77 Questions
What is the basic unit of internal structure for materials?
Atom
Which particles are found in the nucleus of an atom?
Protons and neutrons
What is the role of valence electrons in determining physical and chemical properties?
They are responsible for energetic interaction with other atoms
What does the atomic weight of an atom depend on?
The weight of protons and neutrons
Which particles in the atom have a positive charge?
Protons only
What determines the different lattice systems in crystalline structures?
Interatomic bonds
How do the physical and chemical properties of an atom depend on the electrons furthermost from the nucleus?
They affect energetic interaction with other atoms
What are the properties affected by atomic weight?
Density and specific heat
What is the role of neutrons in the nucleus of an atom?
They are unchanged particles
What determines the atomic number of an element?
The number of protons.
What is the primary reason for the formation of ionic bonds?
Obtaining extra electrons to complete the outer shell and becoming negatively charged
Which type of bond leads to a high electrical and thermal conductivity?
Metallic bond
What is the primary characteristic of covalent bonds?
Strong and highly directional
Which type of bond is responsible for the attraction between positive and negative ions?
Ionic bond
What is the reason for the formation of secondary bonds (Van der Waals forces)?
Polarization of molecules leading to weak attraction
Which characteristic is associated with metallic bonds?
High electrical and thermal conductivity
What is the primary characteristic of amorphous solids?
Without shape and having random arrangement of atoms
In which type of solid are the atoms regularly arranged in a space lattice?
Crystalline solids
What is the primary classification criterion for unit cells in space lattices?
The length of their axes and interfacial angles
What is the main reason for the formation of a covalent bond?
Sharing electrons so that the outer shell of two or more atoms is complete
What is the primary role of valence electrons in the formation of primary bonds?
Completing the outer electron shell
Which type of bond arises when atoms share their electrons to achieve an inert gas structure?
Covalent bond
What is the primary characteristic of amorphous solids?
Random arrangement of atoms
What is the main factor responsible for the high electrical and thermal conductivity in metallic bonds?
Free movement of electrons through the metal
Which type of bond arises from the attraction between positive and negative ions?
Ionic bond
What determines the atomic number of an element?
The number of protons in the nucleus
What is the primary classification criterion for unit cells in space lattices?
The length of their axes (a, b, c)
What is the primary reason for the formation of secondary bonds (Van der Waals forces)?
Polarization of molecules leading to weak forces
What is the role of neutrons in the nucleus of an atom?
Balancing the charge inside the nucleus
What is the primary classification criterion for unit cells in space lattices?
Arrangement of atoms
What determines the different lattice systems in crystalline structures?
Arrangement of atoms
Which type of bond is responsible for the attraction between positive and negative ions?
Ionic bonds
In which type of solid are the atoms regularly arranged in a space lattice?
Crystalline solid
What is the basic unit of internal structure for materials?
Atom
What is the primary characteristic of metallic bonds?
Delocalized electrons
What determines the atomic number of an element?
Number of protons
What is the primary characteristic of covalent bonds?
Sharing of electrons
How do the physical and chemical properties of an atom depend on the electrons furthermost from the nucleus?
They affect both physical and chemical properties
What is the role of valence electrons in determining physical and chemical properties?
They determine both physical and chemical properties
Which dental material has the highest thermal conductivity?
Gold alloys
What is the specific heat of dentin compared to that of water?
Lower
What does the rate at which a body approaches thermal equilibrium describe?
Thermal diffusivity
What is the primary factor causing marginal percolation in composite restorations?
Thermal expansion
What is the role of viscoelastic materials in dental practice?
To resist flow under external force
What is the significance of heat of fusion in the context of dental materials?
Accompanying state transitions
What is the primary effect of thermal cycling on restorations with different expansion coefficients from tooth structure?
Bond degradation between restoration and tooth
What determines the rate at which the interior surface under a dental crown is heated?
Thermal diffusivity
What are the units for density?
gm/cm3 and pound/inch3
What is the specific gravity of a material with a density of 2.5 gm/cm3?
2.5
Which dental material has the highest density?
Gold alloys
Why must upper dentures be made up of low-density materials?
To enhance the retention of the denture
What is thermal conductivity?
The quantity of heat per second passing through a body
Why are thermal properties of dental materials important?
To protect the pulp from extreme temperature differences
What happens when a patient drinks a hot beverage without dental protection?
The pulp reacts severely to the temperature difference
Which type of material would require higher pressure to fill mold cavities during casting procedures?
Materials with low density
What defines specific gravity, in terms of density?
Specific gravity is numerically equal to density, with units
'A low specific gravity material requires ___________ pressure to fill mold cavities.' Fill in the blank.
Higher
What is the unit for density of dental materials?
gm/cm3 and pound/inch3
Which material would require higher pressure to fill mold cavities during casting procedures?
Gold alloys
What is the specific gravity of a material with a density of 2.5 gm/cm3?
2.5
What is the primary factor to consider for protecting the pulp of the tooth from temperature differences?
Thermal conductivity
Which dental material has the highest density?
Gold alloys
What is the unit for thermal conductivity of a material?
watts per meter per degree Kelvin
'A low specific gravity material requires ___________ pressure to fill mold cavities.' Fill in the blank.
higher
'Density of equal volume of HO2' is used to calculate what property?
Specific gravity
What property is affected by atomic weight?
Density
Why must upper dentures be made up of low-density materials?
To aid retention
What is the thermal conductivity of zinc oxide Eugenol cement?
0.0011 cal/sec/cm2/(0C/cm)
What is the primary advantage of high thermal conductivity in metallic denture base materials?
It causes tissue stimulation through vasodilatation
What does the rate at which a body with non-uniform temperature approaches thermal equilibrium describe?
Thermal diffusivity
What does the heat of fusion of a material indicate?
The absorption or liberation of heat during state transitions
What is the primary characteristic of viscoelastic materials?
They exhibit time-dependent strain due to a combination of viscous and elastic behavior
What does the exterior thermal expansion (α) help to avoid in porcelain fused to metal (PFM) restorations?
Marginal percolation
What is the specific heat of gold compared to that of water?
$0.03 cal/gm-10C$
What is the importance of the specific heat of a metal or alloy during the melting process?
It indicates the amount of heat required to raise the temperature to the melting point.
What is most accurate about the rate at which heat flows through a material?
It determines the thermal conductivity.
What characteristic does dentin possess in terms of its thermal conductivity?
Poor conductor of heat.
Study Notes
Atomic Structure
- The basic unit of internal structure for materials is the atom.
- The nucleus of an atom consists of protons and neutrons.
- Valence electrons determine physical and chemical properties of an atom.
- Atomic weight depends on the number of protons and neutrons in the nucleus.
- Protons have a positive charge in the nucleus.
Bonding
- Ionic bonds form between positive and negative ions.
- Ionic bonds lead to a high electrical and thermal conductivity.
- Covalent bonds form when atoms share electrons to achieve an inert gas structure.
- Covalent bonds are primary bonds.
- Metallic bonds arise from the attraction between positive and negative ions.
- Metallic bonds lead to high electrical and thermal conductivity.
- Secondary bonds (Van der Waals forces) form due to the attraction between positive and negative ions.
- Valence electrons play a primary role in the formation of primary bonds.
Crystalline Structures
- The arrangement of atoms in a space lattice determines the lattice system in crystalline structures.
- Unit cells in space lattices are classified based on the arrangement of atoms.
- Crystalline structures have atoms regularly arranged in a space lattice.
Physical Properties
- Atomic weight affects physical properties such as density and thermal conductivity.
- Thermal conductivity is the ability of a material to conduct heat.
- Specific heat is the amount of heat energy required to raise the temperature of a material by 1°C.
- Density is the mass per unit volume of a material, measured in gm/cm³.
- Specific gravity is the ratio of the density of a material to that of water.
Dental Materials
- The primary factor to consider for protecting the pulp of the tooth from temperature differences is thermal conductivity.
- Upper dentures must be made up of low-density materials to reduce weight.
- The thermal conductivity of zinc oxide Eugenol cement is low.
- High thermal conductivity in metallic denture base materials is an advantage.
- Viscoelastic materials are used in dental practice due to their ability to deform and recover.
- The specific heat of dentin is lower than that of water.
- The heat of fusion of a material indicates the energy required to change its state from solid to liquid.
- The exterior thermal expansion (α) helps to avoid mismatch between porcelain and metal in PFM restorations.
Test your knowledge about the structure of matter, atomic structure, interatomic bonds, amorphous and crystalline structures, and crystalline lattices as related to dental biomaterial in the Faculty of Oral and Dental Medicine at Sinai University.
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