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Reports of Pain After Dental Treatment, Electrical Tooth Pulp Stimulation, and Cutaneous Shock
j
r r r m y jjffi j|
A R T IC L E S
Reports of pain after dental treatment, electrical tooth pulp stimulation, and cutaneous shock Robert K. K lepac, PhD Joh n Dow ling, PhD G regory Hauge M arvin M cDonald
To determine if dental treatment is relatively painless and if certain factors contribute to apprehension of dental treatment, a questionnaire was given to dental patients and subjects of mild laboratory stressors. Responses of these groups were then compared.
r
Jomparisons of particularly fear ful and nonfearful dental patients have repeatedly implicated pain as a factor important to dental apprehen sion.1 Studies supporting this infer ence include: reports from largesample surveys on subjects’ percep tion of the origins of their fear2; inter views with maximally and m ini mally fearful subjects3; ratings of pa tients actually undergoing dental tre a tm e n t4,5; and re a c tio n s to p s y c h o p h y s ic a l te s ts of p ain threshold6-7 and tolerance.7 Treat ments aimed at increasing tolerance to pain have been proposed8 and were effective in case studies9 in re ducing avoidance of dentistry. Con sidered togeth er, these studies 692 ■ JADA, Vol. 100, May 1980
suggest that pain, although not the sole or most frequent2,4 factor in den tal apprehension, is clearly among the important factors in understand ing fear and avoidance of dental treatment. In a magazine article on dental ap prehension, Eric Jackson was quoted as saying, “there’s not very much pain in dentistry any more.”10 This point has been made by several den tists in audiences we have addressed and reflects the genuine puzzlement over the seeming paradox—how can a situation that is virtually painfree lead to so many studies that impli cate pain as a major factor in dental apprehension? In fact, hard data do not exist to
support the assumption of painless ness in dental treatment: the assump tion apparently is based on dentists’ observations of patients during treatment, and commentators’ sub jective evaluation of their experi ences with dental treatment. The purpose of this paper is to report on a study that assesses the characteris tics and intensity of pain experi enced during dental treatment by comparing patients’ reports on an es tablished pain questionnaire to re ports of subjects undergoing con trolled laboratory pain. M eth o d
Subjects A total of 58 student volunteers were randomly assigned to receive shock to either an arm or a tooth. The sam ple of dental patients was drawn from a pool created when ten dentists were asked to have as many patients as were willing (up to 33 per dentist) co m p le te a q u e s tio n n a ir e im m ediately after their dental ap pointments. A total of 139 usable questionnaires were returned; most
A R T IC L E S
Table ■ M ean scores on questionnaires on pain. Ratings of paint
Scores on Melzack-McGill Questionnaire
No. Pain group
(M/F)
Age
Sensory*
Affective
Evaluative
Miscellaneous*
Total
Present pain intensity*
Worst dental treatment
Dental treatment Tooth shuck Arm shock
17/12 14/15 11/18
21.7 20.4 20.6
9.2 (a) 14.9 (b) 12.7 (b)
1.0 1.6 0.7
1.2 1.6 1.3
2.8 (a) 4.6 (b) 4.6 (b)
14.1 (a) 22.5 (b) 19.3
1.1 (a) 1.9 (b) 1.8 (b)
2.9 3.4 2.8
‘ Analysis of variance of this variable showed difference in the group of at leastP < .05. Numbers in each colum n followed by letters in parentheses differ a tP < .05 (Newman-Keuls tests). tR atings: 0 = none, 5 = excruciating.
of these (113) came from four den tists. Because reports of pain have been found to vary systematically with age,4 a sample of 29 patients was selected randomly from those within the age range of our sample of college students. Mean ages and male to female ratios appear in the Table.
Instruments and apparatus Tooth pulp stimulation was deliv ered by a DC stimulator (Nuclear, Chicago) modified via a series of potentiometers to permit the ex tremely low current levels and fine increments required. Stimuli were 500 msec trains of 10-msec unipolar pulses presented at a rate of 50 pulses per second. The anode was a conduc tive rubber electrode, 3-mm square, embedded in a plastic probe held by the subject against the incisal edge of a healthy maxillary incisor. A groove filled with electrode paste facilitated electrical contact that was monitored continuously on an oscilloscope. The cathode (Beckman EMG electrode) was attached to the left cheek. These arrangements were patterned after those suggested by M artin and Chapman.11 Cutaneous stimulation was deliv ered by a custom-built, constantcurrent AC stimulator capable of de livering 0 to 21 mA in increments of 0.5 mA. Stimuli of 0.5-sec duration were presented through concentric saline electrodes to the volar surface of the nonpreferred forearm just above the wrist. The contact between electrode and subject was prepared to yield 5,000 (plus or minus 500) ohms inpedance. The apparatus and preparation is that recommended by Tursky.12 The Melzack-McGill Pain Ques tionnaire (MPQ) was used to gather reports on pain. The main portion of the MPQ appears in the Illustration. Subjects were asked to circle words that accurately described their expe riences. The subject did not need to choose a word from each group,
however, only one word from any numbered group should have been circled. As used in this study, if no word was chosen from a group, that group scored 0. If a word was chosen, the rank of that word was entered for that item’s score. For example, if a subject did not select a word from
group 1, the score for that item equaled 0; if “flickering” were cir cled, the score equaled 1; the selec tion of “quivering” scored 2; and selection of “ pulsing” scored 3. Scores for items one to ten were then summed to form a score for the sen sory dimension; items 11 to 15 were
Some of the w o r d s b e l o w d e s c r i b e the s e n s a t i o n s you've just experienced. Circle only those words that b e s t d e s c r i b e them. Leave out any category t h a t is n o t s u i t a b l e . U s e o n l y a s i n g l e w o r d in each appropriate category--the one that applies best. Recall the most intense sensations you felt d u r i n g the session w h ile c h o o s i n g words. 1
2
Flickering Quivering Pulsing Throbbing Beating Pounding
Jumping Flashing Shooting
5
6
Pinching Pressing Gnawing Cramping Crushing 9 Dull Sore Hurting Aching Heavy 13
Tugging Pulling Wrenching
10 Tender T aut Rasping Splitting
14
Fearful Frightful Terrifying
Punishing Grueling Cruel Vicious Killing
17
18
Spreading Radiating Penetrating Piercing
Tight Numb Drawing Squeezing Tearing
3 Pricking Boring Drilling Stabbing Lancinating
7 Hot Burning Scalding Searing
11
A Sharp Cutting Lacerating
8 Tingling Itchy Smarting Stinging
12
Tiring Exhausting
Sickening Suffocating
15
16
Wretched Blinding
19 Cool Cold Freezing
Annoying Troublesome Miserable Intense Unbearable 20 Nagging Nauseating Agonizing Dreadful Torturing
The modified McGill Pain Questionnaire (MPQ). Klepac-others : REPORTS OF PAIN AFTER DENTAL TREATMENT ■ 693
A RTIC LES
summed for the affective dimension;, item 16 was equated to the evaluative dimension; and items 17 to 20 were miscellaneous. All items wpre then summed for a total score. Rationale for these scoring procedures, item groupings, and the scaling proce dures are described in Melzack 11 and Melzack and Torgerson.14 Two items on the rating scale were adapted for use in this study as well. Both items requested a rating of the intensity of pain on a scale in which 0 equaled none; 1 equaled mild; 2 equaled discomforting; 3 equaled distressing; 4 equaled horrible; and 5 equaled excruciating. One item, dubbed present pain intensity (PPI), asked for a rating of the worst pain experienced during the preceding session; the other requested a rating of the worst pain ever experienced during dental treatment.
Procedures Patients were asked by office staff to read and complete a questionnaire. The packet they received contained a complete description of the research, instructions for completion of the materials, and an envelope. Instruc tions emphasized that participation was voluntary and that patients could return the packet unused to the receptionist. If they were willing to participate, patients completed the MPQ to describe the most intense stimulation they had experienced during that session, then sealed the questionnaire in an envelope that would later be delivered to the re search team. Thus, patients’ reports were anonymous both to the office staff and the research team. Through a coding system, the research staff grouped together all patients of a par ticular dentist; however, the identity of each dentist remained unknown. Shocks to both the arm and tooth were presented in two ascending series of stimuli; each began below sensation threshold and proceeded in small increments to the point at which the stimulus was first per c e iv e d (s e n s a tio n th r e s h o ld ), through the level at which subjects first labeled the sensation as “pain ful” (threshold of pain) to the point at which the stimulus was described as “definitely painful and the most in tense stimulus (the subject was) will ing to tolerate in the series” (toler 694 ■ JADA, Vol. 100, May 1980
ance to pain). Immediately after the second series, subjects were asked to complete the MPQ to describe the most intense stimulation they had experienced during that session. Mean current levels at sensation threshold, pain threshold, and toler ance were 16.2, 19.0, and 55.7 respectively, for shock to the tooth; and 1.38, 2.78, and 7.71 mA, respec tively, for shock to the arm.
/xA,
Results Means for the MPQ scales and the ratings of “present pain intensity” and “worst dental treatment ever ex perienced” appear in the Table. Each score was treated v ia one-w ay analysis of variance; this resulted in significant differences among the groups on the MPQ sensory scale, (2, 84) = 5.37, P < .007; miscellane ous scale, F (2 , 84) = 3.72, P < .028; total score, F (2,84) = 4.56,P < .014; and PPI, F (2, 84) = 8.07, P < .001. Newman-Keuls tests disclosed that each of these effects resulted from the dental patients’ scoring lower than one or both of the laboratory groups of subjects, 4}though the latter two groups did not differ. The fact that groups did not differ in ratings of w orst d en tal treatm en t argues against differential bias toward re porting pain as an explanation of the other significant differences between the groups. Of the 29 dental patients, 22 rated PPI greater than 0. In other terms, 76.5% of these patients reported at least mild pain during dental treat ment.
F
Discussion On two global in d exes of pain intensity—the MPQ total score and the direct rating of in ten sity of jjain — dental treatment was per ceived as less painful than one or both of our presumably mild labora tory stressors. The p arallel dif ferences between the groups on the MPQ sensory scale suggest that these overall intensity differences are par tially caused by differences in the sensory qualities of dental treatment relative to pain induced in the labora tory. Although Melzack 13,14 is un clear on the meaning of the miscel laneous scale, items 17 to 19 (Illustra tion) seem similar to the kind of sen
sory qualities reflected in the sensory items (1 to 1 0 ). Considered together, the data suggest that dental treatment is experienced as less intensely pain ful than levels of tolerance to pain induced in the laboratory, and that this difference is the result of dif ferences in the sensory rather than affective or cognitive and evaluative dimensions of the experience of pain. The foregoing interpretation as sumes that the items grouped to gether to form the MPQ subscales are reasonably valid indexes of the di mensions of pain with which they are labeled. Although Melzack based these groupings on reasonable strat egies for constructing a scale and of fered data to justify the distinctions, a factor analysis of the MPQ resulted in a structure of factors that is slightly different from the groupings of items used here .15 Attribution of group dif ferences in pain intensity to sensory rather than affective or cognitive and evaluative factors should be held ten tatively; therefore, although no such qualification is warranted in the in tensity indexes themselves, patients report dental treatment to be less paiiiful than those reporting the ex perience of tooth pulp stimulation or shock to the forearm. Comparisons of PPI ratings of den tal patients and total scores on the MPQ with those reported in other studies support the view of the rela tive painlessness of routine dental treatment among regular patients. Melzack reported mean ratings for patients for whom seven different pain syndromes were diagnosed (for example from menstruation, cancer, or arthritis). Mean PPIs from these patients ranged from 1.9 to 3.0 (com pared wi|h our dental patients’ 1 . 1 ) and total'scores on the MPQ ranged frop 17.5 to 26.3 (compared with dental p a tie n ts’ 14 .1 ). A nother study16 examined MPQ scores after dental extractions. PPIs from this study ranged from a high of 2.15 the evening after surgery to 1.52 two days later (total scores of the MPQ were not reported). These compari sons also suggest that the pain in volved in routine dental treatment is, in fact, mild, just as Jackson 10 and dental practitioners have suspected. Another factor that may be relevant rests in the findings of Kleinknecht and Bernstein ,5 who found that max imally and m inimally fearful pa
A RTICLES
tients tested during treatment dif fered in response to several measures including pain ratings, and show anxiety, but not in overt body move ments, facial expression, or other overt, readily observable reactions. These data suggest that whatever mild levels of pain are experienced in the operatory would not usually be evident to dentists or their team; these enhance further the impression of painlessness among patients dur ing regular visits. The paradox between these data and those supporting the importance of pain in dental apprehension is, nonetheless, more apparent than real. Those earlier studies1’9 system atically selected fearful or avoidant patients, who have infrequently vis ited the dentist,17 often to the point of nearly total avoidance.6 Dental prac titioners see a different set of patients than those seen by researchers. Fearful patients selected for study by researchers, by definition, re spond to dentally relevant cues and stimuli with fear and arousal and show greater reactivity to pain than their fearless counterparts. It should be underscored that modern pain theory regards that phenomenon as every bit as real as the lower level of pain reported by fearless patients. As Turk 18 says: “Recent reviews of the pain literature (e.g. Clark and Hunt, 1971; Liebeskind and Paul, 1977; Turk, 1975) have pro vided com pelling arguments that pain is not simply a function of the amount of tissue damage nor can it be defined ade quately by specifying parameters of phys ica l stim u li as suggested by sensoryp h y s io lo g ic a l th e o rie s. R ath er, p ain should be considered a subjective experi ence defined by an individual, w ith the amount and quality of the pain deter mined by various factors: previous expe riences, how they are recalled, ability to understand the cau se and the co n se quences of the pain, all in addition to the sensory input. Taken together, the clin i c a l observations and laboratory data suggest th at an adequate con cep tu al ization of pain must be multidim ensional in nature, incorporating cognitive and af fective phenomena as well as the physical stimuli and sensory physiology.”
Turks’s view reflects a virtual con sensu s am ong resea rch ers and theorists of pain that affective factors (like fear), and cognitive factors (like “catastrophizing” self-statements) greatly increase the perception and experience of pain .19 The finding that patients who routinely visit a dentist report little pain simply un derscores the importance of under standing and treating the fearful, more sensitive patient.
Summary A growing body of literature suggests that pain is a crucial factor in the development and maintenance of apprehension toward dental treat ment. These findings are often at variance with dental practitioners’ im pressions that routine dental treatment is virtually painless. Data from this study suggest that routine dental treatment is seldom perceived by regular patients as painless but is seen as low in intensity of pain com pared with mild laboratory stressors. These data are interpreted as sup porting the hypothesis that dental treatm ent is relatively painless. However, this conclusion conflicts with data supporting the importance of pain in dental fear, and possible reasons for the discrepancy are pre sented.
The informed consent of all human subjects who participated in the experimental investiga tion reported or described in this manuscript was obtained after the nature of the procedures and possible discomforts and risks had been fully explained. This research was supported by NIH grant no. DE-04976 awarded by the National Institute of Dental Research to the first author. A greatly abbreviated report of this study was included in a paper presented at the Second National Con ference in Behavioral Dentistry, Morgantown, W Va, October 1979, and will be published in the conference proceedings. □r. Klepac is associate professor and chair man, department of psychology, College of Sci ence and Mathematics, North Dakota State Uni versity, Fargo, 58105. Dr. Dowling is research associate, department of psychology, North Dakota State University. Mr. Hauge is clinical
research associate, dental behavior clinic, North Dakota State University. Mr. McDonald, formerly a clinical research assistant, North Dakota State University, is currently a doctoral student, department of psychology, Purdue University. Address requests for reprints to Dr. Klepac. 1. Melamed, B.G. Behavioral approaches to fear in dental settings. In Hersen, M.; Eisler, R.; and Miller, P. (eds.). Progress in behavior mod ification, vol 7. New York, Academic Press, 1979, pp 171-203. 2. Kleinknecht, R.A.; Klepac, R.D.; and Alex ander, L.D. Origins and characteristics of fear of dentistry. JADA 86(4):842-848, 1973. 3. Forgione, A., and Clark, R.E. Comments on an empirical study of the causes of dental fear. J Dent Res 53:496, 1974. 4. Kleinknecht, R.A. Fear assessment in the dental office. In Ingersoll, B., and others (eds.). Behavioral dentistry; proceedings of the second national conference. Morgantown, W Va, West Virginia University Press, to be published. 5. Kleinknecht, R.A., and Bernstein, D.A. The assessment of dental fear. Behav Ther 86:842-848, 1978. 6. Lautch, H. Dental phobia. Br J Psychiatry 119:151-158, 1971. 7. Klepac, R.K., and others. Reactions to pain among subjects high and low in dental fear. North Dakota State University, to be published. 8. Meichenbaum, D. Cognitive behavior modification: an integrative approach. New York, Plenum Press, 1977. 9. Klepac, R.K. Successful treatment of avoidance of dental work by desensitization or increasing pain tolerance. J Behav Ther Exp Psychiatr 6:307-310,1975. 10. Ziffer, R.L. How to really relax at the den tist’s. Parade: Nov 11, 1979, p 15. 11. Martin, R.W., and Chapman, C.R. Dental dolorimetry for human pain research: methods and apparatus. Pain 6:349-364, 1979. 12. Tursky, B. Presidential address, 1973. Physical, physiological, and psychological fac tors that affect pain reaction to electric shock. Psychophysiology 11:95-112, 1974. 13. Melzack, R. The McGill Pain Question naire: major properties and scoring methods. Pain 1:277-299, 1975. 14. Melzack, R., and Torgerson, W.S. On the language of pain. Anesthesiology 34:50-59, 1971. 15. Crockett, D.J.; Prkachin, K.M.; and Craig, K.D. Factors of the language of pain in patient and volunteer groups. Pain 4:175-182,1977. 16. Van Buren, J., and Kleinknecht, R.A. An evaluation of the McGill Pain Questionnaire for use in dental pain assessment. Pain 6:23-34, 1979. 17. Friedson, E., and Feldman, J.J. The public looks at dental care. JADA 57:325-335,1958. 18. Turk, D.C. Cognitive behavioral tech niques in the management of pain. In Foreyt, J., and Rathjen, D. (eds.). Cognitive behavior ther apy. New York, Plenum Press, 1978, p 202. 19. Stembach, R. (ed.). The psychology of pain. New York, Raven Press, 1978.
Klepac-others : REPORTS OF PAIN AFTER DENTAL TREATMENT ■ 695
r r r m y jjffi j|
A R T IC L E S
Reports of pain after dental treatment, electrical tooth pulp stimulation, and cutaneous shock Robert K. K lepac, PhD Joh n Dow ling, PhD G regory Hauge M arvin M cDonald
To determine if dental treatment is relatively painless and if certain factors contribute to apprehension of dental treatment, a questionnaire was given to dental patients and subjects of mild laboratory stressors. Responses of these groups were then compared.
r
Jomparisons of particularly fear ful and nonfearful dental patients have repeatedly implicated pain as a factor important to dental apprehen sion.1 Studies supporting this infer ence include: reports from largesample surveys on subjects’ percep tion of the origins of their fear2; inter views with maximally and m ini mally fearful subjects3; ratings of pa tients actually undergoing dental tre a tm e n t4,5; and re a c tio n s to p s y c h o p h y s ic a l te s ts of p ain threshold6-7 and tolerance.7 Treat ments aimed at increasing tolerance to pain have been proposed8 and were effective in case studies9 in re ducing avoidance of dentistry. Con sidered togeth er, these studies 692 ■ JADA, Vol. 100, May 1980
suggest that pain, although not the sole or most frequent2,4 factor in den tal apprehension, is clearly among the important factors in understand ing fear and avoidance of dental treatment. In a magazine article on dental ap prehension, Eric Jackson was quoted as saying, “there’s not very much pain in dentistry any more.”10 This point has been made by several den tists in audiences we have addressed and reflects the genuine puzzlement over the seeming paradox—how can a situation that is virtually painfree lead to so many studies that impli cate pain as a major factor in dental apprehension? In fact, hard data do not exist to
support the assumption of painless ness in dental treatment: the assump tion apparently is based on dentists’ observations of patients during treatment, and commentators’ sub jective evaluation of their experi ences with dental treatment. The purpose of this paper is to report on a study that assesses the characteris tics and intensity of pain experi enced during dental treatment by comparing patients’ reports on an es tablished pain questionnaire to re ports of subjects undergoing con trolled laboratory pain. M eth o d
Subjects A total of 58 student volunteers were randomly assigned to receive shock to either an arm or a tooth. The sam ple of dental patients was drawn from a pool created when ten dentists were asked to have as many patients as were willing (up to 33 per dentist) co m p le te a q u e s tio n n a ir e im m ediately after their dental ap pointments. A total of 139 usable questionnaires were returned; most
A R T IC L E S
Table ■ M ean scores on questionnaires on pain. Ratings of paint
Scores on Melzack-McGill Questionnaire
No. Pain group
(M/F)
Age
Sensory*
Affective
Evaluative
Miscellaneous*
Total
Present pain intensity*
Worst dental treatment
Dental treatment Tooth shuck Arm shock
17/12 14/15 11/18
21.7 20.4 20.6
9.2 (a) 14.9 (b) 12.7 (b)
1.0 1.6 0.7
1.2 1.6 1.3
2.8 (a) 4.6 (b) 4.6 (b)
14.1 (a) 22.5 (b) 19.3
1.1 (a) 1.9 (b) 1.8 (b)
2.9 3.4 2.8
‘ Analysis of variance of this variable showed difference in the group of at leastP < .05. Numbers in each colum n followed by letters in parentheses differ a tP < .05 (Newman-Keuls tests). tR atings: 0 = none, 5 = excruciating.
of these (113) came from four den tists. Because reports of pain have been found to vary systematically with age,4 a sample of 29 patients was selected randomly from those within the age range of our sample of college students. Mean ages and male to female ratios appear in the Table.
Instruments and apparatus Tooth pulp stimulation was deliv ered by a DC stimulator (Nuclear, Chicago) modified via a series of potentiometers to permit the ex tremely low current levels and fine increments required. Stimuli were 500 msec trains of 10-msec unipolar pulses presented at a rate of 50 pulses per second. The anode was a conduc tive rubber electrode, 3-mm square, embedded in a plastic probe held by the subject against the incisal edge of a healthy maxillary incisor. A groove filled with electrode paste facilitated electrical contact that was monitored continuously on an oscilloscope. The cathode (Beckman EMG electrode) was attached to the left cheek. These arrangements were patterned after those suggested by M artin and Chapman.11 Cutaneous stimulation was deliv ered by a custom-built, constantcurrent AC stimulator capable of de livering 0 to 21 mA in increments of 0.5 mA. Stimuli of 0.5-sec duration were presented through concentric saline electrodes to the volar surface of the nonpreferred forearm just above the wrist. The contact between electrode and subject was prepared to yield 5,000 (plus or minus 500) ohms inpedance. The apparatus and preparation is that recommended by Tursky.12 The Melzack-McGill Pain Ques tionnaire (MPQ) was used to gather reports on pain. The main portion of the MPQ appears in the Illustration. Subjects were asked to circle words that accurately described their expe riences. The subject did not need to choose a word from each group,
however, only one word from any numbered group should have been circled. As used in this study, if no word was chosen from a group, that group scored 0. If a word was chosen, the rank of that word was entered for that item’s score. For example, if a subject did not select a word from
group 1, the score for that item equaled 0; if “flickering” were cir cled, the score equaled 1; the selec tion of “quivering” scored 2; and selection of “ pulsing” scored 3. Scores for items one to ten were then summed to form a score for the sen sory dimension; items 11 to 15 were
Some of the w o r d s b e l o w d e s c r i b e the s e n s a t i o n s you've just experienced. Circle only those words that b e s t d e s c r i b e them. Leave out any category t h a t is n o t s u i t a b l e . U s e o n l y a s i n g l e w o r d in each appropriate category--the one that applies best. Recall the most intense sensations you felt d u r i n g the session w h ile c h o o s i n g words. 1
2
Flickering Quivering Pulsing Throbbing Beating Pounding
Jumping Flashing Shooting
5
6
Pinching Pressing Gnawing Cramping Crushing 9 Dull Sore Hurting Aching Heavy 13
Tugging Pulling Wrenching
10 Tender T aut Rasping Splitting
14
Fearful Frightful Terrifying
Punishing Grueling Cruel Vicious Killing
17
18
Spreading Radiating Penetrating Piercing
Tight Numb Drawing Squeezing Tearing
3 Pricking Boring Drilling Stabbing Lancinating
7 Hot Burning Scalding Searing
11
A Sharp Cutting Lacerating
8 Tingling Itchy Smarting Stinging
12
Tiring Exhausting
Sickening Suffocating
15
16
Wretched Blinding
19 Cool Cold Freezing
Annoying Troublesome Miserable Intense Unbearable 20 Nagging Nauseating Agonizing Dreadful Torturing
The modified McGill Pain Questionnaire (MPQ). Klepac-others : REPORTS OF PAIN AFTER DENTAL TREATMENT ■ 693
A RTIC LES
summed for the affective dimension;, item 16 was equated to the evaluative dimension; and items 17 to 20 were miscellaneous. All items wpre then summed for a total score. Rationale for these scoring procedures, item groupings, and the scaling proce dures are described in Melzack 11 and Melzack and Torgerson.14 Two items on the rating scale were adapted for use in this study as well. Both items requested a rating of the intensity of pain on a scale in which 0 equaled none; 1 equaled mild; 2 equaled discomforting; 3 equaled distressing; 4 equaled horrible; and 5 equaled excruciating. One item, dubbed present pain intensity (PPI), asked for a rating of the worst pain experienced during the preceding session; the other requested a rating of the worst pain ever experienced during dental treatment.
Procedures Patients were asked by office staff to read and complete a questionnaire. The packet they received contained a complete description of the research, instructions for completion of the materials, and an envelope. Instruc tions emphasized that participation was voluntary and that patients could return the packet unused to the receptionist. If they were willing to participate, patients completed the MPQ to describe the most intense stimulation they had experienced during that session, then sealed the questionnaire in an envelope that would later be delivered to the re search team. Thus, patients’ reports were anonymous both to the office staff and the research team. Through a coding system, the research staff grouped together all patients of a par ticular dentist; however, the identity of each dentist remained unknown. Shocks to both the arm and tooth were presented in two ascending series of stimuli; each began below sensation threshold and proceeded in small increments to the point at which the stimulus was first per c e iv e d (s e n s a tio n th r e s h o ld ), through the level at which subjects first labeled the sensation as “pain ful” (threshold of pain) to the point at which the stimulus was described as “definitely painful and the most in tense stimulus (the subject was) will ing to tolerate in the series” (toler 694 ■ JADA, Vol. 100, May 1980
ance to pain). Immediately after the second series, subjects were asked to complete the MPQ to describe the most intense stimulation they had experienced during that session. Mean current levels at sensation threshold, pain threshold, and toler ance were 16.2, 19.0, and 55.7 respectively, for shock to the tooth; and 1.38, 2.78, and 7.71 mA, respec tively, for shock to the arm.
/xA,
Results Means for the MPQ scales and the ratings of “present pain intensity” and “worst dental treatment ever ex perienced” appear in the Table. Each score was treated v ia one-w ay analysis of variance; this resulted in significant differences among the groups on the MPQ sensory scale, (2, 84) = 5.37, P < .007; miscellane ous scale, F (2 , 84) = 3.72, P < .028; total score, F (2,84) = 4.56,P < .014; and PPI, F (2, 84) = 8.07, P < .001. Newman-Keuls tests disclosed that each of these effects resulted from the dental patients’ scoring lower than one or both of the laboratory groups of subjects, 4}though the latter two groups did not differ. The fact that groups did not differ in ratings of w orst d en tal treatm en t argues against differential bias toward re porting pain as an explanation of the other significant differences between the groups. Of the 29 dental patients, 22 rated PPI greater than 0. In other terms, 76.5% of these patients reported at least mild pain during dental treat ment.
F
Discussion On two global in d exes of pain intensity—the MPQ total score and the direct rating of in ten sity of jjain — dental treatment was per ceived as less painful than one or both of our presumably mild labora tory stressors. The p arallel dif ferences between the groups on the MPQ sensory scale suggest that these overall intensity differences are par tially caused by differences in the sensory qualities of dental treatment relative to pain induced in the labora tory. Although Melzack 13,14 is un clear on the meaning of the miscel laneous scale, items 17 to 19 (Illustra tion) seem similar to the kind of sen
sory qualities reflected in the sensory items (1 to 1 0 ). Considered together, the data suggest that dental treatment is experienced as less intensely pain ful than levels of tolerance to pain induced in the laboratory, and that this difference is the result of dif ferences in the sensory rather than affective or cognitive and evaluative dimensions of the experience of pain. The foregoing interpretation as sumes that the items grouped to gether to form the MPQ subscales are reasonably valid indexes of the di mensions of pain with which they are labeled. Although Melzack based these groupings on reasonable strat egies for constructing a scale and of fered data to justify the distinctions, a factor analysis of the MPQ resulted in a structure of factors that is slightly different from the groupings of items used here .15 Attribution of group dif ferences in pain intensity to sensory rather than affective or cognitive and evaluative factors should be held ten tatively; therefore, although no such qualification is warranted in the in tensity indexes themselves, patients report dental treatment to be less paiiiful than those reporting the ex perience of tooth pulp stimulation or shock to the forearm. Comparisons of PPI ratings of den tal patients and total scores on the MPQ with those reported in other studies support the view of the rela tive painlessness of routine dental treatment among regular patients. Melzack reported mean ratings for patients for whom seven different pain syndromes were diagnosed (for example from menstruation, cancer, or arthritis). Mean PPIs from these patients ranged from 1.9 to 3.0 (com pared wi|h our dental patients’ 1 . 1 ) and total'scores on the MPQ ranged frop 17.5 to 26.3 (compared with dental p a tie n ts’ 14 .1 ). A nother study16 examined MPQ scores after dental extractions. PPIs from this study ranged from a high of 2.15 the evening after surgery to 1.52 two days later (total scores of the MPQ were not reported). These compari sons also suggest that the pain in volved in routine dental treatment is, in fact, mild, just as Jackson 10 and dental practitioners have suspected. Another factor that may be relevant rests in the findings of Kleinknecht and Bernstein ,5 who found that max imally and m inimally fearful pa
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tients tested during treatment dif fered in response to several measures including pain ratings, and show anxiety, but not in overt body move ments, facial expression, or other overt, readily observable reactions. These data suggest that whatever mild levels of pain are experienced in the operatory would not usually be evident to dentists or their team; these enhance further the impression of painlessness among patients dur ing regular visits. The paradox between these data and those supporting the importance of pain in dental apprehension is, nonetheless, more apparent than real. Those earlier studies1’9 system atically selected fearful or avoidant patients, who have infrequently vis ited the dentist,17 often to the point of nearly total avoidance.6 Dental prac titioners see a different set of patients than those seen by researchers. Fearful patients selected for study by researchers, by definition, re spond to dentally relevant cues and stimuli with fear and arousal and show greater reactivity to pain than their fearless counterparts. It should be underscored that modern pain theory regards that phenomenon as every bit as real as the lower level of pain reported by fearless patients. As Turk 18 says: “Recent reviews of the pain literature (e.g. Clark and Hunt, 1971; Liebeskind and Paul, 1977; Turk, 1975) have pro vided com pelling arguments that pain is not simply a function of the amount of tissue damage nor can it be defined ade quately by specifying parameters of phys ica l stim u li as suggested by sensoryp h y s io lo g ic a l th e o rie s. R ath er, p ain should be considered a subjective experi ence defined by an individual, w ith the amount and quality of the pain deter mined by various factors: previous expe riences, how they are recalled, ability to understand the cau se and the co n se quences of the pain, all in addition to the sensory input. Taken together, the clin i c a l observations and laboratory data suggest th at an adequate con cep tu al ization of pain must be multidim ensional in nature, incorporating cognitive and af fective phenomena as well as the physical stimuli and sensory physiology.”
Turks’s view reflects a virtual con sensu s am ong resea rch ers and theorists of pain that affective factors (like fear), and cognitive factors (like “catastrophizing” self-statements) greatly increase the perception and experience of pain .19 The finding that patients who routinely visit a dentist report little pain simply un derscores the importance of under standing and treating the fearful, more sensitive patient.
Summary A growing body of literature suggests that pain is a crucial factor in the development and maintenance of apprehension toward dental treat ment. These findings are often at variance with dental practitioners’ im pressions that routine dental treatment is virtually painless. Data from this study suggest that routine dental treatment is seldom perceived by regular patients as painless but is seen as low in intensity of pain com pared with mild laboratory stressors. These data are interpreted as sup porting the hypothesis that dental treatm ent is relatively painless. However, this conclusion conflicts with data supporting the importance of pain in dental fear, and possible reasons for the discrepancy are pre sented.
The informed consent of all human subjects who participated in the experimental investiga tion reported or described in this manuscript was obtained after the nature of the procedures and possible discomforts and risks had been fully explained. This research was supported by NIH grant no. DE-04976 awarded by the National Institute of Dental Research to the first author. A greatly abbreviated report of this study was included in a paper presented at the Second National Con ference in Behavioral Dentistry, Morgantown, W Va, October 1979, and will be published in the conference proceedings. □r. Klepac is associate professor and chair man, department of psychology, College of Sci ence and Mathematics, North Dakota State Uni versity, Fargo, 58105. Dr. Dowling is research associate, department of psychology, North Dakota State University. Mr. Hauge is clinical
research associate, dental behavior clinic, North Dakota State University. Mr. McDonald, formerly a clinical research assistant, North Dakota State University, is currently a doctoral student, department of psychology, Purdue University. Address requests for reprints to Dr. Klepac. 1. Melamed, B.G. Behavioral approaches to fear in dental settings. In Hersen, M.; Eisler, R.; and Miller, P. (eds.). Progress in behavior mod ification, vol 7. New York, Academic Press, 1979, pp 171-203. 2. Kleinknecht, R.A.; Klepac, R.D.; and Alex ander, L.D. Origins and characteristics of fear of dentistry. JADA 86(4):842-848, 1973. 3. Forgione, A., and Clark, R.E. Comments on an empirical study of the causes of dental fear. J Dent Res 53:496, 1974. 4. Kleinknecht, R.A. Fear assessment in the dental office. In Ingersoll, B., and others (eds.). Behavioral dentistry; proceedings of the second national conference. Morgantown, W Va, West Virginia University Press, to be published. 5. Kleinknecht, R.A., and Bernstein, D.A. The assessment of dental fear. Behav Ther 86:842-848, 1978. 6. Lautch, H. Dental phobia. Br J Psychiatry 119:151-158, 1971. 7. Klepac, R.K., and others. Reactions to pain among subjects high and low in dental fear. North Dakota State University, to be published. 8. Meichenbaum, D. Cognitive behavior modification: an integrative approach. New York, Plenum Press, 1977. 9. Klepac, R.K. Successful treatment of avoidance of dental work by desensitization or increasing pain tolerance. J Behav Ther Exp Psychiatr 6:307-310,1975. 10. Ziffer, R.L. How to really relax at the den tist’s. Parade: Nov 11, 1979, p 15. 11. Martin, R.W., and Chapman, C.R. Dental dolorimetry for human pain research: methods and apparatus. Pain 6:349-364, 1979. 12. Tursky, B. Presidential address, 1973. Physical, physiological, and psychological fac tors that affect pain reaction to electric shock. Psychophysiology 11:95-112, 1974. 13. Melzack, R. The McGill Pain Question naire: major properties and scoring methods. Pain 1:277-299, 1975. 14. Melzack, R., and Torgerson, W.S. On the language of pain. Anesthesiology 34:50-59, 1971. 15. Crockett, D.J.; Prkachin, K.M.; and Craig, K.D. Factors of the language of pain in patient and volunteer groups. Pain 4:175-182,1977. 16. Van Buren, J., and Kleinknecht, R.A. An evaluation of the McGill Pain Questionnaire for use in dental pain assessment. Pain 6:23-34, 1979. 17. Friedson, E., and Feldman, J.J. The public looks at dental care. JADA 57:325-335,1958. 18. Turk, D.C. Cognitive behavioral tech niques in the management of pain. In Foreyt, J., and Rathjen, D. (eds.). Cognitive behavior ther apy. New York, Plenum Press, 1978, p 202. 19. Stembach, R. (ed.). The psychology of pain. New York, Raven Press, 1978.
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