Background: Currently, dental impressions are captured using both conventional and digital methods. Numerous studies worldwide have assessed conventional impression techniques in both clinical and in vitro settings. While most studies have evaluated the factors affecting error rates during impression taking, few have examined error rates by impression material type. Proper evaluation of working models and clarification of the causes of impression errors and the factors influencing them form the basis for effective restoration of patients’ oral health. In appliance fabrication, the material properties, technology, and techniques used directly influence the final outcome. Therefore, this study was conducted to examine the causes of impression errors and the related factors that have not been fully investigated in previous studies, including impression-taking technique, impression material type, the size of the area requiring restoration, and other related factors. Aim: To investigate the factors influencing clinical errors in working models used in fixed prosthodontics. Materials and Methods: This cross-sectional observational study was conducted from May 2025 to November 2025 and included 80 working models prepared for fixed prosthesis fabrication. The models were collected from the Central Hospital Laboratory of the MNUMS School of Dentistry, Changed Goods Dental Laboratory, and Suld Dental Laboratory in Ulaanbaatar. After disinfection and drying, the models were analyzed using a Model MD-ID0400 digital 3D scanner to evaluate factors potentially contributing to impression errors. Result: Of the 80 cases included in the study, 67.5% (n=54) were male and 32.5% (n=26) were female, with a mean age of 35.2±3.5 years. Data were collected from working models prepared from impressions submitted by dental clinics for fixed dental restorations and evaluated digitally. All impressions were made using addition silicone impression material. The mean number of working models presenting impression errors among the received cases was 8.00±3.53. Conclusion 1. In the practice of dentistry, the impact of material properties on the quality of the material is not enough to make better impressions of the teeth without additional silicone. The total number of impressions taken was 8.00±3.53. 2. The error rate of the impression taking method was 7.78±3.9 in one stage and 8.03±3.51 in two stages (p<0.843).