A new 3-dimensional method for the construction of an average dental arch

Background: This study tested the validity of, and describes, a novel method of constructing an average morphology of the dental arch. Methods: Upper dental arches of adult patients with a sound full permanent dentition were selected for the study. Laser-scanned images of the dental casts were obtained with an optical laser scanning device. The scanned images were analyzed using 3-dimensional graphic visualization and quantification software. Seventy-nine landmarks were identified on each dental arch on the basis of a protocol previously validated for dental analysis. An average dental arch (ADA) shell was then created and analyzed. Linear measures (crown height and mesiodistal width, intermolar and intercanine distances) and angular measures (inclination of the tooth on a reference plane), derived from the created ADA, were compared with the traditional average of measures, derived from single models, using 1-sample Student's t test (P< 0.05). After validation, the ADA was used as a template for comparison with other dental arches presenting some form of malocclusion. Results: A total of 24 upper dental arches of adult patients with a sound full permanent dentition (mean [SD] age 28.8 [5.6] years) were selected for the study. The differences between the upper ADA and the average of single models were small (<0.1mm/1.0°) and nonsignificant, except for canine angulation. The linear measurements were highly precise. The angular measurements exhibited a higher, but acceptable, degree of precision. Conclusion: The construction of the ADA is reliable and may serve as a method for measuring changes in groups of patients.