MDS PREP
What is the significance of the hybrid layer in dentin bonding?
1) It provides a barrier to prevent microleakage.
2) It has no significant role in bond strength.
3) It improves the aesthetics of the restoration.
4) It is an artifact of the etching process.
The hybrid layer formed by the infiltration of resin into the etched dentin provides a strong mechanical interlock and acts as a barrier to prevent microleakage between the restoration and the tooth structure.
What is the typical concentration range for an amine initiator like DMAEMA in a dental composite resin?
1) 0.1-0.2 wt%.
2) 0.5-1.0 wt%.
3) 1-2 wt%.
4) 2-5 wt%.
An aliphatic amine like DMAEMA is used at low concentrations (around 0.15 wt%) in composite resins to initiate the free radical polymerization in the presence of the light-sensitive initiator, such as camphorquinone.
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.
What is the primary function of a base material in dental restoration?
1) To seal the tooth from microleakage
2) To provide insulation from thermal changes
3) To reinforce the tooth structure
4) To enhance the aesthetics of the restoration
A base material in dental restoration is primarily used to provide a seal against microleakage.
What is the purpose of the calcium content in an electralloy?
1) To improve its malleability
2) To enhance its resistance to corrosion
3) To facilitate bonding with dental tissues
4) To increase its hardness and wear resistance
Electralloy is an alloy of electrolytic gold and calcium, typically with a calcium content of 0.1-0.5%. The addition of calcium creates a dispersion-hardened material that is stronger than pure gold. This property makes it suitable for use in restorations requiring increased hardness and wear resistance, such as inlays and onlays.
What is the primary purpose of using an obtundent in dentistry?
1) To reduce post-operative sensitivity
2) To promote the healing process
3) To strengthen the tooth structure
4) To whiten the tooth
An obtundent is used to reduce post-operative sensitivity by sealing the dentinal tubules and protecting the pulp.
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 polymerization shrinkage of Bis-GMA?
1) 1-2%.
2) 3-4%.
3) 5-6%.
4) 5%.
Bis-GMA undergoes a free radical addition polymerization reaction with a shrinkage of about 1-2%, forming a highly rigid cross-linked setting material.