Objective:To address the critical issue of missing dynamic border molding information in edentulous direct digital impression technology, this study explores innovative digital solutions and conducts preliminary application validation.Methods:Based on the myostatic line theory, a methodology was established: intraoral scanner (IOS) high-frequency video was utilized to dynamically capture functional molding data of soft tissues, integrated with a self-developed mobility gradient recognition algorithm to achieve dynamic threshold segmentation between the muscle dynamic zone and myostatic zone, termed "optical digital molding technology". Ten edentulous patients with well-fitting complete dentures, treated at the Department of Prosthodontics, Peking University School and Hospital of Stomatology from January 2024 to December 2024, were enrolled. The standard deviation between the muscle static line (generated by mobility gradient algorithm with thresholds of 0.3-0.7 mm) and the denture border curve was analyzed to optimize the dynamic threshold, followed by single-case clinical validation.Results:Among the mobility thresholds of 0.3-0.7 mm, the 0.5 mm threshold yielded the smallest standard deviation between the myostatic line and denture border. Clinical validation demonstrated that dentures designed with this threshold exhibited no displacement during dynamic functional tests, with marginal sealing meeting clinical standards.Conclusions:The optical digital border molding technique for edentulous soft tissue boundaries translates the myostatic line theory into quantifiable parameters for the first time. Based on data from 10 cases, a mobility threshold of 0.5 mm is recommended for clinical application.

Objective:To address the critical issue of missing dynamic border molding information in edentulous direct digital impression technology, this study explores innovative digital solutions and conducts preliminary application validation.Methods:Based on the myostatic line theory, a methodology was established: intraoral scanner (IOS) high-frequency video was utilized to dynamically capture functional molding data of soft tissues, integrated with a self-developed mobility gradient recognition algorithm to achieve dynamic threshold segmentation between the muscle dynamic zone and myostatic zone, termed "optical digital molding technology". Ten edentulous patients with well-fitting complete dentures, treated at the Department of Prosthodontics, Peking University School and Hospital of Stomatology from January 2024 to December 2024, were enrolled. The standard deviation between the muscle static line (generated by mobility gradient algorithm with thresholds of 0.3-0.7 mm) and the denture border curve was analyzed to optimize the dynamic threshold, followed by single-case clinical validation.Results:Among the mobility thresholds of 0.3-0.7 mm, the 0.5 mm threshold yielded the smallest standard deviation between the myostatic line and denture border. Clinical validation demonstrated that dentures designed with this threshold exhibited no displacement during dynamic functional tests, with marginal sealing meeting clinical standards.Conclusions:The optical digital border molding technique for edentulous soft tissue boundaries translates the myostatic line theory into quantifiable parameters for the first time. Based on data from 10 cases, a mobility threshold of 0.5 mm is recommended for clinical application.

Objective:To quantitatively evaluate the accuracy of data obtained from liquid-interference surfaces using an intraoral 3D scanner(IOS)integrated with a compressed airflow system,so as to pro-vide clinical proof of accuracy for the application of the compressed airflow system-based scanning head in improving data quality on liquid-interference surfaces.Methods:The study selected a standard model as the scanning object,adhering to the"YY/T 1818-2022 Dental Science Intraoral Digital Impression Scanner"guidelines,a standard that defined parameters for intraoral scanning.To establish a baseline for accuracy,the ATOS Q 12M scanner,known for its high precision,was used to generate true reference values.These true values served as the benchmark for evaluating the IOS performance.Building on the design of an existing scanner,a new scanning head was developed to integrate with a compressed airflow system.This new design aimed to help the IOS capture high-precision data on sur-faces where liquid-interference,such as saliva,might otherwise degrade scanning accuracy.The tradi-tional scanning method,without airflow assistance,was employed as a control group for comparison.The study included five groups in total,one control group and four experimental groups,to investigate the effects of scanning lens obstruction,airflow presence,liquid media,and the use of the new scan-ning head on scanning process and accuracy.Each group underwent 15 scans,generating ample data for a robust statistical comparison.By evaluating trueness and precision in each group,the study as-sessed the impact of the compressed airflow system on the accuracy of IOS data collected from liquid-interference surfaces.Additionally,we selected Elite and Primescan scanners as references for numeri-cal accuracy values.Results:The scanning accuracy on liquid-interference surfaces was significantly reduced in terms of both trueness and precision[Trueness:18.5(6.5)vs.38.0(6.7),P＜0.05;Preci-sion:19.1(8.5)vs.31.7(15.0),P＜0.05].The use of the new scanning head assisted by the com-pressed airflow system significantly improved the scanning accuracy[Trueness:22.3(7.6)vs.38.0(6.7),P＜0.05;Precision:25.8(9.6)vs.31.7(15.0),P＜0.05].Conclusion:The scanning head based on the compressed airflow system can assist in improving the accuracy of data obtained from liquid-inter-ference surfaces by the IOS.

In fixed prosthodontics, clear exposure of the preparation margin is the prerequisite for obtaining accurate digital impressions and improving the marginal fit of restorations. To resolve the issues associated with the cord retraction technique, such as pain, acute injury, and prolonged procedural time, this study proposes a new technology for intraoral digital impression taking with pneumatic gingival retraction. The new scanning head blows a high-speed airflow that instantaneously separates the free gingiva, locally exposing the subgingival preparation margin. Combined with the farthest point preservation stitching algorithm based on the distance from the normal vector and high-speed laser scanning photography, it achieves global preparation edge data and gingival reconstruction, realizing painless, non-invasive, and efficient precise acquisition of the preparation margin. Using this new technique, a patient with a full porcelain crown restoration on a posterior tooth was treated. The digital impression revealed a clear margin of the preparation, and the crown made from this data has a good marginal fit.

During the complete denture restoration process, accurate impression making is a crucial step for achieving good denture retention. With the increasing popularity of intraoral scanning technology in fixed restoration, the use of intraoral scanning technology in complete denture restoration for edentulous jaw has also been developed. This article systematically reviews the research progress and application of intraoral scanning of edentulous soft tissue, focusing on difficulties in intraoral scanning of edentulous jaws, scanning accuracy, clinical application effects, as well as precautions involved. The aim is to provide references for clinical application.