Mechanical axiography was performed on 49 (37 female, 12 male) patients prior to orthodontic treatment, after removal of the fixed appliance, and at the end of retention. Twenty-five subjects (mean age 12.8 years) underwent orthodontic treatment without premolar extractions (group 1) and 24 subjects (mean age 13.5 years) with premolar extractions (group 2). The axiographic tracings of the protrusive movements were analysed using a digitizer and specially designed software. A statistically significant increase (P < 0.05) in the values for horizontal condylar inclination (HCI) was found for both groups over the entire observation period. Group 1 showed a higher increase (P < 0.05) between the beginning of treatment and removal of the brackets, and group 2 between bracket removal and the end of retention. At the end of retention, a similar increase in HCI values was found for both groups. Over the observation period, the frequency of pathological axiographic findings decreased, which seems to be a positive effect of orthodontic treatment.

Guidelines have been established for the arrangement of artificial teeth based on the curve of Wilson, the curve of Spee and the occlusal plate rule of Gysi. However, no scientific studies have been carried out to see whether these prosthodontic rules are actually present in natural teeth. This study was carried out on a selected sample of children and adolescents with natural dentitions using a 3D computer-aided measuring device to reevaluate these occlusal rules in order to establish whether occlusion with anterior protected articulation is the occlusal scheme of choice. The previously estblished prosthodontic rules were confirmed to be present in the complete natural dentitions of adolescents at completion of tooth eruption period and support their use as guiding principles in diagnosis and treatment.