits the periodic expansion to occur.

As is more clearly apparent in FIG. 2, the device of the present invention is configured so as to provide distraction of a selected craniofacial bone simultaneously in more than one plane of space. More particularly, the prior art type expansion devices are shown generally in FIG. 3. These devices operate in a purely linear manner which may cause displacement of the condyles represented by reference numeral 40a and 40b from the temporal mandibular joint (TMJ). This displacement of the condyles 40a and 40b may take place along line D shown in FIG. 3. The device can also be used for tooth movement, such as retraction or distallization of teeth as well as distraction. Further, it may have various applications for distraction of different sections of the maxilla.

As represented diagrammatically in FIG. 2, utilizing the expansion device of the present invention for bone distraction does not result in undesirable displacement of the condyles 40a and 40b. In fact due to the movement imparted by the devices of the present invention (i.e., in two planes of space simultaneously), the condyles are not displaced from the TMJ, but rather the mandible is widened at the point of distraction 42 to follow generally the dotted lines 48a, 48b shown in FIG. 2.

Again with reference to FIG. 1 and FIG. 4, the bone distraction device of the present invention preferably further includes a locking mechanism 50 which is engaged with housing 14 and has a locking extension arm 52 that engages teeth 32 of rack 18 to prevent the rack 18 from sliding relative to housing 14. The lock mechanism 50 may engage the rack 18 at either side of the pinion 20.

It will be appreciated that the simultaneous expansion in two planes of space is accomplished utilizing the device 10 shown in FIGS. 1 and 2 by virtue of the curvature of that device. As an alternative, the embodiment shown in FIGS. 5 and 6 is curved in an arc relative to the plane of the mandible as well as curved to follow the mandibular arch (as is true of the FIG. 1 embodiment). With specific reference to FIG. 6, due to the arcuate curvature of the embodiment shown, it may be appropriate for pinion 20 to be conically shaped and for the teeth 32 of rack 18 to likewise have a conical configuration.

Alternative rack configurations are shown in FIGS. 7, 8 and 9. In the FIG. 7 example, the teeth 32 of rack 18 are not perpendicular to the edges of the rack but rather are angled relative thereto. As will be apparent, but is not shown, the pinion associated with a rack configured as shown in FIG. 7 must have teeth that would correspond to the angled nature of teeth 32 of rack 18. Similarly, FIG. 8 shows yet another alternative configuration for rack 18. In that embodiment, teeth 32 undulate and the associated pinion (not shown) would require teeth to match. Lastly, FIG. 9 shows an alternative embodiment wherein there are two sets of rack teeth 32a and 32b. Racks 18a and 18b are offset relative to one another by the width of the one tooth and would require a pinion (not shown) that has dual sets of teeth for engagement with the offset racks 18a and 18b. It will be appreciated by persons skilled in the art that any configuration of rack and pinion can be utilized successfully in the context of the distraction device of the present invention. Therefore, the invention is not intended to be limited to the specific examples shown and described herein. Furthermore, it will be appreciated by persons skilled in the art that other mechanisms for providing expansion (or contraction) simultaneously in two planes of space are possible. Examples of actuating mechanisms other than the rack and pinion mechanism shown herein, are screw-type expanders and other mechanisms known in the art.

Having thus described the invention with reference to the accompanying drawings, it must be borne in mind that the invention is not intended to be limited to the specific structural embodiments shown and described. As stated above, numerous variations for the rack and pinion configuration are contemplated in addition to those shown herein. Furthermore, other expansion mechanisms are contemplated with the common requirement being that simultaneous movement in more than one plane of space is effectuated. Otherwise, the scope of the present invention is only limited by the claims which follow.