MDS PREP
Nitinol has the disadvantage of which of the following?
1) It cannot be formed into desired shapes
2) It lacks elastic properties
3) Its strength is not suited for orthodontic purposes
4) It lacks stiffness
Dental Materials Answer: 1
Nitinol is a metal alloy – or mixture – of nickel and titanium. This type of wire is also known as “memory wire” or “smart wire,” and it can be used for braces.
What is the Threshold Limit Value (TLV) for mercury vapor exposure set by OSHA?
1) 0.01 mg/m3
2) 0.02 mg/m3
3) 0.05 mg/m3
4) 0.1 mg/m3
The TLV for mercury vapor set by OSHA is 0.05 mg/m3.
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.
What is the purpose of adding barium sulfate to Gutta Percha?
1) To make it more radio-opaque
2) To improve thermal conductivity
3) To enhance the setting reaction
4) To act as a plasticizer
Barium sulfate is added to Gutta Percha to enhance its radiographic visibility.
What is the primary concern with using zinc oxide-eugenol cement in large restorations?
1) Low compressive strength
2) Potential for pulpal toxicity
3) High thermal conductivity
4) High solubility
The primary concern is the potential for pulpal toxicity due to the diffusion of eugenol.
What is the effect of temperature on the setting time of gypsum products?
1) Increased temperature accelerates the setting reaction.
2) Increased temperature has no effect on the setting reaction.
3) Increased temperature retards the setting reaction.
4) Temperature has an inconsistent effect on the setting reaction.
Higher temperatures generally speed up the chemical reactions involved in the setting of gypsum products, leading to a shorter setting time.
What are the advantages of using light-cured composites over chemically cured products?
1) Less porosity, less staining, increased strength, enhanced color stability, and control of working time.
2) Faster curing time, better translucency, and less shrinkage.
3) Longer shelf life and lower cost.
4) Higher wear resistance and easier to manipulate.
Light-cured composites do not require mixing, which reduces porosity and staining. They also allow for better control over working time and increased color stability due to the use of aliphatic amines.
What is the maximum weight loss allowed for a specimen surface according to the specification?
1) 0.04 mg/cm³
2) 0.69 mg/cm²
3) 0.23 mg/cm²
4) There is no maximum weight loss mentioned
The specification mentions that the weight loss must not be greater than 0.04 mg/cm³ from the specimen surface, which is considered negligible from a clinical standpoint.