wavelen spectrop

diagnosti est of the pulp c

contents
Roni Nissan, DMD,a Martin Trope, DMD,b Cheng-Duo Zhang, BS,c and
Britton Chance, PhD,d Philadelphia, Pa.

DEPARTMENT OF ENDODONTOLOGY, TEMPLE UNIVERSITY SCHOOL OF DENTISTRY, AND

DEPARTMENT OF BIOCHEMISTRY AND BIOPHYSICS, UNIVERSITY OF PENNSYLVANIA.

The purpose of this in vitro study was to determine the feasibility of using dual wavelength
spectrophotometry to identify teeth with pulp chambers that are either empty, filled with fixed pulp
tissue, or filled with oxygenated blood. In phase I of the experiment, a human third molar was
prepared so that its pulp space could be filled with oxygenated blood and later emptied. In phase II,
the lower jaw of a beagle dog was removed and placed in formalin, thereby fixing the pulps of the
teeth. The pulp of the right canine was removed via an apical approach, and attachments were
placed in a similar position to those on the human tooth, to allow filling and emptying of the pulp
space. Cavit was placed over the exposed fixed pulp in the left canine. Ten readings, which were
separated by light source and detector removal and replacement, were taken of the right canine
pulp space when it was empty or filled with oxygenated blood, or the left canine pulp space when it
was filled with fixed tissue. Distinct and reproducible changes were measured for pulp spaces filled
with air, tissue, or oxygenated blood. In phase Ill, simulated pulp testing on a dog tooth model was
performed. Blood was introduced into the root canal space, the chamber was rinsed with water and
replaced with air, according to a predetermined code. Spectrophotometer readings were recorded.
The identification of pulpal contents was correctly determined in all 20 of the predetermined
conditions. The findings indicate that continuous wave spectrophotometry may become a useful
pulp testing method.
(ORALSURG ORALMEDORALPATHOL~~~~;~~:§O~-~~)

S ensitivity testing is essential for the differential

diagnosisof pulpal disease.Current methods include
blood flow or determining the status of the blood sup-
ply to the pulp of the tooth has obvious advantages.
thermal and electrical pulp tests, percussion,and pal- Such a test would be an objective assessmentof the
pation. Thermal and electrical pulp tests are subjec- status of the pulpal blood circulation, a true indicator
tive. They test nerve responsesonly; thus false-posi- of pulp vitality.
tive and false-negative results are frequently ob- Past methods for testing pulpal blood circulation
tained.’ The unreliability of testing tooth pulp nerve have included the use of the following: radioactive
responsesis well documented.2-4Recording the pulpal substancesuch asxenon 133 washout5,6;radiolabeled
microspheres7;and laser Doppler flowmetry.*, 9 The
aAssistant Professor, Department of Endodontology, Temple Uni-
use of radioactive materials is restricted on humans.
versity School of Dentistry. Laser Doppler flowmeter technology is expensive and
bProfessor, Department of Endodontology, Temple University may not be practical for clinical use in the average
School of Dentistry. dental office.
CResearch Associate, Department of Biochemistry and Biophysics, Dual wavelength spectrophotometry is a method
University of Pennsylvania.
dProfessor Emeritus, Department of Biochemistry and Biophysics,
that has previously been considered as a diagnostic
University of Pennsylvania. tool to determine pulp status.‘O, l1 Pulse oximetry is a
7/15/40192 method basedon dual wavelength spectrophotometry
Volume 74 Tests of pulp chamber contents 509
Number 4

technology. This technique was developed by Milli-

kan12 and improved by Wood and Geraci.13 Pulse
oximetry has been tested for the detection of blood
flow in the pulp with mixed results.‘O>i1 However,
pulse oximetry could not be expected to be useful. for
blood flow detection in the tooth pulp because it
requires a pulsatile blo’od flow.14~t5 The presence of
arterioles, rather than arteries, in the pulp and insu-
lation by the surrounding dentin and enamel are ob-
staclesto the detection of the pulse. Chancel6 has de-
veloped the technique of continuous dual wavelength
spectrophotometry that measures the oxygenation
change of the blood in the capillary bed rather than
in the supply vessels. Because this technique is not
dependent on the pulseof the vessels,it might be more
applicable to the study of tooth pulp blood flow than
pulse oximetry.
The purpose of this preliminary study was to
determine, in vitro, l.he feasibility of the use of
continuous wave spectrophotometry to identify teeth
with pulp chambers that are either empty, filled
with fixed pulp tissue, or filled with oxygenated
blood.

MATERIAL AND METHODS

Fig. 1. Human tooth model. A, 18-gaugeneedleis ce-
The continuous dual wavelength spectrophotome- mentedinto holesin tooth. Teflon tubes are attached to
ter (Runman, NIM, Inc., Philadelphia, Pa.) used in needleto allow liquid to enter and leave pulp space.B,
this study produces light at two wavelengths only- Crown is firmly held in place by two screwsand piece of
160 nm and 850 nm. When the light absorption at 760 wood.Pulp chamberopeningis sealedby pressingit against
nm is subtracted from that at 850 nm, the difference flat surface covered with three layers of rubber dam.
represents the net absaorptionas a result of a change Fiberopticlight guidesanddetectorsare heldoppositeeach
in oxygenation. When the light absorption at 760 nm other buccally and longitudinally.
is added to that at 850 nm, absorption as a result of
oxygenation is canceled and any observed change re-
surfaces of the tooth were drilled into the chamber
sults from a change in volume or concentration. The
with a No. 2 round bur. Two 10 mm portions of an 18-
level of blood oxygenation being measured (760 nm
gauge needle were cemented into the prepared holes
minus 850 nm), and the volume of the blood (760 nm
with a light-cured resin bonding system (Silux Plus
plus 850 nm) are then translated into an electrical
and Scotchbond 2, 3M, St. Paul, Minn.). After the
current (+_ 1000 mV maximum) that is fed into a lin-
resin had fully set, a Teflon tube was attached to each
ear chart recorder that showsthe two channels-vol-
metal needle. The Teflon tubes permitted liquid to be
ume and oxygenation-being measured.
introduced into and out of the pulp chamber (Fig. 1).
This study included three phases: human tooth
The pulp chamber was sealedby firmly clamping the
model, dog tooth model, and simulated pulp testing on
tooth crown onto a piece of wood covered with rubber
dog teeth.
dam. Two fiberoptic light guides attached to a dual
wavelength spectrophotometer were applied and fixed
PHASE I: Human Tooth Model
oppositeeach other buccally and lingually (Fig. 1, B).
An extracted, impacted, human third molar was The machine was calibrated for the air-filled pulp
prepared for use in the study. The root was removed chamber asfollows: a baseline of 0 * 5 mV, 500 mV
with a diamond disk 2 mm below the cementoenamel full scalefor the oxygenation channel, and 0 + 5 mV,
junction. The roof of the pulp chamber was flattened 200 mV full scalefor the volume channel. Oxygenated
internally to remove any irregularities of the: pulp human blood was then introduced into the pulp
horns that might interfere with blood flow into and out chamber and a measurementtaken. The chamber was
of the chamber. Holes on the mesial and distal cleared by injecting 10 ml of a 2.5% solution of sodium
510 Nissan, Trope, and Zhang ORALSURGORALMED ORALPATHOL
October 1992

A). Metal attachments were soldered onto a 00 clamp

(Ivory Miles Inc., St. Louis, MO.). When the clamp
was placed on the tooth, this procedure permitted the
fiberoptic light guides to be passed through the
attachments and fixed on opposite sides of the tooth
(Fig. 2, 3).
The machine was calibrated for an air-filled pulp
chamber as follows: a baseline of 0 t 5 mV 500 mV
full scale for the oxygenation channel, and 0 I 5 mV
200 mV full scale for the volume channel. After cal-
ibration of the right canine with an empty pulp
chamber, 10 alternate readings were taken from the
tooth with an empty pulp chamber and from the tooth
with the pulp chamber filled with oxygenated blood.
The clamp and light guides were removed and then
replaced between each reading. The right canine was
then filled with blood, and the machine was calibrated
to read it as 0 baseline. The right canine then was
emptied, and reading was taken from the right and the
left canines with fixed pulp tissue alternating 10 times.
The reproducibility and differences of the readings for
the different pulpal states were then measured and
compared. The fixed pulp tissue in the left canine was
now removed, and metal tubes connected. Ten ne-w
readings were taken and compared with those of the
Fig. 2. Dog tooth model. ii, Right canine prepared with opposite canine.
two metal and Teflon tubes that enter empty pulp space
from apical approach. B, Jaw is firmly held by two screws hase ill: Simulated Pulp Testing on Dog Tooth
and a piece of wood. Ivory 00 clamp with metal attach- Model
ments fixes fiberoptic light guides on opposite side of tooth. Two investigators participated in this phase. Inves-
tigator A introduced blood, rinsed the dog tooth with
water and replaced it with air alternating according
hypochlorite to dissolve any remaining blood or to a predetermined code. Investigator B read the
debris, followed by tap water. The chamber was then spectrophotometer and the chart recorder to deter-
dried by continuous air injection. A new measurement mine pulp chamber contents.
of the air-filled chamber was then taken. After each A cardboard barrier was constructed so that the
reading, the machine was turned off, and the fiberop- investigator who read the linear chart recorder could
tic light guides were removed from the tooth. After an not see the dog jaw and the contents of the syringe
interval of 5 minutes, the light guides were replaced used to fill the pulp chamber. The investigator who
on the tooth, and the test was repeated. The above read the linear chart recorder was then asked to name
protocol was repeated 10 times. the pulp chamber contents of the tested tooth accord-
ing to the readings obtained. Twenty readings, sepa-
PHASE II: Dog Tooth Model rated by removal and replacement of the clamp and
The lower jaw of a beagle dog that had been killed light guides, were made. Pulpal contents w-ere changed
in another study was dissected on the distal surface of by investigator A according to a prepared order. Af-
both canine teeth and fixed in a 10% buffered forma- ter each change, investigator B selected and recorded
lin solution. The apical one third of the canine roots the pulp chamber contents according to experience
was removed, which afforded access to the pulp canal. from readings of the previous studies.
In the left canine, the fixed pulp was covered apically
with Cavit (ESPE, Seefeld/Oberbayren, Germany). RESULTS
Phase I: Human Tooth Model
In the right canine, all pulpal tissue was removed from
the crown and root with endodontic files, via an api- Examples of the linear chart readings are shown in
cal approach. Metal needles and Teflon tubes were Fig. 3. The recordings for a tooth filled with air were
fixed through the apex with resin to allow fluid to flow consistent for all 10 readings (0 mV I 5 mV>. When
into and out of the right canine, as in phase I (Fig. 2, biood was introduced into the chamber, a distinct and
Volume 74 Tests of pulp chamber contents 511
Number 4

BLOOD AIR BLOOD A I R

J l 32 mv
+3 7 mV

channel

WATER WATER

Fig. 3. Linear chart recording from human tooth model. Baseline of 0 f 5 mV was calibrated. When ox-
ygenated blood was introduced into pulp chamber, the readings varied from -40 mV to -75 mV whereas
for an air-filled chamber, the readings returned to the baseline value of 0 F 5 mV.

reproducible shift was seen. In the oxygenation chan- Left canine. The 10 readings obtained for the left ca-
nel, the reading with lblood was - 75 mV (k 5 mV). nine filled with fixed pulp tissue were - 100 mV f 10
In the volume channel, the reading was -40 mV (k 5 mV. They were consistent, reproducible, and different
mV). When tap water was introduced to wash out the from those obtained from the empty right canine,
blood, a shift to +35 mV ( f 5 mV) was registered. -387 mV (+- 10 mV). When the fixed tissue was re-
Introducing air resulted in a return to the baseline of moved from the pulp and metal tubes cemented api-
0 (+ 5 mV), indicating the presence of an empty tally, the reading for the left empty canine were sim-
tooth. ilar to that of the right canine with an empty pulp
space (Fig. 5).
Phase II: Dog Tooth Model
Phase III: Simulated Pulp Testing
Examples of linear chart recording readings are
shown in Fig. 4. Fig. 6 shows the representative list of pre-prepared
Right canine. As in phase I, a reproducible reading pulpal contents used by investigator A and the
was obtained with the empty pulp space. When blood recording values and pulpal content selection made by
was introduced into the pulp chamber, a distinct and investigator B. Air-filled tooth readings were 0 + 5
reproducible shift was seen. In the oxygenation chan- mV. Blood-filled tooth readings were - 150 mV +_ 10
nel, the readings with blood were 144 mV ( + 10 mV). mV. The selection of pulpal contents was correctly
In the volume channel, the readings were -80 mV verified for all 20 predetermined conditions.
( +- 5 mV). After the chamber was washed and air in-
DISCUSSION
troduced, a return to the base line of 0 + 5 mV was
registered. The readings for blood-filled dog canine The continuous dual wavelength spectrophotome-
were different from those obtained from the blood- ter used in this study was designed to noninvasively
filled human tooth model of phase I. Again, as in monitor oxygenation changes in muscle. The instru-
phase I, the readings changed consistently and repro- ment detects the presence or absence of oxygenated
ducibly. blood at 760 nm and 850 nm. The blood volume or
512 Nissan, Trope, and Zhang ORAL SLRC~QRAL MEDORALPATHOL
October 1992

WATER WATER

Fig. 4. Linear chart recordingfrom dog’sright canine.Distinct andreproduciblechangessimilarto human

tooth model(Fig. 3) were seen when pulp wasfilled with oxygenatedbloodor air.

blood concentration channel (760 nm plus 850 nm) is other hand, Schnettler and Wallacei’ reported a cor-
arranged to respond linearly to the increase in light relation between blood oxygenation levels in the fin-
absorption. The oxygenation channel (760 nm minus ger and those in the vital tooth pulp. However, they
850 nm) sensesthe oxygenated blood becauseof its compared these readingswith teeth previously treated
greater absorption at 850 nm as compared with 760 endodontically and restored, that is, a structure witb
nm. Thus the presenceof oxygenated blood is detected different light absorption properties. The subtle dif-
by both of thesechannels. Even though the instrument ference in light absorption in a vital (pulsatile) versus
was not specifically designed for dental use, it was nonvital (nonpulsatile) tooth pulp surrounded by
easy to use and might be developed as a pulp tester. similarly light-absorbing enamel and dentin was not
A major advantage is that it usesa visible light that tested.
is widely used in dentistry. This light is filtered to a In the present experiment, continuous wave spec-
near infrared range (760 nm to 850 nm) and is guided trophotometry was used. This measuresblood oxy-
to the tooth by fiberoptics. Thus, unlike laser light, genation change within the capillary bed of a tissue
added eye protection is unnecessary for patient and and thus is not dependent on a pulsatile blood flow.
operator. The test is noninvasive, does not rely on a This study was designedto test the reproducibility
subjective patient response,and therefore yields ob- of readings obtained by the continuous wave spectro-
jective results. The instrument is small, portable, and photometer and its potential to determine the status
relatively inexpensive. It should be suitable for use in of a tooth with a vital, nonvital, or ischemically
a private dental office. necrosed pulp. When the light guides were removed
The dependenceon a pulsatile blood flow appears and replaced, the readings were within 6% of each
to be a major disadvantage of the useof the pulseoxi- other, indicating good reproducibility. In phase I of
meter. Schmitt et al.iO were unable to measure oxy- the experiment, the measurements from an empty
gen saturation of blood with the use of a standard pulp chamber were distinctly different from those re-
pulse oximetry technique on molars in vitro. On the corded when the pulp spacewasfilled with oxygenated
Volume 74 Tests of pulp chamber contents 513
Number 4

Canine - I 1 I 1

-3a7mv -382mV
-380 mu -377rnV

-230mV -231 mV
-221 mV -214mV
- -

-110mv
-100 mV -

-45 mV
-40 mv

Omv Base C-
line P-
\
h-

I I
RiQh t
canline
Right
canine
Lefi
tissue
and
canine

metal
removed
tubes
with empty
connected
blood

Fig. 5. Lmear chart recording from dog’s right canine (empty) and left canine (fixed tissue). Baseline 0 (+ 5
mV) was calibrated with right canine filled with blood. Note, when emptied the right canine showed a dis-
tinct shift in reading (-387 mV; -230 mV). Readings for left canine (fixed tissue -100 mV; -40 mV), was
different from those of both blood-filled and empty right canine. When tissue was removed from left canine,
readings similar to those of empty right canine were seen.

?ltltlE~lllEl
*li r blood air air blood air blood blood
Cllf f111
1111 cnll1ttt1s

-150mV
-148mV

- 3 mV

I-
*lOmV

-Y
--

lllYttllnAlln
B SflfCTIII * ai, al r air air
blood btood blood blood
I! rvtr

Fig. 6. Simulated pulp testing. All predetermined pulp conditions prepared by investigator A (air-filled or
blood-filled teeth) were accurately selected by investigator B.
514 Nissan, Trope, and Zhang ORAL SURG ORAL MED ORAL Parno~
October 1992

blood. This reproducible test was repeated in phase II REFERENCES

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dog tooth models showed reproducible changes when 2. Fuss Z, Trowbridge HO, Bender IB, Rickoff B. Assessment of
the pulp spaces were empty. These findings were dif- reliability of electrical and thermal pulp testing agent. J En-
dod 1986;12:301-5.
ferent from those obtained from pulp spaces filled 3. Stark MM, Kempler D, Pelzner RB, Rosenfeld J, Leung RL,
with oxygenated blood. However, the readings for Mintatos S. Rationalization of electric pulp-testing methods.
human and dog teeth were distinctly different from ORAL SURF ORAL MED ORAL PATHOL 1977;43:598-606.
4. Chambers IG. The role and methods of pulp testing in oral di-
each other. Thus dentin thickness and pulp space size agnosis: a review. Int Endod J 1982;15:1-15.
appear to play a role in the passage of light through 5. Trope M, Jaggi J, Barnett F, Tronstad L. Vitality testing of
the tooth. The results suggest the possibility to differ- teeth with a radiation probe using 133 xenon radioisotope. En-
dod Dent Traumatol 1986;2:215-8.
entiate a pulp space that contains an ischemically ne- 6. Kim S, Schuessler G, Chien S. Measurement of blood flow in
crosed pulp from an empty pulp space or a pulp space the dental pulp of dogs with the Xe-133 washout method. Arch
filled with oxygenated tissue. Oral Biol 1983;28:501-5.
7. Kim S, Dorscher-Kim J, Liu M-T, Trowbridge HO. Biphasic
The spectrophotometer technology is not nerve de- pulp blood flow response to substance P in the dog as a mea-
pendent. Measurement of pulp oxygenation level de- sured with radiolabeled, microsphere injection method. Arch
pends on the blood supply. A spectrophotometer de- Oral Biol 1988;33:305-9.
8. Gazelius B, Olgart L, Edwail B, Edwall L. Noninvasive
termines oxygenation blood level changes. recording of blood flow in human dental pulp. Endod Dent
In young children, avulsed and replanted teeth with Traumatol 1986;2:219-21.
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surement of pulpal blood flow. Int Endod J 1988;21:307-12.
20 days after repIantation.‘7~‘8 Development of the 10. Schmitt JM, Webber RL, Walder EC. Optical determination
nerve supply lags behind that of the blood supply. of dental pulp vitality. IEE Trans Biomed Eng 1991;38:346-52.
Therefore the results of pulp testing and x-ray find- 11. Schnettler JM, Wallace JA. Pulse oximetry as a diagnostic tool
of pulpal vitality. J Endod 1991;17:488-90.
ings are not initially of diagnostic value after tooth 12. Millikan GA. The oxymeter, an instrument for measuring
replantation. However, repeated spectrophotometric continuously the oxygen saturation of arterial blood in man
readings taken at the start of replantation and con- Rev Sci Instrum 1942;13:434-9.
13. Wood EH, Geraci JE. Photoelectric determination of arterial
tinuing up to 40 days later might reveal an increase oxygen saturation in man. J Lab Clin Med 1949;34:387-401.
in the blood oxygenation levels. Such findings might 14. Yoshiya I, Shimada Y, Tanara K. Spectrophotometric moni-
indicate whether the blood supply has been reestab- toring of arterial oxygen saturation in fingertip. Med Biol Eng
Comput 1980;18:27-32.
lished, the healing process is taking place, and the 15. Alexander CM, Teller LE, Gross JB. Principies of pulse oxi-
pulp of the avulsed tooth is recovering. Therefore en- metry: theoretical and practical considerations. Anesth Analg
dodontic treatment would not be needed. 1989;68:368-76.
16. Chance B. Rapid and sensitive spectrophotometry: III-a
The preliminary results reported are from an in double beam apparatus. Rev Sci Instrum- 195 1;22:634-8.
vitro study. An in vivo study is needed to determine 17. Skoalund A. Tronstad L. Wallenius K. A microanaioaraohic
the reproducibility of recordings between both simi- study of vascular changes in replanted and autotr&$anted
teeth of young dogs. ORAL SURG ORAL MED ORAL PATHOL
lar and different teeth. In addition, the influence of 1978;45:17-28.
gingival blood flow on the recordings and data on how 18. Ohman A. Healing and sensitivity to pain in young replanted
large a mass of pulp tissue is needed for accurate re- human teeth: an experimental, clinical, and histological study.
Odontol T 1965;73:165-228.
cordings must be determined. Because the machine
was designed to read the changes in the blood Reprint requests.
oxygenation level in living tissue, it is not unreason- Roni Nissan, DMD
able to expect that similar responses will be attained Department of Endodontology
Temple University School of Dentistry
when the spectrophotometer is used on teeth in vivo. 3223 North Broad St.
In vivo tests of this hypothesis are in progress. Philadelphia, PA 19 140