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Construction of Expansion & Labial Segment Alignment Appliance (ELSAA)

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Patient has presented with full unit buccal Class II and a deep overbite. The incisors are typical Class II Division II relationship with retroclined central incisors and proclined lateral incisors. The objectives we want to achieve with appliance are :

  • Expand the buccal segments
  • To use the expansion to round out the labial segment (selective trimming of the baseplate may be necessary)
  • Where labial teeth are proclined outside the final expanded arch position the combination of the bite plane, selective trimming of the baseplate and lip forces will bring these teeth back into alignment.
  • Maintain the vertical height of the buccal teeth allowing eruption of the lower buccal teeth, so reducing the deep overbite.
  • Activation of the palatal spring will produce proclination of the upper central incisors ultimately turning a Class II Division II incisal relationship into a Class II Division I relationship.
  • The appliance when used as a pre-functional should facilitate the use of medium open activator or similar without the need for further buccal expansion during the myofunctional phase of treatment.

Photography © P.A. Mallett 1999

The appliance may be constructed using either heat-cured acrylic or cold-cured acrylic. In this walkthrough we are using the cold-cured method. It should be noted that most modern cold-cured resins have adequate strength and wear resistance in use and is suitable in this use. The construction details follow ....
The first premolars and first molars should be assessed as to whether there is sufficient undercut on the mesiobuccal and distobuccal aspects of the teeth at the level of the gingivae. If there is insufficient undercut then following the contour of the tooth surface trim the gingivae remembering not to exceed the phsiological limits by over-trimming. I try to keep any trimming to within 1mm, however, the extent of trimming is purely subjective.The over-riding objective of this trimming is to provide sufficient purchase for arrowheads of the Adams clasps which ultimately provide fixation for the appliance.

Once 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 Treatment"

 


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 bite blocks.


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 interface.


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 the wire.


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.