Dental Materials Quiz
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Questions and Answers

Which material has the highest diametral tensile strength among the options listed?

  • Aurafil (Johnson & Johnson)
  • P-30 (3M Dental Products) (correct)
  • Occlusin (ICI Dental)
  • Adaptic (Johnson & Johnson)

Which wear mechanism primarily affects non-contact areas of dental composites?

  • Corrosive wear
  • Fatigue wear
  • Three-body abrasion (correct)
  • Two-body abrasion

What is a primary misconception about the relationship between hardness and wear resistance in dental materials?

  • Hardness is a definitive measure of a material's performance.
  • High filler loadings enhance both hardness and wear resistance.
  • The relationship between hardness and wear resistance breaks down at high filler loadings. (correct)
  • Hardness always correlates with wear resistance.

What factor does NOT influence wear rates in dental materials?

<p>Environmental temperature (B)</p> Signup and view all the answers

Which statement about fatigue cracks in dental materials is correct?

<p>Fatigue cracks are a result of repeated loading and cyclic stresses. (D)</p> Signup and view all the answers

What role does the fluoro-alumino-silicate glass play in polyacid-modified resin composites?

<p>It provides filler and a source of fluoride. (C)</p> Signup and view all the answers

Which component is responsible for facilitating the transport of water and fluoride in polyacid-modified resin composites?

<p>Hydrophilic monomers (C)</p> Signup and view all the answers

What reaction primarily drives the setting process of polyacid-modified resin composites?

<p>Radical polymerization reaction (A)</p> Signup and view all the answers

Which statement distinguishes polyacid-modified resin composites from resin-modified glass-ionomer cements (RMGICs)?

<p>Compomers use composite resins as the starting material. (B)</p> Signup and view all the answers

Which of the following is a necessary condition for fluoride release from the fluoro-aluminosilicate glass in polyacid-modified resin composites?

<p>Absorption of water from the oral environment (D)</p> Signup and view all the answers

In the copolymerization process of a compomer, which component reacts with the dimethacrylate monomer to facilitate fluoride release?

<p>Carboxyl group-containing polymerizable monomer (A)</p> Signup and view all the answers

What is a potential issue with excessive radiopacity in composite materials?

<p>It can mask caries behind the restoration. (B)</p> Signup and view all the answers

Which type of discoloration is most likely caused by a gap between a restoration and tooth tissues?

<p>Marginal discoloration (C)</p> Signup and view all the answers

Which bonding technique is recommended to reduce marginal discoloration in composites?

<p>Acid-etch bonding technique (C)</p> Signup and view all the answers

When comparing the compressive strength of restorative materials, what is the compressive strength of Sybralloy (Kerr)?

<p>500 MPa (D)</p> Signup and view all the answers

What characteristic is primarily affected by the surface finish of restorative materials?

<p>Tensile strength (C)</p> Signup and view all the answers

Which restorative material would likely demonstrate the highest compressive strength based on the provided data?

<p>Occlusin (ICI Dental Products) (C)</p> Signup and view all the answers

What can cause bulk discoloration in two-paste amine-cured composites?

<p>Chemical breakdown of components (C)</p> Signup and view all the answers

What is the intrinsic water absorption of the resin estimated at?

<p>40-45 µg mm⁻³ (C)</p> Signup and view all the answers

Which material has the highest water uptake according to the data provided?

<p>P-30 (3M Dental) (D)</p> Signup and view all the answers

How does high filler loading affect the coefficient of thermal expansion in composites?

<p>It decreases the overall expansion (B)</p> Signup and view all the answers

Which composite is expected to have a higher coefficient of thermal expansion?

<p>Microfilled resins (C)</p> Signup and view all the answers

What can cause increased water absorption in composites?

<p>Short curing times (D)</p> Signup and view all the answers

Which composite has the largest differential expansion factor (D)?

<p>Delton (Johnson &amp; Johnson) (B)</p> Signup and view all the answers

What aspect does water sorption help to compensate for in composites?

<p>Polymerization shrinkage (D)</p> Signup and view all the answers

What is one negative effect of hydrolytic breakdown of the resin-filler bond?

<p>Loss of filler effectiveness (D)</p> Signup and view all the answers

What is a significant characteristic of fluoride release in compomers compared to GICs?

<p>Compomers have similar fluoride release profiles over time to GICs. (A)</p> Signup and view all the answers

Which bonding method is typically omitted when using compomers?

<p>Acid etching of enamel and dentin. (D)</p> Signup and view all the answers

How do compomers compare to composite resins in terms of mechanical properties?

<p>Compomers have inferior diametral and flexural properties. (B)</p> Signup and view all the answers

Which statement about the clinical significance of compomers is incorrect?

<p>Excessive hygroscopic expansion is not a concern for compomers. (C)</p> Signup and view all the answers

What is a limitation of compomers in clinical applications?

<p>They are only suitable for non-stressed areas. (C)</p> Signup and view all the answers

What positively influences the fluoride release from compomers?

<p>Acidic environments promoting material dissolution. (B)</p> Signup and view all the answers

What distinguishes the water uptake behavior of compomers from that of composite resins?

<p>Water diffusion through compomers occurs more rapidly. (A)</p> Signup and view all the answers

How do larger filler particles in compomers affect their properties?

<p>They may lead to lower wear resistance. (A)</p> Signup and view all the answers

Compomers' aesthetic qualities make them competitive with which material?

<p>Composite resins. (A)</p> Signup and view all the answers

What is the average particle size of small-particle hybrid composites?

<p>1 µm (D)</p> Signup and view all the answers

What is a significant advantage of using smaller filler particles in dental composites?

<p>Smoother surface finishes (A)</p> Signup and view all the answers

What size are the fillers in some modern nanocomposites, as mentioned in the content?

<p>75 nm (C)</p> Signup and view all the answers

How have the classifications of composites influenced their design?

<p>To maximize filler loading and packing density (B)</p> Signup and view all the answers

What has been a notable trend in the labeling of dental materials since the early 2000s?

<p>Incorporation of the 'nano' label in various materials (A)</p> Signup and view all the answers

What is one of the primary benefits of nanocomposites in dental applications?

<p>Improved aesthetic properties (B)</p> Signup and view all the answers

What is a role of colloidal silica in small-particle hybrid composites?

<p>To contribute to the particle size distribution (D)</p> Signup and view all the answers

What challenge accompanies the commercialization of 'nano' labeled materials?

<p>Lack of research backing (C)</p> Signup and view all the answers

What characteristic is primarily enhanced by the use of smaller filler particles in composites?

<p>Smoother surface finish (C)</p> Signup and view all the answers

How does the packing density of restorative material get increased in composite classification?

<p>By filling spaces between large particles with small particles (B)</p> Signup and view all the answers

Flashcards

Fatigue Wear

The repeated loading of teeth produces cyclic stresses that can lead to the growth of fatigue cracks.

Corrosive Wear

Chemical attack on composites, like hydrolytic breakdown of the resin-filler interface or erosion of the surface due to acid attack. This can be caused by acids or other chemicals in the mouth.

Abrasive Wear

Direct contact between two surfaces where the harder material indents or cuts away material from the softer surface. This happens when teeth move against fillings.

Wear

The process of material being removed or displaced by interfacial forces generated when two surfaces rub together. This happens when teeth move against fillings.

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Hardness & Wear Resistance

The ability of a material to resist being worn down or scratched. It is measured using different techniques.

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Radiopacity of Composites

The ability of a composite material to appear on a dental X-ray, crucial for detecting decay under fillings.

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Composite Discoloration

The mismatch in color between a composite filling and the natural tooth, causing an unsightly appearance.

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Marginal Discoloration

Discoloration at the edges of a composite filling due to debris accumulation in the gap between filling and tooth.

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General Surface Discoloration

Discoloration on the surface of a composite filling due to debris trapped in the rough surface.

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Bulk Discoloration

Discoloration throughout the entire composite filling, often yellowing, caused by chemical breakdown and absorption of fluids over time.

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Compressive Strength

The resistance of a material to crushing forces, measured in megapascals (MPa).

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Tensile Strength

The resistance of a material to pulling forces, measured in megapascals (MPa).

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What are compomers?

A tooth-colored restorative material that combines features of both resin composites and glass ionomer cements (GICs). They are essentially resin composites modified to provide a sustained release of fluoride.

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How do compomers release fluoride?

Compomers contain a special resin monomer with carboxyl groups (COOH). These groups react with the fluoro-alumino-silicate glass filler in the presence of water, releasing fluoride ions over time.

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What is the setting mechanism of compomers?

Compomers are set by a radical polymerization process triggered by blue light, similar to resin composites. However, unlike conventional composites, they also have an acid-base reaction that contributes to their setting and fluoride release.

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How do compomers differ from resin-modified glass ionomer cements (RMGICs)?

Compomers are classified as resin-based materials with modifications for sustained fluoride release. In contrast, resin-modified glass ionomer cements (RMGICs) are GICs that have been modified to improve their properties.

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What are the clinical applications of compomers?

Compomers have gained popularity in dentistry due to their combination of aesthetic appeal, strength, and fluoride release. They are primarily used for restorations in posterior teeth where fluoride release is desirable.

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What are the advantages of using compomers in dentistry?

Compomers are a good alternative for restoring teeth in areas where high fluoride release is desired, particularly in posterior teeth. They offer a balance between aesthetic appeal and the benefits of fluoride release.

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Fluoride Release in Compomers

Compomers release fluoride over time, but at a lower initial rate than GICs. Modern compomers have similar fluoride release profiles to GICs and RMGICs throughout the restoration's lifespan.

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Handling Characteristics of Compomers

Compomers are easy to handle due to their good flow and adaptation to cavity walls without sticking, making them popular among dentists.

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Adhesion of Compomers

Compomers do not naturally adhere to enamel and dentin like GICs and RMGICs. A dentin adhesive is required for bonding.

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Polymerization Shrinkage and Water Uptake in Compomers

Compomers have similar polymerization shrinkage (~2-2.5 vol %) to composite resins. However, they absorb water more rapidly, which helps offset the shrinkage.

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Mechanical Properties of Compomers

Compomers have generally lower mechanical properties (compressive, diametral, flexural) than composite resins. Their wear resistance is better than GICs and RMGICs, but still lower than composites.

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Applications of Compomers

Compomers are suitable for low stress-bearing restorations, such as proximal and erosion lesions, permanent restorations in primary teeth, and temporary restorations in permanent teeth.

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Aesthetic and Practical Advantages of Compomers

Compomers have good aesthetics and are easy to use, making them a good alternative to composite resins in certain situations.

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Clinical Performance of Compomers

Compomers show favorable results after 3-4 years of clinical use, making them a reliable option in specific cases.

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Water Uptake and its Impact on Compomer Restorations

The rapid water uptake of compomers can help reduce the formation of marginal gaps after placing the restoration, however, excessive water absorption can cause hygroscopic expansion.

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Small-Particle Hybrid Composites

Composites with very small filler particles, typically less than 1 µm in size.

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Nanocomposites

Composites with even smaller fillers, often nanoparticles around 75 nm in size.

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Composite Classification

The way composites are classified based on the size of their filler particles.

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Complementary Particle Size Distributions

Filler particles of very different sizes - big and small - are mixed in a composite to maximize the amount of filler.

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Filler Packing Density

Smaller particles fill the spaces between larger particles, resulting in denser, more stable composites.

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Smoother Surface Finishes

A smoother surface finish due to the use of smaller filler particles.

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Gloss Retention

The improved ability of nanocomposites to maintain their shine and gloss over time.

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Opacity

The ability of materials to transmit light.

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Compressive Strength of Composites

The ability of a composite material to resist crushing forces.

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Tensile Strength of Composites

The ability of a composite material to resist pulling forces.

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Water Sorption in Composites

Water absorbed by a composite material, affecting its properties like color stability and wear resistance.

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Hydrolytic Breakdown

The breakdown of the resin-filler bond in composites due to water absorption, leading to reduced filler effectiveness and increased wear.

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Water Sorption

The amount of water a material absorbs, measured in µg/mm³ (micrograms per cubic millimeter).

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Coefficient of Thermal Expansion

The measure of how a material expands or contracts with changes in temperature. Measured in ppm/°C (parts per million per degree Celsius).

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Differential Expansion Factor

The difference in thermal expansion between a composite material and tooth enamel.

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Thermal Expansion Compatibility

A composite's ability to match the thermal expansion of tooth tissue, minimizing stress and wear.

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Low Thermal Expansion Material

Materials like glass fillers that have a low coefficient of thermal expansion, meaning they expand and contract less with temperature changes.

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High Filler Loading & Thermal Expansion

Composites with higher inorganic filler loading, which exhibit lower overall thermal expansion compared to those with more resin.

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Study Notes

Radiopacity

  • Composites used as posterior restorative material have radiopacity of utmost importance for caries detection
  • Non-radiopaque composites virtually impossible for detecting caries under the restoration
  • Excessive radiopacity can potentially hinder the detection of deeper caries
  • Radiopacity of the composite is related to the surface finish
  • The presence of internal flaws (or small spaces) within the composite will affect the material's ability of radiopacity

Color Match

  • Marginal surface discoloration, bulk discoloration, and general surface discoloration are the three possible discolorations
  • Marginal discoloration is usually caused by the presence of a marginal gap between the restoration and the tooth
  • To achieve a good marginal seal, the material should be employed in an acid-etch technique
  • Employing this technique is to prevent the ingress of staining fluids from the oral environment, resulting in a highly polished surface
  • Bulk discoloration may result from the exposure of trapped air bubbles
  • To avoid this, a 7 μm paste is followed by a 1 μm paste finishing process

Mechanical Properties

  • The mechanical properties of composite resins generally appear to be somewhat inferior compared with those of the composite resins
  • Compressive strength and flexural strength are affected
  • Wear resistance may be lower than expected for some composite resins
  • Larger filler particles reduce the interfacial integrity.

Wear Resistance

  • Wear is the process by which material is displaced or removed by the interfacial forces generated as two surfaces rub together
  • Three wear types occur: abrasive, corrosive, and adhesive
  • Abrasive wear is when two dissimilar surfaces rub together
  • Corrosive wear is chemical attack on resin caused by acid attack
  • Adhesive wear involves mechanical interlocking mechanisms
  • In general, a high filler loading in composite resin results in a stable resin and a strong surface, minimizing possible wear

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Test your knowledge on dental materials with this quiz, covering topics including diametral tensile strength, wear mechanisms, and the properties of polyacid-modified resin composites. Understand the misconceptions about hardness and wear resistance as well as the role of various components in dental applications.

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