LCTE Quiz & Flashcards for Dental Materials

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Questions and Answers

What is the primary function of a matrix in restorative dentistry?

To prevent gingival overhang

To confine the restoration during setting (correct)

To provide optimal surface texture for restoration

To provide proper proximal contact and contour

Which of the following is an ideal requisite for a matrix in restorative dentistry?

Rigidity (correct)

Flexibility

Reactivity

Complexity

What is the classification of matrices based on transparency?

Clear and cloudy matrices

Transparent and opaque matrices (correct)

See-through and non-see-through matrices

Reflective and non-reflective matrices

Which type of matrix is mechanically retained?

Ivory matrix retainer no. 1 Signup and view all the answers

What is the main purpose of an anatomic/custom-made matrix in restorative dentistry?

To displace the gingiva and rubber dam Signup and view all the answers

Which matrix serves the purpose of being self-retained?

Automatrix Signup and view all the answers

What was the main reason for the disappointing clinical performance of the initial formulations of composite restorations in the late 1960s?

Large, irregular filler particles with low filler content by weight Signup and view all the answers

Which of the following was NOT a shortcoming of early composite restorations?

High flexural strength Signup and view all the answers

Which mechanical property of composites depends on the fillers used?

Elastic modulus Signup and view all the answers

What is the typical filler content by weight in hybrid composites?

80% - 90% Signup and view all the answers

What type of filler particles are typically found in hybrid composites?

Microlevel particles with glass range of 1 - 3 micrometers Signup and view all the answers

Which of the following is a common issue associated with early composite restorations?

Marginal breakdown Signup and view all the answers

Which factor affects the smoothness and polishability of composite materials?

Filler size and composition Signup and view all the answers

What do nanohybrid and nanofill composites provide in terms of surface textures?

Polishable and esthetically satisfying surfaces Signup and view all the answers

What is the Linear Coefficient of Thermal Expansion (LCTE) a measure of?

Dimensional change of a material per unit change in temperature Signup and view all the answers

What is the main function of the resin matrix in composite materials?

Forms a continuous phase and binds the filler particles Signup and view all the answers

How does bonding a composite to etched tooth structure help reduce negative effects?

By matching the LCTE of the composite and tooth structure Signup and view all the answers

Which of the following is a reinforcing particle used in composite resins according to the text?

Quartz Signup and view all the answers

What effect does water absorption have on a restorative material?

It changes the material's properties and reduces effectiveness Signup and view all the answers

What is the purpose of using Barium, Strontium, Zirconium, and zinc glasses in composite resins?

Radiopacity Signup and view all the answers

How are filler contents related to water absorption in materials?

Higher filler contents lead to lower water absorption Signup and view all the answers

What factor affects the wear resistance of a material?

Size, shape, and content of filler particles Signup and view all the answers

Why do restorations near gingival tissues require surface smoothness?

For optimal gingival health Signup and view all the answers

What does hue in color refer to?

The intrinsic quality or shade of color Signup and view all the answers

What primarily contributes to the chroma of a tooth?

Dentin Signup and view all the answers

What happens to the value as chroma increases?

Value decreases Signup and view all the answers

Which part of the tooth has the thinnest enamel according to the text?

Cervical area Signup and view all the answers

How are canines different from central and lateral incisors in terms of hue?

Canines are more reddish Signup and view all the answers

Why are older teeth generally more reddish according to the text?

Loss of enamel thickness and opacity Signup and view all the answers

Study Notes

Primary Functions and Requisites of Matrices

A matrix in restorative dentistry provides a temporary boundary for dental materials to restore the tooth's shape and function.
Ideal requisites for a matrix include adaptability, rigidity, and the ability to maintain the desired form during the curing process.

Classification and Types of Matrices

Matrices can be classified based on transparency into opaque, translucent, and transparent types.
Mechanically retained matrices are typically bands or other rigid forms that are secured in place during the restoration process.
Anatomic or custom-made matrices are designed for precise fit, allowing for optimal restoration of the tooth anatomy.

Early Composite Restorations

Initial formulations of composite restorations in the late 1960s displayed disappointing clinical performance due to inadequate adhesion and wear resistance.
Shortcomings of early composites included poor polishability, marginal leakage, and lack of wear resistance.
The mechanical property of composites that depends on the fillers used is strength and elasticity.

Hybrid Composites

Hybrid composites typically have a filler content by weight of around 70% to enhance strength and durability.
These materials usually contain a mix of filler particle types, including spheroidal, irregular, and fine particles.
Common issues with early composite restorations include discoloration, wear, and poor bonding to tooth structure.

Properties and Performance of Composites

Smoothness and polishability of composite materials are influenced by the size and distribution of filler particles.
Nanohybrid and nanofill composites provide enhanced surface textures that improve aesthetics and reduce plaque accumulation.
The Linear Coefficient of Thermal Expansion (LCTE) measures how much a material expands or contracts with temperature changes.

Resin Matrix and Bonding

The resin matrix in composite materials serves to bind filler particles and affect overall mechanical properties.
Bonding composite to etched tooth structure reduces negative effects by enhancing retention and minimizing microleakage.

Filler Particles and Water Absorption

Reinforcing particles in composite resins include silica, glass fibers, and other inorganic materials.
Water absorption can lead to degradation of restorative materials, affecting strength and longevity.
Barium, Strontium, Zirconium, and zinc glasses are used to enhance radiopacity in composite resins, allowing for better visibility during radiographic evaluation.

Wear Resistance and Surface Smoothness

Filler content impacts water absorption, with higher filler concentrations generally leading to reduced absorption.
Wear resistance of a material is affected by its filler type, size, and percentage.
Restorations near gingival tissues require surface smoothness to prevent plaque accumulation and maintain periodontal health.

Color Properties in Dentistry

Hue in color refers to the attribute of color that allows it to be classified as red, blue, yellow, etc.
Chroma of a tooth refers to color intensity, primarily influenced by enamel thickness and dentin color.
As chroma increases, the value (lightness) typically decreases, leading to darker shades.
The thinnest enamel in a tooth is usually found at the incisal edges of anterior teeth.
Canines often exhibit a more yellowish hue compared to central and lateral incisors that have a lighter hue.
Older teeth are generally more reddish due to changes in dentin and enamel as they age.

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Description

Explore the concept of Linear Coefficient of Thermal Expansion (LCTE) in dental materials and its importance in preventing voids or openings at the junction of materials and teeth. Learn how bonding composites to tooth structure can reduce negative effects of temperature changes.

Linear Coefficient of Thermal Expansion in Dental Materials

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