There is no legal regulation for visiting the dentist or doctor during working hours. Whether agreements have been made about this can often be found in your collective labor agreement, employment contract or internal company regulations. The reason for this is that many employees cannot see a doctor, dentist or physiotherapist on weekends or evenings. If there is nothing in your collective labor agreement or company regulations, you can discuss with your employer whether you will continue to be paid during absence.
In practice, this often means that you make such arrangements in your free time and when that is not possible, that you usually do not have to take leave hours.