Corrosion of Biomaterials in dentistryMSE 531: CORROSION

SIDDHESH R. SAWANT

Outline

• Development of implants

• Biocompatibility

• Properties of biomaterials

• Biomaterials for implants

• Corrosion in biomaterials

• Conclusion

Development of Implants

• Implants in dentistry date back to Egyptian era and traces of use found in South Central American cultures

• In 16th and 17th century implants were made of gold and stone

• Early 20th century flourished use of implants made of gold, stainless steel and cobalt alloy

Biocompatibility

• Interaction between biomaterials and living organisms

• Depends on material properties, tissue and external factors

• The dentistry implants are constantly exposed to different temperature and pressure conditions

• Constant contact with different fluids of varying pH

• pH value of human saliva 5.2 to 7.8

Properties of Biomaterials

• The materials selected should have high modulus of elasticity

• They should have high tensile and compressive strengths

• They should have high yield strength and fatigue strength to avoid brittle fracture under cyclic loading

• Minimum ductility of 8% required for dental implants

Biomaterials for Implants

Metal alloys corrosion

• Depends on type of metal used and environment it is exposed

• Oxidation and reduction reactions result into corrosion

• Galvanic type corrosion is observed in regions where two metals with different electrode potential come in contact in presence of an electrolyte

• Crevicular corrosion occurs if there is crack in the metal surface

Pourbaix diagram

Pourbaix diagram for immune metal (gold) Pourbaix diagram for passive element (titanium)

Potential vs Current density

Potential vs current density for some biomaterials

Corrosion of resin based composites

• Modern dentistry uses implants made from composites

• Due to external loads it may result in matrix deterioration, microcracking, interfacial debonding

• Usually biotribocorrosion is the cause of material degradation in composites

Corrosion in ceramics

• Ceramics are good material choice for dental implants when used in form of alloy.

• Corrosion affects the dental ceramics at the interface lines creating small holes

• Zirconia based ceramic is a common material for dentistry implants

• Zirconia is sensitive to stress corrosion because of the change in crystalline phase

Conclusion

• To prevent corrosion of biomaterials in dentistry, it is important to recognize the factors causing these corrosion types

• Same material type usage should be given emphasis for the same patient

• Materials with similar corroding potential value should be given preference with the idea of biocompatibility

• Measures should be taken to keep materials electrically insulated