Dental Materials for Maxillofacial Prosthetics

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Questions and Answers

What is the main disadvantage of HTV silicone?

Poor compatibility with adhesive systems

Poor esthetics due to opacity (correct)

Moisture sensitivity leading to gas bubbles

Less elasticity

What is the advantage of silicones over other materials?

Poor color stability

Easier to manipulate (correct)

Higher degree of toxicity

Poor thermal stability

What is the processing temperature for HTV silicone?

150°C- 200°C for about 1 hour

200°C- 250°C for about 1 hour

180°C- 220°C for about 30 min (correct)

100°C- 150°C for about 30 min

What is the advantage of RTV silicone?

Supplied as single-component materials Signup and view all the answers

What is the main application of silicones?

Maxillofacial prosthetics Signup and view all the answers

What is the disadvantage of silicones?

Poor esthetics due to opacity Signup and view all the answers

What is the main focus of maxillofacial prosthetics?

Replacement of stomatognathic and craniofacial structures Signup and view all the answers

What is the advantage of HTV silicone over RTV silicone?

Better physical properties Signup and view all the answers

Which of the following materials is NOT used for intraoral prosthetics?

Vinyl chloride polymers Signup and view all the answers

What is an ideal requirement for maxillofacial materials?

Biocompatibility and noncarcinogenic Signup and view all the answers

How do RTV silicones cure?

By evaporation of acetic acid Signup and view all the answers

Why is silicone valued for intraoral prosthetics?

Tissue tolerability and poor thermal conductivity Signup and view all the answers

What is the advantage of metallic mesh materials?

Permits granulated tissue to migrate through the mesh Signup and view all the answers

Why is tear strength important in maxillofacial prosthetics?

It is important for thin sections such as the areas surrounding the nasal and eye prosthesis Signup and view all the answers

What should maxillofacial materials be resistant to?

Various chemicals, sunlight, heat, and cold Signup and view all the answers

What is an ideal property of maxillofacial materials in terms of weight?

Light and easily retained in position Signup and view all the answers

What is the significance of percent elongation in maxillofacial prostheses?

It provides information about the flexibility of the material Signup and view all the answers

What is the preferred hardness of a maxillofacial prosthesis?

Same as the surrounding facial structure Signup and view all the answers

Why is water sorption important in maxillofacial prostheses?

It affects the color perception of the prosthesis Signup and view all the answers

Why is it important for a maxillofacial prosthesis to be lightweight?

It improves the retention of the prosthesis Signup and view all the answers

What is the advantage of polymethyl methacrylate in maxillofacial prostheses?

It is compatible with most of the adhesive systems Signup and view all the answers

What is a disadvantage of polyvinyl chloride and copolymers in maxillofacial prostheses?

They are susceptible to degradation or destruction by UV light Signup and view all the answers

What is an advantage of polyurethane elastomers in maxillofacial prostheses?

They have good stability and higher tear resistance Signup and view all the answers

What is a desirable property of a maxillofacial prosthesis material?

Dimensional stability Signup and view all the answers

Study Notes

Maxillofacial Prosthetics

Branch of prosthodontics concerned with restoration and/or replacement of stomatognathic and craniofacial structures with prosthesis due to acquired and congenital defects of the face.

Classification of Maxillofacial Prosthetic Materials

Two main groups: extra oral prosthetic materials and intraoral prosthetic materials.

Extra Oral Prosthetic Materials

Include vinyl chloride polymers, poly (methyl methacrylate), silicone, and polyurethane.
Used for facial prosthetics.
Silicones and polyurethane are considered most desirable for their strength.

Intraoral Prosthetic Materials

Include silicones, poly (methyl methacrylate), Vitallium, and Titanium mesh materials.
Silicone is valued for its tissue tolerability.
Metallic mesh materials permit granulated tissue to migrate through the mesh.

Ideal Requirements for Maxillofacial Materials

Biocompatibility (non-irritating, non-carcinogenic).
Strength: strong enough to endure peripherally.
Flexibility: flexible at temperatures from 4.4°C to 60°C.
Chemical and environmental stability: resistant to various chemicals and environmental factors.
Thermal conductivity: poor conductor of heat.
Ease of processing and ease of duplication.
Weight: light and easily retained in position, comfortable for the patient.
Easy to sterilize.

Physical and Mechanical Properties of Maxillofacial Materials

Tear strength: important in thin sections, such as nasal and eye prosthesis.
Ultimate Tensile Strength and Percent (Maximum) Elongation: indicates flexibility.
Hardness or resistance to abrasion.
Water Sorption: affects physical properties, including color perception.
Weight: lightweight for patient comfort and retention.

Materials for Construction of Maxillofacial Prosthesis

Acrylic Resins

Polymethyl methacrylate was used for facial defects with little movement.
Advantages: compatible with adhesive systems, good strength, color stability, easy to reline and repair.
Disadvantages: rigidity, discomfort.

Polyvinylchloride and Copolymers

Clear, tasteless, and odorless material.
Advantages: adaptable to intrinsic and extrinsic staining.
Disadvantages: susceptible to degradation by UV light, ozone, and peroxide, relatively rigid, and require plasticizers.

Polyurethane Elastomer

Advantages: good stability, high tear resistance, low modulus without plasticizers, good ultimate strength and elongation, accepts intrinsic coloration.
Disadvantages: poor color stability, poor compatibility with adhesive systems, and moisture sensitivity.

Silicones

Most successful maxillofacial prosthetic material.
Advantages: excellent tear and tensile strength, easier to manipulate, chemically inert, low toxicity, and high thermal and chemical stability.
Can be stained intrinsically and/or extrinsically for a lifelike appearance.

High Temperature Vulcanized (HTV) Silicone

Heat-vulcanized silicones for maxillofacial prostheses.
Advantages: excellent tear strength, highest tensile strength, excellent thermal, colour and chemical stability.
Disadvantages: poor esthetics due to opacity, less elasticity, technique sensitive.

Room Temperature Vulcanizing (RTV) Silicone

Room-temperature-curing silicones supplied as single-component materials.
Cure by evaporation of acetic acid.
Prostheses are polymerized by bulk multiple packing.

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Description

This quiz covers the materials used in maxillofacial prosthetics, including their classification and applications in constructing maxillofacial prostheses.