Composite Materials in Dentistry

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Questions and Answers

What was the primary issue with early acrylic materials developed in the 1930s?

Lack of popularity in dentistry

Poor activator systems (correct)

Poor color stability

Limited application scope

What was a notable limitation of self-curing acrylic resins for dental restorations?

Low strength

High wear (correct)

Difficult to manipulate

High processing cost

Which year marked the introduction of a polymeric dental restorative material reinforced with inorganic particles?

1975

1940

1962 (correct)

1930

What are composite restorations primarily known for?

Aid in the restoration of contour and contacts Signup and view all the answers

What kind of injuries could arise from using acrylic resins in dental restorations?

Pulp injury Signup and view all the answers

What does the classification of composites NOT include?

By aesthetic properties Signup and view all the answers

Which of the following is not a consequence of using unfilled acrylic resins?

High elasticity Signup and view all the answers

What characteristic distinguishes composite materials from their individual components?

Altered characteristics when combined Signup and view all the answers

What effect does light condensation have on spherical alloy?

Enhances compressive strength Signup and view all the answers

Which of the following ranges represents the modulus of elasticity for low copper amalgam?

20-50 GPa Signup and view all the answers

What is creep in the context of dental amalgam?

Time-dependent deformation under load Signup and view all the answers

How does high copper amalgam compare to low copper amalgam in terms of creep?

Has lower creep Signup and view all the answers

What property of a material does dimensional change refer to?

Changes in original shape and dimensions Signup and view all the answers

What is the modulus of elasticity range for enamel?

50-80 GPa Signup and view all the answers

Which composition factor increases creep in low copper amalgam?

Presence of $ ext{γ}^2$ phase Signup and view all the answers

Which amalgam type exhibits higher stiffness?

High copper amalgam Signup and view all the answers

What is essential for achieving the desired bond when using tooth-colored restorations?

Isolation of the operative field Signup and view all the answers

What is a consequence of saliva contamination on etched enamel or dentin?

Decreased bond strength Signup and view all the answers

Which method can be used for isolation in tooth-colored restorations?

Cotton rolls Signup and view all the answers

What is a primary characteristic of dental amalgam as a restorative material?

High strength and excellent wear resistance Signup and view all the answers

What is a significant negative aspect of dental amalgam restorations?

Aesthetic limitations Signup and view all the answers

Which of the following is crucial during the polishing process for restorations?

Employing consistent shapes and abrasiveness in tools Signup and view all the answers

Which statement about dental amalgam is true?

It is a mixture of silver-tin-copper alloy and mercury. Signup and view all the answers

In restoring teeth, why is proper occlusal contact important?

It ensures proper function and wear resistance of the restoration. Signup and view all the answers

What is the initial tooth preparation depth for the pulpal floor?

1-2 mm Signup and view all the answers

What is the main purpose of retention form in dental preparation?

To prevent dislodgment of restoration along the path of insertion Signup and view all the answers

What does resistance form ensure in dental restorations?

Stability against apical or oblique forces Signup and view all the answers

Which of the following is NOT an auxiliary means to enhance retention form?

Aesthetically pleasing shapes Signup and view all the answers

How thick should primary tooth preparation depth be at a minimum?

1.5-2 mm Signup and view all the answers

What is the function of cove in primary retention form?

To help prevent dislodgment Signup and view all the answers

What is the recommended angle for the pulpal and gingival walls during preparation?

Perpendicular to occlusal forces Signup and view all the answers

Which of the following features is incorporated into the tooth preparation as part of the outline form?

Undercut form Signup and view all the answers

What is the effect of decreased salivary production on caries susceptibility?

It increases caries susceptibility. Signup and view all the answers

What role does professional tooth cleaning play in dental health?

It controls biofilm and prevents disease. Signup and view all the answers

How does high-frequency exposure to fermentable carbohydrates affect biofilm?

It promotes the production of cariogenic biofilm. Signup and view all the answers

What happens to biofilm growth when fermentable carbohydrates are severely restricted?

Biofilm growth typically does not lead to caries. Signup and view all the answers

What is the purpose of careful mechanical cleaning of teeth?

To disrupt biofilm and prepare a clean surface. Signup and view all the answers

Which of the following statements is true about the environmental factors contributing to caries?

Diet and oral hygiene are key ecological determinants. Signup and view all the answers

What is a key characteristic of the protective proteins in saliva?

They maintain a consistent presence at uniform levels. Signup and view all the answers

What outcome is unlikely when professional tooth cleaning is performed?

A complete eradication of dental diseases. Signup and view all the answers

What characteristic distinguishes root caries lesions from enamel caries lesions?

Root caries tend to be U-shaped in cross-section. Signup and view all the answers

What is a typical sign of active caries on enamel?

Rough surface that can be chipped away Signup and view all the answers

What is the estimated time frame for the progression from non-cavitated enamel caries to clinical caries?

18 months ± 6 months Signup and view all the answers

Which substance plays a critical role in the remineralization process of carious lesions?

Calcium and phosphate ions Signup and view all the answers

What is the appearance of remineralized caries lesions clinically?

Intact but discolored, usually brown or black Signup and view all the answers

What should clinicians consider before restoring remineralized caries lesions?

Whether they are esthetically unacceptable Signup and view all the answers

Where are the earliest signs of caries usually observed on teeth?

On the facial and lingual surfaces Signup and view all the answers

What is identified as non-cavitated enamel caries?

Chalky white, opaque areas Signup and view all the answers

Study Notes

Composite Restoration

Composite restorations are a type of dental restoration that is developed with inorganic particles
Used to resolve issues present in earlier acrylic resins like polymerization shrinkage and thermal expansion
Marginal leakage is a common consequence of unfilled acrylic restorations, making them unsuitable for permanent restorations

Dental Composite Material

Definition: A material made from two or more components with different physical or chemical properties to form a new material with different characteristics
Components:
- Matrix: Initiators
- Filler: Accelerators
- Coupling Agent: Pigments
- Continuous Phase (Resin Matrix):
- Dispersed Phase (Filler):
Classification (based on filler size):
- Macrofilled (conventional): 75-80% inorganic filler, approximately 8 µm particle size, susceptible to discoloration due to rough surface texture.
- Microfilled: Introduced in the late 1970s, designed for smooth surfaces similar to tooth enamel, colloidal silica particles (0.01-0.04 µm), 35-60% by weight, wear resistant, appropriate for restoring cervical lesions.
- Hybrid: Combines characteristics of microfilled and macrofilled, smaller average particle size (0.4-1 µm), 75-85% by weight, superior physical and mechanical properties than conventional composites.
- Nanofilled: Extremely small filler particles (0.005-0.01 µm), high filler levels resulting in good physical properties and improved aesthetics, highly polishable.

Dental Amalgam

Definition: A metallic restorative material composed of a silver-tin-copper alloy and mercury. Used to restore tooth structure (cavity repair).
Advantages: Ease of use, high strength, excellent wear resistance, low cost, and satisfactory long-term clinical research results.
Disadvantages: Non-esthetic, less conservative (more removal of tooth structure), non-insulating, more difficult tooth preparation, and environmental concern (mercury).
Classification (based on particle shape):
- Spherical: Easier to carve, less proximal contact.
- Lathe-cut: More proximal contact, more difficult to carve for some clinicians.
- Admix: Combines advantages of spherically and lathe-cut amalgam.
Classification (based on copper content):
- Low copper alloy: Lowest compressive and tensile strength.
- High copper alloy: Higher compressive and tensile strength.
Classification (based on zinc content):
- Zinc containing: More than 0.01% Zn
- Zinc free: 0.01% or less Zn

Glass Ionomer Restoration

Definition: A water-based material formed by an acid-base reaction between a basic calcium-fluoro-alumino-silicate glass powder and an aqueous poly-acid solution.
Composition:
- Acid-soluble glass powder (alumina and silica).
- Poly-acid liquid (polyacrylic acid co-polymerized with organic acids like maleic, itaconic, and tartaric acids).
Setting Reaction: Acid attack on glass powder, followed by gelation (initial setting), and maturation and hardening (final setting).
Properties:
- Biocompatible, resistant to bacterial plaque due to fluoride release, low setting contraction and good bonding,
- Low wear resistance, moisture sensitive, short working time and long setting time.

Dental Caries

Definition: A multifactorial, infectious, transmissible oral disease leading to localized tooth calcified tissue dissolution and destruction.
Etiology: Cariogenic bacteria metabolize carbohydrates to generate organic acids that cause demineralization of the tooth enamel below a critical pH value.
Factors Affecting Caries:
- Primary Modifying Factors: Tooth anatomy, diet, oral hygiene, fluoride use, immunity, genetic factors
- Secondary Modifying Factors: Socioeconomic status, education, lifestyle, environment, occupation, salivary dysfunction
Lesion Definitions: Smooth-surface, pit-and-fissure, occlusal, proximal, enamel, dentin, coronal, root, primary, secondary, residual, active, inactive

Matrix and Wedging

Matrix: A properly contoured metal or material used to support and form restoration during placement and setting.
Wedging: Used to create space between teeth and hold matrix properly in place.
Types of Matrix Bands:
- Metal bands that can be used for both circumferential and sectional matrices.
- Plastic bands like Mylar are often used for anterior procedures.
Types of Wedges: Wooden or plastic, either straight or anatomically shapes.

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Description

This quiz explores the development and characteristics of acrylic and composite materials used in dental restorations. It includes questions on historical advancements, limitations, and classifications relevant to dental composites. Test your knowledge about the evolution and implications of these materials in dentistry.