Determine the use of  OPG

An OPG is used to see the possibility for an anterior loop which is found to extend about 1-3 mm anterior to the mental foramen in about 12 per cent of cases. If the mandibular canal on an OPG approaches the mental foramen at the same height, the nerve always enters the distal portion of the foramen. However, a loop occurs when the mandibular nerve approaches from below  (the mental foramen), proceeds anteriorly to about 1-3 mm and curves upward and distally to enter the mesial aspect of mental foramen The anterior loop should be verified either by surgical exposure of the mental foramen or with a CT scan. A blunt curved probe is used to check the patency at the distal aspect from where the nerve exits. If not patent, it means that the nerve extends to the mesial side and that either it can be an anterior loop or the incisal branch of inferior alveolar nerve.