The original model is retrieved from storage and the upper twin block checked on the model for wire work distortion etc.

The Mid-line screw is removed from the upper twin block and the edges of the appliance roughened with a trimming bur.

The Adams clasps and labial bow are adjusted from their distorted position to their ideal position.

The mid-line screw is then placed into the palate and lightly secured with wax as shown.

The upper twin block is sealed to the model and a ribbon of wax is also positioned and sealed in the buccal and posterior areas of the model to aid the concentration of the new acrylic in one area. The model and appliance are then soaked in water for approx 10 minutes.

The appliance is then sprayed and cured in the usual method.

The cured upper twin block after the wax has been 'boiled' away and ready for the mid-line screw 'positioning plastic' to be removed and the appliance to be trimmed, smoothed and polished in the usual method.

A variety of burs are used to trim and smooth the upper twin block.

A pencil line may be drawn on the appliance as a guide for sawing the mid-line.

The sawing of the mid-line is performed and the mid-line screw is opened to facilitate smoothing of the sharp edges on the lathe.

The completed repaired upper twin block.