pulse oximetry ( in endodontics )

Principle

The oximeter applies a principle known as the Beer-Lambert law, which states that an unknown concentration of solute (hemoglobin) dissolved in a known solvent (blood) can be assessed by the light absorption of the solute.

Uses in endodontics

 To determine the vitality of tooth

Mechanism

A pulse oximeter uses a probe containing two light-emitting diodes (LED5): one transmits red light (approximately 660 nm), and the other transmits infrared light (900—940 nm) to measure the absorption of oxygenated and deoxygenated hemoglobin, respectively (it operates at 500 on/off cycles/s). Oxygenated and deoxygenated hemoglobin absorb different amounts of red and infrared light. This light is received by a photodetector diode connected to a microprocessor. The pulsatile change in the blood volume causes periodic changes in the amount of red and infrared light absorbed by the vascular bed before reaching the detector. The relationship between the pulsatile change in the absorption of red light and infrared light is assessed by the oximeter to show the saturation of arterial blood. It uses this information, together with known absorption curves for oxygenated and deoxygenated hemoglobin, to determine the oxygen saturation levels.

                                          REF: J Endo 2009;35:329—333