8-isoPGF2α and 8-isoPGF2α-d4 were purchased at purity ≥99% from Cayman Chemical (Ann Arbor, Michigan, USA).
Phadebas® Alpha-Amylase Test was provided by Magle AB Life Sciences (Sweden).
TNF-α was quantified using the Quantikine® ELISA human TNF-α immunoassay (Cat. No. DTA00D) from R&D Systems (United States). Acetonitrile, methanol, and water at LC-MS grade (purity ≥99.9%) were from Fluka (Milan, Italy). Type I ultrapure water (18.2 MΩ-cm) for ELISAs was obtained using the Elga PURELAB Classic system (France).
All the liquid solutions and saliva samples were stored in sterile polypropylene containers from Eppendorf (Milan, Italy).
Phenex™-RC syringe filters (0.2 μm regenerate cellulose, 4 mm of diameter) were from Phenomenex (California, USA).
Salivette roll-shaped polyester swabs were purchased from Sarstedt (Nümbrecht, Germany).
A Macherey Nagel pehanon narrow range (6.0 < pH < 8.1) pH paper strips (Düren, Germany) with a resolution of 0.3 pH units was used to estimate the salivary pH.