Manufacturing technology 3D lithium I
mitating natural aesthetics poses a permanent challenge for dentistry. Silicate ceramics have been the top material for more than 100 years when it comes to replacing lost tooth substance with restorations that look as natural as possible. Charles Henry Lund, a US dentist, first invented an all-ceramic crown restoration made of silicate ceramics as early as 1900. However, the technical application was very complicated with many problems. The main advantage of silicate ceramics is their tooth-like appearance – achieved via a refraction index very close to that of dentin and enamel.
At the beginning of the 1990s, Arnold
Wohlwend developed the process for fabricating pressed ceramics. This was then introduced to the market by Ivoclar under the product name IPS Empress. The technology has been continuously developed over the past 30 years, perfecting both the materials and the pressing technologies. For more than 15 years, lithium disilicate has also been available as grindable blocks for subtractive machining using CAD/CAM processes.
High-precision ceramic 3D printing technologies, such as Lithoz’s LCM process, are the ideal manufacturing methods to make 3D tooth layering a reality.
process. After debinding and crystallisation, the crowns were finished with a stain and glaze firing. The three-dimensional acquisition of the master model and opposing jaw model was carried out with a laboratory strip white light scanner. Subsequently, five fully anatomical crowns (crown 33, 37 on natural abutment, crown 34, 35, 36 on implant abutments) were designed using dental CAD software Modellier.
“The main advantage of silicate ceramics is their tooth-like appearance – achieved via a refraction index very close to that of dentin and enamel.
At IDS 2021, Lithoz – global market leader in ceramic 3D printing – achieved a true technological milestone, using their renowned LCM technology for the additive manufacturing of crowns made of lithium disilicate. The current state-of-the-art in the dental 3D printing of lithium disilicate is presented based on five mandibular crowns. After a classical analogue impression with the fabrication of a master model made of plaster, the CAD design took place followed by fabrication using Lithoz’s LCM
56 3D printing the crown
When printing the CAD models, support structures were generated to facilitate the connection of the restoration’s freeform surface to the building platform of the 3D printer. The data was then loaded into a CeraFab S65 Medical 3D printer, where suitable printing parameters were selected. Low translucency lithium disilicate slurry in the colour A3 was used as the raw material for manufacturing the crowns. The print run took 3.1 hours for all five crowns. After the
printing process, the parts were in their green state. These “green bodies” consisted of a crosslinked organic binder system and lithium disilicate particles, which were dispersed within the formulation. Any excess uncured slurry was removed during cleaning before the parts were taken for debinding and crystallisation. To finalise the crown restorations, a stain and glaze firing was conducted. The firing was conducted at a temperature of 710°C. In the case shown, IPS Ivocolor stains were used.
Assessment of the final result A classic lithium disilicate material was used for the additive fabrication of five crowns using Lithoz’s LCM technology. The fit on the natural abutments and implant abutments were good, while the translucency and overall aesthetics were very good, achieving excellent standards. Particularly striking were the perfect and exact reproduction of the sharp-edged crown margins and occlusal surfaces with their natural representation of the fissures. Since crown margin reinforcement is always necessary with
Medical Device Developments /
www.nsmedicaldevices.com
disilicate printing
High-precision ceramic 3D printing technologies, such as Lithoz’s LCM process, are the ideal methods for producing durable and convincing dental prostheses and replacement teeth. ZT Josef Schweiger, from the department of prosthodontics at LMU Klinikum Munich, explains more.
Josef Schweiger
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