MDS PREP
OVERTRITURATION of silver alloy and mercury:
1) reduces contraction
2) increases strength of lathe cut alloy but reduces strength of spherical
3) decreases creep
4) gives a dull crumby mix
overtrituration (i.e., triturating for longer than the recommended time) results in a mix that is warm and has a dull surface; often the mix sticks to the capsule; it shortens setting time (because the amalgam mass becomes heated), increases contraction, and increases creep; also increases tensile and compressive strength values (for lathe-cut alloys), decreases tensile and compressive strengths (for spherical alloys); overtrituration by 10% is acceptable
During cavity preparation, more incidence of exposure is in
1. Class V cavity in first premolar
2. Class II mesioocclusal cavity
3. Class II distoocclusal cavity
4. Class IV cavity
Conservative Dentistry
Answer: 1
During cavity preparation, the incidence of pulpal exposure is higher in class V
cavities on first premolars due to the proximity of the margins to the pulp
horns.
The product that is formed on the surface of the amalgam restoration and frequently results in discolouration is
1) Sulphide
2) Gamma I phase
3) Gamma II phase
4) Oxide
Conservative Dentistry
Answer: 1
The discoloration of amalgam restorations is often due to the formation of silver sulfide on the surface, which can occur due to the reaction of silver with sulfur compounds in the oral environment. The gamma I phase is a strong component of amalgam, while the gamma II phase is weaker and less stable. Oxides can form as well, but sulfides are more directly associated with the discoloration observed in clinical settings.
Annealing of gold foil is the process by which
1. Contaminants are removed from the surface
2. Rigidity decreases and ductility increases
3. Both ductility and propotional limit decrease
4. None of the above
Conservative Dentistry
Answer: 1
Annealing gold foil is the process of heating gold to remove impurities and restore its cohesion properties. Annealing of gold foil is a heat treatment process used to alter the physical and sometimes chemical properties of the material. The primary purpose of annealing gold foil is to remove any contaminants and stresses that may be present on the surface of the material. This is achieved by heating the gold foil to a specific temperature, typically around 400°C (750°F), and then allowing it to cool slowly. The process can also help in improving the foil's ductility, making it more malleable and easier to work with. However, the direct effect of annealing on the rigidity, ductility, and proportional limit is not explicitly stated in the question, and thus the correct answer is that annealing of gold foil primarily serves to remove contaminants from the surface.
The CAD-CAM system uses
1) Cadmium in castings
2) A purcelain furnace with very high temperature
3) A video camera to all the prepared tooth
4) None of the above
Conservative Dentistry
Answer: 3
The CAD-CAM system utilizes digital imaging, often through a video camera or
scanner, to capture the prepared tooth for designing restorations.
Retention grooves are placed in a class V cavity for non-adhesive restoration in
1. Mesioaxial and distoaxial line angles
2. Occlusoaxial and gingivoaxial line angles
3. All line angles of the cavity
4. None of the above
Conservative Dentistry
Answer: 2
Retention grooves in a class V cavity for non-adhesive restoration are placed in
the mesioaxial and distoaxial line angles. These grooves help hold the
restoration in place by providing mechanical retention and reducing the risk of
microleakage.
Main feature of class V amalgam restoration
1) Occlusal wall is greater than gingival wall
2) Retention undercuts placed in the mesial and distal walls
3) Axial wall is flat and does not follow the contours of the tooth
4) Mesial and distal walls converge
Conservative Dentistry
Answer: 1
In Class V restorations, which are located at the gingival third of the facial or lingual surfaces of teeth, the occlusal wall is typically wider than the gingival wall. This design helps in providing retention and resistance to the restoration, as the occlusal wall is more subject to occlusal forces.
When preparing adjacent class III cavities recommended procedures
1. Prepare large first but fill last
2. Prepare small first but fill last
3. Prepare and fill the small first
4. Prepare and fill the large first
Explanation: When dealing with adjacent Class III cavities, it is generally recommended to prepare the larger cavity first and fill it last. This approach allows the dentist to have better access and visibility when preparing the larger cavity, which can be more complex. Filling the larger cavity last helps to avoid contamination and ensures that the smaller cavity can be filled with precision without compromising the integrity of the larger restoration.