Inclusion Criteria:  Medical status: healthy individuals with no current and past medical findings. Medications: no current medications.  Both mature vital ipsilateral mandibular premolars:  Healthy premolar (ICDAS code 0) Carious premolar (ICDAS code 4-6).  Periapical status  Healthy premolar - Periapical Index. (Code 1). Carious premolar - Periapical Index. (Code 1).  Periodontal status  Healthy premolar - Classification of periodontal diseases and conditions (Code 0). Carious premolar - Classification of periodontal diseases and conditions (Code 0).  Exclusion Criteria:  Patients with oral and maxillofacial syndromes and anomalies. Pregnant and nursing mothers. Class V carious lesions (sensor of pulse oximeter was placed on intact buccal, lingual and cervical surfaces). Teeth with extracoronal restorations. Teeth with developmental defects and other anomalies. Dental trauma. Teeth with symptoms of irreversible pulpitis.