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31 Mar 2015 | Australasian Dental Practice

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New i-expander: Simple expansion for pre aligner therapy

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When diagnosing patients for minor orthodontic treatment, especially aligner therapy, one often finds "crowding" to be an issue and the ability to "create space" as a solution can be challenging. The three common methods to create space are:

  1. Expansion;
  2. Inter-Proximal Reduction (IPR); or
  3. Extraction.

All three have their place but nowadays, extraction has become a contentious treatment approach, especially when the patient is primarily after a "cosmetic fix". This leaves either expansion, IPR or a combination of the two as a very viable, conservative option.

Arch expansion has been around for a long time. Hippocrates recognised a narrow maxilla and various slow expansion techniques were employed by early dental practitioners such as Fauchard and Bourdet in the 1700's and Fox, Delabarre and Robinson et al in the 1800's.

During the late 1800's in the USA, there was much controversy about arch expansion and Rhinologists were best known for this sort of treatment. Some of the most famous expansion appliances include the Coffin Plate; The Schwartz plate; the Quad Helix; and the RME.

The three types of expansion are orthodontic, passive and orthopaedic:

  • Orthodontic expansion relates to the movement of the teeth through the alveolar bone;
  • Passive expansion occurs when the teeth are shielded from the surrounding musculature, for example when using a Frankel functional appliance; and
  • Orthopaedic expansion is often associated with rapid palatal expansion where the mid palatal suture is separated and the underlying skeletal structures are modified. This is often done without surgery, however surgically-assisted distraction is also used.

Often, dental appliances combine these Three types of expansion and removable expansion appliances are a good example of appliances that can combine at least 2 of theses types of expansion.

Introducing the i-expander

The i-expander is a simple, removable device that can be used for steady transverse expansion of either arch and it overcomes a lot of design problems that traditional removable expanders incur. Firstly, it is made from high strength, pressure-formed polycarbonate and comes standard with a surgical grade stainless steel expansion screw. A titanium screw is available as an option for nickel sensitive patients. The i-expander utilises a clasp-less design as the polycarbonate shell covers the posterior teeth, just over the gingival margin, giving the appliance superior retention in the mouth and making it very comfortable for the patient. This covering of the teeth and also lingual areas of the anterior teeth stops super eruption of the arch and of the opposing arch.

It is an inconspicuous appliance that is hard to detect in the mouth, so, as the name suggests, i-expander is short for invisible expander. Speech can be affected, but the patient will adapt in a matter of days.

The invisible nature of the device is another reason it is popular amongst patients as a precursor to clear aligner therapy.

Activating the appliance is simple. For every complete turn of the expansion mechanism, 1mm of expansion is achieved. Because this is a slow and steady expansion device, the ultimate goal is 1mm of expansion per month and this is achieved by 1-quarter turn of the mechanism, a movement of 90o, per week. Some practitioners have suggested an adjustment twice per week, but you have to be careful and evaluate case-by-case as over adjustment can cause dislodgement of the appliance or in some rare cases, excessive pain. Either way, too much adjustment too quickly will not give satisfactory results.

The appliances are often worn for 3-4 months and can achieve a good 3mm of development, usually enough room to start Truline invisible appliance therapy. In fact, the i-expander was specifically developed for pre-Truline aligner therapy. Its use prior to commencing aligner therapy reduces the overall treatment time and cost as the number of aligners required is significantly less. It can work very well in adult patients and is ideal for younger patients as well for general orthodontic expansion.

Patient compliance

The essential ingredient to the success of the i-expander is patient compliance, so 24 hour a day wear gives best results. Part time wear will yield no significant results except frustration for the practitioner. Some patients wear their appliance sporadically and need to wind the appliance back to get it to fit if it has been out of the mouth for some time. Be aware screw mechanisms are designed to be one use only. What is meant by this is that continual winding forward and back by the patient damages the mechanism, causing it to become loose and hence it will not hold the expansion correctly and will often cause self wind-back. The appliance needs to be replaced in these circumstances and ridged compliance resumed for success.

i-expanders must be removed for meals, brushing and flossing, sporting activities and any situation where it would be unsuitable to wear the appliance.

Cleaning the appliance is simple. Using a soft toothbrush and a mild detergent is often all that is needed as long as cleaning is done regularly. Other products specific to orthodontic appliances can be used as cleansers and calculus removing products are especially useful.


The i-expander can be order digitally by supplying an intraoral scan that includes at least half of the anterior palate or simply supply a traditional PVS impression or stone model.

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