BACKGROUND Oral health and general health are very closely related and are considered to be important health problems among individuals due to their expenses associated with treatment, prevalence rate and impact level among individuals and adolescents. These investigations can even have key suggestions for general and oral health prevention strategies relevant to the present knowledge on risk factors for these conditions. Assessment of the current impacts of oral health conditions on quality of life might even develop an understanding of the importance of dental conditions. The general purpose of the current thesis was to investigate the association between oral health and its impact on oral health-related quality of life (OHRQoL) among Brazilian adolescents. METHODS A population-based birth cohort study was carried out in the urban city of Pelotas, Brazil, in the year 2004 (2004 PBCS), including all live births in the city. All mothers living in the urban area of Pelotas and their children born in maternity hospitals of the city of Pelotas (N = 4231) were eligible to participate in this study. RESULTS Findings presented in this thesis indicate that a negative association between oral conditions and OHRQoL exists. Adolescents with severe malocclusion identified with a DAI score greater than 36, showed a negative impact on OHRQoL. Individuals with the presence of dental plaque were seen suffering from severe malocclusion, which in turn was negatively associated with OHRQoL. The evidence provided by the current thesis may not only contribute primarily to the scientific literature but may also furnish researchers and epidemiologists with information vital for orthodontic treatment and be useful to identify community needs and help in the implementation of treatment plans. CONCLUSIONS In conclusion, the impact of malocclusion on daily events among adolescents of Brazil was a common finding in our study. Some other important variables like gingival status, schooling of the fathers that possibly act during childhood which might be affecting the QoL were not included in our present study. These findings may not only contribute to the literature but may also furnish researchers and epidemiologists with information vital for orthodontic treatment and use to identify the community needs and help in the implementation of the treatment plan. Further studies need to be developed to clarify the most complex relationship between impacts of malocclusion on QoL. KEY WORDS Malocclusion, Epidemiological, Brazilian Adolescents, Oral Health-Related Quality Of Life, Dental Aesthetic Index