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Accepted Manuscript

Three-Dimensional Printing in Urology: History, Current Applications,and Future Directions

Niki Parikh MBA, MS, BA , Pranav Sharma MD

PII: S0090-4295(18)30828-8DOI: https://doi.org/10.1016/j.urology.2018.08.004Reference: URL 21190

To appear in: Urology

Received date: 16 June 2018Revised date: 16 June 2018Accepted date: 3 August 2018

Please cite this article as: Niki Parikh MBA, MS, BA , Pranav Sharma MD , Three-DimensionalPrinting in Urology: History, Current Applications, and Future Directions, Urology (2018), doi:https://doi.org/10.1016/j.urology.2018.08.004

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Three-Dimensional Printing in Urology: History, Current Applications, and Future Directions

Niki Parikh, MBA, MS, BA1 and Pranav Sharma, MD1

1Department of Urology, Texas Tech University Health Sciences Center, Lubbock TX

Corresponding author: Pranav Sharma, MD Assistant Professor, Department of Urology Texas Tech Health Sciences Center 3601 4th Street, STOP 7260 Lubbock, TX 79430 Email: [email protected] Phone: (806)-743-1417 Fax: (806)-743-3030 Running (Short) Title: 3D Printing in Urology Conflicts of Interest: None Financial Disclosures: None Funding Sources: None Acknowledgements: None Abstract: To review the history, current applications, limitations, and future directions of three-

dimensional (3D) printing within the field of urology. 3D printing is an additive

manufacturing process in which a 3D model is created using a computer-generated

image. This technology is applied by companies to create and test new drugs, design

and manufacture instrument prototypes, and create patient-specific models of organs

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for surgical teaching and planning. A literature review was performed within the Web of

Science and PubMed databases from January 2008 to May 2018 using keyword

phrases “3D printing” and “urology.” A total of 46 relevant publications were included.

Key Words: three-dimensional; urology; printing; technology

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Introduction:

Three-dimensional (3D) printing (3DP) was invented by Charles Hull in 19861. It

is a form of additive printing in which layer after layer of selected materials are laid to

form a designed object with computer-guided instructions using a specialized device or

printer. The process involves building a solid, 3D object from a digital model using

additive processes in which successive layers of material are assembled on top of one

another to build the desired object. Items for the 3D object are assembled directly from

the digital model, increasing precision and removing room for error. This results in high-

quality, low-cost products that can be created and diffused on a large scale. While

various fields from the automotive industry to the aerospace industry have embraced

this technology, healthcare has been slow to adopt this technology even though an

excess of $155 billion is spent on medical devices yearly. 3DP was initially met with

tremendous enthusiasm in the 1990s with great excitability about its potential uses in

healthcare. The enthusiasm faltered somewhat at the turn of the millennium with

resurgence in recent years.

The potential applications of 3DP in clinical medicine are numerous2. It can allow

physicians to create patient-specific models of pathology with such precise anatomic

detail that it facilitates pre-procedural planning prior to treatments. For example,

patient-specific models of diseased or cancerous organs could be constructed to help

better plan for surgical procedures to improve efficiency, minimize blood loss, and

ultimately translate into better patient outcomes. 3DP can also play a role in the

development of personalized prosthetics for amputees or artificial organs for transplant

candidates as acceptable donor organ numbers continue to dwindle. 3DP can also

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serve as an important teaching tool and training adjunct in medical education not only

for medical students and residents, but also in the counseling of patients and their

families with regards to disease management and procedural description3. Finally, 3DP

can allow for the creation of bioprinted cells for the testing and development of novel

medications or targeted agents to better replicate its potential use and efficacy in actual

patients4. Various medical subspecialties have already extensively studied the

application of 3DP into their clinical practice. Orthopedic surgeons have evaluated its

clinical utility in joint replacement, otolaryngologists have examined its potential use for

implantation in the external ear, cardiologists have looked into its ability to create

implantable artificial heart valves, and trauma surgeons have been able to grow skin

cells using 3DP for grafting and coverage of severe burns and wounds. The field of

urology is just beginning to realize the potential impact of 3DP in pre-surgical planning,

medical education, as well as the creation of personalized prosthetics or other devices

in the treatment of patients5. The following review examines the technology behind

3DP, its current utilization in the field of urology, its limitations, and potential future

applications.

Methods:

A comprehensive literature review was performed within the Web of Science and

PubMed databases from January 2008 to May 2018 using keyword phrases “3D

printing” and “urology.” Initially, 76 relevant peer-reviewed publications were identified

using our search criteria with 64 found within PubMed and 10 found within the Web of

Science. Preferred Reporting Items for Systematic Reviews and Meta-Analyses

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(PRISMA) was used as an evidence-based criterion to select publications for analysis

(Appendix A). After the exclusion of 10 editorial comments or author responses, 8

non-urological publications, and 2 publications with no clinical relevance or patient-

related data, a total of 46 publications were included for review.

Background of 3DP:

Model Design and Creation

The first step in the process of 3DP is designing the prototype or the model.

Data for designs can be collected from various sources of advanced imaging such as

high-definition ultrasound, computed tomography (CT) scan, magnetic resonance

imaging (MRI), or angiography. Using compatible 3DP software, data from two-

dimensional (2D) digital images can be fed into a 3D printer and converted to a 3D

geometric model.

Many 3D printers are currently available for commercial use using different

technologies and materials to create physical objects (Table 1)4. Fused Deposition

Modeling (FDM) is one of the most common printing methods in which a filament is

heated and extruded via a head onto the printer. Liquid plastic is then deposited as per

x and y coordinates onto the building platform in the desired shape. Another method,

called stereolithography (SLA), uses a light-emitting device such as a laser to

selectively illuminate the transparent bottom of a tank filled with a liquid photo-

polymerizing resin. The solidified resin is then progressively dragged up by a lifting

platform to create the desired shape. Finally, laser sintering techniques such as

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electron beam melting (EBM) manufacture parts by melting powdered materials such as

metal layer by layer with an electron beam in a high vacuum.

Software and Hardware Integration

Computer-aided design programs are the source of information and instruction

behind the function of 3DP1. There are multiple file formats utilized with 3DP. The most

commonly used format is the Standard Tessellation Language or Standard Triangle

Language (STL) extension. STL files describe only the surface geometry of a 3D object

without any representation of color or texture. Other file formats include object (OBJ),

which incorporates color and texture, and polygon (PLY), which can store a variety of

properties about scanned models including color, transparency, surface normals,

texture coordinates, and data confidence values.

The main goal of the software is to code surface geometry of 3D objects,

adopting the principles of tessellation1. Tessellation is a process in which different

geometric shapes, usually triangles, are combined without leaving any gaps or overlaps.

These coordinates of vertices and parts of the normal vector of the triangle are stored in

the file formats discussed above as binary codes. The file format extension is then used

with a 3D slicer, an intermediary that allows a computer to communicate with 3D printer

hardware1. The file format must be opened in the slicer, which converts digital 3D

information into instructions for the printer to create the intended object. The slicer

conveys file information, including how much material must be deposited, to the printer

in a bundle called the G-Code, the printer’s language. The G-Code file is transmitted to

the printer, and the 2D image is reassembled into a 3D model on the print bed. With

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successive addition of multiple layers of different extruded material, an object is created

one layer at a time.

Parts

The basic parts of the 3D printer include the print bed, heated surface, bed

surface, filament, and extruder (Figure 1). The frame holds the entire machine. Similar

to a 2D paper printer, a 3D printer’s head moves as per instructions in all directions, and

the nozzle on the print head deposits layers onto a platform or bed where the object is

printed. The motor controls the movement of the head and manages its position. The

temperatures at the extruder nozzle and the motor are controlled by the internal

electronic components.

Materials

There are a number of different types of compatible 3DP materials available to

create a desired object (Table 2). Each material has specific properties and layer

thickness requirements to impart strength and give shape. The most commonly used

3DP materials in healthcare include metals, resins, and wax3.

3DP in Urology:

3DP technology with fabricated models have found many applications within

urological surgery6, 7. Generated replicas can be used in preoperative surgical planning

and can enhance medical education, serving as a platform for the teaching of surgical

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techniques and the counseling of procedures to patients and their families8.

Applications for 3DP in urology are summarized below based on organ type.

Kidney:

Renal Masses

The use of 3DP in the clinical care of renal disease seems to be most highly

utilized and studied in the treatment of renal masses. 3D kidney and kidney tumor

models have been created with silicone, wax, or polymers most commonly using CT

and MRI as the standard 2D source images9. These materials reproduce the shape

and elasticity of the living organ with similar mechanical strength. Smektala et al.

evaluated the workflow of preparation of low-cost individual silicone replicas of kidneys

for laparoscopic training and surgical simulation of complex nephron-sparing

surgeries10. The work flow consisted of four steps: 1. image segmentation, 2. casting

mold design, 3. manufacturing of the casting mold, and 4. silicone replica casting. The

authors prepared 5 silicone kidney models for 5 consecutive patients undergoing

laparoscopic partial nephrectomy due to suspected renal cell carcinoma. Average

times for image segmentation, casting mold design, casting mold printing, and pouring

of silicone replicas were 94 minutes, 22 minutes, 14 hours, and 30 minutes,

respectively. The average costs of casting mold printing and casting of silicone

replicas were only $14.4 and $7.4, respectively, although this study was performed in

Poland where costs run lower. Dwivedi et al. also created patient-specific, 3D-printed

renal tumor molds based on volumetric segmentation of 6 renal masses from multi-

parametric MRI findings11. Adequate fitting of the tumor specimens from surgery

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within the 3D molds created preoperatively was achieved in all patients, proving

accuracy of the technology. The average cost of printing each mold in this United

States study was $160 (range: $20 – $350).

Nephron-sparing surgery in the primary treatment of small renal masses with

suspected renal cell carcinoma can be challenging due to variable renal hilar anatomy

and unclear depth of invasion of renal tumors into the cortex and sinus fat. One of the

most important advantages of 3DP is its ability to provide increased knowledge of

anatomic detail before surgery as well as tactile feedback12. Zhang et al. reported an

effectiveness score of 7.8 and realism score of 6.0 (on a scale of 1 – 10) using 3D-

printed models of kidneys with small renal masses in preparation for tumor excision13.

This increase in anatomical knowledge preoperatively can help improve surgical

outcomes by allowing urologists to rehearse planned procedures with a patient-

specific 3D model of the kidney and its accompanying renal mass. This can be

especially useful in complex partial nephrectomy cases with higher nephrometry

scores where the incidence of complications is greater14. Westernman et al. reported

that 3D stereolithographic kidney models provided tactile and anatomic information

that offered advantages over digital 3D reconstructions alone with the potential to alter

preoperative surgical planning and significantly enhance successful performance of

complex nephron-sparing surgery15. By rehearsing operative procedures with a 3D

model of the patient’s anatomy, surgical approaches along with their risks and

limitations become more evident and can be realized beforehand. This may cause a

change in the surgical approach, improve precision, and thus improve patient

outcomes16. Wake et al. generated 3D-printed models using MRI of 10 renal mass

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cases with a nephrometry score greater than 5 (range 6 – 10) and evaluated surgical

approach from three experienced urologic oncology surgeons with and without the

models through questionnaires. There was a change in the planned approach with the

3D-printed model seen in 30% – 50% of cases with the largest impact seen regarding

decisions on transperitoneal or retroperitoneal approach and hilar clamping. The 3D-

printed models helped increase confidence regarding the chosen operative procedure

in all cases.

3DP has also been shown to improve surgical outcomes such as operative

time, blood loss, and warm ischemia time during partial nephrectomy. Golab et al.

created 3D-printed silicone kidney models from digital 2D CT scan images from three

patients with complex renal masses17. The patient’s surgery was preceded by a

laparoscopic simulation of the operation on their respective silicone model in which the

tumor was excised and renorrhaphy was performed. The average time of the live

partial nephrectomy on the patient was slightly shorter than that of the silicone model

(16 versus 17 minutes) and warm ischemia time was reduced (less than 9 minutes).

The authors concluded that training with the silicone model helped improve operative

efficiency during the live case.

3DP with modeling can enhance planned communication among physicians of

different specializations in complex renal tumor cases where multiple teams are

required. For example, Golab et al. used 3DP with tumor modeling from a digital

image to plan for a rare, complicated surgery involving removal of a malignant renal

cell carcinoma with tumor thrombus extending to the right atrium requiring

coordination from vascular and cardiothoracic surgery18. The printed kidney tumor

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model, the authors reported, was an essential element of communication between

physician groups both preoperatively and intraoperatively.

Medical education of students, residents, and patients as well as their families

serves as another important application of 3DP with regards to the anatomy and

pathology of renal masses19. The Center for Research in Education and Simulation

Technologies (CREST) teaching methodology supports the use of 3DP to benefit the

education of residents with use of anatomical models and surgical simulation20. 3D-

printed kidney models can also enhance the understanding of patients and their families

with regards to the goals of their surgery, pre-and post-operative kidney anatomy, and

overall change in renal function13, 21. Bernhard et al. reported that in patients with a

primary diagnosis of a renal mass who were being considered for partial nephrectomy,

real-time demonstration and patient counseling with a life-sized, patient-specific 3D-

printed kidney replica led to an increase in patient satisfaction during their visit22. After

viewing their personal 3D kidney model, patients demonstrated an improvement in

understanding of basic kidney physiology by 16.7%, kidney anatomy by 50%, tumor

characteristics by 39.3%, and the planned surgical procedure by 44.6% compared to

patients without this visual aid.

Nephrolithiasis

Another area of potential utilization of 3DP in the kidney is in the management of

nephrolithiasis as well as the introduction of novel therapies in the treatment of this

disease. The renal collecting system can be constructed with 3DP based on CT or MRI

imaging using a water-soluble mold in a silicone bed23. The mold is then washed away,

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leaving a replica of the collecting system. This process, however, is currently expensive

and time consuming, limiting its routine application. Adams et al., however, reported the

construction of soft 3D-printed phantoms of the human kidney with collecting system by

using a novel technique that combines 3D wax printing and polymer molding at a much

more cost-effective price point24. Anatomical details and material properties of the

phantoms were validated in detail by CT scan, ultrasound, and endoscopy. Finally,

Ghazi et al. created models of the renal pelvicalyceal system (PCS) using polyvinyl

alcohol hydrogels and 3D-printed injection molds25. Five experts (>100 cases annually)

and 10 novices (<20 cases annually) completed simulations of percutaneous

nephrolithotomy (PCNL) with excellent face and content validity with an average score

of 4.5 and 4.6 (out of 5), respectively.

Designing and creation of the renal PCS with 3DP can help facilitate the

implementation of novel devices in the treatment of nephrolithiasis. Antonelli et al.

evaluated a novel device to prevent stone fragment migration during percutaneous

lithotripsy in a human collecting system model created on a 3D printer26. This

polyethylene sack stone entrapment device (the PercSac), which fit over the shaft of a

rigid nephroscope, resulted in more efficient PCNL in an in vitro 3D-printed kidney

model with a shorter median time for stone fragmentation and a shorter total time for

stone clearance.

3D-printed models of the renal PCS, similar to literature seen with renal masses,

have also shown great promise in medical education and provide an excellent teaching

tool to train residents, especially in the context of work hour requirements. Currently,

training for percutaneous renal access for PCNL procedures involves the use of

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anesthetized pigs or training in the simulation lab, but 3DP with kidney replicas could

serve as a supplement or substitute to other educational methods although there is lack

of consensus regarding the best teaching tool. Atalay et al. investigated the impact of

3D-printed PCS models on residents’ understanding of anatomy prior to PCNL in five

patients. After examination of the 3D models, residents were 86% and 88% better at

determining the number of anterior and posterior calices, respectively, 60% better at

understanding stone location, and 64% better at determining the optimal calyx for entry

into the collecting system. These same set of authors then evaluated the utility of these

3D models in patient education and counseling the day before planned PCNL surgery27.

Based on questionnaire forms administered and completed by the patients before and

after presentation of the 3D model, understanding of basic kidney anatomy increased by

60%, kidney stone position by 50%, the planned surgical procedure by 60%, possible

surgical complications by 64%, and overall satisfaction by 50%.

Transplantation

Minimal research has been performed with 3DP in the area of renal

transplantation although it is a promising area of future application. Kusaka et al.

reported on the creation of a 3D model of a patient’s donor kidney and pelvic cavity

using stereolithographic 3DP techniques to help facilitate education and surgical

planning28. The objective of this study was to help surgeons reduce cross-clamp time

and the amount of blood loss with the end goal of reducing perioperative morbidity and

mortality for the included patients. The 3D-printed model was created to help determine

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factors such as placement of the transplant kidney within the pelvis and vessel length to

help create a more personalized surgical approach and improve outcomes.

Prostate:

The vast majority of studies examining 3DP of the prostate gland deal with the

management and treatment of prostate cancer. They examine optimization of diagnosis

with MRI and ultrasound-guided fusion technologies or improvement of outcomes after

radical prostatectomy.

Combining prostate MRI and 3D-printed prostate models has been shown to

improve the histological correlation rate for prostate adenocarcinoma29. Wang et al.

explored the effect of 3D-printed prostate modeling in assisting with prostate biopsy

using cognitive fusion in 16 patients with suspected lesions on 3-Tesla (3T) MRI30. 3D

printing-assisted cognitive fusion improved the detection of prostate cancer from 22.4%

with systematic biopsies to 46.2% with targeted biopsies.

Similar to partial nephrectomy, 3DP of the prostate gland can assist with surgical

planning, physician education/training, and patient counseling31. The identification of

the anterior pudendal artery and the dorsolateral neurovascular bundles (NVBs) that

control erectile function are extremely important when performing robotic-assisted

radical prostatectomy (RARP). The preservation of the dorsolateral NVBs is essential in

decreasing the incidence of permanent post-prostatectomy erectile dysfunction and

maintaining quality of life after surgery. It is often difficult to identify these structures

secondary to the inherent, deep location of the prostate behind the pubic bone.

Combining the input of magnetic resonance angiography with 3DP to create a patient-

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specific replica of prostate anatomy can help increase the rate of identification of these

structures intraoperatively32. Inspecting 3D models before and during surgery can also

allow for tactile feedback and interaction that robotic-assisted technology currently lacks

in real time33.

Shin et al. evaluated 5 patients with clinically localized prostate cancer with a

dominant lesion visible on pre-biopsy multi-parametric 3T MRI rated as Prostate

Imaging Reporting and Data System (PI-RADS) 4 or 5 with a high probability of

microscopic extracapsular extension34. Manual segmentation of the entire prostate

gland, the biopsy-proven index lesion, and the bilateral NVBs was performed to create

life-sized, 3D-printed prostate models demonstrating all three key anatomic aspects.

The authors reported that this detailed preoperative knowledge of the prostate, cancer

anatomy, and distance or proximity of the index cancer lesion to the prostatic capsule

and NVBs enhanced intraoperative precision and confidence of the surgeon during

RARP. The cost of creating the 3D-printed prostate models was approximately $500

per case.

3D-printed prostate models have also been reported to assist with emerging

technologies such as cryotherapy or high intensity focused ultrasound (HIFU) that

perform focal ablation of prostate tumors as well as with radioactive seed implantation

during treatment with brachytherapy35, 36. They may assist in the measurement of

quantitative transrectal shear wave elastography, which has shown a sensitivity of 77%

and specificity of 82% in predicting radiorecurrent disease within the prostate gland

based on salvage RARP specimens37.

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Other:

In addition to the above, 3DP has been effectively used for urological surgeries

involving the adrenal gland, ureter, tunica albuginea, and urethra38-44. Srougi et al. used

a preoperative 3D-printed model of an adrenal gland to successfully preserve hormone-

secreting function in a patient undergoing concomitant total adrenalectomy and

contralateral partial adrenalectomy with the end goal of avoiding long-term hormonal

replacement42. Cheung et al. also implemented 3DP in an obstructed ureteropelvic

junction model as a laparoscopic simulator in the surgical training for pediatric

pyeloplasty45. The model’s usability and realistic feel gave it promise as an educational

tool.

Limitations:

As can be seen from the multiple references above, most studies in urology

dealing with 3DP have very small sample sizes, making it difficult to make generalized

conclusions about the effects of 3DP on surgical outcomes as well as extrapolate these

results to other patients. The costs and time of hardware, software, and material

creation is also a concern especially in the current healthcare climate where resources

are already over-priced and inefficient. Other issues such as material biocompatibility,

regulatory compliances, ethical implications, and the potential for abuse of

pharmaceutical bioprinting remain significant hurdles to the commonplace use of this

technology in clinical medicine.

Future Directions:

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As 3DP develops, customization, on demand manufacturing, and ease of

production will continue to improve. Drug development and customization with 3DP will

allow for more personalized medications at lower production costs due to the ease with

which 3DP allows for molecular change. Spritam, an FDA-approved antiepileptic

medication, is the first drug manufactured using 3DP and is already available in the

marketplace.

Medical device development is another area of future promise with regards to

3DP in healthcare and urology46. Del Junco et al. created 3D-printed ureteral stents

and examined its flow characteristics compared to contemporary stents in an ex vivo

porcine model with antegrade irrigation of saline38, 39. Mean intraluminal flow rates for

the 3D-printed ureteral stents were significantly higher than the 6 French (F), 7F, and

8.5F stents, and mean extraluminal flow rates were lower compared to 6F and 8.5F

stents. Total flow rates were comparable in all groups. Park et al. also successfully

designed and fabricated an anti-refluxing ureteral stent with a polymeric flap valve that

prevented backward flow using a 3D printer in vitro41. Backward flow rates were

decreased by 8.3 and 4.0 times in uncoated and coated stents, respectively, at applied

pressures of 50 cm H2O. Finally, Cui et al. used 3DP to develop a novel guiding device

for electrode implantation in sacral neuromodulation procedures. The customized 3D-

printed guiding device facilitated quick and precise implantation of the electrode into the

target sacral foramen and could be use in the future to improve surgical efficiency47.

A final area of potential impact for 3DP in clinical medicine and urology is the

bioengineering of tissue or even full-scale organs for possible implantation48-50. Yu et

al. explored the feasibility of 3DP of polycaprolactone (PCL) scaffolds for tissue

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engineering applications of tunica albuginea43. Zhang et al. was the first to utilize 3D

bioprinting technology to fabricate tubular and spiral scaffolds using PCL polymers

laden with urothelial and smooth muscle cells in a hydrogel to replicate the native

urethra in rabbits. The 3D-bioprinted tissue demonstrated similar mechanical

properties and cell bioactivity compared to the animal models. Huang et al. also

evaluated the effects of urethral reconstruction with a 3D porous bacterial cellulose

scaffold seeded with lingual keratinocytes in a rabbit model. This bioengineered

tissue was then used to successfully repair rabbit ventral urethral defects measuring

up to 2 cm.

Conclusion:

With reduction in cost, 3DP will become an indispensable tool with wider

applications in patient care and urology. Its utility in pre-surgical planning and medical

education is expanding, and its ability to efficiently design and create patient-specific

instrumentation, prosthetics, pharmaceuticals, and even complex solid organs for

transplantation could be revolutionary. Standardization and protocol development will

continue to make this technology more user-friendly with time as hardware, software,

and materials become more clinically integrated into healthcare systems. The field of

urology has always been at the forefront of incorporating technological advances into

clinical practice, and 3DP will likely not remain the exception.

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Figure Legends:

Figure 1: Parts of the 3D Printer for A) Stereolithography and B) Fused Deposition Modeling

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Table 1: 3DP Technologies and Materials

Technology Description Material

Binder jetting (BJ) Liquid binding agent is dispersed on powder material selectively binding it together

Ceramic, metal, sand, plastic

Bio-ink or ink jet printing Droplets of stem cells or living cells are dispersed layer by layer (i.e. organ creation)

Stem cells

Digital laser sintering (DLS) Direct metal laser melting ore Metal

Digital light processing (DLP) Traditional light source or laser used to harden photopolymer

Photopolymer

Direct metal deposition (DMD)

Laser used to melt metallic powder

Metal, titanium

Electron beam melting (EBM) Election beam melts and fuses material in a vacuum with no air and free from gaps

Metal, steel, titanium

Fused deposition modeling (FDM) or fused filament fabrication (FFF)

Thermal energy used to fuse materials

Plastic, acrylonitrile butadiene styrene, polylactic acid

Laminated object manufacturing (LOM)

Material is layered (additive) and cut (subtractive) to shape using a laser or blade

Glass, metal, foil paper, plastic

Material jetting (MJ) Printer head releases drops of material on platform

Wax, gels

Power bed fusion (PBF) Laser sinters bed of metal powder

Metal

Selective laser melting (SLM) Laser used as a heat source to melt materials into desired shapes

Metal, metal alloy, cobalt, aluminum

Selective laser sintering (SLS)

Laser sinters material, which is bound into solid objects (similar to welding)

Nylon, ceramic, glass, metal

Stereolithography (SLA) Ultraviolet (UV) light source used to harden photopolymer

Photopolymer resin

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Table 2: 3DP Materials and Their Characteristics

Material Strength Color Minimum Wall

Thickness (Millimeters)

Layer Thickness

Per Millimeter

Biocompatibility Flexibility

Acrylonitrile butadiene styrene

(ABS) Strong Many 1 3 Yes No

Ceramic Delicate White 3 6 Yes Yes

Cobalt chromium Strong Blue N/A N/A Yes No

Gold or silver Strong Gold or silver

0.5 10 Yes Yes

Nylon (polyamide) Strong Optional 1 10 Yes Yes

Polyether ether ketone (PEEK)

Strong Brown or

grey 1 10 Yes Yes

Polyjet resin Strong Transparent 1 10 Yes Yes

Resin Delicate Transparent 1 10 Yes Yes

Stereolithography (SLA) resin

Strong Transparent 1 10 Yes Yes

Stainless steel Very

strong

Gold or bronze plating

3 6 Yes No

Titanium Strongest Silver 0.2 30 Yes No

Ultem (polyetherimide)

Strong Tan, green,

or black N/A N/A Yes Yes