Accuracy of a system for creating 3D computer models of dental arches.

Three-dimensional imaging of dental tissues will have a major impact in dentistry if the images are accurate. The purpose of this study was to measure the accuracy and precision of a system for creating three-dimensional images of dental arches. Using vinyl polysiloxane impression materials and improved dental stone, we made 10 stone casts of a "dental" standard with known dimensions. The impressions and casts were scanned by means of a Comet 100 optical scanner. Custom software created three-dimensional images (computer models) from the scanned data. Accuracy was defined as the average of the absolute differences between the computer models and the standard. Precision was the standard deviation of accuracy over 10 repeated measures. Software processing improved the accuracy of the scanner data. Accuracy +/- precision for the casts and impressions was 0.024 +/- 0.002 mm and 0.013 +/- 0.003 mm, respectively. The system produced computer models with sufficient accuracy for clinical application.

Comparison of woman-specific versus breast-specific data for reporting screening mammography performance.

RATIONALE AND OBJECTIVES: Screening mammography data can be reported on a breast-specific or woman-specific level, and much mammography data available for research is woman-specific. The purpose of this study was to determine if woman-specific screening mammography data are sufficient for research and reporting by measuring and comparing the accuracy of screening mammography on a breast-specific and on a woman-specific level. MATERIALS AND METHODS: Definitions for true-positive and false-positive mammography results were developed to distinguish between breast-specific and woman-specific calculations. The sensitivity, specificity, and positive predictive values of screening mammography were calculated on a breast-specific and on a woman-specific basis for the entire population of the Carolina Mammography Registry and for a randomly selected subset of the population. RESULTS: Only small differences were found in breast-specific versus woman-specific calculations of sensitivity, specificity, and positive predictive values for both the entire population and the smaller subset population. For both populations, woman-specific sensitivity and positive predictive values were slightly higher than the same breast-specific values, and woman-specific specificity was slightly lower. CONCLUSION: For research and reporting, woman-specific data are sufficient.