Materials in Dentistry

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Questions and Answers

What defines a polymer?

A material made of large molecules formed from repeating units called monomers (correct)

A simple molecule that cannot be broken down further

A synthetic material composed entirely of metals

A material formed from small molecules connected by ionic bonds

Which type of bond is primarily responsible for the structure of polymers?

Hydrogen bonds between chains

Ionic bonds within the polymer chain

Van der Waals forces between molecules

Covalent bonds between monomers (correct)

Which of the following is NOT a dental application of polymers?

Cements

Composite filling materials

Metal implants (correct)

Impression materials

What is the characteristic of polar bonds in polymers?

They contribute to low strength and high water sorption Signup and view all the answers

What describes a random copolymer?

Monomers mixed in a relatively random manner along the polymer chain Signup and view all the answers

Which polymer is derived from methyl methacrylate?

Poly-methyl methacrylate (PMMA) Signup and view all the answers

What advantage do polymers offer over metals in dental materials?

Lightweight and flexibility Signup and view all the answers

Which of these is an example of a net advantage of using composite materials?

They provide superior aesthetic results Signup and view all the answers

What characterizes a graft copolymer?

It consists of a main chain with one or more side chains of another monomer attached. Signup and view all the answers

Which effect is NOT associated with extensive cross-linking in polymers?

Increased ductility Signup and view all the answers

How does the molecular weight (M.W) of a polymer affect its properties?

Higher M.W results in a higher melting range and increased stiffness. Signup and view all the answers

What is the clinical significance of polymerization?

Incomplete polymerization can lead to irritation of soft tissues. Signup and view all the answers

Which type of polymerization results in low shrinkage?

Addition polymerization Signup and view all the answers

What is a common characteristic of linear copolymers?

They consist of monomers connected in a sequential manner. Signup and view all the answers

Which of the following is a characteristic of cross-linked polymers?

They exhibit a three-dimensional network structure. Signup and view all the answers

What does condensation polymerization create as a by-product?

A smaller molecule such as water or alcohol Signup and view all the answers

What initiator is used in the polymerization process to generate free radicals?

Benzoyl peroxide Signup and view all the answers

What is a key characteristic of thermoplastic polymers?

They can be reshaped upon heating. Signup and view all the answers

Which factor is NOT associated with the polymerization process?

Volume expansion Signup and view all the answers

What causes the inhibition of polymerization?

Presence of impurities in the monomer Signup and view all the answers

During which step of the polymerization reaction does the chain reaction theoretically continue until all monomers are converted to polymers?

Propagation Signup and view all the answers

What is a common example of a thermoplastic polymer?

Non-cross linked PMMA Signup and view all the answers

What is the significance of adding inhibitors to monomers during storage?

To prevent polymerization and extend shelf life Signup and view all the answers

What effect does polymerization typically have on the temperature of the reaction environment?

It generates heat as the reaction is exothermic. Signup and view all the answers

Which advantage is primarily associated with brittle materials?

High compressive strength Signup and view all the answers

What is a characteristic disadvantage of ionic materials?

Low impact strength Signup and view all the answers

Which material feature primarily contributes to creep behavior?

Covalent microstructure Signup and view all the answers

Which of the following is NOT an advantage of composite polymers?

Polymerization shrinkage Signup and view all the answers

What is a common disadvantage of materials with a crystalline microstructure?

Creep and sag Signup and view all the answers

Which feature is a disadvantage associated with the various components of composite polymers?

Tendency to discoloration Signup and view all the answers

Which of the following is a property of metalic materials in composite polymers?

Strong and stiff Signup and view all the answers

What is a primary factor that limits the performance of brittle materials?

Susceptibility to micro-cracks Signup and view all the answers

What type of bonding primarily holds the chains in thermosetting polymers?

Primary covalent bond Signup and view all the answers

How do thermosetting polymers behave upon reheating?

They decompose at high temperatures Signup and view all the answers

Which of the following is a characteristic property of composites?

Ability to control material properties Signup and view all the answers

What is a notable disadvantage of composite materials?

Tendency to discoloration Signup and view all the answers

Which of the following materials is primarily used in making dental crowns and bridges?

Ceramics and glasses Signup and view all the answers

What type of bond is primarily found in feldspar?

Ionic bond Signup and view all the answers

Which of the following is true about thermosetting polymers?

They have high abrasion resistance Signup and view all the answers

What is the primary phase that remains unchanged during the firing process in ceramics?

Crystalline phase Signup and view all the answers

Study Notes

General Classes of Materials (Lecture 2)

The lecture covers Polymers, Composites, and Ceramics
The material includes a variety of dental applications for each class

Metallurgy

This section discusses the basic properties of metals
Includes types of bonds, and applications in dentistry

Polymers

Definition: Polymers are large molecules made from smaller molecules called monomers linked together through covalent bonding
Types of Bonds:
- Covalent bonds hold monomers together within the polymer chain
- Polar/Hydrogen bonds exist between polymer chains
Nature/Structure: Polymers can be linear, branched, or cross-linked
- Polymers are often amorphous or show partial crystallinity degrees
Dental Applications:
- Impression materials (e.g., alginate, elastomers)
- Composite filling materials
- Cements (e.g., glass ionomer, zinc polycarboxylate)
- Acrylic denture base and artificial teeth
- Soft lining materials
Co-polymers: Polymers formed from a mixture of monomers

Composites

Definition: Composites are a combination of two or more materials with different properties.
Uses: Sealants, veneers, restorations, core buildup, cements, and denture teeth
Properties: Intermediate properties
- Moderate hardness and stiffness
- Thermal and electrical insulation
- Formable, and machinable
- Opaque or translucent

Ceramics

Definition: Ceramics are inorganic, non-metallic, solid materials made from metal and non-metal oxides.
Properties:
- High hardness, melting temperature, modulus of elasticity
- Insulating qualities and chemical inertness
- Brittle
Dental Applications:
- Crowns, bridges, inlays
- Onlays, and other restorations

Polymerization

Definition: A process where monomers chemically bond together to form polymers.
Types:
- Addition polymerization: Monomers link together with no by-product (free radicals or ionically)
- Condensation polymerization: Monomers link together with a byproduct (water, alcohol)
- Rapid in addition polymerization

Thermal Behavior of Polymers

Thermoplastic Polymers:
- Linear or branched structure
- Reversible, soften with heat, and harden with cooling
Thermosetting Polymers:
- Cross-linked structure
- Irreversible chemical reaction
- Do not resoften after curing

Factors Associated with Polymerization

Heat Evolution: Polymers release heat during polymerization
Shrinkage: Change in volume during polymerization
Residual Monomers: Unreacted monomers remain after polymerization.

Inhibition of Polymerization

Impurities and oxygen: Prevent polymerization by inhibiting further growth

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Description

This quiz covers various classes of materials used in dentistry, including polymers, composites, and ceramics. It highlights their properties, types of bonds, and specific dental applications such as impression materials and filling materials. Assess your understanding of these materials and their significance in dental practices.

Materials in Dentistry - Lecture 2

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