Introduction: Open bite is an irregularity in a vertical plane, in which the upper and lower teeth are not in contact. Although open bite may also occur in the side areas of the tooth arches, this irregularity is most common in the foreground. It may be of dentoalveolar or skeletal origin. In addition to the irregular growth and development of the jaw, the cause of the open bite can also be defective orofacial functions. Particular risk factor for the development of open bite in deciduous teeth are sucking habits. Treatment of open bite can be either surgical or with the help of orthodontic appliances. Functional jaw - orthopedic appliances, used for treating open bite, are the bionator according to the Balters protective type, the function regulator type IV and the vestibular plate. Purpose: The purpose of the diploma work is to present the irregularity of open bite, causes that lead to the development of open bite, different treatment methods, and to present functional jaw orthopedic devices used for treating open bite and their manufacture in the laboratory. The purpose is also to present statistical analysis of open bite and the use of appliances when treating open bite, the TheraMon device and analysis of the initial and final study models with the Rapidform program. Methods: We reviewed foreign and domestic professional literature, articles and journals in the field of dental and jaw orthopedics. We constructed three functional appliances and reviewed data for all the patients that have completed treatment at Orthos clinic by the end of year 2014.Results: We designed three functional jaw - orthopedic appliances for treating open bite, presented the construction of appliances in the lab and documented every step of the process. We inserted the TheraMon device into the appliances in order to measure the time the patient was using the appliance. We constructed initial and final study models, we then digitalized them in a three-dimensional format, and measured the surface and volume with RapidForm. Discussion and conclusion: Functional jaw - orthopedic treatment in the early developmental period was successful in all three patients. The morphological deformity of the open bite system was eliminated in all three patients. We can effectively monitor the wearing time of the appliances with the TheraMon device. With the objective method of 3D analysis of the design characteristics of the jaw, we confirmed that functional jaw - orthopedic devices can influence the growth and development of the jaw. When reviewing the statistics, we found that 19% of children with an average age of 11.2 years had open bite.