CIT Occlusion & Bite Registration in Implant Dentistry — Questions and Answers
Question 1: Why must occlusal forces on implant-supported restorations be managed more carefully than on natural teeth?
- Implants are harder than natural teeth and will damage opposing enamel
- Implants lack a periodontal ligament, so they have no shock-absorbing mechanism or proprioceptive feedback (Correct answer)
- Implant crowns are made of porcelain, which is more brittle than natural enamel
- Osseointegrated implants move freely in bone, making occlusal adjustment difficult
Correct answer: Implants lack a periodontal ligament, so they have no shock-absorbing mechanism or proprioceptive feedback
Natural teeth have a periodontal ligament (PDL) that acts as a shock absorber and contains proprioceptive nerve fibers that sense bite force. Osseointegrated implants have no PDL, so they transmit occlusal forces directly to the bone without attenuation and without the fine tactile feedback that natural teeth provide.
Question 2: Which occlusal scheme is generally preferred for a full-arch implant-supported fixed prosthesis to minimize lateral stress on implants?
- Group function occlusion on the working side
- Canine-guided (mutually protected) occlusion (Correct answer)
- Lingualized occlusion with steep cuspal inclines
- Balanced occlusion with equal bilateral contacts in all excursions
Correct answer: Canine-guided (mutually protected) occlusion
Canine-guided or mutually protected occlusion is preferred for implant-supported restorations because it directs lateral excursive forces through the anterior teeth (or implants in that position), disoccluding the posterior implants and reducing the harmful lateral (non-axial) loading on posterior implants.
Question 3: During bite registration for an implant-supported crown, why is it important to have the patient bite lightly rather than at maximum force?
- Maximum force causes the registration material to set too quickly
- Maximum clenching compresses natural teeth in their sockets, potentially leading to an inaccurate registration that is too thin (Correct answer)
- Light biting prevents the temporary crown from fracturing during the record
- Maximum force is only appropriate for removable prosthetics
Correct answer: Maximum clenching compresses natural teeth in their sockets, potentially leading to an inaccurate registration that is too thin
Natural teeth can intrude 25–100 microns in their sockets under heavy occlusal load due to the PDL. If the patient bites hard during registration, the natural teeth are compressed; when they rebound, the bite record becomes too thin, and the final restoration may be fabricated in supraocclusion.
Question 4: A cantilever extension on an implant-supported bridge creates what type of potentially harmful force on the supporting implants?
- Axial compressive force, which is the most favorable loading direction
- Rotational and lever-arm forces that magnify stress at the implant-bone interface (Correct answer)
- Tensile forces only at the crown-abutment junction
- Uniform distribution of force across all implants equally
Correct answer: Rotational and lever-arm forces that magnify stress at the implant-bone interface
A cantilever acts as a lever. Forces applied to the unsupported end are magnified at the fulcrum (the most distal implant), creating rotational moments and non-axial stress at the implant-bone interface. This significantly increases the risk of mechanical complications and bone loss around the supporting implants.
Question 5: Which bite registration material is most commonly used in contemporary implant dentistry due to its dimensional accuracy and rigidity after setting?
- Zinc oxide eugenol (ZOE) paste
- Modeling compound (impression compound)
- Polyvinyl siloxane (PVS) bite registration material (Correct answer)
- Irreversible hydrocolloid (alginate)
Correct answer: Polyvinyl siloxane (PVS) bite registration material
Polyvinyl siloxane (PVS) bite registration materials are preferred because they have excellent dimensional stability, minimal distortion after setting, are rigid enough to maintain the recorded position during model mounting, and do not deform during trimming. Alginate lacks stability; ZOE is messy and brittle; modeling compound has thermal limitations.
Question 6: Parafunctional habits such as bruxism pose a particular risk to implant-supported restorations primarily because:
- Bruxism causes excessive salivary flow that corrodes titanium implants
- The high repetitive lateral forces exceed the implant system's design limits, increasing the risk of component fracture and bone loss (Correct answer)
- Bruxism patients cannot achieve osseointegration
- Nightguards are contraindicated in patients with implants
Correct answer: The high repetitive lateral forces exceed the implant system's design limits, increasing the risk of component fracture and bone loss
Bruxism generates repetitive high-magnitude lateral forces that are poorly tolerated by implants due to the absence of the PDL. These forces can lead to screw loosening, abutment or prosthesis fracture, implant fracture, and marginal bone loss. Night guards are commonly recommended (not contraindicated) to protect implant restorations.
CIT Occlusion & Bite Registration in Implant Dentistry
Why must occlusal forces on implant-supported restorations be managed more carefully than on natural teeth?