Posted by: @sinned

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6361671/

Are there any more studies like this? It doesn't seem like there's enough research on cyclical loading of the sutures/facial bones. I think it could potentially be more effective than constant, static forces. The issue it seems with getting maxillary changes is that it's hard to overcome the resistance of the zygomatic buttress, would it not make sense that the forces are simply too low? I'd liken it to trying to build muscle doing 100 reps vs just doing 10, 10 reps would obviously be more effective. Furthermore, bone might have a better chance at remodeling with intermittent force than constant, static force.

That's a great find!  The conclusion is very encouraging:

Daily spurts of cyclic load caused sutural strain throughout the skull. The regime likely enhances suture growth and may be therapeutically useful.

And I love the fact that this publication is an "official publication of the American Association of Orthodontists".  :)   Maybe in 5 or 10 more years they'll finally catch on?

The results noted in the study fits with theories that Dr. Belfor and Dr. Singh have believed for some time, and providers like Dr. Miraglia have been saying the same things recently - that it's the "intermittent" cyclical forces which are what creates bone, not a constant strain (like an AGGA I suppose, or whatever acrylic appliance that Ron Ead had which was 24x7 wear).  In fact, Dr. Miraglia goes so far as to say that he talks to actual orthopedists to get his education on bone growth (not orthodontists) and he claims they say the same things, that cyclical loads are what create growth and that that's a well-understood concept in some of their medical texts.

I know @greyham made a blog post about it over on his site, and is actually cycling his wear quite a bit throughout the day: https://cfs-survivors.org/blog/2020/10/15/the-optimal-daytime-usage-pattern-for-adult-oral-expansion-appliances/

I'd also be curious to know from @greyham his thought on the cycling pattern that they used here - 2.5Hz.  I've not quite understood that measurement model applied to the human body and a 24 hour day ... but I think he understands it reasonably well.

Here's another animal study - they put stretch forces over the premaxillary sutures in rats (which are believed to be biologically similar enough to humans) and sure enough under an electron microscope they can see the sutures getting wider: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5417680/

So we have all sorts of animal models showing that cyclical forces, and "stretch" forces are creating exactly what we would want - naturally, via remodeling (not mechanically by causing an actual break in the structure of the suture, and then staying a step a head of the body's inflammatory healing process until you can measure the additional width you want).

@toomer

https://asbmr.onlinelibrary.wiley.com/doi/10.1359/jbmr.2003.18.3.521

Here's a study that's cited in the one I linked, they use the same amount of force and time each day; "for 10 minutes/day over 12 days with two different waveforms: static forces with a frequency of 0 Hz and sine‐wave cyclic forces with a frequency 1 Hz, leading to 600 cycles per day". Unfortunately it's on rabbits, but further research should be done. There may be an "ideal" rate for humans that signals for growth.

I think there's probably an ideal rate for the maxilla, but I'm not sure if it's specific to the maxilla or if bones just in general respond better to intermittent forces for growth. I also think that the maxilla in children probably grows cyclically, growth spurts occur intermittently as well, there are long stretches where no bone growth occurs and short periods where there's a lot of bone growth. It seems like a common pattern that growth in the human body occurs intermittently, having constant growth is more commonly a dysfunction. It makes sense that this might extend to the craniofacial region as well, although it kind of sucks to see such a lack of studies in this area.

@sinned In the original report you posted, it looks like they were sedated and then had the load cycling going for 30 minutes a day, and at a frequency level that they felt somewhat matched the pigs normal mastication (chewing) rate.

As for the "600 cycles per day" in the experiment you just linked, it's interesting because one point of the theories of Drs. Belfor and Singh is that you swallow like 2,000 to 3,000 times a day - including a bunch of times while you're sleeping - so that's maybe 1,000 times a day of pressure forces on the inter maxillary suture caused by the pressure differential the swallow action creates in the space differential between the acrylic roof of the DNA appliance, and the actual palate (DNA appliances by design aren't supposed to be touching the palate surfaces).

Your muscles have a frequency as well, so don't worry, the loads will never be "static". It's between 15-30Hz I believe.

Posted by: @toomer

I'd also be curious to know from @greyham his thought on the cycling pattern that they used here - 2.5Hz.  I've not quite understood that measurement model applied to the human body and a 24 hour day ... but I think he understands it reasonably well.  

I haven't seen any research showing the effects of cycling at the extraordinarily low frequency that Dr. Miraglia recommends, which works out to be around 0.00014 Hz (1 cycle / 2 hours); and I vaguely recall that the animal study I looked at showed at reduction in growth rate as the frequency dropped below a couple of Hz or so unfortunately. I really can't extrapolate that down to what might happen 4 orders of magnitude slower though, other than that it's unlikely to be bad and if it works for Dr. Miraglia's patients, I'm willing to try it. I tried to get in touch with Dr. Adrian Lok whose 2019 doctoral dissertation Quantifying the effects of mechanical vibration on the volume of the midpalatal suture covers this to ask his opinion on it. Coincidentally he went to the same university as me, but I don't know his uni email address and I haven't heard anything back from his dental practice yet.