INTRODUCTION TO BIOMATERIALS SCIENCE & MATERIALS STRUCTURE DASMAWATI MOHAMAD, PhD BIOMATERIALS SCIENCE WEEK
INTRODUCTION TO BIOMATERIALS SCIENCE
& MATERIALS STRUCTURE
DASMAWATI MOHAMAD, PhD
BIOMATERIALS SCIENCE WEEK
OBJECTIVES
• Students will have an ample knowledge on biomaterials science and technology to meet the challenges of modern dentistry.
• Students are capable of selecting, manipulating, and evaluating dental materials based on a scientific understanding of their structure and properties.
• Students are able to understand the reasons for clinical failure of dental materials and can critically evaluate materials reported by manufacturers and research publications.
• To cultivate an interest in biomaterials research for a development of new or improved performance of products used in dentistry.
Abbreviation: L – Lecture, P – Practical, SGD - Small Group Discussion, A, B, C, D, E, F – Students GroupsLectures: 12hrs, Practicals: 10 hrs, SGD: 2hrs, Self study: 4hrs, Total hrs per week: 28 hrs
Date 8.30 – 9.30am 9.30 – 10.30am 10.30 –11.30am 11.30-12.30 noon 2.00-3.00pm 3.00 – 4.00pm 4.00-5.00pm
Sunday21.10.07
L1: Introduction to Biomaterial Science & Material structure (Dr Dasmawati)
L2: Biological properties (Pn Suria)
L3: Physical properties & Chemical properties (Dr Dasmawati)
Self Study L4: Genotoxicity(Dr T.P. Kannan)
SGD 1:Physical properties –A,B,C,D,E,F – Dr Dasmawati, Dr Zuryati, Dr Wan Zaripah, Dr Adam, Dr Norliza Mastura, Dr Tin
Monday22.10.07
L5: Principles of Adhesion (Dr Zuryati)
L6: Mechanical properties(Dr Dasmawati)
P1: Material Testing Lab (Mechanical properties) –– D,E,F -Dr Dasmawati, En MarzukiP2: Tissue bank – A,B,C –Dr Suzinaand Mr Goh,
L7: Tissue Engineering & Stem Cell (Dr Suzina)
P1: Material Testing Lab (Mechanical properties) –A,B,C– Dr Dasmawati, En MarzukiP2: Tissue bank – D,E,F –Dr Suzina and Mr Goh
Tuesday23.10.07
L8: CAD-CAM Application of Biomaterials (Dr Zainul)
L9: Application of Bone graft & Material-Tissue Interface(Dr Noor Hayati Razak)
P3: Cytotoxicity – All students (MDL) –Pn Siti Fadilah, Cik Eda and En Marzuki
L10: Ceramics(Dr Norhayati Luddin)
P4: Dental Tech.Lab (Porcelain Coping) – A,B,C- Tn Hj AbdullahP5: Dental lab ((Maxillofacial Prosthesis Materials)) – D,E,F –Tn Hj Abdullah
Wednesday24.10.07
L11: Alloy (Dr Wan Zaripah)
L12: Polymers & Composites (Dr Dasmawati)
P4: Dental Tech.Lab (Porcelain Coping) – D,E,F- Tn Hj Abdullah
P5: Dental lab (Maxillofacial Prosthesis Materials) – A,B,C – Tn Hj Abdullah
5th Student Scientific Conference Rehersal
Thursday25.10.07 5th Student Scientific Conference
Lectures outlinePart I: Introduction of Biomaterials Science:• Characteristics of biomaterials• What subjects are important to biomaterials science ?• Biomaterials in dentistry• History of biomaterials in dentistryPart II: Materials Properties:• Atomic arrangement• Bonding• Composition• Defect
Characteristics of Biomaterials• Definition of Biomaterials: a non-living material designed to interact
with biological systems• Three main areas of use of biomaterials;
– Dental restoratives materials, e.g. metallic & composite filling materials, and casting alloys and ceramics for fixed and removable intraoralprosthesis
– Structural implants, e.g. oral and maxillofacial implants and joint prostheses
– Cardiovascular implants, e.g. catheters, prosthetic heart valves and blood vessels
Characteristics of Biomaterials• Multidisciplinary
– Bring together researches from diverse academic background
– e.g.; bioengineer, chemist, chemical engineer, electrical engineer, mechanical engineer, materials scientist, biologist, microbiologist, physician, veterinarian, ethicist, nurse, lawyer, regulatory specialist and venture capitalist
• Many diverse materials– Biomaterials can be polymers, ceramic, metals,
composite or many different synthetic and modified natural materials
• Development of new materials
What subjects are important to Biomaterials Science ?
• Biocompatibility• Possible adverse effects of the
biomaterials• Mechanical and performance requirement• Ethics
– A wide range of ethical considerations impact biomaterials science
Biocompatibility• Definition: ability of a material to obtain an appropriate biological
response in a given application in the body• Depends on the condition of the host, the properties of the material• Biological response in the dental environment
- biological interfaces with dental materials; dentin-resin interfaceand the implant-bone interface- for dentin-resin interface if the resin material does not penetrate the collagenous network a gap will form resulting in leakage, thus alter the biocompatibility of the restoration. May allow bacteria to reach the pulp and cause infection and also may encourage the breakdown of the material.
• How to measure biocompatibility?- for new biomaterial involved three phases of testing; primary (in vitro), secondary (in vivo), and usage - eg; in vitro;cytotoxicity, genotoxicity tests
Possible adverse effects of the biomaterials
• Toxicity, inflammation, allergy, mutagenicity-Toxicity-dose related potential of a material to cause
cell or tissue death-Inflammation- involves the activation of the host’s
immune system to fight off some threat. It may result from toxicity or allergy
-Allergy- occurs when the body specifically recognizes a material as foreign and reacts disproportionately to the amount of the material present
-Mutagenicity- result when the components of a material alter the base-pair sequences of the DNA in cells.
How safe are dental restorative materials?• Munksgaard (1992) concluded, occupational risks in dentistry
are low and the patient risk for side effects of dental treatment is extremely low.
Mechanical and performance requirement
• In dentistry, need to know how well the materials used are able to withstand the forces generated from the action of mastication and occlusion
• Studied done to determine the biting force. Guinness Book of Records (1994)-the highest biting force as 4337 N sustained for 2 sec. Average maximum biting force is approx. 756 N.
• Hence, in designing of a dental prosthesis, strength is the important factor. The ability of the prosthesis to resist induced stress without fracture or permanent deformation. (will be discussed later)
Biomaterials In Dentistry• Historically, variety of materials have been used as tooth
crown and root replacements including, animal teeth, bone, human teeth, ivory, seashells, ceramics and metals.
• An ideal restorative material would be– Biocompatible– Bond permanently to tooth structure or bone– Match the natural appearance of tooth enamel, dentin and other
tissues– Exhibit properties similar to those of tooth enamel, dentin and
other tissue– Be capable of initiating tissue repair or regeneration of missing
or damage tissues
Biomaterials In DentistryCan be classified into three categories:1. Preventive materials
Eg. pit and fissure sealants, sealing agents that prevent leakage, liners, bases, GIC
2. Restorative materialsconsist of all synthetic components that can be used to repair or replace tooth structure. Eg. primers, bonding agents, cements, resin composites, amalgam, compomers, ceramics, denture polymers
3. Auxiliary Materialssubstances that are used in the process of fabricating dental prostheses and appliances but that do not become part of these devices. Eg. impression materials, casting investments, gypsum cast, dental waxes, bleaching tray.
History of Biomaterials In Dentistry
First gold filling
Etruscan goldbridge work
Ivory dentures
Proposal of the use of porcelain by Fauchard
The use of silver and mercury to make a paste for filing teeth is suggested by Taveou of Paris
1st dental journal is published, American Journal of Dental Science
Amalgam war
Vulcanite is invented by Charles Goodyear
1st cement, zinc phosphate to set in the mouth is introduced
Silicate cements are developed
Detailed study of the properties of amalgams is published by G.V. Black
Practical method of casting gold inlays
Acrylic resin for fillings & dentures is introduced
Acid etch technique is discovers by Buonocore
Composites begin to replace silicate cements
GICs are invented by A. Wilson
Light activated composites appear on the market
Horn introduced resin bonded ceramic veneer
Development of DBA
Introduction of resin-modified glass ionomercements
1st
compomersappear on the market
600BC
AD1480
1500s1728
1826 1839 18501840s 19761879 18951880s 19701955
1950s19071985
198819831978 1994
DENTAL MATERIALS
METALS CERAMICS POLYMERS COMPOSITES
Implants, Restoratives, Wires
Restoratives,Crowns
Dentures Restoratives, Adhesive
Atomic Arrangement• Crystalline structures
– Arrangement of its neighbouring atom is identical– Space lattice- any arrangement of atoms in space in
which every atom is situated similarly to every other atom.
– Dental amalgam, cast alloys, wrought metals, gold foil, pure ceramics (alumina, zirconia) are crystalline
– Dental porcelains consist of noncrystalline glass matrix and cystalline
– Many metals used in dentistry is in cubic arrangement, one of 14 possible lattice types. Body centered cubic (BCC), face centered cubic (FCC) Lattice types depend on length of three unit cell edges and the angles between the edges.
– Packing factor; BCC = 0.68, FCC = 0.74
Atomic ArrangementMetal Atomic diameter
(angstroms)Crystal structure
Gold 2.882 Face-centered cubic
Platinum 2.775 Face-centered cubic
Palladium 2.750 Face-centered cubic
Silver 2.888 Face-centered cubic
Copper 2.556 Face-centered cubic
Tin 3.016 Body centeredtetragonal
Zinc 2.665 Close-packed hexagonal
Silicon 2.351 Diamond cubic
Atomic Arrangement
• Non-crystalline structures– Amorphous form- no symmetry of the atoms– Do not have definite melting temperature, however
they gradually soften as the temperature increase and there is an abrupt increase in the thermal expansion coefficient indicating increase of molecular mobility at certain temperature known as glass transition temperature, Tg.
– Below Tg, the glassy structure– Eg. Dental resins have a glassy structures
Bonding
Bonding is the cohesive forces that hold atoms together and classified as primary and secondary.
Primary Bonding: • Ionic bonds• Covalent bonds• Metallic bonds
Primary Bonding: Ionic Bonds• Ionic Bonds are forces that hold ionic compounds together • Following is the example of sodium chloride (Na+Cl-)
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Primary Bonding: Covalent bonds• H2 is an example of covalent bonding. The single valence electron in each
H is shared with that of the other combining atom, the valence shells become stable.
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• Octet Rule (Lewis) - an atom other than hydrogen tends to form bonds until it is surrounded by eight valence electrons
• The Bond order describes the bond1 = single, 2 = double, 3 = triple- A single bond is formed when 1 pair of electrons is shared - A double bond is formed when 2 pairs of electrons are shared- A triple bond is formed when 3 pairs of electrons are shared
• Covalent bonding occurs in many organic compounds, including dental resins
• Example in quartz and diamond
Primary Bonding: Metallic Bonds• results from the increased spatial extension of valence-electron wave functions when an aggregate of metal atoms is brought close together.• e.g. a metallic crystal such as pure gold. Easily donate electrons from their valence shell. A cloud of electrons will form surrounds the atoms.
Secondary Bonding-do not share electrons-resulting from electrical imbalance known as an electric dipole.
• Van der Waals forces– Short-range force of physical attraction that promotes
adhesion between molecules of liquids or molecular crystals
• Hydrogen bonding– Dipole-dipole interaction. Eg. A water molecule– Associated with the positive charge of H caused by
polarization. When a water molecule intermingles with other water molecule, the H (+ve) portion of one molecule will attracted to the O (-ve) portion of its neighbouring molecule, formed hydrogen bridges.
Bonding: Bond distance– Liming factor that prevents
the atoms or molecules from approaching each other too close
– If the atoms approach too close, they are repelled from each other by their electron charges. On the other hand, forces of attraction tend to draw the atoms together.
– The position at which forces of attraction and repulsion become equal in magnitude is the equilibrium positions of the atoms, interatomic distance a.
Bonding: Bond energy– Amount of energy that
has to be supplied to separate the two atoms
– Generally, covalent bonds the strongest, followed by the ionic bonds, then metallic bonds
Bonding
• In general,– Ceramics- based on the ionic bond– Metals- metallic bond– Molecular solids (polymers)- based on the
covalent and secondary bonds