Psychometric properties of a magnitude matching task using pressure algometry

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Psychometric properties of a magnitude matching task using pressure algometry
Brown, Felicia F
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Anesthesia ( jstor )
Anxiety ( jstor )
Facial pain ( jstor )
Pain ( jstor )
Pain perception ( jstor )
Pain sensitivity ( jstor )
Palpation ( jstor )
Placebos ( jstor )
Response bias ( jstor )
Skin ( jstor )

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Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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Unlimited thanks must go to Henry Gremillion, D.D.S., Melvin B. Benson, D.D.S.,

and the staff of the Parker E. Mahan Facial Pain Center at the University of Florida for

their guidance, support, and supplies. I would also like to thank James McSolay and Gary

Myers for their time and assistance in the administration of iontophoresis. Finally, love

and thanks go to my husband, Andrew Cagle, for data collection and, more importantly,

his unfaltering patience, support, and belief in me.



ACKNOWLEDGMENTS ............................................... ii

A B ST R A C T ......................................................... v



. . . . . . . . I

Temporomandibular Disorders .....
Pain Perception and Assessment ....
Magnitude Matching ............
Assessment of Pain in TMD .......
Pressure Algometry .............
Iontophoresis .... ...........
Design and Statement of Hypotheses

2 METHODS ........

Subjects ...........
Procedures .........
M measures ..........

3 RESULTS .........


Test-Retest Study ...
Validity Study ......
Visual Analog Scales .


. . . . . . . . . . .. 1 9

. . . . . . . . . . . 2 4

. . . . . . . . . . . 2 8

.... 29
.... 30
.... 35


. 2
. 4

.. 12
.. 17


I . . .


A PRELIMINARY SCREENING FORM .............................. 40

B DEMOGRAPHICS QUESTIONNAIRE ............................. 41

C MAGNITUDE MATCHING PROTOCOL .......................... 42

REFER EN CE S ...................................................... 43

BIOGRAPHICAL SKETCH ............................................ 49


Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy



Felicia Brown

May 1998

Chairman: Michael E. Robinson, Ph.D.
Major Department: Clinical and Health Psychology

Commonly used methods of measuring the subjective experience of pain, such as

category rating scales, pain threshold measures, cross-modality matching, and magnitude

estimation, are subject to inherent limitations and biases. Magnitude matching paradigms,

which require subjects to rate the magnitude of two alternating sensory modalities, an

experimental and a control stimulus, using a common scale of magnitude for both, provide

significant improvement over traditional measures. A standardization procedure, whereby

the experimental stimuli are standardized in terms of the control stimuli, is conducted to

cancel out individual factors in assigning pain ratings. Thus, magnitude matching is an

ideal method for examining discriminability and response bias, two components of pain

experience, and for examining group differences in pain perception.

The purpose of this research was to examine, in a nonpatient sample, the test-

retest reliability and validity of a magnitude matching procedure using a pressure

algometer, a clinically relevant pain stimulus, the importance of which has been

demonstrated. In studies in the literature on assessment of pain in temporomandibular

disorders (TMD), the pressure algometer has been found to be a reliable means of

measuring pressure-pain threshold and a sensitive measure of treatment-response in the


Test-retest reliability over two occasions, 3-8 days apart, was found to be

moderate for discriminability (r =.71, p <.01) but poor for response bias (r = .44). The

validity study used iontophoresis as an anesthetic in a double-blind, placebo and no-

treatment controlled design. Although it was hypothesized that subjects in the anesthesia

group would demonstrate reduced discriminability as compared with the control groups,

no differences were found among the 3 groups on this measure. However, differences in

response bias were found, with both the placebo control and no-treatment control groups

differing from the experimental group but not from each other. Possible explanations and

the implications of these findings are discussed.


Temporomandibular Disorders

Temporomandibular disorders (TMD) is a general classification for problems that

are arthrogenous, involving internal derangements within the temporomandibular joint, or

myogenous, involving extracapsular problems such as muscle and pain dysfunction or

myofascial pain dysfunction. Symptoms may include pain or tenderness in the region of

the masticatory muscles, clicking or popping sounds during condylar movements, and

limitation or deviation of the jaw opening. In an examination of the concerns of 157

patients seeking treatment for TMD, pain in the masticatory muscles and/or

temporomandibular joint was the primary complaint in 54% of the sample (Al-Hassan,

Ismail & Ash, 1986).

A literature review by Speculand and Goss (1985) attested that up to 88% of the

general population may have symptoms or signs of TMD at some time, with up to 25% of

the population experiencing severe symptoms. Only a small proportion of sufferers

present for treatment, and most patients have no radiographically detectable pathology of

the TMJ. In addition, the vast majority of persons who present for treatment in clinical

settings are women. It has been suggested that TMD affects women up to 9 times more

frequently than men (Green & Marbach, 1982).


The etiology of TMD is generally believed to be multifaceted and multi-etiological

(Dworkin, 1995). Psychological factors have been implicated in the etiology,

pathogenesis, and maintenance of TMD (Brown, Robinson, Riley & Gremillion, 1996).

Pain Perception and Assessment

The experience of pain is a subjective phenomenon and cannot be measured

independently from self-report (Heft & Parker, 1984). For the clinician treating pain

patients or the researcher studying pain, however, quantification of pain is necessary. The

methodologies for such quantification have come from psychophysics, which has always

been concerned with the perception and judgment of sensation magnitude, or intensity--a

quality that arguably pertains to all sensory modalities (Marks, Szczesiul & Ohlott, 1986).

It is impossible to discuss pain perception without also discussing measurement issues.

Several rating scales have typically been employed to obtain some quantitative

measurement of the experience of pain. Inherently, the sensitivity of such measures is

limited by the type of rating scale. For instance, category rating scales require the subject

to choose a number representing the magnitude of pain or a word from a list describing

the range of pain experience. These scales are restrictive in accuracy to the extent that the

subject's pain is not exactly described by the word choices. Some category scales are

graded, allowing the description of pain severity. Heft & Parker (1984), however, have

shown that the assumption that the categories are equally spaced, on which such scales

rest, is not valid. Both the position and the semantic meaning of the words in the list

contribute to the individual's choice of descriptors; the words do not divide the continuum

of perception into equal portions.

Improvement over category scales may be obtained by the use of cross-modality

matching paradigms, which were developed out of the hypothesis that, because intensity is

a universal attribute of perception, it should be possible to compare the correspondences

of one sensory mode to another, parallel sensory mode (Marks et al., 1986). A subject is

thus asked to adjust the intensity of one stimulus modality, such as loudness of a tone, to

match the perceived intensity of another stimulus modality, such as the brightness of a

light. The visual analog scale (VAS) is an example of cross-modality matching. A

common form of this scale provides the subject with a line, often 10 cm long, with the

instructions to mark the point which illustrates the intensity of his or her pain, given that

the bottom of the scale represents no pain, whereas the top represents the worst pain

imaginable. This method allows an infinite number of choice points. However, subjects

may find them difficult to use because no guidance is provided beyond the endpoints. In

addition, these scales are subject to regression bias. If a subject indicates that a stimulus

intensity is near the endpoint of the scale, but a later stimulus would rate even higher in

magnitude, the subject has no way to indicate this. Cross-modality matching is also not

well suited for use with some types of stimuli to which the subject may quickly adapt, such

as thermal sensations (Duncan, Feine, Bushnell & Boyer, 1988) or for stimuli for which

adjustment is difficult, such as taste or smell (Stevens & Marks, 1980).

A variant of cross-modal matching, magnitude estimation, solves some of the

above problems. Here, the subject gives a number that indicates the perceived intensity of

the stimulus. An unlimited range of responses is then available, eliminating floor and

ceiling effects. But at the same time, variability is introduced which limits the sensitivity in

capturing differences between small groups (Duncan et al., 1988). Some studies have also


shown that some subjects are significantly affected by context effects, such as the range or

mean intensity of the experimental stimuli, in making cross-modal matches, representing

an additional source of variability.

Magnitude Matching

Magnitude matching, introduced by Stevens and Marks (1980), was developed out

of the need for a method to measure and compare individual and group variations,

especially sensory deficits, in the perception of intensity of various stimuli (Marks et al.,

1986). This method incorporates principles from both cross-modality matching and

magnitude estimation. In these paradigms, the subject is asked to rate the magnitude of

two alternating sensory modalities, using a common scale of magnitude estimation for

both. By assigning the same numerical rating to different sensory events, the subject

indicates that they share the same intensity. Ratings from one modality, the experimental

stimuli, are then normalized in terms of the other, the control stimuli. Although the

paradigm assumes that cross-modal matches are absolute, the fact that context may play

an equal role suggests that the method may be used to assess intergroup differences, as

long as care is taken when making quantitative assessments; context effects may mitigate

any differences in discriminability, thereby leading to underestimation of group differences

(Marks et al., 1986; Stevens & Marks, 1980).

The normalization procedure, whereby the experimental stimuli are standardized in

terms of the control stimuli (by dividing mean ratings of the experimental stimuli by the

grand mean rating of the control stimuli), is conducted to cancel out individual

idiosyncracies. Examples of these include susceptibility to context effects, range of

numbers assigned to stimuli, and the absolute size of numbers assigned to stimuli, as well

as the expectations, past experiences and exposures each subject brings to the

experimental setting. In theory, these individual factors should be reflected equally across

modalities of magnitude estimates. Both between-group and subject variability across

testing sessions is reduced, allowing a subject to serve as his or her own control. The

result is more consistent data and improved test-retest reliability. Magnitude matching is

applicable to all continue of stimuli and adaptation is not a problem because only brief

exposure to fixed levels of stimuli is needed. Moreover, fewer trials are needed, which is

especially helpful in pain studies, where it is paramount to limit the number of painful

stimuli to which the subjects are exposed (Duncan et al., 1988; Marks, 1991; Stevens &

Marks, 1980).

Duncan and colleagues (1988) were the first to apply a magnitude matching

paradigm to examine group differences in pain perception. Their cleverly designed study

involved a simulation of differences in pain perception using as experimental stimuli two

ranges (45-49 and 46-50 degrees Celsius) of thermal stimuli for normal subjects rather

than two groups believed to show inherent differences in pain perception. Visual

brightness was the control stimuli and both magnitude estimation and magnitude matching

procedures were employed. When the median pain intensity ratings were simply

compared between the two groups, magnitude estimation did not reveal group differences;

nor did magnitude matching reveal more than a trend towards higher ratings among

subjects in the higher temperature group. With the normalizing procedure, however,

where all pain intensity ratings for each subject were divided by the subject's overall mean

estimate of control stimuli (visual brightness), robust group differences were found when

the data was collapsed across the entire range of temperatures and at each of the


individual temperature comparisons. These authors concluded that subjects are easily able

to match intensities of pain to another type of stimuli, with the normalization procedure

increasing sensitivity. Additionally, they suggest that the use of the magnitude matching

paradigm is most appropriate when making between-group comparisons of pain

perception or testing the effectiveness of analgesia.

In making group comparisons of pain perception, it is important to consider both

discriminability, which is the extent of sensory differences, and response bias, a measure of

willingness to report pain. Because both absolute and relational components contribute to

subjects' responses on magnitude matching tasks, it is possible to examine group

differences while separating out discriminability and response bias. To examine group

differences, the standardized ratings may be plotted on a graph with stimulus level on the

X-axis, and the standardized ratings on the Y-axis. When the data are collapsed for all

subjects in each group, the groups can be represented on the graph with a line identified by

a slope and intercept, where the former represents discriminability and the latter represents

response bias. Steeper slopes would indicate a greater change in standardized rating for

each unit of change in stimulus intensity. Similarly, higher Y-intercepts represent a

tendency to rate stimuli with a higher magnitude across the range of stimuli.

Fuller and Robinson (1995) used a magnitude matching paradigm to examine

differences in pain perception between chronic low back pain patients and nonpatient

controls. The study employed a clinically relevant pain stimulus, a lumbar extension

exercise, to compare perception of pain and heaviness, a nonpain stimulus, in these

subjects. The results of the study indicated that the chronic pain patients were able to

discriminate between painful levels of stimuli better than the control subjects. However,

the CLBP patients and controls were equal in discriminability between levels of heaviness.

In addition, the CLBP patients tended to underestimate the heaviness of weights they were

lifting, possibly suggesting a tendency to underreport relevant but nonpainful judgments.

This study highlighted the importance of testing for group differences using clinically

relevant stimuli rather than experimental pain stimuli. The former seems to be more

sensitive to features of clinical pain such as duration, affective associations to injury, or

fear of injury, factors which may not be operative when an experimental pain stimulus is


Assessment of Pain in TMD

Tenderness in the masticatory muscles is one of the most common clinical findings

in TMD (Gracely & Reid, 1995; List, Helkimo & Karlsson, 1991; Ohrbach & Gale,

1989b). Such tenderness indicates "trigger points," focal areas of muscle tenderness

within tight bands of the masseter and temporal muscles. No specific histopathological,

biochemical or electrophysiologic findings are associated with these hyperalgesic spots,

which may refer pain, tenderness, and autonomic changes, such as redness, swelling and

sweating to distant locations (Jaeger & Reeves, 1986; McMillan & Blasberg, 1994;

Reeves, Jaeger & Graff-Radford, 1986) but it has been suggested that CNS processing is

altered as a consequence of peripheral tissue injury, causing increased sensitivity to both

painful and innocuous stimuli (Reid, Gracely & Dubner, 1994). Trigger point sensitivity is

used in the diagnosis of myofascial pain as well as in quantification of the patient's

experience of pain. The common mode of assessment is manual palpation; firm pressure

on active trigger points can elicit or intensify spontaneously referred symptoms, whereas


latent trigger points are tender to palpation but do not elicit referred phenomena (Jaeger &

Reeves, 1986).

However, the method of palpation used varies widely, by site and by examiner,

despite attempts at standardization. A study examining the reliability of clinical findings in

temporomandibular disorders revealed kappa values ranging from .16 to .45, which are

moderate at best, for interexaminer reliability of assessment of pain based on palpation of

each of the masticatory muscles and joints. Summary scores proved somewhat more

reliable, with kappa values of .51 for pain on muscle palpation and .33 for joint palpation

(deWijer, Lobbezoo-Scholte, Steenks & Bosman, 1995). Similarly, Dworkin, LeResche

and DeRouen (1988) examined the reliability of clinical measurements in TMD and

determined that higher interrater reliability resulted from composite scores of each muscle

group. In addition, reliability of manual palpation of the masticatory muscles could be

improved with extensive training on the part of the examiner, but still to only marginal

levels of reliability. Both interrater and test-retest reliability of manual palpation was

examined by Stockstill, Gross & McCall (1989). These researchers reported a fair degree

of interrater reliability that was maintained over a five-week period.

Reasons for the difficulties in establishing reliability include variations in method of

palpation, such as which finger tip is used to palpate, the surface area of the finger tip, the

amount and variation of pressure applied, and the angle of pressure (List, Helkimo & Falk,

1989). Ohrbach and Gale (1989a) note that the exam procedure may reflect the

examiner's biases; the force of palpation may be dependent on the perceived severity of

the undiagnosed condition. In addition, how much verbal input the patient is asked to

provide, whether an ordinal scale or a visual analog scale is incorporated, and cues

provided to the examiner by observation of the patient's behavior, such as facial

movements, can contribute to measurement variability (Gracely & Reid, 1995). Patient

factors such as variability in signs and symptoms, the subjectivity of pain, and fluctuation

of symptoms over time also contribute to unreliable results (de Wijer et al., 1995; Gracely

& Reid, 1995). Variability in method has obvious clinical implications. Additionally, the

research literature is fraught with vague descriptions of palpation which are not replicable,

or descriptions allowing replication but lacking established validity (Ohrbach & Gale,


Pressure Algometry

A pressure algometer is a hand-held instrument which applies pressure over a

specific area at a constant, uniform rate, thereby allowing standardization and improving

the evaluation of muscle tenderness once a trigger point has been located (Gracely & Reid,

1995). Furthermore, examination with the algometer can replicate the individual's clinical

pain, suggesting that pressure is an appropriate stimulus to activate substantially similar

pain processes to those responsible for clinical pain (Ohrbach & Gale, 1989a). In other

words, the pressure algometer is a clinically relevant pain stimulus, the importance of

which has been previously pointed out by Fuller & Robinson (1995).

In the considerable body of literature, the pressure algometer has most commonly

been used to obtain the pressure-pain threshold (PPT), the subjective point at which a

gradually increasing pressure sensation becomes painful. Another specific advantage of

the pressure algometer over manual palpation is that tenderness may be quantified on a

ratio scale, versus the ordinal scale (e.g., comparatively more or less tender, or mild,

moderate or severe) rating of tenderness possible with palpation (List et al., 1989).


Numerous studies have examined the validity and reliability of the pressure algometer for

obtaining the PPT.

To demonstrate validity for PPT measures as an index of tenderness, several

researchers have compared patients with TMD or other types of head and neck pain with

asymptomatic controls. Seemingly unfailingly, the results have shown that PPTs are lower

in patient groups, indicating more tenderness among patients (List et al., 1989; McMillan

& Blasberg, 1994; Ohrbach & Gale, 1989a; Reeves et al., 1986; Reid et al., 1994).

Many studies have also examined various parameters of reliability of measurement

of the PPT. Intra- and intersession test-retest reliability have been demonstrated in both

groups of healthy volunteers (Jensen, Anderson, Olesen and Lindblom, 1986; Ohrbach &

Gale, 1989b), and TMD patients (List et al., 1989; Reid et al., 1994). Some between-

session fluctuation has been noted by some authors, perhaps due to learning or a decrease

in anxiety (Jensen et al., 1986) or, among patients, variation in pain level over time (Reid

etal., 1994).

Interrater reliability of PPT measurement has also been assessed in the literature.

For example, Reeves et al. (1986) found that 2 examiners could reliably arrive at similar

measurements taken from several different points on the head and neck of myofascial pain

patients. Moreover, these authors reported a high degree of reliability between 2

experimenters when locating unmarked trigger points and measuring their sensitivity.

Other studies attest to the usefulness of the pressure algometer and PPT

measurement for measuring treatment outcome. First, among head and neck pain patients,

highly reliable increases in pain-threshold values were demonstrated after passive

stretching. In nonpatient samples, subcutaneous injection of local anesthesia and


application of TENS electrical stimulation have both been shown to increase PPTs (Jensen

et al., 1986; McMillan & Blasberg, 1994; Graff-Radford, Reeves, Baker & Chiu, 1989).

A study by Bushnell and colleagues (1991) demonstrated that TENS significantly altered

pain threshold and significantly decreased subjects' ability to detect small differences in

heat stimuli, whereas placebo TENS altered neither pain threshold nor discriminability.

The results of another study (Graff-Radford, Reeves, Baker & Chiu, 1989)

indicated that a reduction in pain intensity, as measured by VAS, could occur without a

concomitant reduction in trigger point sensitivity as a result of TENS treatment. In some

experimental groups, a significant difference in VAS rating was seen; however, no group

differences were found in pre- to post-treatment algometer change scores. The authors

offer possible explanations: the 10 minute application time may not have been sufficient to

result in pain inhibition, TENS alone is not suitable for treatment of myofascial pain, or the

sample size may not have been large enough to detect a significant effect. However, the

authors do not consider the possibility that the experimental manipulation may have had an

effect on response bias but not on the sensory-discriminative dimension of pain experience,

thus yielding differences in the VAS measure but not in trigger point sensitivity.

Together, these treatment outcome studies suggest that pressure algometry is, at

least to some extent, responsive to intervention in the laboratory. However, because the

PPT was used to measure sensitivity, it is not certain whether the reductions demonstrated

reflect a decrease in response bias and/or a decrease in the sensory-discriminative aspects

of pain. Because it is a pain threshold measure, the PPT is subject to the inherent

limitations of threshold measurement: subjectivity to placebo effects, response bias, and

the influence of instructions given, in addition to potential insensitivity to explicit pain-

reducing manipulations (Price, 1988).

Some of these shortcomings were avoided in a study in which the authors

(Svensson, Arendt-Nielsen, Nielsen, & Larsen, 1995) obtained stimulus-response curves in

addition to the PPT of healthy controls and patients with facial pain. Curves were

obtained by asking subjects to make cross-modal matches of pain intensity onto visual

analog scales. Although the results of the study did not demonstrate significantly different

PPTs between the pain patients and controls, significantly steeper slopes in the S-R curves

were found in the patient sample versus controls. In addition, injection of local anesthetic

into the masseter muscles of control subjects significantly increased PPTs and reduced the

S-R curve slopes relative to baseline measurements, whereas injection of saline increased

the slopes. PPTs were unaffected by the saline. Although the authors do not discuss the

issue of response bias versus sensory-discriminative aspects of pain report, it seems

reasonable to hypothesize that the changes seen in slope do indeed indicate changes in

sensory-discriminative processes. The PPTs, in contrast, may not have been sensitive

enough to experimental manipulation to result in change. Svensson et al. note that using

S-R curves may provide the basis for a triangulation procedure; thus, a magnitude

matching procedure as we are proposing seems like a logical next-step in the literature.


Iontophoresis is "the introduction, by means of an electric current, of ions of

soluble salts into the tissues of the body for therapeutic purposes" (Lark & Gangarosa,

1990, p. 109). In a recent literature review, Gangarosa, Ozawa, Onkido, Shimomura and

Hill (1995) conclude that iontophoresis provides an optimal method for application of

drugs in the treatment of many surface tissues.

Use of iontophoresis has been in and out of favor since its first applications, which

may be traced back to the mid 1700s. Early equipment was crude and did not yield

reliable results. Despite this, unbridled and overly optimistic claims for the benefits of

iontophoresis were made, without the delineation of procedures to ensure effectiveness

and safety (Gangarosa, 1981 a; Gangarosa, 1982). Currently, iontophoresis is an "old

process that has received new life" with the advent of newer technology and drugs and the

advancement of scientific knowledge regarding transdermal medication delivery

(Gangarosa, 1988, p. 402).

In human skin, the primary barrier to percutaneous absorption of any material is

the stratum corneum, the composition of which is approximately 20% lipids, 40%

proteins, and 40% water. Electrically charged electrodes will repel an ion that is similarly

charged; thus ions with a positive charge may be introduced into the body with a positive

electrode (anode), and negatively ions will be repelled in with a negative electrode

(cathode) (Byl, Zellerbach & Pfalzer, 1996). Iontophoresis alters skin permeability by

causing changes in the arrangement of these molecules. According to the "flip-flop gating

model," when an electric potential, the driving force in iontophoresis, is applied across the

stratum corneum, certain polypeptide molecules reorient into a parallel arrangement and

repel neighboring dipoles, forming pores. Hair follicles, sweat gland ducts and sebaceous

glands act as diffusion shunts, as the reduction in resistance provides pathways for the

entering molecules.

For iontophoresis to be clinically effective, the target tissue must be at an

accessible depth in the body. It does not have to be at the skin surface in order for the

drug to penetrate in sufficient quantity. Bursa, disk, diskal ligament, and joint capsules, as

well as the surface skin and mucosa may all be treated effectively with iontophoretic


The amount of drug actually delivered to a given site and the depth of penetration

depend primarily on the dose of the electrical current; the concentration of the drug and

the total amount of the applied solution are less important (Oshima, Kashiki, Toyooka,

Masuda & Amaha, 1994).

The level of current applied to a site depends on the surface area (more current

may be applied to a larger area) and to the individual's skin tolerance (Irsfeld et al., 1993;

Lark & Gangarosa, 1990). Increasing the electric current may decrease application time.

However, this increases the risk of cutaneous burns. Lower levels are generally more

comfortable (Oshima et al., 1994; Lark & Gangarosa, 1990) but take longer to apply. Up

to 5 mA may be used if the individual can tolerate it (Byl et al., 1996).

There are many advantages to using iontophoretic application instead of injection

of medication. For example, the risks and inconveniences of injection or intravenous

treatment, such as pain, tissue damage, and infection, are avoided. At the body surface, a

high concentration of a medication can be administered into a lesion at a faster rate than

with passive transport and without a detectable level of the drug appearing in the

bloodstream or in other vital organs. On the other hand, if desired it allows delivery

directly into the bloodstream and prevents the variation in absorption and metabolism seen

in oral administration, and avoids the first pass elimination of a drug by the liver. A

controlled, continuous delivery of a drug is ensured, preventing overdose and allowing

rapid termination of delivery if necessary. Another advantage is that the body does not

respond by immunologically sensitizing when medications such as antibiotics are delivered

with iontophoresis. Additionally, iontophoresis may increase patient compliance and

satisfaction and decrease anxiety through the avoidance of needles (Costello & Jeske,

1995; Gangarosa, 1982; Kassan et al., 1996).

A disadvantage of iontophoresis is the amount of time necessary for effectiveness.

Another is the mild hyperemia, tingling, irritation, or burning that may occur on the skin

surface. Because continuous, unidirectional current has an anesthetic effect (Byl et al.,

1996), these side-effects may occur without the sensation of pain and may heal slowly,

especially if they occur under the cathode. However, it is possible to take measures to

minimize the risk of such adverse effects. Patients with excessive susceptibility to the

application of electrical currents, patients with cardiac pacemakers or other implanted

devices, and patients with known sensitivity to the drugs being administered are not

candidates for iontophoresis (Lark & Gangarosa, 1990).

Effective treatment of many conditions in several fields has been described in the

iontophoresis literature, including dermatology (e.g., application of antiviral agents to

surface tissues, treatment of burns with antibiotics) (Kassan et al., 1996; Singh & Singh,

1993), otolaryngology (e.g., for local anesthesia for simple surgeries of the tympanic

membrane) (Costello & Jeske, 1995), and ophthalmology (treatment of eye lesions).

Physical therapists have used iontophoresis of anti-inflammatory medications to treat a

variety of musculoskeletal conditions (Costello & Jeske, 1995). Gangarosa (1988) has

noted that iontophoresis is particularly well suited for treatment in dentistry, because many

conditions are near the surface of the body. Applications include the treatment of

hypersensitive dentin with fluoride, treatment of oral ulcers and herpes orolabialis, and

delivery of local anesthetics for a variety of procedures, such as extraction of teeth,

biopsies, anesthesia prior to injection or intravenous needle insertion, or as a substitute for

injection for local anesthesia (Carlo, Ciancio & Seyrek, 1982; Costello & Jeske, 1995;

Gangarosa, 1974; Gangarosa, 1981 b; Gangarosa, 1982;Gangarosa, 1988). Lark and

Gangarosa (1990) have reported the utility of iontophoretic delivery of local anesthetics or

corticosteroids in treating temporomandibular joint and myofascial pain dysfunction

syndromes. Acute muscle disorders, such as splinting and inflammation, disk disorders

and inflammatory disorders of the joint, such as arthritis and capsulitis, are all responsive

to medication delivery with iontophoresis. In addition, chronic mandibular hypomobilities,

such as myostatic and myofibrotic contracture of the elevator muscles or capsular

tightness, and growth disorders of the joint may benefit from iontophoretic administration

of drugs.

It has also been well established that iontophoresis is an effective method of

achieving local anesthesia (Maloney et al, 1992). Moreover, iontophoresis provides

significant advantages over traditional topical methods of anesthesia, which operate by

passive diffusion over the concentration gradient across the skin (Singh & Singh, 1993).

Studies have shown that topical cream anesthetics, such as a lidocaine/prilocaine mixture,

can be reasonably effective; however, they require a considerably longer application time,

and do not provide as complete an anesthetic effect as does iontophoresis (Greenbaum &

Bernstein, 1994, Irsfeld, Klement & Lipfert, 1993). The depth of anesthesia achieved

with iontophoresis has been shown to be comparable to that of injection, but the duration

time is shorter (Russo, Lipman & Comstock, 1980). The shorter duration time is likely

due to capillary dilation induced by iontophoresis, which increases regional blood flow and

corresponding removal of the drug from the site (Kassan et al., 1996). Duration may be

increased by using a solution containing epinephrine, a vasoconstrictor (Costello & Jeske,

1995; Gangarosa 1981 a). Because systemic administration of epinephrine causes

sympathomimetic effects, it is recommended that iontophoretic application of epinephrine

be avoided in persons with known sensitivity to epinephrine (Costello & Jeske, 1995).

In sum, it is clear that researchers (e.g., Lark & Gangarosa, 1990) have attested to

the clinical efficacy of iontophoresis as a method of treatment in certain TMD and MPDS

conditions. In addition, the established use of iontophoresis in administering topical

anesthetics, and the clear advantages of iontophoretically applied anesthetics over both

simple topical application and injection, suggest that iontophoresis was an optimal choice

for administration of local anesthesia for our research protocol.

Design and Statement of Hypotheses

This research was designed to examine the psychometric properties of the

magnitude matching procedure using healthy subjects. Test-retest reliability was examined

by administering the procedure to subjects on two separate occasions, with a range of 3 to

8 days between sessions. The validity and clinical utility of the magnitude matching task

were examined in a double-blind, placebo and no-treatment controlled paradigm. Subjects

were randomly assigned into one of 3 conditions upon entry in the study, with an attempt

made to obtain an equal number of male and female subjects in each condition. The

experimental group (N=21) received iontophoretically applied lidocaine with epinephrine,

whereas the control group (N=24) received placebo iontophoresis without lidocaine. The

no-treatment group (N=20) was obtained using the data from session 1 of the test-retest


For study #1, test-retest reliability, it was expected that the magnitude matching

procedure would be highly reliable, as demonstrated by the reliability coefficient

(Pearson's r).

For the validity study, it was anticipated that the experimental group, which

received the anesthesia, would demonstrate decreased discriminability, shown by flatter

(less steep) slopes than those of the other two groups. It was not expected that a

significant difference would be found between slopes for the placebo and no-treatment

control groups. It was hypothesized that both the experimental group and the placebo

group would demonstrate lower Y-intercept values than the no-treatment control group,

indicating a decrease in response bias, or a tendency to report the stimuli as less painful.

A significant difference was predicted between the VAS scores for pain intensity

and unpleasantness between the experimental and the two control groups, with the latter

groups displaying higher scores on both scales.



Subjects were recruited from the University of Florida undergraduate subject pool,

the University of Florida Colleges of Dentistry and Health Professions. In addition, some

subjects were University of Florida or Shands Teaching Hospital employees. All subjects

were recruited in accordance with guidelines designated by the University of Florida

Institutional Review Board and the Shands Teaching Hospital IRB. Some undergraduate

subjects received course credit for their participation.

Subjects were read a list of screening questions to ascertain that they met the

criteria designed for subject safety (see Appendix A). Screening ensured that subjects had

no skin conditions that would contraindicate the use of iontophoresis (e.g., discoloration

or blemishes on the skin), and no past or current symptoms of pain in the jaws or face.

Questionable subjects were given a palpation exam by one of the co-investigating dentists;

subjects demonstrating pain or gross dysfunction were excluded from the study. Subjects

also were screened for known sensitivity to epinephrine or a cardiac condition, factors

which would contraindicate the use of iontophoresis and/or lidocaine with epinephrine.


In study # 1, designed to establish test-retest reliability, subjects signed the

informed consent form and completed a demographics questionnaire (see Appendix B)

before undergoing the magnitude matching protocol described below. Between 3-8 days

later, subjects returned to the laboratory for repetition of the magnitude matching.

Following each session, subjects completed 10 cm, horizontal visual analog scales to

indicate the intensity of overall pain and unpleasantness experienced during the procedure.

At the end of the second testing session, subjects were given a full explanation of the

purpose and hypotheses of the study.

Subjects participating in Study #2, the validity study, were informed that they had

been randomly assigned into one of two conditions, the anesthesia group or the placebo

group. Subjects were told that the anesthesia device operates by a very mild and safe

electrical current and that some subjects have reported feeling a "barely perceptible"

sensation (Bushnell et al., 1991). Subjects completed the informed consent and

demographics questionnaire. The possible adverse effects were described and subjects

were given the opportunity to ask any questions about iontophoresis or the drugs being


The experimental group was administered a dosage of 15 mA minutes of lidocaine

2%, 1/100,000 epinephrine to the skin over the masseter muscle. This took an average of

12 15 minutes per patient using a 1.2 mA current. The treatment was performed using

the Empi Du Pel iontophoresis unit (#LR64406), using Empi small size dispersive and

active electrodes. This unit has been designed to automatically control the current and

rate of dosage in accordance with the individual's skin resistance. The placebo control

group underwent application of electrodes, without lidocaine and epinephrine, in the same

location as the experimental group, and were given the same description of the sensation

they may feel. However, the electrical current was not applied. The electrodes were in

place for approximately 12 minutes, as with the experimental group.

In both conditions, a separate trained examiner, blind to experimental condition,

administered the magnitude matching protocol and the visual analog scales. Following

completion of the study, subjects were given a full explanation of the purpose and

hypotheses of the study. The subjects were instructed to use a moisturizer or hand lotion,

preferably containing aloe, on the treated skin under both electrodes.


Magnitude Matching Protocol

In the magnitude matching paradigm, used to compare standardized aspects of

pain ratings over time and between the experimental and control groups, 3 different levels

(6, 7, and 8 foot pounds per square inch) of manual pressure were applied using a hand-

held pressure algometer (Pain Diagnostics, Inc). Lines of 3 different lengths (70, 85 and

100 mm), drawn on 5x7 inch index cards, were presented as standardization stimuli.

Subjects were asked to rate pressure stimuli and line lengths on the same generic number

scale, where 0 indicates no discomfort or pain and no length, and where the top end of the

scale is open. Subjects are instructed to use larger numbers for longer lines and greater

pain or discomfort, and smaller numbers for shorter lines and less pain or discomfort. The

instructions for this procedure may be found in Appendix C.

Manual pressure was applied at the insertion of the masseter muscle, one

centimeter superior and anterior to the angle of the mandible, as described in the

instructions for palpation in the Research and Diagnostic Criteria guidelines for assessment

of temporomandibular disorders (Dworkin & LeResche, 1992). Training in location of

this point was provided to the experimenter by the investigating dentist, a specialist in the

assessment and treatment of facial pain. This point was marked in ink in order to ensure


consistency in site of application. Pressure was increased over one second, then held for

two seconds. The importance of standardized rate of application has been emphasized by

several authors (e.g., Jensen et al., 1986). Using a pad size approximately equal to one

square centimeter circular area, ratings were assessed at 6, 7 and 8 foot pounds per square

inch; pilot data collected using an up-down transformation sequence procedure (Wetherill

& Levitt, 1965) on 12 nonpatient subjects (6 female, 6 male) revealed an average pain

threshold of 7 foot pounds per square inch.

Subjects were given two practice trials, applied to the right wrist bone, using

pressure stimuli of 1 and 3 foot pounds per square inch. Once it was clear that the subject

understood the procedure, the 3 pressure levels were delivered in a randomized sequence

of groups of 3, with no level repeated until all other levels have been presented.

Presentation of the 3 pain stimuli was alternated with the similarly randomized display of 3

line lengths, for a total of 9 pressure ratings and 9 ratings of line length.

Because degree of muscle tension in the jaw has been shown to influence the

pressure-pain threshold (McMillan & Lawson, 1994), subjects were asked to place their

teeth together without clenching their jaw. For ease of administration, data was collected

from the right side of the face. Reid et al. (1994) reported that in control subjects,

pressure-pain thresholds differed among various sites, but no difference between the two

sides of the face was found. Furthermore, some authors have reported a significantly

higher threshold on the right side, seen only in right handed subjects; such effects were

not found in left handed or ambidextrous subjects (Jensen, Rasmussen, Pedersen, Lous &

Olesen, 1992).

The magnitude matching paradigm was used to obtain 2 indices, the slope and

intercept of standardized regression lines. The slope represents ability to discriminate

between pressure stimuli, and the intercept represents response bias. Derivation of these

indices is described in the Results section below.

Visual Analog Scales

Following the magnitude matching procedure, subjects were asked to rate overall

painfulness and overall unpleasantness on 2 horizontal lines of 10 cm length drawn on a

half-sheet of 8x10 inch paper. Endpoints were designated as "not at all

painful/unpleasant" and "the worst pain/most unpleasant imaginable." Subjects were

instructed to indicate degree of pain/unpleasantness by drawing a vertical line at the

appropriate point on the scale. Price & Harkins (1988) describe the many advantages of

visual analog scales in the assessment of pain intensity, including evidence for power

functions and ratio scale data, ease of administration, relatively bias-free results, validity

and reliability, and sensitivity to pain-reducing interventions.


All analyses were conducted using the SPSS 7.5 for Windows 95 statistical

program (Norusis/SPSS Inc, 1995). The data were first examined for violation of

assumptions. Through examination of histograms plotted for each group, outliers were

identified by distance from the mean. An attempt was made to ascertain the reason for

anomalous results given by 7 subjects. Equipment failures, scaling in the wrong direction,

and failing to scale consistently or on one common scale were the cause of outliers. Due

to a differential outlier rate in the experimental group (4 subjects), which dropped the

number of cases to below the goal of at least 20 subjects per condition, the decision was

made to drop all outliers and to replace the subjects in the experimental group.

Replacement ensured adequate power in detecting significant differences.

Frequencies and percentages and, for noncategorical variables, ranges and means,

for the demographics of sex, age, ethnicity, income, education, marital status, and

occupation are shown in Tables 1 and 2, respectively. A one-way ANOVA confirmed that

there were no significant differences between the experimental, placebo control and no-

treatment control groups on any demographic variables.

For both the test-retest reliability and validity studies, calculation of the indices

derived from the magnitude matching paradigm were based on the methods described by

Stevens and Marks (1980), Duncan et al. (1988), Feine and colleagues (1991), and Fuller

and Robinson (1995). The mean rating of each of the 3 pressure levels was first calculated

Table 1
Frequencies and Percentages for Demographic Variables

African American
East Indian
Student Status
Marital Status













Table 2
Ranges. Means and Standard Deviations for Noncategorical Demographic and Visual
Analog Scale Variables

VAS Pain
VAS Unpleasantness
Retest Pain
Retest Unpleasantness





for each subject. Then, in order to standardize these mean ratings for each subject, each

subject's mean rating was divided by that subject's grand mean rating of all of the control

stimuli (lines). Each subject thus generated 3 standardized values, one for each level of

algometer pressure. Regression equations were calculated for each condition, with the

standardized ratings as the dependent variable and the pressure level as the independent

variable. These regressions yielded a slope and intercept value for the magnitude

matching task. The slope and intercept values were then used to examine test-retest

reliability and to test for differences between the experimental (anesthesia), placebo

control (placebo anesthesia), and no-treatment control (Time 1 of the test-retest reliability

study) groups.

To examine test-retest reliability, Pearson's r was calculated for the slopes and

intercepts between Session 1 and Session 2. The results of these analyses provided

support for moderate test-retest reliability of the slope, but not the intercept, over a 3-8

day period. The correlation between the slopes across the two sessions was .71 (p < .01).

For the intercepts, a nonsignificant r of.44 was obtained.

To test for slope differences between the 3 groups in the validity study, a one-way

ANOVA was conducted. In addition, pairwise comparisons had been planned a prior.

Intercept differences were also tested with a one-way ANOVA. The means and standard

deviations for each of the 3 groups and the results of the ANOVA tests are presented in

Tables 3 and 4. The results indicate that there were no significant differences in slope

(discriminability) between the 3 groups, F (2, 62)=. 13, p = .88. Pairwise comparisons

were therefore not conducted. However, significant intercept (response bias) differences

were obtained: F (2, 62) = 8.03, p = .001. The planned pairwise comparisons with Tukey

Table 3
Means and Standard Deviations for One-Way ANOVA Intercept

Group Mean S.D.
Placebo Control* 1.06 .27
Treatment .74 .24
No-treatment Control* .93 .28
F (2, 62) = 8.03, = .001

Table 4
Means and Standard Deviations for One-Way ANOVA Slope

Group Mean S.D.
Placebo Control .14 .09
Treatment .15 .07
No-treatment Control .15 .08
F (2, 62)=.13, p =.88

correction revealed that both the placebo control and no-treatment control groups were

significantly different from the experimental group. However, the two control groups

were not significantly different from each other.

The VAS mean ratings and standard deviations for overall pain and unpleasantness

are shown for each group in Table 2. A one-way ANOVA found no significant

differences on these ratings between any of the 3 conditions. For overall pain, F (2, 59) =

1.34, p = .27. For unpleasantness, F (2, 59) = .66, p = .52.


The aim of this research was to examine the psychometric properties, validity and

test-retest reliability, of a magnitude matching task. The protocol employed the

methodology described by Stevens and Marks (1980). A pressure algometer (Ohrbach &

Gale, 1989a) was used to provide a clinically relevant pain stimulus, emphasized by Fuller

and Robinson (1995). Magnitude matching techniques yield regression lines which

provide separate values for two components of pain threshold: discriminability (slope)

and response bias (intercept). It was hypothesized that the slope and intercept would

show high reliability between the two testing sessions. Moderate test-retest reliability over

a 3-8 day time period was shown for the discriminability component. However, poor test-

retest reliability was observed for response bias for the same time period. It was also

expected that the magnitude matching procedure would be sensitive to a known analgesic,

iontophoretically administered lidocaine with epinephrine. Specifically, the treatment

group was expected to demonstrate a reduction in discriminability, shown by flatter

slopes, as compared with the two control groups. In addition, both the experimental and

placebo group were hypothesized to show a decrease in response bias, indicated by lower

intercept values, as compared with the no-treatment control group. The results of the

validity test indicate that the magnitude matching procedure was indeed sensitive to the

group differences induced by the iontophoretically applied lidocaine and epinephrine

anesthetic. This is evidenced by the significant differences found between the 3 groups on


the intercept values. Both the placebo and no-treatment control groups were significantly

different from the anesthesia group, but not from each other, with both control groups

tending to report more pain.

Test-Retest Study

The data indicate that the study participants were able to discriminate between the

3 pressure levels (6, 7 and 8 foot pounds per square inch) equally well on both testing

occasions. The lack of reliability of the intercept component suggests that unknown

factors affected the subjects' response bias in an inconsistent way across time. Possible

mediators may include learning or state factors such as mood.

In the present study, subjects were tested while sitting in a dental chair in a clinical

examination room. As part of the consent process, they were informed that some of the

pressures they would be receiving may produce temporary discomfort or pain. These

aspects of the experimental situation, along with unfamiliarity with the task, may have

contributed to a state of increased anxiety that was not operative during the second testing

session. Other research has suggested that task instructions may be anxiety-inducing and

that the resulting anxiety can affect task performance and signal detection theory

parameters (Dougher, 1979; Malow, 1981; Schumacher & Velden, 1984; Weisenberg,

Anram, Wolf& Raphali, 1984).

In their research on pressure-pain threshold with the pressure algometer, Jensen et

al. (1986) found a slight but significant increase in PPT over the course of 5 weekly

testing sessions. The authors suggest a reduction in anxiety with increased familiarity with

the procedure or a learning effect as possible mediating factors. Although the PPT does

not yield separate values for discriminability and response bias, the authors' observed

increase in PPT over time, if due to anxiety, would be consistent with an increase in

response bias, or a lesser tendency to label the test stimuli as painful.

Validity Study

Unexpectedly, it was found that the placebo group tended to report the most pain,

as demonstrated by the intercept values (see Table 3). This higher value suggests that

factors associated with the application of the placebo condition contributed to increased

response bias in that group. In contrast, such factors did not have consistent effects on the

other two groups. For example, the identical instructions given to the placebo and

treatment groups included the potential risks and discomforts of the electrode pads,

lidocaine and epinephrine, and iontophoresis. It is possible that factors such as anxiety

influenced the response bias in these groups. The link between anxiety and pain has been

well established by early researchers (Melzack & Dennis, 1971; Rollman, 1977;

Stemrnbach, 1978). Elevated anxiety levels have been associated with reduced pain

tolerance and lowered pain thresholds in medical, psychiatric and nonpatient samples

(Malow, West & Sutker, 1987). It is generally assumed that greater anxiety contributes to

a greater pain reaction to painful stimuli (Malow, 1981). State anxiety has also been

correlated with affective and evaluative, but not sensory, dimensions on the McGill Pain

Questionnaire. These results would be consistent with differences in response bias.

In the present study, the anesthetic may have counteracted the effects of anxiety in

the treatment group whereas the placebo control group may have continued to experience

these effects. As a result, their response bias values were elevated in comparison to the

treatment group. Furthermore, the participants in the no-treatment control group were

aware that the risks described above were not applicable to them; thus their response bias

may have remained unaffected by anxiety or other factors which influenced the other

groups. If anxiety did indeed mediate these results, the observed effect for response bias

may actually be strengthened. Response bias represents subjects' willingness to report

pain. Thus, subjects in the placebo group did not show a tendency to inhibit their report

of pain; anxiety may have in fact heightened their pain. It is important to note, however,

that in the present study, anxiety during the procedure was neither assessed nor


In contrast with the intercept differences found, and with the hypothesis, no

significant differences were found between the 3 groups in discriminability, as illustrated

by the parallel slopes in Figure 2. Thus, it appears that the experimental manipulation did

not affect this variable; all groups were apparently able to discriminate between the 3

levels of pressure equally well. Figure 2 also illustrates the standardized pressure variables

at each pressure level.

Although the present study was not designed to investigate the mechanisms of the

anesthetic used as the treatment, the known mechanisms of local anesthetics may account

for the observed group differences in response bias versus discriminability. It is possible

that the experimental manipulation was effective enough to differentially influence the

groups' response bias, resulting in differences in the report of pain, without substantially

altering their ability to discern the differences in pressure level. In other words, subjects in

each group could still discriminate the pressure levels, but they differed in whether or not

they labeled the stimuli as painful.

Several factors are known to contribute to differential blocking of the various

types of nerve fibers. For example, the minimum blocking of an anesthetic, defined as the

6 7 8
Pressure Level

Figure 1. Standardized Mean Pain Ratings for 6, 7, and 8 Pounds


"drug concentration that just halts impulse traffic" (de Jong, 1996, 150) varies with nerve

fiber diameter and concentration of voltage-gated sodium ion channels. These channels

act as binding sites for lidocaine and other local anesthetics. In addition, nerve blockade is

frequency dependent, meaning that opportunities for the local anesthetic to bind to the

sodium channels are enhanced when the frequency of stimulation is increased. The faster

the nerve is made to fire, the more complete the resulting nerve block. As a result, fibers

such as nociceptive and sympathetic nerves, which carry rapidly flowing impulses, require

a less concentrated local anesthetic to disrupt impulse propagation than do large motor

fibers. Thus, the latter may remain functional while A-delta and C fibers, carrying pain-

related impulses, are inhibited (de Jong, 1996). In general, local anesthetics first result in a

loss of sympathetic function, then loss of pinprick sensation, followed by touch and

temperature discrimination, with loss of motor function affected last (Barash, Cullen, &

Stoelting, 1997; de Jong, 1996).

Lidocaine, in clinical doses, completely inhibits depolarization. The addition of

epinephrine, a vasoconstrictor, decreases the rate of vascular absorption, allowing more

anesthetic molecules to reach the nerve membrane and improving both the depth and

duration of anesthesia (Berde & Strichartz, 1994).

However, because of the differential nerve block factor described above, an

individual treated with lidocaine (and epinephrine) may still perceive touch and pressure

after pain sensations have been eliminated (de Jong, 1996). Therefore, it is highly possible

that discriminability between the 3 levels of pressure used in the present study remained

unaffected on the basis of the mechanisms of action of lidocaine. Although Lineberry and

Kulics (1978) reported that in rhesus monkeys, subcutaneous injection of lidocaine leading

to a partial local block of peripheral nerves resulted in a decrease of discriminability

between noxious intensities of electrical stimuli (which presumably are affected by

lidocaine quicker than are pressure sensations) in a signal detection study, it appears that

the differential effects of lidocaine on discriminability in humans are undocumented in the


A considerable body of earlier signal detection research illustrates the differential

effects of drugs on response bias versus discriminability. For example, Chapman, Murphy

and Butler (1973) found that a 33% nitrous oxide solution affected a change in both

discriminability of certain heat stimuli and response bias. In contrast, diazepam was found

not to affect sensitivity or response bias relative to placebo (Chapman & Feather, 1973).

In studies of placebo alone, it was found that a placebo analgesic increased response bias,

but not discriminability, to pain, heat and warmth (Clark, 1969). Feather, Chapman and

Fisher (1972) obtained similar results. The signal detection research employed

systemically, rather than cutaneously delivered drugs, which would likely hold greater

influence over cognitive tasks such as discrimination. However, it is possible that

lidocaine also affects discriminability and response bias differentially. Both the observed

differences in response bias and the lack of differences in discriminability may be due to

the effects of the lidocaine itself or to other factors.

Other reasons why the results of the present study did not yield group differences

in discriminability may involve methodological issues. For example, Green and Swets

(1966) point out that in classic psychophysics studies, performance may stabilize only after

many sessions. When only a few trials are conducted, data is then collected during the

period when subject performance is at its maximal level of fluctuation, and both


discrimination and response bias may change during a single testing session. It is possible

that not enough trials were administered to reveal group differences. Fluctuation may also

have affected the results of the test-retest study if performance was not yet stabilized.

However, repeated trials in the present study would have compromised the

ecological validity to the clinical situation. In the assessment of facial pain in patient

samples, it would not be possible to administer many pressure trials without aggravating

existing pain conditions. Because the magnitude matching protocol is intended for

eventual use with pain populations, clinical relevance was prioritized.

Visual Analog Scales

It was hypothesized that significant differences would be found on overall pain and

overall unpleasantness as measured by the visual analog scales. However, no differences

were found among the 3 groups on either of these variables. It is possible that the VAS

measures were not sensitive to group differences, perhaps due to their greater face validity

and subjects' desire to minimize their experience of pain and unpleasantness in front of the



Unique features of the present research included the use of a magnitude matching

task using a clinically relevant pain stimulus, a pressure algometer. Both magnitude

matching and pressure algometry are believed to represent improvements over more

traditional means of pain assessment, such as other scaling or threshold measures using

experimental pain stimuli, that have unclear relevance to clinical pain. In addition,

iontophoresis was employed to facilitate the action of topically applied lidocaine with

epinephrine, a standard treatment in many clinical settings. Test-retest reliability was

examined over a 3-8 day period and validity was investigated with a double-blind, placebo

and no-treatment control experimental design.

Test-retest reliability was found to be moderate for the discriminability index but

poor for response bias over time. Subjects were apparently able to scale consistently

across the testing sessions but their performance was affected by nonsensory factors.

Anxiety related to the task and laboratory conditions, which diminished with familiarity by

the second session, is a possible explanatory factor.

Discriminant validity for the magnitude matching task using pressure algometry

was demonstrated by the sensitivity of the procedure to a known analgesic,

iontophoretically applied lidocaine with epinephrine. Group differences were seen

between each of the control groups and the treatment group on the measure of response

bias. These results are consistent with the hypotheses. However, in contrast to


hypotheses, no group differences were observed in discriminability. These data suggest

that, relative to both placebo anesthesia and no treatment at all, subjects in the anesthesia

group tended to report lower levels of pain. All groups were able to discriminate between

the 3 levels of pressure. These results may be explained by the differential mechanisms of

action of lidocaine on discriminability or by a combination of other factors such as anxiety

or methodological constraints.

Visual analog scales for overall pain and aversiveness related to the magnitude

matching protocol was assessed for comparative purposes. Although group differences

were expected on both of these scales, none were found. It is possible that these measures

were more face valid and less sensitive to differences than was the magnitude matching


An aim of the present research was to examine the psychometric properties of the

magnitude matching using healthy subjects, as a precursor to research with patient

populations. Specifically, the use of the algometer to deliver pressures to the masseter

muscle was designed with considerations for the assessment of facial pain. The fact that

support was found for the psychometrics of the protocol suggests that magnitude

matching methodology may be applied to this and other pain populations. Because it is

sensitive to an analgesic, magnitude matching may be able to in distinguish between

patient and nonpatient samples. In addition, the results suggest that magnitude matching

may be useful as an outcome measure for a variety of treatments for clinical pain.

Clinically, the methodology yields more information than do more traditional assessment

measures, such as other scaling techniques or pain thresholds. Of interest is the fact that a

plot of the log transformed standardized pressure variable for each condition revealed a

linear relationship (see Figure 2). These results demonstrated that subjects were able to

discriminate between the levels of pressure while accurately scaling in a ratio level manner.

Thus, the magnitude matching procedure shows clear psychometric advantage over more

traditional methods of scaling. In addition, the separation of response bias from

discriminability may in the future contribute to matching of treatment to patient

characteristics or the prediction of treatment success.

Further research is necessary to delineate factors that affected the response bias

dimension in the present studies. In both the reliability and validity studies, it appeared

that anxiety due to the experimental situation played a role in the study results. However,

because anxiety was not assessed or measured, its role is speculative. The effects of

anxiety and of other factors, such as learning, and the extent to which these can be

experimentally manipulated, should be examined. Similarly, future research needs to

identify factors that may have influenced the lack of demonstrated group differences in

discriminability. For example, the choice of lesser, or further spaced pressures, may

positively influence subject performance. More specific instructions, training, and the

addition of practice sessions may also increase discriminability. Related to these factors is

the issue of stability of performance, which should also be examined using more traditional

psychophysical methods.

In general, the results of the present research are encouraging. The methodology

may applied to a variety of experimental and clinical situations and holds promise for the

clinical assessment of pain conditions and treatment outcome, as well as for future


+ placebo

A treatment

0 no-treatment

log6 log7 log8

log at each pressure level

Figure 2. Log Transformed Variables


.S 0.12

8 0.04

"2 -0.04
C 0




Subject's Name: _____________________ Date: ______

Skin Complexion
1. Do you have very sensitive skin? Yes (Explain) ____________ N
2. Do you sunburn easily? Yes
3. Is your skin very fair, with many freckles? Yes
4. What is your natural hair color? __________
5. Do you have a skin reaction to band-aids or other adhesive tapes? Yes
6. Do you have significant facial scarring due to acne or blemishes? Yes
7. Do you have any birthmarks or other skin discoloration on your face? Yes
8. If male, do you have a beard? Yes

Facial Pain
1. Do you have recurrent or chronic pain in your jaws or face?
(If yes, explain____________)
2. Have you ever had recurrent or chronic pain in your jaws or face?
(If yes, explain _________)

1. Do you have an
(If yes, explain
2. Do you have a

iy heart problems?

cardiac pacemaker?

1. Do you have a known drug allergy to lidocainerug
2. Do you have a known drug allergy to epinephrdocaine?
3. DoIf female, is therave a knowny chance that you could be pregnant?
3. If female, is there any chance that you could be pregnant?


Yes No

Yes No

Yes No

Yes No


Is subject suitable for participation in study? Yes No
Randomized to which study? Test-Retest Validity (Experimental or Control?)


Please answer all questions.


Sex: 0-Male


Ethnicity (Circle one):
1-Caucasian 2-African-American 3-Hispanic 4-Asian
6-Bi-racial (list)______ 7-Other (list)________

Education (Circle highest completed):
High School/GED College: 1 2 3 4 Graduate School: 1
Graduate Program

Are you currently a student?

5-East Indian

2 3 4 5+

0-No 1-Yes, Undergraduate 2-Yes, Graduate


Marital Status (Circle one):
1-Single 2-Married

Total family income (circle one):
1-Under $15,000
7-Over $100,000





Do you have, or have you ever had, a problem with pain in your jaw? 0-No
In another location? 0-No 1-Yes

Does anyone in your family have a problem with chronic pain?
If yes, who?_______

0-No 1-Yes






Instructions to subjects:

"I'm going to ask you to rate the sensation of pressure applied to your jaw with this
pressure device, and also to rate the length of lines presented on these cards. We will
repeat these ratings nine times, three times for each line and pressure. Each rating will
take approximately three seconds. This test is to get an accurate understanding of the pain
and sensitivity of your face.

Judge the sensation and length of the lines on the same number scale. Zero on the
scale represents no sensation, and no length. You can use numbers as large as you want,
but I want you to use larger numbers for longer lines and more painful or uncomfortable
sensations, and smaller numbers for shorter lines and less painful or uncomfortable

Let's practice."

1 Present pressure of 1 foot pound per square inch on wrist bone. Ask for rating.
2 Present card # 3. Ask for rating.
Present pressure of 3 foot pounds per square inch on wrist bone. Ask for rating.
3. Present card #1. Ask for rating.


Al-Hassan, H.K., Ismail, A.I., & Ash, M.M. (1986). Concerns of patients seeking
treatment for TMJ dysfunction. Journal of Prosthetic Dentistry. 56, 217-221.

Barash, P.G., Cullen, B.F., & Stoelting, R.K. (1997). Handbook of clinical anesthesia.
third edition. Philadelphia: Lippincolt-Raven.

Berde, C.B., & Strichartz, G.R. (1994). Local anesthetics. In R.D. Miller (Ed.),
Anesthesia, fourth edition (pp. 489-509). New York: Churchill Livingstone.

Brown, F.F., Robinson, M.E., Riley, J.L., & Gremillion, H.A. (1996). Pain severity,
negative affect, and microstressors as predictors of life interference in TMD patients.
Journal of Craniomandibular Practice. 14(1), 63-70.

Bushnell, M.C., Marchand, S., Tremblay, N., & Duncan, G.H. (1991). Electrical
stimulation of peripheral and central pathways for the relief of musculoskeletal pain.
Canadian Journal of Physiology and Pharmacology. 69, 697-703.

Byl, N., Zellerbach, L.R., & Pfalzer, L.A. (1996). Systemic issues and skin conditions:
Wound healing, oxygen percutaneous drug delivery, burns, and desensitized skin. In
R.S. Myers (Ed.), Saunders manual of physical therapy practice (pp. 585-623).
Philadelphia: W.B. Saunders Company.

Carlo, G.T., Ciancio, S.G., & Seyrek, S.K. (1982). An evaluation ofiontophoretic
application of fluoride for tooth desensitization. Journal of the American Dental
Association. 105, 452-454.

Costello, C.T., & Jeske, A.H. (1995). Iontophoresis: Applications in transdermal
medication delivery. Physical Therapy. 75, 554-563.

de Jong, R.H. (1996). Local anesthetics in clinical practice. In S.D. Waldman & A.P.
Winnie (Eds.), Interventional pain management (pp. 151-166). Philadelphia: W.B.
Saunders Company.

de Wijer, A., Lobbezoo-Scholte, A.M., Steenks, M.H., & Bosman, F. (1995). Reliability
of clinical findings in temporomandibular disorders. Journal of Orofacial Pain. 9,181-

Dougher, M.J. (1979). Sensory decision theory analysis of the effects of anxiety and
experimental instructions on pain. Journal of Abnormal Psychology. 88(2), 137-144.

Duncan, G.H., Feine, J.S., Bushnell, M.C., & Boyer, M. (1988). Use of magnitude
matching for measuring group differences in pain perception. In R. Dubner, G.F.
Gebhart, & M.R. Bond (Eds.), Proceedings of the Vth World Congress on Pain (pp,
383-390). New York: Elsevier Science Publishers.

Dworkin, S. F. (1995). Personal and societal impact of orofacial pain. In J.R. Fricton &
R. Dubner (Eds.), Orofacial pain and temporomandibular disorders (Vol. 21, pp. 15-
32). New York: Raven.

Dworkin, S.F., & LeResche, L. (1992). Research diagnostic criteria for
temporomandibular disorders: Review, criteria, examinations and specifications,
critique. Journal of Craniomandibular Disorders. Facial and Oral Pain. 6, 301-355.

Dworkin, S.F., LeResche, L., & DeRouen, T. (1988). Reliability of clinical measurement
in temporomandibular disorders. Clinical Journal of Pain. 4, 89-99.

Feine, J., Bushnell, M., Miron, D., & Duncan, G. (1991). Sex differences in the
perception of noxious heat stimuli. Pain, 44, 255-262.

Fuller, A. K., & Robinson, M.E. (1995). Perceptual differences between patients with
chronic low back pain and healthy volunteers using magnitude matching and clinically
relevant stimuli. Behavior Therapy. 26, 241-253.

Gangarosa, L.P. (1974). Iontophoresis for surface local anesthesia. Journal of the
American Dental Association. 88, 125-128.

Gangarosa, L.P. (1981a). Defining a practical solution for iontophoretic local anesthesia
of skin. Methods and Findings in Experimental and Clinical Pharmacology. 3(2),83-

Gangarosa, L.P. (1981b). Iontophoretic application of fluoride by tray techniques for
desensitization of multiple teeth. Journal of the American Dental Association. 102,

Gangarosa, L.P. (1982). Iontophoresis in dental practice. Chicago: Quintessence
Publishing Company, Inc.

Gangarosa, L.P. (1988). Electrical medication (iontophoresis): A modality for expanding
dental practice with new therapies. General Dentistry, Sept.-Oct., 402-404.

Gangarosa, L.P., & Mahan, P.E. (1982). Pharmacologic management of TMJ-MPDS.
Ear. Nose and Throat. 61, 30-41.

Gangarosa, L.P., Ozawa, A., Onkido, M., Shimomura, Y., & Hill, T.M. (1995). Journal
of Dermatology. 22 (11), 865-875.

Gracely, R.H., & Reid, K.I. (1995). Orofacial pain measurement. In J.R. Fricton & R.
Dubner (Eds.), Orofacial pain and temporomandibular disorders (Vol. 21, pp. 117-
143). New York: Raven.

Graff-Radford, S.B., Reeves, J.L., Baker, R.L., & Chiu, D. (1989). Effects of
transcutaneous electrical nerve stimulation on myofascial pain and trigger point
sensitivity. Pain, 37, 1-5.

Green, C.S., & Marbach, J.J. (1982). Epidemiological studies of mandibular dysfunction:
A critical review. Journal of Prosthetic Dentistry. 48, 184-190.

Green, D.M., & Swets, J.A. (1966). Signal detection theory and psychophysics. New
York: Wiley.

Greenbaum, S.S., & Bernstein, E.F. (1994). Comparison of iontophoresis of lidocaine
with a eutectic mixture of lidocaine and prilocaine (EMLA) for topically administered
local anesthesia. Journal of Dermatology and Surgical Oncology. 20, 579-583.

Heft, M.W., & Parker, S.R. (1984). An experimental basis for revising the graphic rating
scale for pain. Pain, 19, 152-161.

Irsfeld, S., Klement, W., & Lipfert, P. (1993). Dermal anesthesia: Comparison of EMLA
cream with iontophoretic local anesthesia. British Journal of Anaesthesia., 71, 375-

Jaeger, B., & Reeves, J.L. (1986). Quantification of changes in myofascial trigger point
sensitivity with the pressure algometer following passive stretch. Pain, 27, 203-210.

Jensen, K., Anderson, H.O., Olesen, J., & Lindblom, U. (1986). Pressure-pain threshold
in human temporal region. Evaluation of a new pressure algometer. Pain, 25 313-

Jensen, R., Rasmussen, B.K., Pedersen, B., Lous, I., & Olesen, J. (1992). Cephalic
muscle tenderness and pressure pain threshold in a general population. Pain, 48, 197-

Kassan, D.G., Lynch, A.M., & Stiller, M.J. (1996). Physical enhancement of
dermatologic drug delivery: Iontophoresis and phonophoresis. Journal of the
American Academy of Dermatology. 34, 657-666.

Lark, M.R., & Gangarosa, L.P. (1990). Iontophoresis: An effective modality for the
treatment of inflammatory disorders of the temporomandibular joint and myofascial
pain. Journal of Craniomandibular Practice. 8(2), 108-119.

List, T., Helkimo, M., & Falk, G. (1989). Reliability and validity of a pressure threshold
meter in recording tenderness in the masseter muscle and the anterior temporalis
muscle. Journal of Craniomandibular Practice. 7(3), 223-229.

List, T., Helkimo, M., & Karlsson, R. (1991). Influence of pressure rates on the
reliability of a pressure threshold meter. Journal of Craniomandibular Disorders.
Facial and Oral Pain. 5, 173-178.

Maloney, J.M., Bezzant, J.L., Stephen, R.L., & Petelenz, T.J. (1992). lontophoretic
administration oflidocaine anesthesia in office practice: An appraisal. Journal of
Dermatology and Surgical Oncology. 18, 937-940.

Malow, R.M. (1981). The effects of induced anxiety on pain perception: A signal
detection analysis. Pain, 11, 397-405.

Marks, L.E (1991). Reliability of magnitude matching. Perception and Psychophysics,
49(1), 31-37.

Marks, L.E., Szczesiul, R., & Ohlott, P. (1986). On the cross-modal perception of
intensity. Journal of Experimental Psychology: Human Perception and Performance.
12(4), 517-534.

McMillan, A.S., & Blasberg, B. (1994). Pain-pressure threshold in painful jaw muscles
following trigger point injection. Journal of Orofacial Pain. 8(4), 384-390.

McMillan, A.S., & Lawson, E.T. (1994). Effect of tooth clenching and jaw opening on
pain-pressure threshold in the human jaw muscles. Journal of Orofacial Pain. 8(3),

Ohrbach, R., & Gale, E.N. (1989a). Pressure pain thresholds, clinical assessment, and
differential diagnosis: Reliability and validity in patients with myogenic pain. Pain
39, 157-169.

Ohrbach, R., & Gale, E.N. (1989b). Pressure pain thresholds in normal muscles:
Reliability, measurement effects, and topographical differences. Pain, 37 257-263.

Oshima, T., Kashiki, K., Toyooka, H., Masuda, A., & Amaha, K. (1994). Cutaneous
iontophoretic application of condensed lidocaine. Canadian Journal of Anesthesia.
41(8), 677-679.

Price, D. (1988). Psychological and Neural Mechanisms of Pain. New York: Raven

Price, D., & Harkins, S.W. (1992). Psychophysical approaches to pain measurement and
assessment. In D.C. Turk & R. Melzack (Eds.), Handbook of pain assessment (pp.
111-134). New York: Guilford Press.

Reeves, J.L., Jaeger, B., & Graff-Radford, S.B. (1986). Reliability of the pressure
algometer as a measure ofmyofascial trigger point sensitivity. Pain, 24, 313-321.

Reid, K.I., Dionne, R.A., Sicard-Rosenbaum, L., Lord, D., & Dubner, R.A. (1994).
Evaluation of iontophoretically applied dexamethasone for painful pathologic
temporomandibular joints. Oral Surgery, Oral Medicine, and Oral Pathology. 77,

Reid, K.I., Gracely, R.H., & Dubner, R.A. (1994). The influence of time, facial side, and
location on pain-pressure thresholds in chronic myogenous temporomandibular
disorder. Journal of Orofacial Pain. 8(3), 258-265.

Rollman, G.B. (1977). Signal detection theory measurement of pain: A review and
critique. Pain 3, 187-211.

Russo, J., Lipman, A.G., & Comstock, T.J. (1980). Lidocaine anesthesia: Comparison of
iontophoresis, injection, and swabbing. American Journal of Hospital Pharmacology.

Schumacher, R., & Velden, M. (1984). Anxiety, pain experience, and pain report: A
signal detection study. Perceptual and Motor Skills. 58, 339-349.

Singh, S., & Singh, J. (1993). Transdermal drug delivery by passive diffusion and
iontophoresis: A review. Medicinal Research Reviews. 13(5), 569-621.

Speculand, B., & Goss, A.N. (1985). Psychological factors in temporomandibular joint
dysfunction pain. International Journal of Oral Surgery. 14, 131-137.

Stevens, J.C., & Marks, L.E. (1980). Cross-modality matching functions generated by
magnitude estimation. Perception and Psychophysics. 27(5), 379-389.

Stockstill, J., Gross, A., & McCall, W.D. (1989). Interrater reliability in masticatory
muscle palpation. Craniomandibular Disorders. Facial and Oral Pain. (3), 143-146.

Svensson, P., Arendt-Nielsen, L., Nielsen, H., & Larsen, J.K. (1995). Effect of chronic
and experimental jaw muscle pain on pain-pressure thresholds and stimulus-response
curves. Journal of Orofacial Pain. 9, 347-356.


Weisenberg, M., Anram, 0., Wolf, Y., & Rapheli, N. (1984). Relevant and irrelevant
anxiety in the reaction to pain. Pain, 20, 371-383.

Wetherill, G.B., & Levitt, H. (1965). Sequential estimation of points on a psychometric
function. The British Journal of Mathematical and Statistical Psychology. 18 (Pt 1),


Felicia F. Brown received an undergraduate degree in psychology and

anthropology from Tufts University in 1990. She was employed as a neuropsychometrist

for the University of California at San Diego until entering the doctoral program in

Clinical and Health Psychology at the University of Florida in 1992. She received her

master of science degree in 1994, following completion of her thesis titled, Pain Severity.

negative affect, and microstressors as predictors of life interference in TMD patients. Ms.

Brown is receiving her clinical internship training at McLean Hospital in Belmont,

Massachusetts. She will graduate with a doctorate in clinical and health psychology with

an area of concentration in medical psychology.

I certify that I have read this study and that in my opinion it conforms to
acceptable standards of scholarly presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.

Michael E. Robinson, Chair
Associate Professor of Clinical and Health

I certify that I have read this study and that in my opinion it conforms to
acceptable standards of scholarly presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.

Lind"/R. Shaw -
Associate Professor of Rehabilitation Counseling

I certify that I have read this study and that in my opinion it conforms to
acceptable standards of scholarly presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.

CynqA D. Belar
Professor of Clinical and Health Psychology

I certify that I have read this study and that in my opinion it conforms to
acceptable standards of scholarly presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.

iM4 ei l^^_ion
Henry rrdlo
Associate Pr fessor of Oral and Maxillofacial
Surgery and Diagnostic Sciences

I certify that I have read this study and that in my opinion it conforms to
acceptable standards of scholarly presentation and is full adequate, in scope and quality,
as a dissertation for the degree of Doc or of Philosophy.

Duane E Dede
Assistant Professor of Clinical and Health

This dissertation was submitted to the Graduate Faculty of the College of Health
Professions and to the Graduate School and was accepted as partial fulfillment of the
requirements for the degree of Doctor of Philosophy.

May 1998 "
Dean, College of Health Professions

Dean, Graduate School

11II 111 1111 I I llllU l lii 111111 II M I iGI
3 1262 08555 3153

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