Ammar's Dental Materials 11th Edition (2023-2024) PDF

# Ammar's Dental Materials ## 11th Edition (2023-2024) ### **Contents** #### **(1) Metallurgy** - Definition. - Properties of metal (8) - 1- casting - 2- Cold working - 3- Electroplating - 4- Amalgamation - 5- Sintering - Shaping of metals (5) - Soldification of metals - Methods of alterin...

# Ammar's Dental Materials ## 11th Edition (2023-2024) ### **Contents** #### **(1) Metallurgy** - Definition. - Properties of metal (8) - 1- casting - 2- Cold working - 3- Electroplating - 4- Amalgamation - 5- Sintering - Shaping of metals (5) - Soldification of metals - Methods of altering mechanical properties of alloys (4) - 1- work hardening - 2- solution hardening - 3- Precipitation hardening - 4- grain refiner - Alloys - Def - Classification - No. of alloying elements - Degree of solubility of metals in each other. - solid Solution - Def. - types & Ex. - properties - Eutectic - Def. - Example - properties - inter-metalic - Def. - Example #### **(2) Polymers** #### **(3) Composite** #### **(4) Ceramics** ### **(0) Introduction** #### **Interatomic Distance (I.A.D)** - **Definition**: It's the distance between the center of an atom and the center of its neighbor - **Factors affecting Interatomic distance:** - Temperature - Type of bond - **Covalent Bond** - Number of electrons sharing → The stronger the bond → ↑ I.A.D - → Less attraction to any specific neighboring atom ⇒ ↑ I.A.D #### **Space Lattices Materials Used In Dentistry** | **Space Lattices** | **Characters** | **Number of atoms**| **Figure** | **Examples** | |---|---|---|---|---| | **Body centered cubic space lattice (BCC)** | - A = b = c - All atoms are equidistant from each other horizontally and vertically - α = β = γ = 90° | 2 atoms per unit cell (8x)+1 | | Fe, V, Nb, Cr | | **Face centered cubic space lattice (FCC)** | | 4 atoms per unit cell (8x)+(6x) | | Al, Ni, Ag, Cu, Au | | **Hexagonal close packed space lattice (HCP)** | - A = b≠c - All atoms are equidistant from each other horizontally But not vertically - α = β = 90°, γ = 120° | 6 atoms per unit cell 2(x6)+(x2)+3 | | Ti, Zn, Mg, Cd | #### **Atomic Packing Factor (APF)** - **Definition:** It's the fraction of space occupied by the atoms. - **Calculation:** APF = Volume of atoms inside the unit cell / Volume of the unit cell - **PF for:** - SCS = 52% - BCC = 68% - FCC = 74% ### **(1) Metallurgy (Metals & Alloys)** - **Definition:** Metal is any element that ionizes positively in solution - **Properties:** - ionized positively in solution - all metals are **crystalline solids** at room temperature except **mercury, gallium** - all metals are **white** in color with different tents except **copper, gold** - metals have **high hardness, high melting temperature** (have strong primary bond) - all metals are **opaque** (have free electrons absorb the light) - metals have **good thermal, electrical conductivity** (have free electrons). - metals have **lustrous surface** (have free electron which response to light) - metals have **ability to ductility, malleability** due to (plastic deform: slippage or dislocation of crystals over each other due to line imperfection) #### **Dislocation Motion & Plastic deformation** - Plastic deformation of metals occurs by - **Slip an edge dislocation** (extra-half plane of atoms) slides over adjacent plane. - if dislocation can't move, plastic deformation doesn't occur. #### **Shaping of metals** - **1- Casting:** - **Method:** Melting of the metals and pouring, it in a mold of required shape. - **Example:** mtali restoration - **2- Cold Working:** - **Method:** - formed by mechanical working on a solidified block of cast metal - the stress is applied above Y.S to produce plastic deformation. - plastic deformation occurs due to slip along the crystal planes involving dislocation movement - **3- Electroplating:** - **Method:** Using the process of electrolysis (its reverse to corrosion). - **4- Amalgammation:** - **Method:** Its formation of an alloy by mixing a liquid metal with powdered alloy. - **Example:** Dental amalgam is a mixture of mercury, silver, tin, copper & mercury (50%) - **5- Sintering (Powder Metallurgy):** - **Method:** It is an agglomeration process in presence of heat and pressure in absence of liquid result in: - bonding of powder particles - elimination of any porosity - contraction #### **Soldification of Metals** - **1- Structure during solidification (this done by two-step mechanism):** - **Nuclear formation:** when the molten metal is cooled to freezing point. - the atoms aggregate to form starting point of crystallization (nuclei of crystallization). - **Crystalization:** - As cooling continues the nuclei grow to from crystal (grains) - The growth stopped when there is contact with adjacent growing crystals - **2- Grain Boundary:** - It's the region of transition between different oriented adjacent grains. - the atoms at grain boundaries are located in distorted position to adapt the mismatch lattice orientation in the adjacent grain. - **3- Factors affecting the grain size:** - the rate of cooling the slower cooling rate the more nuclei of crystallization are formed, the smaller grains will be formed and though the greater the strength of the alloy #### **Methods of altering mechanical properties of alloy** | **Method** | **Result** | |---|---| | **Cold Working Hardening** | - Resulted in increasing the hardness, strength and decreasing ductility. - This occurs due to distortion in the space lattice leading to stoppage of dislocation. | | **Solution Hardening** | - Solid solution hardening is an increase in alloy strength through addition of different soluble elements (chromium, tungsten, cobalt, molybdenum). | | **Precipitation Hardening** | - The precipitation phase stop dislocation strength and hardness - Silver-copper system (Amalgam ) is an example | | **Grain Refiner Hardening** | - Addition of grain refining elements that have very high melting points (induim) increase nuclei of crystallization and thus increase number of grains with fine sizes which consequently increase strength of the alloy. | ### **Alloys** - **1) Definition:** It's a mixture of metals. - Pure metals are not suitable for dental applications because they are to soft, ductile so mixtures of metals are used to improve the mechanical properties. - **2) Classification of Alloys according to:** - **1. Number of alloying elements**: - bi-nary (two metals) - Ter-nary (three metals) - quarter-nary (Four metals) - **2. Degree of solubility of metals in each other:** - **Solid Solution:** - substitutional (completely soluble in each other) - interstitial (completely soluble in each other) - **Eutectic alloy:** (partially soluble in each other) - **Intermetallic compound:** (completely insoluble in each other) - **NB:** When 2 molten metals are mixed together; they usually form a solution in the molten condition, defined as a perfectly homogenous mix on the cooling such a solution becomes one of the following types | **Alloy Type** | **Characteristics** | **Example** | |---|---|---| | **Substitution solid solution** | | Solvent metal atom Solute element atom www.substech.com Making new eutectic alloys by mixing eutectic alloys Al19.5CO47.5Cr7.5 Ni25.5 Al20C080 Al19CO15Cr15Nis1 | | **Interstitial solid solution** | | Solvent metal atom Solute element atom www.substech.com Metal A Metal B Metal C Alloying 50 µm (a) Substitutional Solid Solution (b) Interstitial Solid Solution (b) Intermetallic Compound | | **Eutectic Alloys** | - they are alloys in which the two metals are partially soluble in each other. | 1. silver-copper alloy 2. lead-tin alloy 1- have melting point (so its used in soldering, welding alloys) 2- they are heterogenous so they have low tarnish. corrosion resistance 3- they have low ductility and high strength, hardness. | | **Inter-metallic alloys** | In this case the metals are completely insoluble in each other, produce heterogeneous mixture ch.ch by 2 different phases. | 1. dental amalgam alloy - Ag2Hg3 (y1) & Cu3Sn (2) Different phases. 1- have melting points 2- Low Tarnish, Corrosion resistance. 3- they have brittle & have high strength, hardness. | - **1- Solid solution alloys (No chemical bond formation)** - **1. substitutional solid solution** - they are alloys in which the atoms of dissolved metals are completely soluble in each other to produce a perfectly homogenous alloys so the grains of alloy resemble those of pure metals. - **2. interstitial solid solution** - in which 2 different types of atoms are distributed substitutionally in the same space lattice - **1. gold-cupper alloy.** - **2- Eutectic Alloys** - in which the very small atoms occupy the interatomic space bt large atoms - **1. Iron-carbon alloy.** (steal alloy) - **3- Inter-metallic alloys** - (chemical bond formation) - In this case the metals are completely insoluble in each other, produce heterogeneous mixture ch.ch by 2 different phases | **Alloy Properties** | **Solid Solution Alloys** | **Eutectic Alloys** | **Inter-metallic alloys** | |---|---|---|---| | **Melting Point** | they have melting range rather than melting point | 1- have melting point (so its used in soldering, welding alloys) | 1- have melting points | | **Homogeneity** | they are homogenous | 2- they are heterogenous | 2- Low Tarnish, Corrosion resistance | | **Tarnish/Corrosion Resistance** | they resist tarnish, corr | so they have low tarnish | | | **Strength/Hardness** | they have high ductility & low strength, hardness | 3- they have low ductility and high strength, hardness | 3- they have brittle & have high strength, hardness | - **→ condition of formation of substitutional solid solution** :- - atomic size of two metals differ by less than 15% - 2 metals don't react with each other as in intermetallic solution - two metals must have the same space lattice ### **Periodic table of elements:** - subdivided into metals (blue backgrounds), metalloids (purple backgrounds), and nonmetals (yellow backgrounds). - Elements in non-bolded type are used in dental alloys or as pure metals. - The metals are elements that ionize positively in solution and comprise the majority of elements in periodic table. - The single asterisk indicates the insertion point in the table for the lanthanide series of elements, whereas the double asterisk indicates the insertion point for the actinide series of elements ### **1- the metals are characterized by high hardness and strength due to their. Select one:** - **a-covalent bond** - b-strong interatomic 1ry bond - c-ionic bond - d-hydrogen bond ### **2-Grain refiner as Rh, Ir are added to to increase the strength of the alloy by; select one** - a- non of that - b-decreasing in grain size - **c-increasing in grain size** - d-causing distorsion to space lattice ### **3-Metals are characterized by their ductility and malleability due to the presence of their Select one:** - a- crystalline solid - b-crystalline impereftion - **c-metallic bond** - d-electon cloud ### **4-Cold working (work hardening): in which the manufacturing of the alloy results in;Select one:** - a. increasing the hardness and decrease the yield strength - b. decreasing the hardness, yield strength and increase the ductility - **c. increasing the hardness, yield strength and decrease the ductility** - d. increasing the yield strength and decrease the hardness ### **5-All of the following properties are attributed to the presence of electron cloud except; Select one:** - a. Lustrous appearance - b. Opaqueness - c. Thermal conductivity - **d. Sintering** ### **6-Metals can be shaped by these methods,,Select one or more:** - a. algamation - **b. Castin** - **c. Cold working** - **d. Ductility** ### **7-Solid solution alloys differ than Eutectic alloys in that;Select one:** - **a. They have melting range not point** - b. They have high tarnish and corrosion resistance - c. They are ductile - d. They have high strength and hardness ### **8-At room temperature all metals are solids except two are liquid; Select one or more:** - a. Gold - **b. Gallium** - c. Silver - **d. Mercury** ### **9-Solid solution alloys differ than Eutectic alloys in that;Select one:** - **a. They have high strength and hardness** - b. They have low tarnish and corrosion resistance - c. They have melting range not point - d. They are brittle ### **10- which of the following properties not associated with electron cloud.............** - a)luster - b) opacity - **c) thermal conductivity** - d) plastic deformation #### **Periodic table of elements:** H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr