Dental Material MCQs - Gypsum Products

# Model plaster (white) used to cast study models before mixing with water, is largely composed of:
A. CaO
B. CaCO3
C. (CaSO4)2. 1/2H2O
D. CaSO4.2H2O

# The product, which is obtained by calcining under steam pressure at 120-130°C or by dehydrating gypsum in the presence of sodium succinate is:
A. Alpha - hemihydrates
B. Beta - hemihydrates
C. Calcium sulphate dihydrate
D. Orthorhombic anhydrate

# Water powder ratio of dental stone and plaster is respectively:
A. 0.28 and 0.6
B. 0.6 and 0. 28
C. 0.6 and 3.2
D. 0.28 and 0.98

# Type III Dental gypsum is:
A. Class II stone
B. Densite
C. Class I stone or hydrocal
D. Model or lab plaster

# Green strength with reference to plaster means:
A. Dry strength
B. Compressive strength
C. Strength of dental stone due to green colour
D. The wet strength

# Beta hemihydrate particles absorb:
A. more water
B. less water
C. no water
D. none of the above

# Water of reaction needed to react completely with 100 g of calcium sulphate hemihydrates to convert it to calcium sulphate dihydrate:
A. 18.6ml
B. 22.2ml
C. 30.4ml
D. 45.3ml

# Powders of dental plaster and dental stone differ mainly in:
A. Solubility
B. Shelf life
C. Chemical formula
D. Particle porosity

# Plaster of paris is mixed in:
A. Plastic bowl
B. Rubber bowl
C. Glass bowl
D. Metal bowl

# Impression plaster containing potato starch is called:
A. Plaster of paris
B. Soluble plaster
C. Anti - expansion solution
D. Die stones

# Die is:
A. Impression of single tooth
B. Impression of whole teeth
C. Replica of single tooth
D. Replica of whole teeth

# Balanced stone is dental stone:
A. Which undergoes rapid expansion
B. In which accelerators or retarders have been added according to need
C. In which amount of water of hydration is controlled
D. In which the crystals are all of uniform size

# The main ingredient in dental plaster is:
A. Calcium sulphate hemihydrate
B. Calcium phosphate
C. Calcium anhydrate
D. Calcium sulphate dihydrate

# The strength of the gypsum specimen when the water in excess of that required for the hydrate of the hemihydrate is left in the specimen is called?
A. Dry strength
B. Green strength
C. Water strength
D. Compressive strength

# Accelerators and retarders are used with gypsum products mainly to control:
A. Setting time
B. Setting expansion
C. Hardness of the set product
D. None of the above

# Gypsum is used for?
A. Impressions
B. Casts
C. Die
D. Casts and Dies

# The hygroscopic technique is associated with:
A. Investment
B. Hydrocolloids
C. Amalgam
D. Silicate

# The main difference between dental stone and dental plaster is:
A. Chemical composition
B. Shelf life
C. Shape and size of particles
D. Solubility in water

# The most commonly used accelerator in gypsum product is:
A. Sodium fluoride
B. Potassium fluoride
C. Potassium sulfate
D. Aluminium sulfate

# As per ADA No. 25, minimum amount of setting expansion required for type V gypsum product is:
A. 0.05
B. 0.10
C. 0.15
D. 0.20

# Which is a gypsum product?
A. Stone
B. Plaster
C. Investment
D. All of the above

# Plaster of paris:
A. Is wet calcined hemihydrate
B. Has porous and irregular crystals
C. Is alpha hemihydrate
D. Has a W / P of 0.2

# In plaster of paris the setting time is primarily altered by:
A. Altering P / L Ratio
B. Altering temperature of mixing water
C. Speed and length of hand spatulation
D. Addition of accelerators and retarders

# Type I gypsum product is also called:
A. Impression plaster
B. Class I stone/ Hydrocal
C. Class II stone/Densite
D. Model plaster

# The beta hemihydrate of gypsum requires more water to float its powder particles because:
A. They are more regular in shape and dense
B. They are more regular in shape and highly porous
C. They are more irregular in shape and porous
D. They are more dense and prismatic in shape

# Setting of Plaster of Paris is result of:
A. Difference in solubility of CaSO4 1/2 H2O + CaSO4•2H2O
B. Reaction between CaS04 2H2O and water
C. Nucleation and growth of CaSO4.1/2 H2O crystals
D. Reaction between hemihydrate and dihydrate

# Placing cast under tap water is to be avoided as:
A. H2O interferes with hygroscopic expansion
B. H2O In hibits polymerization of dental resin
C. H2O interferes with crystallization of dihydrate
D. Gypsum is slightly soluble in water and the surface of the cast will be eroded

# Gillmore needle is used for:
A. Testing the strength of plaster of paris
B. Evaluating the setting time of plaster of paris
C. Testing the metal hardness
D. Testing the purity of noble metals

# 2 % solution of borax is used as a surface hardening agent for:
A. Casting stone
B. Dental plaster
C. Dental stone
D. Type IV gypsum

# Gypsum product having least expansion:
A. Impression plaster
B. Model plaster
C. Stone plaster
D. Die stone

# Modifiers are added to gypsum mainly to:
A. Modify setting time
B. Modify setting expansion
C. Modify strength
D. Decrease the porosity

# Most commonly used retarder in gypsum:
A. Na2SO4
B. NaCl
C. Citrates
D. K2SO4

# ADA specification number for gypsum products are described under:
A. 1
B. 4
C. 12
D. 25

# The setting expansion of gypsum products can be reduced by:
A. Increased spatulation
B. Adding potassium sulfate
C. Less water powder ratio
D. Allowing setting under water

# Finer particle size of silica:
A. Slower the hygroscopic expansion
B. Greater the hygroscopic expansion
C. Normal setting expansion
D. No setting expansion

# A rough/ chalky surface of the cast is due to:
A. Not waiting for 20 min before pouring
B. Excess wetting agent left on impression
C. Air incorporation in the mix
D. All of the above

# The function of 2% potassium sulphate in a gypsum product is:
A. To regulate the setting expansion
B. Regulate setting time
C. Acts as retarder
D. None

# Plaster mix:
A. Rapid spatulation results in decreased setting time
B. 2% potassium sulphate is accelerator
C. Citrates are retarders
D. All of the above

# The strength of gypsum products is generally expressed in terms of:
A. Tensile strength
B. Wet strength
C. Green strength
D. Compressive strength

# Water: powder ratio for class IV stone is:
A. 0.22-0.24
B. 0.24-0.28
C. 0.65-0. 70
D. 0.45-0.50

# Within practical Limits, using Less water in mixing plaster will result in a set product that:
A. Contracts
B. Is stronger
C. Is more porous
D. Is less brittle

# Increased spatulation is case of dental stone results in:
A. Increased working time
B. Increased setting time
C. Decreased setting time
D. None of the above

# In dental materials setting time is measured by which test?
A. Rockwell test
B. Cold blend test
C. Vickers test
D. Vicat needle method

# Which of the following is false regarding setting of plaster products?
A. Setting expansion increases with increase in nucleic density
B. Most accurate method of controlling setting expansion is by chair side addition of chemicals
C. Potassium sulphate is an accelerator and reduces the setting expansion
D. Maximum acceleration effect for sodium sulphate is approximately 3.4%

# Which of the following is incorrect about non-gypsum die material?
A. All impression materials are compatible with these
B. Polyester produces the most accurate dies
C. Epoxy resin dies are undersized but are used due to their higher abrasion resistance
D. Metal dies are preferable to high strength gypsum dies for captek restoration

Procedures undertaken in preventive orthodontics are all EXCEPT:

 # Procedures undertaken in preventive orthodontics are all EXCEPT:
A. Parents education
B. Checkup for oral habits
C. Extraction of supernumerary teeth
D. Space regaining

The correct answer is D. Space regaining. 

Procedures of preventive orthodontics: 
1. Parent education 
2. Caries control 
3. Care of deciduous dentition 
4. Management of ankylosed tooth 
5. Maintenance of quadrant wise tooth shedding timetable. 
6. Checkup for oral habits and habit-breaking appliances if necessary. 
7. Occlusal equilibration if there are any occlusal pre-maturities. 
8. Prevention of damage to occlusion, e.g. Milwaukee braces 
9. Extraction of supernumerary teeth 
10. Space maintenance 
11. Management of deeply locked first permanent molar 
12. Management of abnormal frenal attachments 

Simple retraction of maxillary incisors using maxillary molars as anchorage is an example of:

 # Simple retraction of maxillary incisors using maxillary molars as anchorage is an example of:
A. Simple anchorage
B. Reciprocal anchorage
C. Stationary anchorage
D. Intermaxillary anchorage

The correct answer is C. Stationary anchorage. 

An anchor tooth or source, which does not move against the forces of teeth to be pulled is stationary
anchorage. In a real sense, only the extraoral source of anchorage derived from headgear would be a stationary anchorage. The anchor tooth being housed in a bioactive environment would show some degree of movement and hence cannot be classified as a stationary anchorage in a real sense.

Bone can be induced to grow at surgically created sites by the method called:

 # Bone can be induced to grow at surgically created sites by the method called:
A. Osteogenesis
B. Distraction osteogenesis
C. Bone wax
D. Green stick fracture

The correct answer is B. Distraction osteogenesis.

• Distraction osteogenesis is the method of inducing bone to grow at surgically created sites. 
• Russian Surgeon Ilizarov discovered in 1950's that if cuts were made through the cortex of a long bone of the limbs, the arm or leg then could be lengthened by tension to separate bony segments. 

• Currently it is believed that best results are obtained if this type of distraction starts after a few days of initial healing and callus formation and if the segments are separated at a rate of 0.5 - 1.5 mm/day. 

• Also this technique is employed for lengthening of mandible and inducing maxillary growth by separating cranial and facial bone at their sutures. 

Perspiration and redness of the cheek and ear after eating

 # A 58-year-old woman underwent left superficial parotidectomy for a pleomorphic adenoma 2 years ago. She presents with complaints of occasional perspiration and redness of the left cheek and ear after eating. Which of the following nerves is the most likely source of these complaints? 
A. Great auricular
B. Frontal branch of the facial nerve
C. Auriculotemporal
D. Lingual

The correct answer is C. Auriculotemporal.

The auriculotemporal syndrome is an unusual phenomenon, which arises as a result of damage to the auriculotemporal nerve and subsequent reinnervation of sweat glands by parasympathetic salivary fibers.

The patient typically exhibits flushing and sweating of the involved side of the face, chiefly in the temporal area, during eating. The severity of this sweating may often be increased by tart foods. Of further interest is the fact that profuse sweating may be evoked by the parenteral administration of pilocarpine or eliminated by the administration of atropine or by a procaine block of the auriculotemporal nerve.

Reference: Shafer's Textbook of Oral Pathology, 7th Edition.

The diameter of the tip of a periodontal probe is:

 # The diameter of the tip of a periodontal probe is:
A. 0.25 mm
B. 0.5 mm
C. 0.75 mm
D. 1 mm

The correct answer is B. 0.5 mm.

Periodontal probes are used to measure the depth of pockets and to determine their configuration. The typical probe is a tapered, rodlike instrument calibrated in millimeters, with a blunt, rounded tip. There are several other designs with various millimeter calibrations. The World Health Organization (WHO) probe has millimeter markings and a small, round ball at the tip. Ideally, these probes are thin, and the shank is angled to allow easy insertion into the pocket. Furcation areas can best be evaluated with the curved, blunt Nabers probe. When measuring a pocket, the probe is inserted with a firm, gentle pressure to the bottom of the pocket. The shank should be aligned with the long axis of the tooth surface to be probed. Several measurements are made to determine the level of attachment along the surface of the tooth.

Reference: Carranza's Clinical Periodontology 12th edition.

Which of the following may create gingival deformities that require gingivoplasty to eliminate the defects?

 # Which of the following may create gingival deformities that require gingivoplasty to eliminate the defects?
A. Erosive linchen planus 
B. Desquamative gingivitis 
C. Acute herpetic gingivostomatitis 
D. Necrotising ulcerative gingivitis 

The correct answer is D. Necrotising ulcerative gingivitis.

■ Shelf-like gingival margins after healing may result in plaque accumulation. 
■ The gingiva is reshaped with periodontal knife or with electrosurgery. This process of eliminating the defects by reshaping is called as gingivoplasty. 
■ Gingival deformities are seen in gingival disease:  (Asked in AIIMS 1999) (ANUG) 
Surgical procedure for severe tissue destruction in ANUG infection is:  (Asked in COMED 2011) (Reshaping the gingiva, Gingivoplasty)