The Brazilian version of CPQ8-10 was used in this study to assess the impact of oral conditions on quality of life. This OHRQoL instrument was designed exclusively for this age group. This instrument has been proven valid and reliable for use in Brazilian children . In order to define cases and controls, the CPQ8-10 scores were analyzed using the two-step cluster method. Cases and controls were individually matched by school because a previous study showed that dental caries experience and severity of dental caries in primary and permanent teeth are influenced by the type of school . In Brazil, economically underprivileged children are enrolled public schools, had a higher prevalence of dental caries and the greatest impact thereof on their quality of life . Cases and controls were individually matched by gender to control the perception of negative impact on quality of life in this age group between sexes, since most studies demonstrated such association [12, 16, 31]. Even though the literature shows that there is no significant difference between boys and girls as to caries increment in the mixed dentition .