The marginal fit of lithium disilicate crowns: Press vs. CAD/CAM

Abstract: This study aimed to compare the vertical marginal gap of teeth restored with lithium disilicate crowns fabricated using CAD/CAM or by pressed ceramic approach. Twenty mandibular third molar teeth were collected after surgical extractions and prepared to receive full veneer crowns. Teeth were optically scanned and lithium disilicate blocks were used to fabricate crowns using CAD/CAM technique. Polyvinyl siloxane impressions of the prepared teeth were made and monolithic pressed lithium disilicate crowns were fabricated. The marginal gap was measured using optical microscope at 200× magnification (Keyence VHX-5000, Japan). Statistical analysis was performed using Wilcoxon test. The lithium disilicate pressed crowns had significantly smaller (p = 0.006) marginal gaps (38 ± 12 μm) than the lithium disilicate CAD/CAM crowns (45 ± 12 μm). This research indicates that lithium disilicate crowns fabricated with the press technique have measurably smaller marginal gaps compared with those fabricated with CAD/CAM technique within in vitro environments. The marginal gaps achieved by the crowns across all groups were within a clinically acceptable range.

摘要：本研究旨在对比采用计算机辅助设计/计算机辅助制造（CAD/CAM）技术与压制成型陶瓷工艺制作的二硅酸锂（lithium disilicate）全冠的垂直边缘间隙。研究收集了20颗经外科拔除的下颌第三磨牙（mandibular third molar），并制备为接受全饰面冠修复的基牙。对预备后的基牙进行光学扫描，采用二硅酸锂瓷块通过CAD/CAM技术制作全冠。同时制取预备牙的聚硅氧烷（polyvinyl siloxane）印模，制作整体压制成型二硅酸锂全冠。使用光学显微镜（放大倍率200×，日本基恩士VHX-5000）测量边缘间隙。采用威尔科克森（Wilcoxon）检验进行统计学分析。结果显示，压制成型二硅酸锂全冠的边缘间隙（38±12 μm）显著小于CAD/CAM制作的二硅酸锂全冠（45±12 μm，p=0.006）。本研究表明，在体外实验环境下，采用压制成型工艺制作的二硅酸锂全冠，其边缘间隙显著小于CAD/CAM技术制作的全冠。所有组别全冠的边缘间隙均处于临床可接受范围内。