Assessing the Impact of Heyndrickxia coagulans Administered Through Sugar-Free Chewing Gum on Dental Biofilm: A Double-Blind Randomized Controlled Trial

<b>Background:</b><i>Heyndrickxia coagulans</i> has emerged as a candidate for oral health applications, and chewing gum offers a promising delivery method. This study evaluates whether <i>H. coagulans</i> delivered via sugar-free chewing gum can induce detectable changes in plaque microbial ecology. <b>Methods:</b> A randomized, double-blind, placebo-controlled clinical trial was conducted on 52 healthy adults. Participants consumed probiotic or control gum for 4 weeks. Dental plaque was collected at baseline (T₀), mid-intervention (T₁), end of intervention (T₂), and one week post-intervention (T₃). qPCR quantified <i>H. coagulans</i>, while 16S rRNA gene profiling assessed microbial diversity and taxonomic composition. Statistical analyses included rank-based difference-in-differences models, Wilcoxon and Mann-Whitney tests, and differential abundance inference based on negative binomial modeling. <b>Results:</b> Forty-four subjects completed the study. In the Intervention group, the strain was detected in 71.4% of participants at T₁ and 61.9% at T₂, and it persisted in 9.5% at T₃. Differential abundance analysis revealed a broad depletion of taxa linked to oral dysbiosis at T₂ with partial persistence at T₃, along with selective enrichment of beneficial strains. <b>Conclusions:</b><i>H. coagulans</i> delivered via chewing gum can reach the dental biofilm and induce modest, transient shifts in microbial composition. However, these biofilm ecology findings should be interpreted in the context of clinical outcomes.