Titanium is one of the most important metals in modern medical implants because it combines low density, high strength, and excellent biocompatibility. Surgeons use titanium alloys in hip stems, dental implants, bone plates, screws, spinal cages, and joint replacements. Its light weight reduces stress on the body, while its strength helps implants survive years of loading.
This makes titanium a key material for devices that must work safely inside living tissue.
Key Facts
- Titanium density is about 4.5 g/cm^3, which is much lower than stainless steel at about 7.9 g/cm^3.
- Common implant alloy Ti-6Al-4V contains about 90% titanium, 6% aluminum, and 4% vanadium.
- Stress = F/A, where F is force and A is cross-sectional area.
- Elastic modulus of titanium alloys is about 110 GPa, lower than stainless steel but still much higher than bone.
- A protective TiO2 surface layer forms naturally and helps reduce corrosion in body fluids.
- Osseointegration is strongest when bone cells attach to a clean, stable, roughened titanium surface.
Vocabulary
- Biocompatibility
- Biocompatibility is the ability of a material to function in the body without causing harmful immune, toxic, or inflammatory effects.
- Osseointegration
- Osseointegration is the direct bonding of living bone to the surface of an implant.
- Titanium dioxide
- Titanium dioxide is the thin oxide layer that forms on titanium and protects it from corrosion.
- Elastic modulus
- Elastic modulus is a measure of how stiff a material is when it is stretched or compressed.
- Implant alloy
- An implant alloy is a carefully controlled mixture of metals designed for strength, durability, and safe use in the body.
Common Mistakes to Avoid
- Assuming pure titanium is used in every implant is wrong because many implants use titanium alloys such as Ti-6Al-4V for higher strength and fatigue resistance.
- Calling titanium corrosion-proof is wrong because it resists corrosion mainly due to a protective oxide layer that can still be affected by wear, damage, or extreme chemistry.
- Thinking lighter always means weaker is wrong because titanium has a high strength-to-weight ratio, so it can be both light and mechanically strong.
- Ignoring stiffness mismatch is wrong because an implant that is much stiffer than bone can change how forces pass through the skeleton and may contribute to stress shielding.
Practice Questions
- 1 A titanium hip stem has a volume of 42 cm^3. Using titanium density 4.5 g/cm^3, calculate its mass in grams.
- 2 A dental implant supports a bite force of 300 N over a contact area of 12 mm^2. Calculate the stress in N/mm^2 using Stress = F/A.
- 3 A patient needs an implant that will contact bone for many years. Explain why titanium's oxide layer, strength-to-weight ratio, and ability to osseointegrate make it a strong material choice.