MDS PREP
What is the effect of temperature on the setting time of gypsum products?
1) Increased temperature accelerates the setting reaction.
2) Increased temperature has no effect on the setting reaction.
3) Increased temperature retards the setting reaction.
4) Temperature has an inconsistent effect on the setting reaction.
Higher temperatures generally speed up the chemical reactions involved in the setting of gypsum products, leading to a shorter setting time.
Porcelain binds to metal in PFM crown by:
1) Metallic bind
2) Mechanical bond
3) Chemical bond
4) Both 2 and 3
Dental Materials Answer: 4
Porcelain binds to metal in metal ceramic restorations by mechanical interlocking and chemical bonding. Mechanical interlocking is provided by proper wetting of the metal surface by porcelain.
The adherent metallic oxides, which are formed during the degassing cycle form a good chemical bond with porcelain.
Tin oxide and Indium oxide are formed from precious metal alloys while chromium oxide is formed from base metal alloys.
What is the effect of adding a nonionic surfactant to silicone impression materials?
1) Increases hydrophilicity
2) Decreases tear strength
3) Enhances setting time
4) Reduces dimensional accuracy
Adding a nonionic surfactant to silicone impression materials makes the surface more hydrophilic, allowing for better wetting of soft tissues and improved detail capture.
What are the main components of a typical dental composite resin?
1) Monomers, fillers, initiators, and accelerators.
2) Resins, fillers, catalysts, and diluents.
3) Polymers, pigments, and plasticizers.
4) Monomers, fillers, and cross-linking agents.
Dental composite resins typically consist of a resin matrix (monomers), filler particles (such as silica or glass), initiators (like camphorquinone), and accelerators (such as amines) to control the setting process.
How do resin teeth typically bond with denture base resins?
1) Through mechanical undercuts.
2) Through silanization.
3) By forming chemical bonds.
4) Both A and B.
Resin teeth are capable of forming chemical bonds with commonly used denture base resins, which allows for a stronger and more durable bond compared to porcelain teeth.
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 are Compomers more correctly termed?
1) Methacryloxy decyl pyridinium bromide-modified composite resins
2) Polyacid-modified composite resins
3) Polymethacrylate-based composite resins
4) Glass ionomer-modified composite resins
Compomers are more correctly termed Polyacrylic acid Modified Composite Resins (PMCRs). They are a blend of glass ionomer and composite resin properties, making them user-friendly and suitable for certain restorative procedures.
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.