This study aims to understand how oral bacteria that cause tooth decay and gum disease spread among family members and whether treating multiple family members can reduce the return of these bacteria after dental treatment.

Families with children aged 5-12 years will be recruited from university dental clinics. Participants will be assigned to one of three treatment groups: treatment for the child only, treatment for the child and parents, or treatment for all family members. Researchers will collect oral bacterial samples from family members before and after treatment and will monitor close-contact interactions within the household using wearable proximity-tracking devices.

The study will also collect information about oral health habits, family interactions, and environmental factors that may influence bacterial transmission. By combining bacterial DNA analysis with information about family contact patterns, researchers hope to better understand how oral bacteria are shared within households and whether family-based treatment approaches can reduce bacterial recolonization after dental therapy.

The results of this study may help improve strategies for preventing childhood tooth decay and gum disease by addressing family-level sources of bacterial transmission.

Oral diseases, including dental caries and periodontal diseases, are among the most prevalent chronic diseases worldwide. Although oral pathogens are known to be transmissible, the mechanisms by which disease-associated bacteria spread within families and contribute to recolonization after treatment remain poorly understood.

This randomized clinical trial will investigate familial oral microbial transmission and the role of household-level interventions in modifying microbial recolonization following professional dental therapy. Forty-five families will be recruited from university dental clinics and randomized into one of three intervention groups: (A) child-only plaque disruption, (B) child plus parent plaque disruption, or (C) plaque disruption for all family members. Eligible households must include at least two children aged 5-12 years and at least one adult requiring periodontal therapy or a child at high risk of disease recurrence.

Oral microbial samples will be collected from all participating family members at multiple oral sites, including saliva, buccal mucosa, tongue, supragingival plaque, and subgingival plaque. Follow-up sampling will occur at 1 week, 4-6 weeks, and 3 months after treatment. Participants will complete oral health and demographic questionnaires, and all family members will wear Ultrawide Band (UWB) proximity-tracking devices to quantify real-time interpersonal contact patterns within the household. Airborne microbial sampling will also be performed to investigate potential aerosol-mediated transmission pathways.

Bacterial DNA sequencing, source-tracking algorithms, and quantitative PCR analyses will be used to identify sources of microbial recolonization and quantify transmission among family members. Generalized Linear Mixed Models will be used to examine associations between microbial transmission, proximity measures, demographic variables, and household characteristics.

The primary objective is to determine whether reducing familial pathogen burden through household-level treatment decreases recolonization of oral pathogens following dental therapy. Secondary objectives include characterizing contact-dependent and airborne transmission pathways and identifying factors associated with oral microbial transmission within families.

Inclusion Criteria:

• Families with at least two children aged 5-12 years living in the same household.
• least one parent or guardian diagnosed with Stage II or III periodontitis requiring non-surgical periodontal therapy.
• At least one child who has undergone caries treatment and is considered at high risk for disease recurrence.
• Willingness of all participating household members to provide oral samples and participate in study procedures.
• Ability of participants or their legal guardians to provide informed consent, and assent from children where applicable.

Exclusion Criteria:

• Children living in multiple households or shared-custody arrangements during the study period.
• Households unable to complete study visits or follow-up procedures.
• Individuals unwilling or unable to comply with study procedures.
• Individuals who do not provide informed consent or assent, where applicable.
• Medical or behavioral conditions that, in the opinion of the investigators, would preclude safe participation in the study.

All-Equal numbers of male and female participants will be recruited.

A decision regarding sharing of individual participant data (IPD) has not yet been made. Data sharing plans will be determined in accordance with University of Alberta policies, participant consent, and applicable ethics requirements.

Participants and investigators will know which treatment group the family has been assigned to.