Real-time observations of tooth demineralization in 3 dimensions using X-ray microtomography

The immediate aim of this study was to develop and test a method to record, visualize and quantify real-time demineralization (or remineralization) of teeth in vitro using X-ray microtomography (XMT or micro-CT). The longer term objective is to improve understanding of demineralization processes, allowing the creation of better artificial models of dental caries and better quantification of the efficacy of caries treatment and prevention regimes. For demineralization studies, the tooth is mounted in a plastic container through which the demineralizing solution is circulated during simultaneous repeated scanning. Key features of the method are safe circulation of the demineralizing solution, periodic interruption to adjust X-ray filament current and re-focus, accurate beam-hardening correction and calibration, alignment of reconstructed scans, and normalization of grey-levels to compensate for changes in the X-ray spectrum. The method was tested by scanning an extracted third molar during 8 days of demineralization. From the reconstructed 3D images, the progression of an artificial carious lesion could be visualized and quantified. The lesion progressed at approximately 0.1 mm per day and appeared to be more erosive in nature. A successful method has been developed to monitor real-time demineralization in 3 dimensions. Further work is now needed to create better models of true carious lesions. Observation of the dynamics of demineralization and remineralization will aid in the development of therapies to treat and prevent dental caries.