Milling & printing

3D Printing and Post-Processing

• Support materials include cutting, break away clean, oven, solution, and combination
• Types of 3D printing include Steriolithography (SLA), Photopolymer Jetting (PPJ), Powder Binder Printers (PBP), Selective Laser Sintering (SLS), and Fused Deposition Modelling (FDM)

Steriolithography (SLA)

• Uses a scanning laser to build parts one layer at a time in light-cured photopolymer resin vats
• Produces 3D printed implant drill guides

Photopolymer Jetting (PPJ)

• Uses light-cured resin materials and print heads to lay down layers of photopolymer
• Can print various materials, including resins, waxes, and silicone-like rubber
• Allows simultaneous printing of different materials and graduated mixtures of materials

Powder Binder Printers (PBP)

• Uses liquid droplets to infiltrate a layer of powder with new powder applied to each surface
• Produces models useful as study models, but accuracy is limited and post-processing makes them fragile

Selective Laser Sintering (SLS)

• Uses a scanning laser to fuse fine material powder to build up structures in layers
• Produces high-resolution models with no supporting material needed
• Uses polymers with high melting points and excellent material properties for study models, cutting and drilling guides, dental models, and engineering/design prototypes
• Can also use polyether ether ketone (PEEK), metals, and metal alloys for partial dentures and prosthetic frameworks, implant bridge frameworks

Fused Deposition Modelling (FDM)

• Early 3D printing technology
• Requires thermoplastic materials
• Materials are biodegradable polymers
• Requires support structures
• Produces study models

Computer-Aided Manufacturing (CAM) Processes

• Comparison of milling and 3D printing
• Milling is a subtractive manufacturing process, while 3D printing is an additive manufacturing process

History of CAD/CAM

• The first computer-aided design and computer-aided manufacturing (CAD/CAM) machine was created in the 1960s
• Dr. Francois Duret introduced CAD/CAM concepts into dental applications in 1973
• The first commercial CAD/CAM system for producing chair-side dental restorations was CEREC in 1987

Chair-Side Production Advantages

• Time-saving
• Low cost
• High level of predictability of outcomes

CAImaging CADesign CAMilling

• Automated optical scanner
• Lightweight table-top milling
• Customized CAD/CAM software machine
• Increases efficiency and productivity of dental laboratories

Dental 3D Imaging

• Desktop scanner and intraoral scanner
• Desktop scanner limitations include institutional constraints and inaccurate gap measurements
• Intraoral scanner limitations include accumulated discrepancy and multi-patch registration mistakes

Production Manufacturing

• Milling machining: computer numerical control (CNC) milling machines
• Subtractive manufacturing process
• Types of milling devices include 3-axis, 4-axis, and 5-axis devices

Milling Variants

• Dry processing: minimal investment costs, no moisture absorption, but higher shrinkage values
• Wet milling: necessary for metals and glass ceramic materials, avoids heat damage, and recommended for zirconium oxide ceramic with higher degree of pre-sintering

Laser Milling

• Advantages include no tool wear, fine laser beam diameter, high resolution, detail, and accuracy, easy to use, and no need for coolant
• Indicated for onlays, inlays, crowns, laminates, and short-span bridges
• Disadvantage: longer milling time than regular milling

3D Printing

• Introduced in 1984, but didn't take off until the 2000s
• Guided by computer-aided design (CAD) software
• Uses data from computed tomography (CT) images, cone-beam computed tomography (CBCT), or intraoral or laboratory optical surface scans
• Applications include precise virtual models, wax patterns, removable partial frameworks, provisional restorations, physical models of the scanned jaw, and implant abutments