CIT Implant Design & Fabrication 3 — Questions and Answers
Question 1: The 'critical healing zone' concept in implant design refers to which anatomical region and its associated biological events?
- The periapical region where new bone trabeculae form first
- The coronal 2-3mm of crestal bone where biological width establishes (Correct answer)
- The apical third where vascular ingrowth initiates osseointegration
- The implant body mid-portion where peak stress concentrations occur
Correct answer: The coronal 2-3mm of crestal bone where biological width establishes
The coronal crestal bone region is the 'critical healing zone' where biological width establishment determines long-term crestal bone stability.
Question 2: A bone-level implant placed at the crestal bone with a 4.1mm platform requires an abutment with which emergence profile consideration?
- Immediate wide emergence to match natural tooth contour
- Narrow emergence that gradually widens to the crown diameter (Correct answer)
- Straight vertical emergence with no angulation compensation
- Concave emergence to create pontic-style soft tissue support
Correct answer: Narrow emergence that gradually widens to the crown diameter
A sub-crestal or crestal bone-level implant requires a gradually widening emergence profile to support peri-implant soft tissue architecture and mimic natural tooth anatomy.
Question 3: When selecting implant diameter for a mandibular first molar site with adequate bone width, which dimension is most commonly recommended?
- 3.0mm narrow diameter
- 3.5mm standard narrow
- 4.5-5.0mm wide diameter (Correct answer)
- 6.0mm extra-wide diameter
Correct answer: 4.5-5.0mm wide diameter
Wide-diameter implants (4.5-5.0mm) are preferred for mandibular molar sites to better replicate the wider root footprint and distribute occlusal forces.
Question 4: In laser surface modification of titanium implants (SLActive/Laser-Lok), what is the primary mechanism for enhanced soft tissue integration?
- Increased surface hydrophilicity attracting plasma proteins
- Parallel circumferential microgrooves that orient connective tissue fibers perpendicularly (Correct answer)
- Removal of the titanium oxide layer to expose pure metal
- Creation of a biofilm-resistant nanosmooth surface texture
Correct answer: Parallel circumferential microgrooves that orient connective tissue fibers perpendicularly
Laser-Lok microgrooves create a physical template that guides connective tissue fiber orientation perpendicular to the implant surface, creating a functional soft tissue attachment.
Question 5: A 'morse taper' internal connection in an implant system refers to which design characteristic?
- A threaded internal channel requiring high torque to seat the abutment
- A conical friction-fit connection with a taper of 5-8 degrees (Correct answer)
- A parallel internal hex with a locking O-ring mechanism
- A butt-joint connection with an anti-rotational index only
Correct answer: A conical friction-fit connection with a taper of 5-8 degrees
Morse taper connections use a precise conical fit (5-8°) creating a cold-weld friction seal that minimizes micromovement and the implant-abutment microgap.
Question 6: Which factor most critically determines the minimum required bone height above the inferior alveolar nerve (IAN) when placing a standard 10mm implant?
- The implant surface treatment type used
- A minimum 2mm safety margin below the implant apex (Correct answer)
- The cortical bone density of the mandible at that site
- The patient's parafunctional habits and occlusal load
Correct answer: A minimum 2mm safety margin below the implant apex
A minimum 2mm safety margin between the implant apex and the IAN canal is the standard to prevent nerve injury from drilling or implant pressure.
Question 7: The 'prosthetic table' concept in wide-platform implants is designed to:
- Support a larger volume of regenerative bone graft material
- Provide a broader implant-crown junction to reduce cantilever stress on the abutment screw (Correct answer)
- Increase the total implant surface area for enhanced osseointegration
- Allow multiple abutments to be connected to a single implant platform
Correct answer: Provide a broader implant-crown junction to reduce cantilever stress on the abutment screw
A wider prosthetic table (platform) on broad-diameter implants reduces the lever arm and bending stress on the abutment screw, improving long-term mechanical reliability.
CIT Implant Design & Fabrication 3
The 'critical healing zone' concept in implant design refers to which anatomical region and its associated biological events?