| As for dentists, to reproduce accurately the color of natural teeth was an important aspect of obtaining aesthetic restorations. But nowadays in clinic, traditional visual colorimetry and color matching methods were somewhat subjective, with low precision, and difficult to repeat. The results were that the color matching rates of anterior teeth restorated by poecelain-fused-to-metal were not suitable for attaining natural aesthetics. So it is important for dentists to improve the color matching rates of restorations. Using CR-32 1 portable colorimeter and chromatic software CHROMA, we studied the color matching rate of porcelain-fused-to-metal restorations through traditional visual colorimetry, and compared it with computer-aided instrumental colorimetry. CIE~l976~L*a*b*system was used here. Results are as follows: 1. Chromatic software CHROMA has a friendly interface and need no high- quanlity hardware. It can acquire acurate and objective results, so suitable for clinic usage. 2. When doctors and patients look for similar chips to patients?natural teeth from shade guide, the accuracy is as low as 48.0%. 30.0% chips with similar hue but different value are selected. The chips with similar value but different hue add upto 18.7%. Among the porcelain-fused-metal restorations fabricated by technicians according to the chips selected by visual colorimetry, 70.8% restorations have similar color with the chips. 26.4% restorations have similar hue but different value. -3- Then the color matching rate of porcelain-fused-metal restorations through traditional visual colorimetry is 34%. 3. The color matching rate of porcelain-fused-metal restorations through computer-aided instrumental colorimetry is 60%, and obviously superior to that of visual colorimetry.Color difference between chips and resorations selected and fabricated through computer-aided instrumental colorimetry is 2.58NBS, much smaller than that of visual colorimetry.
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