3D printing ceramics: LSD printing for silicate ceramics

3D printing of ceramics? For a long time, this was considered almost impossible for dental restorations. Now, LSD printing is delivering promising results: In the future, silicate ceramics could be printed not only by milling or pressing, but also layer by layer.

Silicate ceramics have established themselves in dentistry thanks to their combination of aesthetics, biocompatibility, and durability. Currently, corresponding restorations are predominantly fabricated using subtractive processes. While 3D printing has long been commonplace in other areas of dentistry, no method has yet established itself for ceramic restorations. The main reasons are the limited material selection, often limited mechanical properties compared to subtractive references, and sometimes long processing times.

3D printing ceramics with LSD printing

With the layered Slip deposition With LSD printing, a technology is now coming into focus that appears to be suitable for overcoming these hurdles. This slurry-based variant of binder jetting was developed specifically for ceramic materials. A water-based slurry (feedstock) is applied layer by layer with a squeegee, dried, and then locally solidified by a liquid polymer phase.

In this way, LSD printing opens up the possibility of not only producing ceramic restorations additively, but also of integrating them more efficiently and flexibly into everyday laboratory and practice routines in the future.

Critical process steps: feedstock, debinding and firing

In addition to the actual printing process, three factors are crucial for the quality of the final 3D-printed ceramic: 

• feedstock development
• debinding and
• the burning.

The feedstock must have an optimized rheology to ensure uniform layers form and the workpieces remain free of defects. Blistering, inadequate particle distribution, or delamination can be significantly influenced by the formulation and preparation of the slurry.

Controlled debinding is necessary to completely remove organic components without cracking or internal stresses. Rapid debinding cycles, in particular, require precise coordination of binder content, particle size, and heating profile. The subsequent firing process serves not only to densify but also to selectively crystallize the silicate ceramic.

material and methods

In the presented study, test specimens in different orientations (XY, XZ, YZ) were produced using the LSD printing process and debindered and fired in a combined process. Sawn test specimens from CAD/CAM blocks (VITABLOCS Mark II) served as references. Shrinkage in the X, Y, and Z directions, the microstructure (density, crystal content, porosity, defects), and key mechanical properties such as biaxial flexural strength, fracture toughness, Martens hardness, and indentation modulus were analyzed. Single-tooth crowns and veneers were fabricated for demonstration purposes and examined for dimensional accuracy and esthetic appearance (Figure 1).

Results: shrinkage, microstructure and mechanical properties

Conclusion

For everyday laboratory and practice use, this means: The LSD print is fundamentally capable of producing silicate ceramic restorations that meet minimum clinical requirements. In the tests, all test specimens met the standard values ​​according to DIN EN ISO 6872:2019-01 for Class 1a restorations – i.e., monolithic single-tooth crowns in the anterior region, veneers, inlays, or onlays with adhesive cementation.

Of particular note is the newly developed combined process of debinding and firing, which reduces the total process time to just 45 minutes. This represents a clear advantage over traditional process chains.

At the same time, there is still room for optimization regarding the degree of crystallization and dimensional stability. Nevertheless, the study clearly shows that 3D printing of ceramics using LSD printing has the potential to establish itself as a future-oriented additive alternative to subtractive manufacturing.