MDS PREP
What is the difference between type I and type II glass ionomer cements?
1) Type I has a higher fluoride release
2) Type II has a higher compressive strength
3) Type I sets faster
4) Type II has better aesthetic properties
Type II glass ionomer cements have a higher compressive strength, while Type I is often used for better aesthetics.
Epoxy resins are compatible with which of the following impression material :
1) Polysulphide impression material
2) Polyether impression material
3) Agar
4) Alginate
Dental Materials Answer: 2
Epoxy resins
· Abrasion resistance is many times greater than gypsum
· More expensive
· Undergoes 0.1 – 0.2% shrinkage, thus their shrinkage is approximately equal to gypsum. This is less of problem with newer formulations & polyurethane resin.
· Their detail reproduction is better.
· Hydrocolloids, polysulfides are not compatible with them.
What are the three physical properties controlled by the ANSUADA Specification No. 1 (ISO 24234) for dental amalgam?
1) Creep, tensile strength, and thermal expansion.
2) Compressive strength, hardness, and density.
3) Creep, compressive strength, and dimensional change.
4) Tensile strength, modulus of elasticity, and corrosion resistance.
The specification controls the qualities of dental amalgam by listing requirements for creep, compressive strength, and dimensional change.
What are the typical mixing and setting times for zinc phosphate cement?
1) Mixing time: 1-2 minutes, Setting time: 5 minutes
2) Mixing time: 5-10 minutes, Setting time: 20 minutes
3) Mixing time: 1-15 minutes, Setting time: 1-2 minutes
4) Mixing time: 3-5 minutes, Setting time: 5-10 minutes
According to the text, the mixing time for zinc phosphate cement is about 1-15 minutes.
The impression for a diagnostic cast of a partial edentulous mouth should be taken in:
1) Impression wax
2) Modelling compound
3) Hydro-colloid
4) Hydro cal
Dental Materials Answer: 3
For making impressions of edentulous ridges, impression plaster and impression compound are considered to be useful. For partial edentulous mouth impressions, hydrocolloids are useful.
What is the typical composition of Resin-Modified Glass Ionomer Cement (RMGI)?
1) Glass ionomer and polyacrylic acid
2) Glass ionomer, HEMA, and tartaric acid
3) Glass ionomer and polycarboxylate acid
4) Glass ionomer and zinc oxide
RMGI contains glass ionomer along with 2-hydroxyethylmethacrylate (HEMA) and tartaric acid to improve its properties.
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 dough-forming time for denture base resin according to ANSI/ADA Specification No. 12?
1) Less than 10 minutes
2) Less than 5 minutes
3) Less than 20 minutes
4) Less than 30 minutes
ANSI/ADA Specification No. 12 requires that the material should reach a doughlike consistency in less than 10 minutes from the start of the mixing process.