# Pulse oximetry as a Diagnostic Tool to Determine Pulp Vitality: A Systematic Review
## 4 Discussion
Pulse oximetry has demonstrated to be a helpful tool in diagnosing pulp vitality in normal circumstances and in patients that had undergone radiotherapy [21,22] with sickle cell anemia [28] after alveolar cleft bone grafting [23], to diagnose different states of pulp inflammation [4,15,20,26] in patients with periodontal disease [16] after an at-home bleaching treatment [27], and in recently traumatized teeth [4,10]. As mentioned previously, four articles studied the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of PO as opposed to other diagnostic methods [2,9,20,29], and in all of them, PO showed higher results. A clinical test's sensitivity refers to its ability to identify correctly the patients that have the disease, while specificity refers to the capability of a clinical test to properly identify the patients who do not have the disease. The PPV of a clinical test stands for the probability that a patient with a disease is a true positive, while the NPV is the probability that a patient with a negative result truly is healthy [34]. The aforementioned results act as evidence for the reliability of pulse oximetry as a tool for classifying truly vital and non-vital teeth. However, pulse oximetry still has many limitations. To obtain a valid result, both diodes need to be parallel, which becomes a challenge because currently there are no pulse oximetry specifically designed for dentistry, and any minor head movement from the patient (such as swallowing) can destabilize the diodes and alter the results [35]. [PERSON] et al. (1996) [11], [PERSON] et al. (2007b) [20], and [PERSON] et al. (2012) [9] fabricated their own probes, in which sensors could be held parallel and fit onto the teeth anatomy. Except for [PERSON] et al. (1996) [11], who did not find any diagnostic use for pulse oximetry, [PERSON] et al. (2007b) [20] and [PERSON] et al. (2012) [9] concluded that pulse oximetry is reliable, effective, and precise as a diagnostic tool for pulp vitality. Other factors, such as ambient light, the transmitter light power, or surrounding tissues, have to be taken into consideration. The pulp is surrounded by hard tissues (enamel and dentine), which can have different thicknesses and morphologies, acting as an obstacle for the light, which scatters through the enamel prisms and dental tubules. The presence of restorative materials (i.e., composite resin, glass ionomer) and pulp cappers (i.e., calcium silicate cements) may also hinder the measurement since they can also act as an obstacle for the light source [36]. As a result, oxygen saturation levels shown in the pulse oximetry may be lower. Nevertheless, pulse oximetry could be investigated as a potential tool to monitor pulp vitality after vital pulp treatment or regenerative endodontic procedures [37,38]. The pulp's anatomy and its distance from the sensor are other factors that could influence the reading. Moreover, age plays an important role, resulting in a series of time-dependent morphophysiological changes in the pulp complex--dentine continues its growth, and there could be deposition of mineralized tissue in the pulp and root canals [6]. This, combined with a decrease in pulpal blood flow, may hinder the dispersion of light, altering the pulse oximetry's reading. Regarding the influence of age on pulp vitality results using pulse oximetry, [PERSON] et al. (2015) [33] and [PERSON] et al. (2017b) [19] studied SpO\({}_{2}\) levels among different age groups, concluding that younger participants had higher levels of saturation than those of greater age. Regarding the quality assessment, the items regarding patient selection exhibited a low risk in all studies, although only one study enrolled a random sample [23].