GB2495554A - Dental model repositioning articulator attachment for use in production of orthognathic wafers - Google Patents

Abstract

The device has five movable plates 1 5 and is an attachment for a dental articulator 9. It is situated between the articulator arm 10 and a cast dental model 12 for use in the production of intermediate and final wafers for orthognathic surgery. The top plate 1 is fixed to the articulator and has an interlocking engagement with plate 2 permitting relative motion along the anterior posterior axis. Plate 2 similarly interlocks with plate 3 but provides left and right lateral movements. Plate 3 provides left and right rotational movements which are measured on a scale 8. Plate 4 is connected to plate 5 using three equidistant screws 6. The screws vary the spacing between plates 4 and 5 for impaction and distraction movements. All five plates can be secured in place by tightening a lock washer (14, figure 2) on a locking bolt (13) which extends through the centre of the plates.

Description

DESCRIPTION

MODEL REPOSTIONINCI ARTICULATOR ATTACHMENT

Orthognathic surgery involves the repositioning of the dental arches in relation to the facial skeleton by cutting through the maxilla and then using an acrylic inteimediate wafer made by the dental technician to establish the new position of the maxilla in relation to the mandible then holding this new position with use of plates and screws directly into the bone (osteotomy).

The movements needed are anterior! posterior, left and right lateral, rotation, impaction, distraction/extrusion. In a hi-maxillary osteotomy the mandible is also cut and repositioned to the maxilla by use of the final wafer constructed by the dental technician.

To obtain these acrylic wafers there are various techniques for the dental technician (known as model surgery), the most popular being the Eastmans technique and the Lockwood keyspacer technique The Eastmans technique involves measuring the vertical distances from the tips of the buccal cusps of three reference teeth and the central incisor tips on the maxilla to an reference line draw on the mounting plaster. The planned movements of the maxilla are then marked onto the mounting plaster. The mounting plaster is then cut along the osteotomy line and repositioned by eye according to the planned markings to show the final position of the maxila. This is then secured with wax.

The Lockwood technique involves the same measuring procedures but with the use of plaster key spacers between the mounting plaster and model base to locate the models post and pie operation.

The problem with both of these techniques is that they are not accurate because of the nature of the way the movements are made.

The invention is a means of repositioning plaster cast dental models on a dental articulator for the for use in orthognathic surgery by using five plates to emulate the movements made in said surgery.

The invention is an attachment for existing articulators and locates between the upper arm of the articulator and the plaster cast dental model (where the mounting plaster would be)(Figure I) and allows all movements needed to emulate surgical position of the maxilla for construction of the intermediate and final wafers by the dental technician.

The invention has measuring rulers on areas of each plate 8 The invention has a locking cylindrical bolt 13 that passes through plates 1,2,3,4 that is fixed at the top of plate I and is locked under plate 4 with a threaded washer i4 to obtain non movement of said plates when new position is obtained.

The invention will now be described solely by way of example and with reference to the acconipanyi ng drawings in which: Figure i shows the inventions location between the articulators aim and the cast dental model Figure 2 shows the invention in its separated component parts I plate I 2 plate 2 3 plate 3 4 plate 4 plateS 6 adjustment screws 7 center line 8 measuring rule 9 articulator 1 0 articulator arm 11 articulator fixing screw 12 cast dental model 13 lock bolt 14 lock washer articulator fixing locators 16 plate holes for bolt 17 retention matrix 18 rubber washers 19 trapezium platel trapezium plate 2 top 2ltrapezium plate 2 bottom 22 trapezium plate 3 top 23 circular protruding shape plate 3 bottom 24 circular recess plate 4 top screw disk Plate 1 consists of mounting holes 15 that allow it to be fixed to the articulator on the top, and a trapezium shape 19 on the bottom that allows attachment of plate 2. fixed to plate 1 a cylindrical bolt 13 protrudes from the centre of the bottom of the plate and passes through plates 2,3,4 the terminal end of the cylindrical bolt has a screw type thread Plate 2 has a trapezium shape 20 on the top that allows it to fit into plate 1 and is able to provide anterior and posterior movement in conjunction with plate I and has a measuring rule 8 on the top. It has a trapezium shape on the bottom 21 that allows attachment of plate 3. It has a rectangular hole 16 in the centre of the plate to allow the cylindrical bolt 13 to pass through it but still maintain said movement of plate Plate 3 has trapezium shape 22 on the top that allows it to fit onto plate 2 and is able to provide left and right lateral movement in conjunction with plate 2 and has a measuring rule 8 on the top and on the front. It has a circular shape 23 that protrudes from the bottom that allows attachment of plate 4. it has a square hole 16 in the centre of the plate to allow the cylindrical bolt 13 to pass through it but still maintain said movement of plate Plate 4 has a circular shape 24 on the top recessed into it that allows it to fit into plate 3 and is able to provide left and right rotational movements in conjunction with plate 3 and has a measuring rule S at the front. It has three points about the sides of the plate which are apart and to which are attached a screw mechanism 6 that allows attachment of plate 5. it has a square hold 6 in the centre of the plate to allow the cylindrical bolt 13 to pass through it but still maintain said movement of plate. the terminal end of the bolt passes through a disk type washerl4 that is larger than the square hole in the centre of the plate and has a thread and is able to be tightened to lock the plates into their desired position Plate 5 has three points about the sides of the plate which are apart that allow attachment to plate 4 with use of said screw mechanism 6. Using the screw mechanism it is able to (in conjunction with plate 4) provide impaction and distraction/extrusion movement in any of the said three positions. It has a measuring rule 8 attached to each location of said screw mechanism 6 which protrudes vertically to plate 4. The bottom of plate 5 has means of retention by using a matrix 17 to hold a dental cast model. The screw mechanism consists of a small disk 25 positioned in the middle of the screw and when turned is able to open and close the space between plates 4 and 5. There are rubber washers I S at the end of each screw that separate the screw from the plates 4 and 5 and are attached to the plates 4 and 5. This enables some degree of differing measurements to be obtained in the space between plates 4 and 5.

The invention solves the problem of the inaccuracy of the culTent practice in model surgery.

With the current technique. measurements are taken and the cast model is marked with two sets of vertical lines to show the current position and the required position. The model base is then separated and the technician attempts to move the rnodd to the new position by matching up the old position lines on one part of the model to the new position lines on the other part of the model thus producing the movements required. However this is not accurate because when one movement is made, it can then be accidentally altered by the second movement and third movements. The invention solves this problem of accidental movement.

the invention also solves the problems associated with marking the models accurately as the models do not need to be measured.