Mental foramen on resorbed ridge: how to raise a flap?

Of course every case is different. Using a CT scan to assess the foramen location and also the anterior loop when considering implants. A mid crestal incision that is extensive enough along the arch is usually safe. It allows for careful reflection and a safe procedure

Keep the crestal incision toward the lingual. Use a 2x2 gauze pad to blunt dissect with pressure after initially elevating the flap from at least the cuspid anteriorly to the 2nd molar posteriorly. The blunt pressure with the gauze permits you no not injure or cut accidentally the mental bundle. You should see the mental nerve as you continue to push the flap downward. The nerve appears as a piece of spaghetti emerging from the foramen, or it can be a wide band of nerve tissue in a fan-like shape. But it is clearly demarked from the foramen walls as it emerges while connected to the flap. Now as to implant placement, as a previous Dr. commented, a CTscan is essential because of the need to know where the anterior loop curves and its path back into the mental bundle. It is also important to see where the mandibular nerve is as it moves anteriorly from the 1st molar area to the second bicuspid , first bicuspid and so on. Using the CTscan permits knowing both depth and height of the implants that might be placed. Hope this helps. Dr. Marshall

In addition to the previously reviewed by colleague I would like to consider that the CT scan will help but not solve completely. Then use the palpation and the punction During The local anesthesia to determine exactly the foramen location. So you will be able to avoid the region to perform incision and elevation of the flap with the smallest trauma possible. Prefer instrumental blunt and not sharp. Do not perform near the foramen relaxing incisions. Take extreme care with flap retractors. Remember that if there is still doubts you can still perform intraoperative radiographs.

Develop the surgical plane under the periosteum, the nerve emerges in this plane and you can visualize it. Keep it retracted to protect it. That's how it is done.

An additional comment regarding the CT. Generally when there is so much resorption the area must have been edentulous for a long time and patient is likely to have a removable prosthetic. You may place a radioopaque material such as GP in the the removable prosthetic and have the CT taken with the prosthesis in place. This would serve as a good reference point for the position of the foramen intraorally. If the patient does not have such prosthesis, an inexpensive baseplate or stayplate can be fabricated for that purpose. Comparing the position of the GP in the baseplate intraoral oh and its position on the CT scan should provide a fairly accurate estimate of th clinical position of the mental foramen intraorally. Hope you find this information useful.