# Pulse oximetry as a Diagnostic Tool to Determine Pulp Vitality: A Systematic Review
###### Abstract  
Pulse oximetry (PO) can be used as a technique to assess vascularization. Although it is commonly used in the field of medicine, it still has limited use in dentistry. The aim of this study is to evaluate, by means of a systematic review, if pulse oximetry is a viable and effective system to determine pulp vitality and assess the clinical criteria for its use. A literature search was performed in Medline, Scopus, Embase, and Web of Science databases. Clinical studies using pulse oximetry as a tool to determine pulp vitality in permanent teeth were eligible. Quality assessment of the included studies was performed following the Quality Assessment for Diagnostic Accuracy Studies (QUADAS-2) guidelines. A total of 24 articles were included in the review. The subjective test most compared to PO was the cold test. PO has shown a good sensibility and specificity, and it has been used in different clinical situations. Pulse oximetry has a high potential as a tool for the diagnosis of pulp vitality. However, the absence of a specific pulse oximeter for a dental practice, among other limitations, added to the lack of evidence on how different systemic and oral pathologies may affect the pulp's oxygen saturation levels, which hinders its clinical use.  
diagnosis; endodontics; pulse oximetry; pulp vitality; systematic review +
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Current objective tests, however, measure the true vitality indicator, namely, pul-pal blood flow, and thus may offer higher results in the statistical measures of performance, i.e., sensitivity and specificity. These methods include photoplethysmography, dual-wavelength spectrophotometry, thermography, and, most commonly, laser Doppler flowmetry, pulse oximetry, etc. [5; 6].  
Pulse oximetry is a non-invasive method that is based on 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\" [7] (p. 329). Pulse oximetry systems consist of a sensor with two diodes of different wavelengths that will be absorbed by deoxygenated and oxygenated hemoglobin (red light (600 nm) and infrared light (940 nm), respectively), and a photoreceptor connected to a microprocessor, which captures the emissions and obtains the pulp oxygen saturation (SpO\({}_{2}\)) and pulse data. Because pulp blood flow is pulsatile, this creates constant changes in the absorption of light by the photoreceptor, which will determine the SpO\({}_{2}\) levels comparing the data obtained with the previously established curves of oxygenated and deoxygenated hemoglobin [8].  
Currently, no specific pulse oximeter is commercially available for clinical use in the field of dentistry. However, the use of this technique has been investigated as a diagnostic tool for pulp vitality. In these investigations, the absence of a standardized pulse oximeter results in the use and assessment of custom-made probe designs for the pulse oximeter sensors [9; 10; 11]. The heterogeneity of these designs added to the methodological differences between studies hinders the applicability of pulse oximetry to the clinical setting. Thus, providing a qualitative synthesis of the available evidence regarding this matter is essential in order to determine the potential use of pulse oximetry as a diagnostic tool.