Figure 16. A scan taken 3 mm inferior to Figure 15 shows a distinct circular area of slightly lower signal than surrounding marrow around the root apex of the upper left central incisor. There is no cortical bone on the labial aspect of the root surface, which is at the level of the discharging sinus as ascertained clinically. There is a thick black line of low signal on the palatal aspect that indicates sclerosis and thickening of the palatal cortex of the dentoalveolar ridge, probably in response to the chronic infection.