3D printing in dentistry
Introduction
Developments in digital dentistry have seen the dental sector undergo tremendous change in recent years.
In particular, additive manufacturing has enabled the dental industry to develop its use of digital technologies.
The dental sector is a market driver for 3D printing technology, as it responds to the issues of customisation.
A few key figures
In 2015, the 3D printing market for the dental industry was worth $780 million. According to SmarTech Publishing, a leading firm in market research creation for additive manufacturing, the medical sector (including dental) accounts for 11.3% of additive manufacturing technology users.
The firm also reports that the dental 3D printing market will grow to over $3.1 billion in 2020. This market is experiencing sharp annual growth estimated at over 35%, and is expected to tip $9.5 billion by 2027.
All of these promising figures demonstrate the various opportunities for additive manufacturing in this sector.
In this article on dental 3D printing, we’ll be detailing the techniques, materials and key uses of 3D printing technologies in dentistry, explaining the benefits and disadvantages of 3D printing for dentistry, and concluding with a look at the prospects for this innovative technique.
Dental 3D printing technologies:various procedures and materials
In industry, additive manufacturing is a process whereby a part is formed by adding another material, stacked in a succession of layers. 3D printing is the consumer name for the collection of additive processes.
In the dental industry, several technologies and materials are used in additive manufacturing.
The forming process can be physical (fusion followed by solidification, sintering) or chemical (photopolymerisation).
The technique selected depends on the application required.
Below are the main procedures used in dentistry.
FDM (Fused Deposition Modelling)
The technique involves depositing a thermoplastic filament heated to the plasticity temperature of polymer melt. In this case, the forming process is physical and uses thermoplastic materials (ABS or PLA).
FDM has the advantage of producing parts at low cost that require no post-processing. However, its drawbacks include a lack of speed, accuracy and biocompatibility. It is therefore only suitable for creating dental master models for thermoforming orthodontic alignment trays, retention trays or whitening trays.
Now, with the emergence of the latest thermoplastic material: PEEK (PolyEtherEtherKetone), this process can be used to produce biocompatible dental solutions, and, in particular, removable partial prostheses. This FDA-approved material boasts excellent chemical and mechanical resistance, while also being lightweight, for added patient comfort. Metal-free, this prosthesis has the advantage of being flavour-neutral.
Photopolymerisation
This is the main additive manufacturing process used in the dental sector. It’s a chemical procedure used in SLA (stereolithography) and DLP (Digital Light Processing) techniques.
SLA is the formation of a 3D model using successive layers, with a laser that sweeps each layer into a photosensitive liquid bath and polymerises it. The materials used are thermosetting plastics and elastomers.
This technology offers resolution and accuracy levels that are considerably higher than those of FDM, with biocompatible materials, all of which are liquid resins approved by the EC / FDA. The finish is much less complex, which reduces the overall manufacturing time.
This technology makes it possible to change materials for use with a different application. It can therefore be used to manufacture surgical guides, temporary prostheses, and burn-out elements, such as stellite components.
Metal additive manufacturing
Depicted mainly by SLM (Selective Laser Melting or Fusion Laser) and SLS (Selective Laser Sintering), additive manufacturing is used to make implants, stellites and nickel-chrome copings.
This technology needs sustained production in order to cushion the sizeable investment required.
Metal machines will also require more significant post-processing work, thereby reducing productivity; in terms of unit cost, however, this technology remains considerably more attractive.
Materials processes
Selective Laser Melting (SLM) or Laser Metal Fusion +++
Plastics
Ceramics
Selective Laser Sintering (SLS) or Metal Laser Sintering +++
Thermoplastics (polycarbonate, polyamides, polyvinyl chloride)
Ceramics
FDM (Fused Deposition Modelling) Thermoplastics (ABS or PLA)
Stereolithography (SLA)
Thermoset elastomers and plastics
Applications for 3D printing in dentistry
3D printing has chiefly been adopted by dentistry professionals wanting to produce surgical guides, customised dental trays, burn-out resin parts, impressions for moulds and temporary dental crowns.
3D printing applications in dentistry fall into three categories:
Manufacturing directly from bespoke dental devices:
These are mainly implant surgical guides that can guide the surgeon during the drilling process and thereby respect the digital pre-implant plan, including implant location, angulation and depth.
Using class III biocompatible resins, it is also possible to print 3D trays that are comfortable and perfectly adapted to the patient’s mouth, including whitening, bruxism and fluoride gel trays.
3D printing can also be used to make devices used in DFO, such as alignment and transfer trays, osteotomy guides and repositioning guides, as well as all kinds of orthoses and interception devices.
Devices for maxillo-facial surgery (genioplasty, rhinoplasty, epistheses) can also be printed in 3D.
3D impression printing for dental moulds using the lost-wax technique
A 3D version of dental prostheses (crowns, bridges, etc.) printed using burn-out resin and used to make a customised mould harnessing the lost-wax technique. The final prosthesis is obtained by pouring the desired material (ceramic, metal, etc.) into this mould.
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