The purpose of this study was to determine whether baseline salivary inflammatory biomarkers could discriminate between different clinical levels of disease and/or predict clinical progression over a 3-week stent-induced biofilm overgrowth (SIBO) period.

168 participants were enrolled in a 21-day experimental gingivitis investigation and grouped according to clinical measures of periodontal status of health and diseased individuals representing each of five biofilm gingival interface (BGI) periodontal groups (H, G, P1, P2, P3). Stents were used to prevent plaque removal during brushing over one maxillary and one mandibular posterior dental sextant for 21 days. Clinical periodontal parameters and unstimulated saliva were collected at screening, baseline, and each week during SIBO. Saliva samples were assessed for levels of 13 different biomarkers by multiplex immunoassay.

Higher salivary levels of interleukin (IL)-1β, matrix metalloproteinase (MMP)-3, MMP-8, MMP-9, and neutrophil gelatinase-associated lipocalin (NGAL) were found in diseased groups compared to healthy at baseline. Conversely, higher IL-1 receptor antagonist (ra) levels were found in healthy patients at baseline. In addition, during SIBO MMP-1, tissue inhibitor of metalloproteinase (TIMP)-1, and TIMP-2 levels increased across all participant groups. A stepwise linear regression model using all salivary biomarkers demonstrated that at baseline increased IL-1ra (p=0.0044) and IL-6 (p=0.0093) were the two best predictors of change in probing depths during SIBO.

In summary, this investigation supports salivary levels of IL-1ra and IL-6 as potential indicators for significant probing depth changes during induced gingival inflammation. In addition, participants from BGI-P3 group (severe periodontitis) demonstrated elevated baseline levels of IL-1β, MMP-3, MMP-8, MMP-9, and NGAL compared to other study groups strengthening the relevance of participant's biological phenotype on salivary biomarkers expression