A graphical user interface for computer-assisted margin marking on dentition, the interface comprising: a video control that is configured to receive a user selection of one of a plurality of video images as a working image, wherein the plural of video images are captured from a camera or camera system suitable for capturing images from which a three-dimensional point cloud may be recovered or from a separate video camera and/or channel; a working area that displays the working image and is adapted to receive a user manipulation of one or more points that mark a margin on the dentition; tools for manipulating the one or more points; and a three-dimensional view that displays a three-dimensional perspective rendering of a digital model of the dentition based on the three-dimensional image capture system, characterized in that the three-dimensional view is adapted to receive a user manipulation of the one or more points and, in response thereto, to update the one or more points that mark the margin on the dentition in the working area; and wherein the three-dimensional view is adapted to display one or more corresponding three-dimensional points corresponding to each user manipulation of the one or more points in the working area; wherein the three-dimensional view is adapted to render the digital model of the dentition from a same perspective as the selected video image when a user selects a video image for display in the working area; and wherein the working area is adapted to be updated to provide a video image more closely corresponding to the user-selected perspective in the three-dimensional view when a user selects a perspective in the three-dimensional view. a video control that is configured to receive a user selection of one of a plurality of video images as a working image, wherein the plural of video images are captured from a camera or camera system suitable for capturing images from which a three-dimensional point cloud may be recovered or from a separate video camera and/or channel; a working area that displays the working image and is adapted to receive a user manipulation of one or more points that mark a margin on the dentition; tools for manipulating the one or more points; and a three-dimensional view that displays a three-dimensional perspective rendering of a digital model of the dentition based on the three-dimensional image capture system, characterized in that the three-dimensional view is adapted to receive a user manipulation of the one or more points and, in response thereto, to update the one or more points that mark the margin on the dentition in the working area; and wherein the three-dimensional view is adapted to display one or more corresponding three-dimensional points corresponding to each user manipulation of the one or more points in the working area; wherein the three-dimensional view is adapted to render the digital model of the dentition from a same perspective as the selected video image when a user selects a video image for display in the working area; and wherein the working area is adapted to be updated to provide a video image more closely corresponding to the user-selected perspective in the three-dimensional view when a user selects a perspective in the three-dimensional view.