Comparison of the reliability of laser Doppler ﬂowmetry,

Comparison of the reliability of laser Doppler flowmetry,

pulse oximetry and electric pulp tester in assessing the

pulp vitality of human teeth

H. KARAYILMAZ & Z. KIRZIOGLU Faculty of Dentistry, Department of Pedodontics, Suleyman Demirel University,

Isparta, Turkiye

SUMMARY This study was designed to evaluate and

compare the reliability of laser Doppler flowmetry

(LDF), pulse oximetry (PO) and electric pulp tester

(EPT) for assessing the pulpal status as a vitality test

method by calculating their sensitivity, specificity

and predictive values. Data were collected from

59 pairs of maxillary anterior teeth (38 pairs of

central, 21 pairs of lateral incisors) in 51 patients

(range 12–18 years, mean age 14Æ6 � 1Æ73 years, 28

women, 23 men). The teeth with complete end-

odontic fillings constituted the study group, and the

healthy, contralateral teeth of the same patients

were constituted the control group. The calculated

sensitivity was 0Æ915 for the EPT and 0Æ813 for the

PO. And the specificity of EPT was 0Æ881 and PO was

0Æ949. The difference between the LDF values

obtained from the study, and control group was

statistically significant (P = 0Æ0001). The findings of

this study indicated that LDF can reliably discrim-

inate the vitality of the teeth with a sensitivity and

specificity of 1Æ0 for this sample. Laser Doppler

flowmetry was found to be a more reliable and

effective method than PO and EPT of assessing the

pulpal status of human teeth.

KEYWORDS: laser Doppler flowmetry, pulse oxime-

try, pulp vitality testing, pulpal blood flow

Accepted for publication 26 August 2010

Introduction

The vitality assessment of teeth is a critical diagnostic

procedure in the practice of dentistry. But it is compli-

cated by the fact that the dental pulp is enclosed within

calcified tissue. As the pulp tissue cannot be directly

inspected, the dentist has to use indirect methods (1).

However, the most widely used traditional pulp vitality

test methods, such as electric pulp testers (EPT) and

thermal stimulus, determine only the pulp sensitivity to

the stimuli used but given no direct indication of blood

flow within the pulp. Consequently, false-positive or

false-negative responses can be obtained from traumat-

ically injured teeth or from immature teeth (2, 3).

Furthermore, each of these subjective methods is

depends on the patient’s perceived response to a

stimulus, as well as the dentist’s interpretation of that

response (4). Also, these methods have a potential

to produce an unpleasant and occasionally painful

sensations. Thus, the reliability of these methods can

vary, and they are of limited use with children (5).

Therefore, new, improved diagnostic methods are

needed to assist in the diagnosis of teeth with pulpal

pathosis and consequently to aid in their correct

treatment. Pulse oximetry (PO) and laser Doppler

flowmetry (LDF) are non-invasive methods for assess-

ing blood flow in microvascular systems, which have

been recently introduced as a new method to diagnose

pulp vitality in human teeth.

The PO measurement technique

Pulse oximetry is a relatively recent advancement in

non-invasive monitoring of oxygen saturation (SaO2) of

the blood and pulse rate of the patient. It is effectively

and routinely used in medical applications through the

use of finger, toe, ear and foot probes. Its wide acceptance

in the medical field results from its ease of application

ª 2010 Blackwell Publishing Ltd doi: 10.1111/j.1365-2842.2010.02160.x

Journal of Oral Rehabilitation 2011 38; 340–347

J o u r n a l o f Oral Rehabilitation

and its capability of providing vital information about the

patient’s status (6, 7). The principles of PO are based on a

modification of Beer’s law and the absorbance charac-

teristics of haemoglobin in the red and infrared range.

The PO probe consists from a photo-detector and two

light-emitting diodes (LED). One of the LED transmits

red light (640 nm), and the other transmits infrared light

(960 nm) to the vascular tissue. Oxygenated and deox-

ygenated haemoglobin absorbs different amount of red

and infrared light. The pulsate change in the blood

volume causes periodic changes in the amount of red and

infrared light absorbed by the vascular tissue before

reaching the photo-detector, and PO uses this informa-

tion to calculate the pulse rate and SaO2 (5–7).

The LDF measurement technique

Laser Doppler flowmetry is non-invasive electro-optical

technique, which has been shown to have potential as a

method of assessing the vitality of teeth by detecting the

presence or absence of a pulpal blood flow (PBF) (8, 9).

The LDF technique utilises a beam of infrared (780–

820 nm) or near infrared (632Æ8 nm) light that is

directed to the tissue by optical fibres within a special

designed probe. Monochromatic laser light is transmit-

ted through the crown of the tooth to the dental pulp

via the probe, and it is scattered by moving red blood

cells and stationary tissue cells. Photons which are

reflected from the moving red blood cells are scattered

and frequency shifted according to the Doppler princi-

ple. Photons that interact with stationary tissue cells are

scattered but not Doppler shifted. The proportion

of shifted to unshifted light within the reflected light

gives a semi-quantitative measurement of blood flow

through the tissue and recorded as a voltage output

from the LDF (8–11). The measured voltage was

linearly related to the PBF and expressed in arbitrary

perfusion units (PU) (1 PU = 10 mV) in accordance

with general consensus (European Laser Doppler Users’

Groups, 1992) (8–14).

This study was designed to evaluate and compare the

reliability of LDF, PO and EPT for assessing the pulpal

status as a vitality test method by calculating their

sensitivity, specificity, and predictive values.

Materials and methods

The study sample was constituted from the archives of

the patients who were attending to the Department

of Pedodontics, Suleyman Demirel University, Faculty

of Dentistry. The participants selected for the study had

one or two endodontically treated (at least 1 year

before) maxillary incisor teeth; the contralateral of the

same teeth was healthy. Also, the participants were

non-smokers and had no history of systemic vascular or

cardiovascular disease or any evidence of hypertension,

and none of them were taking any medication. The

research ethical committee of Suleyman Demirel Uni-

versity, Faculty of Medicine, approved the study

(09.03.2006-02 ⁄ 17). The experimental purpose and

methodology were explained to the patients or their

parents ⁄ carers, and an informed consent was obtained.

Data were collected from 59 pairs of maxillary

anterior teeth (38 pairs of central, 21 pairs of lateral

incisors) in 51 patients (range 12–18 years, mean age

14Æ6 � 1Æ73 years, 28 women, 23 men) (Fig. 1). The

teeth with complete endodontic fillings constituted

the study group, and the healthy, contralateral teeth

of the same patients were constituted the control group.

A full history was taken, and clinical and radiographical

examinations of patients were carried out by the same

examiner in accordance with normal clinical practice.

All the teeth selected for the study had clinically intact

crowns or small restorations, which were located in

areas away from cervical region, where the vitality tests

were performed. Sample criteria required teeth to be

free of caries, developmental defects, discolouration or

root resorption.

Patients were warned to abstain from hot or cold

foods and beverages for at least 2 h before attending. All

measurements were performed in a temperature-con-

trolled room (24 � 1�C) using the same unit and in

keeping the same position. The patients rested for

10 min in the unit before the measurements.

Fig. 1. The distribution of 51 participants according to age and

gender.

C O M P A R I S O N O F T H E R E L I A B I L I T Y O F L D F , P O A N D E P T 341

ª 2010 Blackwell Publishing Ltd

The PO apparatus

A commercially available ‘Life Scope I, Multiparameter

Bedside Monitor’ (Model BSM-2301K*) and a modified

infant probe were used to record SaO2 levels. Special

probe holders designed taking into consideration the

morphology of the maxillary incisors to hold the

modified probe on the tooth. Stainless steel clips and

rubber dam clamps were used as the base for the

holders. The tapes enclosing the LEDs and photo-

detector of the infant probe were removed and attached

to the holder in parallel to each other (Figs 2 and 3).

The PO measurement procedures

The probe was positioned on the cervical region of the

crown of the tooth using probe holder. So that light

would travel from the facial to the palatinal side

through the middle of the crown. Pulse oximetry

values were recorded after 45 s of monitoring each of

the teeth. If there was no response at the end of the

measurement period, the PO values of the tooth were

recorded as negative (Fig. 4).

The LDF apparatus

The PBF of the teeth was measured by a commercially

available LDF device (BLF21A†; wavelength 780 nm)

and a custom made (ext. diam.; 1Æ5 mm, two fibre in

0Æ2 mm diam., centres 0Æ5 mm apart) dental probe in

this study (Figs 5 and 6).

The LDF measurement procedure

Silicon-impression-based personal splints were prepared

to ensure accurate and reproducible positioning of the

probe on the tooth for each of the participants. On the

labial side of the splints, holes 2 mm above the gingival

margins were drilled to insert and to fix the probe. The

probe was held perpendicular to the surface of the crown

2 mm from the gingival margin using these splints.

Evaluation took 45 s for each tooth, and data were

collected by a PC connected to the LDF device while

maintaining a real-time display on the monitor. The

20 s of the data, which was optimum part of the

measurement, were selected for the study by a special

software package (Windaq ver. 2.36‡), and the average

Fig. 2. The appearance of modified infant probe.

Fig. 4. The placement the modified infant probe with probe

holder on the tooth and the measurement procedure.Fig. 3. The appearance of special designed probe holder.

*Nihon Kohden Corp., Tokyo, Japan.

†Transonic Systems Inc., Ithaca, NY, USA.‡DATAQ Instruments Inc., Akron, OH, USA.

H . K A R A Y I L M A Z & Z . K I R Z I O G L U342


PBF of the teeth was calculated in PU by the same

software (Figs 7 and 8).

The EPT measurement procedures

A conventional EPT (Pulptester, Model PT-20§) was

used for EPT, and the response was recorded as positive

if the teeth tested showed any response on the

aforementioned scale or negative if there was no

response.

Other measurements

The following measurements were performed to exam-

ine the effects of the values obtained from the teeth by

PO and LDF:

1 The systemic SaO2 level and pulse rate of the patients

were measured by PO device from the index finger

using a finger probe.

2 Systolic and diastolic arterial blood pressures were

also measured and recorded.

Statistical analyses (paired t test, Mann–Whitney U,

Pearson’s correlation) were performed using SPSS (Ver.

13.0¶) at P < 0Æ05 significance level. Also the sensitivity,

Fig. 5. The appearance of commer-

cially available laser Doppler flow-

metry.

Fig. 7. Silicon-impression-based personal splints were used to

ensure accurate and reproducible positioning of the probe on the

tooth.

Fig. 6. The appearance of device and a custom made dental probe

used in this study.

§Parkell Inc., Edgewood, NY, USA. ¶SPSS Inc., Chicago, IL, USA.



specificity, positive predictive value (PPV) and negative

predictive value (NPV) were calculated.

Results

Electric pulp tester identified 5 of the 59 teeth with

complete endodontic fillings as vital, while 54 as non-

vital. In control group consisted from the healthy,

contralateral tooth of the same patient, 52 teeth were

identified as vital and 7 as non-vital with EPT.

The 59 tooth with complete endodontic fillings, 11

teeth gave positive response, whereas 48 teeth

responded negatively to the PO. But in the control

group, 56 gave a positive response, whereas three

responded negatively.

The average PO and LDF values obtained from the

healthy, contralateral teeth and teeth with complete

endodontic fillings have been summarised in Table 1.

In general, it was determined that approximately a

1 ⁄ 10 ratio between the PBF values measured by LDF

Fig. 8. The display of the waveform that synchronised with heart beat.

Table 1. The distribution of laser Doppler flowmetry (LDF) and pulse oximetry (PO) values obtained from healthy, contralateral teeth

and teeth with complete endodontic fillings

Central incisors Lateral incisors Total

n Min. Max. Mean � s.d. n Min. Max. Mean � s.d. n Min. Max. Mean � s.d.

Healthy, contralateral teeth

LDF (PU) 38 5Æ84 18Æ17 10Æ43 � 3Æ25 21 6Æ23 18Æ11 12Æ11 � 3Æ71 59 5Æ84 18Æ17 11Æ02 � 3Æ48

PO (%) 38 81 93 86Æ32 � 3Æ33 21 80 92 87Æ47 � 3Æ06 59 80 93 86Æ71 � 3Æ26

Teeth with complete endodontic fillings

LDF (PU) 38 0Æ13 2Æ21 0Æ99 � 0Æ54 21 0Æ8 2Æ35 1Æ29 � 0Æ66 59 0Æ13 2Æ35 1Æ09 � 0Æ60

PO (%) 38 00 79 17Æ5 � 31Æ86 21 00 76 6Æ95 � 21Æ97 59 00 79 13Æ74 � 28Æ99

PU, perfusion unit.



from the tooth with complete endodontic fillings and

the healthy contralateral tooth of the same patient. The

difference between the study and the control group was

statistically significant (P = 0Æ0001). Thereupon, it was

deduced that LDF can successfully differentiate the

vitality of the teeth inspected in the study.

On the basis of these findings, the sensitivity, spec-

ificity and predictive values were calculated for each of

the method. The sensitivity and the specificity of EPT

were 0Æ915 and 0Æ881, respectively. But for the PO, the

sensitivity was 0Æ813 and the specificity was 0Æ949. The

calculated PPV and NPV for EPT were 0Æ885 and 0Æ912,

respectively. For the PO, the PPV was 0Æ941 and the

NPV was 0Æ835.

Under the findings from vitality assessment using

LDF in this study would give LDF a sensitivity and

specificity of 1Æ0 in discrimination between teeth with

complete endodontic fillings and healthy, contralateral

tooth of the patients.

In addition to these findings, statistically significant

positive correlations were observed between the LDF

values obtained from the study and the control group

(r = 0Æ59, P = 0Æ0001) and between PO and LDF values

obtained from healthy, contralateral teeth (r = 0Æ32

P = 0Æ016).

Although the PO values obtained from the healthy,

contralateral teeth were showed a positive correlations

only with pulse rate (r = 0Æ28 P = 0Æ034) of the patients,

the LDF values were showed statistically significant

correlations with the systemic SaO2 levels (r = 0Æ34

P = 0Æ009) and pulse rate (r = 0Æ30 P = 0Æ019) of the

patients. The gender and arterial blood pressures of the

patients were not significant.

Discussion

The perfect diagnostic test would always be positive in

the presence of disease and negative in the absence of

disease. The extent to which a test correctly classifies

patients defines its accuracy. The concepts of sensitiv-

ity, specificity, PPV and NPV have been developed to

characterise test accuracy and to compute the benefits

of test usage (15). Sensitivity denotes the ability of a

test to detect disease in patients who actually have the

disease. Conversely, specificity describes the ability of

a test to detect the absence of disease. The ideal pulp

test method would have sensitivity and specificity of

1Æ0. The PPV is the probability that a positive test

result actually represents a disease-positive person.

Negative predictive value is the probability that a

person with a negative test result is actually free of

disease (15).

This study was designed to evaluate and compare the

reliability of EPT, PO and LDF as a vitality test method

by calculating their sensitivity, specificity and predictive

values. To our knowledge, this is the first study

evaluating and comparing the reliability of EPT, PO

and LDF together in same study as a vitality test

method.

The calculated sensitivity and specificity of PO and

EPT in our study denoted that 91% of the teeth with

complete endodontic fillings were identified as non-

vital by EPT, while 81% of these teeth were identified

as non-vital by PO. Likewise, 88% of the healthy

contralateral teeth were identified as vital by EPT,

while 95% of these teeth were identified as vital by

PO. Thus, the calculated PPV and NPV denoted that

there was a probability of 88% that no sensitive

reaction represented a root-canal filled tooth, and a

there was a probability of 91% that sensitive reaction

represented a healthy, vital tooth when EPT was used.

Likewise, the probability that no sensitive reaction

represented a root-canal filled tooth was 94%, while

the probability that a sensitive reaction represented a

healthy, vital tooth was 83% with PO. These results

imply that the ability of PO in determining the vitality

of healthy teeth was found better than EPT, but PO

was found insufficient in determining the vitality of

teeth with complete endodontic fillings. The reasons

for this could be that the scattering of the light

(transmitted from PO) from the composite restorations

of the root-canal-treated teeth to the adjacent tissues

(gingiva, etc.) and the physical limitations of PO.

Therefore, the efficacy of PO in teeth with composite

restorations that located in cervical region of the tooth

caused suspicion.

Although some of the studies had shown the effec-

tiveness and accuracy of PO in determining the PBF (5,

16–20), a few studies reported that the overall accuracy

of the commercially available PO instruments was

disappointing and, in its present form, was not consid-

ered to have predictable diagnostic value in determin-

ing the PBF of the teeth (21–23).

Recently, Gopikrishna et al. (19) evaluated the effi-

cacy of PO in comparison with the conventional pulp

vitality tests. They were reported that the sensitivity

and the specificity of PO were 1Æ00 and 0Æ95, respec-

tively. Although specificity of PO reported in both of



the studies was similar, the sensitivity of PO reported in

our study groups was low. It was considered that the

disagreements arise from the differences in study

groups selected and the methods preferred for the

studies. Single-rooted incisors requiring endodontic

therapy were selected for their study, but the teeth

with complete endodontic fillings constituted the study

group and the healthy, contralateral teeth of the same

patients constituted the control group in our study.

In view of these results, it was determined that LDF

can reliably discriminate between vital and non-vital

dental pulps of maxillary anterior teeth with a sensi-

tivity and specificity of 1Æ0 for this sample, and LDF was

found to be a more reliable method than PO and EPT.

There were a number of studies in the literature that

have proved these results (8, 10–14, 24–26). Of these

studies, Evans et al. (12) reported in accordance with

our results, the sensitivity and specificity of LDF were

1Æ0 in their study. Using LDF as a vitality test method, it

appeared that we could diagnose pulpal necrosis more

accurately than with conventional test methods. This

may lead to less pain and discomfort for the patient, less

cost and earlier treatment. However, despite its advan-

tages, LDF still has a number of specifically technical

limitations (27, 28). These include, motion artefact

noise, multiple Doppler shifting, variations in instru-

ment and probe specifications, lack of quantitative units

and knowledge of depth of measurements, lack of the

knowledge of normal PBF values of the healthy teeth,

environmental effects to the measurements and high

costs of the instrument.

Conclusion

Laser Doppler flowmetry was found to be a more

reliable and effective method than PO and EPT for

assessing the pulpal status of human teeth especially in

paediatric patients where patient co-operation and

incomplete pulp innervations reduce the effectiveness

and reliability of conventional test methods. However,

the improvement of the LDF method and apparatus

with further researches is indicated to become a

valuable clinical diagnostic tool in practice of dentistry.

Acknowledgment

This study was supported by the scientific research

grant given by Suleyman Demirel University (SDUBAP,

1212-D-05).

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Correspondence: Dr Huseyin Karayilmaz, Suleyman Demirel Univers-

itesi, Dis Hekimligi Fakultesi, Pedodonti Anabilim Dalı, Cunur

Kampusu, Isparta, Turkiye. E-mail: [email protected]



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