ASTM F2129 (Cyclic Polarization): Detects hydrogen susceptibility in simulated body fluid (SBF). Slow Strain Rate Test (ASTM E8/E292): Tests delayed fracture risk under tension.
Author: Robby
Dental implants (e.g., titanium screws, abutments) are highly sensitive to hydrogen embrittlement due to their small size, high mechanical loads, and exposure to body fluids. Electroplating (e.g., gold plating for aesthetics or hydroxyapatite coatings) can introduce hydrogen, requiring careful removal.
Why? Prevents oxidation while removing hydrogen.
Process:
Temperature: 350–400°C (662–752°F) (below Ti β-transus to avoid grain growth).
Duration: 2–4 hours (depends on part thickness).
Vacuum Level: 10⁻⁵ to 10⁻⁶ mbar (prevents surface contamination).
Standards:
ISO 5832-3 (Titanium alloy implants).
ASTM F86 (Surface preparation for surgical implants).
For:
Stainless Steel (ASTM F138/F1314)
Electroplated Gold or Silver Coatings
Process:
Temperature: 200–250°C (392–482°F) (avoid tempering effects).
Duration: 4–8 hours (longer for thicker coatings).
Critical Note:
Must be done within 1 hour after plating to prevent H₂ diffusion.
Why? Removes ~5–10µm of surface layer where hydrogen concentrates.
Process:
Electrolyte: Perchloric acid + methanol (for Ti) or phosphoric acid (for SS).
Current Density: 10–30 A/dm² for 5–10 mins.
Benefits:
Smoothens surface (reduces bacterial adhesion).
Removes residual hydrogen from acid pickling.
For implants where electroplating is avoidable:
PVD (Physical Vapor Deposition) Gold/TiN: No H₂ generation.
Anodized Titanium: Forms protective oxide layer without H₂ risk.
Bioactive Coatings (e.g., Plasma-Sprayed HA): No electroplating needed.
ASTM F2129 (Cyclic Polarization):
Detects hydrogen susceptibility in simulated body fluid (SBF).
Slow Strain Rate Test (ASTM E8/E292):
Tests delayed fracture risk under tension.
Metallography (ASTM F561):
Checks for H₂-induced microcracks near threads.
Issue: Fracture after 6 months due to unremoved hydrogen from gold plating.
Root Cause: Skipped post-plate bake.
Solution: Implemented vacuum annealing at 375°C for 3 hrs + 100% ASTM F2129 testing.
✅ For Titanium Implants: Vacuum annealing > baking (avoids oxidation).
✅ For SS/Gold-Plated: Bake at 200–250°C within 1 hr of plating.
✅ Critical Areas (e.g., Screw Threads): Electropolish after acid cleaning.
❌ Never Skip: Hydrogen testing per ASTM F2129 or ISO 16429.