What is Anatomic concavities
Anatomic concavities present in the lingual surface of the mandible, the sublingual fossa anteriorly and the submandibular fossa posteriorly. Normally assessment of the bone quantity is done by panaromic x-rays and since, it is a two dimensional representation, the concavities cannot be assessed. It is possible to see them only in the oblique sections in a dental CT- Scan. Especially in the mandibular second molar region extreme caution should be taken while planning an implant as the prominent internal oblique ridge gives a false sense of abundant bone, however, just inferior to the ridge lies the submandibular fossa. If a wide implant is placed directed in a straight axis it can perforate the lingual cortex. Therefore, it is prudent to evaluate the fossa by deep palpation, assess on oblique views on CT-scan and then plan the axis of the implant following that of the tooth to be replaced and not straight as will be discussed in the following units on treatment planning.