CIT CIT Bone Grafting & Osseointegration 5 — Questions and Answers
Question 1: Which property of beta-tricalcium phosphate (β-TCP) makes it preferable to hydroxyapatite (HA) in certain ridge augmentation cases?
- Faster resorption rate allowing replacement by native bone (Correct answer)
- Higher initial compressive strength
- Greater osteoinductive capacity
- Lower risk of inflammatory reaction
Correct answer: Faster resorption rate allowing replacement by native bone
β-TCP resorbs more rapidly than HA, creating space that is replaced by the patient's own bone, which is beneficial in sites where full bone substitution is desired.
Question 2: The 'critical size defect' concept in bone grafting refers to which of the following?
- The smallest defect that will not heal spontaneously without intervention (Correct answer)
- The maximum defect size that can be treated with particulate graft alone
- The defect volume that requires simultaneous implant placement
- The minimum defect requiring a titanium mesh for containment
Correct answer: The smallest defect that will not heal spontaneously without intervention
A critical size defect is defined as the smallest osseous defect that will not heal completely without augmentation during the lifetime of the animal or patient.
Question 3: During second-stage implant uncovery, the clinician observes fibrous encapsulation around the implant rather than bone. This outcome is most consistent with which primary failure cause?
- Micromotion exceeding 100–150 µm during the healing phase (Correct answer)
- Insufficient implant surface roughness
- Delayed loading protocol beyond 6 months
- Over-torquing during placement causing necrosis
Correct answer: Micromotion exceeding 100–150 µm during the healing phase
Excessive micromotion during healing causes fibrous tissue formation rather than direct bone apposition, classically resulting in fibrous encapsulation.
Question 4: Which of the following best describes the role of tenting screws in GBR procedures?
- They maintain space under the membrane to allow blood clot stabilization and bone fill (Correct answer)
- They anchor the membrane to prevent bacterial infiltration
- They accelerate angiogenesis by creating micro-perforations in cortical bone
- They compress the graft to increase initial density
Correct answer: They maintain space under the membrane to allow blood clot stabilization and bone fill
Tenting screws prevent membrane collapse, preserving the protected space beneath that allows undisturbed clot organization and subsequent bone formation.
Question 5: A 58-year-old patient who received IV bisphosphonate therapy for metastatic cancer requires an implant. According to current guidelines, what is the most appropriate recommendation?
- Implant placement is contraindicated due to high MRONJ risk (Correct answer)
- Proceed normally with standard implant protocol
- Drug holiday of 2 weeks is sufficient to proceed safely
- Only pterygoid implants should be considered
Correct answer: Implant placement is contraindicated due to high MRONJ risk
IV bisphosphonates carry a significantly higher MRONJ risk than oral forms, making implant placement generally contraindicated in these patients.
Question 6: Cortical bone decortication (cortical perforation) is performed before particulate graft placement primarily to:
- Allow migration of osteogenic progenitor cells and vasculature from the medullary space (Correct answer)
- Increase the surface area for graft particle adhesion
- Reduce the risk of membrane exposure
- Prevent resorption of the overlying cortical plate
Correct answer: Allow migration of osteogenic progenitor cells and vasculature from the medullary space
Perforating the cortical plate opens access to marrow-derived stem cells and blood supply, both essential for graft vascularization and osteogenesis.
Question 7: Which implant surface characteristic is most directly associated with improved osseointegration speed in poor-quality (Type IV) bone?
- Increased surface roughness (Sa 1–2 µm) via sandblasting and acid-etching (SLA) (Correct answer)
- Mirror-polished machined surface
- Hydrocarbon-contaminated surface
- Anodized smooth surface
Correct answer: Increased surface roughness (Sa 1–2 µm) via sandblasting and acid-etching (SLA)
SLA surfaces with moderate roughness (Sa 1–2 µm) maximize protein adsorption and osteoblast attachment, which is especially critical in low-density Type IV bone.
CIT CIT Bone Grafting & Osseointegration 5
Which property of beta-tricalcium phosphate (β-TCP) makes it preferable to hydroxyapatite (HA) in certain ridge augmentation cases?