BACKGROUND OF THE INVENTION The craniofacial region of the body includes the region of the head comprising the craniofacial bones, including the maxilla (i. e. , the upper jaw bone), the hard palate and the<BR> nose, and the mandible (i. e. , the lower jaw bone). Many dental procedures require sufficient bone height for proper anchoring and osteointegration of objects, such as implants, in the craniofacial region. If there is insufficient bone height, such as insufficient alveolar bone height, augmentation of the deficient bone may be required. For example, the maxillary sinus membrane (located in the upper jaw) may be elevated or the inferior alveolar nerve (located in the lower jaw) may be transposed to allow room for placement of bone graft, collagen or other suitable synthetic bone substitutes or filler material.

Bone distraction followed by osteogenesis is another example of a method for augmentation of deficient bone. Bone distraction generally involves cutting a bone and separating it in a controlled manner. As the separation of the bone at the fracture site takes <BR> <BR> place, new bone is formed (i. e. , by osteogenesis) in the intervening space created by the separation. However, distraction used in dental procedures generally requires a skilled dental surgeon and great care so as not to damage nerves in the region.

SUMMARY OF THE INVENTION The present invention seeks to provide improved dental assemblies for, inter alia, detecting and locating nerves while drilling, osteogenesis of implants, and alternative apparatus for bone distraction, wherein the periosteum, not the bone, is augmented.

There is thus provided in accordance with an embodiment of the present invention a dental assembly including a drill assembly including nerve-locating apparatus. The nerve locating apparatus may include a first electromagnetic energy element adapted to generate a nerve stimulating electrical impulse, and may further include a second electromagnetic energy element adapted to sense the electrical impulse. The second electromagnetic energy element may sense a modification of a property of an electromagnetic field as modified by the first electromagnetic energy element. The drill assembly may include a drill bit formed with a lumen, and at least one of the first and second electromagnetic energy elements may be disposed in the lumen. At least one of the first and second electromagnetic energy elements may include an electrode or a magnetic member. At least a portion of the assembly may be biodegradable.

There is also provided in accordance with an embodiment of the present invention an assembly including an electro-osteogenic implant.

There is also provided in accordance with an embodiment of the present invention dental assembly including an outer interface element adapted to be fixed in a craniofacial structure, the outer interface element having a receiving portion, and an inner element including a periosteum engaging member and adapted to be received in the receiving portion, the inner element being selectively movable outwards of the receiving portion so that the periosteum engaging member lifts a periosteum away from the craniofacial structure.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended drawings in which: Fig. 1 is a simplified pictorial illustration of a drill of a dental assembly with nerve locating apparatus, constructed and operative in accordance with an embodiment of the present invention; Fig. 2 is a simplified pictorial illustration of the dental assembly of Fig. 1 being used to drill a hole in a mandible while locating a mandibular nerve, in accordance with an embodiment of the present invention; Figs. 3A and 3B are simplified graphical illustrations of electrical responses associated with the nerve locating apparatus of Fig. 2, respectively before and after generation of an action potential due to drilling near a nerve; Fig. 4 is a simplified pictorial illustration of a dental assembly with nerve locating apparatus, constructed and operative in accordance with another embodiment of the present invention; Figs. 5A and 5B are simplified illustrations of dental assemblies comprising an electro-osteogenic dental implant, constructed and operative in accordance with different embodiments of the present invention; Fig. 6A is a simplified top-view illustration of one of the dental implants of Fig. 5A, constructed and operative in accordance with an embodiment of the present invention; Fig. 6B is a simplified top-view illustration of one of the dental implants of Fig. 5A, constructed and operative in accordance with another embodiment of the present invention, and comprising a resistor disposed between a galvanic cell element and a contour of the dental implant; Fig. 7 is a simplified graphical illustration of accelerated osteointegration as a result of an electrical current or field in the vicinity of the dental implants of Fig. 5A and 5B and neighboring bone, in accordance with an embodiment of the present invention; Fig. 8A is a simplified illustration of a defect in the craniofacial region, which may be corrected by a dental assembly of the present invention; Figs. 8B and 8C are simplified illustrations of a dental assembly, respectively before and after periosteal augmentation, in accordance with an embodiment of the present invention; and Fig. 8D is a simplified illustration of another version of the dental assembly of Figs.

8B and 8C.

DETAILED DESCRIPTION OF THE PRESENT INVENTION Reference is now made to Figs. 1 and 2, which illustrate a dental assembly 10 constructed and operative in accordance with an embodiment of the present invention.

Dental assembly 10 preferably includes a drilling assembly 12 and nerve locating apparatus 14. Nerve locating apparatus 14 may operate via the application of electrical energy, as is now explained.

Nerve stimulators are known and used as a means to effectively locate peripheral nerves for surgical and therapeutic purposes. Such purposes include, for example, localization of the nerve for the administration of regional anesthesia or to avoid cutting the nerve during sectioning or excision of tissue. Nerve localization via the application of electrical energy is based on the fact that a pulse of electricity may stimulate a nerve fiber to contract an innervated muscle or cause paresthesia in the case of sensory nerves. It is known that if the site of stimulation is a significant distance from the target nerve, a stimulus of high intensity is required to effectively stimulate the nerve. If the site of stimulation is relatively close to the nerve, a low intensity stimulus is sufficient to stimulate the nerve. However, unlike the present invention, drilling assemblies have not heretofore comprised nerve stimulators or locators.

Nerve locating apparatus 14 may include a first electromagnetic energy element 16 adapted to generate a nerve stimulating electrical impulse, and a second electromagnetic energy element 18 adapted to sense the electrical impulse. (The term"electromagnetic" encompasses electrical energy, magnetic energy and any combination thereof. ) In one embodiment of the invention, one of the electromagnetic energy elements comprises a stimulator electrode 20 disposed in a lumen 22 formed in a drill bit 24 of drill assembly 12 (best seen in Fig. 1). The other electromagnetic energy element may comprise a return electrode 26 attached to a patch 28, such as but not limited to an electrocardiogram (ECG) type patch, which may be affixed in the vicinity of a nerve, such as but not limited to, a <BR> <BR> mandibular nerve, e. g. , the inferior alveolar nerve 30. A ground electrode 32 may also be provided, and may be attached to a patch 34 affixed in another suitable portion of the jaw anatomy, such as but not limited to, a portion below the inferior alveolar nerve 30. All the electrodes may be connected via a connector 36 to a controller 38, adapted to receive and process electrical signals from the electrodes. Controller 38 may also comprise a power supply and other circuitry for generating the electrical signals. Portions of dental assembly 10 may be optionally constructed of a biodegradable material.

Drill bit 24 may be held in a chuck 40 of any kind of drill 42, such as but not limited to, an electrically or pneumatically powered drill.

In one operation of dental assembly 10, as seen in Figs. 3A and 3B, stimulating electrical impulses or signals may be generated and delivered via one of the electromagnetic energy elements and return signals sensed and recorded/monitored. As long as drill bit 24 is <BR> <BR> not in the vicinity of a critical nerve, e. g. , the inferior alveolar nerve 30, the return signals may be at or below a threshold 44, as seen in Fig. 3A. However, if drill bit 24 approaches the <BR> <BR> inferior alveolar nerve 30 within a predefined danger zone (i. e. , a predefined distance beyond which it is undesirable to get near the nerve), the return signals may comprise an action potential 46 propagated along the nerve that is above the threshold 44 (such as but not limited to, 70 mV), as seen in Fig. 3B. The action potential 46 may be caused by the electrode 20 in drill bit 24 disturbing the electromagnetic field sensed by the return electrode 26. The action potential 46 is recognized by controller 38 as a warning signal, whereupon controller 38 may emit a warning signal (audible or visual, for example) or turn off the drill assembly 12.

Thus, dental assembly 10 may be used to locate a nerve while drilling. The localization of the nerve may be used for the administration of regional anesthesia or to avoid cutting the nerve during drilling.

Reference is now made to Fig. 4, which illustrates a dental assembly 50, constructed and operative in accordance with another embodiment of the present invention. Dental assembly 50 is preferably similar to dental assembly 10, with like elements being designated by like numerals. Dental assembly 50 may comprise different features as is now explained.

For example, in dental assembly 50, one or more stimulator electrodes 20 may be external to drill bit 24, instead of being disposed in lumen 22. As another example, in dental assembly 50 one of the electromagnetic energy elements may comprise a magnetic member. For example, drill bit 24 may comprise a magnetic member 52 disposed in lumen 22 (alternatively magnetic member 52 may be external to drill bit 24). Magnetic member 52 may comprise without limitation a magnet made of samarium cobalt or neodymium-iron- boron or any other alloy with suitable magnetic properties. Magnetic member 52 may disturb the electromagnetic field sensed by the return electrode 26 and generate the action potential 46, in a manner similar to electrode 20 as described hereinabove.

In the above embodiments, one of the electromagnetic energy elements senses a modification of a property of an electromagnetic field as modified by the other electromagnetic energy element. The electromagnetic stimulation/interference gives rise to the action potential 46, which may be processed as the warning signal by controller 38.

After drilling a hole in the craniofacial region with drilling assembly 12, it may be desired to place an implant or other prosthetic device in the hole. Common materials used in prosthetic devices may include without limitation, ceramics, polymers and metals. Metals may include without limitation, titanium and titanium alloy, stainless steel, gold, cobalt- chromium alloys, tungsten, tantalum, as well as, similar alloys. Titanium is popular in the implant field because of its superior corrosion resistance, biocompatibility, physical and mechanical properties compared to other metals.

A significant drawback to titanium implants is the tendency to loosen over time.

There are three typical prevailing methods for securing metal prosthetic devices in the human body: press-fitting the device in bone, cementing them to an adjoining bone, such as with a methacrylate-type adhesive, or affixing in place with screws. All methods require a high degree of surgical skill. For example, a press-fitted implant must be placed into surgically prepared bone so that optimal metal to bone surface area is achieved. Patient bone geometry significantly influences the success of press-fitted implants and may limit their usefulness as well as longevity. Similar problems occur with cemented implants; furthermore, the cement itself is prone to stress fractures and is not bio-absorbable.

Therefore, all methods are associated to varying degrees with cell lysis next to the implant surface with concomitant fibrotic tissue formation, prosthetic loosening, and ultimate failure of the device.

Methods have been developed to promote the osteointegration of bone to metal, thereby obviating the need for bone cements. Osteointegration is defined as bone growth directly adjacent to an implant without an intermediate fibrotic tissue layer. This type of biologic fixation avoids many complications associated with adhesives and may result in a strong implant-to-bone bond. The present invention provides structure that may enhance osteointegration.

Reference is now made to Fig. SA, which illustrates dental assembly 60, constructed and operative in accordance with another embodiment of the present invention. Dental assembly 60 comprises an electro-osteogenic dental implant 62 (also referred to as a dental prosthesis, the terms being used interchangeably throughout the specification and claims).

Dental implant 62 may enhance osteointegration by means of an electrical current or field in the vicinity of the implant and neighboring bone 63, which current or field may promote osteogenesis.

Dental implant 62 may comprise one or more electrical current elements 64 adapted to generate an electrical current in the vicinity of implant 62. For example, as seen in Fig.

SA, electrical current elements 64 may comprise a plurality of galvanic cell elements disposed on implant 62. The galvanic cell elements may comprise at least partially annular elements 66 mutually spaced from each other on a periphery of implant 62. The galvanic cell elements may be constructed of metals with different electromotive potential, wherein in the presence of an electrolyte, such as but not limited to, intercellular fluid in the bone, an electrical field 68 is created in the vicinity of implant 62.

Alternatively, an implant 62'may comprise galvanic cell elements in the form of axial elements 70 mutually spaced from each other on a periphery of implant 62'. Fig. 6A illustrates a top view of the axial elements 70. It is seen that the axial elements 70 may be in direct contact with the outer contour of implant 62'. As seen in Fig. 6B, in an alternative embodiment, a resistor 72 may be disposed between one or more of the galvanic cell elements 70 and the contour of implant 62'. Resistor 72 may be used to control the current generated by electrical current elements 64.

Alternatively, the galvanic cell elements may comprise an at least partially annular element 74 and a plug element 76 screwed or otherwise inserted into an implant 62". The annular element 74 and plug element 76 may comprise metals with different electromotive potential, so as to create an electrical field 68 in the vicinity of implant 62".

Still alternatively, as seen in Fig. SB, the galvanic cell elements may comprise first and second galvanic elements 78 and 80, respectively. First galvanic element 78 may be disposed on a first electro-osteogenic dental implant 62A and second galvanic element 80 may be disposed on a second electro-osteogenic dental implant 62B spaced from the first implant 62A. A resistor element 82 may connect the two implants 62A and 62B. An electrical field 68 is created between the two implants 62A and 62B.

As another alternative, the galvanic cell elements may comprise a battery or any other kind of power source that may be placed or implanted in the body. The battery may serve as the electrical current element 64 that generates the electrical current in the vicinity of implant 62, or alternatively, the battery may enhance the electrical action of the electrical current element 64.

Although the assemblies of Figs. SA and 5B have been described with reference to dental assemblies and implants, nevertheless it is appreciated that the assemblies of Figs. SA and 5B may also be used as electro-osteogenic implants in any other portion of the body.

Any portion of the dental assemblies of Figs. SA and 5B may be biodegradable. The electrical current or field in the vicinity of the implant and neighboring bone may accelerate osteointegration as graphically shown in Fig. 7 at reference numeral 84, as opposed to osteointegration without the electrical current or field, as graphically shown in Fig. 7 at reference numeral 86.

As mentioned hereinabove, if there is insufficient bone height, such as insufficient alveolar bone height, augmentation of the deficient bone may be required in order to implant the dental prosthesis. One of the methods includes bone distraction, which generally involves cutting a bone and separating it in a controlled manner. However, distraction used in dental procedures generally requires a skilled dental surgeon and great care so as not to damage nerves in the region.

The present invention provides an alternative method for augmenting bone height, as is now described with reference to Figs. 8A-8C.

Fig. 8A illustrates a defect in the craniofacial region, such as but not limited to, a void 90 in the alveolar bone 91. The alveolar bone 91 is covered by the periosteum 92, a thick fibrous membrane covering the surface of the bone. In the prior art, the alveolar bone 91 is cut and lifted, a large periosteal flap is reflected and the area is eventually filled with bone substitute material. This is a delicate and dangerous procedure, which generally requires general anesthesia. In contrast, in the present invention, no bone need be cut. Rather the periosteum 92 may be lifted with a dental assembly 100, as is now described.

Dental assembly 100 may comprise an outer interface element 102 adapted to be <BR> <BR> fixed in a craniofacial structure, e. g. , the alveolar bone 91, as seen in Fig. 8B. Outer interface element 102 may comprise a threaded insert, and may have a receiving portion 104 formed therein (best seen in Fig. 8C). In the embodiment of Figs. 8B and 8C, receiving portion 104 comprises a cavity tapped with female threads.

An inner element 106 may be provided that is adapted to be received in receiving portion 104. In the embodiment of Fig. 8B, inner element 106 may comprise a shank formed with outer male threads that mate with the female threads of receiving portion 104. Inner element 106 may be selectively moved outwards of receiving portion 104. For example, in the embodiment of Fig. 8B, a coupling member 107, such as but not limited to, a bolt head with a male or female hexagonal head, may be attached to inner element 106. A turning tool 108, such as an Allen wrench or key or other equivalent tool, may be used to turn coupling member 107 so as to move inner element 106 in or out of receiving portion 104.

Inner element 106 preferably comprises a periosteum engaging member 110, such as but not limited to, a disc that extends peripherally beyond outer interface element 102. Inner element 106 preferably rotates independently of periosteum engaging member 110, so that when turning inner element 106 with turning tool 108, generally in the direction of an arrow 111, periosteum engaging member 110 does not turn therewith. As seen in Fig. 8C, as inner element 106 is moved outwards of receiving portion 104 generally in the direction of an arrow 112, periosteum engaging member 110 lifts the periosteum 92 away from alveolar bone 91, creating a volume 114. This volume 114 may then be filled, such as but not limited to by injection, with a bone filler material 116, such as but not limited to, bone morphogenetic proteins (BMPs), collagen, glycosaminoglycans, hyaluronic acid, polylactides, polyglycolides, polyanhydrides, polyorthoesters, polylactic and polyglycolic acid copolymers, BMP sequestering agents, and other osteoinductive factors which are enzymatically digested in the body. Additionally or alternatively, bone filler material 116 may comprise bone cells regenerated by osteodistraction through the callus.

Thus, dental assembly 100 may be used to augment bone height by lifting the periosteum 92 away from the alveolar bone 91. Outer interface element 102, inner element 106 and periosteum engaging member 110 may be made of a biodegradable material, such as but not limited to, polylactic and polyglycolic acid copolymers, for example, whereby dental assembly 100 biodegrades with time and is absorbed in the bone filler material 116.

Alternatively, outer interface element 102, inner element 106 and periosteum engaging member 110 may be made of a metal, such as but not limited to, titanium or a titanium alloy.

In the embodiment of Figs. 8B and 8C, inner element 106 may be rotated by means of coupling member 107 with respect to outer interface element 102. Reference is now made to Fig. 8D, which illustrates another example of a coupling member that conveys a force to dental assembly 100 that moves the inner element outwards of the receiving portion.

In the embodiment of Fig. 8D, a receiving portion 104'may be generally smooth, as well as the outer contour of an inner element 106'. A coupling member 107'may comprise a nipple for introducing a fluid 120 therethrough into receiving portion 104', such as via an aperture 122 formed through inner element 106'. The fluid 120 may comprise without limitation air or water, for example. Accordingly, inner element 106'may be moved outwards of receiving portion 104'with a pneumatic or hydraulic force. It is appreciated that these are just some non-limiting examples of apparatus for conveying a force to dental assembly 100 that moves the inner element outwards of the receiving portion.

The periosteal distraction system of the present invention may involve only a small periosteal incision and reflection, with no bone distraction. Bone substitute material may be introduced in a controlled manner, such as but not limited to, injection into volume 114. The procedure may require only local anesthesia and does not pose a risk to the inferior alveolar nerve, for example. There may be less post-operative discomfort due to the significantly less traumatic procedure of the invention.