Speaker 1: You know, usually when we talk about a dental treatment,
Speaker 1: there is this underlying expectation of precision. It feels well,
Speaker 1: almost like engineering.
Speaker 2: Right, Yeah, like building a bridge or something exactly.
Speaker 1: You prip a tooth for a crown, you take a
Speaker 1: digital scan, the lab makes the ceramic and it fits
Speaker 1: onto this totally solid static foundation. It's measurable.
Speaker 2: It is. I mean, you're generally working with hard, unyielding
Speaker 2: tissues enamel, dentin or maybe implants anchored rigidly in bone.
Speaker 2: The variables are for the most part, highly controlled.
Speaker 1: But then you step into the world of complete dentures
Speaker 1: and suddenly that solid foundation is just completely gone.
Speaker 2: Oh entirely.
Speaker 1: We're looking at a clinical landscape that is entirely dynamic.
Speaker 1: It moves, it yields, it literally changes shape from morning tonight.
Speaker 1: And because of that, I think so many general dental
Speaker 1: practitioners view complete dentures as honestly a bit of a
Speaker 1: black art.
Speaker 2: Yeah, they really do. You're trying to build a static
Speaker 2: prosthesis on a moving target. It is the app sleute
Speaker 2: definition of clinical muddy waters. But it is a rigorous science,
Speaker 2: not a dark art. The biology and the physics dictate everything,
Speaker 2: and once you understand those mechanisms that unpredictability just sort
Speaker 2: of fades away.
Speaker 1: Which is exactly what we are here to map out today.
Speaker 1: So welcome to this deep dive. Whether you are a
Speaker 1: dental student prepping for your final boards, a young professional
Speaker 1: looking to refine your clinical skills, and you know, stop
Speaker 1: fearing a dentalist patience, or just a really curious self
Speaker 1: learner fascinated by oral biomechanics. We are going to demystify
Speaker 1: this entire process today.
Speaker 2: Absolutely.
Speaker 1: We're unpacking Complete Dentures, a clinical manual for the general
Speaker 1: dental practitioner by doctor Hugh Devlin, and our mission today
Speaker 1: is to break down this manual in vivid scientific detail.
Speaker 1: We're going from the very first time you evaluate the
Speaker 1: patient's mouth all away to troubleshooting and home care.
Speaker 2: And I'd argue the urgency of mastering these specific technique
Speaker 2: is actually.
Speaker 1: Climbing really, even with all our modern preventative stuff.
Speaker 2: Yeah, you might look at the incredible advancement in preventative
Speaker 2: dental health and assume that complete dentures are just this
Speaker 2: relic of the past, but the demographics tell a completely
Speaker 2: different story. People are living much much longer, oh right,
Speaker 2: we're seeing a dramatic global increase in centenarians. And because
Speaker 2: of this, the patients who do eventually lose all their teeth, well,
Speaker 2: they're becoming identalists much later in life.
Speaker 1: So the clinical profile of the average denture patient is
Speaker 1: shifting older. What does that actually change for the practitioner
Speaker 1: sitting chair side?
Speaker 2: It changes the entire biological baseline your identialist patients. They
Speaker 2: present with highly complex medical backgrounds, polypharmacy, severe anatomical resorption.
Speaker 2: But the biggest hurdle, honestly is their neuromuscular adaptability.
Speaker 1: Because it's a huge piece of foreign plastic in their mouth.
Speaker 2: Exactly, a sixty year old might have the neurological plasticity
Speaker 2: to intuitively train their tongue in cheeks to hold that
Speaker 2: plastic in place while chewing, But an eighty five year
Speaker 2: old patient, their ability to subconsciously learn those new muscle
Speaker 2: patterns is severely reduced. You can't just hand them a
Speaker 2: generic piece of acrylic and expect their failing adaptability to
Speaker 2: just figure it out. Yeah, you have to actively engineer
Speaker 2: the denture to work in perfect harmony with whatever muscle
Speaker 2: control they have left.
Speaker 1: Wow, Okay, let's start with that initial evaluation then, because
Speaker 1: clearly before you even think about mixing alginate or heating
Speaker 1: up impression compound, you have to understand the biological canvas
Speaker 1: you're building on. We really do so extrarely. We're looking
Speaker 1: at facial symmetry, muscle tone, and interraclusal clearance, which is
Speaker 1: that freeway space between the jaws at rest and then intrallly.
Speaker 1: We are palpating the ridge shape, checking for prominent bony
Speaker 1: toy that will act as full crumbs and rock the denture,
Speaker 1: and of course locating muscle attachments.
Speaker 2: Those muscle attachments are so critical. Take the mentalist muscle
Speaker 2: in the lower anterior mandible for example. Okay, if the
Speaker 2: residual alveolar ridge has resorbed severely, the insertion of that
Speaker 2: mentalis muscle might sit almost at the very crest of
Speaker 2: the remaining bone.
Speaker 1: Oh wow, so right where the denture sits exactly.
Speaker 2: So every single time the patient moves their lower lip,
Speaker 2: that muscle fires and it will physically eject a lower
Speaker 2: denture right out of place.
Speaker 1: Okay, let's unpack this because the manual also red flags
Speaker 1: a massive issue regarding the patient's medical history. It specifically
Speaker 1: highlights anticholinergic drugs, So things like older anahistamines, cyclic antidepressants,
Speaker 1: or overactive bladder medication.
Speaker 2: Yeah, this is a perfect example of a systemic medication
Speaker 2: just destroying a mechanical dental treatment. Anycholinergic drugs block the
Speaker 2: neurotransmitter acetocholine in the nervous.
Speaker 1: System, And how does that specifically sabotage our denture.
Speaker 2: Well, the parasympathetic nervous system relies on acetocullin to stimulate
Speaker 2: the salivary glands, particularly for producing that thin, watery, seedyal saliva.
Speaker 2: When you block those receptors, the glands basically stop pumping.
Speaker 1: Oh, so they get dry mouth.
Speaker 2: Profound zerostomia. And a complete dentro relies entirely on a thin,
Speaker 2: can tinuous film of saliva between the acrylic and the
Speaker 2: ucosa those It creates the capillary attraction and the peripheral seal. Right,
Speaker 2: without that fluid dynamic, the mechanical retention fails completely.
Speaker 1: I always visualize it like trying to stick a rubber
Speaker 1: suction cup to a bone dry window. Yes, I mean,
Speaker 1: you can push as hard as you want and the
Speaker 1: sheet might be a perfect match, But without that microscopic
Speaker 1: layer of moisture to create the fluid seal. It's just
Speaker 1: going to fall right off.
Speaker 2: That is a very accurate visualization. And while we are
Speaker 2: evaluating that soft tissue environment, we also have to assess
Speaker 2: for denture stomatitis. It's incredibly common, actually affecting up to
Speaker 2: sixty five percent of venture wearers in some population.
Speaker 1: That is huge. And the manual breaks this down using
Speaker 1: Newton's three types to categorize the severity, right it does.
Speaker 2: Type I is localized hyperamia, basically pinpoint redness, usually caused
Speaker 2: by a direct mechanical trauma from a high spot on
Speaker 2: the denture.
Speaker 1: Look a blister from a tight share exactly.
Speaker 2: Then Tach two is a generalized aerathema that's a bright
Speaker 2: red swollen area covering the entire denture bearing mucosa. And
Speaker 2: finally Type three is inflammatory peppillary hyperplasia, where the tissue
Speaker 2: actually becomes nodular and bumpy. It often looks like a
Speaker 2: cobblestone street. Yet Ty three frequently requires surgical removal before
Speaker 2: a new denture can even be fabricated.
Speaker 1: Now, when we hear dentrostomatitis, I feel like the immediate
Speaker 1: assumption is a fungal infection, specifically candied ALBICNS. But the
Speaker 1: manual highlights this fascinating paradox about how this yeast actually
Speaker 1: behaves in the mouth. It doesn't behave like a traditional
Speaker 1: tissue infection at all.
Speaker 2: No, it doesn't. Candid ALBUCNS rarely invades the mucosal tissue itself.
Speaker 2: In these cases. If you biopsy that bright red and
Speaker 2: flamed palate, you generally won't see fungal hyphae penetrating into
Speaker 2: the patient's epithelia.
Speaker 1: Wait really, yeah.
Speaker 2: Instead, the yeast is actually thriving inside the microscopic pores
Speaker 2: and undercuts of the acrylic denture itself. The plastic is
Speaker 2: the incubator.
Speaker 1: Wait. Wait, if the fungus is living in highly inside
Speaker 1: the plastic of the denture, why is the patient's mucosal
Speaker 1: tissue turning bright red and inflamed? I mean, is it
Speaker 1: an allergic reaction to the east.
Speaker 2: It's a severe inflammatory response. These colonies metabolize and multiply
Speaker 2: in the acrylic, right, and they pump out metabolic by
Speaker 2: products toxins and enzyme oh. I see, so these toxins
Speaker 2: leech out of the plastic and just bathe the adjacent tissue.
Speaker 2: The patient's mucosa is reacting to this constant toxic chemical
Speaker 2: assault sitting pressed against their palate. The fungal load is
Speaker 2: massively higher on the plastic than on the patient.
Speaker 1: So if a practitioner just prescribes an anti fungal lozenge
Speaker 1: for the patient to suck on and sends them home,
Speaker 1: they are completely missing the target totally.
Speaker 2: They are treating the symptom, not the reservoir. As soon
Speaker 2: as the patient stops the lozenges, the toxins from the
Speaker 2: denture will just inflame the tissue all over again.
Speaker 1: So what's the fix?
Speaker 2: The clinical protocol here must be twofold. First, you have
Speaker 2: to disinfect the prosthesis. The manual recommends an overnight soak
Speaker 2: in a zero point two percent for hexiting solution or
Speaker 2: a very dilute household bleach.
Speaker 1: Solution, although quick tavia. You have to ensure the denture
Speaker 1: doesn't have a metal framework or a soft silicone liner,
Speaker 1: because bleach would just rapidly degrade those exactly good point.
Speaker 2: And second, you have to correct the physical trauma. Poorly
Speaker 2: fitting dentures rub the tissue, creating an inflammatory, protein.
Speaker 1: Rich exoity, and that exodate is basically a buffet for
Speaker 1: the candida, just feeding the colony exactly. So to stop
Speaker 1: the rubbing, you often have to fix a severely worn
Speaker 1: occlusal scheme. The book provides this brilliant Chercide intervention for this.
Speaker 1: If the posterior plastic teeth have worn completely flat over
Speaker 1: the years, the patient's jaw will basically slide around uncontrollably
Speaker 1: during chewing right.
Speaker 2: Which drags the denture base across.
Speaker 1: The tissue exactly. So you can temporarily fix this by
Speaker 1: adding two to three millimeters of self curing acrylic directly
Speaker 1: to the lower molars to re establish a stable bite.
Speaker 2: But you have to tightly control the vertical dimension of
Speaker 2: the jaw while that new acrylic cures. You can't just
Speaker 2: slap we acrylic on the teeth and tell the patient
Speaker 2: to bite down blindly, because.
Speaker 1: They'll just slide into the wrong position.
Speaker 2: Right, They'll overclose or bite to the side, and then
Speaker 2: you created an even worse problem.
Speaker 1: So the technique is to take warm, moldable impression compound,
Speaker 1: place it just on the canines and second molars, and
Speaker 1: physically guide the patient's jaw to close at the correct
Speaker 1: vertical height. Once that compound cools. It acts as a
Speaker 1: hard physical vertical stop. Then you apply the doughe self
Speaker 1: curing acrylic to the remaining posterior teeth, coat the opposing
Speaker 1: upper teeth and petroleum jelly so they don't accidentally glue together,
Speaker 1: and just guide the patient to bite down until they
Speaker 1: firmly hit those compound stops. It literally stabilizes the moving target.
Speaker 2: It does, and only once that tissue is healthy and stable,
Speaker 2: can you move to the next phase, which is recording
Speaker 2: the anatomical landscape. And this requires a really deep understanding
Speaker 2: of tissue.
Speaker 1: Physics because, like we established, the mouth is not a
Speaker 1: static block of plaster. It yields to press sure and
Speaker 1: if this tissue acts like a fluid under pressure, I
Speaker 1: imagine taking an accurate impression is an absolute nightmare.
Speaker 2: It can be.
Speaker 1: I mean, if you just shove an alginate looted tray
Speaker 1: in there, won't you capture the tissue in a completely distorted,
Speaker 1: compressed state. How do you record a shape that's constantly
Speaker 1: changing based on how hard you push?
Speaker 2: Well, you have to understand that oral mucosa is visco elastic.
Speaker 2: It possesses both fluid and solid properties. When a patient
Speaker 2: bites down, or when you press an impression tray into
Speaker 2: the tissue, there is this immediate elastic displacement. The solid
Speaker 2: components compress right but if you maintain that pressure for
Speaker 2: just a few seconds, you enter a slower phase called creep.
Speaker 1: Creep, like the tissue is slowly flown away from the pressure.
Speaker 2: Exactly, interstitial tissue, fluid and blood are physically being squeezed
Speaker 2: out of the vascular beds and extracellular spaces in that
Speaker 2: specific area. Wow, when you release the load, the tissue
Speaker 2: springs back elastically right away, but that delayed creep recovery
Speaker 2: the fluid slowly seeping back into the area that can
Speaker 2: take hour.
Speaker 1: And to complicate things, the tissue isn't uniform. The muco
Speaker 1: periostium sitting directly on the crest of the bony ridge
Speaker 1: is tightly bound down so it barely yields. But if
Speaker 1: you move back to the posts dam area at the
Speaker 1: junction of the hard and soft palate, you have highly
Speaker 1: compressible submucosa filled with fatty and glandular tissue exactly.
Speaker 2: And because of this chaotic dynamic tissue bed dentistry develop
Speaker 2: different philosophies for taking impressions. Let's look at the extremes first.
Speaker 2: On one end, you have the mucostatic approach okay, eucostatic,
Speaker 2: which means capturing the tissue entirely at rest with zero
Speaker 2: fluid displacement. You use a very runny, low viscosity material
Speaker 2: like a fluid alginate or plaster of Paris, and a
Speaker 2: tray spaced well off the tissues so no pressure, absolutely
Speaker 2: minimal pressure. The resulting denture fits the resting tissues beautifully,
Speaker 2: but the.
Speaker 1: Moment the patient tries to chew a piece of steak,
Speaker 1: the denture rocks because the rigid acrylic hits the hard,
Speaker 1: unyielding bony areas first, while the compressible tissues just give way.
Speaker 2: Correct. So on the other end of the spectrum you
Speaker 2: have the mucocompressive technique. Here you intentionally force the tissue
Speaker 2: into that compressed creep state using a highly viscous material
Speaker 2: like heavy impression.
Speaker 1: Compound, so you're pushing hard.
Speaker 2: You apply significant seating pressure. The resulting denture fits perfectly
Speaker 2: when the patient is biting down with maximum force.
Speaker 1: Wait here's where it gets really interesting. If you process
Speaker 1: a denture to fit the tissues only when they are
Speaker 1: fully compressed and squeezed a fluid. What happens when the
Speaker 1: patient stops chewing and relaxes. Won't that delayed creep recovery happen?
Speaker 2: Oh, you know it.
Speaker 1: The tissues will slowly fill back up with fluid, attempt
Speaker 1: to rebound to their arresting shape, and literally pop the
Speaker 1: denture right off the ridge.
Speaker 2: You've just described the exact mechanical failure of a purely
Speaker 2: mucocompressive technique. The rebounding tissue acts like a slow motion
Speaker 2: ejector seat.
Speaker 1: That is wild.
Speaker 2: Therefore, the clinical gold standard is the selective mucok impressive technique.
Speaker 2: You design a custom impression tray that selectively applies pressure
Speaker 2: to the primary stress bearing areas like the buckle shelf
Speaker 2: in the mandible, which can handle the load while physically
Speaker 2: relieving the tray over the areas that cannot handle pressure,
Speaker 2: like the incisive papilla.
Speaker 1: And nowhere is the selective pressure more critical than when
Speaker 1: dealing with a fibrous or flabby anterior ridge. This happens
Speaker 1: when the underlying bone has resorbed, leaving behind a wobbly
Speaker 1: flap of connective tissue. It's like trying to take a
Speaker 1: precise mold of a wet sponge sitting on top of
Speaker 1: a rock.
Speaker 2: That's a great way to picture it.
Speaker 1: If you press the sponge, it folds over. If you
Speaker 1: process a hard dentsure with that tissue folded over, the
Speaker 1: patient will be an agonizing pain.
Speaker 2: Yeah, And the manual provides an incredibly elegant engineering solution
Speaker 2: to this biological problem. It's called the window tray technique.
Speaker 2: You take a preliminary impression and cast a model. On
Speaker 2: that model, you construct a custom rigid acrylic tray. Okay,
Speaker 2: but before you go to the mouth, you take an
Speaker 2: acrylic burr and physically cut a large window completely out
Speaker 2: of the tray, directly over the exact area of the
Speaker 2: flabby tissue.
Speaker 1: So you have a standard tray, but with a literal
Speaker 1: hole exposing the wobbly bits.
Speaker 2: Yes. First you border mold the edges of the tray
Speaker 2: to capture the muscle attachments. Then you load the intact
Speaker 2: parts of the tray with a medium viscosity material like
Speaker 2: zinc oxide eugenoal paste and set it. You are capturing
Speaker 2: all the firm, healthy tissues under a controlled functional load
Speaker 2: the paste sets. Meanwhile, that flabby tissue is just sitting
Speaker 2: there perfectly at rest, sticking out through the window. You cut.
Speaker 1: Ah, I see where this is going.
Speaker 2: Finally, you take a very thin, watery wash of plaster
Speaker 2: of Paris and you carefully paint it over that exposed
Speaker 2: flabby tissue zero pressure. You capture the firm tissue under
Speaker 2: load and the flabby tissue at absolute resting state, all
Speaker 2: in the exact same impression.
Speaker 1: It's just brilliant. Okay, So we have conquered the visco
Speaker 1: elastic tissue and captured the perfect landscape. Now we need
Speaker 1: to figure out exactly where the upper and lower jaws
Speaker 1: sit in three D space relative to each other, so
Speaker 1: we can position the teeth, which.
Speaker 2: Brings us to the absolute golden rule of complete denture occlusion.
Speaker 2: Drum roll please, the intercustable position, which is the position
Speaker 2: where the artificial upper and lower teeth interlock maximally, it
Speaker 2: must perfectly coincide with a retruated contact.
Speaker 1: Position, the retruited contact position or RCP. That's a joint
Speaker 1: guided position, right. It's when the condoles of the mandible
Speaker 1: are in their most superior, posterior, reproducible position in the
Speaker 1: glenoid fossa.
Speaker 2: Precisely now, In a young patient with natural teeth, their
Speaker 2: habitual chewing bite might actually sit slightly forward of RCP.
Speaker 2: Their brain uses proprioception from the ligaments around their tooth
Speaker 2: throats to guide the jaw into that forward position.
Speaker 1: But in complete dentures there are no tooth roots.
Speaker 2: Right. If you don't build the artificial bite in RCP,
Speaker 2: the dentures will fail. The patient's dentialist jaw will naturally
Speaker 2: seek that stable retruded joint position during swallowing and resting.
Speaker 1: Makes sense.
Speaker 2: If the art official teeth don't interlock perfectly in that
Speaker 2: exact retruited position, the cusps will crash together on their inclines.
Speaker 2: That creates lateral forces that violently dislodge the denture basis.
Speaker 1: So to map out this spatial relationship, we use wax
Speaker 1: rim bite blocks. The manual gives us some hard numbers
Speaker 1: to start shaping these rims. It suggests the upper wax
Speaker 1: room should be about ten millimeters high in the anterior
Speaker 1: maxilla and the lower rim should be about five millimeters
Speaker 1: high in the posterior mandible. We use these rims to
Speaker 1: establish the freeway space the introclusal clearance, which should be
Speaker 1: about two to four millimeters when the patient's jaw muscles
Speaker 1: are totally relaxed. But I have to challenge these static numbers.
Speaker 1: Does a strict ten milimeter anterior height really apply to everyone?
Speaker 1: Good question? I mean, what if you have a patient
Speaker 1: with a severe skeletal discrepancy or a patient whose maxilla
Speaker 1: has suffered extreme bone resorption over forty years? Do these
Speaker 1: textbook averages just go out the window?
Speaker 2: Does a crucial critical distinction. Those numbers are starting points.
Speaker 2: They're not biological laws. They just provide a statistical average
Speaker 2: to give the lab a baseline. But you must radically
Speaker 2: alter them chair side based on facial esthetics and phonetic function.
Speaker 2: For instance, to get the occlusal plane right, use a
Speaker 2: fox byte plane to align the upper wax rim so
Speaker 2: it is perfectly parallel with the interpupillary line, the line
Speaker 2: between the patient's eyes, and also the all ur tragal
Speaker 2: line on the side of the face.
Speaker 1: Right, and you are looking at the horizontal projection two.
Speaker 1: The labial surface of the upper central incisors typically sits
Speaker 1: about eight to ten millimeters anterior to the center of
Speaker 1: the incisive papilla. The manual also dives into the Golden
Speaker 1: ratio of one point six one point eight. When assessing
Speaker 1: the vertical dimension of the face, you are comparing the
Speaker 1: distance from the pupil to the lip commissure against the
Speaker 1: distance from the lip to the bottom of the chin. Exactly,
Speaker 1: if you blindly follow a ten milimeter rule on a
Speaker 1: severely resorbed patient, you might severely overclose their bite.
Speaker 2: Uure has disastrous esthetic consequences. It visually mimics an angles
Speaker 2: class three maleeclusion.
Speaker 1: Right the underbyte look yeah.
Speaker 2: If the bite is too short, the lower jaw hinges
Speaker 2: too far upward and forward, the chin becomes excessively prominent,
Speaker 2: the corners of the mouth turned down, and the lips
Speaker 2: basically collapse inward. It can instantly age a patient's face
Speaker 2: by twenty.
Speaker 1: Years, which proves why determining where to put the teeth
Speaker 1: visually is just so vital. But the manual pushes us
Speaker 1: to go beyond static anatomical landmarks and actually look at
Speaker 1: dynamic muscle forces. The mouth is essentially this narrow corridor
Speaker 1: of competing muscular forces.
Speaker 2: It really is.
Speaker 1: The tongue is constantly pushing outward while the lips and
Speaker 1: the bascinator muscles and the cheeks are constantly pushing inward.
Speaker 2: Right, and if you set the artificial teeth outside of
Speaker 2: the balance point between those forces, the muscles will constantly
Speaker 2: dislodge the denture. This balance point is called the neutral zone,
Speaker 2: and to capture it we use a functional impression technique
Speaker 2: called the piece of gram.
Speaker 1: I absolutely love the mechanics of this technique. Instead of
Speaker 1: guessing where the teeth should go, you let the patient's
Speaker 1: own musculature physically carve out the boundary.
Speaker 2: It's so smart.
Speaker 1: You take a rigid lower base plate and attach these
Speaker 1: little wire loops sticking up from the ridge. Then you
Speaker 1: load those loops with a thick, moldable silicone putty. You
Speaker 1: place it in the patient's mouth and ask them to
Speaker 1: perform normal, exaggerated functions. So they speak, swallow, purse, their lips,
Speaker 1: smile widely.
Speaker 2: And as they perform those ashens, the strong muscles of
Speaker 2: the tongue on the lingle side and the lips and
Speaker 2: cheeks on the buckle side, they forcefully mold that soft
Speaker 2: puddy wow. They compress it and shape it into a
Speaker 2: unique patient specific corridor where the inward and outward muscular
Speaker 2: forces are perfectly neutralized.
Speaker 1: So once that putty sets, you take it out, and
Speaker 1: you have a physical three D model of the denture space.
Speaker 1: You cast a plaster index around it, hand it to
Speaker 1: the lab technician and tell them the artificial teeth must
Speaker 1: fit exactly inside this specific envelope.
Speaker 2: Yes, exactly. If you place a lower just two millimeters
Speaker 2: too far lingually outside that zone, the side of the
Speaker 2: tongue will catch it during speech and constantly lift the denture.
Speaker 1: It completely removes the guesswork. Now, once the lab has
Speaker 1: set the teeth and wax based on our piesagram, we
Speaker 1: reach the final processing phase. To translate that delicate three
Speaker 1: D wax relationship into hardocrylic properly, we have to utilize articulators.
Speaker 2: We do, and the manual strongly advises that whether you
Speaker 2: use a simple average value articulator or a semi adjustable one,
Speaker 2: you really must use a facebo transfer.
Speaker 1: Okay, So, a face bow looks a bit intimidating, like
Speaker 1: a giant metal caliber wrapping around the patient's face, but
Speaker 1: its biomechanical purpose is simple, right. It records the exact
Speaker 1: three D spatial relationship of the patient's upper jaw to
Speaker 1: their temporal mandibular joints. Hinge axis, and then it transfers
Speaker 1: that exact geometry to the hinges of the articulator on
Speaker 1: the lab bench exactly.
Speaker 2: Without a faceco transfer, the radius of the arc of
Speaker 2: closure on the articulator will not match the radius of
Speaker 2: the arc of closure in the patient's actual skull, which
Speaker 2: means the lab might get the teeth to interlock perfectly
Speaker 2: on the metal hinges, but the moment you put the
Speaker 2: denture in the patient's mouth, their jaw closes on a
Speaker 2: slightly different geometric arc and the teeth will crash into
Speaker 2: each other prematurely.
Speaker 1: Right, But let's say you do use a face bow,
Speaker 1: You do a wax try in, and it's perfect. The
Speaker 1: problem is acrylic resin is a plastic. When the lab
Speaker 1: boils it, polymerizes it and cools it, it shrinks, it warps.
Speaker 1: Always tiny microscopic dimensional shifts happen during curing. So how
Speaker 1: do we fix those processing errors before the patient ever
Speaker 1: even sees the denture.
Speaker 2: You anticipate the shrinkage. You use a split cast mounting technique.
Speaker 2: Before the lab processes the denture, they cut indexing notches
Speaker 2: into the base of the plaster cast. Okay, after the
Speaker 2: acrylic is fully cured. They take the unbroken cast, complete
Speaker 2: with the newly processed denture, and they snap it right
Speaker 2: back onto the articulator, using those notches to guarantee its
Speaker 2: original position.
Speaker 1: And then you check the bite again, and inevitably, because
Speaker 1: of the crylic frinkage, a cusp is hitting too hard,
Speaker 1: which brings us to one of the most critical clinical
Speaker 1: and ammonics in dentistry, the bul rule for selective grinding.
Speaker 2: The Boule rule is just essential for achieving balanced articulation
Speaker 2: during lateral excursions. When the patient grinds their jaw to
Speaker 2: the side, you want even gliding contact if you have
Speaker 2: a premature heavy contact on the working side during that slide,
Speaker 2: you don't just take a burr and randomly grind down
Speaker 2: the cusps until it clears.
Speaker 1: Let's picture this biomechanically. Why can't we just grind whatever
Speaker 1: is hitting.
Speaker 2: Because you have to protect the vertical dimension the centric
Speaker 2: holding cusps, which are the palatal cusps of the upper
Speaker 2: teeth and the buckle cusps of the lower teeth. They
Speaker 2: are what physically maintain the patient's vertical bite height when
Speaker 2: they're biting straight down in centric occlusion. Oh, I see
Speaker 2: if you grind away those holding cusps. To fix a
Speaker 2: sideway's sliding interference, you destroy the vertical stops, the whole
Speaker 2: byte collapses and the patient overcloses, So you.
Speaker 1: Only adjust the non holding cusps. During lateral excursion. The
Speaker 1: be Ol rule bet L you grind the buckle cusps
Speaker 1: of the upper teeth and the lingual cusps of the
Speaker 1: lower teeth. By restricting your burr to those specific cusps,
Speaker 1: you eliminate the sideways interference without destroying the vertical stops
Speaker 1: that hold the bite open exactly.
Speaker 2: It preserves the architecture. Now assume we deliver the adjusted
Speaker 2: denture a week later. At the review appointment, the tissue
Speaker 2: looks good, but the patient is having trouble speaking clearly,
Speaker 2: you have to troubleshoot the phonetics based on the specific
Speaker 2: sounds they are struggling with, Like what if they can't
Speaker 2: pronounce T or D sounds cleanly? It is almost always
Speaker 2: an issue with the anterior horizontal placement. The teeth might
Speaker 2: be set too far forward or backward, meaning the tip
Speaker 2: of the tongue is hitting the plastic at the wrong
Speaker 2: point in space during those explosive consonants.
Speaker 1: What if they develop a severe lisp like they are
Speaker 1: struggling with S sounds and it sounds like whistling or slushy. Error.
Speaker 2: That usually points to the palatolocrylic meaning too thick just
Speaker 2: behind the upper central incisors. When you make an S sound,
Speaker 2: your tongue forms a very narrow groove channel down the
Speaker 2: midline to accelerate air. If the acrylic is too bulky
Speaker 2: in that specific spot, it physically obliterates that medial tongue groove.
Speaker 2: The air scatters, causing the list.
Speaker 1: That makes total sense.
Speaker 2: A great clinical trick is to paint a thin layer
Speaker 2: of pressure indicating paste on the pallet. Have the patient
Speaker 2: loudly say Mississippi several times, and then just look at
Speaker 2: the paste. You will see exactly where the tongue is
Speaker 2: wiping away the paste, showing you precisely where you need
Speaker 2: to thin out the acrylic.
Speaker 1: That is incredibly practical. All right, As we wrap up,
Speaker 1: we have to look at patients who simply cannot tolerate
Speaker 1: this entire conventional process. What happens when your patient is
Speaker 1: ninety two years old, physically frail and suffering from dementia.
Speaker 2: Or Parkinson's, it's tough.
Speaker 1: Their neuromuscular system has spent twenty years learning to control
Speaker 1: their current worn out dentures. If you hand them a
Speaker 1: denture with a completely new shape, their brain simply cannot adapt.
Speaker 2: For these patients, you utilize the template or a copy
Speaker 2: denture technique. For a frail patient with reduced adaptability, changing
Speaker 2: the shape of the polished surface the contours their tongue
Speaker 2: and cheeks have memorized is a disastrous You want to
Speaker 2: give them a new fitting surface to improve retention, and
Speaker 2: new sharp teeth to improve chewing, but you must maintain
Speaker 2: the exact same overall volumetric shape they're used to.
Speaker 1: I always compare this to restoring a classic car for
Speaker 1: an elderly driver.
Speaker 2: Oh, I like that.
Speaker 1: If you take their nineteen sixty five Mustang and you
Speaker 1: change the steering ratio, move the pedals two inches to
Speaker 1: the left, and swap the seat for a bucket seat,
Speaker 1: they will crash it. They won't know how to drive it.
Speaker 1: But if you just rebuild the engine and put on
Speaker 1: new tires while keeping the steering wheel in the seat
Speaker 1: exactly where their muscle memory expects them to be, it
Speaker 1: still feels like their car. It just runs better.
Speaker 2: That's a very apt analogy. The protocol here respects that
Speaker 2: muscle memory. You take their old denture and in case,
Speaker 2: the entire thing in laboratory silicone putty in a specialized flat.
Speaker 2: Once it sets, you pull the old denture out, so
Speaker 2: you have a mold exactly. You now have a perfect
Speaker 2: hollow three D mold of their existing denture. You pour
Speaker 2: melted wax into the space where the teeth go, and
Speaker 2: then pour fluid itself carrying acrylic into the space where
Speaker 2: the base goes.
Speaker 1: So you pull out a perfect physical replica wax teeth
Speaker 1: on an acrylic base.
Speaker 2: Yes, you use that replica as your custom impression tray
Speaker 2: to get a new wash of the tissue, and you
Speaker 2: use it as your byte block to record the jaw relationship.
Speaker 2: You send it to the lab and the technician literally
Speaker 2: plucks out the wax teeth one by one, replacing them
Speaker 2: with hard acrylic teeth.
Speaker 1: That's amazing.
Speaker 2: Patient gets a brain new denture, but the spatial footprint
Speaker 2: feels identical to their old one.
Speaker 1: The manual also provides some rapid fire tips for emergency,
Speaker 1: domicillary or at home care. If a denture fractures cleanly
Speaker 1: in two down, the midline. You can carefully superglue it
Speaker 1: together with cyanoacrolate, pour a quick plaster cast inside the
Speaker 1: fitting surface to hold the shape, widen crack with an
Speaker 1: acrylic bur and fill the gap with self curing acrylic
Speaker 1: polymerized in a pressurized hydroflask to eliminate porosity.
Speaker 2: It also mentions a sobering but vital forensic detail regarding
Speaker 2: denture marking. Oh right, If you are inserting an ID
Speaker 2: marker into the acrylic to identify a patient in a
Speaker 2: worst case scenario like a mass casualty incident or a fire,
Speaker 2: paper or allumin tags are completely useless. They will incinerate.
Speaker 1: So what do you use?
Speaker 2: The ID markers must be made of high grade stainless
Speaker 2: deal to survive temperatures exceeding six hundred degrees celsius.
Speaker 1: A stark reminder of the broader medical and forensic role
Speaker 1: dentistry plays in society. Okay, we have covered a massive
Speaker 1: amount of biomechanics from doctor Devlin's manual today. We started
Speaker 1: by understanding that dentrostomatitis is often a mechanical trauma problem
Speaker 1: exacerbated by candida living in the acrylic reservoir, not the tissue.
Speaker 2: We cover a lot.
Speaker 1: Yeah, we explored how the viscoelastic creep of mucosa dictates
Speaker 1: our selective impression techniques, how we capture the neutral zone
Speaker 1: with a piesagram, and how we protect the vertical dimension
Speaker 1: using the bul rule.
Speaker 2: We've demonstrated that fabricating complete dentures is not a black art.
Speaker 2: It requires a rigorous mastery of biologies, spatial mechanics, and
Speaker 2: material science, all carefully tailored to the declining neuromuscular adaptability
Speaker 2: of the aging patient.
Speaker 1: Which brings us to a final provocative thought. As we
Speaker 1: look at modern trends in dentistry, the shortened dental arch
Speaker 1: concept is becoming increasingly popular. Through advanced periodontics and endodontics,
Speaker 1: patients are retaining their front natural teeth much much longer,
Speaker 1: even if they lose all their posterior molars in their fifties, which.
Speaker 2: Raises a critical physiological question for the future. If a
Speaker 2: patient retains just their six lower anterior teeth into their
Speaker 2: late eighties or nineties, and then suddenly loses them all
Speaker 2: at once due to a medical crisis or a rapid decay,
Speaker 2: how will they possibly adapt to a lower complete denture
Speaker 2: They won't be able to Their neuromuscular adaptability will be
Speaker 2: virtually zero at that extreme age, and they won't have
Speaker 2: had the training wheels of waring a partial denture during
Speaker 2: their middle age.
Speaker 1: It makes you wonder if conventional complete dentures will become
Speaker 1: physically impossible for that future generation to tolerate. Will over
Speaker 1: dentures where we deliberately perform root canals and retain the
Speaker 1: roots of those final teeth beneath the acrylic to provide
Speaker 1: bone preservation and physical snapping attention. Will that become the
Speaker 1: absolute mandatory baseline standard of care.
Speaker 2: It is highly likely. It completely changes the long term,
Speaker 2: decades long treatment planning strategy for any general practitioner. You
Speaker 2: have to plan for the patient's neurological decline, not just
Speaker 2: their dental decline.
Speaker 1: All right, before you head into your next clinic session,
Speaker 1: Let's do a quick mental review exercise to cement what
Speaker 1: we've covered today. Visualize the bul rule in action. Imagine
Speaker 1: you have your newly processed dentures mounted on the articulator.
Speaker 1: You slide the upper jaw to the right to simulate
Speaker 1: a working side lateral excursion. You see a premature heavy
Speaker 1: contact on that working side. Based on the biome mechanics,
Speaker 1: we discussed which specific cusps on the upper and lower
Speaker 1: teeth are you going to adjust with your burr to
Speaker 1: clear the interference without collapsing the patient's vertical bite. Map
Speaker 1: the cusps out in your head right now, remember.
Speaker 2: The preservation of the centric holding cusps. You only adjust
Speaker 2: the buckle of the upper and the lingual of the lower.
Speaker 1: Thank you for taking this deep dive into the science
Speaker 1: of complete ventures with us. Keep questioning the mechanics, keep learning,
Speaker 1: and we will see you on the next deep dive.