Dental 3D printing creates dental parts for dentists as tools or fixtures to print parts and for patients to use. These parts can range from models of teeth and dental aligners to full sets of dentures. In the past, dental providers used scans, radiology, and teeth molds to obtain accurate images of patients’ teeth. These images were then used to construct special, tailored implants for the patient. Now, with 3D printing, dental providers can both create more specialized implants and treat patients more rapidly.

Dental 3D printing makes use of all types of AM technology, including digital-light processing (DLP), selective laser melting (SLM), stereolithography (SLA), and selective laser sintering (SLS). 3D printing not only makes life easier for dental providers but also delivers significant benefits to patients: customized, affordable dental solutions.

What Is Dental 3D Printing?

Dental 3D printing is the use of additive manufacturing to create dental parts such as aligners, dentures, and crowns. To create custom parts that match a patient’s anatomy, dental providers use a tool called an intraoral scanner. This creates images of a patient’s teeth and records them in the form of a CAD file. Dentists then use this CAD file to create implants or dental molds through 3D printing.

What Are the Dental 3D Printing Applications?

Listed below are some of the common uses of 3D printing in dentistry:

1. Implants: 3D printers with high resolutions and printing accuracy (e.g., SLA and DLP printers) are exceptional at printing complex geometries like those associated with teeth. 3D-printed implants are biocompatible and have similar mechanical properties to human teeth. Additionally, maxillofacial dental implants can be 3D-printed as well. Maxillofacial dentistry is a specialized branch of oral surgery performed to correct injuries and defects of the jaws and mouth.
2. Crowns and Bridges:Dental 3D printers can create precise crowns and bridges of both fixed and removable varieties. Burn-out resins can be printed to complete a lost-wax casting of a tooth. Patterns and geometries for casting are printed based on the results of an intraoral scanner. Dentists can then use this 3D printed patterns, burn them away, and be left with a cavity to be filled with resin. 3D printing has significantly improved the process to make crowns and bridges.
3. Surgical Guides: Dentists can use 3D printers to create surgical guides for drilling and cutting. These guides assist dentists to make surgery easier.
4. Anatomical Replicas and Models:Accurate anatomical replicas of a patient’s mouth and jaws can be made with 3D printing. This gives the dentist a tangible model that can be seen and touched to better understand a patient’s anatomy before beginning treatment.

How Is 3D Printing Used in Dentistry?

3D printing is used in dentistry to obtain accurate images and models of the anatomy of a patient’s teeth and jaws. An intraoral scanner captures the exact anatomy of a patient’s mouth. The data from the scan is then used to construct a 3D-CAD model of the desired anatomy. The CAD file, once completed, is uploaded to a 3D printer and built. Dentists can go through several iterations before they obtain a model that is both accurate and comfortable enough for the patient.

Using an intraoral scanner and corresponding images, dentists can also print surgical guides that help during an operation. This enables safer surgery, faster healing, and added prosthetic comfort.

What Material Is Used in the 3D Printing of Teeth?

Materials used in dental 3D printing are not the same as those typically used in 3D printing of other industrial products. Dental 3D printing materials are designed specifically for biocompatibility, aesthetics, and safety in dental applications. Certain resins are explicitly used for anatomical models and replicas (referred to as model resins). Others are designed for implants (draft and castable resins). Additionally, there are resins that are used for creating temporary dental appliances, resins that print clear for use in creating mouth guards, and resins that resemble gingiva for use with dental implants.

Depending on the manufacturer, resins can have different chemical compositions. There is no prescribed standard for dental 3D printing materials, however. Dentists usually select the material they think is best for the patient’s dental application. If several appropriate choices exist, they may discuss them with the patient.

How Are 3D Printed Dentures Created?

1. Obtain a digital model of the dentures to be printed. This can be done by creating a 3D-CAD file via an intraoral scanner.
2. Choose a suitable material for the dentures.
3. Print the dentures with the chosen material based on the created CAD file.
4. Remove any support material from the dentures.

For How Long Can 3D Printed Dentures Be Worn?

3D-printed dentures can be worn in the same way as normal dentures. They should be removed and cleaned with a denture cleaner daily. They should also be kept moist in a secured case when not in use. 3D-printed dentures can be expected to last about 5-7 years before possibly needing replacement.

What Materials Are 3D Printed Crowns Made of?

Some 3D-printed crowns are made of ceramic, cast able waxes, and 3D printable resins. Cast able waxes and resins are composed of about 20% wax. The wax is what helps the crown stick to the patient’s mouth and helps the crown have a similar density as actual teeth. For 3D printed crowns, however, many of the chemical compositions of materials are proprietary and vary from company to company. The technical data sheet of the resins should be reviewed to determine the specific material formulation for the resins.

According to different working principles, 3D printing technologies can be divided into three categories: PBF, light curing, and FDM. As illustrated in Table 1, they can be refined into specific technologies, each with its distinctive advantages.

Powder Bed Fusion (PBF). Any powdered material, which can be sintered or fused by laser radiation and solidified by cooling, could be suitable for laser sintering or fusion technologies [18]. According to the energy sources and powder materials, PBF is divided into the following printing technologies: selective laser melting (SLM), selective laser sintering (SLS), electron beam melting (EBM), and direct metal laser sintering (DMLS) [19]. All these technologies use heat to melt powdered materials.

In dentistry, PBF is used to manufacture all kinds of metal products including AM titanium (Ti) dental implants, custom subperiosteal Ti implants, custom Ti mesh for bone grafting-techniques, cobaltchromium (Co-Cr) frames for implant impression procedures, and Co-Cr and Ti frames for dental implantsupported prostheses.

Moreover, PBF shows considerable potential for manufacturing ceramic restorations, which can be used to manufacture frame crowns, model casting abutments, and models.

The definitions of the terms “laser sintering” and “selective laser melting” are inconsistent. The operating ambient temperatures of SLS and DMLS do not reach the materials’ melting points. The metal powder is partially melted, which results in a large porosity and a rough surface. However, in the SLM process, the powder melts directly at the melting point. Another technique, EBM, differs from SLM by using an electron beam to melt the material. Both technologies completely melt the metal powder in an inert build chamber containing purified argon gas.

PBF uses the roller to apply the powdered substrate from the reservoir onto the build platform. Thereafter, a laser or electron beam selectively fuses the powder particles according to the crosssectional configuration of the CAD file being produced. The shapes of the build platform descend by orders of magnitude in the thickness of the printed layers, and then the process goes in cycles until the object has finally been built.

Ti and its alloys are particularly suitable for 3D printing technologies, particularly SLS. Studies have demonstrated that Ti structures fabricated using 3D printing technologies have great yield strength, ultimate tensile strength, and excellent ductility. Ceramics can also be used in SLS; however, manufacturing ceramics for dental applications employ an indirect technical measure that relies on polymer bonding to fuse ceramic particles. The molded parts produced are fully cleaned and sintered.

SLM does not require any debinding process as it does not involve binders to produce intermediate green fragments. The fabrication time based on PBF is also shorter than that of other 3D printing technologies. However, higher heating and cooling rates may lead to thermal shock and rupture. This can be avoided by preheating the powder. SLS-based products can be weak and porous and require complex postprocessing. A variation based on this technique is known as DMLS whose products are quite dense

SLA is one of the earliest practical 3D printing technologies, and its device consists of a reservoir for the material supplier of photosensitive liquid resin, a model build platform, and an ultraviolet (UV) laser to cure the resin. In the building process, the build platform is submerged in a liquid resin, and the resin is polymerized using a UV laser. Then, the build platform moves a distance equivalent to the thickness of one layer, and the uncured resin then covers the previous layer. There are two ways to move the platform in SLA technology. The first is the top-down movement of the platform. A layer of resin covers the construction platform that is soaked in the resin reservoir. After scanning the first layer with the laser, the construction platform moves down, and a new layer of resin is added by a wheel next to it. The build cycle is repeated until the object is created. In contrast, in the platform-bottom-up approach, the platform is submerged at the bottom of the resin reservoir, and the gap between the platform and bottom can spread only a single layer of resin. The laser is placed at the bottom of the reservoir, and the resin layer would be scanned. After curing, the platform increases the distance of one layer, and the resin material can completely fill the gap between the platform and the bottom owing to gravity. The platform-bottom-up approach has several advantages over the platform-top down approach. First, in the second approach, the resin is in direct contact with oxygen as it undergoes polymerization, whereas light-curing occurs at the bottom to avoid oxygen interference in the platform-bottom-up approach. Second, the laser is located at the bottom, which reduces the potential for injury to the operators. Third, the resin can be refilled automatically owing to gravity. Therefore, most SLA printers currently introduce this technology.

In the case of ceramics, SLA incorporates ceramic particles into a curing resin that selectively cures a ceramic slurry. As the viscosity of the slurry affects the mechanical properties of the structure, the ratio of the ceramic powder content to the resin needs to be balanced. Ceramics with different chemical compositions, such as alumina and zirconia, have good mechanical resistance and are suitable for polycrystalline ceramic crowns Therefore, this kind of ceramics is the focus of research and development of SLA. The DLP technology microsystem consists of a rectangular arrangement of mirrors, called a digital micro reflector device. Each mirror represents one pixel, and the resolution of the projected image depends on the number of mirrors. The angles of the micro reflectors are adjusted individually. The light emitted by the light source is refracted by the micro mirror and then projected onto the surface to be printed as one pixel. Compared to scanning the layer sequentially using a laser in SLA technology, the advantage of DLP is that the entire layer can be constructed by single laser irradiation. As each layer is constructed independently of the respective layer shape or the number of pixels, the construction time can be reduced.

Fused Deposition Modeling. FDM is one of the most popular and cheap 3D printing technologies in dentistry. The filamentous thermoplastic material is heated and melted by the nozzle. Under the control of the computer, the nozzle and worktable move in the X- and Y-axis directions, respectively, and the material in the molten state is extruded and finally solidified through the accumulation of materials layer-by-layer to form the product. Polylactic acid (PLA), polycarbonate, and polyamide, acrylonitrile-butadiene-styrene copolymers are some of the engineering thermoplastics commonly used for FDM applications.  PLA is more environmentally friendly and suitable in the oral cavity. Yefang et al. mentioned that medical grade polycarpic acid-tensioned-tricalcium phosphate scaffolds constructed using FDM are biocompatible and have high mechanical strength and can be used as tissue scaffolds in dentistry. Moreover, Chen et al. demonstrated that custom pallets produced by FDM technology can fit plaster models.