DLP printing for dental applications

1. A revolution in 3D printing

DLP (Digital Light Processing) printing is a recent technology that emerged in the 1990s, influenced by advances in digital projection and the beginnings of Additive Manufacturing. Originally designed for video projectors, DLP technology uses digital micromirrors, known as DMDs (Digital Micromirror Devices), which are arranged on a silicon chip and can rapidly switch between two positions.

Researchers then explored its use in 3D printing, projecting patterns of light onto photosensitive resin to create objects by selectively solidifying the resin layer by layer. Since then, DLP printing has undergone constant improvement thanks to advances in DLP projectors, photosensitive resins and post-processing processes.

The first commercial 3D printers based on DLP technology appeared in the early 2000s. Today, DLP 3D printing is used in various fields, such as jewelry, dentistry, model and prototype production, offering high printing precision and excellent surface quality.

2. The process deciphered

DLP printing is a 3D printing technique similar to stereolithography (SLA). It also uses photosensitive resin polymerization to create three-dimensional objects, but with a slightly different method. The DLP 3D printing process works as follows:

• Modeling: First, a detailed 3D model of the object to be printed is created using 3D modeling software.

• Model preparation: The 3D model is then imported into DLP 3D printing-specific slicing software. This software divides the model into thin layers and generates the necessary instructions for the DLP 3D printer.

• Light projection: In the DLP 3D printing process, a full-spectrum lamp or LED is used to project light through a Liquid Crystal Display (LCD) or another micro-mirror array called a Digital Micromirror Device (DMD). The LCD or DMD is made up of thousands of microscopic pixels that can be switched on or off individually.

• Resin curing: Light projected through the LCD screen or DMD is modulated to create a 2D image of each layer of the object on the photosensitive resin surface. Activated pixels on the LCD or DMD allow the light to selectively harden the resin, forming the solid layer of the object.

• Object construction: Once a layer has hardened, in most cases the printing plate rises slightly to allow the next layer to form. Light is then projected again to harden the new layer, which bonds to the previous one. This process is repeated layer by layer until the object is fully constructed.

• Post-processing: Once DLP 3D printing is complete, the printed object is usually removed from the printing plate and cleaned to remove any excess resin. It can then be hardened or cured further using a UV light source, if required, to improve its mechanical properties.

DLP 3D printing relies on the use of an LCD screen or DMD to selectively project light and allow the photosensitive resin to cure progressively, layer by layer, to produce three-dimensional objects.

3. MovingLight® and DLP: advanced 3D printing for unrivalled productivity and precision

The MovingLight® system uses the UV rays of a moving DLP® (Digital Light Processing) to photopolymerize photosensitive resins. Unlike traditional stereolithography, which uses a UV laser to selectively cure the resin, MovingLight® uses a matrix of micro-mirrors to project precise UV flash patterns onto the resin.

The micro-mirrors, located on a microchip, are individually controlled and can be oriented to reflect light in different directions. This precise control capability enables MovingLight® to project light flash patterns very quickly and precisely onto the resin surface.

When UV light reaches the resin, the photo initiators present in the resin are activated, triggering the polymerization reaction. Areas exposed to the light harden instantly, while unexposed areas remain liquid. The printing platform then moves vertically to add a new layer of liquid resin, and the projection and polymerization process is repeated for each successive layer.

MovingLight® technology offers several advantages over other stereolithography systems. Firstly, it enables high printing speeds, thanks to the ability to rapidly project light flash patterns. This considerably reduces printing time, which is essential for medium- to large-scale production and rapid prototyping.

What’s more, the precision and resolution achieved with MovingLight® are remarkable, thanks to the precision of the micro-mirrors and the quality of the pattern projection. Parts printed with MovingLight® therefore feature excellent dimensional accuracy and an outstanding surface finish.

High-resolution MovingLight® 3D printers are ideally suited to the production of prototypes requiring extreme precision of detail and a smooth surface. They are also ideal for producing parts for a variety of applications, including jewelry, dental models or surgical guides. In addition, they are used in fields such as investment casting, mold making for injection, thermoforming and blow-injection, and the creation of molds for shoe soles.

Prodways’ exclusive MOVINGLight® technology provides :

• Unrivalled resolution – up to 42 microns per pixel
• High productivity – print up to 10 times faster than other technologies on the market
• Large production platforms to manufacture large parts or a large number of small parts
• Innovative materials for more applications

4. Advanced applications in dentistry

DLP 3D printing has found promising applications in the dental field:

• Models for orthodontic aligners: 3D printing is revolutionizing orthodontic care through the manufacture of models for orthodontic aligners. These models enable the use of transparent, customized and graduated aligners, offering a new, invisible technique for realigning teeth. Produced using digital modeling software, these trays are thermoformed directly from 3D-printed orthodontic models.
• Crown and bridge models: The production of dental crown and bridge models from intra-oral scans or scans of physical models. These models serve as a reference for the creation of permanent restorations, guaranteeing precise fit and optimal esthetics. This enables dentists to plan and fabricate custom crowns and bridges for their patients, ensuring a perfect fit and optimum functionality.
• Surgical guides: DLP 3D printed surgical guides are used in dental implantology procedures to precisely guide the positioning of dental implants. These guides are tailor-made for each patient, based on dental scans, and enable surgeons to perform more precise and less invasive procedures.
• Customized impression trays: Since every patient is unique, the use of standardized impression trays always involves a necessary compromise between practicality, patient comfort and final results. By combining a traditional and digital approach, 3D-printed impression trays offer an alternative that combines all the advantages of customization, and is ideal for laboratories still relying on alginate molds.

DLP 3D printing has opened up new perspectives in the dental field, and continues to attract growing interest. Thanks to its precision and ability to produce complex objects with fine detail, this technology offers considerable advantages for dental applications. In the near future, we can expect even more significant advances in the use of DLP 3D printing in dentistry.