Background: Congenital heart disease (CHD) is one of the most common congenital anomalies in children. As the risk for endocarditis following bacteraemia is more common during daily oral hygiene routines, such as tooth brushing, than during dental treatment, the maintenance of optimal oral health in children with CHD may be considered of outmost importance. Children with CHD have a higher caries prevalence compared to healthy controls.

Aim: The primary aim of the study is to explore if an educational intervention including information, counselling and support provided at early stage to families affected by major CHD, or CHD combined with a syndrome, can increase the awareness of the importance of maintaining of good oral health, and avoid the development of poor oral health including dental caries, leading to less dental anxiety and a higher oral heath related quality of life. The secondary aim is to elucidate factors associated with the development of poor oral health and/or orofacial dysfunction as well as family attitudes and needs of support.

Hypothesis: Early information, counselling and support will lead to a) increased awareness of the importance to maintaining good oral health, b) prevent the development of poor oral health and dental caries, c) lead to less dental fear, and d) lead to higher oral heath related quality of life.

Study design: Randomized educational intervention trial. Study population: Children born in Finland and under 12 months of age in 1.7.2017-31.12.2021 with, a) major CHD and potentially included in the criteria of endocarditis prophylaxis, or b) with a major CHD combined with a chromosomal syndrome, will be offered to participate in the study. Patients will be recruited until 200 patients are obtained at the Helsinki University Children's Hospital. A control group consisting of approximately 100 healthy children will also be recruited at birth.

Main outcomes: Dental caries, dental anxiety, oral health related quality of life, and awareness of importance to maintain and behaviour to maintain good oral health.

Significance: Better information to patients leads to better possibility to achieve good oral health. Better oral health leads to 1) less dental procedures and thereby less dental anxiety, 2) less dental procedures under general anaesthesia, which may potentially be a risk procedure for the child with CHD, and 3) better oral health related quality of life.

Power analysis:

Children with CHD are at high risk of developing caries (Stecksén-Blicks C et al 2004). In Swedish high-risk areas for developing caries, 12 % of three-year-old children had moderate and severe carious lesions (ICDAS II 3-6) and 11% initial carious lesions (ICDAS II 1-2) (Anderson et al 2016). Based on the assumption that 10% in the intervention group and 30% in the control group will develop caries (ICDAS II 1-6), p<0.05 and power 0.80, a sample size of at least 65 individuals in each age group is required. 1.7.2017-31.12.2021 198 Finnish speaking families will be offered to participate in the study. To secure an even distribution block randomization will be used. The patients will be randomized into blocks of 4 and 8, with the help of www.randomization.com (Pandis et al 2011).

Inclusion criteria:

• Age < 12 months and prostethic cardiac valve or patient likely to undergo valve surgery using foreign material including homograft (potentially included in the criteria of endocarditis prophylaxis)
• Age < 12 months and unrepaired cyanotic CHD including palliative shunts and conduits
• Age < 12 months and repaired CHD with residual defects at the site or adjacent to the site of the prosthetic patch or device which inhibits endothelialization
• Age < 12 months and cardiac transplantation recipient or listed for transplantation (potentially included in the criteria of endocarditis prophylaxis)
• Age < 12 months and cardiomyopathy (potential cardiac transplantation recipient)
• Age < 12 months and chromosomal abnormality or syndrome and any invasive intevention (surgery or cath) for CHD or likely to require invasive intervention for CHD

Exclusion criteria:

• Neither parent amenable to comprehend intervention instructions provided in Finnish
• Child in out-of-home care (eg foster care)