Mechanical evaluation of a patient-specific additively manufactured subperiosteal jaw implant (AMSJI) using finite-element analysis

Mechanical Evaluation of a Patient-Specific Additively Manufactured Subperiosteal Jaw Implant (AMSJI) Using Finite Element Analysis

1. Scientific Reference

• Study Title: Mechanical Evaluation of a Patient-Specific Additively Manufactured Subperiosteal Jaw Implant (AMSJI) Using Finite Element Analysis
• Authors: E. De Moor, S. E. F. Huys, G. H. van Lenthe, M. Y. Mommaerts, J. Vander Sloten
• Journal: International Journal of Oral and Maxillofacial Surgery
• Year of Publication: 2022
• DOI: 10.1016/j.ijom.2021.05.011

2. Scientific Background

Managing completely edentulous patients with advanced maxillary bone atrophy remains one of the most challenging situations in implant dentistry and oral surgery. Conventional root-form dental implants often require sufficient residual bone volume, making rehabilitation difficult in cases of severe alveolar resorption.

Several treatment strategies have been proposed for these complex cases, including bone grafting procedures, All-on-4 protocols, and zygomatic implants. While these approaches have expanded treatment possibilities, they may also involve surgical complexity, increased morbidity, or specific anatomical limitations.

The development of patient-specific subperiosteal implants manufactured through additive manufacturing technologies represents a renewed interest in customized solutions for severe jaw atrophy. The Additively Manufactured Subperiosteal Jaw Implant (AMSJI) was specifically designed for patients presenting with Cawood and Howell class V to VIII maxillary bone resorption. Before widespread clinical adoption, a detailed biomechanical assessment is essential to determine whether such implants can safely withstand functional loading over time while maintaining structural integrity and supporting long-term rehabilitation.

3. Study Objective

The primary objective of this study was to investigate the biomechanical behavior of a patient-specific AMSJI designed for severely atrophic maxillae using finite element analysis (FEA).

The researchers aimed to evaluate implant safety under physiological and pathological loading conditions, identify regions exposed to the highest mechanical stresses, assess the risk of structural fatigue, and explore the potential contribution of scaffold-mediated bone ingrowth to implant stabilization.

4. Methodology

This research was conducted as a preclinical computational study using finite element analysis.

Three-dimensional digital models of the maxilla and the AMSJI were generated from computed tomography (CT) data. Two anatomical situations were investigated: a Cawood and Howell class V maxilla and a more severely resorbed class VIII maxilla.

The implant was modeled using Ti6Al4V Grade 23 Extra Low Interstitial (ELI) titanium alloy. Different loading scenarios were simulated to reproduce realistic oral function:

• Average occlusal loading: 200 N
• Maximum occlusal loading: 1000 N
• Bilateral clenching: 1000 N
• Unilateral grinding (bruxism): 500 N

The analysis focused on von Mises stresses within the implant, strain distribution within the maxillary bone, and relative micromovements between scaffold structures and bone tissue.

The number of patients included was not specified in the available data, as the investigation was based on individualized digital models rather than a clinical cohort.

5. Main Findings

The simulations demonstrated favorable mechanical behavior of the AMSJI under average occlusal forces of 200 N. Under these conditions, stress levels remained below the fatigue threshold estimated for the intended 15-year implantation period.

Across all loading conditions, the highest stress concentrations were consistently located within the implant arms connecting the basal framework to the prosthetic posts. These regions appeared to be the most mechanically vulnerable components of the design.

When maximum occlusal forces of 1000 N were applied, stress values increased substantially and approached the material’s yield strength in certain regions. Similarly, simulated bruxism scenarios generated considerably higher stress levels than those observed during normal chewing activity.

The class VIII atrophy model exhibited greater stress accumulation within the implant compared with the class V model, suggesting that progressive bone resorption may adversely affect long-term mechanical performance.

The study also found that scaffold-related micromotions remained below thresholds generally considered unfavorable for bone ingrowth, indicating conditions potentially compatible with osseointegration and secondary biological stabilization.

6. Clinical Analysis

This investigation provides valuable biomechanical insight into the use of customized subperiosteal implants for the rehabilitation of severely atrophic maxillae. Rather than evaluating clinical outcomes, the study focuses on the mechanical feasibility of the AMSJI concept under a variety of functional conditions.

One of the most relevant findings is that routine masticatory loading appears unlikely to compromise implant integrity. This observation supports the rationale behind using patient-specific subperiosteal implants in situations where conventional implant placement may be difficult because of advanced bone loss.

The results also emphasize the importance of maintaining residual bone support following implant placement. Increased stress concentrations observed in the class VIII model suggest that ongoing ridge resorption could negatively influence implant longevity through fatigue-related mechanisms.

Another clinically significant aspect concerns patients affected by bruxism. Simulated clenching and grinding generated markedly higher stresses, highlighting a potential risk factor that may influence patient selection and long-term treatment planning.

From an engineering perspective, the identification of the implant arms as the primary stress-bearing regions offers valuable information for future CAD/CAM optimization. Reinforcement of these areas may improve mechanical safety and enhance the overall durability of future AMSJI designs.

Finally, the favorable predictions regarding bone ingrowth into porous scaffold structures support the concept of combining mechanical fixation with biological stabilization, a key objective in contemporary implant design.

7. Clinical Applications

The findings of this study may be relevant in several clinical scenarios, including:

• Rehabilitation of completely edentulous patients with severe maxillary atrophy.
• Cases involving Cawood and Howell class V to VIII bone resorption.
• Situations where bone grafting procedures are undesirable or difficult to perform.
• Digitally planned implant rehabilitation workflows.
• CAD/CAM-based patient-specific implant design.
• Complex oral and maxillofacial reconstruction requiring individualized anatomical adaptation.

Although the results are encouraging, clinical decision-making should remain guided by comprehensive patient evaluation and supported by long-term clinical evidence.

8. Level of Evidence, Limitations, and Transparency

This publication represents a preclinical finite element analysis study, which provides biomechanical evidence but does not constitute clinical proof of treatment efficacy.

The findings are derived from computer simulations and therefore depend on assumptions regarding material properties, loading conditions, implant manufacturing parameters, and biological behavior. Real-life clinical conditions may differ from those modeled in the study.

The authors disclosed potential conflicts of interest. Maurice Mommaerts served as Innovation Manager and Statutory Manager at CADskills, while Stijn Huys held research and development as well as quality management responsibilities within the same company. These affiliations should be considered when interpreting the findings.

The available data do not include clinical follow-up, patient-reported outcomes, survival rates, or long-term complication rates.

9. Key Study Highlights

• Study Type: Preclinical finite element analysis (FEA)
• Level of Evidence: Low to moderate (computational biomechanical study)
• Population or Dataset: Digital anatomical models
• Number of Patients or Implants: Not specified in the available data
• Follow-up Duration: Simulation based on an intended implantation period of 15 years
• Primary Outcome: Mechanical behavior of the AMSJI under functional loading
• Main Finding: Favorable mechanical performance under average occlusal forces
• Scientific Conclusion: The AMSJI appears mechanically safe under normal functional loading conditions in patients with severe maxillary atrophy
• Potential Limitations: Computational modeling, absence of clinical validation, reliance on simulation assumptions

10. Scientific Impact

This study contributes meaningful biomechanical evidence to the growing body of research on patient-specific additively manufactured implants for severe maxillary atrophy.

Its primary contribution lies in the detailed evaluation of stress distribution, fatigue risk, and implant stability under multiple loading scenarios relevant to daily oral function. By identifying the implant arms as the most mechanically critical regions, the work provides practical guidance for future design refinements.

The findings also support the concept of integrating porous scaffold structures into custom-made subperiosteal implants, potentially enhancing biological fixation through bone ingrowth.

Although clinical validation remains necessary, this research represents an important step in bridging digital implant design, additive manufacturing, and complex implant-supported rehabilitation. It establishes a biomechanical foundation that may guide future clinical investigations and technological development in personalized implantology.

11. Editorial Conclusion

This finite element study suggests that the AMSJI concept offers a mechanically viable solution for the rehabilitation of patients with severe maxillary bone atrophy when exposed to normal functional loading. The analysis highlights the influence of residual bone support and parafunctional activity on long-term implant performance while identifying key areas for future design optimization. Although clinical outcomes cannot be inferred directly from computational modeling, the study provides valuable biomechanical evidence supporting the continued development of patient-specific additively manufactured subperiosteal implants.