John Mew’s Lectures 8 – The Stage 1

Featured Video Play Icon

My father taught me the advantages of maxillary expansion which in his day was routine for 5 year olds unless they could place a 2mm coin between each front tooth, but when I graduated 30 years later, I was taught not to expand as it always relapsed. However the research of Skieller in 1964, using metal implants told me that most of the widening of the suture remained stable; it was the teeth and alveolus that relapsed. I then did my own research and found that if the tongue was resting in the palate, then there was very little relapse.

Unfortunately the dental authorities did not agree and I was fined large sums for expanding patients. This created my first confrontation with the British authorities and I had to take the Minister of Health to the High Court to justify expansion. At the time this changed the whole pattern of UK orthodontic treatment but most of my colleagues were using fixed appliances which are not ideal for expansion and so they soon forgot.

I designed the Stage 1 (see illustration below) in 1974 to achieve a range of objectives. It was constructed in Acrylic resin a very safe material, with one tooth cribbed on each side, with rests on the teeth in front and behind. This created a very stable appliance and with the use of Crozat clasps a child under the age of eight was not strong enough to remove it. It was in effect a fixed removable appliance, with the result that every adjustment was effective.

Stage 1 Appliance

After a lot of experiment I decided the best rate of expansion was 1/16th of a millimetre each side per day. I based this rate largely on the work of Storey 1973, who suggested that this rate widens the suture at a natural rate preventing the formation of scar tissue that often makes Rapid Expansion so damaging and unstable. So I adopted the 1/8th of a 1mm turn of the screw each day so that there was always blood flow to the periodontium. Research shows that small intermittent movements are less damaging than a gentle continuous force.

I introduced a ‘shelf’ on each side of the appliance, so that the lower teeth, which I do not expand at this point, would still be supported after 10mm of expansion. This had several advantages; it was sloped towards the midline so it guided the mandible to the centre and widened it slightly. Also It was smooth so it allowed the mandible to slide forward. At the same time biting on the lower teeth ensured the appliance was well seated. Many clinicians and other appliances do not use the shelves and I think it lessens their success. I strongly disapprove of any acrylic covering the teeth as this opens the bite.

To make sure that the arch form is correct, the Catenary wires behind the incisors are re-contoured forward 1mm every two weeks, lengthening the arch as well as widening. This coupled with the contact of the appliance against the soft tissues of the vault ensures a near ideal maxillary form. Appliances which only expand create distorted arches which relapse later. The Indicator Line is adjusted at the same time, this process will be described later.

Catenary
Catenary

There is an ‘Approximating Wire’ on each lateral incisor to enable the clinician to bring the incisors together with all of them facing forward in the centre of the arch,. A rest on the distal tooth each side ensures that the appliance does not tilt forward or aft and there is a hook each side of the Canines for forward pull headgear which can also be used to align the incisors with elastics but this should only be done when the incisors are supported behind by the Catenary Wire. Almost routinely I expand patients under nine 8 millimetres and older that 10 millimetres. This will usually move the maxilla forward two or three millimetres.

 

Engage with Prof John Mew or Dr Mike Mew on this topic;

Professionals (of any medical/health discipline);

https://www.facebook.com/groups/Orthodont/ or https://www.facebook.com/groups/Orthodont/permalink/3490898524262386/

 

Non Professionals;

https://www.facebook.com/groups/craniofacialactiongroup or

https://www.facebook.com/groups/craniofacialactiongroup/permalink/3055335594542770/

Leave a Reply