The 91 subjects who completed the treatment were similar to the 39 who dropped out of the treatment regarding their socio-demographic status, in terms of their family structure, number of siblings, parents' education, economic resources, and other support.
Studies that have analysed the effect of parental characteristics (SES, family environment, family structure, number of siblings, household crowding, parents' age, and parents' oral health literacy) on children's OHRQoL were included.
Univariate analysis revealed that school type, monthly family income, mother's education, family structure, number of siblings, use of cigarettes, alcohol and drugs in the family, parents' perception of oral health of schoolchildren, schoolchildren's self perception their general and oral health, orthodontic treatment needs were significantly associated with poor OHRQoL (p < 0.001).
A search for eligible journal articles was undertaken in August 2013, using PubMed, Medline via OVID, CINAHL Plus via EBSCO, and Cochrane databases to answer if parental characteristics (SES, family environment, family structure, number of siblings, household crowding, parents' age, and parents' oral health literacy) influence children's OHRQoL.
In order to take into account confounding factors, data on family structure like number of siblings, birth order will be recorded as well as details of birth and breastfeeding, hygiene, socioeconomic status, annual health status, and food consumption.
Four other domains were not associated with a subscale score and consist of stand-alone items only: Support the Child, Support Siblings, Structures of Care, and Provide Bereavement Follow-up.
Mothers' age, family structure, household crowding and presence of siblings were significant predictors of children's OHRQoL.
Mothers' age and home environment characteristics, such as family structure, household crowding and presence of siblings were significantly related to the outcome.
The family structure is also simplified, with analysis of siblings only, which may limit the interpretability of variance component analysis and the possible contribution of a common environment is therefore difficult to evaluate.
To preserve family structure, allocation of the siblings of twins to one of the two cohorts, was based on the age of the twins, which resulted in a slight overlap in age between the cohorts (8 siblings older than 36 years were allocated to the young cohort, 2 siblings younger than 36 were allocated to the older cohort).
