###### Abstract  
Traditionally, soft tissue records are obtained by dental impression using impression materials; however, accurately recording the soft tissue immediately after tooth extraction is difficult. We measured the tissue changes after tooth extraction and compared two impression modalities (digital versus conventional) by measuring the changes at the soft tissue level. In this case, 15 patients with 17 single extraction sites were enrolled. Conventional impression (CI) using vinyl polysiloxane material and digital impression (DI) using an intraoral scanner were prepared immediately after extraction (T0) and at 2 months post-extraction (T1). Standard tessellation language files were generated for superimposition of the tissue surface. The tissue changes and discrepancies were measured on the superimposed surfaces. The differences in the changes and the discrepancy between the tissue surface impression at each time point were compared. At all measuring levels, the total tissue change was significantly different between groups DI and CI (_p_ < 0.05). DI exhibited a more pronounced tissue surface at both time points, and the total discrepancy was statistically significantly greater at T0 than at T1 (_p_ < 0.05). The values from DI and CI demonstrated small but significantly different for the same study material. The interpretation of such differences may depend on the clinical situation or scientific value. alveolar bone loss; digital technology; dental impression material; gingiva; tooth  
precise matching between stone models prepared at different time points may be difficult to obtain because it is the human eyes that inevitably determine the matching. Scanning of the stone model using a model scanner was later introduced. Three-dimensional (3D) digital images formatted as standard tessellation language (STL) files are generated using this method [4]. Intraoral scanners have enabled impression material/stone model-free processes [5]. Superimposing STL images from different time points can help analyze the differences in the tissue surfaces [3; 6; 7]. Regarding superimposition, best-fit alignment using an iterative closest point algorithm was applied to search for the best matching location between datasets. However, this method often causes errors in minimizing the absolute distance between datasets regardless of the clinical outcome. To overcome this limitation, we attempted to align surface areas that underwent changes below a predefined threshold on the entire surface [8; 9]. The abovementioned methodological improvement might prevent errors, including those resulting from improper impression/stone material preparation, an inaccurate technique of impression-taking/stone model fabrication, and dimensional changes in the materials, prior to the scanning process [10]. Intraoral scanning technologies have proven accuracy in generating meaningful and novel data [11]. However, specific impression materials, such as vinyl polysiloxane, are highly accurate compared with other materials [12] and have been used to evaluate the accuracy of intraoral scanners [13]. Furthermore, digital impressions using intraoral scanners exhibit deviations according to the scanning device type, scanning range, and intraoral environmental conditions, such as bleeding or mobile tissues [11; 14; 15; 16]. Therefore, there is a need to compare tissue surface changes according to the impression methods (digital or conventional). Impression material/stone model-free processes using an intraoral scanner and the subsequent production of STL files have become popular for analyzing and comparing tissue changes at the soft-tissue level [14; 15]. Extensive data on tissue changes have already been obtained from conventional methods using impression materials and stone models. However, even in recent studies, conventional methods were used because of the unavailability of intraoral scanners and maintenance of the same technique employed at study initiation.