SERPINA5 and periapical periodontitis: Bacterial microbiota of apical periodontitis showed distinctive changes in comparison to oral mucosa controls, showing two main distinct features: (1) a reduced microbiota diversity in PAI-1 and PAI-3 samples in comparison to the oral controls and (2) an increased trend from PAI-1 to PAI-3 toward the anaerobic species, independently from the relatively large inter-individual variability present in patients.