MDS PREP
What is the primary component of zinc polycarboxylate cement?
1) Zinc oxide
2) Polyacrylic acid
3) Titanium dioxide
4) Calcium hydroxide
Zinc polycarboxylate cement primarily consists of zinc oxide and polyacrylic acid.
What are the stoichiometric formulas for the gamma (?), epsilon (?), and zeta (?) phases in dental amalgams?
1) ?: Ag3Sn, ?: Cu3Sn8, ?: Cu3Sn
2) ?: Ag3Sn, ?: AgSn, ?: CuSn
3) ?: AgSn, ?: Cu3Sn, ?: Ag3Sn8
4) ?: AgSn, ?: CuSn, ?: Ag3Sn.
?: Ag3Sn, ?: Cu3Sn8, ?: Cu3Sn
Bonding of GIC to tooth structure is brought about by
1) metal ions
2) hydroxyl bond
3) carboxyl bond
4) ionic bond
Dental Materials Answer: 3
one ot the main adanhtges of GIC as a restoratie material was its ability to form chemical bonds with the tooth structure.
Bonding in GIC primarily invokes chelation of carboxyl groups of the polyacids sith the calcium in the apatite of enamel and dentin. Bond rength of enamel is always greater than that of dentin due to higher mineral content. The bonding is improved by the removal of the debris layer called smear layer’ by a process called conditioning.
The opacity in ceramics is achieved by adding
1) Boric oxide
2) Copper oxide
3) Silica
4) Titanium oxide
What is hysteresis in the context of dental gels?
1) The difference between setting and working time
2) The difference between the temperature of gelation and liquification
3) The difference between the initial and final setting times
4) The difference between the maximum and minimum viscosities
Hysteresis in dental gels refers to the temperature lag or difference between the gelation temperature and the temperature at which the gel reverts back to a liquid state.
What is the typical range of Charpy impact strength for a heat-activated denture resin?
1) 0.48 to 0.78 joules
2) 0.98 to 1.27 joules
3) There is no typical range provided
4) The information is not relevant to heat-activated resins
Heat-activated denture resins typically have a Charpy impact strength range of 0.98 to 1.27 joules, which is higher than that of chemically activated resins.
What happens to acrylic resin when it absorbs water?
1) It expands linearly
2) It contracts linearly
3) It remains the same dimensionally
4) It swells in volume
When acrylic resin absorbs water, it expands linearly by approximately 0.23%, which can affect the fit and function of the denture.
What is the primary mechanism of adhesion for resin cements?
1) Micromechanical retention
2) Chemical bonding
3) Physical adsorption
4) Ionic bonding
Resin cements primarily achieve adhesion through micromechanical retention and chemical bonding.