The impressions are then disinfected again (as part of laboratory protocol) and cast in the usual way.
After the impressions are cast. The models are trimmed and the bases scored as shown. You may trim models in articulation to ensure both upper and lower models fit (with protrusive wax bite in position) between and parallel with the articulator 'arms' and this will also ensure easy removal from the articulator.
It may be necessary (depending on the type of blow down machine used) to use a split articulating technique. See appendix A (2) for reasons why.
In this case the wax bite has a protrusion of approx 5mm and a small vertical dimension of 4-5mm. Generally, an arbitrary protrusive bite is taken (similar to the one shown) and it is the clinician's discretion as to the amount of protrusion and vertical space a
The models are placed into the wax bite and articulated in the usual way. Here, a single hinge articulator has been used.
The models are prepared by removing any anomalies, using a Ash 5 / 9 or similar and blocking out any major undercuts if necessary.
The models are then Cold Mould Sealed in the usual way. It is not necessary to CMS the articulating plaster.
To prevent the lead free pellets (used in the next stage) from blocking the articulator holes using some paper towel as shown.
Here, the lower model is invested in the lead free pellets. Ensure to build the pellets up the 'heels' for the model and there are no 'loose' pellets on the opposing metal sealing ring.
A Biostar machine is been used here. The picture shows the invested model and EVA blank in position. A 4mm blank is used for both upper and lower models.
The heating element is then moved over the EVA blank.
The Biostar machine will alert us as when to close the chamber over the invested model and the locking arm should be moved in to position.
The chamber will be held under a air pressure during the cooling phase.
The Biostar machine will again alert us as when to evacuate the chamber and the formed blank and model are removed from the machine.
N.B. The same process is then carried out for the upper model.
Both upper and lower blanks are then ready for the trimming stages.
The excess blank material can be removed using scissors or using a scalpel heated in a Bunsen Burner flame.
Shown are the upper and lower blanks with the excess removed and ready for sealing together.
N.B. If there is a space between the upper and lower blanks, it may be necessary to 'fill' these spaces with either extra EVA blank material or by using a fusing gun with fusing pins / rods. (see appendix A (3) for further information).
Also see Appendix A (4) regarding reverse articulating in conjunction with using the fusing gun.
In this process an electric hot air gun is used to heat the occlusal surface of both blanks.
A hot air gun is used, as opposed to a flame gun, to prevent oxides from the flame coating the joining surfaces of the blanks and thus preventing an efficient seal between the two.
The hot air gun is held approximately 1-2 inches away from the blank / occlusal surface of the teeth and moved in a continuous motion over both upper and lower blanks / occlusal areas (and only the occlusal areas).
N.B. Do not hold the hot air gun in one place over the blank for an extended period of time as this may result in burning / distortion of the already formed blank.
Once the blanks are heated until they are 'sticky', they are placed on the articulator and carefully closed together.
This picture shows the upper and lower models / blanks closed together. The models / blanks and articulator are immediately quenched in cold water and allowed to cool for approximately 3 minutes.
Once cooled, the appliance is then ready for trimming. Firstly, the models are removed from the articulator and then (in this case) three air holes are made. As shown.
The periphery of the appliance is then trimmed using a rough bur, removing an sharp edges.
The periphery is then smoothed using a polishing bur.
These pictures show the final 'glossing' of the appliance. In this process, the periphery of the appliance is flamed (using a pen flame or similar) and quenched in water to prevent distortion. (see Appendix A (5) for further details on pen flame and hot air gun usage).
Quenching of the appliance during the flaming process. Please note that the flaming and quenching is done in small stages. For example, you should flame about 1-2 inches of the periphery of the appliance and then it is quenched. This is repeated until a 'gloss' is attained over the whole periphery.
The finished Sleep Apnoea Appliance (buccal view).
The finished Sleep Apnoea Appliance (labial view).
The finished Sleep Apnoea Appliance (lingual / palatal view).
(2) A split articulating system may be used depending on the type of blow down machine been used. In this particular case a Bio Star machine has been used and therefore we are able to invest the model and articulating plaster in the lead free pellets. However, certain machines do not have this 'function' and therefore it will be necessary to separate model and articulating plaster, place the model on the 'platform' of the machine, carry out the blow down stage, remove the excess blank material and then 're-articulate' prior to joining the upper and lower blanks together.
Alternatively, it is possible to blow down the blanks on the upper and lower models, remove the blanks from the models, then articulate the models and then replace the blanks prior to joining the two together.
(3) If there are spaces between the upper and lower blanks, it may be necessary to
'fill' these spaces with an extra piece of EVA blank. This is done by simply heating the upper and lower blanks with the hot air gun (as shown), heating an extra piece of EVA blank in the same way and sandwiching this between the already formed upper and lower blanks. The 'filling' material can be trimmed and smoothed in the same way as the periphery.
Alternatively, a fusing gun with fusing pins / rods may be used to not only 'fill' any spaces between the upper and lower arches, but to also join the upper and lower blanks together. If this technique is going to be used, then it may be necessary to reverse articulate the models in the initial stages. (see Appendix A (4) for details).
(4) The reason it may be necessary to reverse articulate is to enable us to gain
access to the palatal and lingual areas of the appliance and smooth these
surfaces efficiently.
(5) In this particular walk through, a pen flame has been used to 'gloss' the periphery of the appliance. It is also possible to use a hot air gun (with a fine / narrow applicator nozzle) to 'gloss' the periphery. In both cases it is important to ensure no distortion of the appliance, by repeatedly quenching in cold water.
