TESTING OF PULP VITALITY BY PULSOXIMETRY

Headnote

Abstract

The methods applied for diagnosing the health condition of the pulp tissue are numerous, however, nowadays, an increasingly higher number of conventional tests are replaced by some objective, non-invasive, painless and reliable tests. Among them, pulse oximetry is a method for the investigation of pulp vitality based on oxygen saturation (Sa02) of the hemoglobin from the blood present in the pulp vascular bed, as a means of differentiating among the vital and the non-vital teeth. In the present study, registrations were made on a group of 120 frontal maxillary teeth, in patients with ages between 20 and 40 years, on using a digital sensor modified by the pulse oximeter with which the pulse and the values of oxygen saturation were measured at the level of both teeth and right hand finger. The mean Sa02 value in the pulp blood of the vital teeth was of 83.30% for the central incisor, of 78.51% for the lateral one and of 84.56%, respectively, for the canine; the value recorded at finger level was of 97%. In the non-vital teeth, the Sa02 value measured on the pulse oximeter was of 0%. Pulse registration showed mean values of 70.56 beatings/min at tooth level and of 70.88 beatings/min, respectively, at finger level.

The results of the present study may confirm that pulse oximetry represents a simple, non-traumatic, efficient and objective method for testing the vitality condition of the dental pulp.

Keywords: endodontic diagnosis, pulse oximeter, tests of pulp vitality.

INTRODUCTION

In endodontics, establishment of a correct diagnosis represents a complex process, in which the data obtained by the physician through clinical and paraclinical examination are synthesized and analyzed for demonstrating any deviation from the normal dental pulp condition. [1]

One of the main factors orienting the therapeutical action involves evaluation of pulp tissue vitality. Investigation of pulp vitality is a diagnosis procedure that should be viewed as a synthesis of the disease history, of the personal dental antecedents referring to the respective tooth, of the clinical, paraclinical examinations and of the special vitality tests, and not only as a singular result of an unique parameter [2].

Conventionally, the dentist usually relies on tests recording the reactivity of the patient to some stimulus, as well as on his analysis of the response provided by the patient to the respective test. The conventional tests, represented by thermal stimulation (cold or of warm application), electrical stimulation or direct stimulation of dentin (the test of cavity) do not represent the ideal tests for checking of pulp vitality, several reasons being here involved, such as:

- the nervous system, extremely resistant to inflammation, may remain reactive, even if all the surrounding tissues are degenerated; consequently, testing of the sensorial function may offer a positive response when the pulp is deteriorated (a false-positive response) [3];

- these tests may be accompanied by unpleasant sensations for the patient [4];

- in cases of calcarous (degenerescent) metamorphosis, teeth having suffered recent traumatisms, or teeth with an incompletely formed root may provide no response to the stimuli (a false-negative response) [5].

Several researchers [6-8] assert that testing of pulp vascularization would be more suitable for testing pulp vitality than dental pulp inervation.

The recent attempts made at developing a method capable of analyzing pulp vascularization include: double wavelength spectrophotometry, lasser doppler flowmetry (LDF), photopletismography), lasser transmitted light laser (TLL - the experimental variant for LDF) and pulsoximetry [9-11].

The pulse oximeter is a non-invasive device measuring the oxygenation degree of hemoglobin, largely employed in medical practice for registering the oxygen saturation (Sa02) of blood during administration of intravenous anaesthesis, by means of a sensor positioned at the level of either hand or foot finger, or ear [12]. It has been invented in 1970, by Takuo Aoyagi, a biomedical engineer working at Shimadzu Company, in Kyoto, Japan [13].

The pulse oximeter uses red and infrared wavelengths that transilluminate a vascular bed, detects the peaks of pulsatile vascular circulation and uses this piece of information for registering oxygen saturation in blood, and also pulse ratio. Due to its simple economic application, it is the most commun manner of recording the saturation of blood oxygen. [4,14]

The pulse oximeter contains two emitting diodes (LEDs) mounted in opposite position with a photodetector. The two wavelengths, the 660 nm (red) and the 925 nm (infrared) one, emitted by LEDs, cross the tissue and are picked up by the photodetector. The signal is then taken over by a microprocessor, which uses only the pulsatile signs for the calculation of oxygen saturation. The transmitted light is converted by a digital display, as either figures or as a pletismogram, for showing both oxygen saturation and pulse ratio. The instrument requires no heating or sterilization, no previous calibration, while the age of the patient and its physical condition do not influence the results. [15]

In dental medicine, several researchers used a pulse oximeter for detecting the state of pulp vitality, quite different results being attained; the final conclusion was that the values recorded for the frontal maxillary group are real and consistent, which shows that pulse oximetry is an efficient method for pulp vitality testing. [14]

Nowadays, no special pulse oximeter sensor, applicable in dental medicine, is available in Romania, even if several experimental models, representing adaptations of sensors (some of them even patented) are now used worldwide [16], while a commercial version is on the way. A pulse oximeter sensor applicable in dental medicine should meet the following conditions: * The sensor should be adapted to the shape, size and anatomical contour of the tooth;

* The emitting sensor and the photo receiver should be placed in parallel position, so that the whole light emitted by the diode sensor will be picked up by the photo receiving one;

* The oximeter device applied on the tooth should be kept steadfast, to assure correct measurements [14].

The purpose of the study was to analyze pulp vascularization at the level of permanent maxillary incisors and canines, registering the values of pulp oxygen saturation with a specially adapted pulse oximeter, and to evaluate its efficiency for the determination of pulp vitality.

MATERIALS AND METHOD

The study was performed on a group of 120 teeth, central and lateral maxillary incisors and canines, in patients with ages between 20 and 40 years, from the Endodontic Clinics - Faculty of Dental Medicine, Constanta.

The criteria for teeth selection were:

- a good periodontal status,

- no apical radiological modifications,

- no coronary reconstructions or enamel fissures.

Of special interest were the teeth demonstrating colour modifications without an obvious cause (obturations, endodontic treatments or old traumatisms). The teeth were evaluated clinically, radiologically and also by pulse oximetry, and the degree of pulp vitality was determined.

The control group was formed of 40 known non-vital incisors and canines with correct radicular obturations, on which the presence or absence of pulp vascularization was evaluated with a pulse oximeter.

The recordings made on a pulse oximeter with the sensor placed at the index of the right hand permitted to compare the Sa02 values from pulp blood with the values determined in the systemic blood. The pulse ratio was taken as a reference constant for all determinations.

To record the degree of sanguine oxygenation at teeth level, a sensor for pulse oximeter NT - measuring the Sa02 in blood from 0% to 100%, with an error interval of 2% - was employed. The sensor, modified for its application at teeth level, its shape and size corresponding to the dimensions of the teeth (4 mm length and 5 mm width), was kept steadfast by means of a specially designed support.

The same sensor was also employed for measuring the extent of sanguine oxygenation at the level of patient's finger. The tested equipment was a portable NT 1 Pulse Oximeter (Newtech, INC.) (Fig. 1)

WORKING METHOD

In a first stage, the values of Sa02 and of pulse in the systemic blood were measured by placing the sensor of the pulse oximeter at the level of the patient's right hand (Fig. 2), after which - employing the same sensor - the same values were determined at the level of the frontal teeth. (Fig. 3) The sensor, especially adapted to the teeth, permitted a parallel positioning of the emitting diode with the photo receiver, so that the whole light emitted by the diode sensor should be picked up by the photo receiver sensor.

The emitting diode was applied on the palatal side of the teeth, and the receiving one - at the level of the vestibular side, in the mean half of the crown. The values were registered 30 sec after application of the sensor on the tooth.

RESULTS AND DISCUSSION

The analysis group included 120 frontal maxillary teeth, in patients with ages between 20 and 40 years. The mean Sa02 value in pulp blood, for the central superior incisor, was of 83.30%, for the lateral superior incisor - of 78.51%, and for the superior canine - of 84.56%. The mean value of Sa02 in arterial blood, registered at finger level, was of 97%. In the case of non-vital teeth, the Sa02 value was 0. The mean pulse value registered at teeth level was of 70.56 beatings/ min and, at finger level, of 70.88 beatings/ min. The Sa02 values recorded in the present study are comparable with those obtained by other researches. (Table 1)

Statistical analysis made use of Pearson parameter, which permitted a correlation between the Sa02 values at tooth and, respectively, finger level, as well as a correlation between the pulse registered at finger level and the one recorded with the pulse oximeter, at tooth level. The correlation between the pulse recorded at tooth and, respectively, finger level was of 0.85, which means a very good correlation, very similar between the two values. For the group under investigation, Pearson analysis also showed a 0.072 value between the Sa02 value at pulp level and the value of oxygen saturation at the level of hand finger, which is a weak correlation.

Numerous investigators analyzed the efficiency of using a pulse oximeter device in endodonty, some of them comparing this procedure with other methods for testing pulp sensitivity. For example, Smith et al. [16] showed that pulsoximetry may effectively detect the oxygen saturation on an in vitro dental model, while Schnettler and Wallace [17] evidenced the existence of a connection between the systemic and pulp saturation of oxygen, by means of an ear sensor modified for being used as a dental sensor, which they also recommended for testing pulp vitality. Kahan et al. [18] designed, constructed and tested a sensor for teeth employing the Biox 3740 oximeter. The authors showed that sanguine pulse at tooth level is synchronous with that at finger level, but not always. Their conclusion was that, in its present form, the device has no predictive diagnosis value. Gopikrishna et al. [14] adapted a pulse oximeter sensor with which they registered oxygen saturation on both vital and non- vital teeth, reaching the conclusion that pulse oximetry represents an efficient and objective method for the evaluation of pulp vitality, mainly if considering the limitations of the conventional tests.

In another study, Gopikrishna, Tinagupta et al. [19] compared the recordings made with a sensor adapted by the pulse oximeter and those obtained through tests of thermal and electrical vitality. The sensitivity of the pulse oximeter was of 100%, of the tests performed at cold - of 81%, and that of the electrical ones - of 71 % (as known, sensitivity indicates the ability of the test of demonstrating the presence of the disease in the patients suffering from it).

The results of the present study showed that the modified sensor of the pulse oximeter could detect - through the enamel and dentin levels - different levels of Sa02 in the pulp blood of the vital teeth and values of 0% Sa02 in the non- vital ones, demonstrating - as other studies also did - that the pulse oximeter is an efficient instrument for the establishment of a correct endodontic diagnosis.

Due to the reproducibility of the oxygen concentration values recorded by the pulse oximeter, they acquire an immediate clinical value in the case of traumatized teeth, while having a special importance, too, in patients' monitorization after conservative treatments, or for checking up the vitality of some vital dies. A comparison made between the first and the last registrations may promptly evidence any tendency of dental pulp necrosis.

CONCLUSIONS

- the pulse oximeter with modified sensor represents an efficient instrument for the determination of pulp vitality;

- analysis of pulp vascularization at tooth level is a better method for the investigation of pulp vitality, comparatively with testing of pulp inervation, which - as a function of patient's sensitivity - may have several variables;

- pulsoximetry provides an efficient method for subsequent researches in patients with general pathologies, such as, for example, diabetes, when the general vascular modifications may impact upon terminal pulp vascularization.

References

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