If there is a 10mm distance from the alveolar crest to the inferior alveolar nerve, what is the MAXIMUM implant length that can be placed?

Correct answer: B. 8mm

• A. A 10mm implant in 10mm of available bone would have NO safety margin — risk of damaging the IAN.
• B. Standard implant planning requires a MINIMUM SAFETY MARGIN of 2mm between the apex of the implant and the inferior alveolar nerve. With 10mm of available bone: 10mm - 2mm safety = 8mm maximum implant length. An 8mm implant can be safely placed with a 2mm buffer to the nerve. Most surgeons would not place a 10mm implant in 10mm of bone.
• C. A 9mm implant with only 1mm safety margin is too close to the IAN — the standard minimum safety margin is 2mm.
• D. 7mm is too conservative — with 10mm of available bone height, 8mm implants can safely be placed with a 2mm safety margin.