To diagnose dental pulp vitality, electric pulp tester has been widely used, which is a method to test
condition of nerve. However, especially in the case of patients with trauma, nerve desensitization could temporarily occur
even though nerve might be recovered by blood flow within the pulp later, which implies that blood flow in dental pulp
is also an important factor for diagnosing vitality. This paper described the development of a probe that relatively
measured blood flow in dental pulp using photoplethysmography (PPG). The probe emits four different wavelength light
sources including three visible and an infrared light. We tested which light source detect sensitively the blood flow in
dental pulp. As a result, green light had the largest peak to peak voltage and the power spectrum among different
wavelengths.