Should I mill or should I print? Or should I do both? Three aspects to consider in the decision-making process

Expertise meets technique

Digitalization has been impacting on dental laboratories for some years now. Alongside subtractive manufacturing such as milling, additive processes, or 3D printing, have found their way into the laboratory. In spite of these developments, specialist knowledge and detailed planning continue to be key requirements for achieving accurately fitting high-quality restorations. Still, the advantages of digital manufacturing cannot be denied, regardless of whether milling or 3D printing processes are used. Two of the main advantages are: a) ability to create objects with exceptionally high precision and b) excellent reproducibility based on digital data files. Today, the workflow in the laboratory can be mapped out almost completely in digital steps: from receiving the intraoral scan data to designing and printing or milling the final product. As many analogue working steps can be replaced, or at least expedited, with digital technology, there is more time to focus on design and esthetics. This approach leads to accurately fitting results achieved in a time efficient manner. Materials specifically designed for dental applications are tailored to the needs of dental laboratories in terms of precision, esthetics and strength. They ensure the reliability of the process and enhance the quality of the workpieces produced in the laboratory. Which process is best suited for a particular case? There are some basic considerations that come into play when deciding on a process.

Interfacing with existing processes

Using digital technology usually leads to an increase in the range of applications and the product portfolio while familiar procedures can stay in place, including the processing of digital data. Since as of yet not all manual working steps can be implemented using digital technology, digital procedures are often employed to complement and enhance the “classic way of doing things”. 3D printing is a good example of this. 3D printing can be integrated into the existing workflow to streamline it and digitalize a large chunk of the fabrication process. For instance, just think what you can do when you combine digital manufacturing with the press technology to create ceramic restorations: The 3D printer produces the wax patterns in burnout material, which, after the burnout process, can be pressed in the usual manner. 3D printers can be easily integrated into the existing laboratory settings without much technical effort. By contrast, the acquisition of a milling machine will have greater consequences on the day-to-day routines of a laboratory. If a dental mill is used for producing restorations, virtually all analogue steps will be replaced by a digital process. Unlike a 3D printer, a mill does not assist the workflow but basically determines the fabrication method. Once purchased, the milling machine will serve to produce a large share of the restorations to keep capacity utilization high and thus ensure profitability.

Up to 85 per cent of the material is lost in the milling process.

Material selection and field of application

The more materials are processed in the laboratory and the more areas of application are covered, the higher the utilization of the mill and thus its profitability. The milling process is suitable for almost any material you want, starting from glass ceramics such as IPS e.max CAD to zirconia including IPS e.max ZirCAD. Even dental alloys, e.g. Colado CAD CoCr4, can processed in a mill. 3D printers also cover a wide range of applications - from models to drilling templates, splints, crowns and bridges. In all cases, printers produce process-supporting pieces. The layered structure of the printed objects makes it possible to implement virtually any geometrical configuration conceivable - even in situations where space is limited. By contrast, milling machines are often limited in this respect because of the limited flexibility of the tools they use. However, there are things that a 3D printer cannot do yet: printers cannot yet cover the same broad spectrum of materials as do milling machines. Nonetheless, there are overlaps in the range of materials that these two technologies offer. For instance, drilling templates or wax patterns can be produced with both of them.

Let’s talk about resources

Up to 85 per cent of the material is lost in the milling process. By contrast, 3D printing only uses the material that is actually needed - to build the workpiece itself and the support structure required for the building process. The light-curing resins are applied layer by layer and cured with light. This way, the design data can be used to produce the particular workpiece using a minimal amount of resource material. Depending on the size of the build platform, several workpieces of the same material can be printed simultaneously per print job. Material usage is manageable, and the acquisition costs for 3D printers are comparatively low. In addition, printers do not incur costs for the regular maintenance and replacement of tools, unlike milling machines. The light-curing auxiliaries can be printed quickly, cost effectively and accurately without a model. In contrast, milling machines can only process one job per run. Only a few restorations can be milled from a material block or disc before they have to be replaced. It needs to be mentioned, however, that many mills are equipped with a built-in material and tool changer for automatic changes so that several jobs involving different types of materials can be processed in sequence without manual involvement on the part of the operator.

Conclusion: Individual factors are decisive

Ultimately, the question of how far you should go to digitalize your laboratory is a matter of interfacing dental technical knowledge with digital technologies. Both the milling procedure and 3D printing come with their own unique advantages. If a laboratory knows how to use these technologies to its best advantage, new possibilities in the design and production of restorations will emerge. Laboratories can increase their efficiency and put themselves in an even better position to meet the demands of patients for affordable, esthetic and functional tooth replacements.

So, you may wonder which path to digitalization is best for you. The answer depends on your individual circumstances:

• What is the focus of production in your laboratory?
• Are you already using some digital technology?
• Are you looking towards optimizing the manufacturing methods and processes you are currently using or do you want to replace them and go completely digital?
• Do you produce a large number of models, drilling templates and splints?
• Do you do a lot of jobs that require the use of lithium disilicate or zirconium oxide?
  
  Given the comprehensive selection of material and the correspondingly wide range of applications, milling technology often dominates the considerations. As the number of jobs implemented with the milling machine keeps growing, machine utilization increases and profitability improves. 3D printing, on the other hand, offers a high level of efficiency and a fast route to profitability, not least due to the fact that several workpieces can be printed simultaneously. If you want to digitalize the press technique or produce splints and drilling templates using an efficient method, using a 3D printer offers advantages. However, the choice of materials is significantly less varied at the present. Combining both manufacturing technologies is also an option worth considering. If a mill is already in use, the scope of production and the added value for the laboratory can be increased by the additional use of a 3D printer. While the milling machine produces the crowns, inlays or bridges using ceramics or metal alloys and thus specifically processes those jobs that account for a large share of the laboratories value creation, the 3D printer can cover the need for all additional process-supporting workpieces. The result: The laboratory benefits from a faster, easier and more reliable workflow.