TRANSLATIONAL AND CLINICAL MEDICINE - Georgian Medical Journal

Background. Zirconium dioxide is widely used in prosthetic dentistry due to its high strength, durability, and biocompatibility. However, its clinical performance may be compromised by fracture susceptibility under certain conditions. In addition, inconsistencies in fabrication protocols and processing recommendations contribute to variability in outcomes and limit standardized clinical application. Selection of appropriate zirconia for prosthodontic applications remains challenging for clinicians and dental technicians due to the lack of a universally accepted, clinically relevant classification system. Existing classifications, mainly based on composition or generation, provide limited guidance for everyday clinical decision-making.

Aim. The primary aim of this study is to develop a clinically relevant and practically applicable classification system for zirconium dioxide in prosthetic dentistry. This classification will be based on parameters directly linked to clinical decision-making, with the objective of providing clear guidance for material selection in specific indications. Furthermore, the study aims to support this classification through experimental evaluation, thereby enhancing the predictability, reliability, and long-term clinical success of zirconia-based prosthetic restorations.

Methods. A total of 80 pre-sintered Y-TZP specimens composed of synthesized zirconium dioxide  stabilized with yttria (Y₂O₃) were prepared for experimental evaluation. All samples were subjected to a three-point bending test to determine flexural strength.

Following mechanical testing, samples underwent macroscopic and microscopic examination to assess fracture patterns and surface characteristics. In the subsequent stage, detailed microstructural analysis was performed using scanning electron microscopy at magnifications of up to 1000×, enabling visualization of structural alterations induced by the applied mechanical stress. Additionally, phase composition and structural changes were evaluated through qualitative and quantitative X-ray diffraction analysis. All procedures complied with the requirements of ISO 6872:2008.

Results. Three-point bending tests showed variability in flexural strength among Y-TZP specimens, indicating a clear dependence on material processing and microstructural characteristics. SEM analysis confirmed differences in grain structure, porosity, and surface morphology, while XRD revealed variations in phase composition, including tetragonal–monoclinic transformation. These structural and phase differences were directly associated with mechanical performance.

Based on the experimental findings and comprehensive literature analysis, a clinically oriented classification system of zirconia (Y-TZP) was developed, integrating mechanical properties, structural characteristics, and indication-specific requirements. This classification is structured according to practical clinical criteria, including mechanical performance, indication-specific requirements, and processing-related factors.

Conclusions. The study demonstrates that zirconia performance is strongly influenced by its microstructure and phase composition, directly affecting clinical reliability. The proposed clinical classification of zirconia (Y-TZP) provides a practical framework for material selection based on functional and indication-related criteria. This classification may improve decision-making in prosthetic dentistry and support more predictable clinical outcomes in zirconia-based restorations.

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