Biomaterials

Course title: Biomaterials

Department of Biomedical Engineering

Yeditepe University

BME 262

Spring 2010

Meetings: Monday 14:00 – 14:50 Room: B-0319

15:00 – 15:50

Wednesday 14:00 – 14:50 Room: B-0319

15:00 – 15:50

Instructor: Prof. Dr. A. Cuneyt Tas

www.cuneyttas.com

Office hours: Anytime; all days; when I am in my office

(you can also reach me at my labs = Floor -1, No: A204 and Floor -3, No: 105)

Textbook: “Biomaterials Science: An Introduction to Materials in Medicine”

Buddy D. Ratner, Allan S. Hoffman, Frederick J. Schoen, Jack E. Lemons

Elsevier Academic Press, 2^nd Edition

ISBN 0-12-582463-7 (Available in the Yeditepe University Library)

Also available through Google books

Course content:

Relationship between materials science and biological/medical sciences,

Properties of crystalline and non-crystalline materials,

Natural biomaterials,

Synthetic biomaterials,

Materials science in orthopedics,

Ceramic, polymeric and metallic biomaterials,

Mechanical behavior of implant biomaterials,

Interaction of synthetic biomaterials with cells (in vitro studies),

Materials science in cardiology,

Application of materials science related research techniques to medical sciences.

Grading:

2 Exams (30% each) + Homeworks (10%) + Final (30%) =100%

---------------------------------------------------------------------------------------------------------------

What do biomedical engineers do?

Reading Assignment – 1: pp. 1 through 9 of the textbook

Homework -1: Due: Wednesday, February 10 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

1.) Describe the relationship between a “biomaterial” and a “medical device.”

Answer: According to the appropriate definition cited by Prof. Buddy D. Rattner (p. 1) “a biomaterial is a material used in a medical device (remember those three classes of medical devices we discussed in our lectures), which is intended to interact with biological systems.” Therefore, especially those biomaterials used in Class I and Class III medical devices do have close relationship with one another.

2.) Separately list the type of materials used in each of the following medical applications;

(a) bone cement, (b) blood vessel prosthesis, (c) skin repair, (d) contact lenses.

Answer: (a) polymethylmethacrylate, PMMA, some forms of it also known under the commercial names of Plexiglas, Lucite, Vitroflex, Oroglas, Optix, etc. (http://en.wikipedia.org/wiki/Poly(methyl_methacrylate))

(b) polyurethane, Dacron (polyethylene terephthalate: PET) or Teflon (polytetrafluoroethylene)

(c) silicone-collagen composites (here be careful about not confusing silicon (one of the metallic elements) and silicone (a polymerized siloxane)

(d) silicone-acrylate (http://www.dowcorning.com/content/personal/silicone_acrylate.asp) or silicone (http://www.lagado.net/silicone-hydrogels.htm) hydrogels

3.) What do the following mean; (a) in vitro, (b) in vivo?

Answer: (a) in glass environment, (b) in a live environment such as human or animal

4.) What could be the common problems seen with the replacement heart valves (after surgery)?

Answer: The most common problem is “calcification” of the valves, seen in bovine heart valves more frequently than those seen in porcine heart valves. Implanted heart valves may also display problems associated with unexpected blood clotting, tissue degeneration, mechanical failure or infection. (Remember that mechanical failure or the risk of infection are common to most implanted biomaterials, not quite specific to the heart valves.)

5.) Why do surgeons use intraocular lenses? What are the typical materials used in making these lenses?

Answer: Intraocular lenses are used to replace a natural lens when it becomes cloudy due to cataract formation. Such intraocular lenses are typically made of PMMA, silicone, acrylic polymers or hydrogels.

Reading Assignment - 2: pp. 10 through 23 of the textbook

Reading Assignment – 3 (download the article in this weblink)

Reading Assignment - 4

Homework -2: Due: Wednesday, February 17 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

1.) Briefly describe the biomedical utilization areas of polylactic acid (PLA), polyglycolic acid (PGA) and polylacticglycolic acid (PLGA) polymer scaffolds.

Answer: These three polymers and their composite derivatives are intended for use in soft tissue repair applications.

http://teximp.serag-wiessner.de/en/seramesh.html

http://www.biomedexperts.com/Abstract.bme/15199583/Self-reinforced_polylactide_polyglycolide_80_20_screws_take_more_than_1_1_2_years_to_resorb_in_rabbit_cranial_bone

2.) What are the major biomedical application differences between UHMWPE and PLA or PLGA?

Answer: UHMWPE is bioinert (it does not resorb in time), but PLA or PLGA are bioabsorbable. UHMWPE can be produced as quite strong implants, but the same will be difficult to achieve in the case of PLA or PLGA.

3.) What is the difference between Bioglass and ordinary window glass?

Answer: Bioglass is a bioresorbable and biocompatible substance, whereas window glass is not.

Bioglass is mainly comprised of CaO, P2O5, SiO2 and Na2O (45S5 is one of the most popular bioglass compositions) and it is developed by Prof. Larry L. Hench. It forms good in vivo connection with the hard tissues of human body. Natural bone can resorb implanted bioglass samples. Natural bone can also grow on the implanted bioglass samples without exhibiting any cytoxicity and inflammation.

4.) What is Goretex? Do people use this material in biomedical applications?

Answer: It is a subcutaneous augmentation material made of microporous polytetrafluoroethylene (PTFE, Teflon) for the repair or enhancement of soft tissues.

http://www.shimmianmanila.com/gore-tex-implant-links

http://emedicine.medscape.com/article/878937-overview

http://www.markbermanmd.com/chapter8.aspx

Goretex is also used in textile industry: http://www.gore-tex.com/remote/Satellite/home

5.) Who is Sydney Ringer? What did he discover about 130 years ago?

(For questions 4 and 5, you may perform an internet search.)

Answer: See Reading assignment-4

Density of biomaterials

Homework -3: Due: Wednesday, February 24 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

In answering these questions, you must ONLY use your class notes!

1.) How do you perform a test of “cell viability” on a given synthetic biomaterial?

Answer: The following ISO standard must be consulted: ISO-10993-5

2.) Which properties of synthetic biomaterials will determine the in vivo performance of implants?

Answer: Basically; physical, chemical, mechanical and biological properties of synthetic biomaterials would significantly regulate the in vivo performance of these materials upon implantation. However, you should have mentioned in your answer the specific points we discussed during the class hours.

3.) Which crystal structures we mentioned in class last week?

Answer: Cubic, tetragonal, hexagonal, rhombohedral, orthorhombic, monoclinic and triclinic structures were mentioned.

4.) How does the density of a given synthetic biomaterial affect the decision of producing an implant out of it?

Answer: The density of a given synthetic biomaterial must be comparable with that of the tissues into which that material will be implanted.

5.) What does a characteristic stress-strain diagram of a given synthetic biomaterial tell the biomedical engineer?

Answer: The stress-strain diagrams of materials are like their characteristic fingerprints and contain valuable information about the elastic modulus, ultimate tensile strength, fracture strength, toughness and percentage elongation of any implant that can be produced from that material.

Reading Assignment – 5: pp. 23 through 32 of the textbook

ISO-10993-Section 1

BME262 – Feb 24-lecture notes

Homework -4: Due: Wednesday, March 3 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

In answering these questions, you must ONLY use your class notes, textbook or the course website!

No copying from Internet!!

1.) How can you use stress-strain diagrams in selecting the most appropriate material for an orthopedic biomaterial?

Answer: The orthopedic biomaterial (whether it would be made out of metals, ceramics, glasses or polymers) must first be mechanically compatible with the host tissues into which it will be implanted. Therefore, the biomechanical properties and characteristics of the host tissues (i.e., natural tissues which will host the implant material) should first be fully known prior to the insertion of the implant. The stress-strain diagrams of the host tissue and the synthetic materials (from which the implant will be manufactured) must first indicate to a match between the elastic modulus values of both the host tissues (whether they are hard or soft tissues) and the orthopedic biomaterial. Secondly, the stress-strain diagram of the biomaterial must not indicate to a material inferior in ultimate tensile strength, fracture strength and mechanical toughness than the host/natural tissue. The “load-carrying ability” of most orthopedic, synthetic biomaterials is usually required to be slightly higher than that of the host tissue. Stress-strain diagrams possess and convey such information effectively to the biomedical engineer.

2.) Suppose that a certain synthetic biomaterial causes mild inflammation following its implantation in patients. By using which chemical analysis technique you can determine its chemical composition accurate to the ppm level?

Answer: The accurate chemical composition determination accurate to the ppm level is typically performed by using the analytical technique (i.e., an instrument) ICP-AES (inductively-coupled plasma atomic emission spectroscopy). It is well-known that, sometimes, even ppm level impurities (such as those of heavy metal elements or cytotoxic organic molecules) present in a synthetic implant may cause mild inflammation in the patients receiving that implant, and such undesired cases of tissue inflammation may persist for long months after the implantation. AAS (atomic absorption spectroscopy) is not accurate enough for this purpose.

3.) The following sentence is directly taken from ISO-10993-Part1. Explain this sentence in your own words.

“Biological testing relies upon animal models and a material cannot, therefore, be conclusively shown to have the same tissue reactions in humans.”

Answer: Mainly the differences in the metabolisms of human beings and animals could lead to such unforeseen test results; this sentence does mean that even an implant performing very well in all the animal tests cannot be regarded as a solid and non-refutable guarantee for the similar, acceptable performance of the same material in the patient body. This is why the biomedical device (especially those will be implanted under the skin of the patient) testing procedures place a great deal of significance in clinical testing.

4.) What does the italicized and underlined phrase mean in the below sentence?

“All successful and civilized engineering processes must be economically feasible, safe and non-hazardous for the living creatures, statistically-sound, reliable, and reproducible.”

Answer: A detailed answer for this question was provided during the class discussions.

Reading assignment – 6: pp. 40 through 57 of the textbook

BME262 – Mar3-lecture notes

Homework -5: Due: Wednesday, March 10 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

The first question below is for everyone to answer,

but the second and third questions are specific to each one of you.

1.) How can you use AFM (atomic force microscope) to quantitatively determine the surface roughness of a given synthetic biomaterial?

Answer: Study the following weblink: AFM surface roughness

2.) For this question, you first need to make a connection to http://lproxy.yeditepe.edu.tr/login

and then click to the DATABASE - WEB OF SCIENCE link

your specific “Title” search keyword combinations are given below for each of you (journal names are given in quotation marks)

B. Altinkaya: biomimetic AND pmma Who are the authors of the “Journal of Biomedical Materials Research” paper?

B. Asfuroglu: biomimetic AND hydroxyapatite AND synthesis Who are the authors of the “Biomaterials” paper?

B. Atis: biomimetic AND calcium AND carbonate Who are the authors of the “Chemistry – A European Journal” paper?

M. Avci: biomimetic AND plga Who are the authors of the “Surface & Coatings Technology” paper?

S. Bilginer: biomimetic AND polycaprolactone Who are the authors of the “Acta Biomaterialia” paper?

H. Ceben: biomimetic AND cellulose Who are the authors of the “Trends in Biotechnology” paper?

S. Coban: biomimetic AND wood Who are the authors of the “Journal of The American Ceramic Society” paper?

C. Demirbag: biomimetic AND paper Who are the authors of the “Smart Materials & Structures” paper?

M. Erdogdu: biomimetic AND carbon Who are the authors of the “Langmuir” paper?

S. Eren: biomimetic AND sequestration Who are the authors of the “Fuel Processing Technology” paper?

S. Ertas: biomimetic AND peg Who are the authors of the “Biomaterials” paper?

A. Gokalp: biomimetic AND urinary Who are the authors of the “Chemical Senses” paper?

M. Karaoglu: biomimetic AND hydrogel Who are the authors of the “Chemistry of Materials” paper?

I. Kopuklu: biomimetic AND scaffold Who are the authors of the “Nature Materials” paper?

M. Kurdoglu: biomimetic AND implant Who are the authors of the “Biomaterials” paper?

U. Tanriverdi: biomimetic AND substitute Who are the authors of the “Tissue Engineering Part A” paper?

B. Tekinalp: biomimetic AND titanium AND surface Who are the authors of the “Surface & Coatings Technology” paper?

G. Tugcu: biomimetic AND dental Who are the authors of the “Cytotherapy” paper?

E. Turan: biomimetic AND orthopedic Who are the authors of the “Expert Review of Medical Devices” paper?

G. Yasar: biomimetic AND soft Who are the authors of the “Journal of Materials Chemistry” paper?

S. Yasar: biomimetic AND hard Who are the authors of the “Nanomedicine” paper?

B. Yavuz: biomimetic AND tissue AND porous Who are the authors of the “Biomacromolecules” paper?

U. Yurttas: biomimetic AND calcium AND deposition Who are the authors of the “Biomaterials” paper?

D. Zaimoglu: biomimetic AND cement Who are the authors of the “Chemistry of Materials” paper?

3.) For this question, you first need to connect to http://lproxy.yeditepe.edu.tr/login

and then click to the DATABASE - ELSEVIER SCIENCE DIRECT link

then, by using your specific search keyword combinations (from the 2^nd question) typed into the “All fields” box, download the very first paper in your resulting list, attach a copy of that paper to your homework, and write the authors, journal name, journal volume, pages, and publication year information of that article as proper “the answer” to this question.

Homework -6: Due: Wednesday, March 17 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

1.) How can one determine whether a material is crystalline or amorphous?

Answer: by using X-ray diffraction. Usually the chemical solubility or resorbability of a biomaterial depends on its crystalline structure, in some cases there will be a significant difference between the solubility of the amorphous form of the same material with that of the crystalline form.

2.) How can one experimentally measure the contact angle?

Answer: http://www.firsttenangstroms.com/pdfdocs/CAPaper.pdf

3.) How can one relate the contact angle to the properties of the sample surface?

Answer: http://www.gsishop.com/webmagzine/20020925/contact.htm

4.) What does one measure with the IR spectroscopy?

Answer: IR spectroscopy could be used as a very robust method to determine the presence (or absence) of molecular groups (such as, amides, carbonates, hydroxyls, sulphates, nitrates, etc.) within a synthetic or natural biomaterial. It is a quick, reliable and reproducible method.

http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/InfraRed/infrared.htm

5.) Briefly describe the operation principles of scanning tunnelling electron microscope.

Answer: https://www.llnl.gov/str/Scan.html

Reading assignment – 7: pp. 59 through 64 of the textbook

BME 262 – Mar 15 Lecture notes

Reading assignment – 8: Nacre stiffness

Assignment – 9: How do we assess cell attachment and spreading on the surface of a biomaterial? (Simply examine Fig. 1 of this article)

Reading assignment – 10: Nacre - Oaki and Imai paper

Homework -7: Due: Wednesday, March 24 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

1.) Draw a simple cubic unit cell and indicate in this cube the [110] direction. Then, calculate the angle between this direction and the (110) plane.

2.) Why do we see a difference between the X-ray diffraction data of aragonite (CaCO₃) and calcite (CaCO₃)?

3.) Write the difference between the diamond and cubic ZnS structures.

4.) If an implanted synthetic biomaterial is found to cause intracutaneous reactivity to the mucosal membrane surrounding it, how can you test this phenomenon before implantation?

5.) What could be the contribution of the organic phase of nacre to the overall toughness of those sea shells?

Homework -8: Due: Wednesday, March 31 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper, with your own hand-writing;

“Teamwork” is strictly forbidden..)

Try your best in providing a precise and a fully balanced answer for each question, in “your own words.”

Do NOT directly copy & paste from internet.

1.) What is the difference between a “high solubility material” and a “bioresorbable material?”

Answer: When one speaks about high solubility materials, the dissolution is meant to occur when that material is placed into a solvent (for example, water). On the other hand, bioresorption will only take place by the combined action of cells and the physiological fluids present in the living tissues.

2.) What is the difference between a “biopolymer” and a “synthetic polymer produced for biological applications?”

Answer: Biopolymers are the polymeric constituents of the living tissues, they are not man-made or synthetic. Synthetic polymers, on the other hand, are made by us, they are artificial. Synthetic polymers may not be as successful, in terms of their in vivo performance, as the biopolymers, but the biomaterials researchers are working hard to develop and synthesize artificial polymers which could mimic the biopolymers.

3.) Prepare a detailed report on how to determine the tensile strength of a polymer fiber to be used in biomedical applications.

Answer: The following weblinks will give you a strong idea on how to determine the tensile strength of fibers. If you would still have questions about this procedure, please see me.

http://www.matweb.com/reference/tensilestrength.aspx

http://www.zwick.com/en/applications/metals/wire-cable/tensile-test-on-wire.html

http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_tc_browse.htm?commid=49272

4.) Under which general circumstances one may observe a severe inflammatory (and, therefore, undesired) response to an implanted synthetic biomaterial?

Answer: Problems encountered (after implantation) with the synthetic biomaterials generally occur in terms of their biocompatibility. If the synthetic material (whether metallic, ceramic, glass or polymeric) is not fully biocompatible, then the host tissues (into which the biomaterial was implanted) will exhibit an inflammatory response to it. Accurate evaluation of the cytotoxicity of any synthetic biomaterial, prior to its implantation, will become quite important in this respect. If the synthetic biomaterial is degrading or resorbing at the implantation site, the degradation or resorption products could be cytotoxic, then such a material will receive an inflammatory response in the long run. In that case, one must refer to the Parts 13, 14, 15, 16 and 17 of the ISO 10993 standard. Parts 5, 10 and 11 of this standard also discuss and reveal such cases and the relevant testing procedures.

Reading assignment – 11: Glass-and-Medicine

Tensile strength values of some materials

Homework -9: Due: Wednesday, April 7 @ 2 pm class session

(Homeworks should always be answered on a clean sheet of paper using your own hand-writing;

“Teamwork” is strictly forbidden..)

Try your best in providing a fully balanced answer for each question, in “your own words,” by using the “Glass and Medicine” paper.

1.) How can you explain the origin of the bone-bonding ability of the 45S5 Bioglass?

Answer: The bone bonding ability of Bioglass (45S5) can at first be related to its unique composition, i.e., 45% SiO₂, 24.5% Na₂O, 24.5% CaO, and 6% P₂O₅. You should notice that this glass contains both CaO and P₂O₅, which are two constituents present in this glass that are easy to form a bond with the calcium phosphate phase (i.e., calcium hydroxyapatite) of the hard tissues, i.e., bones and teeth. We know that the ordinary window glasses which are devoid of P₂O₅ do not exhibit any bone-bonding ability. 45S5 glasses were also found not to cause any scar tissue formation when implanted into the natural hard tissues, and such an advantageous ‘absence’ of scar tissue formation between the implanted material and the bone would be another factor which will help us to explain the superior bone-bonding ability of these special glasses.

2.) Describe the action of Y-90 glass spheres in fighting and eventually destroying the malignant liver tumors.

Answer: Y-90 glass spheres mainly fight and destroy the malignant tumors in two ways; (i) the radioactivity they possess (with a very short half life of only about 64 hours) and (ii) by obstructing the blood vessels (i.e., embolization of the capillary blood vessels) which feed the malignant tumor. The artificial word “radioembolization” simply and adequately describes both aspects of this process.

3.) How are those Y-90 containing glass microspheres prepared; as described in the US Patent 4789501 entitled “Glass microspheres?” (You may directly refer to this patent only in answering this question.)

Answer: The following paragraph is directly copied from the above-mentioned patent.

“The glass compositions were prepared from reagent grade chemicals. Batches yielding 50 grams of glass were melted in platinum crucibles in an electric furnace at the approximate temperatures (as specified in this patent). A typical melting cycle required three hours for batch additions at 1000 C. and three to four hours to refine the melt at the approximate melting temperature. The crucible containing the melt was quenched in 25 C. water, after which the resultant glass frit was broken from the crucible and ground to -100 mesh. The -100 mesh glass powder was then slowly fed by a vibrating spatula into an oxygen/propane flame where surface tension pulled the molten particles into spheres. The flow rates of oxygen and propane were adjusted for each glass composition so as to yield the highest fraction of spherical particles. After spheroidizing, the microspheres were wet screened with deionized water, rinsed in acetone and dried.”

A new article: “Atoms made visible”

Homework -10: Due: Wednesday, April 21 @ 2 pm (you can return your homeworks to the Department secretary)

(Homeworks should always be answered on a clean sheet of paper using your own hand-writing;

“Teamwork” is strictly forbidden..)

Try your best in providing a fully balanced answer for each question by using the “Glass and Medicine” paper.

1.) The following sentence is directly from the above paper: “There are very few cells in the bones of older individuals that are capable of dividing and forming new bone.” How can you explain this sentence, in your own words, by also using Figure 2 of the same paper? (Note: You must write a page as the answer to this question.)

Answer: This is one of the very interesting and hard-to-solve problems the human metabolism exhibits; after a certain age, people will not be able to enough bone cells which will make their bones to continue healthy remodeling. Bone remodeling means the simultaneous resorption (mainly by the osteoclasts) of the older bone and the deposition (by the osteoblasts) of new bone, and this process takes place on a daily basis in a young and healthy adult. This perfect balance is getting destroyed, by natural aging, in favor of only osteoclasts. In other words, resorption takes place but new bone deposition does not due to the lack of healthy osteoblast cells in sufficient numbers. As depicted in Figure 2, healthy osteoblasts proliferate and eventually transform and differentiate into osteocytes. Healthy osteoblasts, according to Figure 2, also produce collagen fibrils and nanosize hydroxyapatite in this process. When the proliferation of osteoblasts stops in an aged human being, this bone formation, bone deposition process stops.

2.) Did the authors of this paper summarize different ways of fighting malignant tumors? (I would like to see your own words in summarizing the views of authors printed in this paper.)

Answer: Yes, they did. The authors mentioned at the end of page 108 the three most common techniques of fighting malignant tumors, which are (i) surgery, (ii) chemotherapy and (iii) radiation or radiotherapy. The authors also wrote that none of these methods were effective enough in treating liver cancers and the 5-year survival rate for patients with the liver cancer was less than 7%. External beam radiation is used to treat many forms of cancer, but the maximum dose that can be delivered to liver cancer tumors is limited by the unavoidable damage inflicted to nearby healthy tissue and is too small to be effective. A potential solution to this problem is to place the radiation source inside the diseased tumor, called intra-arterial therapy, so that a larger dose of localized radiation can be delivered to the tumor(s) in situ without damaging the nearby healthy tissue.

3.) Table II of this paper states that bioglass was also used in toothpastes. How can one use bioglass in toothpastes? Explain in your own words.

Answer: If the bioglass is able to transform itself into apatite-like calcium phosphate (this was shown and proven in the orthopedic arena), then it could also be quite useful for use in the dental arena. Many toothpastes, today, use pure SiO₂ (just read the list of ingredients written on the boxes of toothpastes you purchase from your market) as their abrasive (for whitening the teeth) component, and using Bioglass under this light becomes a better alternative to using pure silicon dioxide (=silica). Bioglass has a proven ability to transform itself into the mineral phase of the hard tissues. It would be better to have some very tiny bioglass particles entrapped in between your teeth than pure silica particles.

4.) How can you describe, in four separate sentences, dental glass-ceramics?

Answer: You should be able to write four sentences after reading page 112 of this paper.

Homework -11: Due: Wednesday, April 28 @ 2 pm class hour

(Homeworks should always be answered on a clean sheet of paper using your own hand-writing;

“Teamwork” is strictly forbidden..)

This homework is like a review which may help you to prepare yourself for the upcoming exam.

1.) PMMA (polymethylmethacrylate) is a polymeric substance which is the main ingredient in a number of polymer-based bone cements used in fixing or glueing (by an orthopedic surgery) titanium alloy implants to the hard tissues. However, PMMA is known to be perfectly bioinert and at the same time quite strong (mechanically). The question is: how can one determine the “bone-bonding ability” of a perfectly bioinert implant material?

Answer: Mainly by performing animal (in vivo) tests. If the bone does not form a real tight bond to the implant surface (this will be judged ex vivo), then such an implant will be deemed to be bioinert.

2.) You have two questions here: (i) Would you expect the synthetic (i.e., man-made) CaCO₃ (which is the mineral part of sea shells) to display any cytotoxicity if implanted into human hard tissues?

(ii) How could you test the level of cytotoxicity of any given synthetic material?

Answer: (i) There is no reason to expect that CaCO3 will exhibit cytotoxicity.

(ii) As you already know, cytotoxicity of any given synthetic biomaterial can be easily tested by performing in vitro cell culture tests.

3.) How can you differentiate a “hydrophobic” biomaterial from a “hydrophilic” biomaterial?

Do you know any quantitative (and experimental) testing technique for evaluating the hydrophilic nature of a synthetic biomaterial?

Answer: (i) Biomaterials with hydrophobic surfaces would not be wetted by water.

(ii) Contact angle measurements (with water) would be a simple technique to evaluate the hydrophilic or hydrophobic nature of the surfaces of synthetic biomaterials.

A new element has been discovered

New research area in biomedical engineering

Cerec machines in dentistry

CEREC machines (in Turkish)

Enamel microstructure article

Soft drink damage to teeth

Dental porcelain manufacture

May 10, 2010 lecture notes

FA-collagen composites

May 12, 2010 lecture notes

PCA-maturation

Silicon in nature