MDS PREP
What is the primary advantage of zinc polycarboxylate cement?
1) High thermal conductivity
2) Low film thickness requirement
3) Chemical bonding with tooth structure
4) Fast setting time
Zinc polycarboxylate cement was formulated to have the strength of zinc phosphate and the biological acceptability of zinc oxide-eugenol cements, with the added advantage of chemical bonding to tooth structure.
What is the typical setting time for a high strength dental stone?
1) Less than 10 minutes.
2) 10-30 minutes.
3) 30-60 minutes.
4) More than 60 minutes.
High strength dental stones typically have a setting time of 30-60 minutes, which allows for sufficient working time while providing enhanced mechanical properties.
What is the primary difference between a glass ionomer and a resin-modified glass ionomer cement?
1) Setting time
2) Mechanism of bonding
3) Compressive strength
4) Fluoride release
The primary difference is the presence of resin in resin-modified glass ionomer, enhancing bonding and strength.
Maximum shrinkage on firing of ceramic occurs during which stage
1) High bisque
2) Low bisque
3) During condensation
4) None of the above
Dental Materials Answer: 1
Ceramic firing involves a series of processes that transform raw clay
materials into a hard, durable ceramic product. The stages of firing can be
broken down into several steps, but the primary ones are bisque firing and glaze
firing. The bisque firing is done before glazing and is typically the first
firing in the process. The purpose of bisque firing is to remove any remaining
moisture, organic matter, and to harden the ceramic piece to a certain extent,
making it suitable for the application of glazes.
There are two main types of bisque firings:
1. Low bisque: This is a lower temperature firing, usually around 950°C to
1000°C (1742°F to 1832°F). It is used for porous clay bodies and allows for some
shrinkage to occur, but it does not fully vitrify the clay. This stage is often
referred to as the biscuit or bisque stage.
2. High bisque: This is a higher temperature firing, typically between 1000°C to
1150°C (1832°F to 2102°F). It is used for clay bodies that require a higher
degree of vitrification and strength before glazing. At these temperatures, the
clay body experiences significant chemical changes and begins to shrink more
dramatically.
The maximum shrinkage of ceramic occurs during the high bisque stage because the
clay particles undergo a process called vitrification. Vitrification is the
point at which the clay's mineral content starts to melt and fuse together,
creating a glass-like phase within the clay matrix. This results in a stronger,
less porous, and denser material. As the minerals melt and the particles bond,
the overall volume of the material decreases, causing the shrinkage.
The shrinkage rate is influenced by various factors, such as the type of clay,
its composition, water content, and the specific temperature profile of the
firing process. However, it is generally during the high bisque that the most
significant shrinkage occurs. After the high bisque, the subsequent glaze firing
is at a higher temperature, which may cause additional shrinkage, but it is
usually less substantial compared to the initial bisque firing.
What is the primary component that gives Ceromer its unique handling characteristics and contributes to its restorative perfection?
1) Ceramic fillers
2) Fluoride releasing fillers
3) Polymer matrix
4) Combination of ceramic fillers and fluoride releasing fillers
Ceromer is a composite material that combines the benefits of glass ionomers and composite resins. The inclusion of ceramic fillers and fluoride releasing fillers in a polymer matrix gives Ceromer its unique handling properties and enhances its restorative capabilities.
What is the chemical composition of Giomers?
1) They are made of fluoride-releasing resin with ceramic filler.
2) They are a combination of glass ionomer and composite resin.
3) They contain fluoraluminosilicate glass and polyalkenoic acid.
4) They are composed of a polymethacrylate matrix with silica fillers.
Giomers are hybrid aesthetic restorative materials that employ PRG technology. The chemical composition includes fluoraluminosilicate glass reacted with polyalkenoic acid, which is then included in a silica-filled urethane resin matrix.
What is the maximum allowable dimensional change for amalgams according to ANSI/ADA Specification No. 1?
1) Not more than 10 µm/cm.
2) Not more than 20 µm/cm.
3) Not more than 30 µm/cm.
4) Not more than 40 µm/cm.
The specification requires that amalgam neither contract nor expand more than 20 µm/cm.
What is the primary purpose of using a thermal insulating base?
1) To protect the pulp from thermal changes
2) To increase the strength of the restoration
3) To improve the aesthetics of the restoration
4) To facilitate the removal of the restoration
The purpose of a thermal insulating base is to protect the pulp from temperature changes during the placement of a restoration.