Background: This study assumes that while all families are unique, families share common tasks that must be fulfilled as part of their functioning and the definition of whether the family process is functional or not is specific and may be unique to the family and is dependent upon what the family perceives as being normal, while considering cycle demands, resources and socio cultural influences. Objectives: To explore the role of family functioning in chronic periodontitis. Methods: The Outer North East London (ONEL) Oral Health Needs Assessments collected data in a representative sample of 2,343 adults aged16-65 and 1,174 children 3-4 years old in 2009-10. Data were collected through home visits by trained dentists and interviewers, and included dental clinical examinations and answers to questionnaires. Family function in the domains general functioning, problem solving, communication, roles, affective responsiveness, affective involvement and behaviour control was assessed using the Family Assessment Device (FAD) Epstein et al., 1983). Chronic periodontitis was defined as having at least one interproximal site with pocket depth of 4 mm or more. Results: Chronic periodontitis was associated with family functioning in the domains general functioning (odds ratio:0.45; 95%CI: 0.25-0.84), communication (odds ratio: 0.55 95%CI: 0.30-0.98), affective involvement (odds ratio:0.56; 95%CI: 0.34-0.94), affective responsiveness (odds ratio:0.47; 95%CI: 0.26-0.81) and behaviour control (odds ratio:0.40 95%CI: 0.22-0.74) after adjustment for ethnicity and socioeconomic position (NS-SEC). However, after adjusting for oral health related behaviour (tobacco consumption and plaque score) only the domain of general functioning (odds ratio: 0.51 6 95%CI: 0.27-0.97) affective responsiveness (odds ratio 0.52; 95%CI: 0.29-0.92) and behaviour control (odds ratio 0.46; 95 CI: 0.25-0.83) remained significantly associated with chronic periodontitis. Family functioning domains general functioning, communication, affective involvement, affective responsiveness and behaviour control also potentially partially mediates the relationship between socioeconomic position and chronic periodontitis experience. Conclusion: Efficient family functioning in the domains of general functioning, affective responsiveness and behaviour control may act as protective factors against chronic periodontitis.