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Figure 14. (a) T1 weighted coronal image through midline of teeth shows a diamond shaped area of moderate signal (light grey) around the roots of the lower central incisors, extending from the mesial aspect of the lower lateral root apices to a point 1 cm lower in the midline. This corresponds to the abnormal area previously demonstrated on transverse MR images. It is demarcated around its sides and base by a thin dark grey/black line of low signal due to sclerotic bone. The lower right central incisor root apex is displaced laterally away from the midline by about 0.75 cm. (b) Coronal short tau inversion recovery (STIR) (fat suppressed) image comparable to (a). It shows the area described above as bright white, which indicates that it has a high water content and may be oedematous in nature. The corresponding moderate signal on T1 weighted scans shows that it is not a solitary bone cyst. It must either contain a high protein or high cellular content. The appearances are not typical of blood and were considered likely to be owing to infection, which, based on the history, was chronic. The diagnosis of infected periapical cyst was confirmed by drainage of pus and bloodstained exudate via the root canals of the lower central incisors, and was successfully followed by root filling of these teeth.
