Influence of spatial resolution and bit depth on detection of small caries lesions with digital receptors

The aim of this study was to compare the caries diagnostic accuracy among intraoral digital receptor systems that provide images in more than one resolution and bit depth.

Eighty noncavitated extracted human teeth were radiographed and analyzed by the following digital systems: Digora Optime (Soredex) 8-bit high- and 8-bit super-resolution, VistaScan (Dürr) 8-bit high- and 8-bit max-resolution and 16-bit high- and 16-bit max-resolution, Dixi2 (Planmeca) 8-bit and 12-bit depths. Insight Film was included as a reference. Six observers scored caries lesions in each tooth surface. The teeth were sectioned and microscopy served as validation. Two-way analysis of variance tested differences in sensitivity, specificity, positive and negative predictive values, and overall accuracy (true positives + true negatives) between the modalities.

There were 160 approximal surfaces examined, and histology showed 63% sound, 31% enamel, and 6% dentinal lesions. Sensitivity was not significantly different within each brand except for VistaScan 8-bit max-resolution, which showed higher sensitivity than the 2 VistaScan high-resolution modalities (P = .003). Digora super-resolution showed higher sensitivity than almost all the other modalities (P < .02), but had lower specificity than all other systems, among which there were no differences. Overall accuracy was significantly lower for Digora high-resolution than for Dixi2 and VistaScan max-resolution modalities (P < .03); there were no differences among the other modalities.

Caries diagnostic accuracy seems to be little influenced by an increase in spatial resolution and bit depth from 8-bit to 12- or 16-bit within digital radiographic system brands. Between systems, the Digora super-resolution images provided higher sensitivity, but lower specificity than most of the other receptors.