Three-dimensional (3D) Printing involves a number of manufacturing technologies that generates a physical model from obtained digital information. 3D Printing as a technique entered prototyping more recently in the 21st century. It was Charles Hull who printed for the first time, in 1983, a 3D object using the first 3D printer. Developments in computer technology and software applications have taken 3D Printing to where it is today.
Method
Three major steps are involved: the data procurement, processing and then actual fabrication using additives.
The first step is critical, that requires images which are obtained from CT scan or an MRI. The images procured are utilised in synthesis of a computer-aided design drawing of the object to be fabricated. The 3D printer then uses the coordinates from the 3D model to enable, its servo motors that move the print head along the x–y plane to fabricate a layer. This is repeated along the z-axis for fabricating the third dimension. Other information that dictates the colour, texture and thickness is fed in the STL file format. Materials used for 3DP includes acrylonitrile-butadiene-styrene (ABS) plastic, poly lactic acid (PLA), polyamide (nylon), stereo lithography materials (epoxy resins), steel, silver, titanium, photopolymers, wax, and polycarbonate, glass-filled polyamide.
3DP technologies
The following are the major techniques adopted in 3D Printing.
Stereolithography is used to create models, prototypes, patterns, and production parts in a layer by layer fashion by using photochemical processes where the light causes chemical monomers to link together to form polymers.
Photopolymer jetting, is a 3D Printing technique where an ink type print-head jets a light-sensitive polymer onto a platform building layers incrementally.
Digital light processing technique builds up the object upside down by using liquid resin and a light source on an elevating platform.
Powder binder is a process which utilises water from an inkjet printer head that is projected onto a powdered bed to build up the object. This technique is cost effective but it falls short on the resolution, it is also difficult to operate and cannot be heat sterilised.
Selective laser sintering is used to print objects from metals and polymers. It is expensive due to its very high capital expenditure and maintenance costs. It also has health risk due to dust inhalation or accidental explosion.
Applications
It has wide range of application across the fields of medical modelling, fabrication of surgical guides, also in fields of prosthodontics, restorative dentistry, orthodontics, implantology and instrument manufacturing.
The utilisation of 3Dprinting in these fields is primarily driven by improvements in affordable and high-end imaging technologies like CT scans. There is also an inherent advantage over the computer-aided design/computer-aided manufacturing milling techniques.
3DP is also applied in organ printing by producing cells and biomaterials individually or layer by layer and fabricating a tissue-like structure. This could help overcoming the huge shortage currently faced in sourcing organs from donors.
Further, 3D printing also has the potential in production of personalised medicines in latest formulations such as pills that include multiple active ingredients, as a complex multilayer or multi reservoir printed tablets, microcapsules, multi-layered drug-delivery devices and nano suspensions.
Porous titanium implants can be easily fabricated using 3D Printing. By focusing a high-power laser beam, it fuses the metal particles on a powdered bed generating the desired implant design layer by layer, with no requirement of post processing steps.
Use of 3D printing in digital orthodontics is in production of Invisalign. The InvisalignR system digitally realigns the patient’s teeth to make a series of 3D printed models to manufacture ‘aligners’, which continuously reposition the teeth over a period of months/years.
Other varied application in dentistry includes fabrication of crown copings, partial denture frameworks, surgical instruments, oral and maxillofacial implants, forensic odontology and simulation models synthesised for education.
Advantages
The conventional subtractive manufacturing technique such as milling creates high wastage by their very nature. This is minimised by utilising these 3D Printing techniques along with other additive manufacturing technologies.
3D Printing has higher efficiency, passivity, flexibility and superior material utilisation.
Disadvantages
Has extended post processing duration. Other disadvantages include its high capex, the occurrence of staircase effect (created by layered deposition), requirement of support materials (that is difficult to remove post processing) and inconsistent reproduction.
Ceramics, most popular materials used in dentistry lacks the ability to be 3D printed due to the high porosity caused during fabrication.
Conclusion
3D Printing has transformed digital dentistry by extensively penetrating opportunities in the diagnosis, treatment and education sectors. The accelerated research in this industry and optimism would help to open more doors and revolutionise digital dentistry.
