Salivary tissue factor induces thrombin generation in a diurnal rhythm

Background: Upon tooth extraction, extravascular tissue factor (TF) initiates coagulation to arrest bleeding. Additionally, saliva is in constant contact with the wound and contains extracellular vesicle-derived procoagulant TF. Since the duration of postextraction bleeding is highly variable between patients, we hypothesized this may be caused by variation in saliva-derived TF-induced clotting activity.

Objectives: We aimed to assess the variability of saliva-induced thrombin generation (TG) in healthy individuals.

Methods: TG was performed according to the calibrated automated thrombinography (CAT) method. Diluted saliva was added (instead of recombinant TF and phospholipids [PL]) to normal pooled plasma (NPP) in the absence/presence of anti-TF antibodies. Saliva was collected from healthy individuals in the morning, afternoon and evening.

Results: Addition of saliva to NPP induced TG curves similar to those induced by r-TF and PL. Moreover, addition of anti-TF antibodies abolished saliva-induced TG, indicating TF-dependence. A large inter-individual variability (peak CV 31%, range 73220 nmol/L thrombin) in saliva-induced TG was observed. Interestingly, within subjects, saliva-induced TG was significantly (P = 0.009) increased in the morning (167 +/- 40 nmol/L thrombin) compared to the afternoon (124 +/- 39 nmol/L thrombin) and evening (123 +/- 38 nmol/L thrombin). This diurnal variation was not attributable to gingival stimulation or damage induced by tooth brushing.

Conclusions: We identified a diurnal rhythm in salivary TF activity that may have implications for tooth extraction and dental surgery, as performing invasive procedures in the morning may be beneficial for rapid coagulation. Future studies should correlate salivary TF to clinical outcome (ie, postextraction bleeding) and assess a possible relation with bacterial status in the oral cavity.