October 13, 2025 • 16 mins
A foundational guide for medical and dental professionals seeking to incorporate 3D Printing (Additive Manufacturing) into their practices. The content covers the basic understanding, history, and wide-ranging applications of 3D printing across various industries, while maintaining a primary focus on the healthcare sector. Key areas discussed include the workflow of medical 3D printing, necessary data acquisition techniques like CT and MRI, essential software for modeling and surgical planning, and the different printing technologies and materials used for creating anatomical models, surgical guides, and implants.
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Episode Transcript
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Speaker 1 (00:00):
Welcome back to the deep Dive. Today, we're taking a
look at something really transformative in healthcare, three D printing. Specifically,
we're focusing on how medical and dental professionals like you
can actually start using it.
Speaker 2 (00:13):
Yeah, we're working from this great guidebook. It's very concise,
definitely not overly technical. The whole idea is to give
you a shortcut really just sort of piece together the
puzzle of implementing three D printing without getting bogged down
and complex engineering details.
Speaker 1 (00:28):
And there's a real sense of purpose behind it. The
authors dedicate it to patients whose tricky cases push them
to tenovate. They mentioned this quote to be trusted as
a greater compliment than being loved. That really speaks to
the commitment driving this, It.
Speaker 2 (00:41):
Really does, and that commitment comes from a solid foundation
of expertise. You've got doctor call who's a maxillofacial surgeon
and researcher, and then doctor Parthisirathi, a pioneer in additive manufacturing,
actually running a big point of care three D printing
setup right now. So you have the clinical side and
the engineering side working together. That means the advice is practical,
focused on getting it implemented successfully for better patient outcomes.
Speaker 1 (01:04):
Okay, brilliant. So let's start right at score one. What
exactly is three D printing when we talk about it
in this context.
Speaker 2 (01:12):
Well, the more precise term is additive manufacturing or AM. Essentially,
it's building an object layer by tiny layer, all from
a digital blueprint a CAD file. For medicine and dentistry.
This is huge because it lets us make things that
are cost effective, perfectly repeatable, and incredibly precise, just what
you need for low volume patient specific items.
Speaker 1 (01:34):
It sounds cutting edge, almost futuristic, but you mentioned it's
actually been around for a bit.
Speaker 2 (01:38):
Yeah. Surprisingly, it's less than forty years old. The initial
concept actually came from Hedeo Cogmen in Japan back in
nineteen eighty. He figured out the layer by layer idea
with photosensitive resin, but famously he couldn't afford the patent fees.
Speaker 1 (01:53):
Oh wow. So who made the big breakthrough though?
Speaker 2 (01:55):
That was Charles Hull in nineteen eighty four. He's often
called the father of three D PS printing. He patent
stereo Lithography SLA and co founded three D Systems. They
launched the first commercial printer, the SLA.
Speaker 1 (02:07):
One, and then things accelerated definitely.
Speaker 2 (02:10):
By nineteen eighty seven, Carl Decarde patented selective laser centering
SLS and Scott Crump patented fused deposition modeling FDM. Those
are still core technologies today. The actual term three D
printing didn't pop up until ninety two thanks to ammanual SAX.
Speaker 1 (02:25):
Interesting history, but for someone looking to implement this understanding,
the approach seems more critical. You mentioned additive versus subtractive exactly.
Speaker 2 (02:33):
This is fundamental. Subtractive manufacturing is the traditional way think
milling or machining. You start with a solid block of material, metal, ceramic, whatever,
and carve weight everything you don't want to get your
final shape.
Speaker 1 (02:44):
Right, Like how dental crowns have often been milled from a.
Speaker 2 (02:46):
Block precisely but subtractive methods. While they need big machines
that waste a lot of material, you need large inventors
of blanks, and crucially, they really struggle with complex shapes.
Try milling something with intricate internal channels or you know,
very organic curves specific to a patient's anatomy. It's tough, sometimes.
Speaker 1 (03:06):
Impossible, okay, So additive comes in to solve that complexity. Issue.
Speaker 2 (03:10):
That's a huge part of it. Additive manufacturing or three
D printing adds material only where it's needed, layer by layer,
so minimum waste, often faster production for complex parts, and
you get complete control over really intricate geometries. Thing designing
a jaw implant with a specific porous structure inside to
help bone grow into it. That's where additive shines.
Speaker 1 (03:30):
But it's not necessarily replacing subtractive entirely.
Speaker 2 (03:34):
Note at all. That's a key takeaway. Neither is inherently better.
We both have their place. You might still use subtractive
for high volume standard parts, but for something like a
custom surgical guy that needs to fit one patient perfectly,
additive is the way to go.
Speaker 1 (03:47):
Okay, let's talk applications. It's used everywhere now, right, Aerospace, cars,
even shoes.
Speaker 2 (03:53):
Oh yeah, it's disrupting tons of sectors. NASA use three
D printed parts on the Perseverance Rover. Car makers use
it for lighter complex parts. Architecture is exploring it for housing,
Adidas has those future craft shoes. It's everywhere, But where
it gets really interesting for us is in healthcare.
Speaker 1 (04:09):
Right, So how did healthcare adopt it? What are the
main uses?
Speaker 2 (04:12):
Healthcare came a bit later to the party, but it's
catching up fast. The applications generally fall into four main
types that professionals really need to grasp. Type I patient
specific anatomical models. These are for visualizing complex anatomy, planning surgery,
even educating patients.
Speaker 1 (04:29):
Okay, like printing a patient's jaw before complex reconstruction exactly.
Speaker 2 (04:33):
Type two are surgical splints. You see these often in
jaw surgery or trauma cases to guide bone segments. Type
three are the patient specific surgical guides or pssgs. These
are templates that guide the surgeon's instruments during the operation,
ensuring incredible accuracy. And Type four are patient specific implants.
These are the actual components left inside the patient, like
(04:54):
a custom cranial plate or hip joint.
Speaker 1 (04:56):
And which medical fields are using this the most.
Speaker 2 (04:59):
Orthopedics leads the way definitely, but dentistry and maxillofacial surgery
are right behind them.
Speaker 1 (05:04):
Why those fields in particular, it's.
Speaker 2 (05:06):
The complexity think about the intricate anatomy of the skull,
the jaw joints. Printing a model of a patient's specific defect,
say after tumor removal, it lets the surgeon, see it,
hold it, plan the cuts, even practice that the surgery beforehand.
On the model, this preoperative planning and rehearsal can dramatically
cut down time in the operating room, sometimes by hours
(05:27):
and less or our time generally means less risk for
the patient and better outcome.
Speaker 1 (05:31):
It's a huge benefit. It really enables that shift towards
personalized medicine, doesn't it, moving away from one size fits all.
Speaker 2 (05:38):
Absolutely, this technology is the key enabler for tailoring treatments
to the individual. But, and this is important. Creating something
like a typewav implant, a custom titanium piece, It's not
just about buying.
Speaker 1 (05:50):
A printer, right, There's got to be more to it
for something that complex and high risk.
Speaker 2 (05:54):
For sure, Implementing this properly, especially for regulated devices, needs
a solid structure. You need to know the terminology, yes,
but critically you need a coordinated team. We're talking surgeons, engineers,
radiologists all working together. They manage the whole process, especially
the critical aspects like controlling the quality of the medical
imaging and validating every.
Speaker 1 (06:15):
Stepkay that team aspect sounds crucial. Let's walk through that workflow. Then.
The book outlines nine steps. Where does it begin.
Speaker 2 (06:22):
It starts with the intake process. This is all about
getting the right information upfront. Quality control starts here. You
need the basics like patient ID, the diagnosis, but also
the specific region of interest or ROI. What exactly are
we printing and what's the end use? Is it for
planning education, a surgical guide, what materials needed flexible, rigid,
(06:42):
and of course when is it needed by Get this
wrong and the whole project can go sideways.
Speaker 1 (06:47):
Makes sense, nail the requirements. First Step two is data acquisition,
getting the images.
Speaker 2 (06:52):
Any volumetric data used for diagnoses can potentially be used
SEET scans, MRI, even ultrasound in some cases, but there
are protocols. Immobilization is absolutely key. If the patient moves
during the scan, you get motion artifacts and the data
is pretty much useless for precise printing. Also removing metal objects, jewelry,
anything that can cause artifacts, and scan the whole ROI.
Speaker 1 (07:14):
In one go, you mentioned CT is common for bone.
Are there specific settings the surgeon should push for?
Speaker 2 (07:19):
Yes, and this is critical for accuracy for skeletal anatomy.
From CT, the slice thickness and increment are vital. If
you get scans with thick slices, say the standard five milimeter.
For some scans, you lose detail. The edges aren't sharp,
the geometry is blurred.
Speaker 1 (07:35):
So thicker slices mean a guide or model won't fit properly.
Speaker 2 (07:38):
Exactly for the kind of high spatial resolution you need.
For an accurate surface model, you need thin slices. The
recommendation is really thin point five millimeters to maybe one
point twenty five millimeter. You also need good image contrast.
The software needs to clearly tell the difference between dense
bone and say soft tissue or a tumor. This relies
on the hounds field units in the scan data.
Speaker 1 (07:59):
Ah okay, So hounds field units are those numbers that
quantify tissue density in the CT image.
Speaker 2 (08:04):
Precisely they allowed the software to differentiate materials. We also
use three D scanning a lot, especially in dental and
maxillofacial work. Things like intraoral scanners capture the surface shape directly,
great from making braces, retainers, that sort of thing. Regardless
of how you get the data, though, it needs to
be in DICOM format for the software. Dit COOM is
like the universal standard for medical images.
Speaker 1 (08:23):
Got it dit com in then software processing. The book
mentions FDA or CE approval for clinical software.
Speaker 2 (08:31):
Yes, that's mandatory if the software is being used to
make diagnostic decisions. You also generally need pretty powerful computers
for this work. The first main software step is segmentation
and thresholding. This is where you use those hounds field
units we talked about. You basically tell the software select
all the pixels within this density range, which corresponds to
bone for example. This isolates the structure you want. Then
(08:53):
you often use techniques like region growing to clean it up,
remove straight pixels or noise, and make sure it's one
continuous structure.
Speaker 1 (08:59):
So you've digitally isolated the bone for instance. What comes next.
Three D biomodeling right.
Speaker 2 (09:05):
This is prepping the segmented data for the printer. It's
like the final digital check. You might trim away anatomy.
You don't need areas outside the main region of interest.
You might also need to add virtual supports or connectors.
Imagine printing a thin piece of skull. It might need
some temporary digital bracing to print successfully. You also have
(09:25):
to handle things like removing overlapping structures. If you're printing
a model with bone and a tumor in different materials.
The software needs perfect boundaries between them, no.
Speaker 1 (09:33):
Overlap, and adding patient IDs securely filling any tiny holes
in the model exactly.
Speaker 2 (09:39):
All these little steps ensure the digital model is robust
and printable. The final output from all this prep work
is the three D mesh file. Usually it's an STL
file Standard Tesselation Language or sometimes AMF. If dot COM
was the stack of raw images, STL is the actual
geometric map the printer follows.
Speaker 1 (09:56):
And that STL file is the foundation for virtual surgical
planning via.
Speaker 2 (10:00):
Yes VSPS where the magic happens. For surgeons, you take
that three D model into planning software. The surgeon can
then digitally perform the surgery, simulate bone cuts, osteotomies, plan
where screws or plates will go, identify potential problems all
on the computer before touching the patient. It's usually collaborative.
The surgeon works with the design engineer iterating the plan
(10:22):
until it's perfect, and that perfect digital plan gets translated
into the real world using those patient specific surgical guides
the pssg's we mentioned, they transfer the plant's accuracy to
ther Okay.
Speaker 1 (10:33):
So plan perfected SDL file ready, Let's talk about the
actual printers and materials. How are printers classified generally.
Speaker 2 (10:41):
By how they work, the type of raw material, the
energy source they use. There are four main families relevant here.
First is material extrusion and the most common type is
FDM fuse deposition modeling. This uses heat to melt a
plastic filment like ABS or PLA and extrudes it layer
by layer. Is usually the most affordable option. Great for
base siccanatonical models you might use for visualization or practice.
(11:03):
Supports are often breakaway or dissolve in water.
Speaker 1 (11:05):
Okay, simple plastic extrusion.
Speaker 2 (11:07):
What's next that polymerization. This includes SLA, serio lithography and
DLP digital light processing. These use UV light to cure
liquid photopolymer resin layer by layer in a vat. They're
known for really high accuracy and smooth surface finish, crucial
if you need find details on a surgical model. SLA
(11:27):
uses a laser beam to trace the layer. DLP projects
the whole layer image at once. The downside parts always
need a secondary UV cure after printing.
Speaker 1 (11:36):
Higher detail, but extra steps.
Speaker 2 (11:38):
Third type material jetting technologies like polyjet fall here. Think
of it like a very sophisticated inkjet printer, but instead
of ink, it jets tiny droplets of photopolymer resin and
it cures them instantly with UV light as they're deposited.
The big advantage here is multi material and multicolor capability.
You can print a part that has rigid sections mimicking
bone right next to flexible sections mimicking soft tissue, all
(11:59):
in one go. So incredibly useful for realistic surgical simulation models.
Speaker 1 (12:03):
Wow, okay, that sounds very advanced. And the last category
powder bed fusion.
Speaker 2 (12:07):
Right, this is where we get into higher strength parts
and metals. These systems use energy a laser or an
electron beam to fuse powder particles together layer by layer. SLS.
Selective laser centering uses a laser to fuse plastic powders,
often things like nylon or PKK. You can get really strong,
durable parts, sometimes even used for non implantable devices. Then
(12:30):
you have metal printing using technologies like EBM, DMLS or SLM.
These use powerful electron beams or lasers to melt fine
metal powders, typically titanium alloys like T six L four
V for medical implants.
Speaker 1 (12:43):
Got it, So the technology choice links directly to the
material and Chapter eleven stresses that material choice depends entirely
on the end use.
Speaker 2 (12:50):
Absolutely, it's driven by the clinical application and the associated risks.
For TYPEI anatomical models, you just need good visualization, so
various photopolymers, boxy resins, thermoplastics work fine. You can choose opaque, transparent, rigid, flexible,
whatever helps the planning.
Speaker 1 (13:03):
But for surgical guides type three it's different. They go
into the operating room exactly.
Speaker 2 (13:08):
They aren't permanent implants, but they contact the patient during surgery,
potentially in the sterile field, so they have strict requirements.
They must be biocompatible, they must be sterilizable, able to
withstand steam, autoclaving or gamma radiation without warping or degrading,
and they need to be durable enough for the surgeon
to handle them without breaking. That's why you see specific
(13:31):
materials like medical grade resins designed for surgical guides, or
sometimes polyamide nylons.
Speaker 1 (13:36):
Okay, strict rules for guides, and for type four the actual.
Speaker 2 (13:39):
Implants even stricter. These are permanent devices. The raw materials
themselves are highly regulated, things like titanium alloys, especially TY
six L four V, certain high performance polymers like peak
or ceramics. And the amazing thing with three D printing
here is engineering within the implant. You can design lattice structures,
specific porosities impossible with traditional methods, to encourage bone integration,
(14:02):
or fine tune the implant's stitches to match the patient's bone.
Speaker 1 (14:05):
Incredible potential there. So the part comes off the printer.
Is it done?
Speaker 2 (14:09):
Oh? Definitely not. Post processing is always required. It's a
crucial step to get the final usable part. The first
thing is always removing support structures. How you do that
depends heavily on the technology. FDM supports might just snap off.
Soluble supports dissolve polyjets. Jelly like supports often need a
high pressure water jet or sometimes a chemical bath. Metal
(14:32):
printing supports usually need to be carefully cut or machined off.
Speaker 1 (14:35):
So support removal is step one.
Speaker 2 (14:37):
What else you might need? Gluing if the part was
too big to print in one piece. Sanding is almost
always done to get a smooth surface finish, sometimes going
up to very fine grits, and then there might be
finishing steps like painting for models for special coatings for
medical devices. Every single post processing step has to be
carefully controlled and validated.
Speaker 1 (14:55):
Okay, so wrapping this up, we've gone from the patient
scan the DICOM data, through segment and modeling to get
an SDL file, chosen a technology and material, printed it,
and then post processed it. What's the big picture takeaway?
Speaker 2 (15:07):
The big picture is that three D printing isn't just
a novelty. It's becoming a fundamental tool for delivering personalized healthcare.
It's part of that whole industry four point zero shift.
By understanding this whole workflow, from knowing why you need
thin ct slices to understanding which materials can be sterilized,
you as the clinician can make informed choices, choices that
(15:28):
ultimately improve patient safety, boot surgical accuracy, and help move
your practice towards truly customize better outcomes. But you have
to engage with it, adapt.
Speaker 1 (15:37):
To it, and as the author's stress, doing this at
a high level, especially in a hospital setting, really needs
that integrated team the surgeon, engineer, radiologists working together seamlessly
in what they call a point of care three D
printing center exactly.
Speaker 2 (15:51):
Which actually leads perfectly into a final thought, a sort
of review exercise for you. Our listeners to really cement this.
Speaker 1 (15:57):
Okay, let's hear it all right.
Speaker 2 (15:59):
So think back to the diferences we discussed between additive
and subtractive manufacturing early on in chapter one, and remember
the specific purpose of a patient's specific surgical guide a PSSG,
which is a type three device as detailed in chapter eleven.
Now explain why added a manufacturing three D printing is
so uniquely suited for making these pssgs compared to trying
to make them with traditional subtractive methods like milling. Your
(16:20):
answer should really touch on customization, the ability to create
those complex, intricate shapes that perfectly match an individual patient's anatomy,
and why that precise, often friction based fit is so
critical for surgical accuracy.
Welcome back to the deep Dive. Today, we're taking a
look at something really transformative in healthcare, three D printing. Specifically,
we're focusing on how medical and dental professionals like you
can actually start using it.
Speaker 2 (00:13):
Yeah, we're working from this great guidebook. It's very concise,
definitely not overly technical. The whole idea is to give
you a shortcut really just sort of piece together the
puzzle of implementing three D printing without getting bogged down
and complex engineering details.
Speaker 1 (00:28):
And there's a real sense of purpose behind it. The
authors dedicate it to patients whose tricky cases push them
to tenovate. They mentioned this quote to be trusted as
a greater compliment than being loved. That really speaks to
the commitment driving this, It.
Speaker 2 (00:41):
Really does, and that commitment comes from a solid foundation
of expertise. You've got doctor call who's a maxillofacial surgeon
and researcher, and then doctor Parthisirathi, a pioneer in additive manufacturing,
actually running a big point of care three D printing
setup right now. So you have the clinical side and
the engineering side working together. That means the advice is practical,
focused on getting it implemented successfully for better patient outcomes.
Speaker 1 (01:04):
Okay, brilliant. So let's start right at score one. What
exactly is three D printing when we talk about it
in this context.
Speaker 2 (01:12):
Well, the more precise term is additive manufacturing or AM. Essentially,
it's building an object layer by tiny layer, all from
a digital blueprint a CAD file. For medicine and dentistry.
This is huge because it lets us make things that
are cost effective, perfectly repeatable, and incredibly precise, just what
you need for low volume patient specific items.
Speaker 1 (01:34):
It sounds cutting edge, almost futuristic, but you mentioned it's
actually been around for a bit.
Speaker 2 (01:38):
Yeah. Surprisingly, it's less than forty years old. The initial
concept actually came from Hedeo Cogmen in Japan back in
nineteen eighty. He figured out the layer by layer idea
with photosensitive resin, but famously he couldn't afford the patent fees.
Speaker 1 (01:53):
Oh wow. So who made the big breakthrough though?
Speaker 2 (01:55):
That was Charles Hull in nineteen eighty four. He's often
called the father of three D PS printing. He patent
stereo Lithography SLA and co founded three D Systems. They
launched the first commercial printer, the SLA.
Speaker 1 (02:07):
One, and then things accelerated definitely.
Speaker 2 (02:10):
By nineteen eighty seven, Carl Decarde patented selective laser centering
SLS and Scott Crump patented fused deposition modeling FDM. Those
are still core technologies today. The actual term three D
printing didn't pop up until ninety two thanks to ammanual SAX.
Speaker 1 (02:25):
Interesting history, but for someone looking to implement this understanding,
the approach seems more critical. You mentioned additive versus subtractive exactly.
Speaker 2 (02:33):
This is fundamental. Subtractive manufacturing is the traditional way think
milling or machining. You start with a solid block of material, metal, ceramic, whatever,
and carve weight everything you don't want to get your
final shape.
Speaker 1 (02:44):
Right, Like how dental crowns have often been milled from a.
Speaker 2 (02:46):
Block precisely but subtractive methods. While they need big machines
that waste a lot of material, you need large inventors
of blanks, and crucially, they really struggle with complex shapes.
Try milling something with intricate internal channels or you know,
very organic curves specific to a patient's anatomy. It's tough, sometimes.
Speaker 1 (03:06):
Impossible, okay, So additive comes in to solve that complexity. Issue.
Speaker 2 (03:10):
That's a huge part of it. Additive manufacturing or three
D printing adds material only where it's needed, layer by layer,
so minimum waste, often faster production for complex parts, and
you get complete control over really intricate geometries. Thing designing
a jaw implant with a specific porous structure inside to
help bone grow into it. That's where additive shines.
Speaker 1 (03:30):
But it's not necessarily replacing subtractive entirely.
Speaker 2 (03:34):
Note at all. That's a key takeaway. Neither is inherently better.
We both have their place. You might still use subtractive
for high volume standard parts, but for something like a
custom surgical guy that needs to fit one patient perfectly,
additive is the way to go.
Speaker 1 (03:47):
Okay, let's talk applications. It's used everywhere now, right, Aerospace, cars,
even shoes.
Speaker 2 (03:53):
Oh yeah, it's disrupting tons of sectors. NASA use three
D printed parts on the Perseverance Rover. Car makers use
it for lighter complex parts. Architecture is exploring it for housing,
Adidas has those future craft shoes. It's everywhere, But where
it gets really interesting for us is in healthcare.
Speaker 1 (04:09):
Right, So how did healthcare adopt it? What are the
main uses?
Speaker 2 (04:12):
Healthcare came a bit later to the party, but it's
catching up fast. The applications generally fall into four main
types that professionals really need to grasp. Type I patient
specific anatomical models. These are for visualizing complex anatomy, planning surgery,
even educating patients.
Speaker 1 (04:29):
Okay, like printing a patient's jaw before complex reconstruction exactly.
Speaker 2 (04:33):
Type two are surgical splints. You see these often in
jaw surgery or trauma cases to guide bone segments. Type
three are the patient specific surgical guides or pssgs. These
are templates that guide the surgeon's instruments during the operation,
ensuring incredible accuracy. And Type four are patient specific implants.
These are the actual components left inside the patient, like
(04:54):
a custom cranial plate or hip joint.
Speaker 1 (04:56):
And which medical fields are using this the most.
Speaker 2 (04:59):
Orthopedics leads the way definitely, but dentistry and maxillofacial surgery
are right behind them.
Speaker 1 (05:04):
Why those fields in particular, it's.
Speaker 2 (05:06):
The complexity think about the intricate anatomy of the skull,
the jaw joints. Printing a model of a patient's specific defect,
say after tumor removal, it lets the surgeon, see it,
hold it, plan the cuts, even practice that the surgery beforehand.
On the model, this preoperative planning and rehearsal can dramatically
cut down time in the operating room, sometimes by hours
(05:27):
and less or our time generally means less risk for
the patient and better outcome.
Speaker 1 (05:31):
It's a huge benefit. It really enables that shift towards
personalized medicine, doesn't it, moving away from one size fits all.
Speaker 2 (05:38):
Absolutely, this technology is the key enabler for tailoring treatments
to the individual. But, and this is important. Creating something
like a typewav implant, a custom titanium piece, It's not
just about buying.
Speaker 1 (05:50):
A printer, right, There's got to be more to it
for something that complex and high risk.
Speaker 2 (05:54):
For sure, Implementing this properly, especially for regulated devices, needs
a solid structure. You need to know the terminology, yes,
but critically you need a coordinated team. We're talking surgeons, engineers,
radiologists all working together. They manage the whole process, especially
the critical aspects like controlling the quality of the medical
imaging and validating every.
Speaker 1 (06:15):
Stepkay that team aspect sounds crucial. Let's walk through that workflow. Then.
The book outlines nine steps. Where does it begin.
Speaker 2 (06:22):
It starts with the intake process. This is all about
getting the right information upfront. Quality control starts here. You
need the basics like patient ID, the diagnosis, but also
the specific region of interest or ROI. What exactly are
we printing and what's the end use? Is it for
planning education, a surgical guide, what materials needed flexible, rigid,
(06:42):
and of course when is it needed by Get this
wrong and the whole project can go sideways.
Speaker 1 (06:47):
Makes sense, nail the requirements. First Step two is data acquisition,
getting the images.
Speaker 2 (06:52):
Any volumetric data used for diagnoses can potentially be used
SEET scans, MRI, even ultrasound in some cases, but there
are protocols. Immobilization is absolutely key. If the patient moves
during the scan, you get motion artifacts and the data
is pretty much useless for precise printing. Also removing metal objects, jewelry,
anything that can cause artifacts, and scan the whole ROI.
Speaker 1 (07:14):
In one go, you mentioned CT is common for bone.
Are there specific settings the surgeon should push for?
Speaker 2 (07:19):
Yes, and this is critical for accuracy for skeletal anatomy.
From CT, the slice thickness and increment are vital. If
you get scans with thick slices, say the standard five milimeter.
For some scans, you lose detail. The edges aren't sharp,
the geometry is blurred.
Speaker 1 (07:35):
So thicker slices mean a guide or model won't fit properly.
Speaker 2 (07:38):
Exactly for the kind of high spatial resolution you need.
For an accurate surface model, you need thin slices. The
recommendation is really thin point five millimeters to maybe one
point twenty five millimeter. You also need good image contrast.
The software needs to clearly tell the difference between dense
bone and say soft tissue or a tumor. This relies
on the hounds field units in the scan data.
Speaker 1 (07:59):
Ah okay, So hounds field units are those numbers that
quantify tissue density in the CT image.
Speaker 2 (08:04):
Precisely they allowed the software to differentiate materials. We also
use three D scanning a lot, especially in dental and
maxillofacial work. Things like intraoral scanners capture the surface shape directly,
great from making braces, retainers, that sort of thing. Regardless
of how you get the data, though, it needs to
be in DICOM format for the software. Dit COOM is
like the universal standard for medical images.
Speaker 1 (08:23):
Got it dit com in then software processing. The book
mentions FDA or CE approval for clinical software.
Speaker 2 (08:31):
Yes, that's mandatory if the software is being used to
make diagnostic decisions. You also generally need pretty powerful computers
for this work. The first main software step is segmentation
and thresholding. This is where you use those hounds field
units we talked about. You basically tell the software select
all the pixels within this density range, which corresponds to
bone for example. This isolates the structure you want. Then
(08:53):
you often use techniques like region growing to clean it up,
remove straight pixels or noise, and make sure it's one
continuous structure.
Speaker 1 (08:59):
So you've digitally isolated the bone for instance. What comes next.
Three D biomodeling right.
Speaker 2 (09:05):
This is prepping the segmented data for the printer. It's
like the final digital check. You might trim away anatomy.
You don't need areas outside the main region of interest.
You might also need to add virtual supports or connectors.
Imagine printing a thin piece of skull. It might need
some temporary digital bracing to print successfully. You also have
(09:25):
to handle things like removing overlapping structures. If you're printing
a model with bone and a tumor in different materials.
The software needs perfect boundaries between them, no.
Speaker 1 (09:33):
Overlap, and adding patient IDs securely filling any tiny holes
in the model exactly.
Speaker 2 (09:39):
All these little steps ensure the digital model is robust
and printable. The final output from all this prep work
is the three D mesh file. Usually it's an STL
file Standard Tesselation Language or sometimes AMF. If dot COM
was the stack of raw images, STL is the actual
geometric map the printer follows.
Speaker 1 (09:56):
And that STL file is the foundation for virtual surgical
planning via.
Speaker 2 (10:00):
Yes VSPS where the magic happens. For surgeons, you take
that three D model into planning software. The surgeon can
then digitally perform the surgery, simulate bone cuts, osteotomies, plan
where screws or plates will go, identify potential problems all
on the computer before touching the patient. It's usually collaborative.
The surgeon works with the design engineer iterating the plan
(10:22):
until it's perfect, and that perfect digital plan gets translated
into the real world using those patient specific surgical guides
the pssg's we mentioned, they transfer the plant's accuracy to
ther Okay.
Speaker 1 (10:33):
So plan perfected SDL file ready, Let's talk about the
actual printers and materials. How are printers classified generally.
Speaker 2 (10:41):
By how they work, the type of raw material, the
energy source they use. There are four main families relevant here.
First is material extrusion and the most common type is
FDM fuse deposition modeling. This uses heat to melt a
plastic filment like ABS or PLA and extrudes it layer
by layer. Is usually the most affordable option. Great for
base siccanatonical models you might use for visualization or practice.
(11:03):
Supports are often breakaway or dissolve in water.
Speaker 1 (11:05):
Okay, simple plastic extrusion.
Speaker 2 (11:07):
What's next that polymerization. This includes SLA, serio lithography and
DLP digital light processing. These use UV light to cure
liquid photopolymer resin layer by layer in a vat. They're
known for really high accuracy and smooth surface finish, crucial
if you need find details on a surgical model. SLA
(11:27):
uses a laser beam to trace the layer. DLP projects
the whole layer image at once. The downside parts always
need a secondary UV cure after printing.
Speaker 1 (11:36):
Higher detail, but extra steps.
Speaker 2 (11:38):
Third type material jetting technologies like polyjet fall here. Think
of it like a very sophisticated inkjet printer, but instead
of ink, it jets tiny droplets of photopolymer resin and
it cures them instantly with UV light as they're deposited.
The big advantage here is multi material and multicolor capability.
You can print a part that has rigid sections mimicking
bone right next to flexible sections mimicking soft tissue, all
(11:59):
in one go. So incredibly useful for realistic surgical simulation models.
Speaker 1 (12:03):
Wow, okay, that sounds very advanced. And the last category
powder bed fusion.
Speaker 2 (12:07):
Right, this is where we get into higher strength parts
and metals. These systems use energy a laser or an
electron beam to fuse powder particles together layer by layer. SLS.
Selective laser centering uses a laser to fuse plastic powders,
often things like nylon or PKK. You can get really strong,
durable parts, sometimes even used for non implantable devices. Then
(12:30):
you have metal printing using technologies like EBM, DMLS or SLM.
These use powerful electron beams or lasers to melt fine
metal powders, typically titanium alloys like T six L four
V for medical implants.
Speaker 1 (12:43):
Got it, So the technology choice links directly to the
material and Chapter eleven stresses that material choice depends entirely
on the end use.
Speaker 2 (12:50):
Absolutely, it's driven by the clinical application and the associated risks.
For TYPEI anatomical models, you just need good visualization, so
various photopolymers, boxy resins, thermoplastics work fine. You can choose opaque, transparent, rigid, flexible,
whatever helps the planning.
Speaker 1 (13:03):
But for surgical guides type three it's different. They go
into the operating room exactly.
Speaker 2 (13:08):
They aren't permanent implants, but they contact the patient during surgery,
potentially in the sterile field, so they have strict requirements.
They must be biocompatible, they must be sterilizable, able to
withstand steam, autoclaving or gamma radiation without warping or degrading,
and they need to be durable enough for the surgeon
to handle them without breaking. That's why you see specific
(13:31):
materials like medical grade resins designed for surgical guides, or
sometimes polyamide nylons.
Speaker 1 (13:36):
Okay, strict rules for guides, and for type four the actual.
Speaker 2 (13:39):
Implants even stricter. These are permanent devices. The raw materials
themselves are highly regulated, things like titanium alloys, especially TY
six L four V, certain high performance polymers like peak
or ceramics. And the amazing thing with three D printing
here is engineering within the implant. You can design lattice structures,
specific porosities impossible with traditional methods, to encourage bone integration,
(14:02):
or fine tune the implant's stitches to match the patient's bone.
Speaker 1 (14:05):
Incredible potential there. So the part comes off the printer.
Is it done?
Speaker 2 (14:09):
Oh? Definitely not. Post processing is always required. It's a
crucial step to get the final usable part. The first
thing is always removing support structures. How you do that
depends heavily on the technology. FDM supports might just snap off.
Soluble supports dissolve polyjets. Jelly like supports often need a
high pressure water jet or sometimes a chemical bath. Metal
(14:32):
printing supports usually need to be carefully cut or machined off.
Speaker 1 (14:35):
So support removal is step one.
Speaker 2 (14:37):
What else you might need? Gluing if the part was
too big to print in one piece. Sanding is almost
always done to get a smooth surface finish, sometimes going
up to very fine grits, and then there might be
finishing steps like painting for models for special coatings for
medical devices. Every single post processing step has to be
carefully controlled and validated.
Speaker 1 (14:55):
Okay, so wrapping this up, we've gone from the patient
scan the DICOM data, through segment and modeling to get
an SDL file, chosen a technology and material, printed it,
and then post processed it. What's the big picture takeaway?
Speaker 2 (15:07):
The big picture is that three D printing isn't just
a novelty. It's becoming a fundamental tool for delivering personalized healthcare.
It's part of that whole industry four point zero shift.
By understanding this whole workflow, from knowing why you need
thin ct slices to understanding which materials can be sterilized,
you as the clinician can make informed choices, choices that
(15:28):
ultimately improve patient safety, boot surgical accuracy, and help move
your practice towards truly customize better outcomes. But you have
to engage with it, adapt.
Speaker 1 (15:37):
To it, and as the author's stress, doing this at
a high level, especially in a hospital setting, really needs
that integrated team the surgeon, engineer, radiologists working together seamlessly
in what they call a point of care three D
printing center exactly.
Speaker 2 (15:51):
Which actually leads perfectly into a final thought, a sort
of review exercise for you. Our listeners to really cement this.
Speaker 1 (15:57):
Okay, let's hear it all right.
Speaker 2 (15:59):
So think back to the diferences we discussed between additive
and subtractive manufacturing early on in chapter one, and remember
the specific purpose of a patient's specific surgical guide a PSSG,
which is a type three device as detailed in chapter eleven.
Now explain why added a manufacturing three D printing is
so uniquely suited for making these pssgs compared to trying
to make them with traditional subtractive methods like milling. Your
(16:20):
answer should really touch on customization, the ability to create
those complex, intricate shapes that perfectly match an individual patient's anatomy,
and why that precise, often friction based fit is so
critical for surgical accuracy.
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