بسم الله الرحمن الرحيم مذكرة شاملة لمادة BIOMATERIALS — من الرابطة الذرية إلى تصنيف المواد الحيوية 8 محاضرات كاملة تغطي كامل مقرر المادة.
8محاضرات كاملة
240سؤال MCQ بالشرح
🧩 كل محاضرة عبارة عن:
📖 الشرح — شرح مفصّل يغطي كل نقطة في المحاضرة
🔤 التعريفات — تعريف واضح ومباشر لكل مصطلح ومفهوم
📊 جدول مقارنة — يقارن بين المفاهيم المتشابهة لتسهيل الحفظ
⭐ أهم النقاط — 10 إلى 15 نقطة مركّزة للمراجعة السريعة
🧩 اختبار MCQ — 30 سؤال لكل محاضرة، مع شرح ليه الإجابة صح وليه الباقي غلط
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الاشتراك في المذكرة
مذكرة BIOMATERIALS 🎯
150 جنيه / مرة واحدة فقط
الحمد لله، قدرنا نوصّل ليك المحتوى ده بعد وقت طويل من التعب والمجهود والمراجعة — مش بس تجميع معلومات، ده شغل حقيقي من الأول للآخر. 💪
كل محاضرة اتبنت من الصفر: شرح مفصّل يغطي كل نقطة في المقرر، تعريفات واضحة لكل مصطلح، جداول مقارنة تساعدك تربط المعلومات، أهم النقاط للمراجعة السريعة، واختبار MCQ تفاعلي بـ 30 سؤال لكل محاضرة مع شرح الإجابة الصح والغلط — كل ده في موقع واحد، بتصميم احترافي، يشتغل على أي موبايل أو لابتوب.
فضلاً عن الوقت، فيه تكاليف حقيقية وراء الموقع ده — وحاولنا مع كل ده إن السعر يفضل بسيط ومناسب للجميع، لأن هدفنا الأول إنك تذاكر صح وتنجح بإذن الله. 🎯
نسأل الله السداد والتوفيق، وأن يكون في ميزان حسناتنا جميعاً. 🤲
وبنحب نوضح إننا لسنا منصة تعليمية ولا بنقدم كورسات — نحن فقط مجموعة من الزملاء حاولنا نقدم المعلومة بطريقة منظمة وسهلة. السعر ده ببساطة هو تكلفة الموقع اللي بيخليك تلاقي كل حاجة في مكان واحد بشكل احترافي — مش أكتر من كده. 🖤
8
محاضرات كاملة
240
سؤال MCQ بالشرح
🧩 كل محاضرة عبارة عن:
📖 الشرح — شرح مفصّل يغطي كل نقطة في المحاضرة
🔤 التعريفات — تعريف واضح ومباشر لكل مصطلح ومفهوم
📊 جدول مقارنة — يقارن بين المفاهيم المتشابهة لتسهيل الحفظ
⭐ أهم النقاط — 10 إلى 15 نقطة مركّزة للمراجعة السريعة
🧩 اختبار MCQ — 30 سؤال لكل محاضرة، مع شرح ليه الإجابة صح وليه الباقي غلط
خطوات الاشتراك
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بيوصل خلال دقائق بإذن الله 🎉
Atomic Building Blocks & Structural Arrangement of Atoms
🔬 Atomic Building Blocks — All materials are built from atoms and molecules
Types of Atomic Bonding
A. Primary Bonds (Strong · Chemical · Irreversible): 1. Ionic | 2. Covalent | 3. Metallic
B. Secondary Bonds (Weak · Physical · Reversible): 1. Hydrogen Bond | 2. Van der Waals Forces
🏗️ Structural Arrangement of Atoms in Solid Materials
i. Crystalline: Regular arrangement — Long-range order — Definite melting point — 14 Bravais Lattices — Unit cell
ii. Amorphous (Non-crystalline): Random distribution — Short-range order — Glass Transition Temperature (Tg) — Examples: glass, wax
⚠️ Important — Tg: Glass Transition Temperature is where a non-crystalline material begins to soften — and where the Coefficient of Thermal Expansion (CTE) rises sharply.
Atom
The basic unit of any material. All materials are built from atoms and molecules.
Valence electrons
Electrons in the outermost shell — responsible for chemical bonding.
Ionic bond
Formed by transfer of electrons → electrostatic attraction between + and − ions. Example: NaCl. Dental use: Glass & Ceramics.
Covalent bond
Formed by sharing of electrons. Example: H₂O, CH₄, Acrylic resin. Dental use: Polymers.
Metallic bond
Free electron cloud around positive ion cores. Explains conductivity, opacity, and lustre. Dental use: Dental alloys.
Hydrogen bond
Secondary weak bond — attraction between dipoles of adjacent molecules. Example: between H₂O molecules.
Van der Waals forces
Secondary weak bond — temporary fluctuation in electron distribution creates transient dipoles. Example: Chemisorption in liquid alloys.
Crystalline
Atoms arranged in a regular, repeating 3D pattern — Long-range order — definite melting point — 14 Bravais Lattices.
Amorphous (Non-crystalline)
Atoms randomly distributed — Short-range order — no definite melting point — softens gradually at Tg. Example: Glass, wax.
Unit cell
The smallest repeating unit of a crystal lattice.
Bravais Lattices
14 possible ways to arrange lattice points in 3D space.
Glass Transition Temp (Tg)
Temperature at which non-crystalline material begins to soften on heating — also where CTE rises sharply.
Electrostatic attraction
Attraction between positive and negative ions — the basis of ionic bonding.
Opacity & Lustre
Properties of metallic bond: free electrons absorb incident light (opacity) and reflect some of it (lustre).
Bonding of similar materials by atomic/molecular attraction. Example: two gold pieces joined under pressure (metallic bond).
Adhesion
Bonding of dissimilar materials by atomic/molecular attraction.
Adhesive
A liquid or thin material added to produce adhesion between two surfaces.
Adherend
The solid material to which the adhesive is applied.
Adhesive junction
The transition layer between the adhesive and the adherend.
Macro-mechanical retention
Visible to the naked eye — examples: lateral undercuts, screws, pins.
Micro-mechanical retention
Not visible to the naked eye — example: acid etch technique for composite resin.
Surface energy
Higher energy of surface atoms compared to bulk atoms, because surface atoms are not equally attracted in all directions.
Surface tension
Attractive force between atoms/molecules at the surface of a liquid.
Wettability
The ability of a liquid to spread over a solid surface.
Contact angle (θ)
Angle formed between the solid surface and the tangent to the curved liquid surface — the true measure of wetting. θ < 90° = good wetting; θ > 90° = poor wetting; θ = 0° = perfect wetting.
Viscosity
Resistance of a liquid to flow. Low viscosity = better flow = better adhesion.
Surfactant
A substance that reduces surface tension and improves spreading.
Adhesive failure
Fracture at the adhesive-adherend interface.
Cohesive failure
Fracture within the adhesive or adherend material itself — indicates adhesion was stronger than the material.
COOH group (Carboxyl)
Reacts with calcium in tooth structure to form a true chemical bond — the basis of GIC and ZPC bonding to teeth.
Acid etch technique
Phosphoric acid creates microscopic pores in enamel for micro-mechanical retention of composite resin.
Color Matching Methods: Shade Guide — VITA Classic (by Hue) | VITA Pan 3D Master (by Chroma)
💡 Value: Most important color parameter in dentistry — represents tooth vitality. Non-vital teeth: low value → gray appearance.
💡 Fluorescence: Natural teeth emit blue-white light (400–450 nm) under UV radiation (300–400 nm). Dental porcelain contains cerium oxide (fluorescing agent). Acrylic resin has no fluorescing agent → appears as a missing tooth under black light.
Hue
The dominant wavelength of light — the basic color (e.g., red, blue, green).
Value
Degree of lightness or darkness of a color — THE MOST IMPORTANT parameter in dentistry. Represents tooth vitality (non-vital tooth has low value → appears gray).
Chroma
Degree of saturation/intensity of a particular hue.
Opacity
Prevents all light passage — no object can be seen through the material. Example: metals.
Translucency
Allows some light to pass while scattering the rest — objects seen unclearly. Example: dental enamel, dental ceramics.
Transparency
Allows complete light passage without distortion — objects seen clearly. Example: glass.
Metamerism
Phenomenon where colors appear to match under one light source but differ under another → color matching must be done under at least two light sources (one being sunlight or white light).
Fluorescence
Ability to absorb light of a certain wavelength and re-emit it at a longer wavelength. Natural teeth emit blue-white (400–450 nm) under UV light (300–400 nm).
Opalescence
Reflects short wavelengths (blue) and transmits long wavelengths (yellow-red) — as seen in dental enamel and high-esthetic ceramics.
Cerium oxide
Fluorescing agent added to dental porcelain to replicate natural tooth fluorescence (not present in acrylic resin).
Shade guide
Tool containing samples at various Hue, Value, and Chroma levels to match tooth color. Disadvantage: color perception varies between individuals.
VITA Classic
Shade guide arranged by Hue.
VITA Pan 3D Master
Shade guide arranged by Chroma.
Pigmentation
Incorporation of metal oxides into dental materials (composite, acrylic) for aesthetic color effects.
📊 Light Transmission Properties
Property
Opacity
Translucency
Transparency
Light passage
None
Partial (rest scattered)
Complete, undistorted
Object visibility
Impossible
Unclear
Clearly visible
Example
Metals
Dental enamel, ceramics
Glass
13 color parameters: Hue (dominant wavelength/color), Value (lightness/darkness — most important clinically), Chroma (saturation/intensity).
2Non-vital tooth appears gray due to low value.
3Metamerism: colors match under one light source but differ under another → match under 2 sources, one being sunlight/white light.
4Fluorescence: natural teeth emit blue-white light (400-450 nm) when excited by UV (300-400 nm).
5Cerium oxide is added to dental porcelain (not acrylic) to reproduce natural fluorescence.
6Opacity: no light passes. Translucency: partial light passes, scattered (e.g. enamel). Transparency: full light passes without distortion (e.g. glass).
7Opalescence: reflects shorter (blue) wavelengths, transmits longer (yellow-red) wavelengths — used in porcelain veneers for natural depth.
8Rough surfaces appear lighter & less chromatic — they reflect more white light that dilutes the material's true color.
9VITA Classic shade guide = arranged by hue. VITA Pan 3D Master = arranged by chroma/value.
10Shade guide limitation: color perception varies between observers.
11Pigmentation is achieved by incorporating metal oxides as colored pigments into resins/acrylics.
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Lecture 05
Mechanical Properties
Stress-Strain Curve (Universal Testing Machine) — Slope of linear portion = E (Elastic Modulus) | Area under elastic portion = Resilience | Total area = Toughness
💡 Tear Strength: Rate-dependent — rapid loading ↑ tear strength. Therefore, alginate impressions should be removed with a rapid snap to maximize tear resistance and avoid tearing in thin sections.
Stress (σ)
Internal reaction to external force = Force / Area (F/A). Unit: Pascal (N/m²).
Strain (ε)
Change in length per unit length (ΔL/L). Dimensionless (no unit).
Elastic deformation
Reversible deformation — material returns to original dimensions after stress removal (stretching of atomic bonds).
Plastic deformation
Irreversible deformation — material does not return to original dimensions (breaking and rearrangement of atomic bonds).
Proportional / Elastic Limit (PL/EL)
Maximum stress without any permanent deformation — end of the linear portion of the stress-strain curve.
Yield Stress (YS)
Stress at which the material begins to behave plastically.
Ultimate Strength (US)
Maximum stress the material can withstand before fracture.
Fracture Strength (FS)
Actual stress at which fracture occurs.
Elastic Modulus (E)
Slope of the linear portion = Stress/Strain. Measures stiffness/rigidity of the material.
Flexibility
Maximum elastic strain at the proportional limit. High flexibility = large elastic deformation at low stress.
Ductility
Ability to undergo plastic deformation under tension without fracture — ability to be drawn into wire.
Malleability
Ability to undergo plastic deformation under compression without fracture — ability to be hammered into thin sheets.
Brittleness
Inability to show plastic deformation — fracture occurs at or near the proportional limit (opposite of ductility).
Resilience
Resistance to permanent deformation — energy to deform the material to the PL. Area under the elastic portion of the stress-strain curve.
Toughness
Resistance to fracture — total energy to fracture. Area under the entire stress-strain curve. Requires high PL + good ductility.
Compressive strength
Maximum stress under compressive force before failure. Measured by compressing a cylinder between two flat plates.
Diametral Tensile Strength
Indirect tensile test for brittle materials only (Brazilian test) — disc compressed diametrically, external compression creates internal tension.
Flexural Strength
= Transverse strength = Modulus of rupture = Three-point bending test. Rod supported at both ends, load applied at center.
Impact Strength
Energy required to fracture under a sudden impact force. Charpy test (horizontal support) / Izod test (vertical support).
Tear Strength
Resistance to tearing forces. Rate-dependent: rapid loading ↑ tear strength. Important for elastic impression materials and maxillofacial prosthetics.
Burnishability
Ability to shape cast restoration margins under pressure — depends on ductility and malleability.
📊 Stress-Strain Curve — Key Points
Term
Definition
Dental Significance
PL / EL
Maximum stress without permanent deformation
Restorations need high PL to avoid permanent deformation under occlusal forces. Orthodontic wires and clasp arms are intentionally bent beyond EL to achieve permanent shape change.
Yield Stress
Stress at which plastic behavior begins
YS of restoration must exceed normal occlusal forces
Elastic Modulus (E)
Slope of linear portion = Stress/Strain
(1) High E for denture bases and long-span bridges → prevent flexure and ensure even load distribution. (2) Orthodontics: stiff wire (high E) = high, rapid force | flexible wire (low E) = low, slow force
Flexibility
Maximum elastic strain at PL
Impression materials need high flexibility to be withdrawn from undercuts without permanent deformation
Resilience
Area under elastic portion
Resistance to permanent deformation
Toughness
Area under the entire stress-strain curve
Zirconia, alumina, and leucite are added to dental ceramics to increase fracture toughness by impeding crack propagation
📊 Other Mechanical Properties
Property
Definition
Test Method
Dental Significance
Compressive strength
Maximum stress under compression before failure
Cylinder compressed between two flat plates until fracture
Rigid until a yield stress is reached, then flows with constant viscosity
Ketchup 🍅
🔬 Thixotropic material: A pseudoplastic material that loses viscosity under repeated pressure and regains it at rest — due to structural breakdown and reformation.
Monophase Rubber Impression — Practical Example
1
In the tray: high viscosity — material stays in tray and does not drip.
2
Through a syringe nozzle (high pressure applied): viscosity decreases — material flows easily around teeth.
🔄
2. Viscoelasticity
Definition
A phenomenon where a material exhibits a combination of both elastic and viscous properties.
🌀 Ideal Elastic — Spring
On loading: sudden, immediate deformation → stays constant
On unloading: sudden & complete recovery back to zero
Not strain-rate dependent
🛢️ Ideal Viscous — Dashpot
On loading: gradual, progressive deformation
On unloading: no recovery — permanent deformation remains
Strain-rate dependent
⚡ Viscoelastic — Universal Model (Real Materials)
On loading: ① Instantaneous (sudden) deformation ② Time-dependent, non-linear progressive strain
On unloading: ① Instantaneous recovery ② Slow (delayed) recovery ③ Permanent (plastic) deformation remains
⭐ Clinical Significance
1
Snap (rapid) removal of impression materials — shortens load application time → reduces permanent deformation → more accurate impression.
2
Allow sufficient time before model pouring — lets the viscoelastic impression material recover its accurate dimensions.
🔩
3. Creep (Flow / Sag)
Definition & Conditions
Creep = Time-dependent plastic strain (deformation) in a material subjected to a constant stress below its yield strength.
Clinical Examples
💡 Most metals & alloys do NOT exhibit creep at mouth temperature (high melting points). Amalgam is the only exception.
🎯
4. Stress Relaxation
Definition
Stress Relaxation = Reduction in stress in a material subjected to constant strain over time.
Orthodontic Elastics Comparison
⚡
5. Fatigue
Key Definitions
S-N Curve & Clinical Significance
📈 S-N Curve (Stress vs. Number of cycles):
↑
↑ Stress → ↓ number of cycles to fracture
↓
↓ Stress → ↑ number of cycles to fracture
⭐ Clinical Significance:
Restorations must be designed so that masticatory stresses remain below the Endurance Limit to prevent cumulative fatigue fracture.
📊
Master Comparison Table
❓
MCQ — 30 Questions
✍️
Written Questions (5) + Answers
Flow
The spread of a material over a surface under pressure or its own weight.
Viscosity (η)
Resistance of a fluid to flow = Shear Stress ÷ Strain Rate; measured in MPa/s or centipoise (cp).
Newtonian Fluid
A fluid with constant viscosity — a linear relationship between shear stress and shear rate (e.g. water).
Pseudoplastic (Shear-Thinning)
A fluid whose viscosity decreases as shear rate increases (e.g. monophase rubber impression).
Dilatant (Shear-Thickening)
A fluid whose viscosity increases as shear rate increases (e.g. fluid denture-base resin).
Thixotropic Material
A pseudoplastic material that loses viscosity under repeated pressure and regains it at rest.
Viscoelasticity
A phenomenon where a material exhibits a combination of both elastic and viscous properties.
Creep
Time-dependent plastic deformation in a material under constant stress below its yield strength, near its softening temperature.
Stress Relaxation
Reduction in stress in a material subjected to constant strain over time.
Fatigue
Progressive fracture of a material under repeated cyclic loading.
Endurance Limit (Fatigue Limit)
The maximum stress that can be applied for an infinite number of cycles without fracture.
Term
Definition
Unit
Flow
Spread of a material over a surface under pressure or its own weight
—
Viscosity (η)
Resistance of a fluid to flow = Shear Stress ÷ Strain Rate
MPa/s or cp
Application
Viscosity Required
Why?
Cementation
⬇️ Low (High flow)
Must spread beneath the crown
Filling materials
⬆️ High
Must stay in place
Impression materials
Moderate
Must record fine oral details
Factor
Non-setting Materials
Setting Materials
⬆️ Pressure
Both: ↑ pressure → ↑ flow → ↓ viscosity
⏱️ Time
Independent of time
Viscosity ↑ with time (progressive setting)
🌡️ Temperature
↑ temp → ↓ viscosity
↑ temp → ↑ viscosity (↑ reaction rate)
Condition
Details
Stress
Constant and below the Yield Strength
Temperature
Near the softening temperature of the material
Material
Reason
Consequence
Dental Amalgam
Contains Hg with a melting point slightly above mouth temperature + constant masticatory forces
2Viscosity (η) = shear stress ÷ strain rate. Cementation needs LOW viscosity; filling materials need HIGH viscosity.
34 fluid types: Newtonian (constant η, e.g. water), Pseudoplastic/shear-thinning (↑rate→↓η), Dilatant/shear-thickening (↑rate→↑η), Plastic (needs yield stress to flow).
4Thixotropic material: pseudoplastic that loses viscosity under pressure and regains it at rest.
5Viscoelasticity = combination of elastic (spring, instant full recovery) + viscous (dashpot, no recovery) behavior.
6Snap removal of impressions minimizes permanent deformation; waiting before pouring lets viscoelastic recovery complete.
7Creep = time-dependent plastic strain under constant stress BELOW yield strength, near the softening temperature.
8Amalgam is the only metal that creeps at mouth temperature (Hg melting point close to body temp) → marginal breakdown → microleakage → secondary caries.
9Metal sag in PFM bridges = creep from porcelain weight + high firing temperature near the metal's melting point.
10Stress relaxation = ↓ stress at CONSTANT strain over time. Latex band (slow decay) preferred over plastic band (rapid decay) in orthodontics.
11Fatigue = progressive fracture under repeated CYCLIC loading (not a single overload).
12Endurance limit = max stress for infinite cycles without fracture; restorations should be designed to stay below it.
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Lecture 08
General Classes of Biomaterials
General Classes of Biomaterials
Dental biomaterials are generally categorized into four classes:
⚙️
Metals
e.g. Amalgam, Alloys
🧪
Polymers
e.g. PMMA, Silicones
💎
Ceramics
e.g. Porcelain Crowns
🔬
Composites
Combination of 2+ classes
⚠️ One class — Composites — is a combination of two or more classes.
1
⚙️ Metals
Properties of Metals
At room temperature, all metals are crystalline solids — except Mercury & Gallium (liquid at room temperature).
Good thermal and electrical conductivity — due to free electrons.
Opaque and lustrous (shiny).
High hardness and melting temperature — due to strong primary inter-atomic bond (metallic bond).
Good ductility and malleability — due to crystalline imperfections (dislocations) which allow slippage of crystals over each other.
White in color — except Copper (reddish) and Gold (yellow).
Shaping of Metals
1️⃣ Casting — Melting the metal/alloy and shaping it in a mold of the required shape.
2️⃣ Cold Working — Shaping a solidified cast metal by mechanical working (rods, wires, tubes…). Stress is applied above the yield strength.
3️⃣ Powder Metallurgy (Sintering) — Bonding of solid powder particles by heat & pressure in the absence of any liquid.
4️⃣ Amalgamation — Mixing a liquid metal with a powdered alloy. Dental amalgam = Mercury + Silver + Tin + Copper → strong, hard, durable direct filling.
★
🔩 Alloys
Why Alloys?
Pure metals are too soft and ductile for dental applications.
Mechanical properties are improved by using mixtures of metals = Alloys.
An alloy = a mixture containing 2 or more metals.
Classification 1 — According to Number of Alloying Elements
Classification 2 — According to Degree of Solubility
Types of Solid Solution
⚠️ Conditions for Substitutional Solid Solution: (1) Atomic size difference <15% | (2) Same type of crystal lattice | (3) Metals do not react with each other
Properties of Solid Solution Alloys
Have melting ranges rather than a melting point.
Homogeneous → resist tarnish and corrosion.
High ductility, but low strength & hardness compared to other alloy types.
Properties of Eutectic Alloy
Have a fixed melting point.
Heterogeneous → low tarnish and corrosion resistance.
Brittle, but high strength & hardness.
2
🧪 Polymers
Key Definitions
Polymer — Long chain molecules consisting of many repeating small units (monomers). Poly = many, Mer = monomer unit. e.g. Poly Methyl Methacrylate (PMMA)
Monomer — The smallest repeating unit in the polymer chain.
Homopolymer — Polymer formed of one type of monomer.
Copolymer — Polymer formed of 2 or more types of monomers.
Classification 1 — According to Spatial Configuration
Classification 2 — According to Thermal Behavior
Polymerization Process
Process of forming a polymer from monomers.
Polymerization is never entirely complete → remaining unconverted monomer = Residual Monomers.
Residual monomers cause irritation of soft tissues and hypersensitivity.
Types of Polymerization Reactions
3
💎 Ceramics & Glasses
Definition & Composition
Inorganic materials processed by firing at high temperature.
Have ionic or covalent bonding and tightly packed structures.
Composed of a glassy matrix (amorphous) + crystalline phase (e.g. Al₂O₃, ZrO₂).
Unlike metals and polymers, ceramics are brittle and difficult to shear plastically due to the ionic nature of bonding and minimum number of slip systems.
Cracks within ceramics act as stress raisers — the stress at the crack tip can be many times higher than the surrounding stress → stress concentration → weakens the material.
Advantages vs. Disadvantages
4
🔬 Composite Materials
Definition & Advantage
Composites = combination of two or more classes of materials.
Advantage: fabricate a new material with desirable properties not achievable with one material alone.
Dental example: Composite Restoration.
⊞
📊 Full Comparison Table
Alloy
A mixture containing 2 or more metals, used to improve on the poor mechanical properties of pure metals.
Solid Solution Alloy
A fully-soluble, homogeneous alloy with a melting range, high corrosion resistance, high ductility, but low strength/hardness.
Eutectic Alloy
A partially-soluble, heterogeneous alloy with a fixed melting point; brittle but high strength/hardness.
Intermetallic Compound
A completely insoluble, heterogeneous alloy that is very hard but very brittle.
Polymer
A long-chain molecule made of many repeating small units (monomers).
Monomer
The smallest repeating unit in a polymer chain.
Homopolymer / Copolymer
A polymer formed from one type of monomer (homopolymer) or 2+ types (copolymer).
Thermoplastic Polymer
A polymer that softens reversibly on heating and hardens again on cooling (e.g. Impression Compound).
Thermosetting Polymer
A cross-linked polymer that does NOT soften again once set (e.g. Impression Silicones).
Residual Monomer
Unconverted monomer remaining after incomplete polymerization; causes soft-tissue irritation and hypersensitivity.
Ceramic
An inorganic material processed by firing at high temperature, composed of a glassy matrix plus a crystalline phase.
Composite
A combination of two or more material classes, giving properties not achievable by any one class alone.
Type
Number of Metals
Binary
2
Ternary
3
Quaternary
4
Type
Solubility
Microstructure
Melting
Hardness
Corrosion Resistance
Example
Solid Solution
Fully soluble
Homogeneous
Range (not a point)
Low
High
Gold–Copper
Eutectic Alloy
Partially soluble
Heterogeneous
Fixed melting point
High
Low
Lead–Tin / Silver–Copper
Intermetallic Compound
Completely insoluble
Heterogeneous
—
Very High
Very Brittle
—
Type
Description
Conditions / Example
A. Substitutional
Two different atom types distributed substitutionally in the same crystal lattice.
Atomic size difference <15% | Same crystal lattice type | No chemical reaction | Ex: Gold–Copper
B. Interstitial
Atoms of one metal (much smaller) occupy the interatomic spaces of the larger atoms.
Large difference in atomic size | Ex: Iron–Carbon (Steel)
Type
Description
Notes
A. Linear
Separate and discrete straight chains.
—
B. Branched
Separate chains with side branches.
—
C. Cross-linked
Network structure — may become one giant molecule.
Stronger, harder, more rigid. Flow at higher temperatures. Don't absorb liquids as easily.
Property
Thermoplastic
Thermosetting
Structure
Linear or branched
Cross-linked
On heating
Softens → can be shaped → hardens on cooling (Reversible)
Does NOT soften again on reheating (Irreversible)
Solubility in organic solvents
Soluble
Not soluble
Abrasion resistance
Lower
Higher
Dimensional stability
Less
More
Dental example
Impression Compound
Impression Silicones
Type
By-products?
Dental Example
1. Condensation Polymerization
Yes (e.g. water)
Polysulphide Impression
2. Addition — Free Radical
No
Composite Resin
3. Addition — Ring-Opening
No
Polyether Impression
Advantages ✅
Disadvantages ❌
Inertness & Biocompatibility
Brittleness
High compressive strength
Susceptibility to notches or cracks
Pleasing aesthetic appearance
Low tensile strength
—
Low impact strength
Property
⚙️ Metals
🧪 Polymers
💎 Ceramics
🔬 Composites
Bond Type
Metallic
Covalent
Ionic / Covalent
Mixed
Hardness
High
Low
Very High
Medium–High
Ductility
High
Medium
Brittle
Medium
Aesthetics
Poor
Medium
Excellent
Good
Corrosion Resistance
Medium
Low
High
Good
Electrical Conductivity
Excellent
Insulator
Insulator
Medium
Dental Example
Amalgam, Crowns
Denture base, PMMA
Porcelain crowns
Composite resin
14 classes of dental biomaterials: Metals, Polymers, Ceramics, Composites (a combination of 2+ classes).
2All metals are crystalline solids at room temperature EXCEPT Mercury & Gallium (liquid).
3Metal properties: high conductivity, opacity/lustre, high hardness/melting point (from metallic bond), good ductility/malleability (from dislocations).
44 metal shaping methods: Casting, Cold Working (stress above yield strength), Powder Metallurgy/Sintering (heat+pressure, no liquid), Amalgamation (Hg + powdered alloy).
5Alloys improve on pure metals (too soft/ductile alone): Binary (2 metals), Ternary (3), Quaternary (4).
6Solid Solution (fully soluble, melting range, high corrosion resistance) vs Eutectic (partially soluble, fixed melting point, brittle but hard) vs Intermetallic Compound (insoluble, very hard & brittle).
7Substitutional solid solution needs <15% atomic size difference & same lattice type (e.g. Gold-Copper). Interstitial: small atoms fit between larger ones (e.g. Iron-Carbon/Steel).
9Cross-linked polymers = stronger/harder/more rigid than linear/branched, and absorb less liquid.
10Thermoplastic = softens reversibly on heating (e.g. Impression Compound). Thermosetting = does NOT soften again once set (e.g. Impression Silicones).
113 polymerization types: Condensation (releases by-product, e.g. water), Addition-Free Radical (no by-product, e.g. Composite Resin), Addition-Ring-Opening (no by-product, e.g. Polyether).
12Ceramics = glassy matrix + crystalline phase; brittle due to ionic bonding & minimum slip systems; cracks act as stress raisers.
13Composite advantage: combines desirable properties not achievable by any single material class alone.