Stress Distribution of Hybrid Ceramic Implant-supported Superstructure Versus Zirconia and Lithium Disilicate Superstructures

Introduction The choice of crown material for dental implants is critical, and polymer-infiltrated hybrid ceramics have been proposed to mitigate excessive stress. However, research on the stress distribution in these materials and their impact on supporting structures is limited. This study evaluated stress distribution across various CAD/CAM crown materials: multilayered zirconia, polymer-infiltrated hybrid ceramics, and lithium disilicate ceramics on maxillary premolar implants. Materials and Methods A three-dimensional finite-element model simulating a maxillary premolar implant was developed, featuring a 3.7 mm diameter, 13 mm length, and 5.5 mm abutment height, and was covered with a 50 μm cement layer. The model was subjected to compressive vertical and oblique loads, and three superstructure materials were tested. Results The study noted slight differences in deformation and stress distribution among materials under the same load conditions. Multilayered zirconia crowns exhibited the least deformation, followed by lithium disilicate crowns, whereas polymer-infiltrated hybrid ceramics showed the most significant deformation. Discussion The polymer-infiltrated hybrid ceramics exhibited higher susceptibility to deformation due to their resin content. Resilient materials reduce implant stress; implant failure is unlikely at von Mises stress levels below 550 MPa. Oblique loading intensified stress and deformation across all structures, corroborating previous findings about risks to prosthetic parts and surrounding tissues. While cortical bone experienced higher stress than spongy bone, it did not exceed strength limits, particularly at the implant-abutment neck. Conclusions Stress and deformation increased progressively across all materials, with oblique loads producing greater stress than vertical loads. The bone and mucosa showed minimal response to the crown materials.