Saliva composition from birth to adolescence: a systematic review of the literature

BACKGROUND: This systematic review examined the saliva composition of healthy children from birth to 18 years of age by assessing the salivary flow rate, pH, buffering capacity, and ion levels. This review followed the PRISMA guidelines. A systematic search was performed using PubMed, the Cochrane Library, and Scopus. Information regarding the salivary flow rate, pH, buffering capacity, and ion levels in whole saliva was systematically collected, and a qualitative synthesis was performed. The methodological quality of the studies was assessed using the JBI Critical Appraisal Tools.

HIGHLIGHT: Of the 3,268 retrieved studies, 41 were eligible for inclusion. Unstimulated salivary flow showed an age-related decrease, whereas stimulated salivary flow increased with age. The pH of the saliva remained consistent across different ages, whereas the buffering capacity showed an age-related increase. Salivary sodium, calcium, and potassium levels were lower in the younger children than in the older children. An investigation of salivary ion levels revealed lower average fluoride concentrations in Asian populations than in European populations. Most studies had a low or moderate risk of bias.

CONCLUSION: This systematic review highlights age-dependent differences in salivary flow and composition in healthy children from birth to 18 years of age. The flow rate of unstimulated saliva decreased with age, while the flow rate of stimulated saliva increased. The salivary pH remained stable, whereas the buffering capacity increased with age. Furthermore, salivary sodium, calcium, and potassium levels tend to increase with age. These findings underscore the dynamic nature of salivary composition from childhood to adolescence.