CIT CIT Prosthetic Components & Restoration 5 — Questions and Answers
Question 1: Which material is most commonly used for provisional implant-supported restorations due to its ease of modification and repairability?
- High-strength zirconia
- PMMA (polymethylmethacrylate) (Correct answer)
- Full-contour lithium disilicate
- Cobalt-chromium alloy
Correct answer: PMMA (polymethylmethacrylate)
PMMA is the preferred provisional material because it can be easily added to, trimmed, and polished chairside, allowing iterative refinement of tissue contours and occlusion.
Question 2: In implant prosthodontics, what term describes the misfit at the implant-abutment interface that can lead to microleakage and bone loss?
- Rotational freedom
- Microgap (Correct answer)
- Platform mismatch
- Taper lock failure
Correct answer: Microgap
A microgap at the implant-abutment interface allows bacterial colonization and micromovement, contributing to marginal bone loss and peri-implantitis.
Question 3: A screw-access channel in a screw-retained crown is typically sealed with which material after torquing the prosthetic screw?
- Zinc oxide eugenol cement
- PTFE (Teflon) tape followed by composite resin (Correct answer)
- Zinc phosphate cement
- Glass ionomer base only
Correct answer: PTFE (Teflon) tape followed by composite resin
PTFE tape is placed over the screw head to protect it, and then composite resin seals the access channel, allowing future retrievability by removing the composite.
Question 4: Which occlusal scheme is generally recommended for implant-supported full-arch fixed prostheses to minimize lateral forces on implants?
- Canine-guided occlusion
- Group function occlusion
- Lingualized occlusion
- Bilateral balanced occlusion (Correct answer)
Correct answer: Bilateral balanced occlusion
Bilateral balanced occlusion distributes lateral forces evenly across all implants during excursive movements, reducing the risk of overloading individual implants or components.
Question 5: What is the function of an anti-rotation feature on an implant abutment connection?
- To increase cement retention area
- To prevent the abutment from rotating independently of the implant body (Correct answer)
- To allow slight abutment movement for stress absorption
- To reduce the torque required during abutment placement
Correct answer: To prevent the abutment from rotating independently of the implant body
Anti-rotation features such as hex, octagon, or spline connections physically lock the abutment to the implant to prevent rotational movement, which is essential for single-unit restorations.
Question 6: When evaluating the fit of an implant framework at try-in, which radiographic finding confirms passive fit?
- Uniform radiolucency between the abutment and implant
- Complete seating of all abutments with no gap visible radiographically at each implant interface (Correct answer)
- A visible screw shadow on periapical radiograph
- Bone level at the implant shoulder on panoramic view
Correct answer: Complete seating of all abutments with no gap visible radiographically at each implant interface
Radiographic confirmation of passive fit requires that no gap is visible at any implant-abutment junction when each screw is tightened individually, confirming the framework seats completely at every implant.
Question 7: Which technique is used to verify the accuracy of a master cast by confirming that the implant analogs replicate the exact intraoral implant positions?
- Facebow transfer
- Verification jig (pick-up index) (Correct answer)
- Pantographic tracing
- Gothic arch tracing
Correct answer: Verification jig (pick-up index)
A verification jig is fabricated from the master cast and tried in the patient's mouth; if it seats passively at all implant connections simultaneously, the cast accurately reflects the intraoral implant positions.
CIT CIT Prosthetic Components & Restoration 5
Which material is most commonly used for provisional implant-supported restorations due to its ease of modification and repairability?