CIT CIT Prosthetics & Restoration 4 — Questions and Answers
Question 1: Which cement type is most appropriate for retrievable implant-supported crowns requiring periodic maintenance access?
- Resin-modified glass ionomer with reduced film thickness
- Zinc phosphate cement for permanent retention
- Temporary provisional cement with low retentive strength (Correct answer)
- Self-adhesive resin cement for definitive seating
Correct answer: Temporary provisional cement with low retentive strength
Temporary provisional cement allows retrievability for maintenance while providing adequate short-term retention.
Question 2: When designing a screw-retained implant crown, what is the ideal screw access channel angulation relative to the occlusal surface?
- 0–15 degrees off-axis to avoid esthetic compromise (Correct answer)
- 30–45 degrees to improve torque delivery
- 60–75 degrees for maximum lingual access
- Perpendicular (90 degrees) to the occlusal plane
Correct answer: 0–15 degrees off-axis to avoid esthetic compromise
Screw channels within 0–15 degrees of the implant long axis maintain adequate structural integrity and esthetics.
Question 3: A patient presents with a fractured zirconia implant crown three months after delivery. The most likely contributing factor is:
- Excessive occlusal contacts in lateral excursion (Correct answer)
- Improper shade selection during fabrication
- Insufficient emergence profile design
- Over-torquing the retention screw at delivery
Correct answer: Excessive occlusal contacts in lateral excursion
Lateral excursive contacts create bending stresses that exceed zirconia's fracture toughness in unsupported areas.
Question 4: An implant-supported fixed partial denture (FPD) pontic rests on tissue. Which pontic design minimizes tissue irritation while maintaining cleansability?
- Bullet pontic with convex apical surface
- Sanitary (hygienic) pontic with 3 mm tissue clearance
- Modified ridge-lap pontic with concave lingual surface (Correct answer)
- Ovate pontic seated 1–2 mm into soft tissue
Correct answer: Modified ridge-lap pontic with concave lingual surface
The modified ridge-lap design provides esthetic contour on the buccal while allowing floss access on the lingual.
Question 5: What is the primary purpose of using a torque wrench when seating an abutment on an implant?
- To prevent stripping the internal hex connection
- To achieve manufacturer-specified preload without plastic deformation (Correct answer)
- To verify implant osseointegration stability
- To confirm proper emergence profile angulation
Correct answer: To achieve manufacturer-specified preload without plastic deformation
Correct torque establishes optimal screw preload, clamping the abutment without yielding the screw material.
Question 6: Which occlusal scheme is generally recommended for a single implant-supported molar crown in a dentate patient?
- Group function with heavy balancing contacts
- Bilateral balanced occlusion across all teeth
- Light centric stops with freedom in centric and no excursive contacts on the implant crown (Correct answer)
- Canine-guided occlusion centered on the implant crown
Correct answer: Light centric stops with freedom in centric and no excursive contacts on the implant crown
Light centric loading with excursive disclusion protects the implant-bone interface from lateral overload.
Question 7: During final impression for an implant crown, a snap-on impression coping is used. Which technique does this describe?
- Closed-tray (indirect) impression technique (Correct answer)
- Open-tray (direct) pickup impression technique
- Digital intraoral scan with engagement key
- Analog transfer using a silicone index
Correct answer: Closed-tray (indirect) impression technique
Closed-tray technique uses a coping that remains in the mouth; the impression records the external form and the coping snaps out after set.
CIT CIT Prosthetics & Restoration 4
Which cement type is most appropriate for retrievable implant-supported crowns requiring periodic maintenance access?