The Effects of Sodium Fluoride and Chlorhexidine Use on Salivary IL-6 and Matrix Metalloproteinase Levels in Children With Active Caries

Biomarkers to Be Measured in the Study and Expected Benefits:Biomarkers to Be Measured inthe Study and Expected Benefits:Dental caries is a multifactorial infectious disease with high prevalence that affects alarge proportion of the world's population. The fundamental pathogenesis of the diseaseis characterized by tissue destruction caused by complex and synergistic biologicalprocesses that arise from the interaction of acids‐produced through the fermentation ofdietary carbohydrates by bacteria‐with susceptible host factors such as dental hardtissues and saliva. The body develops an inflammatory response against dental caries,which is characterized by infection and tissue destruction; the purpose of this responseis to eliminate the agent that initiated the inflammation and to restore tissuehomeostasis.As a result of bacterial stimulation and recognition, odontoblasts, pulp tissuefibroblasts, and immune cells such as dendritic cells, macrophages, and neutrophilscollectively produce a large number of molecules; these include cytokines and chemokinessuch as interleukin‐1 beta (IL‐1β), tumor necrosis factor alpha (TNF‐α), interleukin‐6(IL‐6), interleukin‐8 (IL‐8), and prostaglandins, which prolong the inflammatory stateand thereby support the activation of innate and adaptive immune responses.IL‐6, produced by odontoblasts and immune cells, increases markedly in the inflamed pulp.IL‐6 neutralizes bacterial cell wall components by enhancing the secretion of LBP(lipopolysaccharide‐binding protein) and regulates the immune response by reducingpro‐inflammatory cytokine production. It also contributes to edema formation byincreasing vascular permeability. It has been reported that salivary IL‐6 may serve as apotential biomarker for assessing caries severity.As caries lesions progress toward the pulp, demineralization and collagen degradation inthe dentin matrix accelerate. The decrease in pH exposes collagen fibers to proteolyticenzymes, facilitating the demineralization of the dentin matrix. This acidic environmentalso accelerates caries progression by increasing the activation of MMPs (zinc‐ andcalcium‐dependent endopeptidases). MMPs are classified into five subgroups based on theirsubstrate specificity and structural similarities: collagenases, stromelysins,gelatinases, matrilysins, and membrane‐type MMPs. These enzymes can be activated in anacidic environment or by lactate released by cariogenic bacteria. MMP‐8 (neutrophilcollagenase) can cleave triple‐helical fibrillar collagens into characteristic 3/4 and1/4 fragments. MMP‐9 is a gelatinase capable of degrading type IV collagen. Theactivation of MMP‐8 and MMP‐9 plays a critical role in collagen degradation in dentincaries lesions.The activity of MMPs, which play a central role in dentin collagen degradation, alsostands out as an important target for maintaining tissue balance. The control of theseenzymes is primarily achieved through tissue inhibitors of metalloproteinases (TIMPs).TIMP‐1 and TIMP‐2 are the primary regulators of MMP activity and effectively preventexcessive extracellular matrix (ECM) degradation . TIMP‐2 exhibits strong inhibition ofpolymorphonuclear cell (PMN)‐derived MMPs, while TIMP‐1 demonstrates more pronouncedinhibition of fibroblast‐derived MMPs.Inhibition of MMP activity is considered a potential strategy for slowing cariesprogression and preventing dentin erosion. In this context, sodium fluoride (NaF) andchlorhexidine (CHX) are cited in the literature as the principal agents capable ofreducing MMP activity. NaF has been shown to inhibit the catalytic activity ofrecombinant MMP‐8 and MMP‐9. Similarly, CHX can largely prevent collagen degradation indemineralized dentin and can demonstrate long‐lasting anti‐MMP effects by bindingelectrostatically to the dentin matrix.All of these findings demonstrate that inflammation can be objectively measured throughboth local and systemic biomarkers. The dynamic interaction between pro‐inflammatorysignals and matrix degradation, along with the endogenous inhibitors involved in thisprocess, is of critical importance for the preservation of dentin tissue and the controlof caries progression. However, studies that comprehensively reveal the molecular‐levelinteractions of this axis, particularly in caries‐active children, are limited in theliterature. In this context, the aim of our study is to compare the biomarkers IL‐6,MMP‐8, MMP‐9, and TIMP‐1‐representing the key components of the inflammation‐matrixdegradation axis‐between healthy children and caries‐active children, and to evaluate theeffects of materials such as NaF and CHX used in caries prevention on these parameters.Biomarker Analysis The levels of IL‐6, MMP‐8, MMP‐9, and TIMP‐1 in saliva samples will beevaluated using human saliva enzyme‐linked immunosorbent assay (ELISA) kits. Biomarkeranalyses (ELISA) of the samples will be performed at the ALKU Faculty of MedicinePharmacology Laboratory.The obtained data will be statistically analyzed. Descriptive statistics: Quantitativevariables will be expressed as mean ± standard deviation or median and interquartilerange (IQR), and qualitative variables will be expressed as frequencies and percentages.Between‐group comparisons and within‐group changes over time will be evaluated usingappropriate parametric or non‐parametric tests.Results will be interpreted by correlating changes in salivary biomarker levels withclinical findings.