Dental implants, as a newest restoration method for missing teeth, have been commonly carried out in China. Dental implants are known as the “third set of real teeth for human beings”, and they are comfortable, non-abrasive and long-lasting, and have become the preferred solution for missing teeth. Dental implants are composed of artificial roots, also called implants, abutments, and crowns.
The main material for implants is titanium, so what are the properties of titanium?
I. Application of titanium in medicine
1, titanium as an emerging material in our country and the world pharmaceutical industry, surgical instruments, human implants and other fields have been used for decades, and has achieved great success.
2, the human body should be trauma, tumor caused by bone, joint injury, the use of titanium and titanium alloy can be manufactured artificial joints, bone plates and screws are now widely used in clinical. Also used in hip joints (including femoral head), knee joints, elbow joints, metacarpophalangeal joints, interphalangeal joints, lower M bone, artificial vertebrae (spinal orthosis), pacemaker shell, artificial heart (heart valves), artificial dental implants, and titanium mesh in skull shaping and other aspects.
3. The requirements for implant materials can be grouped into three areas: biocompatibility of the material with the human body, corrosion resistance of the material in the human environment and mechanical properties of the material, as long-term implant materials have the following seven specific requirements.
(1) Corrosion resistance ;
(2) Biocompatibility;
(3) superior mechanical properties and fatigue properties;
(4) toughness;
(5) Low modulus of elasticity;
(6) Good wear resistance in the assemblies;
(7) satisfactory price;
4, surgical implant materials are: metals, polymers, ceramics, etc. Metal materials include stainless steel, base alloys and titanium-based alloys.
Comparison of material properties and bone properties and implant material characteristics are shown in Table I and Table II. Table II shows that stainless steel is inexpensive and easy to process, but corrosion resistance and biocompatibility is not as good as titanium alloys; t alloy wear resistance is better than titanium alloys, but the density is greater, too heavy; titanium and titanium alloys due to high specific strength, good biocompatibility and good corrosion resistance of body fluids and other characteristics are being increasingly important. The shortcomings of titanium alloys are poor wear resistance, difficult to cast, and poor processing performance.
Second, the domestic and foreign surgical implants with titanium and titanium alloy processing material standards
1, foreign surgical implants with processing material standards
Pure titanium: International Organization for Standardization ISO 5832/2 1999E “surgical implants – pure titanium processing materials
U.S. standards: ASTM F67 2006a “surgical implants with pure titanium
TC4: ISO 5832/3 1996Z Surgical implants – Metallic materials – Ti-6Al-4V processed materials
ASTM F1472 2002 Processed Ti-6Al-4V alloy for surgical implants
TC4ELI: ASTM F136 2002a “Specification for Ti-6Al-4VELI (Ultra Low Clearance) Processed Materials for Surgical Implants
TC20: ISO 5832/11 I994(E) “Surgical implants – Metallic materials – Ti-6Al-7Nb alloy processed materials
ASTM F1295:2005 “Ti-6Al-7Nb alloy processed material for surgical implants
2.Chinese national standards
①, “Titanium and titanium alloy processing materials for surgical implants” Chinese national standard is GB/T13810-2007, the grades are: TA1ELI, TA1, TA2, TA3, TA4, TC4, TC4ELI, TC20.
Varieties are: plate 0.8～25mm; bar 7.0～90mm; wire 1.0～7.0mm;
GB T13810-2007 standard in the performance indicators.
②, GB/T13810-2007 standard, in order to ensure the comprehensive performance of titanium and titanium alloy processing materials for surgical implants (strength, plasticity, toughness, hardness, fatigue resistance and other properties of a reasonable match), the two-phase titanium alloy of high times the metallurgical organization and hydrogen content and other interstitial element content have very strict requirements and control.
③, in order to ensure the safety and service life of titanium and titanium alloy processed materials implanted in the human body, the national standard requires a strict 100% ultrasonic flaw inspection of plate and bar processed materials to ensure the internal quality of the product.
3.Chinese national standards and foreign advanced standards of comparison
Pure titanium –
①, pure titanium processing material in the chemical composition and microstructure and other indicators are equivalent to
ISO 5832/2:1999(E) requirements;
②, mechanical properties equal to or higher than ISO 5832/2, and increased the index requirements of the sectional shrinkage
③. Ultrasonic inspection is added to the plates and bars.
TC4 processing material –
①, chemical composition and microstructure equivalent to ISO 5832/3: 1996 (E) requirements;
②, mechanical properties requirements are higher than ISO 5832/3, increased the index of bar sectional shrinkage;
③, the plate and bar increased the ultrasonic inspection requirements
TC4ELI processing material–
①, in the chemical composition, mechanical properties, bending properties and other indicators equivalent to
ASTM F136 2002a requirements;
②. Microstructure rating has been added;
③. Ultrasonic inspection requirements for bars and plates;
TC20 alloy processing material –
①, chemical composition, mechanical properties, microstructure and other indicators are equivalent to
ISO 5832/11 1994 (E) requirements;
②, increased the low-temperature tissue test;
③. Ultrasonic test is added to the bar;
Conclusion
Chinese national standard – “titanium and titanium alloy processing materials for surgical implants” GBT13810-2007, including all foreign titanium and titanium alloy processing materials for surgical implants involved in the specification of titanium grades, the indicators of the standard is stricter than similar products foreign standards, but also increased the foreign standard does not have the ultrasonic The standard is stricter than the foreign standards for similar products, and also adds the ultrasonic inspection requirements that are not available in foreign standards. The products produced according to the requirements of this standard can fully meet the requirements of foreign standards.
Attachment.
1, titanium alloy organization and the relationship between performance
There is a close relationship between the organization and performance of titanium alloys, what kind of organization will have the corresponding performance and its counterpart. Due to the special nature of the material for human implants, countries have put forward the requirements for the rating of the metallographic organization of the material – to get equiaxed spherical organization, does not allow the existence of coarse mesh basket and Weiss organization, which is the basic guarantee of the performance of the material.
What kind of processing organization is obtained is entirely determined by the forging and rolling thermal processing process, which is the core and key of producing qualified titanium for human implants, and it also represents the technical level of a company.
Titanium and titanium alloys after thermal processing can usually be obtained after three kinds of organization.
Wei’s organization – the performance of this type of organization is characterized by high strength, but the fatal weakness is low plasticity and impact toughness. It is the undesired organization of the processed material.
Equiaxial organization-The performance of this type of organization is characterized by good overall performance, especially good plasticity and impact toughness, with the highest fatigue strength. It is the most desirable tissue.
Mesh basket – The properties are between Weiss and equiaxial. Sometimes selective use of this organization.
2, TA1, TA2, TA3, TA4, the difference between the four industrial pure titanium
China will be industrial pure titanium according to the number of impurity elements it contains is divided into four grades, namely TA1, TA2, TA3, TA4. they are with the United States 1 ~ 4 grade titanium basic correspondence, namely Gr.1, Gr.2, Gr.3, Gr.4. With the reduction of purity, industrial pure titanium strength, hardness, while plasticity, impact toughness, fatigue resistance is reduced. TA3 and TA4 are optional for high requirements of strength, hardness and wear resistance, and TA1 and TA2 can be used for better formability.
3, the impact of impurity elements on titanium properties
Impurities in titanium, especially interstitial impurities, not only plasticity and toughness is reduced, but also fatigue performance, creep resistance, gap sensitivity are very harmful.
Surgical implants with titanium processing material, because of its special use, in order to ensure its good performance and service life, should focus on controlling the content of impurity elements. Both strength, but also sufficient plasticity, toughness and good fatigue resistance.