ORTHODONTIC AND ORTHOPAEDIC JAWBONE ANCHOR

Abstract: Orthodontistry, and the manipulation of jaw growth, conventionally make use of apparatus fixed on anchor teeth. These teeth may move undesirably or may be absent, and alternatives include osteointegrated anchors such as that of EP-A-0818183 and anchors screwed into the bone such as that of WO-A9612451. Such anchors when placed in the palate necessitate a connection with teeth before the orthodontic/orthopaedic appliances can apply forces, and when fixed in the upper jaw make treatment difficult in the lower jaw. These disadvantages are circumvented by the present invention, whereby forces are applied via a horizontal connection piece (4) and a retentive part for elastic bands (5) on metal plates (1) fixed in the outer cortex of the jawbone, directly on the jawbone.

Description: ORTHODONTIC AND ORTHOPAEDIC JAWBONE ANCHOR The present invention pertains to an anchor that is fixed with screws under the periosteum in the jawbone and that serves as an absolute anchor for forces that are transmitted with orthodontic appliances to the teeth, or with orthodontic-orthopaedic appliances to the jaws themselves. The device is used in orthodontics, in dento-facial orthopaedics and in oral & maxillofacial surgery. It concerns patients whose teeth that are normally used for anchorage cannot or may not be loaded. In this way, the orthodontic force that induces wanted tooth movements (action) cannot lead to unwanted tooth movements (reaction) of the anchor teeth. It concerns also patients that are lacking anchor teeth. It concerns also patients where the jaw developement is manipulated with extra-oral appliances and where tooth movements are not desired. The list of indications is not limited. The assets of this invention compared to the appliance of HOFFMAN and KVARNSTROM (EP 0818183 A2 19980114, EP 0818183 A3 19980729, EP 97850112 19970707 and US 679358 19960711), are that the fixation in bone is secured by means of screws, and not by osseointegration onto the bony surface. The magnitude, the speed and the the direction of the load is therefore less delicate. The bone anchor can also be put in any place on the outer circumference of the upper- and lower jaw. The device of HOFFMAN and KVARNSTROM can only be put on the palate, which limits the applications. A third asset is that the forces are applied directly to the bone anchor, and not indirectly via a palatal bar on anchor teeth. It has the asset compared to the device of ASIKAI- NEN, SUTTER, MUNDWILLER, MERZ, WEHRBEIN, GLATZMAIER, HAUSMAN and HUSKENS (WO 9612451 Al 19960502), that the fixation can be everywhere on the outer circumference of the jawbone, and that it is not limited to the central part of the palate, where a suture is located with growth ability, and that the force application can be directly, and not secondary via anchor teeth. This is realised according to the invention because the bone anchor has the features as described in the appended claims . Preferably, the bone anchor comprises: a fixation plate, that is fixed underneath the periosteum with screws in the jawbone; a bendable vertical arm that is immediately, or during a second surgical phase, brought in the oral cavity through the soft tissues or mucous membrane; and a, preferably horizontal, connection piece (bracket, tube) that can contain an orthodontic arch wire or the fixation arm of a headgear appliance, with or without blocking system. In addition, the bone anchor may comprise a tool to fix an elastic band. The fixation with screws on the outer surface of the jaw permits to place the bone anchor at any given position on the outer circumference, also when teeth are present in that area. At that moment, only the screw length needs to be adapted. The vertical arm can be bend when the bone anchor is placed, or later, in a way that the part that receives the orthodontic or orthopaedic forces by means of an activated arch wire, an elastic band, an extra-oral traction device, can be put in an ideal anatomic and functional position. The load can be applied immediately, when it is small, or after osteointegration, when it is bigger. The horizontal connection piece, that is located transver- saly on top of the vertical arm, can have different dimensions (length, diameter) , according to the application. A blocking system can be placed in the connection piece. The retention for the elasctic traction can be in hook shape, in T-shape, or an indent in the vertical arm can be used. Preferably, the apparatus is made of titanium. This material is well known for its optimum biocompatibility, both for incorporation into the bone (osteointegration) and for incorporation into the soft tissue parts (mucous membrane) . No allergies to titanium have been described. These and other characteristics of the invention will emerge from the following description, in which reference is made to the appended drawings, which show an exemplary embodiment of an apparatus according to the invention, and in which: Figure 1 shows a front view of a bone anchor, without fixation screws, fixed at the lateral side of the upper jaw according to the invention on a scale of 2:1; Figure 2 shows a side view of a bone anchor on a scale of 2:1. In these figures, identical numerals refer to identical or similar elements. A bone anchor is fixed in the jaw bone by means of a surgical intervention, to use as an absolute anchorage for forces that are transmitted by orthodontic or dentofacial orthopaedic appliances to the teeth or to the jaws. The bone anchor depicted in Figure 1 and 2 serves for the rigid anchorage in the jaw bone by which undesired movements can be prevented of teeth that would otherwise be taken as anchorage, and as a replacement for anchor teeth when these are absent, and for application of orthopaedic forces directly to the jaw and not via the anchor teeth. It comprises following parts: a fixation plate 1, fixed with screws in bores in the outer surface of the jaw, by means of a system of holes 2, whether linear, or complex and multidimensional positioned; a vertical arm 3, in different lengths; a horizontal connection piece 4, of variable dimensions, with or without locking screw; a retention mechanism for elastic bands.

Claims: CLAIMS 1. Bone anchor to prevent undesired movements of anchor teeth, in replacement of anchor teeth that are absent, and for the application of orthopaedic forces to the jaw bone, without having to resort to teeth for an anchorage, comprising: a fixation plate (1) , with bores (2) for being screwed in the outer surface of the jaw bone; a vertical arm (3) for penetrating the soft tissues (mucous membrane) and coming in the oral cavity; a connection piece (4) , varying in dimensions according to the function, with or without a blocking screw; and a retentive part for elastics (5) , preferably in the shape of hooks or T-shaped extensions, or via indents in the vertical arm. 2. Bone anchor according to claim 1, wherein the connection piece (4) extends horizontally, in particular transverse to the fixation plate (1) . 3. Bone anchor according to claim 2, wherein the connection piece is a tube (4) , which preferably extends horizontally. 4. Bone anchor to prevent undesired movements of anchor teeth, in replacement of anchor teeth that are absent, and for the application of orthopaedic forces to the jaw bone, without having to resort to teeth for an anchorage, comprising: a fixation plate (1) , with bores (2) for being screwed in the outer surface of the jaw bone; a vertical arm (3) for penetrating the soft tissues (mucous membrane) and coming in the oral cavity; and a connection piece (4) , such as a bracket or a tube, for orthodontical wire. 5. Bone anchor according to claim 4, further comprising a a retentive part for elastics (5) , preferably in the shape of hooks or T-shaped extensions, or via indents in the vertical arm. 6. Bone anchor to prevent undesired movements of anchor teeth, in replacement of anchor teeth that are absent, and for the application of orthopaedic forces to the jaw bone, without having to resort to teeth for an anchorage, comprising: a fixation plate (1) , with bores (2) for being screwed in the outer surface of the jaw bone; a vertical arm (3) for penetrating the soft tissues and coming in the oral cavity; and a retentive part for elastics (5) , in the shape of hooks or T-shaped extensions, or via indents in the vertical arm. 7. Bone anchor according to claim 6, futher comprising a connection piece (4) for orthodontical wire. 8. Bone anchor according to any one of the claims 1-7, characterised in that the forces apply directly to the bone and not via the teeth. 9. Bone anchor according to any one of the claims 1-8, characterised in that it can be placed circumferentially on the outer cortex of the upper- and lower jaw, without having to count with the presence of teeth. 10. Bone anchor according to any one of the preceding claims, wherein the arm is bendable.

Inventors: MOMMAERTS MAURICE YVES, MOMMAERTS, MAURICE, YVES
Applicants: MOMMAERTS MAURICE YVES, MOMMAERTS, MAURICE, YVES
Application year: 2001
Main classification: A61B17
IPC codes: A61B17, A61C7, A61C8