Floor of nose and Nasal spine
Although variable, the nasal floor is typically situated 5-9mm below the level of inferior turbinates. The inferior piriform rim is used as a guideline for the height of the opposing cortical plate to determine the implant length, and care should be taken to prevent perforation of the nasal floor and mucosa during implant placement.
Another consideration is the gradual loss of canine eminence distal to the lateral piriform rim in edentulous patients, forming a recess behind it. Implants placed in this position in extremely resorbed maxilla which is palatally placed and closer to nasal cavity will penetrate the nasal cavity.