October 15, 2025 • 17 mins
A comprehensive overview of the orthodontic management of Class II malocclusion, detailing various treatment approaches and underlying biological concepts. They discuss the epidemiological and clinical features of Class II malocclusions, including the effects of non-nutritive sucking behaviors and the different subdivisions like Division 1 and Division 2. A significant portion of the text addresses treatment timing, weighing the evidence from randomized clinical trials (RCTs) regarding early two-phase treatment versus later single-phase treatment, and the challenges of predicting the mandibular growth spurt using methods like hand-wrist and cervical vertebral maturation. Furthermore, the sources examine the efficacy and side effects of different appliances, contrasting removable functional appliances like the Twin Block with various fixed functional appliances (e.g., Herbst, Forsus), and consider newer technologies such as clear aligners and skeletal anchorage devices. Finally, they explore treatment options for severe cases, including orthodontic-surgical management, and discuss ancillary considerations like the effect of treatment on the temporomandibular joint and its potential link to breathing disorders.
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Episode Transcript
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Speaker 1 (00:00):
Welcome back to the deep dive today. We are really
getting into it tackling one of the most common and
let's be honest, most debated topics and orthodonics, managing class
two malaclusion.
Speaker 2 (00:12):
That's right, And our goal here for you, the dental
professional or the really dedicated learner, is to kind of
cut through some of the noise, you know, especially around
growth modification. We're focusing purely on the solid quantitative data.
Speaker 1 (00:26):
Yeah, We've sifted through those big RCTs the meta analyzes.
Speaker 2 (00:30):
Exactly to give you a really structured summary of what
the evidence actually says works when and maybe why. We're
going deep on timing mechanics and those skeletal outcomes which
might surprise some people.
Speaker 1 (00:42):
Okay, sounds good. Let's start at the beginning. Then defining
class two. I know there are different types recognized for
like over a century.
Speaker 2 (00:49):
Now, yep, basically three main anthroposterior buckets. First up is
class two division one. That's probably the one most people picture.
You've got the lower incisors sitting behind a palatol to
the singulum of the other and.
Speaker 1 (01:00):
The uppers are usually tilted forward, proclined.
Speaker 2 (01:03):
Typically proclined, yeah, or sometimes average inclination. But the result
is that classic increased overjet.
Speaker 1 (01:08):
Okay, then there's an intermediate.
Speaker 2 (01:10):
Type sort of some classifications mention it. The upper incisors
might be more upright, maybe even a bit tipped back,
but you still have that increased overjet because of the
underlying jaw relationship.
Speaker 1 (01:22):
Got it? And the third one is class two Division two.
That looks quite different, doesn't it?
Speaker 2 (01:27):
Very distinct? The hallmark here is definitely the retrocline upper incisors.
They're tipped backwards. This often means the overjet looks minimal,
kind of tucked in.
Speaker 1 (01:36):
You still need to check the lowers.
Speaker 2 (01:38):
Always because the lower incisors can also be retroclined and
div two and if they are well, you might actually
still see an increased overjet despite the upper inciser position.
Speaker 1 (01:47):
It's tricky, okay. Eediology, let's talk about habits non nutritive
sucking and NSB. That always comes up. How clear is
the evidence differentiating say a pacifier from thumb sucking.
Speaker 2 (01:59):
Well, NNSB definitely plays a part. Those forces, the horizontal ones.
They can increase the maxillary arch length procline the incisors,
but the evidence does push us to be specific pacified
or use, for instance, seems less likely to cause a
big overjet in the baby teeth the primary dentician. Okay,
but it is linked with a higher risk of a
(02:20):
class two canine relationship developing and also posterior crossbite.
Speaker 1 (02:24):
What about digit sucking fingers thumbs.
Speaker 2 (02:28):
That seems to carry a bit more risk, especially if
it keeps going into the mixed dentition phase. We see
a measurably greater chance of posterior cross by it and
anterior open bite with persistent digit sucking.
Speaker 1 (02:39):
But if the habit stops.
Speaker 2 (02:41):
That's the crucial part. The occlusal effects generally tend to
lessen even resolve once the habit stops. Persistence is really
the key driver towards a lasting malaclusion.
Speaker 1 (02:52):
Right, Okay, let's think about young kids, say three to
seven years old. The literature makes a really interesting point
about when the occlusal signs appear versus the skeletal pattern.
Speaker 2 (03:01):
Yeah, this is vital for thinking about prognosis. You see
the occlusal features quite early on the discal step in
the molars. The class TK nine relationship often a narrow
uppy arch those are usually established, but.
Speaker 1 (03:12):
The jaw relationship itself, the skeletal part.
Speaker 2 (03:15):
That seems to develop a bit later, the full skeletal
class two pattern that mendibular retrognathia doesn't appear to be
fully locked in. During the deciduous dentition. You might see
signs like a smaller mandible or a steeper angle, but
it's still kind of evolving.
Speaker 1 (03:29):
And the bad news is it probably won't just fix
itself right.
Speaker 2 (03:33):
Unfortunately, No, that retruated mandibular position is pretty unlikely to
self correct just with growth. It tends to stick.
Speaker 1 (03:40):
Around in soft tissues.
Speaker 2 (03:41):
Player role here too, Oh massively think about division one.
If the lower lip gets trapped behind the upper incisors
a complete lip trap, it actively pushes those lower incisors
further back, retroclines them, and makes the overjet even worse.
And for DOV two in division two, a high lip
line is often considered a primary car the upper lip
constantly pressing on those incisors mechanically forces them into that
(04:04):
characteristic tipped back, retroclined position.
Speaker 1 (04:07):
Okay, So if self correction is unlikely, the big question
is when to treat. This brings us to the whole
growth modification debate. We know mandibular growth peaks roughly around
puberty twelve for girls fourteen for boys.
Speaker 2 (04:20):
Broadly, yes, it follows general height growth, but the peak
for the condyle doesn't line up exactly with the peak hepvelocity.
There's variability and trying.
Speaker 1 (04:29):
To pinpoint that peak, is it even possible accurately?
Speaker 2 (04:33):
Well, that's the problem. Methods like handwrist X rays they're
just not accurate enough. Plus there's the extra radiation dose,
so they're generally not justified anymore.
Speaker 1 (04:41):
What about CVM looking at the neck vertebrae.
Speaker 2 (04:44):
Cervical vertebral maturation is an alternative, sure, but the evidence
when you really look at it suggests it doesn't offer
any significant advantage over just using the patient's age to
predict that pubertal spurt. We're just not great at timing
it perfectly.
Speaker 1 (04:58):
Which makes those big randomized trials the US and UK
ones even more important. They compared treating early in the
mixed dentition versus just one phase of treatment in adolescence.
What was the verdict?
Speaker 2 (05:10):
It was pretty groundbreaking really, both approaches worked. Early treatment
corrected the class too reduce the overjet. Later single phase
treatment also corrected the class too and reduced the overjet.
Speaker 1 (05:21):
Okay, so what was the difference.
Speaker 2 (05:23):
The critical finding was that the later single phase treatment
needed fewer appointments overall and took slightly less total time.
Speaker 1 (05:31):
So that idea of catching the growth spurt with an
early phase, does it actually give you a significant skeletal
boost more jaw growth.
Speaker 2 (05:41):
This is probably the single biggest take home message. The
evidence supporting clinically significant additional mandibular growth just by timing
treatment to the spur is well, it's weak, very weak.
Oh week are we talking current data pooling? The best
studies suggests maybe at most an extra two millimeters of
annualized increase in total mandibular length if you treat during
(06:02):
the spark compared to before it.
Speaker 1 (06:04):
Two millimeters. That sounds tiny, especially when you factor in
the time and cost of two phase treatment.
Speaker 2 (06:09):
Exactly, it's really minimal from a clinical significance perspective. So
the accepted treatment effects what we reliably achieve are essentially
dental wal veular removing teeth. So the sensible strategy is
given that starting treatment in the late mixed dentition seems
most efficient. Avoid that early phase just for the sake
of chasing a minimal and frankly unsupported skiletal gain.
Speaker 1 (06:29):
Okay, if it's mainly dental wall veular let's dig into
the mechanics. What do the meta analyzes tell us about
the overall changes we get with functional appliances? What are
the reliable numbers?
Speaker 2 (06:41):
When you synthesize the data, you consistently see a statistically
significant drop in the amb angle. The mean difference is
around magnistry one point six degrees, and is that.
Speaker 1 (06:51):
From moving the max sylla back or the mandible forward.
Speaker 2 (06:54):
It seems to be more from bringing the mandible forward.
The increase in sm b angle is about plus so
undred and seven degrees, whereas the reduction in SNA the
maxillary effect is smaller, around a nine to point five degrees.
Speaker 1 (07:06):
Makes sense, but they're always side effects, right, especially dental
violer ones.
Speaker 2 (07:10):
Absolutely you typically see a slight opening rotation of the mandible.
The mandibular plane angle increases slightly about plus zero point
six degrees. But the big one, the most significant dental
side effect, is proclamation of the lower incisors. They tip
forward considerably. The average is about plus five point five degrees.
That's kind of the price you pay dentally for pushing
the mandible forward with these appliances.
Speaker 1 (07:32):
But you do get profile improvements.
Speaker 2 (07:34):
Yes, there's a definite soft tissue benefit. The mentalabial angle
that curve below the lower lip tends to improve significantly,
increases by over nineteen degrees on average.
Speaker 1 (07:43):
Okay, let's focus on specific appliances. The twin block is
a popular removable one. How does it stack up?
Speaker 2 (07:50):
It generally performs very well in studies. The evidence shows
it's significantly more effective at improving those key angles A
and B, SNA, S and B compared to older designs
like the Activator Bionator or the Frankle two.
Speaker 1 (08:04):
And for clinicians using it, any practical tips for the
byte registration that seems crucial.
Speaker 2 (08:09):
Super crucial. The goal is usually to advance the mandible
to reduce the overjet by about seventy or eighty percent
in that first step, though if you have a massive overjet,
say over fifteen millimeters, you might need to do it
in stages reactivate later, and the technique use a full
sheet of softened pink wax that lets you accurately see
and control the vertical opening. You need just enough clearance
(08:30):
for the blocks, but not so much that you cause
excessive posterior opening. Get that right, and then you monitor closely.
You should expect about one to two millimeters of overjet
and overbyte reduction every six weeks or so.
Speaker 1 (08:42):
What about when patient compliance with removables is a challenge,
fixed functionals like the IRBs or forces come into play.
Speaker 2 (08:49):
Right, Their main advantage is taking compliance out of the
equation they're cemented in, and.
Speaker 1 (08:53):
Their effects are still mostly denoiveolar primarily.
Speaker 2 (08:56):
Yes, you get retraction or distallization in the upper arch
and propclination or meusual movement in the lower arch.
Speaker 1 (09:02):
Now what about adding tads, skeletal anchorage, mini screws, mini plates.
The idea was maybe that boosts the skeletal effect of
fixed functionals.
Speaker 2 (09:10):
That was definitely the hope, but the research delivered a
bit of a plot twist. Adding skeletal anchorage to reinforce
fixed functional appliances showed no statistically significant effect on the
main skeletal outcomes A and B, SNB, SNA, menduralink. None
were significantly different compared to non anchored fixed functionals.
Speaker 1 (09:30):
No extra growth boost at all. So why use tads
with them?
Speaker 2 (09:33):
Because they did make a big difference with the unwanted
dental side effects. Specifically, they significantly reduced that lower inciser proclamation.
We're talking a difference of nearly eight degrees favoring the
tad reinforced group.
Speaker 1 (09:46):
Ah, So the benefit is purely about controlling the teeth,
preventing that forward flaring of the lowers exactly.
Speaker 2 (09:52):
It's about improving anchorage control, not enhancing skeletal change.
Speaker 1 (09:56):
Interesting. Okay, let's consider some other approaches. Headgear the classic
pulling back device. How does its effect compared directly to
functional appliances.
Speaker 2 (10:05):
Pushing forward headgear definitely has a much stronger restrictive effect
on the maxilla. Remember a functionals reduced SNA by about
net a zero point five degrees. Headgear achieves a significantly
greater reduction around madisc one point seven degrees.
Speaker 1 (10:19):
But it doesn't do much for the mandible.
Speaker 2 (10:21):
No significant effect on S and B, basically negligible change.
Its effects are things like rotating the palattal plane posteriorly
pulling a point back. So the choice really depends on
the diagnosis. The patient's specific pattern is the problem. Mostly
maxillary excess headgear might be better, mandibular deficiency functional might
be the primary choice.
Speaker 1 (10:43):
What about rapid maxillary expansion RME. I. Hear clinicians using
it sometimes for Class two, the theory being it unlocks
the bite lets the mandible come forward. Does that hold up?
Speaker 2 (10:52):
It's a common clinical idea, but unfortunately the high quality
evidence just isn't there. When you pull the RCT data,
r ME alone shows no statistically significant improvements in SNA, SMB, ANB,
or even mandibular length compared to untreated kids.
Speaker 1 (11:07):
So it doesn't reliably help correct the class to itself.
Speaker 2 (11:10):
Not robustly. No, it's great for cross bites obviously, but
not as a primary Class two corrector. Based on current.
Speaker 1 (11:16):
Evidence and those prefabricated milefunctional trainers things like the LM
activator myobrace.
Speaker 2 (11:20):
They seem popular, they are convenient, yes, but the meta
analysis comparing them to conventional custom made functional appliances suggests
they deliver well suboptimal results. For instance, the final amb
angle tends to be almost a degree higher, indicating less
correction compared to conventional appliances.
Speaker 1 (11:39):
So maybe easier to use but less effective.
Speaker 2 (11:41):
That seems to be the trade off according to the
current synthesis of evidence.
Speaker 1 (11:45):
And the newest kid on the block, clear aligners with
mandibular advancement features MA wings. What's the science saying there?
Speaker 2 (11:53):
Honestly, the current everything space is really weak. Most studies
are retrospective, small sample sizes, lots of highest potential. It's
very early days.
Speaker 1 (12:02):
Any preliminary hints, some.
Speaker 2 (12:03):
Initial, very low quality data hints that conventional functional appliances
might still produce more actual chin advancement, maybe about two
millimeters more and slightly better SMB improvement than the current
aligner m may features. But really we desperately need good
quality RCTs before we can say anything definitive.
Speaker 1 (12:19):
Fair enough, Okay, let's switch gears to older patients post pubertal,
where growth modification isn't really on the table. We're talking
camouflage masking the skeletal issue. If extractions are part of
that plan, what's the expected impact on the profile the lips.
Speaker 2 (12:36):
Extraction based camouflage generally results in more retruded lips, both
upper and lower. The nasal labial angle also tends to
increase become more obtuse by about two point eight degrees
on average.
Speaker 1 (12:46):
But is it always dramatic?
Speaker 2 (12:48):
Not necessarily. The important caveat is if the patient starts
with a borderline profile not too protrusive. The effect of
extractions on lip position is significantly less pronounced, and crucially,
predicting how much the lips will retract per millimeter of
incisor retraction is highly unpredictable. The range is huge, like
point twenty five millimeters up to point seven five milimeters
of lip change for every one millimeter the incisor moves back.
(13:11):
So it's not a simple recipe, not at all very
patient specific.
Speaker 1 (13:14):
Now let's bring it back to the core mechanics with
Johnson's picture analysis. Yeah, this really synthesizes things dovinte comparing
pushing the mandible forward versus pulling the maxilla back with
the distallizers. What's the big picture?
Speaker 2 (13:24):
The fundamental conclusion from that analysis is pretty clear. Pretty
much all Class two treatments in growing individuals work primarily
by interrupting the natural dental reveolar compensation. We're stopping the
teeth from adapting to the underlying skeletal.
Speaker 1 (13:39):
Imbalance, and the end result.
Speaker 2 (13:41):
The final skeletal and dental outcome is remarkably similar regardless
of how you did it. Functional appliance headgear distallizer pushing
the mandible forward with a functional parrot seems to get
about the same ultimate mandibular positional chains, maybe three to
four millimeters, as pulling the maxilla back with distalization allows
the mandible to express its growth, so.
Speaker 1 (14:03):
That extra mandibular growth we thought we were getting the.
Speaker 2 (14:06):
Actual additional mandibular enhancement. The true skeletal change beyond what
would have happened anyway compared to untreated controls, is likely
no more than one point six millimeters.
Speaker 1 (14:15):
Wow. Again, really minimal biological difference.
Speaker 2 (14:18):
Precisely, it underscores that our main power lies in managing
the dental veolar changes effectively.
Speaker 1 (14:24):
Which logically leads to the question, when is camouflage just
not enough?
Speaker 2 (14:28):
Yeah?
Speaker 1 (14:28):
When is surgery the clear answer?
Speaker 2 (14:30):
For the more severe skeletal discrepancies. Definitely, where trying to
camouflage would lead to a compromise facial profile or unstable occlusion,
a combined orthodonic surgical approach is superior. It gives better
skeletal correction, a more stable and ideal bite, more harmonious profile,
and often it's actually faster overall than trying to push
(14:50):
the limits of camouflage.
Speaker 1 (14:51):
Let's touch quickly on some broader effects. Airway, is there
a link between Class two and airway size.
Speaker 2 (14:57):
Yes, the evidence suggests there is.
Speaker 1 (14:59):
Two.
Speaker 2 (15:00):
Macclusion is generally associated with significantly smaller upper airway volumes, nasal, cavity, pharynx.
Speaker 1 (15:06):
And does treatment help.
Speaker 2 (15:08):
Interestingly, yes, functional appliance treatment is associated with significant increases
in various airway dimensions. For example, the ore faranx volume
showed a substantial increase in treated patients over twenty three
hundred cubic millimeters on average in one meta analysis.
Speaker 1 (15:23):
That's quite striking. What about the TMJ the jaw joint.
Are we potentially harming it by pushing the mandible forward?
Speaker 2 (15:29):
The evidence actually points the other way. Functional appliances lead
to an anterior and inferior repositioning of the condyle in
the fossa and potentially increased condolar growth pain. One important
RCT actually found that kids treated with functional appliances reported
significantly less TMJ pain compared to untreated Class two kids.
The ODDS ratio was b three to two, suggesting a
(15:51):
potentially protective effect rather than a harmful one.
Speaker 1 (15:55):
Okay, so let's think long term stability. Do these changes
hold up after treatment?
Speaker 2 (16:01):
Well, some of the accelerated growth seen during functional appliance.
Treatment might be transient, growth might slow down a bit afterward,
but when you compare treated patients to untreated Class two
individuals long term, say three plus years post retention, the
treated groups still shows significant differences. They tend to maintain
a significantly smaller sna angle meaning the maxillary restriction holds
(16:23):
to some extent, and a significantly larger effective mandibular length
comin by about two millimeters on average. So there are
lasting beneficial changes compared to doing nothing.
Speaker 1 (16:33):
So wrapping this all up, this deep dive really highlights
that while we have many tools, the idea of dramatically
altering skele little growth is well maybe overstated. Timing doesn't
seem to unlock huge amounts of extra growth, and most
of what we achieve in growing patients is really skillful
management of the dental vewolder compensation.
Speaker 2 (16:52):
Absolutely, it comes back to basing our decisions on the
patient's actual phenotype, is it a maxillary or mandibular issue,
and relying on the robust evidence. Knowing that the true
skeletal enhancement is likely limited to that one point six
milimeter range helps manage expectations both ours and the patients and.
Speaker 1 (17:10):
It focuses attention on managing the predictable dental veolar effects
like that lower incisor proclamation exactly.
Speaker 2 (17:17):
It's about effective, predictable orthodontics based on what the science
actually supports.
Speaker 1 (17:21):
Okay. To help everyone consolidate this, particularly the points about
anchorage control, here's a short review question.
Speaker 2 (17:27):
For you to ponder prompt Imagine you're treating a non
growing class to patient. You decide on maxillary arch distilization,
but instead of using tads, you opt for a conventional
toothborn intraoral appliance. Based on what we've discussed today, what
specific unwanted effect should you be most vigilant about managing
with the conventional appliance And thinking back to the TAD comparison,
(17:49):
what specific adverse dental alveolar effect and the lower arched
is Using skeletal anchorage like tads with a fixed functional
help minimize even though it doesn't boost the overall skeletal correction,
Welcome back to the deep dive today. We are really
getting into it tackling one of the most common and
let's be honest, most debated topics and orthodonics, managing class
two malaclusion.
Speaker 2 (00:12):
That's right, And our goal here for you, the dental
professional or the really dedicated learner, is to kind of
cut through some of the noise, you know, especially around
growth modification. We're focusing purely on the solid quantitative data.
Speaker 1 (00:26):
Yeah, We've sifted through those big RCTs the meta analyzes.
Speaker 2 (00:30):
Exactly to give you a really structured summary of what
the evidence actually says works when and maybe why. We're
going deep on timing mechanics and those skeletal outcomes which
might surprise some people.
Speaker 1 (00:42):
Okay, sounds good. Let's start at the beginning. Then defining
class two. I know there are different types recognized for
like over a century.
Speaker 2 (00:49):
Now, yep, basically three main anthroposterior buckets. First up is
class two division one. That's probably the one most people picture.
You've got the lower incisors sitting behind a palatol to
the singulum of the other and.
Speaker 1 (01:00):
The uppers are usually tilted forward, proclined.
Speaker 2 (01:03):
Typically proclined, yeah, or sometimes average inclination. But the result
is that classic increased overjet.
Speaker 1 (01:08):
Okay, then there's an intermediate.
Speaker 2 (01:10):
Type sort of some classifications mention it. The upper incisors
might be more upright, maybe even a bit tipped back,
but you still have that increased overjet because of the
underlying jaw relationship.
Speaker 1 (01:22):
Got it? And the third one is class two Division two.
That looks quite different, doesn't it?
Speaker 2 (01:27):
Very distinct? The hallmark here is definitely the retrocline upper incisors.
They're tipped backwards. This often means the overjet looks minimal,
kind of tucked in.
Speaker 1 (01:36):
You still need to check the lowers.
Speaker 2 (01:38):
Always because the lower incisors can also be retroclined and
div two and if they are well, you might actually
still see an increased overjet despite the upper inciser position.
Speaker 1 (01:47):
It's tricky, okay. Eediology, let's talk about habits non nutritive
sucking and NSB. That always comes up. How clear is
the evidence differentiating say a pacifier from thumb sucking.
Speaker 2 (01:59):
Well, NNSB definitely plays a part. Those forces, the horizontal ones.
They can increase the maxillary arch length procline the incisors,
but the evidence does push us to be specific pacified
or use, for instance, seems less likely to cause a
big overjet in the baby teeth the primary dentician. Okay,
but it is linked with a higher risk of a
(02:20):
class two canine relationship developing and also posterior crossbite.
Speaker 1 (02:24):
What about digit sucking fingers thumbs.
Speaker 2 (02:28):
That seems to carry a bit more risk, especially if
it keeps going into the mixed dentition phase. We see
a measurably greater chance of posterior cross by it and
anterior open bite with persistent digit sucking.
Speaker 1 (02:39):
But if the habit stops.
Speaker 2 (02:41):
That's the crucial part. The occlusal effects generally tend to
lessen even resolve once the habit stops. Persistence is really
the key driver towards a lasting malaclusion.
Speaker 1 (02:52):
Right, Okay, let's think about young kids, say three to
seven years old. The literature makes a really interesting point
about when the occlusal signs appear versus the skeletal pattern.
Speaker 2 (03:01):
Yeah, this is vital for thinking about prognosis. You see
the occlusal features quite early on the discal step in
the molars. The class TK nine relationship often a narrow
uppy arch those are usually established, but.
Speaker 1 (03:12):
The jaw relationship itself, the skeletal part.
Speaker 2 (03:15):
That seems to develop a bit later, the full skeletal
class two pattern that mendibular retrognathia doesn't appear to be
fully locked in. During the deciduous dentition. You might see
signs like a smaller mandible or a steeper angle, but
it's still kind of evolving.
Speaker 1 (03:29):
And the bad news is it probably won't just fix
itself right.
Speaker 2 (03:33):
Unfortunately, No, that retruated mandibular position is pretty unlikely to
self correct just with growth. It tends to stick.
Speaker 1 (03:40):
Around in soft tissues.
Speaker 2 (03:41):
Player role here too, Oh massively think about division one.
If the lower lip gets trapped behind the upper incisors
a complete lip trap, it actively pushes those lower incisors
further back, retroclines them, and makes the overjet even worse.
And for DOV two in division two, a high lip
line is often considered a primary car the upper lip
constantly pressing on those incisors mechanically forces them into that
(04:04):
characteristic tipped back, retroclined position.
Speaker 1 (04:07):
Okay, So if self correction is unlikely, the big question
is when to treat. This brings us to the whole
growth modification debate. We know mandibular growth peaks roughly around
puberty twelve for girls fourteen for boys.
Speaker 2 (04:20):
Broadly, yes, it follows general height growth, but the peak
for the condyle doesn't line up exactly with the peak hepvelocity.
There's variability and trying.
Speaker 1 (04:29):
To pinpoint that peak, is it even possible accurately?
Speaker 2 (04:33):
Well, that's the problem. Methods like handwrist X rays they're
just not accurate enough. Plus there's the extra radiation dose,
so they're generally not justified anymore.
Speaker 1 (04:41):
What about CVM looking at the neck vertebrae.
Speaker 2 (04:44):
Cervical vertebral maturation is an alternative, sure, but the evidence
when you really look at it suggests it doesn't offer
any significant advantage over just using the patient's age to
predict that pubertal spurt. We're just not great at timing
it perfectly.
Speaker 1 (04:58):
Which makes those big randomized trials the US and UK
ones even more important. They compared treating early in the
mixed dentition versus just one phase of treatment in adolescence.
What was the verdict?
Speaker 2 (05:10):
It was pretty groundbreaking really, both approaches worked. Early treatment
corrected the class too reduce the overjet. Later single phase
treatment also corrected the class too and reduced the overjet.
Speaker 1 (05:21):
Okay, so what was the difference.
Speaker 2 (05:23):
The critical finding was that the later single phase treatment
needed fewer appointments overall and took slightly less total time.
Speaker 1 (05:31):
So that idea of catching the growth spurt with an
early phase, does it actually give you a significant skeletal
boost more jaw growth.
Speaker 2 (05:41):
This is probably the single biggest take home message. The
evidence supporting clinically significant additional mandibular growth just by timing
treatment to the spur is well, it's weak, very weak.
Oh week are we talking current data pooling? The best
studies suggests maybe at most an extra two millimeters of
annualized increase in total mandibular length if you treat during
(06:02):
the spark compared to before it.
Speaker 1 (06:04):
Two millimeters. That sounds tiny, especially when you factor in
the time and cost of two phase treatment.
Speaker 2 (06:09):
Exactly, it's really minimal from a clinical significance perspective. So
the accepted treatment effects what we reliably achieve are essentially
dental wal veular removing teeth. So the sensible strategy is
given that starting treatment in the late mixed dentition seems
most efficient. Avoid that early phase just for the sake
of chasing a minimal and frankly unsupported skiletal gain.
Speaker 1 (06:29):
Okay, if it's mainly dental wall veular let's dig into
the mechanics. What do the meta analyzes tell us about
the overall changes we get with functional appliances? What are
the reliable numbers?
Speaker 2 (06:41):
When you synthesize the data, you consistently see a statistically
significant drop in the amb angle. The mean difference is
around magnistry one point six degrees, and is that.
Speaker 1 (06:51):
From moving the max sylla back or the mandible forward.
Speaker 2 (06:54):
It seems to be more from bringing the mandible forward.
The increase in sm b angle is about plus so
undred and seven degrees, whereas the reduction in SNA the
maxillary effect is smaller, around a nine to point five degrees.
Speaker 1 (07:06):
Makes sense, but they're always side effects, right, especially dental
violer ones.
Speaker 2 (07:10):
Absolutely you typically see a slight opening rotation of the mandible.
The mandibular plane angle increases slightly about plus zero point
six degrees. But the big one, the most significant dental
side effect, is proclamation of the lower incisors. They tip
forward considerably. The average is about plus five point five degrees.
That's kind of the price you pay dentally for pushing
the mandible forward with these appliances.
Speaker 1 (07:32):
But you do get profile improvements.
Speaker 2 (07:34):
Yes, there's a definite soft tissue benefit. The mentalabial angle
that curve below the lower lip tends to improve significantly,
increases by over nineteen degrees on average.
Speaker 1 (07:43):
Okay, let's focus on specific appliances. The twin block is
a popular removable one. How does it stack up?
Speaker 2 (07:50):
It generally performs very well in studies. The evidence shows
it's significantly more effective at improving those key angles A
and B, SNA, S and B compared to older designs
like the Activator Bionator or the Frankle two.
Speaker 1 (08:04):
And for clinicians using it, any practical tips for the
byte registration that seems crucial.
Speaker 2 (08:09):
Super crucial. The goal is usually to advance the mandible
to reduce the overjet by about seventy or eighty percent
in that first step, though if you have a massive overjet,
say over fifteen millimeters, you might need to do it
in stages reactivate later, and the technique use a full
sheet of softened pink wax that lets you accurately see
and control the vertical opening. You need just enough clearance
(08:30):
for the blocks, but not so much that you cause
excessive posterior opening. Get that right, and then you monitor closely.
You should expect about one to two millimeters of overjet
and overbyte reduction every six weeks or so.
Speaker 1 (08:42):
What about when patient compliance with removables is a challenge,
fixed functionals like the IRBs or forces come into play.
Speaker 2 (08:49):
Right, Their main advantage is taking compliance out of the
equation they're cemented in, and.
Speaker 1 (08:53):
Their effects are still mostly denoiveolar primarily.
Speaker 2 (08:56):
Yes, you get retraction or distallization in the upper arch
and propclination or meusual movement in the lower arch.
Speaker 1 (09:02):
Now what about adding tads, skeletal anchorage, mini screws, mini plates.
The idea was maybe that boosts the skeletal effect of
fixed functionals.
Speaker 2 (09:10):
That was definitely the hope, but the research delivered a
bit of a plot twist. Adding skeletal anchorage to reinforce
fixed functional appliances showed no statistically significant effect on the
main skeletal outcomes A and B, SNB, SNA, menduralink. None
were significantly different compared to non anchored fixed functionals.
Speaker 1 (09:30):
No extra growth boost at all. So why use tads
with them?
Speaker 2 (09:33):
Because they did make a big difference with the unwanted
dental side effects. Specifically, they significantly reduced that lower inciser proclamation.
We're talking a difference of nearly eight degrees favoring the
tad reinforced group.
Speaker 1 (09:46):
Ah, So the benefit is purely about controlling the teeth,
preventing that forward flaring of the lowers exactly.
Speaker 2 (09:52):
It's about improving anchorage control, not enhancing skeletal change.
Speaker 1 (09:56):
Interesting. Okay, let's consider some other approaches. Headgear the classic
pulling back device. How does its effect compared directly to
functional appliances.
Speaker 2 (10:05):
Pushing forward headgear definitely has a much stronger restrictive effect
on the maxilla. Remember a functionals reduced SNA by about
net a zero point five degrees. Headgear achieves a significantly
greater reduction around madisc one point seven degrees.
Speaker 1 (10:19):
But it doesn't do much for the mandible.
Speaker 2 (10:21):
No significant effect on S and B, basically negligible change.
Its effects are things like rotating the palattal plane posteriorly
pulling a point back. So the choice really depends on
the diagnosis. The patient's specific pattern is the problem. Mostly
maxillary excess headgear might be better, mandibular deficiency functional might
be the primary choice.
Speaker 1 (10:43):
What about rapid maxillary expansion RME. I. Hear clinicians using
it sometimes for Class two, the theory being it unlocks
the bite lets the mandible come forward. Does that hold up?
Speaker 2 (10:52):
It's a common clinical idea, but unfortunately the high quality
evidence just isn't there. When you pull the RCT data,
r ME alone shows no statistically significant improvements in SNA, SMB, ANB,
or even mandibular length compared to untreated kids.
Speaker 1 (11:07):
So it doesn't reliably help correct the class to itself.
Speaker 2 (11:10):
Not robustly. No, it's great for cross bites obviously, but
not as a primary Class two corrector. Based on current.
Speaker 1 (11:16):
Evidence and those prefabricated milefunctional trainers things like the LM
activator myobrace.
Speaker 2 (11:20):
They seem popular, they are convenient, yes, but the meta
analysis comparing them to conventional custom made functional appliances suggests
they deliver well suboptimal results. For instance, the final amb
angle tends to be almost a degree higher, indicating less
correction compared to conventional appliances.
Speaker 1 (11:39):
So maybe easier to use but less effective.
Speaker 2 (11:41):
That seems to be the trade off according to the
current synthesis of evidence.
Speaker 1 (11:45):
And the newest kid on the block, clear aligners with
mandibular advancement features MA wings. What's the science saying there?
Speaker 2 (11:53):
Honestly, the current everything space is really weak. Most studies
are retrospective, small sample sizes, lots of highest potential. It's
very early days.
Speaker 1 (12:02):
Any preliminary hints, some.
Speaker 2 (12:03):
Initial, very low quality data hints that conventional functional appliances
might still produce more actual chin advancement, maybe about two
millimeters more and slightly better SMB improvement than the current
aligner m may features. But really we desperately need good
quality RCTs before we can say anything definitive.
Speaker 1 (12:19):
Fair enough, Okay, let's switch gears to older patients post pubertal,
where growth modification isn't really on the table. We're talking
camouflage masking the skeletal issue. If extractions are part of
that plan, what's the expected impact on the profile the lips.
Speaker 2 (12:36):
Extraction based camouflage generally results in more retruded lips, both
upper and lower. The nasal labial angle also tends to
increase become more obtuse by about two point eight degrees
on average.
Speaker 1 (12:46):
But is it always dramatic?
Speaker 2 (12:48):
Not necessarily. The important caveat is if the patient starts
with a borderline profile not too protrusive. The effect of
extractions on lip position is significantly less pronounced, and crucially,
predicting how much the lips will retract per millimeter of
incisor retraction is highly unpredictable. The range is huge, like
point twenty five millimeters up to point seven five milimeters
of lip change for every one millimeter the incisor moves back.
(13:11):
So it's not a simple recipe, not at all very
patient specific.
Speaker 1 (13:14):
Now let's bring it back to the core mechanics with
Johnson's picture analysis. Yeah, this really synthesizes things dovinte comparing
pushing the mandible forward versus pulling the maxilla back with
the distallizers. What's the big picture?
Speaker 2 (13:24):
The fundamental conclusion from that analysis is pretty clear. Pretty
much all Class two treatments in growing individuals work primarily
by interrupting the natural dental reveolar compensation. We're stopping the
teeth from adapting to the underlying skeletal.
Speaker 1 (13:39):
Imbalance, and the end result.
Speaker 2 (13:41):
The final skeletal and dental outcome is remarkably similar regardless
of how you did it. Functional appliance headgear distallizer pushing
the mandible forward with a functional parrot seems to get
about the same ultimate mandibular positional chains, maybe three to
four millimeters, as pulling the maxilla back with distalization allows
the mandible to express its growth, so.
Speaker 1 (14:03):
That extra mandibular growth we thought we were getting the.
Speaker 2 (14:06):
Actual additional mandibular enhancement. The true skeletal change beyond what
would have happened anyway compared to untreated controls, is likely
no more than one point six millimeters.
Speaker 1 (14:15):
Wow. Again, really minimal biological difference.
Speaker 2 (14:18):
Precisely, it underscores that our main power lies in managing
the dental veolar changes effectively.
Speaker 1 (14:24):
Which logically leads to the question, when is camouflage just
not enough?
Speaker 2 (14:28):
Yeah?
Speaker 1 (14:28):
When is surgery the clear answer?
Speaker 2 (14:30):
For the more severe skeletal discrepancies. Definitely, where trying to
camouflage would lead to a compromise facial profile or unstable occlusion,
a combined orthodonic surgical approach is superior. It gives better
skeletal correction, a more stable and ideal bite, more harmonious profile,
and often it's actually faster overall than trying to push
(14:50):
the limits of camouflage.
Speaker 1 (14:51):
Let's touch quickly on some broader effects. Airway, is there
a link between Class two and airway size.
Speaker 2 (14:57):
Yes, the evidence suggests there is.
Speaker 1 (14:59):
Two.
Speaker 2 (15:00):
Macclusion is generally associated with significantly smaller upper airway volumes, nasal, cavity, pharynx.
Speaker 1 (15:06):
And does treatment help.
Speaker 2 (15:08):
Interestingly, yes, functional appliance treatment is associated with significant increases
in various airway dimensions. For example, the ore faranx volume
showed a substantial increase in treated patients over twenty three
hundred cubic millimeters on average in one meta analysis.
Speaker 1 (15:23):
That's quite striking. What about the TMJ the jaw joint.
Are we potentially harming it by pushing the mandible forward?
Speaker 2 (15:29):
The evidence actually points the other way. Functional appliances lead
to an anterior and inferior repositioning of the condyle in
the fossa and potentially increased condolar growth pain. One important
RCT actually found that kids treated with functional appliances reported
significantly less TMJ pain compared to untreated Class two kids.
The ODDS ratio was b three to two, suggesting a
(15:51):
potentially protective effect rather than a harmful one.
Speaker 1 (15:55):
Okay, so let's think long term stability. Do these changes
hold up after treatment?
Speaker 2 (16:01):
Well, some of the accelerated growth seen during functional appliance.
Treatment might be transient, growth might slow down a bit afterward,
but when you compare treated patients to untreated Class two
individuals long term, say three plus years post retention, the
treated groups still shows significant differences. They tend to maintain
a significantly smaller sna angle meaning the maxillary restriction holds
(16:23):
to some extent, and a significantly larger effective mandibular length
comin by about two millimeters on average. So there are
lasting beneficial changes compared to doing nothing.
Speaker 1 (16:33):
So wrapping this all up, this deep dive really highlights
that while we have many tools, the idea of dramatically
altering skele little growth is well maybe overstated. Timing doesn't
seem to unlock huge amounts of extra growth, and most
of what we achieve in growing patients is really skillful
management of the dental vewolder compensation.
Speaker 2 (16:52):
Absolutely, it comes back to basing our decisions on the
patient's actual phenotype, is it a maxillary or mandibular issue,
and relying on the robust evidence. Knowing that the true
skeletal enhancement is likely limited to that one point six
milimeter range helps manage expectations both ours and the patients and.
Speaker 1 (17:10):
It focuses attention on managing the predictable dental veolar effects
like that lower incisor proclamation exactly.
Speaker 2 (17:17):
It's about effective, predictable orthodontics based on what the science
actually supports.
Speaker 1 (17:21):
Okay. To help everyone consolidate this, particularly the points about
anchorage control, here's a short review question.
Speaker 2 (17:27):
For you to ponder prompt Imagine you're treating a non
growing class to patient. You decide on maxillary arch distilization,
but instead of using tads, you opt for a conventional
toothborn intraoral appliance. Based on what we've discussed today, what
specific unwanted effect should you be most vigilant about managing
with the conventional appliance And thinking back to the TAD comparison,
(17:49):
what specific adverse dental alveolar effect and the lower arched
is Using skeletal anchorage like tads with a fixed functional
help minimize even though it doesn't boost the overall skeletal correction,
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