Biomechanical Effects of Digitally Designed Titanium, Modified PEEK, and PEKK Subperiosteal Implants in the Atrophic Maxilla: A Finite Element Analysis

Mohammed A. El-Sawy, Basin El-Khatib, Hesham S. Borg, Mohamed T. Khater.

Full text link: https://pubmed.ncbi.nlm.nih.gov/40640731/ 

Biomechanical Effects of Digitally Designed Titanium, Modified PEEK, and PEKK Subperiosteal Implants in the Atrophic Maxilla: A Finite Element Analysis

1. Scientific Reference

• Study Title: Biomechanical effects of digitally constructed titanium, modified polyetheretherketone, and polyetherketoneketone subperiosteal implants on atrophied maxilla: a finite element analysis.
• Authors: Mohammed A. El-Sawy, Basin El-Khatib, Hesham S. Borg, Mohamed T. Khater.
• Journal: BMC Oral Health
• Publication Year: 2025.
• DOI: 10.1186/s12903-025-06426-z.

2. Scientific Background

Managing severe maxillary atrophy remains one of the most demanding challenges in implant dentistry. Conventional endosseous implants often require sufficient bone volume, making advanced bone augmentation procedures, sinus floor elevation, zygomatic implants, or other reconstructive techniques necessary before rehabilitation can be achieved. While these approaches have expanded treatment possibilities, they frequently involve extensive surgery, increased morbidity, prolonged healing periods, and multiple clinical stages.

Recent advances in digital implant planning, CAD/CAM manufacturing, and additive manufacturing have renewed clinical interest in patient-specific subperiosteal implants. Unlike earlier generations, digitally designed frameworks can be precisely adapted to individual anatomical conditions, offering a potential solution for patients with severe maxillary resorption who may not be suitable candidates for conventional implant therapy.

Within this evolving treatment concept, selecting the most appropriate framework material has become an important biomechanical consideration. Titanium remains the benchmark because of its well-established mechanical properties, whereas high-performance polymers such as modified PEEK (BioHPP) and PEKK have emerged as promising alternatives owing to their lower elastic modulus and favorable material characteristics. This study investigates how these materials influence stress transmission within the atrophic maxilla under simulated functional loading.

3. Study Objective

The purpose of this investigation was to evaluate the biomechanical influence of different material combinations used for both the subperiosteal framework and the prosthetic superstructure in patients presenting with an atrophic maxilla.

Using finite element analysis, the authors compared titanium, modified PEEK, and PEKK across nine framework combinations to determine how each configuration affected stress distribution within the supporting bone, fixation screws, cement layer, and prosthetic components under clinically relevant loading conditions.

4. Methodology

This research is a preclinical finite element analysis (FEA) designed to evaluate the biomechanical behavior of customized subperiosteal implant systems. A three-dimensional digital model of an atrophic maxilla was generated from computed tomography (CT) data and processed through a fully digital CAD workflow before mechanical simulations were performed using ANSYS software. The computational model was validated by comparison with previously published finite element studies.

The customized subperiosteal framework was stabilized using twelve titanium mini-screws measuring 2 mm in diameter, with lengths of 5, 7, and 9 mm selected according to anatomical constraints. Three framework materials—titanium, modified PEEK (BioHPP), and PEKK—were assigned to both the subperiosteal implant and the prosthetic framework, producing nine different material combinations for biomechanical comparison.

Three loading protocols were simulated to reproduce clinically relevant occlusal conditions:

• bilateral posterior vertical loading of 200 N;
• bilateral posterior oblique loading of 100 N applied at 30°;
• anterior vertical loading of 150 N distributed across the incisors.

Mechanical performance was assessed by analyzing von Mises stress, principal stress, and displacement throughout the implant system and surrounding bone.

5. Main Findings

The finite element simulations revealed clear biomechanical differences among the three framework materials evaluated. Across all loading scenarios, titanium subperiosteal frameworks consistently generated the lowest stress levels within the supporting bone and fixation screws, demonstrating the most favorable load transfer characteristics. This advantage became particularly evident under anterior loading, which produced the highest mechanical demands throughout the implant system.

Bone stress values remained lowest when titanium was used as the subperiosteal framework material. Modified PEEK produced the highest stress concentrations within the surrounding bone, while PEKK demonstrated an intermediate mechanical response. Under vertical incisor loading, titanium was the only material that maintained bone stresses below the physiological threshold discussed by the authors, whereas both polymer-based frameworks generated substantially higher stress values.

A similar pattern was observed at the cement interface. Titanium frameworks resulted in lower stress concentrations under both posterior and anterior loading conditions, whereas modified PEEK produced the highest stresses. The authors noted that anterior loading generated the most critical conditions for the cement layer, suggesting an increased theoretical risk of prosthetic debonding when more flexible framework materials are used.

Interestingly, titanium exhibited the highest internal stresses within the prosthetic framework itself. Rather than representing a disadvantage, this reflects the material’s greater stiffness, allowing more of the applied load to be absorbed by the framework while reducing stress transmission to the supporting biological structures. In contrast, modified PEEK and PEKK absorbed mechanical energy more readily but distributed occlusal forces less efficiently throughout the implant complex.

Stress levels recorded in the titanium fixation screws remained within safe mechanical limits under all simulated loading protocols. Although screw stresses increased when polymer-based subperiosteal frameworks were used—particularly during anterior loading—they also remained below the reported safety limits for titanium mini-screws. Overall deformation remained within physiological limits for every simulated configuration, indicating that none of the tested designs experienced catastrophic structural failure under the applied loads.

6. Clinical Analysis

This study provides valuable biomechanical insight into one of the emerging areas of modern implant dentistry: the interaction between framework materials in digitally manufactured subperiosteal implant systems. Rather than evaluating an isolated implant component, the investigators analyzed the combined influence of both the subperiosteal framework and the prosthetic superstructure, offering a more comprehensive understanding of how material selection may affect the mechanical behavior of the entire rehabilitation.

The findings suggest that material stiffness remains a critical determinant of biomechanical performance in customized subperiosteal implants. Titanium demonstrated superior structural stability by concentrating stresses within the framework itself while limiting force transmission to the surrounding bone, fixation screws, and cement layer. From a biomechanical perspective, this represents a favorable load-sharing mechanism because protecting biological tissues is generally more important than minimizing internal stresses within a metallic framework that possesses a substantially higher mechanical strength.

Modified PEEK and PEKK exhibited a different mechanical behavior. Their lower elastic modulus enabled greater deformation and increased energy absorption, characteristics that may appear advantageous at first glance. However, the simulations demonstrated that this increased flexibility also resulted in higher stress transfer to supporting structures, particularly during anterior loading conditions where bending forces were greatest. These findings indicate that polymer-based frameworks should not be viewed simply as lower-stiffness alternatives to titanium but rather as materials whose clinical performance is likely to depend on the functional environment in which they are used.

The authors also emphasize that these conclusions should be interpreted within the limitations of computational modeling. Finite element analysis provides valuable information regarding stress distribution but cannot reproduce biological adaptation, osseous remodeling, patient-specific variability, parafunctional activity, or long-term fatigue behavior under clinical conditions. Consequently, while the study offers meaningful guidance for material selection during digital treatment planning, it should not be interpreted as definitive clinical evidence regarding implant survival or long-term prosthetic success.

7. Clinical Applications

The findings of this investigation may assist clinicians involved in the digital planning of customized subperiosteal implant rehabilitation for patients with severe maxillary atrophy. Based on the biomechanical simulations, titanium appears to remain the preferred framework material when high occlusal loads, full-arch restorations, or opposing natural dentition are anticipated, owing to its superior ability to reduce stress transmission to supporting tissues.

PEKK and modified PEEK may represent reasonable alternatives in selected clinical situations characterized by lower functional loading. According to the authors, these materials could be considered in patients with reduced bite forces, complete dentures in the opposing arch, or anterior restorations where mechanical demands are less pronounced. However, these potential applications should be interpreted cautiously because they are derived from computational simulations rather than prospective clinical investigations.

8. Level of Evidence, Limitations, and Transparency

This publication represents a preclinical finite element analysis (FEA) and should therefore be considered as biomechanical research rather than clinical evidence. Finite element modeling is a well-established engineering method for investigating stress distribution within implant-supported restorations, but it cannot directly predict clinical outcomes, implant survival, or long-term biological performance. Consequently, the findings should be interpreted as theoretical mechanical evidence that may guide future research and material selection rather than establish definitive clinical recommendations.

The authors acknowledge several methodological limitations. The computational model was developed from the anatomy of a single atrophic maxilla, which limits the generalizability of the findings to the broader patient population. Furthermore, all materials were modeled as isotropic, homogeneous, and linearly elastic, simplifying the complex mechanical behavior of cortical bone as well as polymer-based materials such as modified PEEK and PEKK. The simulations also evaluated only static loading conditions and did not incorporate fatigue, creep, biological remodeling, or long-term degradation, all of which may influence clinical performance over time. In addition, the absence of experimental validation means that the numerical predictions should be confirmed through laboratory testing and prospective clinical studies.

Regarding transparency, the authors declared no competing interests. Open-access publication was supported by the Science, Technology & Innovation Funding Authority (STDF) in collaboration with the Egyptian Knowledge Bank (EKB). The authors further state that the research itself did not receive any specific grant from public, commercial, or non-profit funding agencies.

9. Key Study Highlights

• Study Design: Preclinical finite element analysis (FEA).
• Level of Evidence: Preclinical computational study.
• Study Model: Three-dimensional CT-derived model of an atrophic maxilla.
• Number of Patients: One anatomical model used for simulation.
• Number of Implant Configurations: Nine material combinations involving titanium, modified PEEK, and PEKK.
• Follow-up Period: Not applicable.
• Primary Outcome: Stress distribution within bone, fixation screws, cement layer, prosthetic framework, and subperiosteal framework under three simulated loading protocols.
• Principal Finding: Titanium subperiosteal frameworks consistently generated the most favorable biomechanical behavior by minimizing stress transfer to supporting bone and fixation components.
• Scientific Conclusion: Titanium demonstrated superior biomechanical performance under the simulated conditions, whereas PEKK and modified PEEK may represent alternative materials in carefully selected low-load clinical situations.
• Main Limitations: Single-anatomy computational model, simplified material assumptions, static loading conditions, and lack of experimental or clinical validation.

10. Scientific Impact

This investigation contributes meaningful biomechanical evidence to the growing body of literature on digitally customized subperiosteal implants. While previous finite element studies have primarily evaluated individual framework materials or isolated implant components, this work expands current knowledge by examining how the combined selection of subperiosteal framework and prosthetic superstructure materials influences the mechanical behavior of the entire rehabilitation system.

The results reinforce titanium’s position as the current reference material for customized subperiosteal implant frameworks, particularly in situations involving high functional loading. At the same time, the study provides valuable insight into the mechanical behavior of emerging high-performance polymers such as modified PEEK and PEKK. Rather than presenting these materials as direct substitutes for titanium, the findings suggest that their biomechanical performance is highly dependent on functional loading conditions and prosthetic design. This distinction may help clinicians adopt a more individualized approach to material selection during digital implant planning.

Equally important, the study identifies several areas requiring further investigation. The authors recommend future laboratory validation, fatigue testing, biological assessment, and prospective clinical studies to determine whether the biomechanical advantages observed through finite element modeling translate into improved long-term clinical outcomes. As digital workflows continue to transform implant dentistry, such multidisciplinary research will be essential for optimizing patient-specific treatment strategies.

11. Editorial Conclusion

This finite element analysis provides a comprehensive biomechanical comparison of titanium, modified PEEK, and PEKK for digitally designed subperiosteal implant rehabilitation in the atrophic maxilla. Within the limitations of computational modeling, titanium demonstrated the most favorable mechanical performance by reducing stress transmission to supporting bone and fixation components while maintaining structural stability. Although modified PEEK and PEKK may offer potential advantages in carefully selected low-load clinical situations, additional experimental and clinical evidence is required before their broader application can be fully supported. Overall, this study represents a valuable contribution to the ongoing evolution of digitally customized implant rehabilitation and highlights the importance of material selection in optimizing biomechanical performance.