Fdm

Application of Fused Deposition Modeling (FDM) on Bone Scaffold Manufacturing

Abstract

  • Health Issues: Rise in bone diseases and fractures requiring efficient bone grafting procedures.

  • Bone Grafting: Traditional methods (autographs, allographs, xenografts) have limitations.

  • Biomaterials: Need for bone scaffolds manufactured with additive manufacturing for rapid healing.

  • FDM Technology: Proffers numerous advantages, but challenges include material scarcity and mechanical property optimization.

Introduction

  • Bone Grafting Statistics: Over 500,000 bone graft procedures annually in the U.S.; 2.2 million worldwide.

  • Bone Defects: Significant issues arise from trauma, nonunion, infection causing limb shortening and decreased function.

  • Bone Structure: Composed of spongy and cortical types, primarily collagen (organic) and hydroxyapatite (inorganic).

  • Scaffold Requirement: Effective strategies for restoring damaged tissues include autografting, allografting, and xenografting.

  • Tissue Engineering: Offers a promising approach to create scaffolds that can support cell growth and regeneration.

Key Concepts in Bone Tissue Engineering (BTE)

  • Bone Scaffold Characteristics:

    • Mechanical Properties: Elastic modulus, compressive strength, stiffness.

    • Biological Properties: Biodegradability, biocompatibility.

    • Structural Qualities: High porosity, hierarchical structure.

  • Scaffold Designs:

    • Whole scaffold design variations: uniform, gradient, topology optimization.

    • Unit designs: Voronoi diagrams, TPMS, honeycomb.

Factors Affecting Scaffold Design

  • Porosity and Microarchitecture: Mechanical properties reliant on individual trabecular attractiveness and porosity levels.

  • Materials Used: Three classifications:

    • Metals: Titanium and alloys.

    • Ceramics: Hydroxyapatite and bioglass.

    • Polymers: Natural (collagen, chitosan) and synthetic (PLA, PCL).

  • Additive Manufacturing (AM) vs Subtractive Manufacturing: AM is preferred for creating complex geometries without waste.

Additive Manufacturing Overview

  • Definition: The process of creating products layer by layer.

  • Early Development: Emerged in the late 1980s; includes various 3D printing techniques (SLA, SLS, FDM).

  • FDM Explained:

    • Uses thermoplastic filament heated and extruded to form layers.

    • Ideal for producing detailed parts in biomedical applications.

FDM Process

  • Set-Up: CAD model to .stl to G-code transfer for printer processing.

  • Factors Impacting FDM Quality:

    • Layer thickness, raster angle, build orientation, infill density, printing speed, nozzle diameter, extrusion temperature, etc.

  • Material Characteristics: Properties of filaments determine the printed output’s performance in terms of mechanical strength and flexibility.

Design Architecture of Bone Scaffolds

  • Requirements: Scaffolds must degrade correctly and promote ECM formation without damaging human tissues.

  • Porosity and Pore Size: Pore sizes should ideally range from 100 to 600 micrometers for optimal biological performance.

Unit Cell Bone Scaffold Design

  • Variations: Cubic, cylindrical, hexagonal scaffold designs each exhibit unique compressive strength characteristics.

FDM Printing Parameters

  • Layer Thickness: Directly affects mechanical properties and the surface finish of the product.

  • Build Orientation: Influences strength and mechanical integrity; needs careful planning to optimize.

  • Infill Patterns: Different patterns impact weight, strength, and material usage.

FDM Material Considerations

  • Material Selection: Must ensure biocompatibility, mechanical strength, and environmental sustainability.

    • Synthetic Polymers: PLA, PCL, PGA, and their composites are widely studied.

  • Biocomposite Development: Utilizes materials like hydroxyapatite to enhance mechanical properties and biological functions of scaffolds.

Conclusion & Research Gaps

  • Emphasis on the integration of advanced biomaterials and innovative scaffold designs remains crucial for improving therapeutic efficacy in bone regeneration.

  • Continued research is required to refine printing parameters, materials for scaffolds, and an understanding of microarchitecture in scaffold design for optimal usage in clinical settings.