December 05, 2021

How much relapse occurs after 40 years?

We all know that orthodontic treatment relapses to a degree. This new study looked at orthodontic relapse over 40 years. I thought that the results were interesting and clinically relevant.

Most research suggests that orthodontic relapse is inevitable. However, longitudinal studies also show that arch dimensions in untreated people change over several years. Therefore, we could consider that relapse is part of the normal ageing process that we cannot stop!   In many ways, it is surprising that only a few researchers have looked at this critical area.  As a result, I thought that this new study was fascinating.

A team from Bauru, Brazil, did the study. The AJO-DDO published the paper.

Occlusal changes in orthodontically treated subjects 40 years after treatment and comparison with untreated control subjects.

Karina Maria Salvatore Freitas, et al. AJO on line.

What did they ask?

The aim of their study was

“To compare the ageing changes of the dental arches in orthodontically treated and untreated subjects after a four-decade follow up”.

What did they do?

They looked at the dental casts of orthodontic patients and an untreated group.

The orthodontic sample.

They collected the records for the 29 orthodontic patients from the files of the graduate clinic at Bauru Dental School.  The main inclusion criteria were:

  • Class I or Class II Division 1 malocclusion
  • Fixed appliance treatment with the extraction of four first premolars.

They took the records at the start and end of treatment and at least 25 years after the end of treatment. Notably, the patients had stopped retention at less than 3.3 years after treatment.

The untreated group

These were 22 people who had not received orthodontic treatment.  They collected the initial records from 1967 to 1974. They took final records from April 2015 to May 2016.  Unfortunately, the authors did not state where they obtained this sample of people.

In the treated group, the only teeth that were missing were the first premolars. However, in the untreated group, most subjects had some teeth missing.

The primary outcome was Little’s Index for incisal crowding. The study team also used the PAR index for treatment change and measured other dental dimensions. For example, arch width at the canines and molars, arch length, etc.

What did they find?

The paper contained a large amount of detailed data. Unfortunately, I do not have the space to go into this all here. So, I am going to concentrate on what I feel are the main findings.

At the start of the study, the groups were similar for their age and sex distribution. But, unfortunately, the groups were different in follow-up times. The authors addressed this problem by annualising the changes for the untreated group. I thought that this was reasonable.

The important findings were

  • The treated group was followed for 36.4 years after the end of retention. The follow-up for the untreated subjects was 43.12 years.
  • In the treated group, crowding was corrected with treatment. However, it then significantly relapsed in the long term.  For example, the mean Little’s Index change for mandibular crowding was 4.28 (SD=2.79) compared to 1.29 (1.05) in the untreated group.  When they looked at maxillary crowding, the difference for the treated group was 3.11(1.49) and 0.68 (0.9) for the untreated subjects.
  • At the final data collection, the treated group had Little’s Index scores of 4.0 in the maxilla and 5.3 in the mandible. At the start of the treatment, the LI score for the maxilla was 10.0 and 8.9 for the mandible.
  • In the treated group, intercanine width increased with treatment and decreased with time. This was not the case for the untreated sample.
  • Overjet and overbite were corrected with treatment and remained stable.

Their conclusions were:

“Treated patients showed a relapse of crowding and a decrease in arch form. However, the long-term changes in the untreated group were different from the treated group”.

What did I think?

I thought that this was an ambitious project that must have taken a great deal of effort. The authors wrote a very detailed paper, and I hope that I have extracted sufficient information from the large amount of data they produced.

As with all research work, there are some deficiencies that I feel I should mention.  Most importantly, I could not find any information on the source of the untreated subjects.  As a result, we need to be careful in assuming that the two groups came from similar sources. This problem means that there may be some bias. However, we do not know the direction of the bias.

We also need to consider the reasons for people taking part in studies of this nature. For example, was it possible to take the records because the participants were pleased with the results of their treatment, or were they disappointed? Again, this may introduce bias.

Nevertheless, I think that I am being very critical. It is an outstanding achievement to obtain information over such a long period.  I know that the expansionists, magic bracket users, mandible growers, breathing physicians, and myofunctional orthodontists will say that the investigators did this study wrong, and the findings do not apply to their patients.  I simply suggest that they research their treatment and not merely quote the “Pyramid of Denial”.

Final comments

This paper adds to our knowledge and reinforces that orthodontic treatment relapses to a clinically important degree. I cannot help feeling that orthodontic relapse is something that we should accept. Perhaps, we should explain that this is a feature of ageing and we cannot stop time?

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Have your say!

  1. “Perhaps, we should explain that this is a feature of ageing and we cannot stop time?”
    I always asked patients if they would expect their faces to remain the same over time.
    In the ’60s and ’70s weren’t we taught that intercanine width and lower incisor inclination was sacred (Mills)? So, maybe some of these patients were treated to that standard – could this affect the results?

  2. “…..expansionists, magic bracket users, mandible growers, breathing physicians, and myofunctional orthodontists will say that the investigators did this study wrong, and the findings do not apply to their patients. I simply suggest that they research their treatment and not merely quote the “Pyramid of Denial”…….”. Sidebar comment and quoting from Prof. Dan Gilbert’s outstanding book Stumbling on Happiness, 2006….”natural happiness is what we get when we get what we wanted, and synthetic happiness is what we ‘MAKE’ when we don’t get what we wanted.”

  3. Agree the bigger challenge is separating the inevitable physiologic change (nothing in the universe stands still; occlusion, even great ones are not the exception) over time from orthodontic relapse. Perhaps data showing the velocity of change over time once retention ceased may assist with that, if it is possible? Happy Holidays to all and thx Kevin for keeping us a little distracted in 2021 VVXX

  4. This study shows that NOT respecting the original arch form, lower intercanine width, and dumping or “advancing” lower incisors is doomed for relapse. Hays Nance was right, “Advancing lower incisors is suicide.” Lavern Merrifield in his description of “The Dimensions of the Denture” described a lateral limit, anterior limit, posterior limit and vertical limit of the arch. If these limits are respected long term stability is achievable. This has been shown by published studies from James Vaden, Jimmy Boley and others. But, extraction treatment does not sell as readily. No one dies from bad orthodontics–Lysle Johnston, Jr.

    • Pertaining to cuspid retraction, as I recall Bob Little’s substantial studies at U Washington, Seattle showed that with first bicuspid extractions the lower cuspids were regularly retracted into a wider arch position (into the first bicuspid sites) and, therefore, expanded.

  5. The workers’ conclusion that “Treated patients showed a relapse of crowding and a decrease in arch form. However, the long-term changes in the untreated group were different from the treated group” is spot on. The changes in the treated group over some 40 years are 230% worse than the untreated group! (LI: 4.28 cf LI: 1.29) Does that not beg the question about the validity of extraction orthodontics? It would have been interesting to include a second control of patients treated non-extraction for a more informative result.
    There is a whole lot more to relapse and instability than just the teeth, especially if one focusses on the 6 front teeth alone.

  6. Awareness of this tendency to relapse forever is why we recommend that retainers be worn every night for at least two years, or until age 18. Subsequent to that, we advise that they be tried in every night for the rest of your life if you want your teeth to stay put. When you try them in, the fit will tell you if you need to wear them that night or not.

  7. Interesting study but how many orthodontists routinely advocate the extraction of 4 FIRST premolars these days?? It was a good long term study..40 years, supporting Lysle Johnson’s findings. It confirms for me at least, is the only way to “guarantee” stability is lifelong retention. We should make sure our patients know this when they consent to treatment.

  8. yes – accept relapse occurs, don’t deny it, and advise retention is for life…My follow up question is based upon the evidence should we be advising those who want to keep their occlusion stable to wear retainers to prevent unwanted change?

  9. It is important to fully understand why the teeth move, obviously due to a force.
    But what is this force responsible? Is it the force of chewing, of clenching the teeth, of grinding? Is it because of a bad habit?
    The mouth has a biomechanical function and although many do not believe it, the mouth has a hinge component and under normal conditions it functions as a third type lever.
    But in a state of disease, this biological lever is transformed into a lever of the first type in which the point of support is in the last molar (interference in centric), the power is in the masseter girth and the resistance is located in the condyle.
    The lever of the first type is the most powerful and efficient, but it is the most pathological because it develops excessively harmful forces.
    In this scenario, the force in the masseter girth is closely related to the denture, so excessive forces develop in the arches that are not biological, these forces are manifested in the teeth as dental mobility, diatemas, crowding, wear , destruction, dental loss as well as many other alterations.
    So our role as a dental health professional is to keep forces at biological levels.

  10. The main conclusion of the study seems to be that treatment relapse and physiologic change seem to be inevitable. Perhaps, the ancient Greek philosopher Heraclitus of Ephesus (c. 535 – 475 BC) already recognized this phenomenon of constant change: panta rhei (“everything flows”).

  11. One of my instructors would tell patients that as we get older our hair turns gray, our skin gets wrinkly and our teeth get wrinkly. Also, last year, I saw three patients who had banded lower 3-3 retainers that had recently broken and had to be removed. The alignment of the incisors were perfect, after 30 years. Also, the zinc phosphate cement was intact, not washed out. I was amazed.

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