Almost no other manufacturing process has attracted as much attention in recent years as 3D printing, also known as additive manufacturing (AM). This process has already existed for more than three decades and has proved itself, for example, in prototype production and mechanical engineering. Additive manufacturing has also been used for many years in areas such as architecture, design, the entertainment industry etc. One of the currently most interesting and intensively researched areas is 3D printing in healthcare and medicine. In tissue engineering for example, scientists are attempting to produce biological tissue by cell seeding on printed frameworks . 3D printing also offers great potential in the patient-individualized reproduction of anatomical shapes. Used in combination with digital imaging procedures (e.g. computed tomography), DICOM data can be generated, segments extracted in STL format and implants (e.g. in surgery) or anatomical models printed (e.g. for surgical planning). 3D printing is also used in dentistry and dental technology, for which various 3D printing techniques have been established . In dental laboratories, a popular application is the printing of dental appliances (e.g. jaw models, impression trays, drill templates). Splints, bite plates or denture bases are also often produced using the 3D printing process. Interesting developments with the potential to change manufacturing methods in future can be observed in the printing of ceramic materials for dentures . The latest research in dental 3D bioprinting (tissue engineering) is also revealing exciting possibilities, for example in the printing of patient-specific bone substitute materials, implants and cell-loaded 3D structures . But 3D printers as a supplementary technology are not only closing a gap in the digital workflow in research, the manufacturing industry or the dental laboratory, but also in the dental practice.
3D printers in the dental practice
3D printing offers numerous advantages in the dental practice , practice laboratory and dental laboratory. For example, it can be used to produce objects with complex geometries (e.g. models, drill templates, impression trays) within a short time. In contrast with subtractive milling, 3D printing is not associated with any significant loss of material. Resin-based, light-curing 3D printer systems are usually used in the dental practice and are based mainly on the DLP or SLA technologies. A crucial difference between the two methods is the type of light source used for polymerization. In an SLA printer, the material is cured at very precise points using a laser beam, whereas the polymerization of the printing resin in the DLP printer (Digital Light Processing) is based on a projector, thereby curing the whole surface of the layer to be printed. This accelerates the printing process. An example of a modern 3D printing system based on the DLP technology is the Straumann® CARES® P20 from the company Rapid Shape.
Use in practice
Although modern printer systems often follow automated sequences, working with the printer still requires a basic technical understanding of digital technologies and some experience in CAD design. The actual printing process is comparatively quick. An assessment of the overall production time needs to take account of not only the design and the printing, but also the post-processing (cleaning, light-curing) of the printed component [10, 16]. This post-processing significantly determines the quality, including the material quality, of the printed object . If simple and reliable post-processing is desired, it is useful to opt for 3D printer systems that facilitate an extensively automated process chain. Examples include the printers from the Straumann® CARES® P series, which are embedded in a validated process chain. The system components are as follows:
- 3D printer with software,
- various 3D printing resins,
- automatic cleaning system (Straumann® CARES® P wash) and
- automated light-curing unit (Straumann® CARES® P cure).
3D printing of dentures in the dental practice
A wide range of dental applications exists for 3D printers. Printing dentures has so far proven to be a challenge. Although any geometrical shape can be produced with a 3D printer, suitable materials are needed. Dental printing materials (resins) must be able to cope with the demands of intraoral use (Medical Devices Act) . Printing resins approved for fixed restorations (crowns, bridges) have been available for some time. These include the light-curing composite P pro Crown & Bridge (Straumann) for the additive manufacturing of temporary anterior and posterior restorations. As a result, the digital workflow – subsequently presented using the example of implantology – has become a reality and offers interesting alternatives to the conventional route. Thus, the printing of temporary crowns can be viewed as an alternative to the time-consuming manually produced or milled provisional.
Patient case report: Initial situation
The young woman presented at the dental practice with symptoms at tooth 21. The tooth had been endodontically treated (multiple root apex resections) and provided with a crown (Fig. 1). The crown appeared slightly dark in the mouth and had a gray sheen. Since the tooth was also repeatedly causing symptoms, the patient expressed her wish for a new restoration. Otherwise, she had a full set of functioning teeth with no abnormal findings. Periodontal examination revealed a small recession in the anterior region of the lower jaw. The problematic requirements in the anterior region included high esthetic demands. Since the clinical and radiological diagnostic (Fig. 2) assessment revealed that an attempt to preserve tooth 21 would not offer any reliable prospects of success, the decision was made to extract the tooth. An immediate implant placement was planned in order to preserve the hard and soft tissues as effectively as possible before physiological remodeling after the extraction. The immediate insertion of an implant in the extraction socket is designed to prevent extensive bone resorption and severe soft tissue regression [7, 1, 5]. A flap-free procedure also minimizes the surgical trauma, thereby benefiting the esthetic result (no scar formation). Ultimately, the comparatively quick prosthetic rehabilitation and the reduced number of treatment sessions are arguments in support of this treatment protocol.