MDS PREP
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 the typical composition of the mica crystals in a fluoromica glass ceramic like Dicor?
1) SiO2 · K2O · MgO · Al2O3 · ZrO2
2) Al2O3 · K2O · Na2O · MgO · ZrO2
3) SiO2 · CaO · Al2O3 · ZrO2
4) Al2O3 · Na2O · MgO · CaO
Fluoromica glass ceramics like Dicor have a composition based on mica crystals consisting of silica, potassium oxide (K2O), magnesium oxide (MgO), and aluminum oxide (Al2O3), with zirconium oxide (ZrO2) added for stability. Fluorides are included in the mixture to achieve fluorescence in the finished prosthesis. The material is castable and shares some similarities with traditional dental ceramics but with unique properties derived from its crystalline structure.
What is the effect of silicate cement on the pulp?
1) It is non-irritating.
2) It is mildly irritating.
3) It is highly irritating.
4) It has no effect.
Silicate cement is classified as a severely irritant to the pulp.
What is the typical bond strength of etched enamel with restorative materials?
1) 5-10 MPa.
2) 15-25 MPa.
3) 5-10 MPa.
4) 30-50 MPa.
Properly etched enamel surfaces can achieve bond strengths of approximately 15 to 25 MPa when using suitable restorative materials.
Which of the following statements about the dimensional change of amalgams is correct?
1) The low-copper, lathe-cut alloy has the highest dimensional change.
2) The high-copper admixed alloy has the lowest dimensional change.
3) All amalgams have a dimensional change of -19.7 µm/cm.
4) All amalgams have a dimensional change of -1.9 µm/cm.
The lowest change of -1.9 µm/cm was for the high-copper admixed alloy.
Which of the following is NOT a component of dental amalgam?
1) Finely ground silver/tin metal powder
2) Mercury
3) Hydrophilic polymer
4) Zirconia
Dental amalgam is a mixture of metallic elements consisting of silver, tin, copper, and sometimes zinc, combined with liquid mercury to form an amalgamated alloy. The mercury acts as a matrix that bonds the metal particles together. It does not contain hydrophilic polymers, which are typically found in resin-based composite materials used for tooth-colored restorations.
Before restoring a tooth with composite, the area is etched. Accidental contamination occurs with saliva, Therefore
1) the area is re-etched before restoration
2) the area is air-dried using an air spray and continue with restoring
3) wipe the saliva with cotton and continue to restore.
4) add excess composie material and cure it
Dental Materials Answer: 1
Etching of tooth surface with 37% phosphoric acid creates microporosities in the enamel and dentin. This is the main method of adhesion of composite resin to tooth surface.
After etching the surface energy of the enamel will increase. This will make it very sticky to any kind of contaminants. If salivary contamination will occur, the salivary proteins will precipitate in the microporosities. This will prevent the adequate penetration of the bonding agent, therby reducing the micotag formation. Hence, complete isolation is essential.
What happens if the water temperature exceeds 50°C during the mixing of gypsum products?
1) The setting reaction is accelerated.
2) The setting reaction is retarded.
3) No reaction occurs.
4) The material becomes less soluble.
If the temperature of the water used to mix gypsum products exceeds 50°C, it can slow down the setting reaction due to the reversible nature of the gypsum crystal formation at higher temperatures.