Introduction: Caries is a microbiologically caused disease that still affects humanity to a great extent. There has been a great deal of emphasis on the development of methods for assessing caries risk, identification of biomarkers and vaccine development strategies to control the incidence of caries, a disease with a known cause. Immunologic response plays an essential role in the development of caries. Saliva contains an inherent defense mechanisms as part of nonspecific immunity. The soluble receptor CD14 in the saliva, mediates in the recognition of Gram-negative and Gram-positive bacteria that can participate in the development of demineralization of hard dental tissue caused by caries. Previous studies did not investigate the relationship of sCD14 concentration in the saliva and caries activity, collected from adults. Only saliva collected from children and adolescents was tested, and the results showed differing conclusions. Objectives: The aim of this study was to determine the concentration of salivary sCD14 and salivary flow rate, pH and buffer capacity, in order to determine its potential role as a biomarker for caries activity. The aim was also to determine the dental status of all participants and to evaluate the prevalence of demineralization of hard dental tissues. Participants and methods: The sample consisted of a total of 88 healthy subjects, 20-40 years of age. Participants completed a questionnaire (illness, drugs, consummation of acidic drinks, sugar intake, smoking habits...) and informed consent. Excluding factors were: using anti-inflammatory drugs 2 weeks prior to saliva collection, illness, pregnancy, and chronic and acute infectious diseases. Then a clinical examination was performed to determine the dental status of each participant, using a mirror, dental probe and KaVo DIAGNOdent Pen because of its diagnostic values and to determine the strength of the demineralization of caries lesions. Excluding factors were: bleeding on probing, calculus, inflammations of oral mucosa, ongoing dental treatment (endodontics, sutures of oral mucosa...), and missing majority of teeth. Dental status was recorded using the DMFT and DMFS index. Participants were divided into three groups: 28 subjects without caries were the control group, 30 subjects with 1-5 caries were the first experimental group (E1) and 30 subjects with 6 and more caries were the second experimental group (E2). Methods used for collecting saliva samples were with stimulation (by chewing paraffin wax) and without stimulation of salivary secretion. In the saliva samples the flow of saliva, pH and buffer capacity of saliva is then determined. The concentrations of the sCD14 in all saliva samples were determined using matrix-matched commercial enzyme-linked immunosorbent assay ELISA. Results: The results showed a statistically significant (χ2 = 9.86; ss = 2; p = 0.007) higher concentration of sCD14 in resting saliva samples of participants with caries, both experimental groups (median E=198.0 ng/mL and E2=210.9 ng/mL) compared to the control group (178.4 ng/mL). With the unit increase in sCD14 concentration in resting saliva samples, the emergence of caries increased by 1%. The sensitivity of the sCD14 concentration in resting saliva for caries recognition was 68%, while the specificity was 57%. Both measures were in optimum ratio at 182.9 ng/mL concentration of sCD14 in resting saliva. The predictive value of sCD14 concentration in resting saliva (area below ROC curve = 0.70) for caries was statistically significant (p = 0.002). The median DMFS index was: for the control group 32, and for groups E1 and E2 30 and 28, respectively (the difference between the groups were not statistically significant). In this study, the control group had a statistically significant higher number of missing tooth surfaces (p = 0.036) and surfaces with filling (p = 0.001) compared to experimental groups. Participants of the E2 group with caries localized in the lateral region of the dental arch exhibited a statistically significant higher concentration of sCD14 in resting saliva (p = 0.003) with respect to the control group, rather than the E1 group. According to the same localization of caries in the dental arch, the difference for the E1 group was marginally statistically significant (p = 0.058). There was no statistically significant correlation between the concentration of sCD14 in saliva and the measurement of caries lesions by KaVo DIAGNOdent Pen device at different localizations in the dental arch. The median pH of resting and stimulated saliva did not show a statistically significant difference between the groups (control=7.3, E1 and E2=7.2), and no statistically significant association between the pH of saliva and concentration of sCD14 in saliva was observed. The higher buffering capacity of the stimulated saliva was statistically significantly related to the lower concentration of sCD14 in the stimulated saliva. Subjects with medium (pH 4.5-5.5) or low (pH <4.5) buffer capacity of stimulated saliva had a four-fold greater chance of developing caries compared to subjects with high buffering capacity (pH = 5.5). Conclusions: The increased concentration of sCD14 in the resting saliva can be used as a potential marker for the presence of caries. In addition to the concentration of sCD14 in resting saliva, a statistically significant predictor of caries activity also showed to be the buffering capacity of the stimulated saliva and the subjects with caries also had decreased flow rate of resting saliva as an important defensive factor by the host. Saliva collection methods and salivary sCD14 concentration determination are not standardized, which can be a problem for the interpretation of the results, in this type of study. Further studies in the future are required in order to achieve standardization for the collection of saliva samples and standardization of determination of salivary sCD14 concentration for a better performance of its role as a potential marker for carious activity.