Polymerization Shrinkage in Dentistry Quiz

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Questions and Answers

What is the purpose of using Pigments in denture fabrication?

To give the natural tissue-like appearance

In denture fabrication, what is the function of Plasticizers?

To give more resilient & softer polymer

What is the role of Opacifier in denture materials?

To give radio-opacity

How does the Inhibitor hydroquinone contribute to denture fabrication?

To inhibit polymerization on storage Signup and view all the answers

What is the purpose of Cross-linking agent (glycol dimethacrylate) in denture materials?

To increase mechanical properties and decrease cracks Signup and view all the answers

What is the recommended P/L ratio for proportioning in denture fabrication?

3:1 by volume or 2.5:1 by weight Signup and view all the answers

What are the thermal properties of non-metallic dentures?

Thermal conductivity is very low, leading to oral tissue isolation from temperature sensations. Coefficient of thermal expansion is high, causing contraction and expansion which may result in loss of porcelain teeth. Signup and view all the answers

What causes surface porosity in dentures?

Surface porosity is caused by under packing, packing early at a sticky stage, excessive monomer, and lack of separating medium. Signup and view all the answers

How does over curing lead to gaseous porosity in dentures?

Over curing can result in fine, uniform bubbles in thicker parts of the denture, leading to gaseous porosity. Signup and view all the answers

What is crazing in dentures and what factors contribute to it?

Crazing refers to cracks in dentures caused by mechanical stress, solvent action, differences in coefficient of thermal expansion, cleaning with bleaching agents or alcohol, and lack of separating medium. Signup and view all the answers

What distinguishes pour type resin from other denture base resins?

Pour type resin has very small polymer beads, resulting in a very fluid mix and excellent reproduction of details. Signup and view all the answers

How does high impact strength resin differ from heat cure resin?

High impact strength resin is similar to heat cure resin but is reinforced with butadiene styrene rubber. Signup and view all the answers

What is the role of painting all parts of the cast in the flask with a separating medium, except for the occlusal part?

Prevent passage of H2O from gypsum to resin, decrease passage of monomer to plaster, decrease porosity, facilitate separation of flasks Signup and view all the answers

What are the consequences of packing the acrylic material into the flask too early?

Decrease viscosity, easy flow out of the flask, increased porosity Signup and view all the answers

What problems can occur if the acrylic material is packed into the flask too late?

Increased viscosity, no metal to metal contact, movement or fracture of teeth Signup and view all the answers

What is the purpose of overfilling the mold and applying sufficient pressure during the flasking process?

To reduce shrinkage porosity due to under packing and/or low pressure Signup and view all the answers

What are the effects of premature opening of the flask before cooling?

It may cause warpage in the denture Signup and view all the answers

How does rapid cooling impact the internal stresses in the denture?

Rapid cooling will increase internal stresses (thermal stresses) in the denture Signup and view all the answers

Study Notes

Purpose of Pigments in Denture Fabrication

Pigments enhance the aesthetic appearance of dentures, closely mimicking natural tissue colors.

Function of Plasticizers in Denture Fabrication

Plasticizers improve the flexibility and workability of denture materials, allowing for better shaping and adjustment.

Role of Opacifier in Denture Materials

Opacifiers increase the opacity of denture materials, preventing shine-through of the underlying structures and improving aesthetics.

Contribution of Inhibitor Hydroquinone in Denture Fabrication

Hydroquinone acts as a polymerization inhibitor, preventing premature setting of materials during storage and improving shelf life.

Purpose of Cross-linking Agent (Glycol Dimethacrylate) in Denture Materials

Glycol dimethacrylate introduces cross-linking, enhancing the strength and stability of denture materials.

Recommended P/L Ratio for Proportioning in Denture Fabrication

A commonly recommended powder-to-liquid (P/L) ratio is essential for achieving optimal consistency and strength in the cured acrylic.

Thermal Properties of Non-Metallic Dentures

Non-metallic dentures exhibit good thermal insulation properties, providing comfort during temperature transitions in the oral cavity.

Causes of Surface Porosity in Dentures

Surface porosity can arise from inadequate mixing of the acrylic components or insufficient pressure during the curing process.

Over Curing and Gaseous Porosity in Dentures

Over curing leads to thermal expansion and the formation of gas bubbles, resulting in gaseous porosity within the denture material.

Crazing in Dentures and Contributing Factors

Crazing refers to the formation of fine cracks in the denture's surface, which can be caused by stress, rapid temperature changes, and low-quality materials.

Distinction of Pour Type Resin from Other Denture Base Resins

Pour type resins are unique in that they are mixed to a liquid form and poured into molds, unlike other types that may require packing.

Difference Between High Impact Strength Resin and Heat Cure Resin

High impact strength resins are designed to withstand greater forces and resist breakage compared to traditional heat cure resins, making them more durable.

Role of Separating Medium Application on Flask Cast

Applying a separating medium on all parts of the cast, except the occlusal area, facilitates easy demolding and prevents material adhesion.

Consequences of Early Packing of Acrylic Material into Flask

Packing too early can lead to poor adaptation and voids, compromising the fit and aesthetics of the final denture.

Problems from Late Packing of Acrylic Material into Flask

Delaying packing can result in premature setting, limiting the materials' workability and increasing the risk of defects in the final product.

Purpose of Overfilling Mold and Sufficient Pressure During Flasking

Overfilling and applying sufficient pressure ensure complete mold adaptation while eliminating voids, enhancing the denture's integrity.

Effects of Premature Opening of Flask Before Cooling

Opening the flask too early can lead to dimensional changes and deformation, negatively affecting denture fit and stability.

Impact of Rapid Cooling on Internal Stresses in Dentures

Rapid cooling induces internal stresses, which can cause warping or cracking, ultimately compromising the durability and function of the denture.

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Description

Test your knowledge on polymerization shrinkage in dentistry, including the use of initiators, pigments, plasticizers, and other additives to improve properties of dental materials. Learn about monomers, inhibitors, cross-linking agents, and liquid components.