EFDA Dental Materials & Equipment Maintenance 4 — Questions and Answers
Question 1: Which curing light intensity is considered the minimum for adequate polymerization of composite resin?
- 200 mW/cm²
- 400 mW/cm² (Correct answer)
- 600 mW/cm²
- 1000 mW/cm²
Correct answer: 400 mW/cm²
A minimum irradiance of 400 mW/cm² is generally required to achieve adequate polymerization depth and degree of conversion in composite resins.
Question 2: What is the function of a matrix band during a Class II composite restoration?
- Provide a temporary wall to replace the missing proximal surface during condensation (Correct answer)
- Hold the rubber dam in place
- Reflect light from the curing unit
- Prevent contamination from the gingival sulcus
Correct answer: Provide a temporary wall to replace the missing proximal surface during condensation
A matrix band recreates the proximal wall of the tooth, allowing the composite to be condensed against it and achieving proper contour and contact.
Question 3: Which solvent is recommended to clean composite resin that has not yet been light-cured from instruments?
- Water
- Alcohol (isopropyl) (Correct answer)
- Acetone
- Glutaraldehyde
Correct answer: Alcohol (isopropyl)
Isopropyl alcohol effectively dissolves uncured composite resin from instruments without damaging them.
Question 4: When using an ultrasonic scaler, the water spray serves which critical function?
- Improve patient comfort only
- Cool the tip and lavage the surgical site to prevent thermal damage (Correct answer)
- Increase the frequency of vibration
- Sterilize the working area
Correct answer: Cool the tip and lavage the surgical site to prevent thermal damage
The water coolant prevents heat buildup from ultrasonic vibration that could damage the pulp, and flushes debris from the subgingival area.
Question 5: What is a key reason why dental impression materials should be poured promptly after removal from the mouth?
- Syneresis or imbibition can alter the dimensional accuracy of the impression (Correct answer)
- The material becomes too rigid for pouring
- Setting reaction of the stone is inhibited by contact with impression material
- Color changes make it difficult to identify defects
Correct answer: Syneresis or imbibition can alter the dimensional accuracy of the impression
Alginate and hydrocolloid impressions undergo syneresis (shrinkage) or imbibition (expansion) if not poured immediately, causing dimensional inaccuracies in the resulting model.
Question 6: Which action is required when a sterilization pouch's chemical indicator does NOT change color after a cycle?
- Use the instruments and retest next cycle
- Re-run the load and quarantine items until biological indicator results are confirmed (Correct answer)
- Discard the pouch and use unpackaged instruments
- Increase the temperature for the next cycle only
Correct answer: Re-run the load and quarantine items until biological indicator results are confirmed
A failed chemical indicator suggests the sterilization parameters were not met; the load must be re-processed and quarantined pending biological indicator confirmation.
Question 7: What effect does increased spatulation time have on zinc phosphate cement?
- Decreases setting time and weakens the mix
- Increases setting time and generates more heat
- Increases working time by dissipating heat on the cool slab (Correct answer)
- Shortens working time by accelerating the acid-base reaction
Correct answer: Increases working time by dissipating heat on the cool slab
Mixing zinc phosphate cement over a large, cool glass slab with extended spatulation dissipates heat and slows the acid-base reaction, thereby increasing working time.
EFDA Dental Materials & Equipment Maintenance 4
Which curing light intensity is considered the minimum for adequate polymerization of composite resin?