MDS PREP
What is the effect of adding a nonionic surfactant to silicone impression materials?
1) Increases hydrophilicity
2) Decreases tear strength
3) Enhances setting time
4) Reduces dimensional accuracy
Adding a nonionic surfactant to silicone impression materials makes the surface more hydrophilic, allowing for better wetting of soft tissues and improved detail capture.
Porcelain binds to metal in PFM crown by:
1) Metallic bind
2) Mechanical bond
3) Chemical bond
4) Both 2 and 3
Dental Materials Answer: 4
Porcelain binds to metal in metal ceramic restorations by mechanical interlocking and chemical bonding. Mechanical interlocking is provided by proper wetting of the metal surface by porcelain.
The adherent metallic oxides, which are formed during the degassing cycle form a good chemical bond with porcelain.
Tin oxide and Indium oxide are formed from precious metal alloys while chromium oxide is formed from base metal alloys.
How is platinized gold foil formed?
1) By mixing gold and platinum powders and then beating them
2) By rolling gold and platinum sheets together to form a laminated foil
3) By plating gold onto a platinum substrate
4) By fusing a platinum rod with a gold ingot
Platinized gold foil is a combination of gold and platinum where 15% of the content is platinum. It is produced by rolling layers of gold and platinum together to achieve the desired thickness and distribution of the platinum within the gold foil. This process creates a homogeneous mixture that enhances the hardness and wear resistance of the restoration, making it suitable for high-stress areas like incisal edges and cusp tips.
What is the primary function of a light-curing unit in the polymerization of resin-based materials?
1) To generate heat for setting.
2) To activate the photosensitizer and initiate the polymerization reaction.
3) To accelerate the chemical reaction.
4) To increase the viscosity of the material.
Light-curing units emit light at specific wavelengths that are absorbed by the photosensitizer in the resin, triggering the free radical polymerization process and setting the material.
What is the relationship between the concentration of zinc and the setting expansion of an amalgam alloy?
1) A higher zinc concentration results in greater setting expansion.
2) A lower zinc concentration results in greater setting expansion.
3) There is no relationship between zinc concentration and setting expansion.
4) The relationship is not specified in the given text.
The relationship between zinc concentration and setting expansion is not specified in the given text. However, the presence of zinc in amalgams can affect the rate and extent of setting.
What is the purpose of the acidic monomer in resin cements?
1) To neutralize the alkaline tooth structure
2) To dissolve the smear layer
3) To initiate the polymerization reaction
4) To increase the viscosity of the cement
The acidic monomer helps to dissolve the smear layer for better penetration and bonding.
What is the typical timeframe for the initiation of dimensional change measurement in an amalgam?
1) At the beginning of trituration.
2) Between 5 minutes and 24 hours after the beginning of trituration.
3) At the end of trituration.
4) 40 days after the restoration.
Dimensional change measurement is typically initiated between 5 minutes and 24 hours after the beginning of trituration.
What is the typical intensity range of a dental argon laser?
1) 1-10 mW.
2) 100-500 mW.
3) 500-1000 mW.
4) More than 1000 mW.
Dental argon lasers typically operate within the range of 100 to 500 mW, providing sufficient power for soft tissue procedures and some hard tissue interactions.