Information Quality, Content Scope, and Audience Engagement of Popular Turkish Instagram Posts on Tooth Whitening: A Cross-Sectional Content Analysis

Background: Social media platforms, particularly Instagram, have become significant sources of health information, yet the quality of dental content remains underexplored. This study compared the scope and reliability of information in popular Turkish-language Instagram posts on tooth whitening by poster source and examined associations with post format, purpose, and whitening approach. As a secondary aim, the association between information quality and normalized audience engagement was investigated within this algorithmically curated sample. Methods: This cross-sectional content analysis included 500 publicly accessible Turkish Instagram posts retrieved under the hashtag #dişbeyazlatma. The posts were classified by source, purpose, format, and whitening approach. Content scope and information reliability were assessed using the Descriptive Coverage Index (DCI) and Modified Treatment-Information Reliability (MTIR) scores by two calibrated evaluators. Engagement Rate was calculated as (likes + comments)/follower count × 100. Results: Most posts originated from dentist/clinic accounts (75.8%) and were marketing-oriented (72.0%). Dentist/clinic accounts demonstrated significantly higher MTIR scores than independent users and brand accounts (p < 0.001), whereas DCI did not differ significantly across sources. Raw engagement differences disappeared after normalization (p = 0.408). Reel posts scored higher than photo posts on both measures; carousel posts scored higher than photos on MTIR but not DCI. In-office whitening content scored significantly higher than DIY- or OTC-focused posts on both measures (p < 0.001). A weak positive association was observed between MTIR and Engagement Rate (r = 0.141). Conclusions: Popular Turkish Instagram posts on tooth whitening exhibited substantial variability in content scope and reliability. Independent users commanded greater raw audience reach yet predominantly produced DIY-focused content with substantially lower content scope scores than in-office and multi-method posts, and among the lowest reliability scores, raising a public health concern within this high-visibility content stratum. These findings may inform content development strategies for dental professionals and public health communicators targeting Turkish-speaking audiences.