## 1 Introduction  
Producing digital impressions with dental scanners has become common practice in the field of fixed prosthodontics. The digital impression does not employ impression materials or need to be poured, disinfected, and shipped to the dental laboratory. As a consequence, this eliminates the associated problems, leading to a possible improvement in the quality of impressions [1,2]. It has been concluded that digital impression techniques are clinically acceptable for the fabrication of crowns and short-span FPD, but the conventional impression technique is still recommended for full arch FPD [3].  
A previous in vitro study evaluated the accuracy of four conventional impression materials with four digital impression systems, and reported greater local deviations with digital impression systems [4]. An in vivo study by [PERSON] et al. attempted to assess the realistic application and precision of digital scanners. The lowest precision was reported for iTero full-arch intraoral scans, followed by extra-oral model scanning with iTero scans whereas stone model scanning with extra-oral scanner D250 3 Shape showed the highest precision [5].  
Studies conducted by [PERSON] and [PERSON] [6], and [PERSON] et al. [7] reported a higher precision of conventional impressions when compared to the digital ones, whereas comparable precision was also reported for quadrant impressions made using digital and conventional techniques, but a significant difference in precision was reported between various digital scanners used in the study [8]. Moreover, a previous in vitro study reported comparable accuracy of full-arch digital impressions when compared to conventional impressions [9].  
In their in vivo study on full arch impressions, [PERSON] et al. reported higher precision with conventional impressions materials compared to the eight digital intraoral scanners used in their study. They reported that full dental arches could be successfully recorded by all eight intraoral scanners [10]. A similar clinical study by [PERSON] et al. also supported the use of intraoral digital scanners for generating maxillary full-arch impressions with acceptable accuracy [11].  
The amount of distortion in the stone cast produced by conventional impression differs according to the clinical case and the location of the prepared abutment teeth (i.e., short span in one quadrant, long span crossing the midline, or in some cases full mouth). Despite the different concepts between the conventional and digital impression methods, they are used for reproducing oral hard and soft tissues. This current study was conducted to evaluate the accuracy of master cast generated by conventional (putty and light body consistencies polyvinyl siloxane (PVS) and alginate (ALG)) and digital impression techniques on a typodont master model with full-arch-prepared abutment teeth. This study examined the following two null hypotheses: (1) no statistically significant differences in accuracy between casts made by the two impression modalities and the typodont master model at each of the four locations (horizontal straight (HS), horizontal curved (HC), horizontal cross arch (HCA), and vertical (V)), and (2) no statistically significant differences in dimensions measured at each of the four locations between the casts generated using the conventional and digital impression techniques.