MDS PREP
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.
What is the typical refractive index range of bis-GMA and TEGDMA, and what happens when they are mixed in equal proportions?
1) 1.50 to 1.60 and increases.
2) 1.40 to 1.60 and decreases.
3) 1.55 for bis-GMA and 1.46 for TEGDMA, and a mixture yields approximately 1.50.
4) 1.50 for bis-GMA and 1.60 for TEGDMA, and a mixture yields approximately 1.55.
The refractive indices of bis-GMA and TEGDMA are approximately 1.55 and 1.46, respectively, and when mixed in equal proportions, they provide a refractive index of around 1.50.
What is the typical film thickness for a resin cement?
1) 50 µm
2) 25 µm
3) 15 µm
4) 5 µm
Resin cements are generally applied in a film thickness of 25 µm or less for optimal performance.
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 recommended thickness of the luting agent film for optimal effectiveness?
1) 50 µm
2) 25 µm
3) 15 µm
4) 5 µm
According to the text, a luting agent must be sufficiently fluid to flow into a continuous film of 25 µm thickness or less without fragmentation.
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.
What is the function of benzoyl peroxide in the composition of denture base resin powder?
1) It acts as a filler
2) It acts as a cross-linking agent
3) It acts as an initiator
4) It acts as an inhibitor
Benzoyl peroxide in the powder of denture base resin is responsible for initiating the polymerization process when it reacts with the monomer in the liquid component.
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.