CIT CIT Prosthetic Components & Restoration 4 — Questions and Answers
Question 1: Which type of implant-supported prosthesis uses a metal bar connecting multiple implants to support a removable overdenture?
- Fixed full-arch bridge
- Bar-retained overdenture (Correct answer)
- Screw-retained implant crown
- Cement-retained bridge
Correct answer: Bar-retained overdenture
A bar-retained overdenture uses a metal bar spanning multiple implants, with clips or attachments in the denture that snap onto the bar for retention.
Question 2: When fabricating a zirconia implant crown, which factor is most critical to account for during milling to ensure accurate final fit?
- Shade selection before sintering
- Sintering shrinkage compensation (approximately 20-25%) (Correct answer)
- Occlusal surface texture
- Shade matching after glazing
Correct answer: Sintering shrinkage compensation (approximately 20-25%)
Zirconia must be milled oversized by approximately 20-25% to compensate for the shrinkage that occurs during the sintering process.
Question 3: A patient has a single-unit implant crown with a 5 mm emergence profile. Which abutment height is most appropriate for a cement-retained restoration with 2 mm of soft tissue?
- 1 mm abutment height
- 2 mm abutment height (Correct answer)
- 4 mm abutment height
- 6 mm abutment height
Correct answer: 2 mm abutment height
When soft tissue is 2 mm, a 2 mm abutment height ensures adequate cement retention while keeping the margin accessible for cement removal.
Question 4: What is the primary purpose of a custom impression coping in implant prosthodontics?
- To protect the implant during healing
- To replicate the exact soft tissue contour around the implant in the final impression (Correct answer)
- To set the vertical dimension of occlusion
- To serve as the final abutment
Correct answer: To replicate the exact soft tissue contour around the implant in the final impression
Custom impression copings capture the unique gingival contours that have been shaped during the provisional restoration phase, ensuring the master cast replicates the actual peri-implant tissue architecture.
Question 5: In an All-on-4 implant-supported prosthesis, the two posterior implants are typically angled at approximately how many degrees from vertical?
- 10–15 degrees
- 30–45 degrees (Correct answer)
- 55–60 degrees
- 70–75 degrees
Correct answer: 30–45 degrees
Posterior implants in the All-on-4 concept are typically angled 30–45 degrees to maximize bone contact, avoid anatomical structures, and extend the posterior cantilever support.
Question 6: Which retention mechanism in implant-supported overdentures requires the least amount of interocclusal space?
- Bar and clip attachment
- Locator attachment
- Ball and socket attachment
- Magnetic attachment (Correct answer)
Correct answer: Magnetic attachment
Magnetic attachments require the least vertical space of all overdenture retention systems, making them suitable for patients with minimal interarch distance.
Question 7: When torquing an abutment screw, which technique best ensures accurate final torque delivery?
- Apply torque in one continuous motion
- Pre-torque to half value, wait 10 minutes, then apply final torque (Correct answer)
- Use a manual driver without a torque wrench for better tactile feedback
- Torque until resistance is felt, then add one quarter turn
Correct answer: Pre-torque to half value, wait 10 minutes, then apply final torque
Pre-torquing to half the recommended value, waiting 10 minutes to allow stress relaxation, and then applying final torque helps achieve accurate, stable seating of the abutment screw.
CIT CIT Prosthetic Components & Restoration 4
Which type of implant-supported prosthesis uses a metal bar connecting multiple implants to support a removable overdenture?