System that is configured to be operated in a context of a dental care procedure to be performed in the mouth of a user for a total operation time, the dental care procedure including dental care actions to be performed at respective areas in the user's mouth by means of a functional unit, and the system comprising: an appliance that is configured to operate such a functional unit, a data providing arrangement that is configured to include operation data in the form of respective combinations of an area in the user's mouth and an effective time duration of a dental care action to be performed at the area concerned, wherein the effective time durations of the respective combinations add up to the total operation time and have respective values according to a proportional division of the total operation time on the basis of a distribution of the extent to which dental care is needed at the areas of the respective combinations, wherein at least two effective time durations are different from one another, and a controller that is configured to communicate with the data providing arrangement and to control operation of the appliance in accordance with the operation data wherein the controller is configured to execute an algorithm for adjusting the operation data in the data providing arrangement on the basis of input in respect of at least one area in the user's mouth, which algorithm comprises the steps of: adjusting the extent to which dental care is needed in respect of the at least one areas to which the input applies, determining a new distribution of the extent to which dental care is needed at the areas of the respective combinations, and making a new proportional division of the total operation time on the basis of the new distribution of the extent to which dental care is needed at the areas of the respective combinations. an appliance that is configured to operate such a functional unit, a data providing arrangement that is configured to include operation data in the form of respective combinations of an area in the user's mouth and an effective time duration of a dental care action to be performed at the area concerned, wherein the effective time durations of the respective combinations add up to the total operation time and have respective values according to a proportional division of the total operation time on the basis of a distribution of the extent to which dental care is needed at the areas of the respective combinations, wherein at least two effective time durations are different from one another, and a controller that is configured to communicate with the data providing arrangement and to control operation of the appliance in accordance with the operation data wherein the controller is configured to execute an algorithm for adjusting the operation data in the data providing arrangement on the basis of input in respect of at least one area in the user's mouth, which algorithm comprises the steps of: adjusting the extent to which dental care is needed in respect of the at least one areas to which the input applies, determining a new distribution of the extent to which dental care is needed at the areas of the respective combinations, and making a new proportional division of the total operation time on the basis of the new distribution of the extent to which dental care is needed at the areas of the respective combinations. adjusting the extent to which dental care is needed in respect of the at least one areas to which the input applies, determining a new distribution of the extent to which dental care is needed at the areas of the respective combinations, and making a new proportional division of the total operation time on the basis of the new distribution of the extent to which dental care is needed at the areas of the respective combinations.