Introduction: Orthodontists treat child and teenager malocclusion, but has expanded to include adults in recent decades due to raised awareness of the importance of oral health. Mainly adult patients choose to treat malocclusions using aligners. Different tooth movements, orthodontic appliances and technologies for the production of orthodontic appliances are used to eliminate malocclusion. Purpose: In the diploma thesis, we aim to describe individual tooth movements to achieve ideal occlusion and elimination of malocclusions, such as open, deep and cross bite, crowding, closing gaps, and class II and III malocclusions using aligners. We also want to introduce two forming techniques of aligners. The first one is the forming technique of a plaster set-up, which started the development of aligners, and the second is the modern forming technique of digital set-up. For the comparison of both set-ups, we then applied computer overlay technology. The purpose of the diploma thesis is to determine the efficacy of the treatment and to achieve the ideal occlusion by using aligners and confirm or disprove the hypothesis. Hypothesis: Differences exist between manual and digital simulations of tooth movements. Methods: We applied two methods. The dominating one is a descriptive method of collecting and reviewing the literature. The primary source were English-language professional books, scientific articles and electronic books, which have been made available through the Central Medical Library, web browsers and online professional databases, such as Google Scholar, Cobiss, ScienceDirect, PubMed, etc. The second method is a description and creation of an older and modern way of simulating tooth movements and designing an aligner. We began the modern digital set-up by designing treatment in the computer-aided program and continued by producing an SLA model. In the older method, we started making a plaster set-up manually. We also applied a computer overlay method to compare manual plaster and virtual set-ups. Results: For comparison, we made plaster and digital set-up under the same treatment plan. Thus, we extracted the lower-left redundant premolar on the model and, when making the set-up, harmonised the course of the median line and achieved class I occlusion. Since the risk of uncontrolled tooth movement into the gap is high, we additionally designed composite attachments to reduce the risk of uncontrolled tipping. The completed plaster set-up was duplicated and then poured, and a model was created for the digital set-up using the stereolithographic 3D printing process. Then, we scanned the data of the gypsum surface of the manual set-up using a 3D scanner and transferred both virtual models to a computer overlay program. The results indicated a discrepancy between the two. Discussion and conclusion: Achieving ideal occlusion by applying aligners is limited to lighter malocclusions, such as crowding and open bite and closure of smaller diastema. More complex and extensive malocclusions require the additional application of ancillary orthodontic elements and elastics, but this area has not been sufficiently explored. Scientists are working to improve the aligners in the tooth movement and to advance the manufacturing process. Therefore, in part two, we compared the gypsum and digital set-up, which in many ways is more appropriate and has significant advantages over gypsum. With the use of computer overlay technology, we have further confirmed this thesis, since there are deviations between them, which are the result of multiple pouring of plaster and its dimensional change.