Oral Health, Saliva Bacteria, and Disease Activity in Children With JIA: A Cross-Sectional Study.

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease in children, characterised by alternating periods of active disease and remission. Despite therapeutic advances, joint involvement in the hands, wrists, or temporomandibular joints can hinder daily oral hygiene practices, and long-term medication use may affect the oral microenvironment, increasing the risk of dental caries and gingivitis. In current routine rheumatology follow-up in China, oral health status is not systematically assessed; it is usually addressed only when the child complains of symptoms, leading to delayed recognition and intervention.

This single-centre, cross-sectional observational study aims to compare oral health status between JIA children with different levels of disease activity and to preliminarily explore the association of salivary local biological characteristics with disease activity. No intervention is applied. All data are collected at a single time point during a regular outpatient visit.

Study Population Children aged 6 to 16 years who meet the ILAR classification criteria for JIA are eligible. Exclusion criteria include use of systemic antibiotics within the past 3 months, ongoing fixed orthodontic treatment, presence of other systemic conditions known to affect oral health (e.g., diabetes, Sjögren's syndrome), or inability to cooperate with the examination.

Grouping and Assessments At enrolment, two experienced rheumatologists independently classify each participant as having "active disease" or "clinical remission" based on standardised clinical assessment (joint examination, physician global assessment, and routine laboratory inflammatory markers). During the same visit, the following are completed: (1) collection of demographic and disease-related data; (2) a comprehensive oral clinical examination conducted by trained dentists, covering dental hard tissues, periodontal soft tissues, and oral hygiene status; and (3) collection of unstimulated whole saliva for subsequent analysis of local inflammatory markers and microbial community profiles. All data are recorded using coded identifiers to protect participant privacy.

Statistical Analysis Oral health parameters will be compared between the two groups, with multivariable methods used to control for potential confounders such as age, sex, and disease duration. The correlation between continuous disease activity scores and composite oral health indices will be evaluated. Saliva data will be explored for associations with disease activity and oral health parameters.

Clinical Significance This study addresses a long-neglected but clinically relevant question: whether disease activity in JIA is associated with oral health status. If children with active disease show poorer oral conditions, this would support the need for rheumatologists to actively inquire about oral hygiene habits and dental history during follow-up, and to consider incorporating basic oral health screening (e.g., questions on brushing, gum bleeding, toothache) into routine visits. Through this work, we aim to promote clinical awareness of oral health issues in children with chronic diseases and advocate for the inclusion of oral health assessment as a fundamental component of JIA chronic disease management, fostering collaboration between paediatric rheumatology and dentistry, and ultimately improving patients' quality of life.

Inclusion criteria

• Children aged 6 to 16 years.
• Diagnosed with juvenile idiopathic arthritis according to the International League of Associations for Rheumatology (ILAR) classification criteria, excluding the systemic-onset subtype.
• For the active disease subgroup, all of the following must be met:

• Presence of active arthritis as determined by the attending rheumatologist;
• Planned initiation or adjustment of disease-modifying antirheumatic drugs (DMARDs) or biologic agents within 1 month after enrolment;
• Meeting the following disease activity criterion: JADAS-27 score > 1. For the remission subgroup, the following must be met: JADAS-27 score ≤ 1 and clinically stable disease.
• Able to cooperate with oral examination and saliva sample collection.
• Written informed consent provided by a legal guardian, with assent obtained from the child.

Exclusion criteria

• Use of systemic antibiotics within 3 months prior to enrolment, or use of mouthwash containing antibiotics, corticosteroids, or chlorhexidine within 1 month prior to enrolment.
• Diagnosis of other autoimmune diseases (e.g., systemic lupus erythematosus, Sjögren's syndrome), chronic inflammatory diseases (e.g., inflammatory bowel disease), diabetes mellitus, congenital heart disease, or other systemic conditions that may affect the study outcomes.
• Presence of acute infection at the time of sampling or examination (e.g., body temperature > 37.5°C, upper respiratory tract infection, acute oral infection).
• Significant cognitive or behavioural impairment that prevents cooperation with study procedures.
• Ongoing or planned orthodontic treatment within the next 6 months.