Gingival Soft Tissue Integrative Zirconia Abutments with High Fracture Toughness and Low-Temperature Degradation Resistance

Low fracture toughness, low-temperature degradation (LTD) susceptibility, and inadequate soft tissue integration greatly limit the application of zirconia ceramic abutment. Integrating the "surface" of hard all-ceramic materials into the gingival soft tissue and simultaneously promoting the "inner" LTD resistance and fracture toughness is challenging. Composite ceramics are effective in improving the comprehensive properties of materials. In this study, we aim to develop a zirconia composite abutment with high "inner" structure stability and "surface" bioactivities simultaneously and to explore the mechanism of performance improvement. Therefore, elongated SrAl₁₂O₁₉ and equiaxed Al₂O₃ were introduced into the zirconia matrix by using the Pechini method. Reinforcements of different shapes can promote the density, reduce the grain size, and increase the phase stability of composite ceramics, which improves the fracture toughness and LTD susceptibility. In addition, the released strontium ions (Sr²⁺), without sacrificing the mechanical properties of the material, could activate the biological capacity of the zirconia surface by activating the M2 polarization of macrophages through the Sr²⁺/calcium-sensing receptor/SH3 domain-binding protein 5 axis, thereby promoting the collagen matrix synthesis of fibroblasts and the angiogenesis of vascular endothelial cells. This successful case proposes a novel strategy for the development of advanced high-strength and bioactive all-ceramic materials by introducing reinforcements containing biofunctional elements into the ceramic matrix. The approach paves the way for the widespread application of such all-ceramic materials in soft-tissue-related areas.