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the model preparation is complete it is usually good practice to fabricate the active
components first. In this case the palatal spring. This spring is constructed of
0.8mm hard stainless steel round wire, using Adams universal spring-forming pliers.
It is good practice to round the free-end of the spring before it is turned back
on itself. Note the free end of the spring is turned vertically as this will provide
the patient with a means of tactile positioning of the spring once it is activated
and the appliance is inserted. The tag should be kept clear of the midline suture
as this is where the appliance is to be split facilitating arch expansion.
The finished spring is waxed into position as shown. It should be orientated relative
to the central incisors, so that once activated it acts at near 90o to the palatal
aspect of the tooth surface. This will reduce the problem of having the spring ride
up the palatal aspect of the teeth rather than directing force at the teeth.
Wax should not be built up any higher than the surface contour of the spring, however,
ensure the free-end is covered as shown.
The Adams clasps should now be fabricated. I usually start
with the first molars and I have used 0.8mm hard stainless steel round wire as recommended
in H.R. Ortons publication titled "Functional Appliances in Orthodontic
The finished Adams clasps should be constructed as shown, remembering to allow sufficient
space between the tages to allow for the positioning of the vertical stops. The
finished clasps are now waxed into position on the model. Note to finish wax under
the tags where they extend over the interstitial areas during baseplate fabrication.
This is of greater importance where Adams clasps are used in conjunction iwth posterior
The Adams clasps are fabricated on the first premolar teeth
and waxed into position as shown. These Adams clasps are fabricated using 0.7mm
hard stainless steel wire. Remember to leave some space between the tags to facilitate
placing of the vertical stops.
The vertical stops are now fabricated as shown using 0.9mm hard stainless steel
round wire on the first molars and 0.8mm on the first premolars.
! Remember to round-off the
tips of the wire
A strip of wax is softened to form to the occlusal and labial surfaces of the teeth
and sealed to prevent overspray. Similarly for the posterior border. The expansion
screw is placed in position with the application of wax at the plastic tag/model
The model is immersed in water for 10 minutes. It is then removed and any excess
water blown away from the palatal surface. Using the 'salt and pepper' technique,
the acrylic resin is applied to the surface quadrant by quadrant until the desired
thickness is achieved. The anterior bite plane is built up to the desired height.
Once the acrylic resin application is complete, the resin is cured according to
the manufacturers instructions.
The wax is bioled away and the appliance is then removed from the model. The plastic
tag is removed from the baseplate as shown.
The baseplate is trimmed and smoothed in the usual way. You may have received technical
instructions from the clinician requesting the baseplate be selectively trimmed
as shown. In this case the baseplate is cut away from the laterals and the mesiopalatal
surface of the canine. The clinician may request that this trimming be carried out
at the chairside if possible.
Using a fretsaw blade, the baseplate is cut following the midline suture. In this
case in line with the bite plane down until you are through to the the palatal screw.
! Take care not to distort
Detach the blade from the body of the saw at one end and thread it through the hole
you have cut previously, distal to the spring. Re-attach the saw blade and cut the
rest of the anterior part of the baseplate down the midline. You will need to repeat
the process in order to remove the saw.
Finally, cut the acrylic baseplate distal to the expansion screw.
The appliance is now pumiced and polished to a high polish. The appliance is thoroughly
cleaned and the screw is closed. Check the upper polished surface is smooth and
free of sharp edges, minimising the risk of irritation.
Lightly polish the fitting surface to remove only the sutface roughness
but remove minimal surface detail. This is done to prevent palatal irritation and
substantially increases the patient ability to keep the appliance clean and hygenic.
Finally, place the appliance on the model ready to go to the surgery / dental office.
! Dont forget to supply a
screw activation key with the appliance.