MDS PREP
What is the chemical structure of Giomers?
1) They contain fluoraluminosilicate glass and silica-filled urethane resin.
2) They are purely organic ceramic-filled polymers.
3) They are a combination of glass ionomer and resin-modified glass ionomer.
4) They have a matrix of polyacrylic acid and ceramic filler particles.
Giomers are a combination of fluoraluminosilicate glass and silica-filled urethane resin. This unique composition allows for the release of fluoride and improved physical properties compared to traditional composites.
What is the primary function of a dental sealer in restorative procedures?
1) To prevent microleakage
2) To desensitize the tooth
3) To enhance the aesthetics of the restoration
4) To reinforce the tooth structure
A dental sealer is used to fill the microscopic spaces between the restorative material and the tooth structure, primarily to prevent microleakage.
What is Goldent, and how is it used in dental restorations?
1) A brand of gold alloy used for inlays and onlays
2) A form of gold foil with a high platinum content
3) A combination of powdered gold and gold foil in a pellet form
4) A gold-plated stainless steel mesh used for subgingival retention
Goldent is a form of direct gold restoration where pellets of powdered gold are wrapped in a No. 3 gold foil. The foil acts as a container for the gold particles and allows for better handling and condensation during placement. Each pellet contains approximately 95% powdered gold and 5% gold foil, making it more economical than using gold foil alone for restorations.
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 are the advantages of using Ormocers in dental restorations?
1) High elasticity and low thermal conductivity.
2) Low shrinkage and excellent biocompatibility.
3) Easy to manipulate and high modulus of elasticity.
4) Good radiopacity and high load deflection rate.
Ormocers have several advantages, including low shrinkage, excellent biocompatibility, and superior resistance to masticatory forces. These properties make them suitable for restorations that resemble natural teeth.
What is the typical mixing ratio for zinc polycarboxylate cement?
1) 1:1
2) 1:2
3) 2:1
4) 3:1
The typical mixing ratio for zinc polycarboxylate cement is 1:2 (powder to liquid).
Which type of amalgam alloy has the lowest compressive strength at 1 hour?
1) High-copper lathe-cut alloy
2) Low-copper lathe-cut alloy
3) High-copper spherical alloy
4) Low-copper spherical alloy
The compressive strength at 1 hour is lowest for the low-copper lathe-cut alloy, which is 45 MPa.
Bonding of GIC to tooth structure is brought about by
1) metal ions
2) hydroxyl bond
3) carboxyl bond
4) ionic bond
Dental Materials Answer: 3
one ot the main adanhtges of GIC as a restoratie material was its ability to form chemical bonds with the tooth structure.
Bonding in GIC primarily invokes chelation of carboxyl groups of the polyacids sith the calcium in the apatite of enamel and dentin. Bond rength of enamel is always greater than that of dentin due to higher mineral content. The bonding is improved by the removal of the debris layer called smear layer’ by a process called conditioning.