Comparison of methods for measuring root and mucogingival sensitivity

Comparison of methods for measuring root and mucogingival sensitivity Benjamin W. Walline,a Joshua G. Wagner, BS,a David B. Marx, PhD,b and Richard A. Reinhardt, DDS, PhD,c Lincoln, Neb UNIVERSITY OF NEBRASKA

Objective. The aim of this study was to compare the variability of measurements of root and mucogingival sensitivity over a 24-hour period.

Study design. Sixteen individuals (46.8 ± 3.2 years old) were randomly tested for pain thresholds with calibrated electrical stimulation of the root and adjacent mucosa (electric pulp tester), pressure on mucosa (pressure-sensitive probe), and cold on the root (experimental thermocoupler probe) at baseline and after 4, 8, and 24 hours. Variability between and within subjects was estimated by using analysis of variance for random effects. Results. Intrasubject variability was highest for electric testing of the root and lowest for cold testing of the root across time. Of all subjects, 93% fell within 5°C at all periods for the cold stimulation/moderate pain threshold. Conclusions. Calibrated cold stimulation of root areas appears to provide the most sensitive measure to assess therapeutic interventions to control cervical dental pain because of low intrasubject variability in untreated patients.

(Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;90:641-6)

The dental practitioner is confronted with the need to assess and treat discomfort in root and mucogingival areas. Two common conditions are dentin hypersensitivity and mucogingival sensitivity. The ability to quantify patient sensations to stimuli in these areas allows the magnitude of the condition or therapeutic management to be more accurately measured. However, the variability of these measures in health must be known to understand their relevance during patient complaints and treatment. The 3 commonly used stimuli for root and mucosal sensitivity testing are electricity, pressure, and cold. Electric dental pulp stimulation has been widely used in pain models and has been reported to be consistently sensitive.1,2 Studies have shown that hand-held electric pulp testers can be expected to provide reproducible results when testing hard and soft tissue sites.3,4 By using a device similar to the one in this study, Dal Santo et al3 found a 95% chance of having a difference of less than 10 instrument units at 2 time points. These results were similar for consecutive same-day trials and corresponding trials on different days. The value of electric stimulation for dentin sensitivity testing remains controversial5 and perhaps better suited for aDental Student, University of Nebraska Medical Center, College of Dentistry. bProfessor, Biometry, University of Nebraska. cProfessor, Surgical Specialties, University of Nebraska. Received for publication Dec 9, 1999; returned for revision Feb 25, 2000; accepted for publication Jun 2, 2000. Copyright © 2000 by Mosby, Inc. 1079-2104/2000/$12.00 + 0 7/15/109659 doi:10.1067/moe.2000.109659

measuring pulpal vitality than dentin hypersensitivity.6 The value of electric testing for mucogingival sensitivity seems logical, but needs further evaluation as is partially addressed in this study. Electric testing of the gingival tissue also has been performed as a means for identifying a false positive pulp test, in which the pulp test causes response at a level above the patient’s tissue response.7 The rationale for using pressure testing to evaluate soft tissue sensitivity is clear. Pain and sensory thresholds to tactile stimulation appear to have less variability on the gingiva/oral mucosa than on skin or tooth structure, although the site of stimulation must be moved slightly to avoid receptor fatigue or sensitization.8 The advent of pressure-sensitive probes allows quantifications of soft tissue stimulation. Pain threshold assessments have been performed with a modified electronic probe that steadily delivered an increasing force.9 Variations in levels of mucogingival inflammation can cause variations in responses to probing pressure. Sensitivity to thermal stimuli, especially cold, appears to be the most common complaint of patients with recession.10 Cold stimuli, like ethyl chloride, are reported to produce temperatures of 14°C to 20°C on the external surface of the tooth,11 but short exposure (1-2 seconds) failed to produce a relationship between surface temperature intensity and perceptual or neural response.12 Studies that use cold stimulation with calibrated temperatures for longer duration are rare. Water of known temperatures flowed onto exposed dentin has been used,13 which simulates “real world” cold liquid irritation. However, volume and flow were difficult to 641

642 Walline et al

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY November 2000

Fig 1. Diagram of thermocoupler cold testing device. Fluid is circulated from pump through thermocoupler to cool (or heat) liquid, then through insulated tubing to probe where it cools metal tubing and tip, and finally back to pump (unlabeled arrows). Digital control unit allows programming of target temperature and then signals thermocoupler. Probe temperatures are monitored by control unit through thermistor at probe tip.

control. Thermoelectric devices allow precise temperatures to be applied through metal probes.6,14 Our group has developed a cold probe based on thermocoupler technology. Circulating cold liquid cools a metal probe fitted with a thermistor to measure temperature delivery from 25°C to 0°C, allowing for 10-minute testing of 11 temperatures in this range. Shorter times are necessary for fewer target temperatures. Evaluation of the patient’s response to stimulation is the other critical part of oral sensitivity quantitation. A continuous visual analog scale (VAS), a line along which the patient can rate (mark) increasing sensation/pain, is widely used. An acceptable alternative is the use of simple intensity verbal descriptors (eg, no pain, mild pain, moderate pain) after stimulation.10,15 Defining the point (threshold) during increasing stimulation at which the sensation progresses from no pain to mild pain (or from mild pain to moderate pain) could be used to quantitate the level of stimulation necessary to cause discomfort. The use of multiple stimuli and outcome measures may be useful in providing a clearer interpretation of disease etiology and therapy efficacy.16 Investigations of reproducibility of methods related to clinical situations are also critical in this process.10 The purpose of

this study was to compare various stimuli and patient perception instruments, which may be used by the dentist to test cervical root/mucogingival sensations, with regards to their variability across a 24-hour period. This information would be helpful in subsequently determining effective approaches to quantitate oral pain and corrective therapy in the dental setting.

MATERIALS AND METHODS Potential subjects were recruited by college advertising, then screened for at least 1 tooth (test tooth) with ≥2 mm recession and a painful reaction to an ethyl chloride-soaked pellet placed on the exposed root surface. All subjects were required to be in good health and were required to sign an Institutional Review Board Informed Consent. This convenience sample included college staff, students, and patients (2 male and 14 female subjects), all of whom were white with a mean age of 46.8 ± 3.2 years. Current medications included estrogen/progesterone (n = 6), birth control pills (n = 3), antihistamines (n = 3), 1 aspirin per day (n = 3), angiotensin-converting enzyme inhibitor (n = 1), antidepressant (n = 1), synthetic thyroid (n = 1), and cholesterol-reducing statin (n = 1). Before testing, an oral examination was performed consisting of peri-

Walline et al 643

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 90, Number 5

Table I. Mean outcome values for tests at each period Test Electric root Electric mucosa Pressure mucosa/mild pain Pressure mucosa/moderate pain Cold root/mild pain Cold root/moderate pain

Baseline 3.4*

36.8 ± 34.5 ± 4.6* 43.1 ± 4.5† 65.3 ± 5.3† 16.2 ± 1.2‡ 9.8 ± 1.3‡

4 Hours

8 Hours

24 Hours

33.8 ± 2.5 36.9 ± 4.2 33.8 ± 3.4 53.3 ± 4.5 16.4 ± 1.3 12.3 ± 1.4

32.8 ± 3.0 34.4 ± 4.1 33.1 ± 3.5 52.0 ± 6.3 15.8 ± 0.9 13.0 ± 1.1

40.9 ± 2.9 40.6 ± 3.5 30.0 ± 3.5 54.7 ± 5.9 16.9 ± 1.2 13.2 ± 1.5

*Mean

digital readout on electric pulp tester (± standard error of the mean). grams pressure (± SEM). ‡Mean °C (± SEM). †Mean

odontal probing, caries detection, and screening for oral pathosis (mucosal and gingival). Subjects were excluded from the study if they had extensive restorations, active caries, orthodontic treatment, or periodontal pathosis (>4 mm probing depth or bleeding on probing) near the area of the test tooth. A periapical radiograph was made of the test tooth to exclude apical radiolucencies, root canal treatment, caries, or restorations near the recession. No dental therapy had been performed in the preceding 3 months. Test teeth included 7 mandibular incisors, 3 maxillary molars, 2 maxillary canines, 2 maxillary premolars, 1 mandibular canine, and 1 mandibular molar. Stimulations evaluated for the variability of subject response included electric, cold thermal, and pressure tests performed (at the same time of day) at baseline and after 4, 8, and 24 hours. The sequence of tests was varied by using Latin squares randomization. Before the sequence began, subjects were allowed to experience the contact of the testing instruments to distinguish this from actual stimulation. Electric tests on both the test root and adjacent mucogingival junction area were performed by using an electric pulp tester (Analytic Technology, Richmond, Va). After drying the area, electric pulp testing was done on the facial root surface, ensuring that the tip was contacting root and not gingiva while coated with a thin layer of toothpaste used as the conduction media. Some slight overlap of the enamel was possible. The pulp tester also was applied at the mucogingival junction adjacent to the test tooth; the subjects were instructed to raise a hand the moment they experienced a sensation, and the digital readouts were recorded. For both tests the voltage was increased at a rate setting of 2. Cold testing was performed by using a prototype thermocoupler cold testing device with a thermistor built into the probe tip (Fig 1). The temperature was slowly decreased in 2.5°C increments from 25°C to 0°C by circulating fluid through the metal probe. The probe was placed on the root surface in the area of recession (approximately 1 mm2 of metal-root contact,

no conduction media) at each temperature interval (2.5°C) for 5 seconds each or until pain was felt (<5 seconds). Subjects were instructed to raise a hand the moment they experienced what they perceived as a cold sensation of mild or moderate pain (as compared with no pain). The threshold at which the subject experienced mild and moderate pain was recorded. The subjects were instructed that they could stop testing at any time. Patients also marked a pain response on a continuous 10 cm VAS when they requested testing be discontinued (typically the moderate pain threshold). Pressure testing on soft tissue occurred just apical to the mucogingival junction on the facial aspect of the test tooth. Testing was done with a modified probe tip (0.35 mm in diameter) adapted to a pressure-sensitive device capable of delivering pressures ranging from 10 to 100 grams (Vine Valley Research, Middlesex, NY). Pressures in 10-gram increments were sequentially applied to the mucosa. Subjects were instructed to differentiate between pressure (no pain) and mild or moderate pain. Subjects also marked on a VAS chart the different gram increments. The minimal gram force needed to induce what the subjects perceived as mild and moderate pain was recorded as threshold levels. Mean data for each test were calculated to describe general response levels and to allow comparisons with other studies, with the caveat that some tests did not include interval data (electric and VAS), so the interpretation of their means should be made with caution. Threshold levels for electric (first sensation), cold (temperature at mild and moderate pain), and pressure tests (lowest force to cause mild and moderate pain), along with VAS values for cold and pressure tests, were compared (by using both raw and rank transformed data for electric and VAS tests) among subjects and among time periods for each subject with variance component estimation (analysis of variance for random effects). Intersubject variability (SUB VAR) was compared with residual variability (RES VAR; intrasubject variability of outcomes from time to time) with the construction of the ratio SUB VAR/RES VAR to allow a dimensionless

644 Walline et al

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY November 2000

Table II. Test outcomes according to intersubject variability/residual variability Test

Subject variability/residual variability

Electric root Electric mucosa Pressure mucosa/mild pain Pressure mucosa/moderate pain Pressure mucosa/VAS Cold root/mild pain Cold root/moderate pain Cold root/VAS *Rank

0.00/136.84 109.47/142.30 102.14/128.13 197.20/250.00 0.06/0.15 11.98/7.56 13.80/11.43 0.003/0.308 46.67/110.39*

= = = = = = = = =

0.00 0.77 0.80 0.79 0.40 1.58 1.21 0.01 0.41

F Value

Significance

0.96 4.08 4.19 4.16 2.64 7.31 5.66 1.09 2.62

NS P = .0001 P = .0001 P = .0001 P = .0007 P = .0001 P = .0001 NS P = .0079

transformed data.

Table III. Percentage subjects within 20% range of measurements Test

Percentage subjects

Electric root (n = 16) Electric mucosa (n = 16) Pressure mucosa/mild pain (n = 16) Pressure mucosa/moderate pain (n = 15) Cold root/mild pain (n = 16) Cold root/moderate pain (n = 14)

25.0* 43.8* 56.3† 53.3† 75.0‡ 92.9‡

*Within

16 point range on pulp tester. 20 grams force range. ‡Within 5oC range. †Within

evaluation of how much of the total variability of each test was caused by intersubject variability versus intrasubject variability. For instance, a ratio above 1 would indicate more variability between subjects than within subjects from time to time, or the most consistency from time to time. This would be a valuable attribute in identifying small changes in responses to therapy in an individual. F values also were calculated (higher F values would indicate more intersubject variability compared with intrasubject variability).

RESULTS The order in which the tests were conducted during each period had no influence on the outcome values. The mean outcome measures for each test (electric stimulation readout at first sensation; pressure [grams] at mild and moderate mucosal pain thresholds; temperature [°C] at mild and moderate root pain thresholds) across time are presented in Table I. Mean interval data (pressure and cold thresholds) were not significantly different across time, that is, the means were no different than what would be expected from intersubject variability. Variability ratios and values are reported in Table II. Electric stimulations of the root produced the least consistent response across time within subjects. Sensation to electric stimulation of mucosa and pain

thresholds to pressure stimulation of mucosa were more consistent across the 24-hour test period. Pain responses to calibrated cold stimulation were the most consistent across time. Using the VAS measurement when the patient requested testing be stopped proved to be less consistent than specific mild or moderate perceived-pain thresholds. In all but 1 procedure (VAS evaluation of cold stimulation), the ratio of the variance components was quite similar for raw data compared with rank-transformed data. Hence, only the raw data results were presented for all procedures except VAS cold stimulation, where both were presented. Percentages of subjects consistently falling (at each time period) within a 20% segment of the entire range of all measurements that could be applied are reported in Table III. One subject in the pressure mucosa test and 2 subjects with the cold stimulation/moderate pain test did not respond within the range of all stimuli for all time points, so they were not included in this analysis. The results mirrored the variability ratios, with electric stimulation of the root producing the least consistent results. Electric and pressure stimulations of mucosa showed intermediate variability, and cold tests had the most subjects within the 20% range. In fact, all but 1 subject among those responding with a moderate pain perception at all sessions were within 5°C at all periods.

DISCUSSION The order in which stimuli are delivered for cervical sensitivity studies has been considered important.10 However, alternating the order by using Latin squares in this study did not affect any of the outcome measurements. This is consistent with the Pantera et al17 finding that cold application did not alter subsequent electric pulp testing. A variety of physiologic events may decrease pulp sensitivity, including adrenaline,12 exercise,18 hypertension,19 and orthodontic forces.20 Diurnal variations in pain thresholds also are of

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 90, Number 5

concern.21 These variables, therefore, were controlled by exclusion criteria and study design. Mean values for electric root sensitivity reported in Table I were similar or higher than reports of sensation thresholds on enamel by using a pulp tester similar to the one used in our study.3,4 The difference in conducting surface (dentin versus enamel), the older mean age, and the relatively high number of posterior teeth in this study may have accounted for some of the higher thresholds, although no pattern could be determined. Gingival thresholds between 30 and 403 were similar to those in Table I. Nineteen percent of sites showed electrical pulp readings consistently above the gingival values, where Peters et al7 suggested that pulpal pathosis could be present. However, all these teeth responded normally to cold, indicating pulp vitality.7 The pressure/mild pain thresholds on mucosa were lower than reported gingival sulci thresholds,9 suggesting mucosa is a more sensitive pressure target. Mean pain thresholds with known temperature stimulation of exposed dentin have been reported near 30°C7 down to 24°C.14 Because the lower of these values represents indoor air temperature, these individuals were highly sensitive to cold, whereas our patients generally responded with pain to temperatures around the level of ethyl chloride or ice water.11 These individuals, therefore, were fairly tolerant of most intraoral temperatures. In other words, they presented a relatively healthy response to gingival recession. Although mean outcome measurements provide interesting data on the relative thresholds of patient response, group means obscure the intrasubject variability, which is important in judging the level of individual pathosis or drug therapy improvement.22 Even when intersubject peak pain means have been reported to be consistent across time, some subjects had increasing thresholds and others had decreasing thresholds.23 Results reported in Table II indicate that intrasubject pain response variability was highest with electric stimulation of the root and least variable with cold stimulation of the root when the intensity verbal descriptions of “mild pain” and “moderate pain” were used to determine thresholds. However, VAS measurements for cold stimulation were more variable within subjects. The rationale for the statistical approach used was that if a particular test is going to be effective in determining a change between baseline (normal) and a clinical situation (disease or therapeutic intervention), it should have a small amount of variability over time under normal conditions. Because variability is scale dependent, one cannot simply compare variances of different procedures. In addition, if there is no variability at all, then the procedure will not effectively

Walline et al 645

measure differences over time. Hence, an ideal test would have high variability among subjects when compared with variability within subjects. Therefore, we estimated the variance within subjects and between subjects with analysis of variance for random effects. The ratio of these variance components (between subjects divided by within subjects) was used as a measure of effectiveness of the test, with higher ratios (above 1) indicating the least variable tests across time. No serial (time order) correlation was found. Variance components for within and between subjects were calculated for both the raw and rank transformed data because of the lack of interval data for some tests (electric and VAS), but no major changes in the level of variability were noted. As a way to further portray the variability of each test, a small segment (20%) of the entire range of possible measurements for that test was selected to define low fluctuation across time. The percent of subjects within the 20% range of all measurements at all periods paralleled the intrasubject variability pattern (Tables II and III). Although electrical stimulation of enamel has been shown to produce pain threshold readings within 10 units 95% of the time,3 dentin stimulation thresholds were within 16 units (20%) at all 4 time periods only 25% of the time in our study. The additional rigor of being within a small range at 4 rather than 2 times may account for some of these differences. Previous reports6 of cold stimulation causing pain sensation within a 3°C range over 2 times with a 65% frequency are comparable with causing mild pain within a 5°C range over 4 times with 75% frequency in this study. The finding that the moderate pain threshold was within a 5°C range over all 4 measurement periods >90% of the time also is supportive of the low variability of these tests. The fact that 2 subjects did not reach the moderate pain threshold at some periods reinforces the need to screen for inclusion criteria to carefully define the highest threshold to be used. There are several implications concerning the use of these tests in future drug therapy trials or dental office therapy monitoring. First, electric stimulation of the exposed dentin may not be sensitive enough to detect changes because of the high intrasubject variability. Second tests with intermediate variability (electric and pressure on mucosa) would benefit from a runin/washout period before clinical trials to establish sensitivity levels and to eliminate erratic or inconsistent responders.5 Finally, cold stimulation with known and clinically relevant temperatures may provide the most sensitive measure of therapy effect. These cold tests can be performed in 10 minutes (15 minutes for all tests) by using simple pain descriptors to set thresholds (mild pain

646 Walline et al

and moderate pain). The prototype thermal instrument used in our study also could be modified to allow a small amount of water of known temperature to contact the tooth, thereby avoiding metal contact sensitivity and increasing “real world” simulation. The variability characteristics described in this article may be helpful in designing future clinical trial and office protocols to evaluate the treatment of cervical/mucogingival pain. We thank Julie Layton for her clinical assistance and Deb Dalton for preparing the manuscript. We also acknowledge financial support from the University of Nebraska Medical Center College of Dentistry. REFERENCES 1. McCormack K, Brune K. Dissociation between the antinociceptive and anti-inflammatory effects of the nonsteroidal antiinflammatory drugs: a survey of their analgesic efficacy. Drugs 1991;41:533-47. 2. Guasti L, Cattaneo R, Rinaldi O, Rossi MG, Bianchi L, Gaudio G, et al. Twenty-four-hour noninvasive blood pressure monitoring and pain perception. Hypertension 1995;25:1301-5. 3. Dal Santo FB, Throckmorton GS, Ellis E III. Reproducibility of data from a hand-held digital pulp tester used on teeth and oral soft tissue. Oral Surg Oral Med Oral Pathol 1992;72:103-8. 4. Cameron WA, Pairman JS, Orchardson R. The effect of an electronic analgesia device on dental pain thresholds. Anesth Pain Control Dent 1993;2:171-5. 5. Holland GR, Narhi MN, Addy M, Gangarosa L, Orchardson R. Guidelines for the design and conduct of clinical trials on dentine hypersensitivity. J Clin Periodontol 1997;24:808-13. 6. Orro M, Truong T, DeVizio W, Miller S, Chu T-C, Boylan D. Thermodontic stimulator—a new technology for assessment of thermal dentinal hypersensitivity. J Clin Dent 1994;5:83-6. 7. Peters DD, Baumgartner JC, Lorton L. Evaluation of the positive and negative responses to cold and electrical pulp tests. J Endod 1994;20:506-11. 8. Svensson P, Bjerring P, Arendt-Nielsen L, Kaaber S. Variability of argon laser-induced sensory and pain thresholds on human oral mucosa and skin. Anesth Prog 1991;38:79-83. 9. Heins PJ, Karpinia KA, Maruniak JW, Moorhead JE, Gibbs CH.

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY November 2000

10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

20. 21. 22.

23.

Pain threshold values during periodontal probing: assessment of maxillary incisor and molar sites. J Periodontol 1998;68:812-8. Gillam DG, Newman HN. Assessment of pain in cervical dentinal sensitivity studies: a review. J Clin Periodontol 1993;20:383-94. Trowbridge HO, Franks M, Korostoff E, Emling R. Sensory response to thermal stimulation in human teeth. J Endod 1980;6:405-12. Ahlquist M, Franzen O. Pulpal ischemia in man: effects on detection threshold, A-delta neural response and sharp dental pain. Endod Dent Traumatol 1999;15:6-16. Muzzin KB, Johnson R. Effects of potassium oxalate on dentin hypersensitivity in vivo. J Periodontol 1989;60:151-8. Thrash WJ, Jones DL, Dodds WJM. Effect of fluoride solution on dentinal hypersensitivity. Amer J Dent 1992;5:299-302. Gillam DG, Bulman JS, Newman HN. A pilot assessment of alternative methods of quantifying dental pain with particular reference to dentin hypersensitivity. Comm Dent Health 1997;14:92-6. Coda B, Tanaka A, Jacobson RC, Donaldson G, Chapman CR. Hydromorphone analgesia after intravenous bolus administration. Pain 1997;71:41-8. Pantera Jr TA, Anderson RW, Pantera CT. Reliability of electric pulp testing after pulp testing with dichlorodifluoromethane. J Endod 1993;19:312-4. Droste C, Greenlee MW, Schreck M, Roskamm H. Experimental pain thresholds and plasma beta-endorphin levels during exercise. Med Sci Sports Exerc 1991;23:334-42. Falcone C, Auguadro C, Sconocchia R, Angoli L. Susceptibility to pain in hypertensive and normotensive patients with coronary artery disease: response to dental pulp stimulation. Hypertension 1997;30:1279-83. Hall CJ, Freer TJ. The effects of early orthodontic force application on pulp test responses. Austral Dent J 1998:43:359-61. Taylor PP. The evaluation and use of the high frequency vitalometer. Oral Surg Oral Med Oral Pathol 1953;6:1020-4. Chapman CR, Hill HF, Saeger L, Gavrin J. Profiles of opioid analgesia in humans after intravenous bolus administration: alfentanil, fentanyl and morphine compared on experimental pain. Pain 1990;43:47-55. Mengel MKC, Stiefenhofer AE, Jyväsjärvi E, Kniffki K-D. Pain sensation during cold stimulation of the teeth: differential reflection of Aδ and C fibre activity? Pain 1993;55:159-69.

Reprint requests: Richard A. Reinhardt, DDS, PhD UNMC College of Dentistry 40th and Holdrege Lincoln, NE 68583-0757 [email protected]