October 16, 2025 • 19 mins
An extensive overview of orthodontic treatments for Class II malocclusion in patients who are often uncooperative, focusing on various fixed functional and intra-arch noncompliance appliances. The text examines the mechanical designs, modes of action, clinical efficacy, and side effects of numerous devices, including the Herbst appliance, Jasper Jumper, Mandibular Anterior Repositioning Appliance (MARA), and various molar distalizers like the Pendulum Appliance and Distal Jet. Furthermore, the document discusses the importance of patient compliance in treatment success, exploring psychological profiles and alternative terms like adherence and therapeutic alliance. The sources also offer detailed guidance on appliance construction, management, activation, and retention, often comparing different devices based on skeletal and dental changes observed in clinical studies.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
Welcome back to the deep Dive. Today, we're tackling a
really critical document, the foundational text on treating class to
non compliant patients. We're going to distill the science for
you exactly.
Speaker 2 (00:12):
Our mission today is well pretty straightforward. We want to
cut through all the dense literature and give you a
comprehensive look at the fixed appliance is used for class
two correction, specifically the ones designed to get around that
huge barrier patient cooperation.
Speaker 1 (00:27):
Or lack thereof.
Speaker 2 (00:28):
Often precisely, this is all about understanding the biomechanics that
really changed how we approach these cases.
Speaker 1 (00:35):
Yeah, let's start right there with compliance or you know
the term. The literature uses adherence, collaboration.
Speaker 3 (00:40):
Therapeutic alliance sometimes right, but.
Speaker 1 (00:43):
It all boils down to whether the patient actually does
what you need them to do.
Speaker 2 (00:47):
And the research is pretty clear on the profiles. You've
got your low compliance types maybe impulsive, impatient, sometimes just negligent,
and then the high compliance patients diligent, responsible, self controlled.
Speaker 3 (01:00):
It seems obvious, maybe.
Speaker 1 (01:02):
It does seem like common sense, but the key bit
for clinicians, the real takeaway is that cooperation isn't static.
It tends to drop off.
Speaker 2 (01:10):
Oh, absolutely predictably and significantly between say, ten and eighteen
months into treatment. That's a crucial window.
Speaker 1 (01:18):
So if your whole plan relies on them wearing elastics
perfectly in months sixteen, well good luck.
Speaker 3 (01:25):
If you're probably setting yourself up for frustration.
Speaker 2 (01:27):
Yeah, and that sort of clinical deadline, that reality is
exactly why the focus shifted so heavily towards fixed appliances,
things that don't depend so much on the patient.
Speaker 1 (01:36):
Which brings us neatly to our first big category, fixed
functional appliances, the ones designed from mandibular repositioning.
Speaker 2 (01:43):
That's right, and the core idea behind these the philosophy
is something the source calls energy management.
Speaker 1 (01:48):
Energy management that sounds eliminating. Why that term.
Speaker 2 (01:52):
Well sets up a really helpful contrast with the older
ways think about. The old approach is mostly polling mechanics,
you know, like a class too.
Speaker 3 (01:58):
Elastis right.
Speaker 2 (01:59):
The removable one ones, Yeah, they deliver high forces, but
intermittently only when worn, and they often have unwanted side
effects like extruding teeth, messing with the vertical dimension.
Speaker 1 (02:10):
Okay.
Speaker 2 (02:10):
Modern fixed functional appliances, on the other hand, use what
the text calls flexible pushing mechanics. They manage and crucially
capture continuous forces.
Speaker 1 (02:21):
How do they capture energy? What's actually powering the change?
Speaker 2 (02:24):
It's the patient's own body, their biology. You're chewing muscles.
The mastigatory muscles generate a surprising amount of force, like
ten pounds on average when you close.
Speaker 1 (02:33):
Wow.
Speaker 3 (02:33):
Okay, So if you have a fixed.
Speaker 2 (02:34):
Device in there that resists that closing just a little bit,
maybe it needs say four ounces of force per side
to engage, the patient has to constantly exert an extra
eight ounces of force just to bite, normally to chew.
Speaker 1 (02:47):
Ah. So it's a continuous, low level workout exactly, a
small mandated two hundred and four to seven workload, And
that's what drives the long term orthopedic change.
Speaker 3 (02:55):
It's harnessing the body's power.
Speaker 1 (02:57):
Okay, if that makes sense. So when we talk fixed
fiveunctional appliances, there's one that always comes up first, the benchmark,
the HERBS.
Speaker 2 (03:05):
Absolutely, the IRBs is without question the reference standard. It
works because it forces the mandible forward two hundred and
forty seven using this rigid fixed telescopic.
Speaker 1 (03:15):
Mechanism telescopic like tubes sliding within each.
Speaker 2 (03:18):
Other precisely and it applies force in two directions at once,
pushing back on the upper jaw the maxilla, and pushing
forward on.
Speaker 3 (03:25):
The lower jaw the mandible.
Speaker 2 (03:26):
And the results they're significant and really well documented. It's
shown to stimulate condolar gross the end of the jaw
bones sagitally up to three point eight millimeters during treatment.
Speaker 1 (03:35):
That's quite a bit it is, and the.
Speaker 2 (03:38):
Chin point, the pagonian moves forward anywhere from two point
six to seven point six millimeters long term. It's this
combined orthopedic bone level change and dental change that makes
it the standard everyone compares against.
Speaker 1 (03:50):
So herbs is the rigid standard bearer. Okay, let's just
slightly What about taking a removable concept like the twin
block and making it fixed. That's the MRA, right, the
Medibular Interior Repositioning Appliance exactly.
Speaker 2 (04:02):
Conceptually, the MRA is just like a fixed version of
a twin block. It uses these interlocking parts an upper
elbow and a lower arm to mechanically keep the lower
jaw forward.
Speaker 1 (04:12):
Seem straightforward.
Speaker 2 (04:13):
It does, But here's a really critical clinical pearl from
the sources. For the MRA to actually work effectively, you
absolutely must stabilize.
Speaker 1 (04:22):
The lower arch safly.
Speaker 2 (04:24):
How typically, with a lower lingual arch and LLA, it's
basically a wire connecting the lower molars behind the teeth.
Speaker 1 (04:30):
Okay, why is that so essential for the MRA.
Speaker 2 (04:33):
Because without that LA holding the lower molar steady, the
constant forward push from the MRA makes those molars want
to rotate inwards and forwards mesiolingually.
Speaker 1 (04:44):
Ah, and if they rotate, the lower.
Speaker 2 (04:46):
Arm just slips off the upper elbow. The mechanism disengages,
and your correction stops dead. The LA provides the necessary
anchorage to stop that rotation.
Speaker 1 (04:54):
That's a fantastic practical point. Got it. Now, what about
outcomes with MRA. The books seems to draw a line
between kids and adults.
Speaker 2 (05:02):
Yes, a very important distinction. In growing children, particularly boys
who are near their pubertal growth spurt, the correction includes
a significant amount of actual mandibular growth, real skeletal change.
But in adults who don't have that growth potential anymore,
the correction you get with MRA is almost entirely dental
veolar remodeling. The teeth shift within the bone, but the
(05:24):
underlying jaw relationship doesn't change much.
Speaker 1 (05:27):
Skeletally good to know. Okay, moving on. Maybe the most
visually obvious example of that flexible pushing idea the Jesser jumper.
Speaker 2 (05:36):
Ah, the jumper, Yes, it's quite a unique design. It's
basically a compressed coil spring inside a plastic sheath. It
delivers a light, continuous pushing force, usually around two hundred
and ten to three hundred and thirty grams if you
activated about four milimeters.
Speaker 1 (05:49):
Flexible continuous push sounds good. How effective is it?
Speaker 2 (05:52):
It is effective, but the type of correction is key here.
The breakdown is roughly sixty percent dental veolar changes tooth
movement and only about forty percent skeletal effects.
Speaker 1 (06:01):
So sixty forty dental violar versus skeletal. Why does that
split matter so much clinically?
Speaker 2 (06:06):
Well, imagine you have a patient with a really significant
skeletal issue, a truly small lower jaw. The jumper being
mostly tooth moving might not be your best choice compared
to something like the herbs, which gives you more of
that orthopedic skeletal push.
Speaker 1 (06:20):
So you trade some skeletal effects for maybe ease of use.
Speaker 2 (06:23):
Potentially, Yes, jumpers can be easier to install sometimes, but
you sacrifice some of that skeletal horsepower. And another point
the sources mentioned frequently is the jumper's main clinical drawback.
Speaker 1 (06:35):
They tend to break ah breakage. That's a practical headache,
it really is.
Speaker 2 (06:39):
It means more chare time, more repairs, which can be
frustrating for everyone.
Speaker 1 (06:43):
Okay, So to maybe tackle that breakage issue and combine
some good ideas, we then see things like the twin
Forest Bike corrector the TFBC.
Speaker 2 (06:51):
Right, the TFPC is a clever hybrid design. It kind
of borrows the fixed forward positioning idea from the HERBS,
but it uses an active nickel titanium push for the
force continuous force around one hundred to two hundred.
Speaker 1 (07:03):
Grams, so combining rigidity with an active spring sort of. Yeah.
Speaker 2 (07:08):
And the research on the TFBC highlighted something important about timing.
It showed a significant increase in mandibular length two point
one millimeters compared to just zero point seven millimeters in
control groups without the appliance.
Speaker 1 (07:20):
Okay, a measurable difference.
Speaker 2 (07:22):
Yes, But the key finding was when this effect was
most pronounced during cervical vertebral maturation stage two or CBMs two,
that specific stage of skeletal development.
Speaker 1 (07:33):
So knowing where your patient is in their growth cycle
is absolutely crucial for getting the most out of the TFBC.
Speaker 2 (07:39):
Absolutely critical timing is vital if you're aiming for that
orthopedic response makes sense.
Speaker 1 (07:44):
And finally, in this fixed functional group, there's the SABA
Universal Spring, the SUS SUS.
Speaker 2 (07:51):
Its big selling point is versatility. First, the design is universal,
meaning one size fits about eighty percent of patients, which
cuts down on lab work and customization sufficient very But
the really clever part is the biomechanics. It has an
internal spring, but you can choose to activate it.
Speaker 1 (08:06):
Or not, so you can change how it works exactly.
Speaker 2 (08:08):
If you deactivate the spring, it basically functions like a
rigid RB's telescope, good for maximizing that orthopedic hold, keeping
the jaw forward rigidly. But if you activate the spring,
you get that flexible push mechanism, which might be better
for encouraging more tooth movement, more dental violar change.
Speaker 1 (08:25):
So the clinician can actually adapt the force system mid
treatment without swapping out the whole appliance.
Speaker 2 (08:32):
That's the idea adaptability built right in.
Speaker 1 (08:34):
Wow. Okay, that gives us a really solid overview of
that first major strategy, the fixed functional appliances, using the
patient's own muscles to push the mandible forward. Now let's
switch gears conceptually, let's talk about the second main non
compliance strategy, intramaxillary appliances.
Speaker 2 (08:52):
Right, So, if the first group was mostly about moving
the lower jaw forward, this second group is primarily focused
on moving the upper molars backward or dist within the
upper arch the maxilla.
Speaker 1 (09:01):
So working within one jaw, not between two.
Speaker 2 (09:03):
Precisely, this approach is overwhelmingly focused on dental alveolar correction,
moving teeth to gain space or correct the byte relationship,
rather than changing the jaw position itself skeletally.
Speaker 1 (09:14):
And the classic example here, the one everyone learns about,
is the pendulum appliance.
Speaker 3 (09:18):
The pendulum.
Speaker 2 (09:19):
Yes, it uses these quite heavy point zero three two
inch TMA wire springs. They originate from a big crylic
button on the pallette, a nance button which acts as.
Speaker 1 (09:31):
The anchor, and it's known for being.
Speaker 2 (09:32):
Fast, undeniably fast. You can get significant molar distallization pushing
those upper molars back up to five point seven millimeters
quite rapidly.
Speaker 1 (09:41):
But you know, rapid force often comes with consequences. Biomechanically speaking,
is that true.
Speaker 3 (09:46):
Here, It absolutely is.
Speaker 2 (09:47):
The pendulum's main trade off is control, specifically control over
how the tooth moves. Because of where the force is applied,
you get a lot of distal.
Speaker 1 (09:55):
Tipping tipping, meaning the crown moves back way more than
the route exactly.
Speaker 2 (09:59):
The crown back significantly, sometimes measured between eight point four
degrees and really a shocking fifteen point seven degrees in
some studies, and that's not usually ideal. Plus you get
anchorage loss.
Speaker 1 (10:10):
Ah, the anchor teeth move too.
Speaker 2 (10:12):
Yes, the nance button rests against the pre molars usually
and they tend to move forward measually maybe one point
three to two point six millimeters. So you push the
molars back to gain space, but you lose some of
that space again as the front teeth drift forward.
Speaker 1 (10:27):
Okay, so speed, but with tipping and anchorage loss. If
the pendulum causes tipping, how did designers try to fix
that with the next iteration the distal jet.
Speaker 2 (10:36):
Well, the goal with the distal jet was specifically to
reduce that tipping moment. It's also a fixed palatal device,
uses a nickel titanium coil spring for the force like
some others.
Speaker 1 (10:48):
But the key difference is The key is.
Speaker 2 (10:49):
Where the force is applied. The discal jet is designed
so the push happens more parallel to the tooth center
of resistance, usually about four to five millimeters higher up,
closer to the roots, than with the pendulum.
Speaker 1 (11:01):
Pushing closer to the center of the tooth mass right.
Speaker 2 (11:04):
And by applying the force near that center of resistance,
you significantly reduce the tendency for the crown to tip back.
You get more bodily movement, although maybe not perfect translation.
Speaker 1 (11:13):
Does it get rid of the anchorage loss problem entirely?
Speaker 3 (11:16):
No, unfortunately not.
Speaker 2 (11:17):
You still get anchorage loss with the distal jet. Maybe
up to thirty percent of the space you create by
pushing the molars back can be liced by the premolars
drifting forward.
Speaker 1 (11:26):
Still a significant chunk it can be.
Speaker 2 (11:29):
But this is where newer technology really helps. You can
now place mini screw implants tads in the palette just
in front of the activation lock of the distal jet
for extra anchorage, for absolute anchorage. Essentially, those implants completely
brace the anterior segment, stopping the pre molars from moving forward.
It neutralizes that anchorage loss.
Speaker 1 (11:50):
Very clever integration. Okay, so we get tipping control improved.
What if the absolute priority is pure bodily movement, moving
the crown and root together there perfectly. That's where the
kingel slider.
Speaker 2 (12:02):
Comes in precisely. The keel slider's design goal is translation,
true bodily movement. It usually has a wide nance button
for stability, often with an anterior byte plane built in,
which is handy for deep bite cases. Okay, and it
uses heavy knitty coil springs maybe two hundred grams, but
they're mounted on these rigid sliding rods. These rods pass
through tubes attached to the molarbans.
Speaker 1 (12:22):
Through the molar tubes. Why is that important.
Speaker 2 (12:25):
Because it guarantees that the pushing force is delivered directly
at or very close to the tooth's center of resistance.
An applying force right at the center of resistance is
the fundamental mechanical requirement for achieving bodily movement instead of tipping.
Speaker 1 (12:39):
Got it pure translation by design. And finally, in this
intermaxillary group we have the first class appliance. The FCA
sounds like it's aiming for speed and efficiency.
Speaker 3 (12:50):
It is.
Speaker 2 (12:50):
It's known for being remarkably fast. The studies show at
correcting class two relationships in an average of just two
point four months.
Speaker 1 (12:57):
Wow, that's quick.
Speaker 2 (12:58):
It's very quick, and it's high highly regarded for its
anchorage control as well. It typically achieves about four point
zero millimeters of molar distallization, but with only about one
point seven millimeters of anchorage loss in the premolars.
Speaker 1 (13:11):
So doing the math, that's less than half anchorage loss
compared to the movement gained.
Speaker 2 (13:16):
Right, it works out to about a point four to
one ratio of anchorage loss to distallization, or roughly thirty
percent loss, which compared to some older methods, is very
efficient mechanically, one of the best options if you want
speed with reasonable control.
Speaker 1 (13:29):
Okay, you've mentioned mini screws or tads a few times
now as a way to combat anchorage loss. Let's just
touch on that ultimate solution using implants for absolute anchorage.
Speaker 2 (13:40):
Yeah, absolute anchorage is kind of the holy grail if
you want to completely eliminate unwanted tooth movement. Using palatle
mini implants like Strawman orthosystem or the on plant system
gives you rigid, immovable stability.
Speaker 1 (13:54):
No reciprocal force, no anchorage laws.
Speaker 3 (13:56):
At all exactly.
Speaker 2 (13:58):
The implant just doesn't move. All the force goes exactly
where you want it. For instance, purely into distallizing the
molars without the premolars creeping.
Speaker 1 (14:06):
Forward sounds perfect. So if it solves the anchorage problem completely,
what's the catch? Is there a new clinical hurdle?
Speaker 2 (14:12):
There is, and it's time. Even this ultimate non compliant
solution introduces a different kind of compliance issue, a temporal one.
Meaning these implants, especially the larger surface area ones like
the on plant, need time to fuse with the bone
ossio integration. The on plant, for example, requires about sixteen
weeks of healing before you can safely start applying orthodontic
(14:32):
forces to it.
Speaker 1 (14:34):
Sixteen weeks, that's nearly four months of waiting before you
can even start the actual correction exactly.
Speaker 2 (14:40):
You need that waiting period for the implant to become
rigidly stable. So you solve the anchorage problem, but you
introduce a significant delay which might not sit well with
an impatient patient.
Speaker 3 (14:50):
Ironically, that really.
Speaker 1 (14:51):
Put an interesting spin on the whole non compliance idea.
You eliminate the need for patient action during treatment, but
you add this upfront waiting period.
Speaker 2 (15:00):
Every solution seems to have its trade off, doesn't it.
Speaker 1 (15:02):
It certainly seems that way. Okay, So let's recap. We've
explored these two fundamental non compliance strategies. First the fixed
functional appliances ERPST, MARI jumper, TFBC, SUS, which are mainly
about repositioning the mandible, often stimulating growth.
Speaker 2 (15:20):
Right harnessing muscle energy to push the lower jaw forward.
Speaker 1 (15:24):
And second the intermaxillary distallizer's pendulum distal jet geel slider FCA,
which focus on moving upper molars backward within the maxilla,
mostly dental veolar correction.
Speaker 2 (15:34):
Exactly gaining space or correcting the bite by moving teeth
within the arch.
Speaker 1 (15:38):
So the big synthesis here, the takeaway for you listening
is really about diagnosis.
Speaker 2 (15:42):
Absolutely the choice between these strategies, and even within the
strategies rigid versus flexible, for example, it all hinges on
accurately figuring out the root cause of the class two.
Is it mainly a skeletal problem like a small lower jaw,
Is it mostly the upper teeth being too are forward
or some combination, And you also need.
Speaker 1 (16:02):
To factor in the patient's growth.
Speaker 2 (16:04):
Status critically important, are they still growing how much? That
dictates whether you can realistically aim for skeletal change or
if you're limited to tooth movement. Once you've answered those
diagnostic questions, the path towards the optimal appliance becomes much clearer.
Speaker 1 (16:21):
Okay, that makes perfect sense. Diagnosis drives the treatment choice.
Now that brings us towards the end and our final
provocative thought. We spend all this time talking about how
to correct the class to non compliantly, but what about
making sure it lasts?
Speaker 3 (16:34):
Yeah?
Speaker 2 (16:34):
Stability, ah, stability the long game. And this is where
soft tissue adaptation comes in, something that's maybe overlooked sometimes
in the rush to get the correction done. Soft tissues
like muscles and daga muscles, the purious deal attachments, all
the connective tissues around the jaws and teeth. The sources
issue a pretty strong warning here. The rate of class
to relapse things shifting back is often directly proportional to
(16:58):
how fast and how much correct you achieved initially.
Speaker 1 (17:01):
So faster isn't always better for long term success.
Speaker 2 (17:04):
Not necessarily because bone changes tooth movements can happen relatively
quickly with these fixed appliances, but the soft tissues adapt
much much slower if you take the appliance off before
those muscles and tissues have fully remodeled and accepted the
new jaw or tooth position.
Speaker 1 (17:20):
They can just pull things back to where they started.
Speaker 2 (17:22):
They can actively contribute to relapse. Yes, it's why concepts
like overcorrection, pushing slightly beyond the ideal endpoint initially and
then allowing adequate retention time for those soft tissues to
fully adapt are so critical for making the correction stick
long term.
Speaker 1 (17:37):
Fascinating, So the biology needs time to catch up with
the mechanics. That is a phenomenal point to end on. Okay,
to help cement to all this, let's do a quick
clinical synthesis challenge thinking about the specific device features we discussed.
Speaker 3 (17:49):
All right, let's test it.
Speaker 1 (17:50):
Imagine you have an eleven year old patient. Diagnosis confirms
a true retrognatic mandible SEW a significant skeletal component, and
this patient has a history of poor compliance with earlier,
simpler treatments. You decide mandated mandibular repositioning is needed now,
based purely on the documented effects and force characteristics we
(18:11):
talked about, Which appliance would you theoretically choose to best
address that skeletal issue. The rigid IRBs or the flexible Jasper.
Speaker 2 (18:20):
Jumper and why okay, good scenario. Given the true skeletal
retrognathism and the need for orthopedic change in a growing patient,
you would theoretically select.
Speaker 1 (18:29):
The herbs appliance and the reasoning.
Speaker 2 (18:31):
The crucial factor is the Earth's higher documented skeletal contribution.
Its rigid twenty four hour forced protrusion is specifically shown
to stimulate more significant condular growth and mandibular advancement compared
to the jumper. Remember, the Jasper jumper gets about sixty
percent of its effect for moving teeth, only forty.
Speaker 3 (18:48):
Percent skeletal right.
Speaker 1 (18:49):
This sixty to forty split.
Speaker 2 (18:50):
Exactly so when the primary goal is to address a
major underlying skeletal deficiency, the herbs, with its greater orthopedic
horse power, is the more direct and theoreally efficient choice.
Despite any potential downsides like bulkiness, the skeletal need points
strongly towards the herbs in this case
Welcome back to the deep Dive. Today, we're tackling a
really critical document, the foundational text on treating class to
non compliant patients. We're going to distill the science for
you exactly.
Speaker 2 (00:12):
Our mission today is well pretty straightforward. We want to
cut through all the dense literature and give you a
comprehensive look at the fixed appliance is used for class
two correction, specifically the ones designed to get around that
huge barrier patient cooperation.
Speaker 1 (00:27):
Or lack thereof.
Speaker 2 (00:28):
Often precisely, this is all about understanding the biomechanics that
really changed how we approach these cases.
Speaker 1 (00:35):
Yeah, let's start right there with compliance or you know
the term. The literature uses adherence, collaboration.
Speaker 3 (00:40):
Therapeutic alliance sometimes right, but.
Speaker 1 (00:43):
It all boils down to whether the patient actually does
what you need them to do.
Speaker 2 (00:47):
And the research is pretty clear on the profiles. You've
got your low compliance types maybe impulsive, impatient, sometimes just negligent,
and then the high compliance patients diligent, responsible, self controlled.
Speaker 3 (01:00):
It seems obvious, maybe.
Speaker 1 (01:02):
It does seem like common sense, but the key bit
for clinicians, the real takeaway is that cooperation isn't static.
It tends to drop off.
Speaker 2 (01:10):
Oh, absolutely predictably and significantly between say, ten and eighteen
months into treatment. That's a crucial window.
Speaker 1 (01:18):
So if your whole plan relies on them wearing elastics
perfectly in months sixteen, well good luck.
Speaker 3 (01:25):
If you're probably setting yourself up for frustration.
Speaker 2 (01:27):
Yeah, and that sort of clinical deadline, that reality is
exactly why the focus shifted so heavily towards fixed appliances,
things that don't depend so much on the patient.
Speaker 1 (01:36):
Which brings us neatly to our first big category, fixed
functional appliances, the ones designed from mandibular repositioning.
Speaker 2 (01:43):
That's right, and the core idea behind these the philosophy
is something the source calls energy management.
Speaker 1 (01:48):
Energy management that sounds eliminating. Why that term.
Speaker 2 (01:52):
Well sets up a really helpful contrast with the older
ways think about. The old approach is mostly polling mechanics,
you know, like a class too.
Speaker 3 (01:58):
Elastis right.
Speaker 2 (01:59):
The removable one ones, Yeah, they deliver high forces, but
intermittently only when worn, and they often have unwanted side
effects like extruding teeth, messing with the vertical dimension.
Speaker 1 (02:10):
Okay.
Speaker 2 (02:10):
Modern fixed functional appliances, on the other hand, use what
the text calls flexible pushing mechanics. They manage and crucially
capture continuous forces.
Speaker 1 (02:21):
How do they capture energy? What's actually powering the change?
Speaker 2 (02:24):
It's the patient's own body, their biology. You're chewing muscles.
The mastigatory muscles generate a surprising amount of force, like
ten pounds on average when you close.
Speaker 1 (02:33):
Wow.
Speaker 3 (02:33):
Okay, So if you have a fixed.
Speaker 2 (02:34):
Device in there that resists that closing just a little bit,
maybe it needs say four ounces of force per side
to engage, the patient has to constantly exert an extra
eight ounces of force just to bite, normally to chew.
Speaker 1 (02:47):
Ah. So it's a continuous, low level workout exactly, a
small mandated two hundred and four to seven workload, And
that's what drives the long term orthopedic change.
Speaker 3 (02:55):
It's harnessing the body's power.
Speaker 1 (02:57):
Okay, if that makes sense. So when we talk fixed
fiveunctional appliances, there's one that always comes up first, the benchmark,
the HERBS.
Speaker 2 (03:05):
Absolutely, the IRBs is without question the reference standard. It
works because it forces the mandible forward two hundred and
forty seven using this rigid fixed telescopic.
Speaker 1 (03:15):
Mechanism telescopic like tubes sliding within each.
Speaker 2 (03:18):
Other precisely and it applies force in two directions at once,
pushing back on the upper jaw the maxilla, and pushing
forward on.
Speaker 3 (03:25):
The lower jaw the mandible.
Speaker 2 (03:26):
And the results they're significant and really well documented. It's
shown to stimulate condolar gross the end of the jaw
bones sagitally up to three point eight millimeters during treatment.
Speaker 1 (03:35):
That's quite a bit it is, and the.
Speaker 2 (03:38):
Chin point, the pagonian moves forward anywhere from two point
six to seven point six millimeters long term. It's this
combined orthopedic bone level change and dental change that makes
it the standard everyone compares against.
Speaker 1 (03:50):
So herbs is the rigid standard bearer. Okay, let's just
slightly What about taking a removable concept like the twin
block and making it fixed. That's the MRA, right, the
Medibular Interior Repositioning Appliance exactly.
Speaker 2 (04:02):
Conceptually, the MRA is just like a fixed version of
a twin block. It uses these interlocking parts an upper
elbow and a lower arm to mechanically keep the lower
jaw forward.
Speaker 1 (04:12):
Seem straightforward.
Speaker 2 (04:13):
It does, But here's a really critical clinical pearl from
the sources. For the MRA to actually work effectively, you
absolutely must stabilize.
Speaker 1 (04:22):
The lower arch safly.
Speaker 2 (04:24):
How typically, with a lower lingual arch and LLA, it's
basically a wire connecting the lower molars behind the teeth.
Speaker 1 (04:30):
Okay, why is that so essential for the MRA.
Speaker 2 (04:33):
Because without that LA holding the lower molar steady, the
constant forward push from the MRA makes those molars want
to rotate inwards and forwards mesiolingually.
Speaker 1 (04:44):
Ah, and if they rotate, the lower.
Speaker 2 (04:46):
Arm just slips off the upper elbow. The mechanism disengages,
and your correction stops dead. The LA provides the necessary
anchorage to stop that rotation.
Speaker 1 (04:54):
That's a fantastic practical point. Got it. Now, what about
outcomes with MRA. The books seems to draw a line
between kids and adults.
Speaker 2 (05:02):
Yes, a very important distinction. In growing children, particularly boys
who are near their pubertal growth spurt, the correction includes
a significant amount of actual mandibular growth, real skeletal change.
But in adults who don't have that growth potential anymore,
the correction you get with MRA is almost entirely dental
veolar remodeling. The teeth shift within the bone, but the
(05:24):
underlying jaw relationship doesn't change much.
Speaker 1 (05:27):
Skeletally good to know. Okay, moving on. Maybe the most
visually obvious example of that flexible pushing idea the Jesser jumper.
Speaker 2 (05:36):
Ah, the jumper, Yes, it's quite a unique design. It's
basically a compressed coil spring inside a plastic sheath. It
delivers a light, continuous pushing force, usually around two hundred
and ten to three hundred and thirty grams if you
activated about four milimeters.
Speaker 1 (05:49):
Flexible continuous push sounds good. How effective is it?
Speaker 2 (05:52):
It is effective, but the type of correction is key here.
The breakdown is roughly sixty percent dental veolar changes tooth
movement and only about forty percent skeletal effects.
Speaker 1 (06:01):
So sixty forty dental violar versus skeletal. Why does that
split matter so much clinically?
Speaker 2 (06:06):
Well, imagine you have a patient with a really significant
skeletal issue, a truly small lower jaw. The jumper being
mostly tooth moving might not be your best choice compared
to something like the herbs, which gives you more of
that orthopedic skeletal push.
Speaker 1 (06:20):
So you trade some skeletal effects for maybe ease of use.
Speaker 2 (06:23):
Potentially, Yes, jumpers can be easier to install sometimes, but
you sacrifice some of that skeletal horsepower. And another point
the sources mentioned frequently is the jumper's main clinical drawback.
Speaker 1 (06:35):
They tend to break ah breakage. That's a practical headache,
it really is.
Speaker 2 (06:39):
It means more chare time, more repairs, which can be
frustrating for everyone.
Speaker 1 (06:43):
Okay, So to maybe tackle that breakage issue and combine
some good ideas, we then see things like the twin
Forest Bike corrector the TFBC.
Speaker 2 (06:51):
Right, the TFPC is a clever hybrid design. It kind
of borrows the fixed forward positioning idea from the HERBS,
but it uses an active nickel titanium push for the
force continuous force around one hundred to two hundred.
Speaker 1 (07:03):
Grams, so combining rigidity with an active spring sort of. Yeah.
Speaker 2 (07:08):
And the research on the TFBC highlighted something important about timing.
It showed a significant increase in mandibular length two point
one millimeters compared to just zero point seven millimeters in
control groups without the appliance.
Speaker 1 (07:20):
Okay, a measurable difference.
Speaker 2 (07:22):
Yes, But the key finding was when this effect was
most pronounced during cervical vertebral maturation stage two or CBMs two,
that specific stage of skeletal development.
Speaker 1 (07:33):
So knowing where your patient is in their growth cycle
is absolutely crucial for getting the most out of the TFBC.
Speaker 2 (07:39):
Absolutely critical timing is vital if you're aiming for that
orthopedic response makes sense.
Speaker 1 (07:44):
And finally, in this fixed functional group, there's the SABA
Universal Spring, the SUS SUS.
Speaker 2 (07:51):
Its big selling point is versatility. First, the design is universal,
meaning one size fits about eighty percent of patients, which
cuts down on lab work and customization sufficient very But
the really clever part is the biomechanics. It has an
internal spring, but you can choose to activate it.
Speaker 1 (08:06):
Or not, so you can change how it works exactly.
Speaker 2 (08:08):
If you deactivate the spring, it basically functions like a
rigid RB's telescope, good for maximizing that orthopedic hold, keeping
the jaw forward rigidly. But if you activate the spring,
you get that flexible push mechanism, which might be better
for encouraging more tooth movement, more dental violar change.
Speaker 1 (08:25):
So the clinician can actually adapt the force system mid
treatment without swapping out the whole appliance.
Speaker 2 (08:32):
That's the idea adaptability built right in.
Speaker 1 (08:34):
Wow. Okay, that gives us a really solid overview of
that first major strategy, the fixed functional appliances, using the
patient's own muscles to push the mandible forward. Now let's
switch gears conceptually, let's talk about the second main non
compliance strategy, intramaxillary appliances.
Speaker 2 (08:52):
Right, So, if the first group was mostly about moving
the lower jaw forward, this second group is primarily focused
on moving the upper molars backward or dist within the
upper arch the maxilla.
Speaker 1 (09:01):
So working within one jaw, not between two.
Speaker 2 (09:03):
Precisely, this approach is overwhelmingly focused on dental alveolar correction,
moving teeth to gain space or correct the byte relationship,
rather than changing the jaw position itself skeletally.
Speaker 1 (09:14):
And the classic example here, the one everyone learns about,
is the pendulum appliance.
Speaker 3 (09:18):
The pendulum.
Speaker 2 (09:19):
Yes, it uses these quite heavy point zero three two
inch TMA wire springs. They originate from a big crylic
button on the pallette, a nance button which acts as.
Speaker 1 (09:31):
The anchor, and it's known for being.
Speaker 2 (09:32):
Fast, undeniably fast. You can get significant molar distallization pushing
those upper molars back up to five point seven millimeters
quite rapidly.
Speaker 1 (09:41):
But you know, rapid force often comes with consequences. Biomechanically speaking,
is that true.
Speaker 3 (09:46):
Here, It absolutely is.
Speaker 2 (09:47):
The pendulum's main trade off is control, specifically control over
how the tooth moves. Because of where the force is applied,
you get a lot of distal.
Speaker 1 (09:55):
Tipping tipping, meaning the crown moves back way more than
the route exactly.
Speaker 2 (09:59):
The crown back significantly, sometimes measured between eight point four
degrees and really a shocking fifteen point seven degrees in
some studies, and that's not usually ideal. Plus you get
anchorage loss.
Speaker 1 (10:10):
Ah, the anchor teeth move too.
Speaker 2 (10:12):
Yes, the nance button rests against the pre molars usually
and they tend to move forward measually maybe one point
three to two point six millimeters. So you push the
molars back to gain space, but you lose some of
that space again as the front teeth drift forward.
Speaker 1 (10:27):
Okay, so speed, but with tipping and anchorage loss. If
the pendulum causes tipping, how did designers try to fix
that with the next iteration the distal jet.
Speaker 2 (10:36):
Well, the goal with the distal jet was specifically to
reduce that tipping moment. It's also a fixed palatal device,
uses a nickel titanium coil spring for the force like
some others.
Speaker 1 (10:48):
But the key difference is The key is.
Speaker 2 (10:49):
Where the force is applied. The discal jet is designed
so the push happens more parallel to the tooth center
of resistance, usually about four to five millimeters higher up,
closer to the roots, than with the pendulum.
Speaker 1 (11:01):
Pushing closer to the center of the tooth mass right.
Speaker 2 (11:04):
And by applying the force near that center of resistance,
you significantly reduce the tendency for the crown to tip back.
You get more bodily movement, although maybe not perfect translation.
Speaker 1 (11:13):
Does it get rid of the anchorage loss problem entirely?
Speaker 3 (11:16):
No, unfortunately not.
Speaker 2 (11:17):
You still get anchorage loss with the distal jet. Maybe
up to thirty percent of the space you create by
pushing the molars back can be liced by the premolars
drifting forward.
Speaker 1 (11:26):
Still a significant chunk it can be.
Speaker 2 (11:29):
But this is where newer technology really helps. You can
now place mini screw implants tads in the palette just
in front of the activation lock of the distal jet
for extra anchorage, for absolute anchorage. Essentially, those implants completely
brace the anterior segment, stopping the pre molars from moving forward.
It neutralizes that anchorage loss.
Speaker 1 (11:50):
Very clever integration. Okay, so we get tipping control improved.
What if the absolute priority is pure bodily movement, moving
the crown and root together there perfectly. That's where the
kingel slider.
Speaker 2 (12:02):
Comes in precisely. The keel slider's design goal is translation,
true bodily movement. It usually has a wide nance button
for stability, often with an anterior byte plane built in,
which is handy for deep bite cases. Okay, and it
uses heavy knitty coil springs maybe two hundred grams, but
they're mounted on these rigid sliding rods. These rods pass
through tubes attached to the molarbans.
Speaker 1 (12:22):
Through the molar tubes. Why is that important.
Speaker 2 (12:25):
Because it guarantees that the pushing force is delivered directly
at or very close to the tooth's center of resistance.
An applying force right at the center of resistance is
the fundamental mechanical requirement for achieving bodily movement instead of tipping.
Speaker 1 (12:39):
Got it pure translation by design. And finally, in this
intermaxillary group we have the first class appliance. The FCA
sounds like it's aiming for speed and efficiency.
Speaker 3 (12:50):
It is.
Speaker 2 (12:50):
It's known for being remarkably fast. The studies show at
correcting class two relationships in an average of just two
point four months.
Speaker 1 (12:57):
Wow, that's quick.
Speaker 2 (12:58):
It's very quick, and it's high highly regarded for its
anchorage control as well. It typically achieves about four point
zero millimeters of molar distallization, but with only about one
point seven millimeters of anchorage loss in the premolars.
Speaker 1 (13:11):
So doing the math, that's less than half anchorage loss
compared to the movement gained.
Speaker 2 (13:16):
Right, it works out to about a point four to
one ratio of anchorage loss to distallization, or roughly thirty
percent loss, which compared to some older methods, is very
efficient mechanically, one of the best options if you want
speed with reasonable control.
Speaker 1 (13:29):
Okay, you've mentioned mini screws or tads a few times
now as a way to combat anchorage loss. Let's just
touch on that ultimate solution using implants for absolute anchorage.
Speaker 2 (13:40):
Yeah, absolute anchorage is kind of the holy grail if
you want to completely eliminate unwanted tooth movement. Using palatle
mini implants like Strawman orthosystem or the on plant system
gives you rigid, immovable stability.
Speaker 1 (13:54):
No reciprocal force, no anchorage laws.
Speaker 3 (13:56):
At all exactly.
Speaker 2 (13:58):
The implant just doesn't move. All the force goes exactly
where you want it. For instance, purely into distallizing the
molars without the premolars creeping.
Speaker 1 (14:06):
Forward sounds perfect. So if it solves the anchorage problem completely,
what's the catch? Is there a new clinical hurdle?
Speaker 2 (14:12):
There is, and it's time. Even this ultimate non compliant
solution introduces a different kind of compliance issue, a temporal one.
Meaning these implants, especially the larger surface area ones like
the on plant, need time to fuse with the bone
ossio integration. The on plant, for example, requires about sixteen
weeks of healing before you can safely start applying orthodontic
(14:32):
forces to it.
Speaker 1 (14:34):
Sixteen weeks, that's nearly four months of waiting before you
can even start the actual correction exactly.
Speaker 2 (14:40):
You need that waiting period for the implant to become
rigidly stable. So you solve the anchorage problem, but you
introduce a significant delay which might not sit well with
an impatient patient.
Speaker 3 (14:50):
Ironically, that really.
Speaker 1 (14:51):
Put an interesting spin on the whole non compliance idea.
You eliminate the need for patient action during treatment, but
you add this upfront waiting period.
Speaker 2 (15:00):
Every solution seems to have its trade off, doesn't it.
Speaker 1 (15:02):
It certainly seems that way. Okay, So let's recap. We've
explored these two fundamental non compliance strategies. First the fixed
functional appliances ERPST, MARI jumper, TFBC, SUS, which are mainly
about repositioning the mandible, often stimulating growth.
Speaker 2 (15:20):
Right harnessing muscle energy to push the lower jaw forward.
Speaker 1 (15:24):
And second the intermaxillary distallizer's pendulum distal jet geel slider FCA,
which focus on moving upper molars backward within the maxilla,
mostly dental veolar correction.
Speaker 2 (15:34):
Exactly gaining space or correcting the bite by moving teeth
within the arch.
Speaker 1 (15:38):
So the big synthesis here, the takeaway for you listening
is really about diagnosis.
Speaker 2 (15:42):
Absolutely the choice between these strategies, and even within the
strategies rigid versus flexible, for example, it all hinges on
accurately figuring out the root cause of the class two.
Is it mainly a skeletal problem like a small lower jaw,
Is it mostly the upper teeth being too are forward
or some combination, And you also need.
Speaker 1 (16:02):
To factor in the patient's growth.
Speaker 2 (16:04):
Status critically important, are they still growing how much? That
dictates whether you can realistically aim for skeletal change or
if you're limited to tooth movement. Once you've answered those
diagnostic questions, the path towards the optimal appliance becomes much clearer.
Speaker 1 (16:21):
Okay, that makes perfect sense. Diagnosis drives the treatment choice.
Now that brings us towards the end and our final
provocative thought. We spend all this time talking about how
to correct the class to non compliantly, but what about
making sure it lasts?
Speaker 3 (16:34):
Yeah?
Speaker 2 (16:34):
Stability, ah, stability the long game. And this is where
soft tissue adaptation comes in, something that's maybe overlooked sometimes
in the rush to get the correction done. Soft tissues
like muscles and daga muscles, the purious deal attachments, all
the connective tissues around the jaws and teeth. The sources
issue a pretty strong warning here. The rate of class
to relapse things shifting back is often directly proportional to
(16:58):
how fast and how much correct you achieved initially.
Speaker 1 (17:01):
So faster isn't always better for long term success.
Speaker 2 (17:04):
Not necessarily because bone changes tooth movements can happen relatively
quickly with these fixed appliances, but the soft tissues adapt
much much slower if you take the appliance off before
those muscles and tissues have fully remodeled and accepted the
new jaw or tooth position.
Speaker 1 (17:20):
They can just pull things back to where they started.
Speaker 2 (17:22):
They can actively contribute to relapse. Yes, it's why concepts
like overcorrection, pushing slightly beyond the ideal endpoint initially and
then allowing adequate retention time for those soft tissues to
fully adapt are so critical for making the correction stick
long term.
Speaker 1 (17:37):
Fascinating, So the biology needs time to catch up with
the mechanics. That is a phenomenal point to end on. Okay,
to help cement to all this, let's do a quick
clinical synthesis challenge thinking about the specific device features we discussed.
Speaker 3 (17:49):
All right, let's test it.
Speaker 1 (17:50):
Imagine you have an eleven year old patient. Diagnosis confirms
a true retrognatic mandible SEW a significant skeletal component, and
this patient has a history of poor compliance with earlier,
simpler treatments. You decide mandated mandibular repositioning is needed now,
based purely on the documented effects and force characteristics we
(18:11):
talked about, Which appliance would you theoretically choose to best
address that skeletal issue. The rigid IRBs or the flexible Jasper.
Speaker 2 (18:20):
Jumper and why okay, good scenario. Given the true skeletal
retrognathism and the need for orthopedic change in a growing patient,
you would theoretically select.
Speaker 1 (18:29):
The herbs appliance and the reasoning.
Speaker 2 (18:31):
The crucial factor is the Earth's higher documented skeletal contribution.
Its rigid twenty four hour forced protrusion is specifically shown
to stimulate more significant condular growth and mandibular advancement compared
to the jumper. Remember, the Jasper jumper gets about sixty
percent of its effect for moving teeth, only forty.
Speaker 3 (18:48):
Percent skeletal right.
Speaker 1 (18:49):
This sixty to forty split.
Speaker 2 (18:50):
Exactly so when the primary goal is to address a
major underlying skeletal deficiency, the herbs, with its greater orthopedic
horse power, is the more direct and theoreally efficient choice.
Despite any potential downsides like bulkiness, the skeletal need points
strongly towards the herbs in this case
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