IMPLANT BIOMATERIALS: Engineering the Future of Implants.pptx

Implant biomaterials are meticulously engineered to meet a complex set of requirements: they must be biocompatible, durable, and capable of supporting tissue integration. The development of these materials involves a deep understanding of both materials science and biological interactions, as well as the ability to predict and mitigate potential complications.

With the continuous evolution of technology and materials science, the field of implant biomaterials is rapidly advancing. Researchers and engineers are exploring innovative materials and surface treatments that enhance performance and longevity while minimizing adverse reactions. This dynamic field promises to revolutionize the landscape of medical implants, offering new solutions to age-old challenges and paving the way for more effective, personalized treatments.

As we delve into the intricacies of implant biomaterials, we uncover a fascinating intersection of science, engineering, and medicine that is shaping the future of healthcare.

1. IMPLANT BIOMATERIALS DR. SATVIKA PRASAD MDS DEPT. OF PROSTHODONTICS MMCDSR

2. CONTENTS Introduction Definition Classification Requirements of an ideal implant material Implant properties Biomaterials Conclusion References

3. INTRODUCTION Replacement of missing teeth has always posed a challenge to the dentist in terms of esthetics and masticatory loading. With fixed replacements, disadvantages of reduction of abutment teeth decreases. Therefore, dental implants has revolutionized replacement of missing natural teeth. In 1952, Branemark developed a threaded implant designed made of pure Ti that showed direct contact with bone. Hence, popularity of implants reached new heights. Currently there are various materials available as implant material; but for success and longevity of it depends on 4 B’s BIOMATERIAL BIOMECHANICS BIOLOGICAL TISSUES BODY SERVICABILITY

4. CLASSIFICATION A) ACCORDING TO COMPOSITION

5. B) ACCORDING TO TISSUE RESPONSE

6. Requirements of an ideal implant material Any material used as implant must meet 2 basic criteria Implant material should have certain ideal physical, mechanical, chemical & biological properties to fulfill these basic criteria Biocompatibility with living tissue Bio- functionaliity with regard to force transfer

7. BULK PROPERTIES Modulus of elasticity Tensile strength Compressive strength Shear strength Yield strength Fatigue strength Ductility Hardness & toughness Electrical & thermal conductivity SURFACE PROPERTIES Surface tension Surface energy Biocompatibility Corrosion resistance Cytotoxicity of corrosion products Bone and implant surface interaction Implant properties can be studied under

8. Bulk properties MODULUS OF ELASTICITY (E) – Measure of change in dimension with respect to stress. This will ensure, more uniform distribution of stress at implant bone interface Ideally a biomaterial with elastic modulus comparable to bone (18GPa ) should be selected TENSILE, COMPRESSIVE, SHEAR STRENGTH – Any implant material should have high tensile, compressive and shear strength to prevent fracture & improve functional stability Tensile strength- the maximum load that a material can support without fracture when being stretched Compressive strength- the maximum load that a material can support without fracture when being compressed Shear strength-  the force that tends to slide the adjoining parts of a body relative to each other, without fracturing the material

9. YIELD & FATIGUE STRENGTH – Implant materials should have high yield and fatigue strength to prevent brittle fracture under cyclic loading DUCTILITY – Ability of a material to deform plastically under a tensile stress before it fractures It safeguards against brittle fracture of implant It is minimum 8% for implants. Yield strength- Magnitude of stress at which a material shows initial permanent deformation Fatigue strength- Stress at which material fractures under repeated loading

10. HARDNESS & TOUGHNESS Hardness = resistance to permanent surface indentation Toughness = amount of energy required to fracture a material Increased Hardness = Decreases Wear of implant Increased Toughness = Prevent Fracture of implant ELECTRICAL & THERMAL CONDUCTIVITY Should be minimum to prevent thermal expansion, contraction and oral galvanism

11. Surface properties SURFACE TENSION & SURFACE ENERGY Determines- Wettability of implant by wetting fluid (blood) Cleanliness of implant surface Results in good tissue integration with load carrying capacity BIOCOMPATIBILITY Material to perform with an appropriate biological response Mainly a surface phenomenon Most important requirement for a biomaterial depends on Corrosion resistance Cytotoxicity of corrosion products

12. CORROSION RESISTANCE Deterioration of metal caused by reaction with its environment = corrosion Types of corrosion- Stress corrosion- cracking due to increased stress Fretting corrosion- micromotion or rubbing contact within a corrosive environment Crevice corrosion- occurs in narrow region e.g.- implant screw- bone interface Pitting corrosion- occurs in surface pit Galvanic corrosion- occurs between 2 dissimilar metal in contact within an electrolyte Electrochemical corrosion- anodic oxidation & cathodic reduction take place resulting in ,metal deterioration as well as transfer of charge via electron All these types of corrosion & charge transfer can be prevented by Presence of passive oxide layer on metal surface

13. CYTOTOXICITY OF CORROSION PRODUCTS- Toxicity of implant materials depends on toxicity of corrosion products which depends on- Amount of material dissolve by corrosion Amount of corrosive particles deposited in tissue CORROSION RESISTANCE + TOXICITY = BIOCOMPATIBILITY BONE & IMPLANT SURFACE INTERACTION Implant material should have an ability to form direct contact/ interaction with bone Osseointegration Which is dependent on biocompatibility + surface treatment

14. biomaterials TITANIUM Gold standard in implant materials. Pure Ti occurs in 4 grades – I, II, III, IV -> based O 2 & Fe content Consist of 2 phases α (6% Al acts as α stabilizer) β (4% Vanadium acts as β stabilizer) Casting of Ti alloy is difficult due to high melting point (1700 ºC ). It absorb N, H, O 2 from air during casting which makes it brittle

15. It is one of the MOST BIOCOMPATIBLE material due to excellent corrosion resistance Due to formation of biologically inert oxide layer TiO TiO 2 Ti 2 O 3 ( Anastase ) Rutile Brookite Most stable & Mostly formed Oxide layers are SELF HEALING i.e. if surface is scratched / abraded during implant placement it REPASSIVATES instantaneously Low level of charge transfer Main reason for excellent biocompatibility

16. TITANIUM ALLOY – Ti 6Al 4V α stabilizer β stabilizer Consist of – Titanium – 90% Aluminum – 6% Vanadium -4% Properties – Excellent corrosion resistance Oxide layer is formed which is resistant to charge transfer thus contributing to biocompatibility Modulus of elasticity is 5.6 times that of the bone, more uniform distribution of stress Strength of Ti alloy is 6 times greater than pure Ti.

17. COBALT, CHROMIUM, MOLYBEDNUM ALLOYS Composed of same elements as Vitallium Vitallium introduced in 1937 by Venable Strock & Breach Composition- Cobalt- 63% Chromium- 30% - provides corrosion resistance Molybednum - 5% - provides strength Properties – High mechanical strentgth Good corrosion resistance Low ductility Direct apposition of bone to implant is seen, but it is interspersed with fibrous tissue Uses:- Limited for fabrication of custom designs for subperiosteal frames due to ease of castability and low cost

18. IRON, CHROMIUM, NICKEL BASED ALLOY These are surgical steel alloys or austenitic steel Composition- Iron – 74% Chromium- 18% - corrosion resistance Nickel – 8 % -stabilize austenitic steel Properties – High mechanical strength High ductility Pitting and crevice corrosion Hypersensitivity to Ni has been seen Bone implant interface shows fibrous encapsulation & ongoing foreign body reactions Use is limited

19. PRECIOUS METALS- Gold, Platinum, Palladium They are noble metals unaffected by air, moisture, heat and most solvents Do not depend on surface oxides for their inertness Properties- Low mechanical strength Very high ductility More cost per unit weight Not used

20. CERAMICS

21. BIOINERT CERAMICS Those ceramics show direct bone apposition at implant surface but do not show chemical bonding to bone Properties Bioinert ceramics are full oxides thus excellent biocompatibility Good mechanical strength Low ductility which results in brittleness Color similar to hard tissue Uses- Initially thought to be suitable for load bearing dental implants but due to inferior mechanical properties Used as surface coatings over metals To enhance their biocompatibility To increase the surface area for stronger bone to implant surface

22. BIOACTIVE CERAMICS Calcium phosphate ceramics These have evoked greatest interest in present times Mainly consists of- Hydroxyapatite(HA) Tricalcium phosphate (TCP)

23. Properties- CPC have biochemical composition similar to natural bone CPC form direct chemical bonding with surrounding bone due to presence of free calcium and phosphate compounds as implant surface Excellent biocompatibility No local or systemic toxicity No alteration to natural mineralization process of bone L ow mechanical tensile, shear strength, fatigue strength Brittle, low ductility Exists in amorphous or crystalline form Exists in dense or porous form

24. Solubility of CPC CPC show varied degree of resorption or solubility in physiologic fluids The resorption depends on Crystallinity High crystallinity is more resistant to resorption Particle size -Large particles size requires longer time to resorb 2. Porosity Greater the porosity, more rapid is the resorption. 3. Local environment Resorption is more at low pH e.g. in case of infection or inflammation 4. Purity presence of impurities accelerate resorption

25. Uses - Due to lack of mechanical strength, not used as load bearing implants Used as Bone grafts material for augmentation of bone As bioactive surface coating for various implant material to increase Biocompatibility Strength of tissue integration

26. GLASS CERAMICS They are bioactive ceramics Bioglass or Ceravital Silica based glass with additions of calcium and phosphate produced by controlled crystallization Properties High mechanical strength Less resistant to tensile and bending stresses Extremely brittle They chemically bond to the bone due to formation of calcium phosphate surface layer

27. USES-  Inferior mechanical properties – not used as load bearing implant Used more often as bone graft material When used as coating bond between coating and metal substrates is weak and subject to dissolution

28. CARBON AND C- SILICONE COMPOUNDS Properties Inert Biocompatible Modulus of elasticity is close to that of bone Bone implant interface shows osseointegration Brittle Susceptible to fracture under tensile stress Used mainly as surface coatings for implants materials 

29. Advantages Tissue attachment Can be used in the regions that serve as barrier to elemental transfer of heat and electrical current flow Control of color and provide opportunities for the attachment of active biomolecule or synthetic compounds. Limitations 1. Mechanical strength properties are relatively poor. 2. Biodegradation that could adversely influence tissue stability. 3. Time dependent changes in physical characteristics. 4. Minimal resistance to scratching or scraping procedures associated with oral hygiene.

30. POLYMERS Polymeric implants were first introduced in 1930s However they have not found extensive use in implant due to- Low mechanical strength Lack of osseointegration e.g. – Polymethyl methacrylate (PMMA) Polytetrafluoro ethylene (PTFE) Polyethylene tetrapthylate (PETP) Dimethyl polysiloxane Ultrahigh molecular weight polyethylene (UHMWPE)

31. Used currently to provide shock absorbing qualities in load bearing metallic implants. E.g. in IMZ ( intramobile cylinder implants) system a polyoxymethylene intra mobile element (IME) is placed between prosthesis and implant body which- Ensures more uniform stress distribution Acts as internal shock absorber

32. The key component of the IMZ implant system is the intramobile element (IME), whose purpose is to simulate the viscoelasticity of the periodontal ligament and reduce the forces transmitted to the marginal bone–implant interface . Since the implant and IME are rigidly connected, the IME serves to reduce the displacement between the osseointegrated implant and a natural tooth while also impeding the intrusion of natural teeth

33. COMPOSITES Combinations of polymers and other categories of synthetic biomaterials. Several of the inert polymers have been combined with particulate or fibers of cotton, aluminum oxide, and hydroxyapatite and glass ceramics. They are intended as structured scaffolds, plates, screws or other such applications. Disadvantages 1. In general, polymers and composites of polymers are especially sensitive to sterilization and handling techniques. If intended for implant use, most cannot be sterilized by steam or ethylene oxide. 2. Most polymeric biomaterials have electrostatic surface properties and tend to gather dust or other particulate if exposed to semiclean oral environments. 3. Because many can be shaped by cutting or auto- polymerizing in vivo (PMMA), extreme care must be taken to maintain quality surface conditions of the implant 4. Porous polymers can be deformed elastically, which can close open regions intended for tissue ingrowth. 5. Also, cleaning the contaminated porous polymers is not possible without a laboratory environment.

34. sterilization Conventional sterilization is Steam- results in contamination of surfaces Dry- also leaves organic & inorganic surface residues Therefore special methods are used, Radiofrequency glow discharge technique (RFGDT) or plasma cleaning Most frequently used Cleaning is done as it is bombarded by high energetic ions formed in gas plasma in a vacuum chamber. Hence NOT USED

35. Plasma created by the electric discharge of a gas between two electrodes in a low-pressure chamber is called glow discharge plasma. Glow discharge happens when free plasma electrons recombines with positive ions and emit photons. This phenomenon lies between the dark discharge region with low current ionization and no light emission, and arc discharge with large radiations. Glow discharge plasma contains energetic ionized gases species, which can be used for different purposes, cleaning a surface or coating it, as sputtering deposition method.

36. UV sterilization Cleans surface Increases surface energy Gamma radiation Used to sterilize pre packaged dental implants

37. conclusion Implant biomaterials are a cornerstone of modern medical advancements, offering significant improvements in the quality of life for patients through enhanced functionality, biocompatibility, and longevity of implants. Advances in materials science have led to the development of innovative biomaterials that not only meet the mechanical and biological demands of implants but also contribute to the healing process and long-term success of various procedures. As research continues to evolve, the future promises even more refined materials with tailored properties to address specific clinical needs. Ultimately, the ongoing exploration and development of implant biomaterials will play a crucial role in pushing the boundaries of medical technology and improving patient outcomes across a wide range of therapeutic areas.

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