MDS PREP
What is the most corrodible phase in the low-copper amalgam system?
1) Sn7. Hg
2) ? (gamm1) phase
3) Cu3Sn phase
4) ? (delt1) phase
The Sn7. Hg or ? (gamm1) phase is the most corrodible in the low-copper amalgam system.
What is the typical concentration of sodium chloride used as an accelerator in dental plaster?
1) 5%.
2) 10%.
3) 15%.
4) 20%.
A concentration of sodium chloride of about 5% is commonly added to dental plaster to accelerate the setting reaction and reduce the setting time.
What are the two types of alginate impression materials according to ADA specification No. 18?
1) Type I - Fast set with a setting time of 1-2 minutes, Type II - Normal set with a setting time of 2-4 minutes
2) Type I - Slow set with a setting time of 3-5 minutes, Type II - Medium set with a setting time of 4-6 minutes
3) Type I - Fast set with a setting time of 1-2 minutes, Type II - Slow set with a setting time of 3-5 minutes
4) Type I - Normal set with a setting time of 1-2 minutes, Type II - Fast set with a setting time of 2-4 minutes
ADA specification No. 18 categorizes alginate impression materials into two types: Type I (Fast set) with a setting time of 1-2 minutes and Type II (Normal set) with a setting time of 2-4 minutes.
What is the recommended force for condensing a composite resin using a 0.5 mm diameter condenser nib?
1) 3.75 pounds
2) 8.43 pounds
3) 15 pounds
4) 0.04-0.4 µm
The recommended force for condensing a composite resin using a 0.5 mm diameter condenser nib is 3.75 pounds. This force is considered optimal and is well within the physiologic limits of the tooth.
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 maximum weight loss allowed for a specimen surface according to the specification?
1) 0.04 mg/cm³
2) 0.69 mg/cm²
3) 0.23 mg/cm²
4) There is no maximum weight loss mentioned
The specification mentions that the weight loss must not be greater than 0.04 mg/cm³ from the specimen surface, which is considered negligible from a clinical standpoint.
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 type of dental cement is used in cases of rampant caries and unhygienic oral conditions?
1) Zinc polyacrylate
2) Calcium sulfate
3) Zinc oxide-eugenol
4) Calcium hydroxide
Calcium hydroxide is used in cases of rampant caries and unhygienic oral conditions due to its antibacterial and tissue-dissolving properties.