There are few longitudinal studies of the prevalence of malocclusionsand possible self-correction of malocclusions during the developmentof the dentition. Early intervention might be unnecessary if self-correction of the malocclusion occurs during the transition from theprimary to the permanent dentition. Most studies are cross-sectionaland in those of longitudinal design, the results are inconsistent anddifficult to interpret.Malocclusions may or may not influence the quality of life inchildren and adolescents. Thus, evaluations of the influence ofdifferent malocclusions on quality of life will certainly underpin abroader understanding and knowledge about how malocclusionsaffect the daily life of young patients. This information may also beimportant when it comes to assessing the most appropriate time forstarting orthodontic treatment, not only from a professional pointof view, but also, most importantly, from the patients’ perspective.The overall aim of this thesis was therefore to evaluate theprevalence of malocclusions, and to document changes occurringduring the development of the dentition, from the primary dentitionstage at age 3, through the mixed dentition at age 7, to the earlypermanent dentition at age 11.5 years. Further aims were to reviewthe current state of knowledge about the impact of malocclusionson oral health related quality of life (OHRQoL) and to investigatehow malocclusions affect the quality of life in a cohort of children,aged 11.5 years, whose dental care is provided by the Swedish PublicDental Service.