A digital technique is described for designing and fabricating segmental individual tooth trays that can be used to make an impression of multiple preparations with high accuracy and efficiency. A digital model of prepared dentition was acquired. The segmental individual tooth trays with retention attachments and tissue stops were designed and 3D printed with light-polymerizing resin. The segmental impression of each section of the prepared dentition was made with the corresponding individual tooth tray loaded with the impression material. A final overall impression was made to pick up the segmental individual tooth trays with a full arch tray.

OBJECTIVE: To analyze the clinical performance of the intraoral digital impression (IDI) in the fixed prosthodontics.
METHODS: Databases of Medline (Ovid), EMBASE, Cochrane Central Register of Controlled Trials, and CNKI were searched for randomized controlled trial (RCT) on the use of IDI in fixed prosthodontics until May 2020. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of included studies. A Meta-analysis was conducted when available.
RESULTS: Eleven RCTs involving 618 patients were included in this study. A total of 2 and 3 studies had low and high risks of bias, respectively, and other included studies had a medium risk of bias. Results illustrated that the IDI group could shorten the impression-taken time [SMD=-5.63, 95%CI (-11.25, -0.01), P=0.05] and improve the accuracy of the marginal fit [SMD=-0.53, 95%CI (-0.84, -0.22), P=0.000 7] compared with the conventional impression group. However, no significant difference was observed in the internal fit.
CONCLUSIONS: Evidence indicated a good clinical performance of IDI for fixed prosthodontics. Notably, high-quality studies are expected to further support the conclusion.
目的: 系统评价口内扫描数字化印模（IDI）技术对固定修复的临床应用效果。方法: 计算机检索Medline（Ovid）、EMBASE、Cochrane Central Register of Controlled Trials以及中国知网（CNKI）数据库关于IDI对口腔固定修复治疗临床效果的随机对照试验（RCT），各数据库均检索至2020年4月。2名研究者依照纳入标准分别对文献进行筛选、提取及评价，可合并结果进行Meta分析。结果: 共纳入11篇RCT，涉及618名患者，其中高质量文献2篇，低质量文献3篇，其余均为中质量文献。结果显示，与常规取模方式相比，IDI具有更短的操作时间［SMD=-5.63，95%CI（-11.25，-0.01），P=0.05］，更准确的修复体边缘密合性［SMD=-0.53，95%CI（-0.84，-0.22），P=0.000 7］；但2组间对修复体的适合性差异无统计学意义。结论: 现有证据表明IDI应用于口腔固定修复中可获得较好的临床效果，未来仍需更多高质量研究支持。.

BACKGROUND: This paper introduces a method to digitally design a virtual model of a tooth preparation of the mandibular first molar, by using the commercial three-dimensional (3D) computer-aided design software packages Geomagic and Imageware, and using the model as an input to automatic tooth preparing system.
METHODS: The procedure included acquisition of 3D data from dentate casts and digital modeling of the shape of the tooth preparation components, such as the margin, occlusal surface, and axial surface. The completed model data were stored as stereolithography (STL) files, which were used in a tooth preparation system to help to plan the trajectory. Meanwhile, the required mathematical models in the design process were introduced.
RESULTS: The method was used to make an individualized tooth preparation of the mandibular first molar. The entire process took 15min.
CONCLUSIONS: Using the method presented, a straightforward 3D shape of a full crown can be obtained to meet clinical needs prior to tooth preparation.