不同数字印模方式影响全瓷冠边缘适合性的研究

目的 研究硅橡胶印模扫描、直接光学印模和传统的物理印模对计算机义齿辅助设计与制作全瓷冠边缘适合性的影响。方法 用数控车床制备聚甲基丙烯酸甲酯材质下颌第一磨牙标准全冠预备体16个，采用硅橡胶制取精细印模，超硬石膏灌注翻制成石膏模型。分别采用扫描全冠预备体、硅橡胶印模和石膏模型获取数字化模型，制作48个氧化锆全瓷冠。采用间隙印模测量法评价3组冠的边缘间隙，应用SPSS 17.0软件对实验数据进行统计分析。结果 直接扫描组、硅橡胶印模组、超硬石膏组的全瓷冠边缘间隙测量结果分别为（69.18±9.47）、（81.04±10.88）、（84.42±9.96） μm。直接扫描组与硅橡胶印模组、超硬石膏组差异有统计学意义（P<0.05），硅橡胶印模组与超硬石膏组之间差异无统计学意义（P>0.05）。结论 直接扫描、硅橡胶印模扫描、石膏模型扫描法全瓷冠的边缘适合性均在临床可接受范围之内，硅橡胶印模扫描可作为临床上获取数字模型的方式之一。

Study on the effect of different impression methods on the marginal fit of all-ceramic crowns

Objective To investigate the effect of three different impression methods on the marginal fit of all-ceramic crowns. The three methods include scanning silicone rubber impression, cast models, and direct optical impression. Methods The polymethyl methacrylate (PMMA) material of a mandibular first molar in standard model was prepared with 16 models duplicated. The all-ceramic crowns were prepared using three different impression methods. Accurate impressions were made using silicone rubber, and the cast models were obtained. The PMMA models, silicone rubber impressions, and cast models were scanned, and digital models of three groups were obtained to produce 48 zirconia all-ceramic crowns with computer aided design/computer aided manufacture. The marginal fit of these groups was measured by silicone rubber gap impression. Statistical analysis was performed with SPSS 17.0 software. Results The marginal fit of direct optical impression groups, silicone rubber impression groups, cast model groups was (69.18±9.47), (81.04±10.88), (84.42±9.96) μm. A significant difference was observed in the marginal fit of the direct optical impression groups and the other groups (P<0.05). No statistically significant difference was observed in the marginal fit of the silicone rubber impression groups and the cast model groups (P>0.05). Conclusion All marginal measurement sites are clinically acceptable by the three different impression scanning methods. The silicone rubber impression scanning method can be used for all-ceramic restorations.