Occlusal status and prevalence of occlusal malocclusion traits among 9-year-old schoolchildren.

The aim of this study was to provide detailed information concerning clinically relevant occlusal traits and the prevalence of occlusal anomalies in an orthodontically relevant period of dental development. Four hundred and ninety-four German schoolchildren (237 males and 257 females), median age 9 years, were orthodontically examined. Overjet and overbite were measured to the nearest 0.5 mm, and sagittal molar relationships were registered clinically to the nearest quarter unit. In addition, crossbites, scissor bites, and midline displacements were evaluated. Descriptive statistics was complemented by testing gender differences and differences between groups with Class I and Class II anomalies (Mann-Whitney U-test) as well as a statistical evaluation of differences between the three dental stages (Kruskal-Wallis test). Overjet exhibited an extreme range between -2 and 12 mm (median values 3-3.5 mm). An increased overjet was more prevalent than a reduced or reverse overjet, and a severely increased overjet greater than 6 mm was a common finding affecting around 5-10 per cent of the children. Similarly, overbite showed considerable variations of between -1 and 9 mm (medians 3-3.5 mm) and males exhibited a significantly larger overbite than females. In Class II malocclusion subjects, overbite was significantly enlarged (on average between 0.5 and 1 mm) when compared with those with a Class I malocclusion. Traumatic contact of the gingiva affected every 14th child. A Class II molar relationship of three-quarter units or more was a frequent finding affecting more than one child in five. In addition, at 9 years of age, 3 per cent of the children exhibited a Class III molar relationship of at least a half unit. The wide range of orthodontically relevant occlusal traits found in the present study underlines the need for orthodontic screening at 9 years of age (or earlier).