Impact of TiF₄ Varnish on the Oral Biofilm Microbiome in High-Caries-Risk Patients

Dental caries is a prevalent global disease, influenced by biofilm formation, dietary sugars, and host factors. Fixed orthodontic appliances increase the risk of noncavitated lesions, highlighting the need for effective prevention. Fluoride varnishes reduce demineralization and promote remineralization; however, their impact on the oral biofilm microbiome in high-caries-risk patients remains underexplored.

To profile microbial biofilms involved in caries lesions after treatment with sodium fluoride (NaF) and titanium tetrafluoride (TiF₄) varnishes using 16S rRNA sequencing of the oral biofilm microbiome.

A randomized crossover study was conducted with 13 participants (12-18 y) with fixed orthodontic appliances and at least 1 active noncavitated lesion. Participants underwent 4 stages: G1 (nontreatment), G2 (professional prophylaxis; PP), G3 (PP + NaF varnish), and G4 (PP + TiF₄ varnish). Clinical analyses (Nyvad and plaque indices) and supragingival biofilm sampling were performed. Bacterial DNA was extracted and amplified for 16S rRNA sequencing. Repeated-measures analysis of variance, Friedman/Wilcoxon with Bonferroni correction, Pearson chi-squared, and permutational multivariate analysis of variance tests were performed ( P < 0.05).

Shannon diversity (median, 25%-75%) values were as follows: G1 (6.25, 6.21-6.27), G2 (5.81, 5.77-5.83), G3 (5.63, 5.64-5.71), and G4 (5.76, 5.72-5.78). G2, G3, and G4 differed significantly from G1, with no difference among them ( P < 0.05). The most abundant genera were Veillonella (G1: 7.6%, G2: 10.6%, G3: 9.4%, G4: 5.7%), Corynebacterium (G1: 8.2%, G2: 7.3%, G3: 6.8%, G4: 10.4%), and Neisseria (G1: 4.0%, G2: 9.2%, G3: 9.6%, G4: 9.6%). Significant reductions were observed in the Prevotella/Haemophilus, Prevotella/Neisseria, and Prevotella/Rothia log-ratios compared with G1 ( P = 0.001). G2 reduced Prevotella/Haemophilus. G3 reduced Prevotella/Haemophilus and Prevotella/Neisseria. G4 reduced Prevotella relative to all 3 genera, indicating broader microbiome modulation.

PP, whether or not combined with fluoride varnishes, modified the biofilm microbiota. PP + TiF₄ varnish affected a greater number of bacterial log-ratios associated with commensal-dysbiotic balance, although no significant differences were found between treatment groups.Knowledge Transfer Statement:The findings from this study can guide clinicians in selecting the most effective fluoride varnish for high-caries-risk patients. By understanding how sodium fluoride (NaF) and titanium tetrafluoride (TiF₄) varnishes modulate the oral microbiome, clinicians can develop more targeted and effective prevention strategies. This knowledge has the potential to enhance patient outcomes by optimizing caries prevention during orthodontic treatment, allowing for more personalized and microbiome-focused approaches.