Evaluation of Different Subperiosteal Implant Thicknesses on Mechanical Strength and Stress on Bone by Finite Element Analysis

Evaluation of Different Subperiosteal Implant Thicknesses on Mechanical Strength and Stress on Bone by Finite Element Analysis

1. Scientific Reference

• Study Title: Evaluation of Different Subperiosteal Implant Thicknesses on Mechanical Strength and Stress on Bone by Finite Element Analysis
• Authors: Abdulsamet Kundakcioglu, Mustafa Ayhan
• Scientific Journal: International Journal of Medical Sciences
• Year of Publication: 2024
• DOI: 10.7150/ijms.91620

2. Scientific Background

The management of severely atrophic jaws remains one of the major challenges in dental implantology and oral surgery. In certain edentulous patients presenting advanced bone resorption, the placement of conventional endosseous implants may become difficult or even impossible without resorting to bone reconstruction procedures.

Bone grafting techniques and zygomatic implants are recognized alternatives, but they may be associated with increased surgical complexity, longer treatment duration, or a higher risk of complications. In this context, the renewed interest in customized subperiosteal implants, made possible by CAD/CAM digital technologies and additive titanium manufacturing, opens new therapeutic perspectives.

However, the presence of a metallic structure directly beneath the soft tissues raises questions regarding the optimal thickness of these devices. Excessive reduction in thickness could compromise the mechanical strength of the implant, whereas an overly bulky design could increase the risk of soft tissue exposure.

3. Study Objective

The primary objective of this study was to determine the minimum thickness of a customized subperiosteal implant capable of withstanding physiological masticatory loads while limiting the mechanical stresses transmitted to the supporting bone.

The authors compared three identical implant designs manufactured with different thicknesses (1 mm, 1.5 mm, and 2 mm) in order to evaluate their biomechanical behavior using finite element analysis.

4. Methodology

This was a preclinical experimental study based on finite element analysis (FEA).

The researchers used computed tomography data from 11 patients treated with customized subperiosteal implants to generate an average digital model of the atrophic maxilla.

Three implant models were subsequently designed with thicknesses of:

• 1 mm (M1)
• 1.5 mm (M2)
• 2 mm (M3)

The implants were manufactured from Ti6Al4V alloy. A vertical load of 250 N simulating an occlusal force was applied. The investigated parameters included:

• Von Mises stresses within the implant;
• Residual stresses transmitted to the bone;
• Mechanical displacements;
• Risk of plastic deformation of the device.

5. Main Results

The differences observed among the three configurations mainly concerned the mechanical strength of the implant and the displacements generated under loading.

The 1 mm-thick implant (M1) exhibited the highest maximum stress, with a value of 495.44 MPa, exceeding the safety threshold set at 415 MPa. This situation suggests a risk of plastic deformation under functional loading.

The 1.5 mm and 2 mm models demonstrated maximum stresses of 173.24 MPa and 144.58 MPa, respectively, remaining well below the critical threshold defined by the authors.

Regarding stresses transmitted to the bone, all three models remained below the safety limit adopted in the study. The maximum observed values were:

• 26.63 MPa for M1;
• 25.95 MPa for M2;
• 22.15 MPa for M3.

Displacements were also influenced by thickness. The thinnest model exhibited a maximum displacement of 1.44 mm, whereas the 2 mm model showed a displacement of approximately 0.46 mm.

6. Clinical Analysis

This study provides valuable insight into a rarely documented aspect of implant rehabilitation using customized subperiosteal implants: the balance between design thinness and biomechanical safety.

The analysis demonstrates that excessive reduction in thickness may lead to a substantial increase in mechanical stresses concentrated at fixation interfaces. These areas appear to represent the most critical points of the implant system. When the thickness decreases to 1 mm, mechanical strength becomes insufficient according to the criteria adopted by the authors.

From a clinical perspective, these findings are particularly relevant in the management of patients with severe maxillary atrophy for whom conventional alternatives may require complex bone reconstruction procedures. The study suggests that a thinner design is not necessarily synonymous with clinical improvement if it is accompanied by a loss of mechanical stability.

The results also indicate that a thickness of 1.5 mm could represent a compromise between reducing metallic volume and maintaining satisfactory strength. However, this interpretation should remain cautious since it is based on a numerical simulation rather than long-term clinical evaluation.

The study does not allow direct assessment of implant survival rates, biological complications, prosthetic stability, or patient-reported outcomes.

7. Clinical Applications

The findings of this work may be useful in several clinical situations involving digital implant rehabilitation protocols:

• Patients presenting severe maxillary atrophy;
• Candidates for customized subperiosteal implants manufactured through additive manufacturing;
• Cases in which extensive bone grafting procedures are difficult to consider;
• Digital implant planning using CAD/CAM workflows;
• Optimization of the mechanical design of customized implants.

This study may also help guide teams involved in computer-assisted design of subperiosteal implants by highlighting the direct impact of material thickness on the distribution of mechanical stresses.

8. Level of Evidence, Limitations, and Transparency

This study corresponds to a preclinical experimental investigation based on finite element numerical modeling.

The level of clinical evidence is therefore limited, as no prospective clinical comparison or long-term patient evaluation was performed within the framework of this biomechanical analysis.

Among the identifiable limitations:

• Results obtained from a virtual model;
• Simulation of a single vertical load of 250 N;
• Absence of direct clinical evaluation of complications;
• Absence of implant survival data;
• Inability to reproduce all real biological conditions.

The authors themselves specify that conclusions derived from finite element analysis require long-term clinical validation.

Regarding transparency, the authors declare no conflicts of interest.

9. Key Study Points

• Study Type: Preclinical experimental study using finite element analysis
• Level of Evidence: Low to moderate (biomechanical modeling)
• Population or Number of Studies Analyzed: Digital model constructed from 11 patients
• Number of Patients or Implants: 11 radiological records used to generate the average model
• Follow-up Duration: Not applicable
• Primary Outcome Evaluated: Mechanical strength and bone stresses according to implant thickness
• Main Result: The 1 mm model exceeds the mechanical safety threshold adopted by the authors
• Scientific Conclusion: A thickness of 1.5 mm appears sufficient under the simulation conditions investigated
• Potential Limitations: Numerical study without direct clinical validation

10. Scientific Impact

This publication contributes to the development of customized subperiosteal implants manufactured by metallic 3D printing, a field experiencing renewed interest in the rehabilitation of severely atrophic jaws.

Its main contribution lies in the quantitative evaluation of the influence of material thickness on the biomechanical behavior of the implant. While many studies focus on clinical outcomes or design concepts, this investigation concentrates on a technical parameter that may influence both mechanical stability and the clinical integration of the device.

The presented data support the concept that thickness reduction is possible up to certain limits without compromising mechanical strength. They therefore provide useful information for optimizing future designs of subperiosteal implants produced through CAD/CAM digital workflows.

However, these findings constitute more of a basis for reflection in research and biomedical engineering than definitive clinical validation.

11. Editorial Conclusion

This biomechanical study provides original data regarding the impact of thickness on customized titanium subperiosteal implants manufactured through additive manufacturing. The simulations indicate that a thickness of 1 mm could expose the implant to a risk of mechanical deformation, whereas a thickness of 1.5 mm appears to maintain performance compatible with the adopted safety criteria. Although promising for digital planning in advanced implantology, these findings must be interpreted in light of the preclinical nature of the study and require confirmation through long-term clinical investigations.