Evaluating the effect of pore size for 3d-printed bone scaffolds

Saran Seehanam, Suppakrit Khrueaduangkham, Chomdao Sinthuvanich, Udom Sae-Ueng, Viritpon Srimaneepong, Patcharapit Promoppatum

Full text link: https://pubmed.ncbi.nlm.nih.gov/38375289/

Evaluating the Effect of Pore Size for 3D-Printed Bone Scaffolds

1. Scientific Reference

• Study Title: Evaluating the Effect of Pore Size for 3D-Printed Bone Scaffolds
• Authors: Saran Seehanam, Suppakrit Khrueaduangkham, Chomdao Sinthuvanich, Udom Sae-Ueng, Viritpon Srimaneepong, Patcharapit Promoppatum
• Journal: Heliyon
• Year of Publication: 2024
• DOI: 10.1016/j.heliyon.2024.e26005

2. Scientific Background

The development of porous metallic scaffolds has become a major area of interest in bone tissue engineering, implant dentistry, and maxillofacial reconstruction. Advances in additive manufacturing now enable the fabrication of highly complex lattice structures capable of combining mechanical strength with biological functionality.

For implant-supported rehabilitation and bone regeneration applications, scaffold architecture plays a critical role in determining both structural behavior and biological performance. Parameters such as pore size, porosity, surface area, and lattice geometry influence cellular attachment, nutrient transport, fluid permeability, and load distribution.

Although several lattice architectures have been proposed for orthopedic and dental applications, defining an optimal pore size remains challenging. Previous studies have reported varying recommendations due to the complex interactions between scaffold geometry, mechanical properties, and biological responses. Within this context, the present study investigates how pore size affects the performance of two widely studied scaffold architectures—Diamond and Gyroid—using a combination of experimental testing and computational modeling.

3. Study Objective

The primary objective of this study was to evaluate the influence of pore size on the suitability of additively manufactured bone scaffolds intended for medical implant applications.

The authors specifically aimed to assess manufacturability, mechanical behavior, and simulated biological performance of strut-based Diamond structures and TPMS-based Gyroid structures fabricated with identical relative density but varying pore dimensions.

4. Methodology

This investigation was designed as a preclinical engineering study combining additive manufacturing, mechanical testing, finite element analysis, computational fluid dynamics (CFD), and cell seeding simulations.

Diamond and Gyroid lattice structures were fabricated from Ti-6Al-4V alloy using Laser Powder Bed Fusion (LPBF). All structures were designed with a constant relative density of 0.3 while pore sizes ranged from 300 μm to 1300 μm.

The investigation included:

• Evaluation of manufacturing accuracy and relative density.
• Compression testing to assess mechanical performance.
• Finite element simulations to examine stress distribution and elastic anisotropy.
• Non-Newtonian CFD simulations to analyze fluid transport characteristics.
• Discrete phase modeling to estimate cell seeding efficiency.

No animal experiments or human clinical data were reported in the information provided.

5. Main Results

The study demonstrated that both scaffold architectures exhibited higher as-built densities when smaller pore sizes were used. However, Gyroid structures showed better manufacturing accuracy because their final density remained closer to the intended design value.

Mechanical testing revealed that pore size had only a limited influence on elastic modulus. In contrast, post-yield behavior was considerably affected by pore size, particularly in Diamond structures. Finite element simulations indicated that Diamond scaffolds developed localized stress concentrations at strut junctions, whereas Gyroid scaffolds exhibited a more homogeneous stress distribution.

CFD analyses showed that pressure drop increased substantially as pore size decreased. Smaller pores enhanced cell seeding efficiency but simultaneously increased flow resistance, creating a trade-off between biological and transport-related parameters.

To address this balance, the authors combined normalized specific surface area, normalized pressure drop, and cell seeding efficiency into a single evaluation metric. Based on this framework, an optimal pore size of approximately 500 μm was identified for both Diamond and Gyroid structures. Furthermore, Gyroid scaffolds achieved higher overall performance scores than Diamond scaffolds.

6. Clinical Analysis

Although this investigation is not a clinical study, it provides valuable insights for the future development of porous implants used in implant dentistry, oral surgery, orthopedic reconstruction, and regenerative medicine.

One of the most relevant findings is the demonstration that pore size influences multiple scaffold functions simultaneously. Smaller pores may improve surface availability and initial cell attachment but can also restrict fluid transport by increasing pressure drop within the scaffold network. Conversely, larger pores facilitate fluid circulation but may reduce the available surface area for cellular interactions.

The study also highlights important architectural differences between Diamond and Gyroid structures. The more uniform stress distribution observed in Gyroid scaffolds suggests a potentially improved mechanical behavior under loading conditions. In addition, the superior manufacturability observed for Gyroid designs may be advantageous when producing patient-specific implants through additive manufacturing workflows.

From a clinical perspective, these findings contribute to the ongoing effort to optimize scaffold design for osseointegration and bone regeneration. However, it is important to emphasize that biological performance was estimated through computational models rather than direct in vivo or clinical validation. Consequently, the results should be interpreted as design-oriented evidence rather than proof of clinical superiority.

7. Clinical Applications

The findings may be relevant for:

• Development of porous bone scaffolds produced through additive manufacturing.
• Design of customized implants for oral and maxillofacial reconstruction.
• Research involving implant surface engineering and osseointegration.
• CAD/CAM-based workflows for patient-specific medical devices.
• Future scaffold development for bone regeneration and implant-supported rehabilitation.

The study may also assist engineers and clinicians involved in designing porous implant structures intended to balance mechanical integrity with biological performance.

8. Level of Evidence, Limitations, and Transparency

This work should be classified as a preclinical experimental and computational study.

The level of evidence remains limited because the biological outcomes were inferred from simulations rather than direct laboratory or clinical observations. No human participants, animal models, or long-term clinical outcomes were included in the information provided.

The authors acknowledge the practical challenges associated with extensive in vitro and in vivo investigations, which partly motivated the use of computational modeling approaches.

Regarding transparency, one of the authors is affiliated with OsseoLabs Co. Ltd. according to the author affiliations listed in the article. No detailed conflict-of-interest statement is available within the provided material.

9. Key Study Points

• Study Type: Preclinical experimental and computational study
• Level of Evidence: Preclinical engineering research
• Population or Number of Studies Analyzed: Not applicable
• Number of Patients or Implants: Not specified in the provided information
• Follow-Up Duration: Not applicable
• Primary Outcome Evaluated: Effect of pore size on scaffold manufacturability, mechanical performance, and simulated biological behavior
• Main Finding: An optimal pore size of approximately 500 μm was identified using a combined evaluation framework
• Scientific Conclusion: Gyroid structures demonstrated greater overall suitability as bone scaffolds than Diamond structures within the study conditions
• Potential Limitations: Absence of biological validation through animal or clinical studies

10. Scientific Impact

This study contributes to the growing body of research focused on optimizing porous implant architectures manufactured through additive technologies.

Rather than examining mechanical properties alone, the authors integrated structural, fluid dynamic, and cell-related parameters into a unified assessment framework. This multidisciplinary approach provides a more comprehensive understanding of how scaffold geometry may influence overall implant performance.

The work also reinforces the scientific interest in TPMS-based architectures, particularly Gyroid structures, which continue to attract attention for their combination of favorable mechanical and biological characteristics. By proposing a computational strategy capable of screening scaffold designs before biological testing, the study may help accelerate future research and reduce development costs associated with experimental investigations.

Moreover, the findings provide additional evidence supporting the importance of pore size optimization in the design of next-generation bone substitutes and patient-specific implantable devices.

11. Editorial Conclusion

This preclinical study offers a comprehensive evaluation of how pore size affects the performance of 3D-printed titanium bone scaffolds. By integrating manufacturing, mechanical, fluid transport, and cell seeding considerations, the authors identified a pore size of approximately 500 μm as the most favorable compromise within the investigated conditions. The results also suggest that Gyroid architectures may provide advantages over Diamond structures in terms of manufacturability and overall scaffold performance. Nevertheless, clinical relevance remains to be confirmed through dedicated biological and clinical investigations.