Biomechanical Evaluation of Prosthetic Framework Materials in Subperiosteal Implants: A Finite Element Analysis

Büşranur Demir, Ipek Caglar

Full text link: https://pubmed.ncbi.nlm.nih.gov/41318436/

Biomechanical Evaluation of Prosthetic Framework Materials in Subperiosteal Implants: A Finite Element Analysis

1. Scientific Reference

• Study Title: Biomechanical Evaluation of Prosthetic Framework Materials in Subperiosteal Implants: A Finite Element Analysis
• Authors: Büşranur Demir, Ipek Caglar
• Journal: BMC Oral Health
• Year of Publication: 2025
• DOI: 10.1186/s12903-025-07391-3

2. Scientific Background

Managing patients with advanced maxillary atrophy remains one of the greatest challenges in implant dentistry. Conventional implant placement frequently requires bone augmentation procedures before rehabilitation can be achieved, increasing treatment complexity, surgical morbidity, and overall treatment time. In recent years, patient-specific subperiosteal implants have regained clinical interest owing to advances in digital workflows, including cone-beam computed tomography, CAD/CAM planning, and metal additive manufacturing. These technologies allow highly customized implants to be fabricated according to individual anatomical conditions.

Although implant design has evolved considerably, the biomechanical influence of prosthetic framework materials on modern subperiosteal implant systems remains insufficiently investigated. Most previous biomechanical studies have focused on endosseous implant restorations rather than custom-made subperiosteal devices. Understanding how different framework materials influence stress transfer throughout the prosthetic complex may contribute to improved treatment planning and mechanical reliability in full-arch implant rehabilitation.

3. Study Objective

The purpose of this investigation was to evaluate how prosthetic framework materials with different elastic moduli affect the biomechanical behavior of full-arch restorations supported by subperiosteal implants. Specifically, the authors compared stress distribution within cortical bone, trabecular bone, the implant body, fixation screws, prosthetic screws, and prosthetic frameworks using finite element analysis.

4. Methodology

This investigation was designed as a preclinical finite element analysis (FEA) using a three-dimensional digital model reconstructed from cone-beam computed tomography (CBCT) data obtained from a completely edentulous maxilla. The digital anatomy served as the basis for designing a patient-specific two-piece subperiosteal implant intended to support a full-arch fixed prosthesis. Ethical approval for the use of the imaging data was obtained before model development.

Four framework materials were evaluated: cobalt–chromium (CoCr), titanium (Ti), zirconia (Zr), and polyetheretherketone (PEEK). Five restorative configurations were subsequently generated by combining these frameworks with commonly used veneering materials: CoCr–porcelain, zirconia–porcelain, titanium–porcelain, titanium–acrylic resin, and PEEK–composite resin.

To simulate physiological mastication, the investigators simultaneously applied a 100 N vertical load in the anterior region together with 150 N vertical forces and 100 N oblique forces at a 30° angle in the posterior regions. Maximum principal stresses were calculated for cortical and trabecular bone, whereas von Mises stresses were assessed for the implant framework, fixation screws, prosthetic screws, and prosthetic framework. As this was a computational investigation, no additional patient cohort or clinical follow-up was included.

5. Main Findings

The finite element simulations demonstrated that prosthetic framework material substantially influenced stress transmission throughout the entire implant-supported reconstruction. Among all restorative designs, the PEEK–composite configuration generated the highest stress values within cortical bone, trabecular bone, the implant body, and both fixation and prosthetic screws. Conversely, the cobalt–chromium framework veneered with porcelain consistently produced the lowest stress levels across most evaluated structures.

Compared with the cobalt–chromium model, the PEEK–composite restoration increased cortical bone stress by approximately 14%, trabecular bone stress by 22%, and prosthetic screw stress by nearly 96%. In contrast, titanium frameworks veneered with either porcelain or acrylic resin exhibited very similar biomechanical behavior, suggesting that the veneering material itself had only a limited effect when the framework material remained unchanged.

The prosthetic screws experienced the greatest mechanical loading among all components, reaching a maximum von Mises stress of 233.05 MPa, whereas fixation screws showed substantially lower peak values, with a maximum of 71.45 MPa. Stress concentrations were predominantly located around prosthetic abutments, screw connections, and the canine and zygomatic fixation regions. Importantly, stress values calculated for both cortical and trabecular bone remained below the biological tolerance thresholds adopted by the investigators for all tested configurations.

6. Clinical Analysis

This study provides valuable biomechanical insight into a topic that has received comparatively little attention in implant dentistry: the influence of prosthetic framework materials on the mechanical performance of modern subperiosteal implant systems. Rather than demonstrating that more flexible materials necessarily improve load absorption, the simulations suggest the opposite trend. The framework with the lowest elastic modulus—PEEK combined with composite resin—generated the greatest stress concentrations within the supporting bone, implant body, and prosthetic screws. These findings indicate that increased flexibility at the framework level does not automatically translate into reduced loading of the implant complex.

In contrast, the cobalt–chromium framework consistently produced the lowest stress values in most implant components. Although the framework itself experienced higher internal stress than the more flexible materials, it appeared to distribute functional forces more efficiently throughout the prosthetic assembly. This observation highlights an important biomechanical principle: a rigid framework may protect surrounding components by absorbing and redistributing occlusal loads rather than transferring them directly to the implant–bone interface.

Another clinically relevant finding concerns the prosthetic screws. Across all tested models, these components experienced the highest von Mises stress values, exceeding those observed in the implant body and fixation screws. This suggests that mechanical complications affecting prosthetic screw stability may deserve particular attention when planning full-arch rehabilitations supported by subperiosteal implants. The authors therefore emphasize that successful treatment planning should consider not only framework selection but also the mechanical resilience of the screw-retained connection.

The comparison between titanium frameworks veneered with porcelain and those veneered with acrylic resin also provides an interesting perspective. Despite the markedly different elastic properties of the veneering materials, both restorative designs produced nearly identical stress distributions. This finding suggests that, within layered prosthetic restorations, the framework material exerts a much greater influence on overall biomechanical behavior than the veneering material itself.

Finally, it is important to interpret these findings within the context of computational modeling. Finite element analysis offers a highly controlled environment for comparing mechanical performance but cannot replicate biological healing, bone remodeling, patient-specific variability, or long-term clinical function. Consequently, while the study strengthens the biomechanical rationale for framework material selection in digitally designed subperiosteal implants, its conclusions should be viewed as theoretical evidence requiring validation through prospective clinical investigations.

7. Clinical Applications

The findings of this investigation may assist clinicians involved in the digital planning of full-arch rehabilitations using patient-specific subperiosteal implants, particularly in patients presenting with severe maxillary atrophy where conventional implant placement and extensive bone grafting are less desirable or not feasible. The results suggest that framework material selection should be considered an integral part of prosthetic design rather than solely an esthetic or manufacturing decision.

The study also highlights the importance of evaluating the mechanical behavior of screw-retained prosthetic components during CAD/CAM treatment planning. Since prosthetic screws exhibited the highest stress concentrations in every configuration, clinicians and designers may benefit from paying particular attention to connection design and component durability when developing customized implant-supported restorations. Nevertheless, these applications should be interpreted cautiously, as the conclusions are based on computational simulations rather than clinical outcome studies.

8. Level of Evidence, Limitations, and Transparency

This publication is a preclinical finite element analysis (FEA) and therefore represents experimental biomechanical research rather than clinical evidence. While finite element modeling is a well-established method for comparing the mechanical performance of implant-supported restorations under standardized loading conditions, its conclusions remain theoretical and cannot directly predict long-term clinical outcomes or treatment success.

The authors acknowledge several methodological limitations inherent to the computational design. Bone tissues were modeled as homogeneous, isotropic, and linearly elastic materials, which simplifies the complex biological variability encountered in clinical practice. Gingival soft tissues were intentionally excluded from the model because the primary objective was to evaluate stress distribution within bone and implant components. In addition, screw threads were simplified to reduce computational complexity, and biological processes such as bone remodeling, healing, fibrointegration, and material aging could not be reproduced within the simulation. The authors therefore emphasize that further clinical investigations are required before these biomechanical observations can be translated into definitive therapeutic recommendations.

Based on the information available in the article excerpts, no conflicts of interest or commercial affiliations with implant manufacturers are specifically reported. Likewise, no industry sponsorship influencing the study design is identified within the provided material.

9. Key Study Highlights

• Study type: Preclinical three-dimensional finite element analysis (FEA).
• Level of evidence: Experimental biomechanical study (preclinical).
• Study model: One digital model of a completely edentulous maxilla reconstructed from CBCT imaging.
• Number of patients: One CBCT dataset used for digital reconstruction.
• Implant design: Patient-specific two-piece subperiosteal implant.
• Clinical follow-up: Not applicable.
• Primary outcome: Stress distribution within cortical bone, trabecular bone, implant body, prosthetic framework, fixation screws, and prosthetic screws.
• Framework materials evaluated: Cobalt–chromium, titanium, zirconia, and PEEK combined with different veneering materials.
• Main finding: The PEEK–composite restoration generated the highest stresses throughout most implant components, whereas the cobalt–chromium framework produced the lowest overall stress values.
• Scientific conclusion: Framework material significantly influences biomechanical behavior in subperiosteal implant-supported restorations, and prosthetic screw mechanics should be considered during treatment planning.
• Principal limitation: Results are derived from computational simulations and require validation through clinical studies.

10. Scientific Impact

This investigation contributes meaningful biomechanical evidence to a relatively underexplored area of implant dentistry. While numerous finite element studies have examined conventional endosseous implants, comparatively few have investigated the mechanical behavior of customized subperiosteal implant systems fabricated through contemporary digital workflows. By directly comparing multiple prosthetic framework materials within an identical anatomical model, the study expands current knowledge regarding the relationship between framework stiffness and stress transfer across implant-supported full-arch rehabilitations.

Beyond material comparison alone, the research highlights the importance of evaluating the complete restorative complex. The observation that prosthetic screws consistently experienced the highest stress concentrations suggests that mechanical reliability depends not only on implant design but also on the integrity of prosthetic connection components. This broader perspective may encourage future investigations to examine implant frameworks and prosthetic hardware as interconnected elements rather than isolated structures.

Although the study does not establish clinical superiority for any specific material, it provides a robust biomechanical foundation that may guide future laboratory investigations and prospective clinical trials evaluating patient-specific subperiosteal implant rehabilitations.

11. Editorial Conclusion

This finite element analysis demonstrates that prosthetic framework material plays a significant role in the biomechanical behavior of full-arch restorations supported by customized subperiosteal implants. Among the evaluated configurations, cobalt–chromium frameworks showed the most favorable overall stress distribution, whereas PEEK-based restorations generated higher stress concentrations within bone, implants, and prosthetic screws. While these findings improve the biomechanical understanding of digitally designed subperiosteal implant systems, they should be interpreted within the limitations of computational modeling. Prospective clinical studies remain essential to determine whether these mechanical differences translate into meaningful long-term clinical outcomes.