Wednesday, 23 March 2011

Bone Anchored Maxillary Protraction of Growing Class III Patients, EuJO

The traditional protocol for maxillary protraction of growing class III pre-pubertal patients would be expansion and loosening of the mid-palatal suture with the means of a Hyrax appliance. That will be followed with 5-7months (more depending on the severity and patient compliance) of protraction with a facemask, with a force of 300-400gr elastics (8-14oz). The optimal use of the facemask would be 14-16h/day.

The latest issue of European Journal has an article from distinguished  researchers, such as Bachetti, Franchi, Cevidanes, Clerck, from Florence, Michigan, and North Carolina university. In this article the effects of a different protocol using bone anchored mini-plates, and lighter force (progressive increase 150-200-250gr) Class III traction is analyzed.

The authors have a group of 26 growing children with a dental-skeletal Class III, matched with a 16 untreated control group of similar age and malocclusion. 

The link for the abstract.

The results, dictate that: 

  • The effect of correction of the Class III is in both jaws, with a more pronounced effect in the maxilla. 
  • Also in the vertical the effect measured is minimum.
This is the insertion site for the two miniplates

The traction is started with a 150gr elastics for the first month, 200gr the second month and 250gr afterwards. Also in most of the cases a plate is used to disocclude and allow for the lower front to shift to a normal overjet over the upper front.

This technique certainly shows potential

There is no need for lab work, and multiple appointments such as impressions for the Hyrax construction, cementing the Hyrax, activation, check up, securing the screw after activation.

But the main issue here is the fact that with this approach there is no problems what-so-ever like in the facemask protocol. The patients do not wear something visible, and as such the traction is 24h/day. Also during sleep there is no discomfort of wearing a huge and bulky appliance such as the facemask. Motivation of patients and compliance is most probably enhanced.

The obvious disadvantage is of course the need for the patients which are usually of very young age (8-9years even younger in some cases) to undergo two operations. One for the insertion and one for the removal of the mini-plates.

Lastly the use of full fixed appliances could be done in conjunction with this protocol. With older patients of 12-13 years  the traditional orthodontic treatment could be carried out, on top of having the mini-plates and the Class III elastics.

It seems we are moving towards an era where traditional facemask treatment for protraction of Class III patients with maxillary deficiency will be a thing of the past.

The stability of those treatments remains to be tested with time, along with the existence of any kind of side-effects to the temporo-mandibular joint from the "chin cup" effect of the Class III traction. Time will tell.


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