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Rapid Maxillary Expansion

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					                    Rapid Maxillary Expansion (RME)
Rapid maxillary expansion (RME) is a technique which aims to correct transverse maxillary
discrepancies by producing a sutural expansion at the mid-palatal suture by application of
high forces. It is commonly used for treatment of posterior crossbites especially where
maxillary discrepancy is 4 mm or more. RME is carried out during or before the pubertal
growth spurt (below age 15 years) as after this period the intermaxillary suture closes, leading
to skeletal resistance to this procedure.

An expander is a rigid appliance that consists of either metal rings fixed to posterior teeth
(banded RME) or acrylic splints over several teeth ( bonded RME) joined by a wire
framework attached to a screw in the midline which is turned daily (1/4 turn twice a day).
After obtaining the required amount of expansion (2-3 weeks of active treatment) the
expander is kept in place for a retention period of 3-6 months in order to stabilize the
outcome of the procedure.




There is no evidence to suggest that banded RME appliance is more effective than bonded
appliance or vice versa, however, oral cleaning is easier with the banded expander.

Occlusal maxillary radiographs can be taken to monitor the process of expansion. A
triangular radiolucency is created following the separation of the maxillae. The patient should
be warned about the midline diastema formation during the procedure, though this will
usually close during the retention period.
There are reports that RMEs may also be an aid in alleviating nasal airway constriction that
may have contributed to constricting the maxilla in the first place, however, the effect can
vary from no appreciable change to marked improvement, depending on the cause, location
and severity of nasal obstruction.

In comparison to slow expansion appliances such as Quad Helix, RME delivers a greater
degree of skeletal movement and also leads to less tipping of the molars which could damage
their periodontal health and possibly create a posterior open bite.

One study evaluated the long-term changes in the dental arch dimensions in adolescent
patients treated with RME using a Haas-type expander (112 subjects were evaluated 6.1 years
after completion of their treatment). It found the average of 3.7mm width gain in maxillary
intermolar and interpremolar regions and 2.2mm gain in the intercanine region. For the
mandibular teeth the intermolar width gained was 5.4mm and intercanine width was 1.8mm
compared with the control group.

It has been suggested that after initial treatment there is a continual relapse of the dental and
skeletal expansion for up to 5 years.




                                         References
   1. D. Gill, F. Naini, M. McNally, A. Jones. The management of transverse maxillary
      deficiency. Dental Update 2004; 31: 516-523
   2. Manuel O, Paul W, Carlos Flores-Mir. Long-term dental arch changes after rapid
      maxillary expansion treatment: a systematic review. Angle orthodontist. 2005;75:155-
   3. Harrison J.E, Ashby D. Orthodontic treatment for posterior crossbites. Cochrane
      Database of Systematic Reviews 2001.

				
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posted:11/8/2011
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