March 04, 2019

In Conclusion…A guest post by Lysle Johnston

This is a guest blog post by Lysle Johnston one of World’s most respected orthodontists.  He addresses some of the issues on Class II correction that have been raised in previous posts.

Apologia

At the outset, please note that this communication is, to a degree, an apologia for cephalometrics in the 21stCentury.  I am willing to acknowledge/admit that much of the past century’s cephalometric “research” has provided useless answers to unasked questions.  Perhaps, as a result, it is de rigueurto say that this sort of research is obsolete. Admittedly, cephalometrics can’t answer questions about “satisfaction”:  don’t you feel better coming to me knowing that we are going to “work with growth” by treating early and often?

Importantly, the fact that something is easy to do and even easier to sell doesn’t hide the fact that there often is no evidence to characterise what our contemporary “new age” treatments actually can do and how they do it.  More?  Better? Different?   Who cares?  As long as nobody dies from anchorage loss, data are beside the point; florid advertising is all that’s necessary.  To someone who, since a rural childhood, has taken clocks and cars and all things mechanical apart to understand the underlying mechanics, I would argue that skilled cephalometric analysis (2D or 3D) is at present perhaps the only way to characterize the actual morphological impact of the wares being sold in today’s orthodontic bazaar.  So be it.  Based on 60 years of cephalometric research, I have reached a number of conclusions about the inner workings of our various treatments.  More than a century of “bone growing” with old, new, and re-cycled treatments is a case in point.

How does Class II correction occur?

For both Class I and II malocclusions, it is known (from cephalometrics) that the usual pattern of growth features a mandibular excess.  Alas, we also know (again, from cephalometrics) that, in the absence of treatment, this favourable mandibular excess usually has no impact on the molar relationship:  maxillary dento-alveolar compensation neutralises the effect of any mandibular excess. Based on data (once more, from cephalometrics) obtained from an analysis of thousands of different Class II treatments, I would argue that all successful modalities (the reader can specify the criteria for “success”) do what they do by controlling the A-P position of the upper dentition.

As a result, “Carriere motion” devices, headgear, TADs, “distal jets,” Class II elastics, and the like all would serve, not only control the maxillary buccal segments as needed but also allow whatever mandibular excess happens to occur to contribute to a molar correction.  Appropriate to the present thread, the same argument can be made (based on my cephalometric data) for any treatment that features some sort of bite jumping in the hope of augmenting mandibular growth.

What “works”?

Firstly, it is clear that “functionals” work; however, the bulk of the pertinent evidence (derived from cephalometrics) argues that this outcome depends on the usual pattern of growth, rather than an assumed, but probably imaginary mandibular growth augmentation.  Actually, the “Sunday bite” produced by functional appliances serves to keep the mandible forward so that the normal (“usual”; “expected”; average; etc.) mandibular excess can occur without causing maxillary dento-alveolar compensations. Further, it would allow this excess to grow the condyles back into the fossae, thereby helping to hold the forward mandibular occlusal position.  Given this analysis, keying a mandibular aligner into a forward position might work; unfortunately, it is probably an unnecessary elaboration.

If the name of the game is to allow the normal mandibular excess to occur without pushing the uppers forward, all that would be needed is to “flat plane” the upper (or lower) aligner.  From my cephalometric data, I would argue that, In the absence of occlusal intercuspation, all or part of the Class II correction thus would be achieved “for free.”  I suggested this modification to Invisalign years ago, but there was little interest.  The future probably will be no kinder to the world of cephalometric inference and its atavistic practitioners.  If so, I think we are in danger of throwing out the baby with the bathwater under the assumption that cephalometrics has little place in the world of contemporary craniofacial biology.

If, as seems likely, cephalometric data are to be ignored (rationalised by a self-serving concern for “radiation hygiene”), salability and a practice’s “bottom line” will be the only criteria by which we can guess whether some new appliance actually does what is claimed.  That’s the way it is and the way it probably always will be, “World without end.”

I’m glad to be retired.

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Have your say!

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    Dr. Lysle Johnston hit the “nail on the head” when describing the correction of Class II malocclusions with different modalities. I would like to add one more thing to Dr. Johnston’s comments…”I’m glad to be retired” also.

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    This is why one of the most meaningful things an orthodontist can do is to superimpose tracings as in the ABO experience. At least one time in ones career you can critally view what is going on or what was done.

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      As in all these things, you need to be a little careful as all points move with growth. I’m not overly convinced that, in general, post op cephs are appropriate really as long as the clinical picture is acceptable.

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    Oh how we miss the incisive skewering of the pompous, deluded and self aggrandizing amongst us. Enjoy retirement but an occasional reminder that we are scientists at heart would be welcomed.

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    Well that was a depressing read.

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    Thanks Lysle, I’m glad you are in a less stressful place, even though I still value your wonderful contributions. As usual, your views co-incide fully with mine even though we arrived here from apparently different orthodontic planets. I trained at Eastman, London and practice in Melbourne AU. I was trained to trace before and after for all class ii correctors. I still always do it, 30 years later. It takes literally a minute, on the fly, in the clinic with mum & dad looking over my shoulder. And I superimpose the two. It’s one of the most interesting, educational and “salesful” “wow-moments” in my practice. And there is absolutely no doubt, in my mind, that your version of what is happening, is correct.

    To say, as some self-serving health economists conclude, that cephalometrics has no benefit to the individual patients, is untrue. Unless, of course, one can’t be bothered to do it properly. Such a situation would be understandable if all one could afford was coloured pencils and greasproof baking paper to use for cephalometrics. But if your fees afford a proper facilitiy to be used, like, let’s say a properly integrated patient image and retrieval database, then cephalometics will reward the user and patient. From Geoff Wexler.

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    As one of the lucky ones that studied under Dr. Johnston’s tutelage, I am very thankful that he has always fought the good fight on behalf of science and fact. I still laugh thinking about Dr. Johnston’s lectures/editorials titled, “Growing jaws for fun and profit”. Just the other day the Invisalign rep. stopped by and bragged loudly in front of my receptionist’s desk that he has 18,000 finished cases that show how Invisalign’s mandibular advancement (MA) enhancement works well in augmenting growth. I plan to send him the details from this well done post.

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    Any 2 dimensional analysis of a 3 dimensional object has obvious drawbacks. To assume that the hard and soft tissues of the head in a growing patient, if held in space for a time in a different orientation; will not respond and be altered ignores all basic rules of biology. It also ignores the obvious health benefit obtained in altering a long term mouth breathing and deviated swallowing pattern to a more normal pattern. To assume the benefit in normal respiration does not continued to positively influence growth is also not reasonable. One cannot use the “smoke and mirror” science of a so called “usual pattern of growth” to explain away all things. One needs the pressure of the lips on the outside, the tongue on the inside and the cusps in a normal orientation for both dental stability and continued normal function.

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      I think you missed the most Important point. At least he advocates reliable measurement. I grant you there may be discussion about validity if one extrapolates and attempts prediction.

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    It is interesting to see the plethora of inane postulates and incongruous aphorisms that seem to punctuate the perspectives of the factually-challenged.
    One can glean as much or as little from cephalometrics as his/her own cognitive dissonance will allow.

    The only “Smoke and Mirrors” seems to be the tenacious grip to tenuous fallacy, while indulging in all the expansive and diverse manifestations of denial.
    All these so-called “rules of biology” and ‘theories” are sorely in need of evincing. Color us skeptical, but Proof >>>>Platitude.

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    Dear Dr. Johnston

    Do you think maybe 21st-Century cephalometrics might be made somewhat more useful if it were informed by the crania and mandibles of sub-adults (fetuses, infants, children and teens) and adults (erupted third molars with retromolsr space) who’d died before cultural industrialization, rather than based upon a few Caucasian kids from mid 20th-Century America? You could have access to some of these specimens next time you are in Ann Arbor, or maybe come to U Penn or U Arkansas someday and we can look at some of them together sir.
    Fire Up Chips!
    Kev
    CMU-1977

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    Dear Dr. Johnston

    Do you think maybe that 21st-Century cephalometrics might be made somewhat more useful/made better, if became more informed by the crania and mandibles of sub-adults (fetuses, infants, children and teens) and adults (those specimens with erupted third molars and associated retromolar space) who’d died before their cultures had been exposed to industrialization (i.e., ‘Western-exposed), rather than based upon a few Caucasian kids from mid 20th-Century America, as was the basis for Steiner and Downs analyses(Casco)?

    Sam Bishara taught me this in the mid-1980’s

    You might gain access to some of these pre-industrialized specimens next time you are in Ann Arbor, or maybe please come to U Penn or U Arkansas someday and we can look at some of them together sir…..I’d be honored to introduce you to some of your pre-industrialized ancestors someday Prof. Johnston, most of whom seldom required the services of an orthodontist….or ENT surgeon for that matter.

    Fire Up Chips!
    Kev
    CMU-1977

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    I wait impatiently to see some ceph overlays using CBCT. Then we will be able to document “Sunday bite” correction of Cl II using functional appliances in 3-D.

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    I was missing Dr Johnston’s sharp and lucid view of our profession. Even if retired please keep on sharing your thoughts!

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    “If the name of the game is to allow the normal mandibular excess to occur without pushing the uppers forward, all that would be needed is to “flat plane” the upper (or lower) aligner. From my cephalometric data, I would argue that, In the absence of occlusal intercuspation, all or part of the Class II correction thus would be achieved “for free.” ”

    I actually tried this! In a few patients I bonded acrylic pads to the upper posterior teeth in an attempt to uncouple the occlusion and permit mandibular growth to correct Cl II (with and without TADS as indirect anchorage). There was some Cl II corrective effect but it takes too long, you need to hit the sweet spot of the growth curve (good luck with that), and there are hygiene concerns with said brilliant strategy. But unfortunately there were negative vertical consequences…oops! The upper posterior teeth intruded, the occlusal place tip upward in the back and an increase in gingival display resulted consistently. Turns out there is “no free lunch.”

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      You just (very concisely )explained why fee for service ortho.practice has to work to a different metric pattern than academia.
      Both have value but real life pts.only pay for real and efficient changes ,not theoretical ones !

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    I would refer readers, and Prof. Johnston, to Prof. Harvold’s work on relative eruption as a means of affecting A-P relationships without relative growth. These effects are present in all Class II correctors, whether the inventors realise it or not. Look at the vertical, not just the A-P.

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    I remember Dr Johnston saying the same thing many years ago and decided then to “allow normal growth to change the bite” by using an upper removable posterior bite plane together with a lower fixed to attach class 2 in the assumption that by keeping the teeth apart the bite would jump. I only tend to do this in full unit 2 molar cases again assuming that when the posterior occlusion is half 2 then there is no likely impediment to bite jumping and that growth will do the job. Seems to work, although a proper study would be needed naturally. Maybe we should change the name of functional appliances to Growth Utilisers or something, it would be a start.

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    Well you can’t patent a flat plane , so of course they weren’t interested! They also don’t utilise their attachments that are out of patent , you have to request them . The “magic” patented attachments are really all that separates them from all other aligner compsnies

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    I think 3D analysis will revolutionise our understanding of growth-effects in non-treated and treated cases, to a far more accurate extent than current 2D superimposed crude imagery.
    Of course the ethical issues and ‘benefit vs harm’ conundrum will need to be addressed and may be possible as both technology increases and overall doses decreases, to justify at least a research-based open sourced database to inform all………. however this is far in the future.

    That is without even considering the bigger questions, like is Class 2 a ‘disease’ to be treated and is most of Orthodontics in the population mainly a ‘cosmetic’ procedure anyway, determined by societal desires ???

    As thinking Dentists it is important that we keep questioning what we do and why and of course with the passage of time, one realises that we ‘know’ a lot LESS than we thought we knew previously !!

    Yours reflectively,

    Tony.

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    Isn’t that interesting? Was it Dr. Johnston who remarked, “There’s so much we know, that we pretend not to”?

    Who benefits from this “lack of knowledge” or “absence of certitude”? All this rhetorical drivel is geared towards a subliminal objective to further an agenda that is in contravention to the data.

    When we are fooled into thinking we “know” a lot less, folks assume that we become more susceptible to gibberish like Retractive Orthodontics, Airway-Friendly Orthodontics, Face-Focused Orthodontics…you get the picture.

    As for the harm, the only harm is done to the brain when trying to contort itself into conflating fantasy with reality.

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    The examples Dr. Johnston cites are what I referred to in my lectures as “faith based medicine”, as opposed to evidence based medicine. Lyle just re-enforces how fortunate I was to have Tony Gianelli as my mentor. And I too am glad to be retired.

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    Somehow and for a few reasons, I can imagine the ghost of Robert M. Ricketts smiling.

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