Expanding horizons? A historic paper from the UK that warned us on the fallacy of expansion decades ago.

Let me see what’s left, let me see what’s true

A few weeks ago, I had been reviewing some of my old cases together with a colleague of mine who would then briefly mention to me a historic paper by B.R. Towned with an astute title “The Comedy of Expansion and the Tragedy of Relapse”. The next day, I foraged the Internet and with the help of Dr Eliseo Plasencia found the original text.

The first paragraph was already music to my ears:

“A very considerable number of dental practitioners in this country are practising expansion as a panacea for many orthodontic ills.”

“Many unfortunate children are being saddled with uncomfortable appliances which, as we shall see, by the very nature of things can be doing no good and sometimes positive harm.”

These lines from 1950s written by a British orthodontist accurately resemble my own thoughts I have today. It was surprising how little has changed and how many commonalities orthodontists share even divided by generations, national borders, and the amount of scientific data available. 

What also seems to be invariable is a desire of some individuals to violate the common sense. Despite the fact that from 1940s “Thou should not expand” is considered to be the first orthodontic commandment, each and every generation of practitioners are coming up with new methods to challenge the status quo.

Over the past decade, we have seen an expansion pendulum swinging back stimulated by the development of new bone-borne expanders and enticing CBCT images such treatment modality is always accompanied by.

Will I be that fool who rushes on to where angels fear to tread?

Miniscrew-assisted rapid palatal expansion (MARPE) has been proposed as a method which could potentially overcome the disadvantages we have with the traditional tooth-borne expanders, namely – the age limit and the unwanted tipping of the buccal teeth.

However, our knowledge on the effects of MARPE to this day is frugal and limited mostly to case reports. We certainly know that the success rate of the midpalatal suture opening in adults with MARPE is far from 100% and many practitioners report complications as severe as vomer trauma.

I believe that the hype around MARPE has the same nature as the hype around the self-ligating brackets we had a while ago. We have a new appliance and it raises our hopes for the easier treatment and better results. Although the evidence suggests we should come back to our senses and be careful weighing up the pros and cons each time before drilling the patient’s palate.

I know that you know the ending numbers

The recent studies on MARPE tell us that the difference in the amount of the midpalatal suture opening between MARPE and the traditional expanders is about 2 mm. I think this number has a very little significance in most of the cases, moreover we also don’t know if any of this additional expansion will be preserved in 5-year period.

Personally, I feel quite comfortable treating transverse discrepancies in mixed and early permanent dentition cases with the conventional tooth-borne expanders. I also feel that MARPE could be a wonderful addition to SARPE (Surgically-assisted rapid palatal expansion) in adult cases. Such combination could facilitate more bodily distraction of the maxilla. Furthermore, we should not forget that extraction is also an essential method to solve many orthodontic issues and sometimes can be used together with MARPE or classic tooth-borne expansion.

Going back to the paper by Towned, I think its conceptual value lies in his suggestion to distinguish between dental and bony arches. He writes:

“As the basal bone has an independent genetic origin from the teeth, there is no guarantee that the size of the bony arches and the dental arches will correspond.”

I think this idea sounds clear and reasonable. He then continues: 

“We must extract certain units of the dental arch so that its size may be correlated to that of the bony arch.”

All in all, I think that sometimes it is good to look back at the pieces of knowledge from the past. This gives the equanimity required not to fall for the legerdemains of the present. There is still something to the words of George Santayana: “Those who don’t know history are destined to repeat it.”


  1. Thanks . I teach burden of treatment in grad Ortho and welcome sober thoughts as to what would be the best for each patient , some treatment plans become very burdensome for patients and families . Ron


    • Hi Ron! Thanks for stopping by. Unfortunately, not every orthodontist has a sobriety of William Proffit.


  2. There is another paper which deserves to be kept in mind:
    JRE Mills, The stability of the lower labial segment. A cephalometric story. Dental Practitioner 1968
    He demonstrated that if the lower incisors are proclined to relieve crowding or reduce an overjet, the incisors tended to rebound back to their pre-treatment position unless they are permanently retained.
    I think our patients should expect us too work for a result which is stable without the need for permanent retention. After all, orthodontic treatment should not be a ‘life sentence’.


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