Comparison of Stress Distribution Among Standard Dental Implants Placed in Grafted Bone, Zygomatic Implants, and Subperiosteal Implants in the Atrophic Edentulous Maxilla: 3D Finite Element Analysis

Comparison of Stress Distribution Among Standard Dental Implants Placed in Grafted Bone, Zygomatic Implants, and Subperiosteal Implants in the Atrophic Edentulous Maxilla: A Three-Dimensional Finite Element Analysis

1. Scientific Reference

• Study Title: Comparison of Stress Distribution Among Standard Dental Implants Placed in Grafted Bone, Zygomatic Implants, and Subperiosteal Implants in the Atrophic Edentulous Maxilla: 3D Finite Element Analysis
• Authors: H. Gözde Keleş, Çiğdem Karaca
• Journal: The International Journal of Oral & Maxillofacial Implants
• Year of Publication: 2023
• DOI: 10.11607/jomi.9987

2. Scientific Background

The rehabilitation of severely atrophic edentulous maxillae remains one of the most demanding challenges in implant dentistry and oral and maxillofacial surgery. Extensive alveolar bone resorption combined with maxillary sinus pneumatization frequently limits the placement of conventional dental implants without prior bone reconstruction procedures.

Over the years, several treatment strategies have been developed to address these anatomical limitations. Autogenous bone grafting remains a well-established approach for creating sufficient bone volume, while zygomatic implants have emerged as an alternative for patients with severe posterior maxillary atrophy. More recently, advances in digital design and manufacturing technologies have renewed interest in patient-specific subperiosteal implants fabricated from titanium or polyether ether ketone (PEEK).

Although these approaches have individually demonstrated promising clinical outcomes, direct clinical comparisons remain difficult. Understanding how each treatment modality distributes functional loads is therefore important for improving long-term implant-supported prosthetic rehabilitation and reducing biological or mechanical complications.

3. Study Objective

The primary objective of this investigation was to compare the biomechanical behavior of four different surgical treatment concepts used for fixed implant-supported rehabilitation of the atrophic edentulous maxilla.

The authors aimed to evaluate stress distribution within bone tissue, implants, abutments, and prosthetic frameworks under functional loading conditions in order to better understand the biomechanical advantages and limitations associated with each treatment option.

4. Methodology

This research was conducted as a three-dimensional finite element analysis (3D FEA) study, representing a preclinical computational investigation.

A virtual model of an atrophic edentulous maxilla was generated from computed tomography data. Four treatment scenarios were simulated:

• Reconstruction with an anterior iliac crest onlay graft combined with bilateral sinus augmentation and conventional implants.
• Reconstruction with a mandibular ramus graft in the anterior maxilla combined with posterior zygomatic implants.
• Custom two-piece titanium subperiosteal implants.
• Custom two-piece PEEK subperiosteal implants.

All models received identical loading conditions consisting of a 150-N vertical force and a 50-N lateral force. Stress accumulation within cortical bone, trabecular bone, implants, abutments, and prosthetic frameworks was assessed using finite element analysis software. No human patient outcomes or clinical follow-up data were included because this was a virtual biomechanical study.

5. Main Findings

The study demonstrated distinct biomechanical behaviors across the four treatment models.

The iliac crest graft model generated the highest tensile stress values in both cortical and trabecular bone under vertical loading. This same model also produced the highest von Mises stress values within the implants themselves, suggesting greater mechanical demand on the implant system.

The PEEK subperiosteal implant model exhibited the highest compressive stress levels within both cortical and trabecular bone. According to the authors, compressive stress within trabecular bone exceeded the accepted strength threshold for this tissue.

Titanium subperiosteal implants generated the highest stress values within the abutments and prosthetic framework. Under both vertical and lateral loading conditions, the prosthetic superstructure associated with titanium subperiosteal implants experienced substantially greater stress accumulation than the other treatment configurations.

Overall, none of the four treatment concepts demonstrated consistently superior biomechanical performance across all evaluated structures.

6. Clinical Analysis

One of the most relevant messages emerging from this study is that the treatment of severe maxillary atrophy cannot be reduced to a single universally optimal solution. Each rehabilitation strategy appears to shift biomechanical stresses toward different components of the restorative system.

The iliac graft approach may facilitate placement of conventional dental implants but appears to concentrate higher tensile stresses within both bone and implants. This finding may be related to the mechanical characteristics of iliac bone compared with denser graft sources such as the mandibular ramus.

The zygomatic implant configuration showed favorable stress distribution within certain bone regions but demonstrated increased implant-related stress under lateral loading. Clinically, this observation highlights the importance of prosthetic design and occlusal management when zygomatic implants are used for full-arch rehabilitation.

The comparison between titanium and PEEK subperiosteal implants is particularly noteworthy. The lower stress observed within PEEK implants themselves suggests efficient load transfer; however, this benefit may come at the expense of increased stress transmission to surrounding bone. Conversely, titanium subperiosteal implants concentrated more stress within the prosthetic and implant components rather than the supporting bone.

Because the findings are derived from computational modeling rather than clinical outcomes, they should be interpreted as biomechanical insights rather than direct predictors of long-term clinical success.

7. Clinical Applications

The results may be particularly relevant for clinicians managing:

• Severe maxillary atrophy requiring advanced implant rehabilitation.
• Full-arch implant-supported prosthetic reconstruction.
• Cases involving autogenous bone grafting procedures.
• Treatment planning with zygomatic implants.
• Digital workflows for custom-made subperiosteal implants.
• Complex implant-supported prosthetic restorations where biomechanical optimization is a major concern.

The study also emphasizes the importance of prosthetic framework design and load distribution in reducing the risk of biological and mechanical complications during long-term follow-up.

8. Level of Evidence, Limitations, and Transparency

This investigation represents a preclinical finite element analysis study, which provides valuable biomechanical information but does not offer the level of evidence associated with prospective clinical trials or systematic reviews.

Several limitations were acknowledged by the authors. The models were based on computational assumptions that cannot fully reproduce biological conditions encountered in clinical practice. Stress accumulation around stabilization screws used for subperiosteal implants was not specifically analyzed. Furthermore, finite element models cannot account for all patient-related variables that influence long-term implant success.

The authors clearly state that the findings should be interpreted within the limitations of virtual simulations and require validation through in vivo studies and clinical research.

Regarding transparency, the study was supported by the Hacettepe University Scientific Research Projects Coordination Unit, and the authors reported no conflicts of interest related to the study.

9. Key Study Points

• Study Type: Three-dimensional finite element analysis (3D FEA)
• Level of Evidence: Preclinical computational study
• Population or Sample: Virtual model of an atrophic edentulous maxilla
• Number of Patients: Not applicable
• Number of Implants: Variable according to each simulation model
• Follow-up Duration: Not applicable
• Primary Outcome: Stress distribution within bone, implants, abutments, and prosthetic frameworks
• Main Finding: No treatment option demonstrated universally superior biomechanical performance
• Scientific Conclusion: Each rehabilitation strategy presents distinct biomechanical advantages and limitations
• Potential Limitations: Computational assumptions, absence of clinical validation, and limited analysis of certain implant components

10. Scientific Impact

This study contributes to the implant dentistry literature by providing a direct biomechanical comparison of several advanced treatment concepts used in the rehabilitation of severely atrophic edentulous maxillae. Such comparisons are uncommon because these approaches are often investigated independently.

The research expands current understanding of how grafted bone, zygomatic implants, and modern patient-specific subperiosteal implants respond to functional loading. The findings support the concept that treatment selection should not be based solely on surgical feasibility but should also consider biomechanical behavior and prosthetic design.

Additionally, the study highlights the growing relevance of digitally designed subperiosteal implants and the influence of material properties on load transfer. These observations may help guide future research focused on implant design optimization, CAD/CAM workflows, and long-term rehabilitation strategies for complex maxillary reconstruction cases.

11. Editorial Conclusion

This finite element analysis provides valuable biomechanical insight into four different treatment strategies for the rehabilitation of the atrophic edentulous maxilla. Rather than identifying a single superior solution, the study demonstrates that each approach involves specific mechanical trade-offs affecting bone, implants, abutments, or prosthetic frameworks. For implantologists and oral surgeons managing severe maxillary atrophy, these findings reinforce the importance of individualized treatment planning and careful consideration of biomechanical factors alongside surgical and prosthetic objectives.