MDS PREP
What is the primary function of 2-hydroxyethyl methacrylate (HEMA) in dentinal bonding?
1) To act as an initiator for the polymerization reaction
2) To create a hydrophobic barrier between dentin and resin
3) To dissolve the dentin surface
4) To create a hydrophilic bridge between the dentin and resin
HEMA is a hydrophilic monomer that is applied to the conditioned dentin. It fills the dentinal tubules and adheres to the exposed collagen fibers, creating a wetting layer that allows subsequent hydrophobic resins to infiltrate and bond to the dentin. This bridging action is crucial for the adhesion of resin to the hydrophilic dentin surface, which is essential for the longevity and durability of the restoration.
How do resin teeth typically bond with denture base resins?
1) Through mechanical undercuts.
2) Through silanization.
3) By forming chemical bonds.
4) Both A and B.
Resin teeth are capable of forming chemical bonds with commonly used denture base resins, which allows for a stronger and more durable bond compared to porcelain teeth.
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.
What is the by-product of the condensation setting reaction in silicone elastomers?
1) Water
2) Ethyl alcohol
3) Carbon dioxide
4) Oxygen
The condensation reaction in silicone elastomers produces ethyl alcohol, which evaporates during setting, contributing to the material's contraction.
What are microfilled composites known for?
1) Their high wear resistance.
2) Their high translucency.
3) Their ease of manipulation.
4) Both A and B.
Microfilled composites contain very fine silica particles (0.04 to 0.2 µm in diameter), which give them excellent translucency and a high surface area for better filling of small restorations.
What is the typical film thickness required for zinc polycarboxylate cement?
1) 50 µm
2) 25 µm
3) 15 µm
4) 5 µm
As a luting material, zinc polycarboxylate should form a film of less than 25 µm.
What is the role of a primer in the bonding process of resin cements?
1) To clean the tooth surface
2) To increase the surface energy of the tooth structure
3) To reduce the surface tension of the bonding agent
4) To accelerate the setting of the cement
A primer increases the surface energy of the tooth structure, enhancing the ability of the bonding agent to wet and infiltrate the surface.
Which of the following is not a type of oil-based cement?
1) Zinc oxide-eugenol
2) Zinc phosphate
3) Nano-eugenol-zinc oxide
4) All of the above are oil-based cements
Zinc oxide-eugenol is the only oil-based cement mentioned in the text.