MDS PREP
What is the typical peak wavelength for light-activated dental composite resins?
1) 300-400 nm.
2) 400-500 nm.
3) 500-600 nm.
4) 600-700 nm.
Light-activated dental composite resins are usually cured with blue light at a peak wavelength of about 470 nm, which is absorbed by the photoinitiator, such as camphorquinone.
What is the typical setting time for gypsum-based products like dental plasters and stones?
1) Less than 10 minutes.
2) 10-30 minutes.
3) 30-60 minutes.
4) More than 60 minutes.
The setting time for gypsum products can range from a few minutes for impression plaster to up to 30 minutes for some dental stones, depending on the specific formulation and water to powder ratio.
What is the main disadvantage of using zinc phosphate cement?
1) Low compressive strength
2) Potential for pulpal irritation
3) Difficulty in removal
4) High cost
While it has good mechanical properties, poorly placed zinc phosphate cement can cause pulpal irritation.
What is the primary function of a base material in dental restoration?
1) To seal the tooth from microleakage
2) To provide insulation from thermal changes
3) To reinforce the tooth structure
4) To enhance the aesthetics of the restoration
A base material in dental restoration is primarily used to provide a seal against microleakage.
What is the typical particle size of silica in microfilled composites?
1) 0.5-1 µm.
2) 0.04-0.2 µm.
3) 1-10 µm.
4) 10-30 µm.
Microfilled composites have a very high surface area with silica particles diameters of 0.04 to 0.2 µm, which provides excellent aesthetic results and polishability.
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.
What are the ideal requirements for a luting agent according to ANSI/ADA Specification No. 96 (ISO 9917)?
1) High compressive strength and long setting time
2) Low compressive strength and short setting time
3) High compressive strength and short setting time
4) Low compressive strength and long setting time
The text does not provide specifics on luting agent requirements in terms of compressive strength and setting time.
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.