Two different dental 3D printing technologies are currently commercially in use in most digital dental laboratories. Both work by selectively exposing liquid resin to a curing light source in order to form very thin layers of solidified material. These layers are then stacked upon one another to create the final 3-dimensional object. The main distinction between the two various 3D printers technologies centers around the type of light source used for resin solidification.
Stereolithography
First invented in the 1980s, stereolithography (SLA) uses an ultraviolet laser as its light source to trace each increment of material deposited, thereby solidifying and curing the resin while transforming it from a liquid to a solid. SLA is the most common resin dental 3D printing process in use and has become popular for its ability to produce high-accuracy, isotropic, and watertight appliance components with fine features and deliver a smooth, detailed finish.
Digital Light Projector
Digital Light Projector (DLP) technology employs a digital projector set up in a tight grid of square pixels to project emitted light, thereby curing the resin material. Digital light processing is very similar to SLA with one significant difference: where SLA machines use a laser beam to trace each layer, a DLP machine employs a projected light source that cures an entire layer of deposited resin. Since it is able to cure an entire layer all at once, the manufacturing process is much faster than SLA. DLP technology is most suited to those situations where production speed is key and a very fine level of detailed precision is not as overtly critical – temporary appliances, denture try-ins, study models, etc.
Post-Manufacturing Processing
Similar to traditional processing methods, all dental 3D printer-produced restorations require further finishing by hand after manufacturing in order to be employed as a finished restoration. The printed parts are washed in solvents to remove any uncured resin before the object undergoes a final curing process. Most parts need to be cleared of their manufacturing sprues. Depending on the application, some assembly of components printed with different resins, such as denture baseplates with 3D printed or milled denture teeth, are often necessary to complete the restoration. Finally, finishing and progressive polishing are performed to make the appliance suitable for delivery to dental practices and use.