Resorption pattern and radiographic diagnosis of invasive cervical resorption. A correlative microCT, scanning electron and light microscopic evaluation of a case series.

The aim of this study was to evaluate, whether and how the histologic structure of invasive cervical resorption (external granulomas) affect their clinical radiographic diagnosis. For this purpose, nine more or less intact extracted teeth, of which intraoral radiographs were available, were processed for examination in the scanning electron (SEM) and light microscope. From some of the specimens non-decalcified ground sections were prepared and some were decalcified for preparation of histologic sections. Five teeth were scanned in an X-ray microtomography (microCT) device and digitally reconstructed in three dimensions. Three histologic characteristics, namely (1) the location and extension of the resorptive defect, (2) the size of the communication with the periodontium, and (3) the amount of mineralized substitution tissue formed in the lesion affected the radiographic diagnosis. At early and advanced stages, invasive cervical resorption had encircled the pulp cavities, however, without destroying the innermost dentin. Even if the dentinal wall adjacent to the pulp was histologically intact and thick, this important diagnostic feature frequently could not be recognized in conventional radiographs. Also, the communication between the resorptive lesion and the periodontium often was not visible radiographically, although it could always be identified in the microscopic evaluation, particularly at early stages when it proved to be very small. Invasive cervical resorption lesions containing large amounts of mineralized substitution tissue were difficult to recognize and, therefore, could easily be overseen. Thus, three features which are deemed essential for the differential diagnosis of invasive cervical resorption were not readily apparent in conventional radiographs. From these three features, the dentinal wall against the pulp cavity and the communication to the peri-odontium were, however, clearly visible in the microCT reconstructions.