The digital workflow – from scanning to the finished crown design

A few decades ago virtually all dental technical work started with a physical plaster model cast from an impression taken in the mouth with a casting material. Today an increasingly large part of the work is digitally scanned from the start. Digitalisation does not change the purpose — the crown bridge or denture must still fit millimetre-precisely — but it changes how the dental technician gets there.

§From mouth to file

Work typically starts with an intraoral scanner at the dentist's office that captures thousands of images per second and assembles them into a digital 3D surface model of the teeth and surrounding tissues. If the lab has instead received a physical impression or plaster model it can be scanned on the lab's own model scanner. Regardless of the route the result ends up as a digital file typically in STL or PLY format that describes the surface geometry as a net of triangular surfaces.

§Designed in CAD software

The file is imported into a CAD program (computer-aided design), where the dental technician designs the replacement itself. Here the margin line — the crown's transition to the prepared tooth — is drawn with great care, because an inaccurate margin line can result in poor fit or an edge where bacteria can collect. Next the crown's own anatomy is shaped, and the software automatically checks contact points with adjacent teeth and bite against the opposite tooth row in a virtual articulator that simulates the patient's chewing movements.

• 01The margin line is drawn along the edge of the prepared tooth.
• 02The crown's basic shape is retrieved from a digital tooth library and adapted to the individual tooth's anatomy.
• 03Contact points with adjacent teeth are adjusted so the tooth sits neither too tight nor too loose.
• 04Bite contact is checked in a virtual articulator that simulates the patient's chewing movement.
• 05The finished design is nested and sent on to manufacturing (CAM).

§From file to physical workpiece

The actual production - CAM computer-aided manufacturing - happens either by milling or printing. With milling the crown is cut from a solid block of zirconia lithium disilicate composite or metal with rotating diamond burs guided by multiple axes simultaneously. With 3D printing the piece is instead built up layer by layer from a liquid photopolymer that hardens every time a layer is hit by light from a projector or laser. The two methods complement each other: milling is typically used for the final durable replacement while printing is often used for models splints temporary crowns and casting moulds.

For the dental technician the digital workflow does not mean the craft disappears — it shifts. Where hands previously shaped wax around a plaster model they now control a mouse and keyboard with the same demands for an eye for shape function and aesthetics. The best results still arise when solid material understanding and a trained eye meet digital precision.

“The software draws lines. It is still the dental technician who decides whether it becomes a tooth.”