Improved Oral Health in Head and Neck Cancer Survivors

The goal of this clinical trial is to learn if an oral care programme, designed as a multicentre two-armed randomised controlled trial (RCT), can prevent or mitigate late oral sequalae following completion of head and neck cancer (HNC) treatment, and assessing its impact on health-related quality of life (HRQoL), oral health, work ability, nutritional status, psychological well-being, and healthcare-related economic costs. The intervention consists of an oral care programme given to the intervention group (HNC survivors) from six months after the end of treatment and every three months for three years. The main questions it aims to answer are: * Does the intervention improve oral health, nutritional status, HRQoL, and reduce stress and anxiety compared with standard care? * Does the intervention reduce the duration of sick leave and improve return-to-work outcomes compared with standard care? * Is the intervention cost-effective from a health economic perspective? * Does the intervention improve patients' self-efficacy in managing their oral health and related challenges compared with standard care? * Does the intervention influence self-reported oral health, oral health-related behaviours, and oral health knowledge over time compared with standard care? * Do the effects of the intervention differ according to age, sex and sociodemographic factors? * Does the intervention affect salivary composition and salivary biomarkers over time compared with standard care?