Evaluation of the Salivary-Free Amino Acids Levels (Glycine and Proline) as Caries Susceptibility Predictors in 8- to 10-Year-Old Children

Abstract This research investigated the association between levels of salivary free amino acids (glycine and proline) and caries susceptibility in healthy children versus children with active caries, to inform future strategies for the detection and prevention of pediatric dental caries. The study had a case–control design and was conducted with 80 healthy children (8–10 years old) recruited from private and governmental primary schools in the Rusafa of Baghdad city, Iraq, classified according to their level of caries activity (active caries, n = 40; inactive caries, n = 40) based on their caries experience and Snyder test results. Then, unstimulated whole saliva was collected for amino acid analysis performed by reversed-phase high-performance liquid chromatography. Statistical analysis was conducted using the Shapiro–Wilk test for symmetric distribution of the quantitative variable, the independent t-test was utilized for making comparisons, and Pearson's correlation was used to verify if there is a linear relationship between two quantitative factors that are normally distributed. Glycine was the most abundant amino acid in the saliva, followed by proline from 113 components identified in the saliva. Glycine levels decreased significantly (p < 0.05) with the active caries group, regardless of gender differences. On the contrary, a significant positive correlation was established between increased levels of salivary proline (p < 0.05) and the active caries group. The higher salivary glycine and proline levels may serve as potential biomarkers for assessing caries susceptibility and informing preventive strategies.