MDS PREP
The point at which a stress of a material exhibits a specific limited deviation P Is called
1) Proportional limit
2) Tensile strength
3) Ultimate strength
4) Yield strength
Dental Materials Answer: 4
Yield strength is the stress required to produce plastic deformation.
During crown cementation, complete filling of crown with cement is not advisable due to :
1) Increased risk of bubble entrapment
2) Increased seating time
3) Increased pressure required for seating crown
4) All of the above
Dental Materials Answer: 4
It is not advisable to fill the crown completely with cement due to following 4 reasons:
1. the time for removal of excess cement elevates.
2. the risk for bubble entrapment increases
3. increased pressure may be needed
4. the time for seating increases
What is the primary wavelength emitted by an argon laser used in dentistry?
1) 400-500 nm.
2) 500-600 nm.
3) 800-900 nm.
4) 1000-1100 nm.
Argon lasers emit light in the green-blue spectrum, with wavelengths between 488 and 514.5 nm, which are absorbed well by pigmented tissues like hemoglobin and melanin, making them useful for soft tissue procedures.
Which of the following is NOT a component of dental amalgam?
1) Finely ground silver/tin metal powder
2) Mercury
3) Hydrophilic polymer
4) Zirconia
Dental amalgam is a mixture of metallic elements consisting of silver, tin, copper, and sometimes zinc, combined with liquid mercury to form an amalgamated alloy. The mercury acts as a matrix that bonds the metal particles together. It does not contain hydrophilic polymers, which are typically found in resin-based composite materials used for tooth-colored restorations.
What is the typical particle size range of the fillers in conventional, microfilled, and hybrid composites?
1) Conventional: 8-12 µm, Microfilled: 0.04-0.4 µm, Hybrid: 0.1-0.01 µm
2) Conventional: 1-5 µm, Microfilled: 0.04-0.4 µm, Hybrid: 0.01-0.1 µm
3) Conventional: 8-12 µm, Microfilled: 0.01-0.05 µm, Hybrid: 0.5-1 µm
4) Conventional: 0.01-0.1 µm, Microfilled: 0.1-0.5 µm, Hybrid: 0.5-1 µm
The particle size of the fillers in composite materials affects their physical and handling properties. Conventional composites have larger filler particles, while microfilled and hybrid composites have smaller ones. The text provides the typical ranges for each type of composite.
What is the primary chemical bonding mechanism between etched enamel and restorative materials?
1) Formation of a smear layer.
2) Ionic bonding.
3) Covalent bonding.
4) Mechanical interlocking.
Acid etching creates microscopic tags and fissures on the enamel surface, allowing the restorative material to flow in and mechanically interlock, enhancing the bond strength.
What is the maximum allowable creep for a 1-day-old amalgam specimen under a 36 MPa stress at 37°C according to ANSI/ADA Specification No. 1 (ISO 24234)?
1) 0.5%
2) 1%
3) 2%
4) 3%
The maximum allowable creep is 1% for amalgam quality according to the specification.
What is the primary use of sodium chloride as an accelerator in gypsum-based materials?
1) To increase the setting temperature.
2) To accelerate the setting reaction.
3) To improve the mechanical properties.
4) To prolong the working time.
Sodium chloride acts as an accelerator in gypsum-based materials by increasing the solubility of the hemihydrate, thereby speeding up the conversion to dihydrate and the overall setting process.