Computer technologies are ubiquitous and in the recent times, these technologies are penetrating more into the field of medicine, where they play a vital role in modern healthcare. In this master's thesis, we are solving a problem, which dentists typically encounter during teeth alignment treatment. At the end of the treatment, when permanent orthodontic braces are removed, the initial phase of tooth demineralization often appears as white spot lesions on the smooth surfaces of a tooth. We developed a prototype for automatic segmentation of teeth and white spot lesions, which may contribute to a more accurate and objective way of treatment monitoring. In the process of development, we used various image processing techniques and image segmentation algorithms. The developed prototype was evaluated against a database, which we built from the selected images of clinical examinations. The prototype showed promising results with a lot of potential for improvements and future work.