Cluster analysis application to Class I malocclusion

The purpose of this study was to obtain Class I malocclusion statistical subtypes by applying cluster analysis techniques, to assess clinical and cephalometric characteristics from different clusters, and to analyse sex and age effects on grouping patterns. Four-hundred-and-sixteen Spanish patients (243 females, 173 males) with Class I osseous and dental malocclusion (4 degrees > ANB > 0 degrees) between 8 and 16 years of age, with no previous orthodontic treatment, were analysed. Cluster analysis was applied to the information provided by 20 variables both clinical and cephalometric (Ricketts' analysis) per patient. The grouped individuals were defined in a statistically significant manner by a greater lower incisive proclination, greater lower labial protrusion, less dental crowding, and less pogonion-NB distance. So, only the protrusive traits were statistically expressed in the cluster analysis. The grouping pattern in Class I malocclusion was shown in a more defined form at younger age levels and disappeared with age. The clustering pattern was very similar in Class I malocclusion males and females.