Evaluation and optimization of zirconia based dental restorations fabricated by use of additive manufacturing in vitro and in vivo

• Applicant: Professor Dr. Andreas Zenthöfer
• Subject Area: Dentistry, Oral Surgery
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524875261

Nowadays, all-ceramic dentures are of great importance in prosthetic dentistry. In particular, oxide ceramics such as zirconia are suitable for almost all prosthetic indications due to their high flexural strength of > 1000 MPa. This group of materials is processed for the fabrication of e.g. crowns or bridges in a CAD/CAM workflow, whereby the design created in the computer software (CAD) is almost exclusively converted into the definitive dental prosthesis by means of special milling units (CAM). This classic subtractive manufacturing strategy several disadvantages. On the one hand, the milling cutters cannot work out all object geometries due to their size and restrictions due to the axis alignment (so-called milling radius correction), and on the other hand, especially in the case of very delicate objects such as (occlusal) veneers, marginal splintering can occur due to so-called tooling stress. Finally, waste is produced in the form of the remnants of the blanks. For a few years now, devices have been available on the market that enable additive manufacturing, i.e. 3D printing, of ceramic objects. Currently, a 3D ceramic printer with clinical approval has been presented. Ceramic printing could be a milestone in prosthetic dentistry. One example is the possibility of earlier, faster, and less invasive rehabilitation of chewing function and aesthetics, and thus oral health-related quality of life, in children and adolescents in the form group of tooth or tooth structure malformations. The additive manufacturing process is interesting from a health economic point of view, as the manufacturing costs are halved compared to the milling approach. Initial studies on 3D ceramic printing also by the lead applicant are hopeful. However, there is still much need for preclinical optimization and clinical studies are also lacking. The project applied for here therefore has the following objectives: (1) Possible optimization approaches of the workflow in stereolithographic fabrication of different types of dental restorations, testing the influence of different sintering strategies including rapid sintering processes on the fit and microscopic structure of the final product as well as its reliability (preclinical) (2) Assessment of the wear of restorations and antagonistic teeth (preclinical) (3) Determination of the fracture load of 3D-printed occlusal veneers (posterior region) of different layer thicknesses (0.4 mm, 0.6 mm, 0.8 mm) and abutment tooth analogs of different stiffness (preclinical) (4) Clinical pilot study with n = 10 patients requiring a single crown in the posterior region, objectification of the clinical fit using crown duplicates, patient questionnaire to assess treatment comfort / quality of life, description of clinical performance and documentation of possible complications within the 1-year observation period

• DFG Programme: Research Grants