June 28, 2026 • 21 mins
A visual, practical guide for dental professionals learning the Biofunctional Prosthetic System for creating high-quality dentures. Instead of relying on dense scientific text, the author utilizes detailed photography and simplified instructions to walk clinicians through a complex Class 2 dental case. The provided excerpts specifically highlight the initial stages of treatment, focusing on the clinical examination of the patient's oral anatomy and the importance of accurate tissue palpation. It further details the technical process for taking preliminary impressions, emphasizing the use of specific injection techniques and alginate materials to ensure a stable fit. By prioritizing image-based learning, the source aims to help practitioners master the specialized tools and protocols required for successful removable prosthetics.
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https://linktr.ee/dentistry_made_simple
Produced by:
https://www.podcaistudio.com/
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:01):
What if I told you that the secret to a
perfectly stable lower denture has like absolutely nothing to do
with the job bone itself and literally everything to do
with the floor of the mouth.
Speaker 2 (00:11):
I mean it sounds completely counterintuitive, but especially if you
spend your days just staring at severe bone loss on
panoramic X rays. Yeah, exactly, But in the realm of
removable prosthetics, the behavior of the soft tissue really dictates
almost everything about your final success.
Speaker 1 (00:26):
Okay, let's unpack this because that is a massive paradigm shift.
Today we are talking directly to you, whether you're a
dental student grinding through your very first complete denture cases,
a young professional trying to refine your chair side technique,
or just a deeply curious self learner fascinated by the
engineering of the human mouth. We're taking a comprehensive start
(00:48):
to finish masterclass on handling class two removable prosthetics.
Speaker 2 (00:53):
Which is notoriously one of the most challenging classes of
identialist cases. I mean, the requirements for getting a functional
in prision, determining the occlusal plane without natural teeth as guides,
and then arranging the artificial teeth.
Speaker 1 (01:06):
It's a lot.
Speaker 2 (01:07):
It is. It presents incredible hurdles for both the clinician
and the laboratory technician.
Speaker 1 (01:12):
And to conquer those hurdles, we're relying on a highly visual,
incredibly practical source. It's called BPS Step by Step by
Joseph PERTONI. Yes, it details the BPS SEMCD system that
stands for suction effective mandibular Complete Denture, which is a
philosophy pioneered by Professor Giro Abe and developed by.
Speaker 2 (01:33):
Ivaclor right the Abe technique exactly.
Speaker 1 (01:36):
And our mission for this deep dive today is to
extract every critical detail from this workflow, like no skipped steps.
We are breaking down the science from the exact moment
the patient opens their mouth to the final polish of
the teeth.
Speaker 2 (01:49):
And you know the real value of Ratoni's guide is
that it removes the guesswork. It bridges that gap between
what happens in the dental chair and what happens in
the lab, proving that essentially le aesthetics rely entirely on
invisible structural preparation.
Speaker 1 (02:03):
Well, let's dive right into that preparation. Then, before we
even think about mixing a single drop of impression material,
we have to read the terrain of the patient's mouth.
I like to think of this like a surveyor mapping
out a plot of land before laying a foundation, Like
if you miss a hidden sinkle, it really doesn't matter
how beautiful the house is, right, the whole thing just collapses.
Speaker 2 (02:22):
That's a great way to look at it. And the
primary tools for this survey are visualization and critically manual palpation.
You literally have to physically feel the anatomical landmarks.
Speaker 1 (02:36):
So starting on the upper arch, what are we feeling for?
Speaker 2 (02:39):
Well, you start by palpating the tuberosities at the very
back of the ridge. You're actively checking like is this
a solid, bony base or are these flabby, boneless moving tubers.
Speaker 1 (02:50):
Because moving tissue can't support the.
Speaker 2 (02:51):
Load exactly, moving tissue cannot support a vertical load. Then
you also evaluate the zygramatic arch on the side.
Speaker 1 (02:58):
It's just pretty hard and bony.
Speaker 2 (03:00):
Usually, yes, the zygomatic arch is hard. It can actually
provide excellent support for the denture base. However, if that
arch is highly prominent, you must mark it on your
initial assessment.
Speaker 1 (03:09):
Wait, why is that so critical to mark?
Speaker 2 (03:11):
Because you have to communicate that prominence to the technician.
They have to actively avoid it when designing the custom tray.
If the rigid tray hits a prominent zygomatic arch, it
will instantly dislodge the impression and later the denture itself
will just pop right out.
Speaker 1 (03:29):
Oh wow. It's like finding a massive boulder right where
you want to pour your concrete footing exactly.
Speaker 2 (03:34):
You just have to design the architecture around it. And
checking the front of the upper ridge works the same way.
Speaker 1 (03:39):
Right. Figuring out if the anterior ridge is bony or flabby.
Speaker 2 (03:42):
Yeah, because that totally dictates your pressure later. But let's
move down to the lower ridge, which is the notorious
trouble spot for everyone.
Speaker 1 (03:50):
Yeah. Lower dentures are the bane of dental students everywhere, they.
Speaker 2 (03:54):
Really are, but the lower is where the HESEMCD system
really shines. So achieving reliable lower section starts with the
retromolar pads at the back of the mannible. Again, check
if they're bony or movable. Okay, Then you need to
establish the actual width of your foundation. You do this
by finding the distance between the mila hyderidges on the
lingual side the inside right right the inside, and the
(04:17):
linear obliqua externa on the buckle or cheek side.
Speaker 1 (04:21):
Okay, and then the source details this technique called the
sublingual test, which honestly seems to be the absolute make
or break moment for this entire suction philosophy.
Speaker 2 (04:30):
Oh, it is the defining test. So you ask the
patient to raise their tongue to their palate and then
move the tip of their.
Speaker 1 (04:36):
Tongue left and right while you just watch.
Speaker 2 (04:38):
While you are intensely observing the floor of the mouth,
the sublingual.
Speaker 1 (04:42):
Area, and what determines a pass or fail here, what
are we looking for?
Speaker 2 (04:46):
You're watching the tissue dynamics. So if the sublingual tissue
actively follows the movements of the tongue, it indicates a
lack of spongy tissue. It's taut, which means it's hard
to seal, very difficult to seal. But if that sublingual TOI,
she remains completely passive and has this like glandular soft
structure the jackpot, it is a massive advantage that passive
(05:08):
spongy tissue will naturally drape over the borders of the.
Speaker 1 (05:11):
Denture base like a natural gasket.
Speaker 2 (05:13):
Exactly like a gasket, It seals the lower denture against
the floor of the mouth regardless of how the patient
moves their tongue.
Speaker 1 (05:20):
I love that gasket metaphor. You also check the menam area.
Speaker 2 (05:23):
Right the chin, Yeah, by gently pulling the lower lip
to observe the lip seal muscles. And you also check
for macroglossy, which is just an extra wide tongue.
Speaker 1 (05:32):
And that ties directly into Pounds rule, right, it does.
Speaker 2 (05:34):
Pounds rule defines the necessary living space for the tongue
in the lower arch. You must preserve a trapezoid shaped free.
Speaker 1 (05:42):
Area where exactly is this trapezoid.
Speaker 2 (05:44):
It's located between the lingle walls of the lower retromolar
pads at the back, and it narrows toward the measual
contact point of the artificial canines in the front.
Speaker 1 (05:53):
So if you encroach on that space, if.
Speaker 2 (05:55):
You encroach on this trapezoid with thick acrylic or poorly
placed teeth, the tongue feels cramped. It will just constantly
fight to dislodge the denture.
Speaker 1 (06:04):
Okay, so we've mapped our bedrock, found our sinkholes, identified
our natural gaskets. But the mouth isn't a static piece
of stone. It moves, it flexes, it gags. How do
we capture that dynamic environment without distorting the tissues we
just mapped.
Speaker 2 (06:19):
That requires a highly specific preliminary impression technique. For the
upper the author relies on shrine maker's trays, and for
the lower the ideal tool is doctor Jiro Abe's FCB tray.
That's frame cutback tray designed specifically to capture that sublingle
fold we just talked about.
Speaker 1 (06:36):
Oh, if the patient has a really severe gag reflex,
the book mentions falling back on a lower shrine maker's tray.
Speaker 2 (06:42):
Right, Yeah, sometimes you have to adapt. But you don't
just guess the tray size either, Right.
Speaker 1 (06:47):
You take a measuring caliber. You literally measure the exact
distance between the buckle walls of the upper tuberosities and
match that perfectly to the tray.
Speaker 2 (06:55):
With exactly no guessing.
Speaker 1 (06:57):
But the part of this that really caught my eye
is the chemistry of the algenate mix. It's called a
two layer, one phase injected technique.
Speaker 2 (07:04):
What's fascinating here is the deliberate manipulation of setting times.
You use two different types of algenate simultaneously.
Speaker 1 (07:11):
Really at the exact same time.
Speaker 2 (07:13):
Yes, First, the syringe material, this is an injectable long
setting algenate like neocoloid. You mix this and load into
a large thirty five to fifty milli meters central tip syringe. Okay, Meanwhile,
you mix the tray material, which is a regular setting
algenate like hydrocolor five.
Speaker 1 (07:30):
So we are essentially manipulating time here. The syringe material
sets slowly, so you have the freedom to maneuver around
the vestibules, while the tray material sets faster, so the
patient isn't sitting there gagging for ten minutes.
Speaker 2 (07:42):
That is the exact mechanism. It's brilliant, but there is
a massive caveat regarding the powder measurement. The author stresses
in all caps that a cap of algenate must be.
Speaker 1 (07:53):
A flat cap, meaning you can't pack it in.
Speaker 2 (07:56):
It can never be condensed. If you tap the scoop
against the side of the content to pack more powder in,
you fundamentally alter the water to powder ratio.
Speaker 1 (08:04):
Which throws off the dimensional stability of the impression.
Speaker 2 (08:07):
Once it cures, it completely ruins the consistency. So once
it's perfectly mixed, you start with the syringe. You inject
the neo colloid continuously into the upper for nex area.
Speaker 1 (08:18):
You just keep moving.
Speaker 2 (08:19):
Yeah, you must be brave and keep the material flowing
to prevent any air bubbles from forming. And you also
add a tiny peanut sized drop directly onto the incisive
papilla to capture that crucial landmark perfectly.
Speaker 1 (08:32):
And when you finally insert the loaded tray, the source
offers this brilliant biomechanical tip that I loved. You don't
hold the tray by the front handle.
Speaker 2 (08:40):
Yes, when you seat the upper tray, you support the
center of the palatal area with your fingertip.
Speaker 1 (08:46):
Because if you push from the handle, you basically create
a giant lever.
Speaker 2 (08:49):
Right, you end up over pushing the front and lifting
the backup completely, which distorts the impression depth. Center pressure
guarantees an even anatomical distribution.
Speaker 1 (09:00):
Makes perfect sense. And that perfect anatomical model brings us
to the next massive challenge. We have the upper, we
have the lower, but how do they relate to each other?
The jaw moves in three dimensions.
Speaker 2 (09:10):
And without teeth you have no vertical dimension of occlusion.
Speaker 1 (09:14):
Here's where it gets really interesting to me. The source
uses a closed mouth, a clusodynamic impression technique with something
called accentric tray, but the book relies heavily on mathematical
measurements to mount these casts. My question is how does
this rigid math work on a patient whose jawbone has
severely resorbed over decades.
Speaker 2 (09:33):
It works because the BPS system anchors itself to anatomical
landmarks that defy bone resorption. What do you mean, Well,
the alveolar ridge might melt away over the years, but
certain points remain in approximately the exact same functional position.
The first point is this sagital third of the retromolar pads. Okay,
this point sits at the exact same vertical position as
(09:55):
the last molar distal cusps used to no matter how much.
Speaker 1 (09:59):
Bone is lost.
Speaker 2 (10:00):
And the second point the virtual symphesis point. This is
the contact point of the first lower incisors and it
lies directly on the midline over the tuberculum mentalis.
Speaker 1 (10:10):
Okay, so how does that help us with the math?
Speaker 2 (10:12):
The mathematical genius here is that the virtual symphesis sits
at exactly half the inner vestibular distance wait half, yes,
half the distance from the deepest part of the upper
vestibule to the deepest part of the lower vestibule.
Speaker 1 (10:25):
So by measuring that total distance from the top fornix
to the bottom fornix and simply cutting that number in half.
We aren't just guessing where the occlusal plane should be.
We're actually forcing the patient's own anatomy to.
Speaker 2 (10:38):
Tell us precisely. You adjust the measuring tin on the
front of the centric tray to that exact halved measurement.
Then you mount the lower cast and average value using
a horizontal guide or a rubber band around the articulator.
Speaker 1 (10:53):
Now you have to help us translate some of the
heavier jargon here, because the text mentions setting the bulkwall
angle to twenty two point five degrees and using a
bondwell triangle of one hundred and eight millimeters. Right.
Speaker 2 (11:04):
That sounds intimidating, But let's break that down visually. The
bondwell triangle is essentially a geometric tripod inside the skull. Okay,
imagine drawing a triangle from the two temporo mandibular joints
down to the point between the lower central incisors. On
an average human, each side of that triangle is one
hundred and eight minimeters.
Speaker 1 (11:22):
So it standardizes the size of the jaw. Yeah, and
the bulk willl.
Speaker 2 (11:25):
Angle that is, the downward tilt of the jaw. It's
the angle between that bondwell triangle we just drew and
the occlusal plane, which averages twenty two point five degrees.
Speaker 1 (11:32):
Oh okay.
Speaker 2 (11:33):
By aligning the lower cast to a rubber band set
at these standard metrics, you basically translate a highly resorbed
ambiguous mouth into a mathematically functional space in the lab.
Speaker 1 (11:43):
So we have our foundational math. Now we need to
fabricate the custom trays to get our final perfect seal.
The lab preparation here is pretty meticulous.
Speaker 2 (11:54):
Very meticulous. The technician uses wax as a spacer to
block out resilient areas like the rugae so the tray
doesn't compress them.
Speaker 1 (12:02):
Right, and they map out the frenums, the deflection points,
the mila hyde ridges, oh and even the samaya sinew
strings if the patient.
Speaker 2 (12:09):
Has them exactly. Then they fabricate the base plates using
half the normal amount of a self curing acrylic like ivolin,
keeping it thin but rigid, thin but rigid, finishing it
with a bite rim and painting it with adhesive. But
the real clinical magic happens during the functional impression.
Speaker 1 (12:26):
Let's talk about achieving that complete seal for the upper denture.
The text prescribes a very specific maneuver at the back
of the palate.
Speaker 2 (12:32):
Yes, to seal the upper completely, the clinician applies a
three milimeter strip of high consistency impression material straight across
the vibrating line between the hamular areas.
Speaker 1 (12:42):
Why use a thick high consistency material there instead of something.
Speaker 2 (12:46):
Flowable because you need mechanical force. That thick material physically
raises the soft pallet tissue. Oh I see, its high
viscosity pushes against the vibrating line, creating a tight close
contact seal that it prevents air from breaking the section
when the patient speaks or swallows. Makes sense, And to
seal the lower, the lower relies on finding the BTC
(13:08):
point formation that stands for a buckle tongue contact. How
do you find that when you take the lower impression
before you cut away any excess material over the retromolar area,
you look for a curvy island of impression material just
floating there. Yeah, well, this island represents the exact location
where the patient's tongue in cheek physically touch each other.
(13:28):
If your impression captures that contact island, you have successfully
sealed the posterior of the lower denture.
Speaker 1 (13:35):
Now I have to push back a little here. I
know a lot of dentists who absolutely love using extra
light body wash material for all their final impressions because
it flows beautifully into every tiny crevice. But the author
explicitly forbids using extra light body material on standard upper cases.
Why avoid a material that captures such great detail.
Speaker 2 (13:57):
Because capturing detail is totally useless if you don't achieve
tissue compression. Extra light body is extremely runny.
Speaker 1 (14:04):
It just flows away right.
Speaker 2 (14:06):
If you use it on a standard upper palate, it
won't compress the tissue. It will just run down the
patient's throat and trigger their gag reflex.
Speaker 1 (14:14):
Itikes.
Speaker 2 (14:14):
It is a highly specialized tool meant only for highly
resolved lower crests, where it helps pul the saliva together
on the concave surface to prevent voids.
Speaker 1 (14:24):
Oh gotcha.
Speaker 2 (14:25):
And even then, you know you must use a cotton
roll to dry up the excess saliva just seconds before insertion.
Speaker 1 (14:30):
Okay, that makes a lot of sense. The right viscosity
for the right structural goal, saliva is managed, the physical
seal is tight. But all of this is useless if
the upper and lower jaws don't meet correctly exactly. We
are to freeze the bite in centric relation.
Speaker 2 (14:44):
Right and to stabilize the jaw in that perfect reproducible position.
The system uses a Gothic arch tracing device called the nathometer.
Speaker 1 (14:52):
M How does that work?
Speaker 2 (14:54):
The patient goes through functional movements to trace an arrow.
Once you find the exact point of centric relation, you
place a small perforated plexi profile over the tracing and
fix it with a screw.
Speaker 1 (15:07):
So this physically blocks the patient from moving laterally or protrusively.
Speaker 2 (15:12):
Yes, they are locked into the perfect bite. And then
you inject byte registration silicone between the upper and lower
plates to record it. But there is a very specific
warning about the mixing tips used for the silicone. Yeah,
I saw that you must use the wide green injection tips,
not the smaller yellow ones.
Speaker 1 (15:29):
Why does the tip matter so much?
Speaker 2 (15:30):
Because the gap between the upper and lower nethometer plates
is only about four millimeters, However, you cannot just squeeze
a tiny strip of material in there. You must push
the silicone deep, like about twelve millimeters deep in the
vestibular direction.
Speaker 1 (15:44):
Why push it twelve millimeters deep if the vertical gap
is only four milimeters.
Speaker 2 (15:48):
It is entirely for the technicians stability in the lab. Yeah,
in the lab, the technician has to remove those metal
plates and fit the heavy plaster upper and lower models
together using only that piece of silicone.
Speaker 1 (16:00):
Right, and if it's too narrow.
Speaker 2 (16:02):
If you only inject a narrow strip, the heavy models
will just rock back and forth on it. A wide
twelve millimeters deep silicone record creates a massive occlusal fitting surface,
guaranteeing the models mount perfectly.
Speaker 1 (16:14):
The technician will definitely thank you for that, which brings
us to model analysis. The models are mounted, but before
a single artificial tooth is placed, the technician has to
draw a blueprint.
Speaker 2 (16:25):
On the plaster, a critical blueprint.
Speaker 1 (16:27):
So what does this all mean for the final smile?
Speaker 2 (16:29):
It dictates the boundary between function and failure. The technician
projects lines from the retromolar pads, marks the tuberosities, and
projects the axis of the incisive patilla to the front
of the model to find the anatomic midline.
Speaker 1 (16:43):
But the single most critical biomechanical concept in this phase
is the sagital stop.
Speaker 2 (16:48):
Right, Oh, absolutely, the sagital stop, which is.
Speaker 1 (16:50):
The literal end of the chewable ridge section.
Speaker 2 (16:52):
Yes, think about the shape of the lower jaw As
it moves toward the back of the mouth. The bone
curves upward towards the joint.
Speaker 1 (16:59):
Ok maturing it.
Speaker 2 (17:00):
If you place functional chewing teeth on that steep upward incline,
the downward force of chewing hits an angled surface.
Speaker 1 (17:07):
Which creates resultant forward vectors. It acts like a.
Speaker 2 (17:10):
Ski slope, exactly a ski slope, pushing the whole lower
denture forward out of the.
Speaker 1 (17:15):
Mouth, and that sliding motion will instantly injure the mucous membrane.
Speaker 2 (17:18):
It causes terrible sore spots. So you must mathematically determine
where to stop placing teeth. The guide offers two methods.
Speaker 1 (17:26):
Okay.
Speaker 2 (17:27):
The twenty two point five degree rule involves drawing a
line parallel to the occlusal plane, drawing a twenty two
point five degree angle backwards, and seeing where it intersects
the ridge.
Speaker 1 (17:37):
Okay, I have to jump in here. The twenty two
point five degree rules sounds like a lot of protractor math.
Is there a more conservative fail safe approach? Like what
if a patient complains they don't have enough teeth in
the back to chew their food, and you feel pressure
to add another molar.
Speaker 2 (17:51):
If you want the failsafe, you use Professor Gerber's strict rule.
The deepest point of the sagital curvature is the stop period.
Just stop at the bottom of the do not go
past the lowest point of the valley. If you yield
to the patient's pressure and place a tooth behind the
sagital stop, you must follow strict safety rules, which are
that tooth must have a minimum three milimeter gap from
(18:13):
the upper tooth or have no antagonist at all. It
can be there for cheek support, but it absolutely cannot
participate in active chewing.
Speaker 1 (18:22):
That is a vital safety mechanism. Do not put functional
teeth on a.
Speaker 2 (18:25):
Ski slope exactly.
Speaker 1 (18:27):
Finally, we reach the arrangement of the teeth on the
temporary base plates.
Speaker 2 (18:31):
Yes, starting with the upper anteriors. The metrics here are absolute.
The upper central incisors sit seven to nine milimeters forward
from the center of the incisive papilla, and their incisile
edges should be two millimeters longer than half the interervestibular
distance we measured earlier, and.
Speaker 1 (18:47):
They should point to the middle of the lower opposite fornix.
But what about the midline. You said the papilla gives
us the anatomic midline.
Speaker 2 (18:54):
It does, But here is a crucial distinction that clinicians
often miss. The midline for the front teeth must be
the esthetic midline, not just the anatomic one. Well, I
really yes. The clinician evaluates the patient's facial features and
marks the esthetic center. The smile follows the face.
Speaker 1 (19:12):
You know.
Speaker 2 (19:12):
The bone is just the foundation.
Speaker 1 (19:14):
I love that the smile follows the face. And for
the posteriors, the technician uses a two D template, right.
Speaker 2 (19:21):
This template represents Monson's sphere, which curves to match the
speed curve front to back and the Wilson curve side
to side. You position the chewing surfaces of the posterior
teeth to maintain contact with this curved template.
Speaker 1 (19:35):
But if we connect this to the bigger picture of
lab work, there is a trap here with the wax.
Speaker 2 (19:39):
Isn't there a massive trap? Think of a wet kitchen
sponge drying out on your sink. Okay, as it dries
and shrinks, the edges curl up. Dental wax does exactly
the same thing as the hot wax cools around the teeth.
Thermal shrinkage physically pulls the lingual cusps down and away
from the template.
Speaker 1 (19:56):
Oh wow.
Speaker 2 (19:57):
Yeah. The technician has to constantly monitor and correct for themage.
Speaker 1 (20:00):
And the upper and lower posteriors are set in a
one to two relationship with maximal intercusp pation, and to
get the forces directing straight down into the ridge, the
technician often has to grind the basal surfaces like the
necks of the artificial teeth to rotate them perfectly into
the palatal direction.
Speaker 2 (20:17):
It really highlights why this specific system is a masterclass.
I mean, by anchoring every single step to unchanging anatomical
landmarks and applying strict rules for angles and material physics,
you take a highly unpredictable biological environment and make success
completely reproducible.
Speaker 1 (20:34):
It's absolute precision engineering, all right. If you are listening
to this on your commute or steadying in the lab,
it is time for your review question to lock this
in before your next didentialist case. Ask yourself, what are
the two distinct rules for determining the sagital stop on
a lower model and why is it so dangerous to
set functional teeth behind that point?
Speaker 2 (20:53):
And as you think about that ski slope effect, consider
this broader philosophical question, how much of traditional removable prosthetics
relies on fighting against inevitable bone laws. By shifting our
entire technique to anchor on structures like the virtual synthesis
and the retromolar pad landmarks that fundamentally defy bone resorption,
are we essentially time proofing our dentures.
Speaker 1 (21:15):
Wow?
Speaker 2 (21:15):
Think about how prioritizing permanent landmarks over disappearing bone could
change your entire approach to the identialist patient.
Speaker 1 (21:23):
That is a phenomenal thought to end on. Stop chasing
the resorbing bone and start building on the permanent bedrock.
Thank you for joining us on this deep dive. Keep learning,
keep pushing your clinical boundaries, and stay curious. See you
next time.
What if I told you that the secret to a
perfectly stable lower denture has like absolutely nothing to do
with the job bone itself and literally everything to do
with the floor of the mouth.
Speaker 2 (00:11):
I mean it sounds completely counterintuitive, but especially if you
spend your days just staring at severe bone loss on
panoramic X rays. Yeah, exactly, But in the realm of
removable prosthetics, the behavior of the soft tissue really dictates
almost everything about your final success.
Speaker 1 (00:26):
Okay, let's unpack this because that is a massive paradigm shift.
Today we are talking directly to you, whether you're a
dental student grinding through your very first complete denture cases,
a young professional trying to refine your chair side technique,
or just a deeply curious self learner fascinated by the
engineering of the human mouth. We're taking a comprehensive start
(00:48):
to finish masterclass on handling class two removable prosthetics.
Speaker 2 (00:53):
Which is notoriously one of the most challenging classes of
identialist cases. I mean, the requirements for getting a functional
in prision, determining the occlusal plane without natural teeth as guides,
and then arranging the artificial teeth.
Speaker 1 (01:06):
It's a lot.
Speaker 2 (01:07):
It is. It presents incredible hurdles for both the clinician
and the laboratory technician.
Speaker 1 (01:12):
And to conquer those hurdles, we're relying on a highly visual,
incredibly practical source. It's called BPS Step by Step by
Joseph PERTONI. Yes, it details the BPS SEMCD system that
stands for suction effective mandibular Complete Denture, which is a
philosophy pioneered by Professor Giro Abe and developed by.
Speaker 2 (01:33):
Ivaclor right the Abe technique exactly.
Speaker 1 (01:36):
And our mission for this deep dive today is to
extract every critical detail from this workflow, like no skipped steps.
We are breaking down the science from the exact moment
the patient opens their mouth to the final polish of
the teeth.
Speaker 2 (01:49):
And you know the real value of Ratoni's guide is
that it removes the guesswork. It bridges that gap between
what happens in the dental chair and what happens in
the lab, proving that essentially le aesthetics rely entirely on
invisible structural preparation.
Speaker 1 (02:03):
Well, let's dive right into that preparation. Then, before we
even think about mixing a single drop of impression material,
we have to read the terrain of the patient's mouth.
I like to think of this like a surveyor mapping
out a plot of land before laying a foundation, Like
if you miss a hidden sinkle, it really doesn't matter
how beautiful the house is, right, the whole thing just collapses.
Speaker 2 (02:22):
That's a great way to look at it. And the
primary tools for this survey are visualization and critically manual palpation.
You literally have to physically feel the anatomical landmarks.
Speaker 1 (02:36):
So starting on the upper arch, what are we feeling for?
Speaker 2 (02:39):
Well, you start by palpating the tuberosities at the very
back of the ridge. You're actively checking like is this
a solid, bony base or are these flabby, boneless moving tubers.
Speaker 1 (02:50):
Because moving tissue can't support the.
Speaker 2 (02:51):
Load exactly, moving tissue cannot support a vertical load. Then
you also evaluate the zygramatic arch on the side.
Speaker 1 (02:58):
It's just pretty hard and bony.
Speaker 2 (03:00):
Usually, yes, the zygomatic arch is hard. It can actually
provide excellent support for the denture base. However, if that
arch is highly prominent, you must mark it on your
initial assessment.
Speaker 1 (03:09):
Wait, why is that so critical to mark?
Speaker 2 (03:11):
Because you have to communicate that prominence to the technician.
They have to actively avoid it when designing the custom tray.
If the rigid tray hits a prominent zygomatic arch, it
will instantly dislodge the impression and later the denture itself
will just pop right out.
Speaker 1 (03:29):
Oh wow. It's like finding a massive boulder right where
you want to pour your concrete footing exactly.
Speaker 2 (03:34):
You just have to design the architecture around it. And
checking the front of the upper ridge works the same way.
Speaker 1 (03:39):
Right. Figuring out if the anterior ridge is bony or flabby.
Speaker 2 (03:42):
Yeah, because that totally dictates your pressure later. But let's
move down to the lower ridge, which is the notorious
trouble spot for everyone.
Speaker 1 (03:50):
Yeah. Lower dentures are the bane of dental students everywhere, they.
Speaker 2 (03:54):
Really are, but the lower is where the HESEMCD system
really shines. So achieving reliable lower section starts with the
retromolar pads at the back of the mannible. Again, check
if they're bony or movable. Okay, Then you need to
establish the actual width of your foundation. You do this
by finding the distance between the mila hyderidges on the
lingual side the inside right right the inside, and the
(04:17):
linear obliqua externa on the buckle or cheek side.
Speaker 1 (04:21):
Okay, and then the source details this technique called the
sublingual test, which honestly seems to be the absolute make
or break moment for this entire suction philosophy.
Speaker 2 (04:30):
Oh, it is the defining test. So you ask the
patient to raise their tongue to their palate and then
move the tip of their.
Speaker 1 (04:36):
Tongue left and right while you just watch.
Speaker 2 (04:38):
While you are intensely observing the floor of the mouth,
the sublingual.
Speaker 1 (04:42):
Area, and what determines a pass or fail here, what
are we looking for?
Speaker 2 (04:46):
You're watching the tissue dynamics. So if the sublingual tissue
actively follows the movements of the tongue, it indicates a
lack of spongy tissue. It's taut, which means it's hard
to seal, very difficult to seal. But if that sublingual TOI,
she remains completely passive and has this like glandular soft
structure the jackpot, it is a massive advantage that passive
(05:08):
spongy tissue will naturally drape over the borders of the.
Speaker 1 (05:11):
Denture base like a natural gasket.
Speaker 2 (05:13):
Exactly like a gasket, It seals the lower denture against
the floor of the mouth regardless of how the patient
moves their tongue.
Speaker 1 (05:20):
I love that gasket metaphor. You also check the menam area.
Speaker 2 (05:23):
Right the chin, Yeah, by gently pulling the lower lip
to observe the lip seal muscles. And you also check
for macroglossy, which is just an extra wide tongue.
Speaker 1 (05:32):
And that ties directly into Pounds rule, right, it does.
Speaker 2 (05:34):
Pounds rule defines the necessary living space for the tongue
in the lower arch. You must preserve a trapezoid shaped free.
Speaker 1 (05:42):
Area where exactly is this trapezoid.
Speaker 2 (05:44):
It's located between the lingle walls of the lower retromolar
pads at the back, and it narrows toward the measual
contact point of the artificial canines in the front.
Speaker 1 (05:53):
So if you encroach on that space, if.
Speaker 2 (05:55):
You encroach on this trapezoid with thick acrylic or poorly
placed teeth, the tongue feels cramped. It will just constantly
fight to dislodge the denture.
Speaker 1 (06:04):
Okay, so we've mapped our bedrock, found our sinkholes, identified
our natural gaskets. But the mouth isn't a static piece
of stone. It moves, it flexes, it gags. How do
we capture that dynamic environment without distorting the tissues we
just mapped.
Speaker 2 (06:19):
That requires a highly specific preliminary impression technique. For the
upper the author relies on shrine maker's trays, and for
the lower the ideal tool is doctor Jiro Abe's FCB tray.
That's frame cutback tray designed specifically to capture that sublingle
fold we just talked about.
Speaker 1 (06:36):
Oh, if the patient has a really severe gag reflex,
the book mentions falling back on a lower shrine maker's tray.
Speaker 2 (06:42):
Right, Yeah, sometimes you have to adapt. But you don't
just guess the tray size either, Right.
Speaker 1 (06:47):
You take a measuring caliber. You literally measure the exact
distance between the buckle walls of the upper tuberosities and
match that perfectly to the tray.
Speaker 2 (06:55):
With exactly no guessing.
Speaker 1 (06:57):
But the part of this that really caught my eye
is the chemistry of the algenate mix. It's called a
two layer, one phase injected technique.
Speaker 2 (07:04):
What's fascinating here is the deliberate manipulation of setting times.
You use two different types of algenate simultaneously.
Speaker 1 (07:11):
Really at the exact same time.
Speaker 2 (07:13):
Yes, First, the syringe material, this is an injectable long
setting algenate like neocoloid. You mix this and load into
a large thirty five to fifty milli meters central tip syringe. Okay, Meanwhile,
you mix the tray material, which is a regular setting
algenate like hydrocolor five.
Speaker 1 (07:30):
So we are essentially manipulating time here. The syringe material
sets slowly, so you have the freedom to maneuver around
the vestibules, while the tray material sets faster, so the
patient isn't sitting there gagging for ten minutes.
Speaker 2 (07:42):
That is the exact mechanism. It's brilliant, but there is
a massive caveat regarding the powder measurement. The author stresses
in all caps that a cap of algenate must be.
Speaker 1 (07:53):
A flat cap, meaning you can't pack it in.
Speaker 2 (07:56):
It can never be condensed. If you tap the scoop
against the side of the content to pack more powder in,
you fundamentally alter the water to powder ratio.
Speaker 1 (08:04):
Which throws off the dimensional stability of the impression.
Speaker 2 (08:07):
Once it cures, it completely ruins the consistency. So once
it's perfectly mixed, you start with the syringe. You inject
the neo colloid continuously into the upper for nex area.
Speaker 1 (08:18):
You just keep moving.
Speaker 2 (08:19):
Yeah, you must be brave and keep the material flowing
to prevent any air bubbles from forming. And you also
add a tiny peanut sized drop directly onto the incisive
papilla to capture that crucial landmark perfectly.
Speaker 1 (08:32):
And when you finally insert the loaded tray, the source
offers this brilliant biomechanical tip that I loved. You don't
hold the tray by the front handle.
Speaker 2 (08:40):
Yes, when you seat the upper tray, you support the
center of the palatal area with your fingertip.
Speaker 1 (08:46):
Because if you push from the handle, you basically create
a giant lever.
Speaker 2 (08:49):
Right, you end up over pushing the front and lifting
the backup completely, which distorts the impression depth. Center pressure
guarantees an even anatomical distribution.
Speaker 1 (09:00):
Makes perfect sense. And that perfect anatomical model brings us
to the next massive challenge. We have the upper, we
have the lower, but how do they relate to each other?
The jaw moves in three dimensions.
Speaker 2 (09:10):
And without teeth you have no vertical dimension of occlusion.
Speaker 1 (09:14):
Here's where it gets really interesting to me. The source
uses a closed mouth, a clusodynamic impression technique with something
called accentric tray, but the book relies heavily on mathematical
measurements to mount these casts. My question is how does
this rigid math work on a patient whose jawbone has
severely resorbed over decades.
Speaker 2 (09:33):
It works because the BPS system anchors itself to anatomical
landmarks that defy bone resorption. What do you mean, Well,
the alveolar ridge might melt away over the years, but
certain points remain in approximately the exact same functional position.
The first point is this sagital third of the retromolar pads. Okay,
this point sits at the exact same vertical position as
(09:55):
the last molar distal cusps used to no matter how much.
Speaker 1 (09:59):
Bone is lost.
Speaker 2 (10:00):
And the second point the virtual symphesis point. This is
the contact point of the first lower incisors and it
lies directly on the midline over the tuberculum mentalis.
Speaker 1 (10:10):
Okay, so how does that help us with the math?
Speaker 2 (10:12):
The mathematical genius here is that the virtual symphesis sits
at exactly half the inner vestibular distance wait half, yes,
half the distance from the deepest part of the upper
vestibule to the deepest part of the lower vestibule.
Speaker 1 (10:25):
So by measuring that total distance from the top fornix
to the bottom fornix and simply cutting that number in half.
We aren't just guessing where the occlusal plane should be.
We're actually forcing the patient's own anatomy to.
Speaker 2 (10:38):
Tell us precisely. You adjust the measuring tin on the
front of the centric tray to that exact halved measurement.
Then you mount the lower cast and average value using
a horizontal guide or a rubber band around the articulator.
Speaker 1 (10:53):
Now you have to help us translate some of the
heavier jargon here, because the text mentions setting the bulkwall
angle to twenty two point five degrees and using a
bondwell triangle of one hundred and eight millimeters. Right.
Speaker 2 (11:04):
That sounds intimidating, But let's break that down visually. The
bondwell triangle is essentially a geometric tripod inside the skull. Okay,
imagine drawing a triangle from the two temporo mandibular joints
down to the point between the lower central incisors. On
an average human, each side of that triangle is one
hundred and eight minimeters.
Speaker 1 (11:22):
So it standardizes the size of the jaw. Yeah, and
the bulk willl.
Speaker 2 (11:25):
Angle that is, the downward tilt of the jaw. It's
the angle between that bondwell triangle we just drew and
the occlusal plane, which averages twenty two point five degrees.
Speaker 1 (11:32):
Oh okay.
Speaker 2 (11:33):
By aligning the lower cast to a rubber band set
at these standard metrics, you basically translate a highly resorbed
ambiguous mouth into a mathematically functional space in the lab.
Speaker 1 (11:43):
So we have our foundational math. Now we need to
fabricate the custom trays to get our final perfect seal.
The lab preparation here is pretty meticulous.
Speaker 2 (11:54):
Very meticulous. The technician uses wax as a spacer to
block out resilient areas like the rugae so the tray
doesn't compress them.
Speaker 1 (12:02):
Right, and they map out the frenums, the deflection points,
the mila hyde ridges, oh and even the samaya sinew
strings if the patient.
Speaker 2 (12:09):
Has them exactly. Then they fabricate the base plates using
half the normal amount of a self curing acrylic like ivolin,
keeping it thin but rigid, thin but rigid, finishing it
with a bite rim and painting it with adhesive. But
the real clinical magic happens during the functional impression.
Speaker 1 (12:26):
Let's talk about achieving that complete seal for the upper denture.
The text prescribes a very specific maneuver at the back
of the palate.
Speaker 2 (12:32):
Yes, to seal the upper completely, the clinician applies a
three milimeter strip of high consistency impression material straight across
the vibrating line between the hamular areas.
Speaker 1 (12:42):
Why use a thick high consistency material there instead of something.
Speaker 2 (12:46):
Flowable because you need mechanical force. That thick material physically
raises the soft pallet tissue. Oh I see, its high
viscosity pushes against the vibrating line, creating a tight close
contact seal that it prevents air from breaking the section
when the patient speaks or swallows. Makes sense, And to
seal the lower, the lower relies on finding the BTC
(13:08):
point formation that stands for a buckle tongue contact. How
do you find that when you take the lower impression
before you cut away any excess material over the retromolar area,
you look for a curvy island of impression material just
floating there. Yeah, well, this island represents the exact location
where the patient's tongue in cheek physically touch each other.
(13:28):
If your impression captures that contact island, you have successfully
sealed the posterior of the lower denture.
Speaker 1 (13:35):
Now I have to push back a little here. I
know a lot of dentists who absolutely love using extra
light body wash material for all their final impressions because
it flows beautifully into every tiny crevice. But the author
explicitly forbids using extra light body material on standard upper cases.
Why avoid a material that captures such great detail.
Speaker 2 (13:57):
Because capturing detail is totally useless if you don't achieve
tissue compression. Extra light body is extremely runny.
Speaker 1 (14:04):
It just flows away right.
Speaker 2 (14:06):
If you use it on a standard upper palate, it
won't compress the tissue. It will just run down the
patient's throat and trigger their gag reflex.
Speaker 1 (14:14):
Itikes.
Speaker 2 (14:14):
It is a highly specialized tool meant only for highly
resolved lower crests, where it helps pul the saliva together
on the concave surface to prevent voids.
Speaker 1 (14:24):
Oh gotcha.
Speaker 2 (14:25):
And even then, you know you must use a cotton
roll to dry up the excess saliva just seconds before insertion.
Speaker 1 (14:30):
Okay, that makes a lot of sense. The right viscosity
for the right structural goal, saliva is managed, the physical
seal is tight. But all of this is useless if
the upper and lower jaws don't meet correctly exactly. We
are to freeze the bite in centric relation.
Speaker 2 (14:44):
Right and to stabilize the jaw in that perfect reproducible position.
The system uses a Gothic arch tracing device called the nathometer.
Speaker 1 (14:52):
M How does that work?
Speaker 2 (14:54):
The patient goes through functional movements to trace an arrow.
Once you find the exact point of centric relation, you
place a small perforated plexi profile over the tracing and
fix it with a screw.
Speaker 1 (15:07):
So this physically blocks the patient from moving laterally or protrusively.
Speaker 2 (15:12):
Yes, they are locked into the perfect bite. And then
you inject byte registration silicone between the upper and lower
plates to record it. But there is a very specific
warning about the mixing tips used for the silicone. Yeah,
I saw that you must use the wide green injection tips,
not the smaller yellow ones.
Speaker 1 (15:29):
Why does the tip matter so much?
Speaker 2 (15:30):
Because the gap between the upper and lower nethometer plates
is only about four millimeters, However, you cannot just squeeze
a tiny strip of material in there. You must push
the silicone deep, like about twelve millimeters deep in the
vestibular direction.
Speaker 1 (15:44):
Why push it twelve millimeters deep if the vertical gap
is only four milimeters.
Speaker 2 (15:48):
It is entirely for the technicians stability in the lab. Yeah,
in the lab, the technician has to remove those metal
plates and fit the heavy plaster upper and lower models
together using only that piece of silicone.
Speaker 1 (16:00):
Right, and if it's too narrow.
Speaker 2 (16:02):
If you only inject a narrow strip, the heavy models
will just rock back and forth on it. A wide
twelve millimeters deep silicone record creates a massive occlusal fitting surface,
guaranteeing the models mount perfectly.
Speaker 1 (16:14):
The technician will definitely thank you for that, which brings
us to model analysis. The models are mounted, but before
a single artificial tooth is placed, the technician has to
draw a blueprint.
Speaker 2 (16:25):
On the plaster, a critical blueprint.
Speaker 1 (16:27):
So what does this all mean for the final smile?
Speaker 2 (16:29):
It dictates the boundary between function and failure. The technician
projects lines from the retromolar pads, marks the tuberosities, and
projects the axis of the incisive patilla to the front
of the model to find the anatomic midline.
Speaker 1 (16:43):
But the single most critical biomechanical concept in this phase
is the sagital stop.
Speaker 2 (16:48):
Right, Oh, absolutely, the sagital stop, which is.
Speaker 1 (16:50):
The literal end of the chewable ridge section.
Speaker 2 (16:52):
Yes, think about the shape of the lower jaw As
it moves toward the back of the mouth. The bone
curves upward towards the joint.
Speaker 1 (16:59):
Ok maturing it.
Speaker 2 (17:00):
If you place functional chewing teeth on that steep upward incline,
the downward force of chewing hits an angled surface.
Speaker 1 (17:07):
Which creates resultant forward vectors. It acts like a.
Speaker 2 (17:10):
Ski slope, exactly a ski slope, pushing the whole lower
denture forward out of the.
Speaker 1 (17:15):
Mouth, and that sliding motion will instantly injure the mucous membrane.
Speaker 2 (17:18):
It causes terrible sore spots. So you must mathematically determine
where to stop placing teeth. The guide offers two methods.
Speaker 1 (17:26):
Okay.
Speaker 2 (17:27):
The twenty two point five degree rule involves drawing a
line parallel to the occlusal plane, drawing a twenty two
point five degree angle backwards, and seeing where it intersects
the ridge.
Speaker 1 (17:37):
Okay, I have to jump in here. The twenty two
point five degree rules sounds like a lot of protractor math.
Is there a more conservative fail safe approach? Like what
if a patient complains they don't have enough teeth in
the back to chew their food, and you feel pressure
to add another molar.
Speaker 2 (17:51):
If you want the failsafe, you use Professor Gerber's strict rule.
The deepest point of the sagital curvature is the stop period.
Just stop at the bottom of the do not go
past the lowest point of the valley. If you yield
to the patient's pressure and place a tooth behind the
sagital stop, you must follow strict safety rules, which are
that tooth must have a minimum three milimeter gap from
(18:13):
the upper tooth or have no antagonist at all. It
can be there for cheek support, but it absolutely cannot
participate in active chewing.
Speaker 1 (18:22):
That is a vital safety mechanism. Do not put functional
teeth on a.
Speaker 2 (18:25):
Ski slope exactly.
Speaker 1 (18:27):
Finally, we reach the arrangement of the teeth on the
temporary base plates.
Speaker 2 (18:31):
Yes, starting with the upper anteriors. The metrics here are absolute.
The upper central incisors sit seven to nine milimeters forward
from the center of the incisive papilla, and their incisile
edges should be two millimeters longer than half the interervestibular
distance we measured earlier, and.
Speaker 1 (18:47):
They should point to the middle of the lower opposite fornix.
But what about the midline. You said the papilla gives
us the anatomic midline.
Speaker 2 (18:54):
It does, But here is a crucial distinction that clinicians
often miss. The midline for the front teeth must be
the esthetic midline, not just the anatomic one. Well, I
really yes. The clinician evaluates the patient's facial features and
marks the esthetic center. The smile follows the face.
Speaker 1 (19:12):
You know.
Speaker 2 (19:12):
The bone is just the foundation.
Speaker 1 (19:14):
I love that the smile follows the face. And for
the posteriors, the technician uses a two D template, right.
Speaker 2 (19:21):
This template represents Monson's sphere, which curves to match the
speed curve front to back and the Wilson curve side
to side. You position the chewing surfaces of the posterior
teeth to maintain contact with this curved template.
Speaker 1 (19:35):
But if we connect this to the bigger picture of
lab work, there is a trap here with the wax.
Speaker 2 (19:39):
Isn't there a massive trap? Think of a wet kitchen
sponge drying out on your sink. Okay, as it dries
and shrinks, the edges curl up. Dental wax does exactly
the same thing as the hot wax cools around the teeth.
Thermal shrinkage physically pulls the lingual cusps down and away
from the template.
Speaker 1 (19:56):
Oh wow.
Speaker 2 (19:57):
Yeah. The technician has to constantly monitor and correct for themage.
Speaker 1 (20:00):
And the upper and lower posteriors are set in a
one to two relationship with maximal intercusp pation, and to
get the forces directing straight down into the ridge, the
technician often has to grind the basal surfaces like the
necks of the artificial teeth to rotate them perfectly into
the palatal direction.
Speaker 2 (20:17):
It really highlights why this specific system is a masterclass.
I mean, by anchoring every single step to unchanging anatomical
landmarks and applying strict rules for angles and material physics,
you take a highly unpredictable biological environment and make success
completely reproducible.
Speaker 1 (20:34):
It's absolute precision engineering, all right. If you are listening
to this on your commute or steadying in the lab,
it is time for your review question to lock this
in before your next didentialist case. Ask yourself, what are
the two distinct rules for determining the sagital stop on
a lower model and why is it so dangerous to
set functional teeth behind that point?
Speaker 2 (20:53):
And as you think about that ski slope effect, consider
this broader philosophical question, how much of traditional removable prosthetics
relies on fighting against inevitable bone laws. By shifting our
entire technique to anchor on structures like the virtual synthesis
and the retromolar pad landmarks that fundamentally defy bone resorption,
are we essentially time proofing our dentures.
Speaker 1 (21:15):
Wow?
Speaker 2 (21:15):
Think about how prioritizing permanent landmarks over disappearing bone could
change your entire approach to the identialist patient.
Speaker 1 (21:23):
That is a phenomenal thought to end on. Stop chasing
the resorbing bone and start building on the permanent bedrock.
Thank you for joining us on this deep dive. Keep learning,
keep pushing your clinical boundaries, and stay curious. See you
next time.
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