Comparison of clinically used shade guide systems with color range of natural teeth / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the limitation of currently used shade guide systems comparing with color range of nature teeth.</p><p><b>METHODS</b>Digital pictures of shade guide systems A (VITAPAN Classic), B (VINTAGE Halo), C (3D-MASTER), and 322 central incisors were taken under the same condition as light source of D65 with the observation method of d/0 degrees. The data obtained from nature tooth color were compared with the color range of three shade guide systems mentioned above in items of L * a * b */C * H degrees.</p><p><b>RESULTS</b>The normal chroma value (95%) of the natural teeth were L* 61.631-73.250, a * -0.719-1.879, and b * 8.701-17.790. Natural tooth colors were different from those of the shade guide system A which color range was narrower, short of red hue, higher values, and unevenly distribution of saturation. On the other hand, the range of red hue increased in shade guide system B while its saturation was slightly high. The color range of shade guide system C was greatest among the three shade guide systems. The saturation and value of shade guide system C covered all varieties of nature teeth measured in this research, but it still lacked red hue comparing to the nature teeth.</p><p><b>CONCLUSIONS</b>Comparing the color range of nature teeth, the shade guide systems used in clinic have uneven hue distribution and cannot cover all colors of nature teeth. Generally, all the shade guide systems are lack of the hues which are named under the category of red tone.</p>

A primary study of color tolerance of anterior tooth crown prosthesis / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the color tolerance of anterior ceramic crown and seek an effective approach for color-matching of oral prostheses.</p><p><b>METHODS</b>30 single maxillary incisor ceramic prostheses and the corresponding nature teeth were measured by a digital camera in a steady environment for image taking and color measurement, which based on the standard recommended by CIE. The color tolerance was analyzed in two groups based on satisfaction and dissatisfaction of prostheses color-matching.</p><p><b>RESULTS</b>The deltaE of satisfaction group was 2.5503, while the deltaE of dissatisfaction group was 4.0772. There was significant difference between chromatic aberration of satisfaction group and dissatisfaction group (P<0.01). When the lightness and saturation of prosthesis were higher than nature teeth, there was no significant difference between deltaL*, deltab*, deltaC* of satisfaction group and dissatisfaction group (P>0.05). When the lightness and saturation of prosthesis were smaller than nature teeth, there was significant difference between deltaL*, deltab*, deltaC* of satisfaction group and dissatisfaction group (P<0.01). There was significant difference between deltaa*, deltaH of satisfaction group and dissatisfaction group (P<0.05, P<0.01).</p><p><b>CONCLUSION</b>Control of color difference is the key for shade matching of anterior tooth prosthesis. Applying the color tolerance is beneficial to improving the prosthesis quality.</p>

Circulating test and analysis of clasp retention / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To show the trend of the retention change during the circulation of the clasp dislodging and inserting, and to discuss the proper depth of the undercut for a specific clasp. It is also a basic study for the best designing of RPD.</p><p><b>METHODS</b>The Chatillon force measuring instrument was used to record the variation of the retention of Co-Cr alloy casting Akers clasp when they were dislodging from undercuts of different depths (0.25 mm, 0.50 mm, 0.75 mm) on bicuspid and molar.</p><p><b>RESULTS</b>The data was analysed of Correlation and Regression by SPSS 10.0 statistic software. The variations of the retention in the circulation are obvious from the different teeth and different undercut depths. It shows an attenuation trend in circulation (P < 0.01). After 400 times dislodging, in bicuspid group, the retention of the clasp used in 0.50 mm undercut became less than the one used in 0.25 mm undercut. While the retention of the clasp used in 0.75 mm decreases most obviously, it values 0.7670 kg. In molar group, the attenuations of the retention at different depths of undercut are similar, the retentions of the clasp still rank as, from great to less, 0.75 mm, 0.50 mm and 0.25 mm, in the depth of undercut.</p><p><b>CONCLUSION</b>the proper depth of the undercut for bicuspid is 0.25 mm, and 0.50 mm for molar.</p>