3D printing is a revolutionary concept based on
additive process. It offers multifaceted applications
for dentistry in general and prosthodontics
in particular. A myriad of advantages like
reproducibility, accuracy, customisation and ability
to create complex parts with ease in less time have
provided improved patient treatment options and
compliance. This article presents an overview on
currently available technologies and their utilisation.
Abbreviations: CAD-computer aided designing, FDM-fused deposition modelling, SLS-selective laser sintering, SLA- standard triangular language, PLA-polylactic acid.
Key words: 3D printing, CAD/CAM, additive manufacturing, bio printing, selective laser sintering, fused deposition modelling.
Charles Hull in 1983 printed the first 3D-object
Digital dentistry was
pioneered by Francois Duret in 1970, with some
initial hiccups it took time to be integrated into
Last few years have seen strikingly increased application of 3D printing. The desired object/site is scanned using an intraoral (IS) 3D scanner or built using a CAD software. IS consists of a mini camera, integrated software and a computer.
Data is obtained as STF files (standard triangular language)/STL (standard tessalation lan-guage). This information is always broken down and stored as triangles or tessellation. The tessellation is the process of linking the surface with geometric shapes to avoid overlaps and gaps. Stitching the triangular files leads to a process of STL2 . These STL files store the surface geometry of objects and this information is encoded in ASCII (American Standard Code For Information Interchange) or Binary coding mostly which is used for small sizes3 . This in-formation is used to print objects in layers through various digital slicing and physically re-produces layers with an automated process4 . Additive Manufacturing is an additive process referred to as rapid prototyping where a lot of layers are added in contrast to traditional process like subtractive manufacturing5
. The most widely used additive methods include fused deposition modelling (FDM), Stereo lithography (SLA), Selective laser printing (SLS), Polyjet Printing and Bioprinting6 , Direct metal laser sintering. A variety of materials can be used which include plastics, ceramics, resins and metals
Developed by Scott Crump 1988, melted material
generally thermoplastic polymers such as poly
lactic acid (PLA) polycarbonate, polyether ether ketone (PEEK) is extruded through a nozzle to
print layer by layer. Print head has multi nozzle
and extrudes different types of material at the
. It is the printer of choice for in-house
production of 3D models8
. It is a flexible method
however its use is limited to temporary crown and
bridges manufacturing. Limitations include limited
colour selection, moderate printing resolution, and
complete removal of support material, surface
quality and time efficiency.
Both use laser to scan and build object layer by
layer but in selective laser sintering powder-based
material is used for printing.
SLA uses photo polymerisation - a process by which the UV laser beam causes chain of molecules to link together and form polymers.9 Products are built with application of UV laser inside a vat of resin.10
SLA is used for printing from CT (DICOM data). Advantages include good printing resolution as compared to FDM; support material removal is less too hence less wastage.
SLA is used to print surgical guides, aligners, dental models and crowns, RPD’s, fabrication of implant surgical guides.
SLS prints FDP’S, metal crowns and RPD’S. They can replicate intricate geometries and provide biodegradable scaffold for tissue engineering.
Printers with highest resolution. 3D model is
created one layer at a time by the printer head
getting layers of liquid photopolymer acrylic plastic
build tray followed by UV light curing11. It uses
widest choice of printing materials with varieties
in density, hardness, flexibility and porosity.
Resolution is as fine as 25-80 microns, faster
printing and replication of complex geometries.
Disadvantage includes post print model processing such as intensive washing and removal of support material.12
Applications include planning patient specific 3D models with complicated geometries, surgical stents and guides, phantoms for orthopaedic and cardiac surgeries, scaffolds for tissue engineering.13, 14, 15
Uses photo polymerising materials stimulating natural cells such as chitosan, agar, alginate to
print hard and soft tissue scaffolds. Bio printing
uses cell ink based bio printers or spheroid or
micro tissue based systems have been developed
to generate artificial tissues, complex 3D in vitro
models.16,17 With that the additive manufacturing
has given a new face to discipline of stem
cell therapeutics with the flexibility of printing
cells into desired 3D complex, employing it for
transplantation and regeneration.18 3D printing
has found its applications in generating optimal
values of human bone and skin grafts in vitro.19
This has immense potential to replace the current
strategies of procuring auto grafts which is
associated with donor site morbidity and loss of
This technology is used to produce metal parts with
high accuracy and better mechanical strength. In
this technology metal material is added layer by
layer and a laser beam is used to fuse metal at a
point.21,22 This uses titanium, cobalt, aluminium,
bronze alloy, steel. Approximate accuracy is 25-
3D models are fabricated by adding layers of the
defined sheet of materials. A laser is used to cut
sheet as per the required cross section. Adhesives
are used to combine the layers and generated by repeating the steps.23,24
Powerful electron beam is used to build product
layer by layer by using a metal powder by
command of the CAD model with exact geometry.
Under a vacuum the raw material is stored and
fused by an electron beam.25, 26 Vacuum eliminates
A literature search using search engines such as
Google scholar and Pubmed with keywords was
done, all articles from 2016 to 2020 printed in
English, inclusive of case reports, in vitro studies
and systematic reviews were considered.
Minev R, Minev E, 201627 stated that shrinkage
of 3D printed models is an unavoidable problem
during the printing process and it affects printing
accuracy of most 3D printers. FDM shrinkage
occurs due to thermal contraction when melted
filaments solidify. In SLA and multijet shrinkage
occurs due to polymerisation. Hambali RH, Cheong
KM, Azizan N, 201728 concluded that FDM has
bad surface quality due to staircase effect of
manufacturing using material extruding through
a nozzle. This was improved by approximately
97.2% via immersion in acetone solution for 300
seconds. This chemical treatment is one of the most
economical and fast methods to enhance surface quality of additive manufacturing parts for future
manufacturing industry. Raymond E Rebong et
al 201829 assessed the dimensional accuracy of
3D models with each other and compared with
traditional plaster casts. They concluded amongst
FDM, SLA, and Polyjet printing, the FDM had
fewest dimensional measurement differences as
compared to plaster mode.
Daniel Khorsandi et al 201830 Compared SLA and FDM methods of rapid prototyping. They stated that SLA offers greater efficiency, high level of accuracy. Layer thickness of two different techniques FDM 0.5-0.127mm as compared to SLA 0.05-0. 015mm. Both however make rough patterns that need to be polished to limit bacterial retention. Ucar et al, 201831 published an in vitro study to show that the ceramics manufactured by stereolithography show comparable mechanical properties to milled ceramics. However, manufacturing process and strength, fracture toughness are areas that require further research. To improve the properties of ceramics so produced, porosity should be eradicated resulting in denser more compact mixture. Kim et al, 201832 proposed a new digital prosthesis using an FDM printer to make a flask for making a complete denture. This took 7 hours to complete and showed satisfactory results in terms of completeness of complete denture. Using a universal development system software, denture design STL and a denture flask STL were superimposed, and the denture region was set as an empty space. Conventional artificial teeth were inserted into the 3D manufactured flask, resin packing, finishing and polishing was done using conventional method of fabrication of complete denture. Fusong Yuan, Yao Sun, Lei Zhang, 201933 implant guide CAD and FDM 3D printing were used to achieve a chair- side high efficiency design for production of implant guides. Visual inspection revealed that the positioning of 30 implant guides was successful and retention was satisfactory. A comparison of 3D data of printed implant guide and CAD guide demonstrated a morphological error of 0.5999 plus minus 0.146. Making FDM and CAD time saving, efficient chair side methods. Lee D et al, 202034 stated digital light processing 3D printers (DLP) produce shrinkage depending on the material and polymerisation method. Owing to material characteristics the FDM accuracy of full arch dental models is supposed to be higher than that of the DLP however due to surface roughness of the FDM method the crown preparation die for dental prosthesis is not accurate. Therefore, a new hybrid dental model that combines the FDM for full arch and DLP for specific die is proposed.
Yoshiki Ishida et al, 202035 Compared the accuracy of cylindrical patterns fabricated with consumer FDM 3D printers with consumer SLA 3D Printers. After the patency of FDM device expired, several types of small consumer 3D printers were introduced for personal use. The accuracy of these less priced printers was compared with dental FDM 3D and SLA 3D printers. The consumer printers had worse accuracy than dental printers. An enlargement adjustment of 1-3% along the horizontal axis was necessary to realise the set design. In terms of surface roughness consumer SLA produced smooth patterns. Hence, they concluded that consumer printers have potential to be used in dental applications.
Not only for manufacturing 3D has led to an exemplary shift in training by providing idealistic plastic typodonts to more real-life 3D printed models that are based on data obtained by intraoral scan of patients36. Polyjet printing has successfully been used to create models in different levels of hardness, replicating that of healthy enamel, dentin and caries so that the trainee experience proprioception of working on real tooth37. 3D manufacturing undoubtedly offers a promising future due to its multiple applications and accurate detail reproduction however at the same time it involves high investment cost. One of its largest limitation is the quality. Due to the way successive layers are deposited on top of each other an inherent weakness is literally build into the design. Finishing of final product is time consuming and requires skill. Depending on the material it may need additional treatment to reach full strength. For example, zirconia blocks used require further sintering to reach high strength. SLA can be done only by using photopolymerising resins. These are messy and can cause inflammation and irritation on inhalation. Also, resins cannot be heat sterilised.
3D printing has the potential of revolutionising
dentistry in general and Prosthodontics in
particular. Although the initial investment is high
and it requires training in usage, it helps to reduce the time for actual patient care. In today’s
scenario of emerging infective pandemics minimal
exposure to the clinician, technician and patient
can be offered. It can allow patient care from any
part of the world by exchange of information. It
has a great potential in research and treatment
modalities. Because the print object is produced according to the image of the patient, the print
can be tailored to optimally fit the condition of the
patient. The problem that requires further research
is the limitation of available material assortment
in particular when moving beyond the canonical
polymers as well as improvement of printing speed
and post processing requires.
Although it is not a replacement for conventional treatment methods but its scope to improve and develop is what the future of dentistry holds.
Source of support:
Conflicts of interest:
The authors declare no conflicts of interest.