Patient-specific Finite Element Analysis of Immediate Loading in the Edentulous Maxilla: Comparison of Three Implant Configurations Using Digital Twins.

Rehabilitation of severely atrophic edentulous maxillae with dental implants pose a significant clinical challenge. Immediate loading in grafted bone is often debated due to concerns about stress distribution and osseointegration. This study aimed to compare stress distribution in the maxilla using three full-arch implant configurations-all-on-four, all-on-six, and quad-zygomatic implants-in a single patient, to determine the safest and most favorable approach for immediate loading in grafted bone. Two CBCT scans from a 64-year-old female patient, before and after bone grafting (allograft with onlay grafting and sinus augmentation), were used to generate three patient-specific finite element models. Each model included the maxilla, implants in the respective configuration, abutments, and a full-arch prosthesis. Von Mises stresses in cortical and cancellous bone, implants, abutments, and prosthesis, as well as maximum bone displacement, were analyzed. Our results demonstrated that the all-on-six configuration provided the most favorable biomechanical outcome, with homogeneous cortical stress distribution, reduced stress in implants and prosthesis, and bone displacement fully compatible with immediate loading in grafted bone. The all-on-four model showed stress peaks at tilted abutments and cantilevers, whereas the quad-zygomatic model distributed implant and abutment stresses efficiently but induced higher cortical bone stresses, still within physiological limits.This patient-specific digital twin study demonstrates that immediate loading in full-arch grafted bone is biomechanically safe and optimal, with the all-on-six configuration providing superior stress distribution. These findings support clinical decision-making for immediate loading protocols and highlight the value of patient-specific FEA in planning complex maxillary rehabilitations.