# Surface Morphology of Three-Dimensionally Printed Replicas of Upper Dental Arches
## 4 Discussion and Conclusions  
Three-dimensional scanning methods associated with computational methods and modern printing technologies have many applications in atomatology and in the clinical practice now. These methods enable the examination of results of complex dental operations and corrections of dental arches as well. Associated problems are related to the accuracy of sensor systems, materials used for three-dimensional printers and the surface analysis of resulting physical models. From practical point of view, it is known that conventional impression materials provide highly accurate impressions based on highly precise plaster casts. Disadvantages of these traditional methods are the possible loss of quality due to, e.g., abrasion, attrition and transport and storage problems. On the other hand, the digital impression process using intraoral [6, 15, 20] scan can be resulted in loss of information. The printing is more precise, prepare long term stable material, but the time of printing is longer. Our approach to the study used profilometer to determine surface structure of the models and electron microscope to find the inner structure. Similar approach was recently chosen by [PERSON] at al. to analyze surface of custom/made titanium meshes used in maxilla/facial surgery [21]. This way seems to be an alternative to micro CT scans with its pros and cons. As disadvantage we can find the necessity to destroy the examined object to characterize the inner structure. It is well known, that profilometers are great for surface analysis of 2D object, but may result in some errors in curvy objects [22]. Micro CT scans can provide information about inner and outer structure from one scan, was confirmed as useful tool in reconstruction of fine anatomic structures as for example middle ear [23], but as disadvantage we see that the method is based on X-ray, which means may have limited use in in vivo studies, other limitation can be also small sample size, high cost and need of specialists in the field to obtain reliable scans. [PERSON] et al. [24] published recently research comparing different methods (CT scans with standard and high resolution, optical 3D scans, micro-CT scans) of 3D data acquisition for tooth replication. Methods were examined on a dry human mandible and showed differences in quality of obtained 3D models, which may also affect 3D printing, if we use these data as source for printing. In that study authors found optical scanning better for more detailed replica than other methods mentioned. Some studies compared various types of 3D printing with different results--surgical templates printed by the light-cured method were statistically less incongruent than those made by an FDM printer in a study by [PERSON] et al. in 2015 [25]. The accuracy of models obtained by intraoral scanning is very high and shows a high level of precision even in more complicated procedures such as dental implantology and prosthodontics [26]. A study by [PERSON] et al. from 2020 showed lower accuracy of fixed dental prostheses fabricated on a 3D printed model than on a conventional cast, but still sufficient for clinical practice [27]. Although many studies have been devoted to the accuracy of models in various clinical applications, with various results, it is not only the metric quality and stability that are important attributes of the 3D printed model: in prosthodontics, esthetic dentistry and orthodontics, the surface of the model is equally important. This also gives information about individual characteristics such as the presence and shape of mamelons, individual curves and the shape of teeth and incisal edge as well as cusps. Specific studies are devoted to profilometer-based approach [28] and advanced micro computed tomography [29], owing to the fact that hard X-ray allow for the isotropic spatial resolution in three-dimensional space. These methods can improve possibilities of the assessment of implants and surrounding bones, to determine mineral concentration in the teeth and to estimate the thickness of enamel.