Detection of a movable object when 3D scanning a rigid object

A method for detecting movable objects recorded in subscans when scanning a set of teeth by means of an intraoral scanner for generating a virtual 3D model of the set of teeth, where the virtual 3D model is made up of a plurality of subscans of a surface of the set of teeth, and where new subscans are adapted to be added to the 3D virtual model when they are acquired, wherein the method comprises:

• acquiring at least a first subscan of at least a first portion of the surface of the set of teeth, wherein a provisional virtual 3D model is initially defined by the at least first subscan;
• determining a provisional excluded scan volume associated with the provisional virtual 3D model;
• acquiring at least a second subscan of at least a second portion of the surface of the set of teeth, and defining the virtual 3D model based on the provisional virtual 3D model and any subsequent subscans including the second subscan;
• determining an excluded scan volume associated with each of the subsequent subscans including the second subscan where no surface can be present in at least two of the subsequent scans;
• determining an excluded scan volume of the virtual 3D model based on the provisional excluded scan volume and the excluded scan volumes associated with each of the subsequent subscans;
• determining whether a surface of a movable object is present in the excluded scan volume of the virtual 3D model;
• and
• if the surface of the movable object is present in the excluded scan volume of the virtual 3D model, then disregard the surface of the movable object in the creation of the virtual 3D model of the set of teeth.