A method of providing an accurate three-dimensional scan of a dental arch area is disclosed. The arch area has two segments and a connecting area between the two segments. The connecting area has homogeneous features. A connecting-geometry tool with at least one definable feature is affixed to the arch area. The definable feature overlays at least part of the connecting area. The arch area is scanned to produce a scanned dataset of the arch area. The definable feature of the connecting-geometry tool on the connection area is determined based on the scanned dataset. The dimensions of the arch area are determined based on the data relating to the definable features from the scanned dataset.