Marginal Bone Remodeling at Monolithic Zirconia Full-Arch Prostheses in the Maxilla and Mandible

Overview

This prospective observational clinical study aims to compare 12-month clinical, radiographic, and patient-reported outcomes of monolithic zirconia full-arch implant-supported prostheses placed in the maxilla versus the mandible. The study also investigates whether mandibular morphology (U-shaped vs V-shaped) and arch geometry (inter-implant distance and cantilever length) are associated with early marginal bone remodeling. All arches were rehabilitated following standardized surgical and digital prosthetic protocols.

This prospective observational cohort study investigates early marginal bone remodeling in full-arch implant-supported monolithic zirconia prostheses placed in the maxilla and mandible. Although monolithic zirconia has become a widely adopted restorative material due to its mechanical strength, esthetic stability, and reduced risk of veneering complications, limited evidence exists regarding whether early bone remodeling differs between the maxillary and mandibular arches or whether mandibular anatomical configurations influence these remodeling patterns. The present study was designed to address these knowledge gaps under rigorously standardized surgical and prosthetic conditions. All participants were fully edentulous and rehabilitated following identical clinical protocols. Each arch received between six and eight titanium implants placed through computer-guided surgery, followed by the connection of multi-unit abutments and the delivery of an immediate-loading PMMA provisional prosthesis within 48 hours. After a healing period of three months, definitive monolithic zirconia full-arch prostheses were fabricated and delivered using a fully digital workflow. Standardized periapical radiographs were obtained at baseline (prosthesis insertion) and at the 12-month follow-up using customized positioning devices, fixed exposure parameters, and a paralleling technique to ensure reproducibility. Radiographs were calibrated digitally using the known implant thread pitch, and marginal bone level changes were measured by two independent calibrated examiners. A key component of this study is the incorporation of mandibular anatomical variability into the analysis. Mandibular morphology was categorized into U-shaped and V-shaped configurations according to validated CBCT criteria based on intercanine-to-intermolar width ratios and anterior arch angles. Because mandibular flexure and strain distribution have been hypothesized to vary according to arch shape, the study evaluates whether these morphological classifications correspond to differences in early marginal bone remodeling. Additionally, geometric variables-including inter-implant distance and distal cantilever length-were extracted directly from the definitive CAD designs to assess potential associations between implant distribution and remodeling outcomes. The study also incorporates patient-reported outcomes to better understand the functional and psychosocial impact of treatment. The OHIP-14 questionnaire and a visual analog scale (VAS) for satisfaction were administered at baseline and at the 12-month recall appointment. Clinical parameters, prosthetic complications, and peri-implant soft-tissue conditions were documented to complement the radiographic evaluation. This design allows for multiple levels of comparison: * Arch-level comparison (maxilla vs mandible) under identical surgical/prosthetic protocols. * Morphology-specific analysis within the mandible (U-shaped vs V-shaped). * Geometry-based evaluation assessing correlations between implant positioning (inter-implant distance, cantilever length) and marginal bone remodeling. * Within-subject comparison for individuals rehabilitated in both arches. Because the study is observational and non-interventional, it does not assign treatments or modify clinical protocols. Instead, it seeks to characterize natural remodeling patterns under contemporary full-arch zirconia rehabilitation techniques and to explore whether anatomical and geometric factors contribute to variability in early outcomes. The broader goal of this research is to clarify whether certain mandibular anatomical configurations may benefit from modified implant distribution, segmented framework designs, or alternative prosthetic considerations. The findings have the potential to inform future guidelines in digital full-arch implant rehabilitation and help clinicians better anticipate patient-specific biomechanical challenges. Long-term follow-up and biomechanical measurements are encouraged for future studies to validate the associations observed in this 12-month analysis.