Objective: To develop a new technique for determining symmetry in tooth morphology and to evaluate this in the investigation of a patient with a solitary maxillary median central incisor (SMMCI) and a control group.
Design: A 9-year-old Caucasian female presented with SMMCI. Clinically the tooth appeared symmetrical. Morphology measurements of the maxillary central incisor were made using an image analysis system. Symmetry was determined by outlining the tooth from labial and axial views. These images were block filled, duplicated, flipped horizontally and then superimposed on the original image. The coincident area and perimeter of the two images from both views were measured. The method was repeated for the maxillary central incisors of 20 sets of control study models for young adult patients from which reference intervals for comparison with the SMMCI case were prepared.
Results: From the labial view, the area and perimeter of the two images of the SMMCI tooth were 98.85% and 98.97% coincident, respectively. From the axial view the area of the two images was 96.17% coincident, while the perimeter was 99.03% coincident. In all but one comparison for coincidence the SMMCI was above the upper limit of the reference range from the control group.
Conclusions: This new technique is a valid method of assessing symmetry and is a useful clinical tool in cases of SMMCI.