The present invention pertains to a distraction device used to widen an upper jaw (maxillae) after osteotomy and fixation of an adjustable bridging onto the bone of the palate with the goal to gradually increase the distance between the two mutually opposite halves of the jaw.
The device is used in maxillofacial surgery, in particular in orthognathic surgery in patients with narrow maxillae. It concerns a developmental disturbance, sometimes congenital as in cleft lip and palate, that can lead to a cross-bite, tooth crowding, hindered nasal breathing, a disturbed occlusion with the lower dental arch, and a psychosocial aesthetic problem. The aim of the invention is to restore the dental occlusion, to improve nasal breathing and to bring the face into normal proportions.
The assets of this invention compared to tooth-borne appliances (that are patented by Leone, Schellino and Modica (EP 0846446), by Palmisano (WO 9629964), by Bernhard Förster (WO 9628110 and WO 9810708), by Klapper aand George (EP 0706349), are that there is no or less rotation of the jaw segments in the frontal plane by its high level of force application, that it results in orthopaedic and not orthodontic expansion, that dento-alveolar relapse is not to be expected during and after the expansion, that the interchangeable expansion- modules allow to continue expansion without having to resort to the fabrication of a new appliance, and that the orthodontist has all teeth available to start with active orthodontic treatment before the stabilisation period has ended.
This is realised according to the invention because the device has following parts;
two abutment plates, that are fixed to the palatal bone (processus palatinus ossis maxillaris), whether with screws into drill holes (as in current description) or with other means such as pins, left and right under the soft tissues;
a box-like extension, provided by a slot (in current description) or another hinge mechanism to fix the distraction module into or onto. The extension pierces the soft tissues;
expandable parts (distraction modules) of different lengths, in current description four, with at both sides connections possibilities (in current description wings) that fit into or onto the extension of the abutment plates.
The distraction module comprises a telescopic screw. The telescopic screw allows the distraction section to be kept compact, leading to a greater stretching with a small initial length. Modules of different lengths allow to choose in the individual case for the proper initial size, and, in the current description, to change for a bigger size when deemed necessary.
The screws or pins used to fix the abutment plate to the palate have appropriate lengths in order to avoid damage to the roots of the teeth.
After a latency period of four to seven days, activation can start, by 1/3 mm daily. After a distraction period of one to two weeks, and a stabilization period of one to three months, the orthodontist can start with fixed orthodontic appliances. One or two months later, the apparatus is removed. Complete bony consolidation occurs in the median vertical distraction area and in the lateral horizontal distraction areas.
Advantageously, the expansion screw is a mechanical jackscrew, which comprises three parts which fit into one another, the central segment having the largest diameter, in order to act as a connecting sleeve, and being provided at its ends with internal turns of opposite direction and different sizes, into which two mutually opposite telescopic arms fit, which are able to move into one another and have virtually the same length as the connecting sleeve, so that they can move completely into and out of the central connecting sleeve.
The flat conical shaped wing (in the current design) at one of the sides of the telescopic arm allows the distraction module to be fitted into the extension box of the abutment plate.
A colour or form code on the connecting sleeve allows to control the speed of the gradual stretching.
Three bores with thread at one side of the connecting sleeve allow to block the movements of the module with a blocking screw.
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. No allergies to titanium have been described. Dimetalosis has been ruled out.
The most characteristic item of the invention is the application of the expansion force directly onto the bone, and not indirectly over the teeth.
3. Distraction apparatus according to one of the proceeding claims, characterised in that the expansion screw (3, 4, 5) is a mechanical jackscrew, which comprises three parts which fit into one another, the central element having the largest diameter, in order to act as a connecting sleeve (5), and being provided at its ends with internal threads of opposite direction and different sizes, into which two mutually opposite telescopic arms (3, 4) fit, which are able to move completely into and out of the central connecting sleeve (5).