All Free Dental Materials MCQs with Answers

• A. Eugenol
• B. Zinc oxide
• C. Calcium Hydroxide
• D. Silica

Explanation: Calcium hydroxide stimulates pulpal cells to form a hard-tissue barrier, including reparative dentin, because of its high alkalinity and…

• A. Low fusing ceramic and high fusing alloys
• B. Matching of coefficients of thermal expansion of ceramics and alloy
• C. Bonding between ceramic and alloy
• D. All of the above

Explanation: A successful metal-ceramic casting requires a compatible high-fusing alloy, a suitable lower-fusing ceramic, closely compatible thermal…

• A. Improve bonding
• B. Decrease porosity
• C. They react with the porcelain opaque layer, which masks the metal
• D. Improves the thermal expansion between the metal and porcelain

Explanation: Tin and indium preferentially oxidize at the alloy surface, forming oxides that chemically bond with the porcelain opaque layer.

• A. 11.5-12.5 x 10^-6/°C
• B. 13.5-14.5 x 10^-6/°C
• C. 10.5-11.5 x 10^-6/°C
• D. 16.5-17.5 x 10^-6/°C

Explanation: Metal substructures for metal-ceramic restorations commonly have a coefficient of thermal expansion around 13.5 to 14.5 × 10^-6/°C…

• A. Quartz
• B. Tridymite
• C. Cristobalite
• D. Corundum

Explanation: Cristobalite undergoes a relatively large thermal expansion, so it is incorporated into investments when greater setting and thermal…

• A. Transformation toughening
• B. Dispersion of crystalline phase
• C. All of the above
• D. Inducing residual compressive strength

Explanation: Chemical tempering strengthens porcelain by ion exchange at the surface, producing residual compressive stress that resists crack opening…

• A. In vacuum
• B. Boric oxide
• C. For long period
• D. Under pressure

Explanation: Vacuum firing removes air trapped between porcelain particles and therefore reduces internal porosity.

• A. Improper condensation
• B. Low temperature during glazing
• C. High temperature during glazing
• D. High firing temperature

Explanation: Pyroplastic flow is the viscous deformation of porcelain at elevated firing or glazing temperatures, especially when the softened…

• A. Rate of arriving at firing temperature
• B. Uniformity of particle size
• C. Type of investment used
• D. Shape and size of particle

Explanation: The shape and size of porcelain particles determine how closely they pack during condensation and how much pore space is lost as firing…

• A. Thoroughness of condensation
• B. Rapidity of firing
• C. High firing temperature
• D. All of the above

Explanation: Thorough condensation removes as much air as possible before firing, making it the primary method of preventing porcelain porosity.

• A. Feldspar
• B. Kaolin
• C. Quartz
• D. Clay

Explanation: Feldspar is the principal component of conventional dental porcelain and forms the glassy matrix after firing.

• A. Highly polished porcelain
• B. Highly glazed porcelain
• C. Highly polished acrylic
• D. Highly polished metal

Explanation: Highly glazed porcelain has a smooth, non-porous surface that minimizes plaque retention and irritation of the gingiva.

• A. Rubber
• B. Plastic
• C. Glass
• D. Organic substances

Explanation: Dental porcelain is a ceramic composed mainly of a glassy phase with dispersed crystalline phases.

• A. Colour matching
• B. Transparency
• C. Opacity
• D. None of the above

Explanation: Metallic oxides such as iron, copper, cobalt, and chromium oxides act as pigments in porcelain and help produce the required shade.

• A. Same as porcelain
• B. More than or equal to porcelain but not less
• C. Less than porcelain
• D. More than porcelain

Explanation: For a metal-ceramic restoration, the alloy’s thermal expansion should be slightly greater than, or at least equal to, that of porcelain so…

• A. Medium bisque
• B. Low bisque
• C. Cold stage bisque
• D. High bisque

Explanation: The recognized biscuit firing stages are low, medium, and high biscuit.

• A. High Bisque stage
• B. Low Bisque stage
• C. Fusion stage
• D. Medium Bisque stage

Explanation: The greatest practical shrinkage occurs during the medium-biscuit stage, when liquid-phase sintering causes particles to fuse and pores to…

• A. aluminium porcelain
• B. Glazed porcelain
• C. dispersed porcelain
• D. All of the above

Explanation: Dispersion strengthening adds crystalline alumina particles to the glassy porcelain matrix, producing aluminous or aluminium-reinforced…

• A. High fusion expansion
• B. Linear coefficient of thermal expansion less than that of metal
• C. High fusion temperature
• D. Linear coefficient of thermal expansion more than that of metal

Explanation: Porcelain should have a slightly lower linear coefficient of thermal expansion than the metal, so cooling places the porcelain in…

• A. Heat pressing
• B. Machining
• C. Sintering
• D. Slip casting

Explanation: Porcelain fused to metal is formed by compacting ceramic powder and firing it below its melting point, a process called sintering.