Salivary parameters of adults with diabetes mellitus: a systematic review and meta-analysis

Among the oral manifestations of diabetes mellitus (DM), salivary alterations stand out when considering that they can be linked to environmental changes that prompt other oral diseases. This study aimed to compare whether salivary parameters such as salivary flow, ionic composition, pH, and buffer capacity are altered in adults with DM.

A literature search was performed in 8 databases and the gray literature. Observational and clinical studies with populations >30 years old were included. The methodological quality of individual studies was assessed, 7 meta-analyses were performed, and the certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations approach (protocol registered at PROSPERO-CRD42021214632).

Of the 5,816 titles retrieved, 22 observational studies were included, representing a total of 1,202 individuals with DM and 946 normoglycemic control subjects. Individuals with DM had significantly lower unstimulated (mean difference [Md] = 0.13 mL/min; CI = 0.06-0.2; P = .0005) and stimulated (Md = 0.44 mL/min; CI = 0.13-0.75; P = .005) salivary flow rates, a lower pH when evaluated with electrodes (Md = 0.45; CI = 0.19-0.71; P = .0007), and a higher salivary urea (standard Md = 1.52; CI = 0.19-2.85; P = .03). No significant differences were found in the other parameters.

Although the certainty of evidence was low because of the type of studies included, this review indicated salivary alterations in individuals with DM, such as hyposalivation, pH, and urea concentration.