COMPUTER-ASSISTED RECONSTRUCTION OF ENAMEL FISSURES AND CARIOUS LESIONS OF HUMAN PREMOLARS

The origin of cariogenesis in occlusal fissures remains elusive becaus e of limited information about both the fissure structure and the morp hologic details of carious lesions occurring there. The present study was aimed at reconstructing the coronal structure of human premolars w ith the aid of computer-assisted image analysis and, on the basis of t he reconstructed structures, investigating the configuration of fissur es, their proximity to the enamel-dentin junction (EDJ), and the occur rence and extension of carious lesions around the fissure walls. The c oronal portions of the teeth were embedded in polyester resin and then ground off stepwise by hand. Serial images of the enamel contour on s uccessive ground planes were recorded by objective microscopy after it was distinctly demarcated with either 0.5 w/v% carbol fuchsin or 1 w/ v% basic fuchsin. Usually, from 150 to 250 photoprints were collected from a single enamel crown to reproduce the details of the fissure str uctures. The enamel outline (the occlusal and lateral surfaces, fissur e walls, and EDJ) and, if present, the outline of caries-attacked area s were traced accurately on those photoprints by means of a digitizing system. The enamel contour data in series were input into an image an alyzing system (Nikon COSMOZONE, 2SA). Observation of the computer-dra wn coronal enamel allowed us to view the morphologic features of the f issures (shape, divarication, and proximity to EDJ) and to scrutinize the pathway of enamel caries along fissure walls. The results indicate that the computer-assisted reconstruction of enamel crown, in conjunc tion with the step-by-step grinding technique, is useful in basic and clinical studies of occlusal fissure caries.