The pain and discomfort experienced during orthodontic treatment: A randomized controlled clinical trial of two initial aligning arch wires Malcolm Jones, BDS, MSc, PhD, FDS, D.Orth., RCS," and Clement Chan, BDS, MScD, MOrth, RCS, MDO, RCPSb Cardiff, Wales A randomized controlled clinical trial was performed to compare the nature, prevalence, intensity, and duration of pain related to the use of a relatively recently developed superelastic arch wire and a more traditional multistranded steel arch wire. Other factors likely to influence the pain experience were also investigated. Forty-three subjects participated in the study, the pain response being assessed by each of the visual analogue scales, the questionnaires, and an analgesic consumption record. In 18 of the 43 subjects a standardized preliminary dental extraction procedure was used as a control. Subsequent to the random allocation of an initial arch wire in 43 patients, 22 of them underwent a second arch wire in the opposing arch, the wire again being determined by random allocation. It was found that the prevalence, intensity, and duration of pain after the insertion of the two types of wire was similar but much greater than in the postextraction control phase. The pain score peaked on the morning after the placement of the arch wire, lasting typically for 5 to 6 days. The pain and discomfort experienced after the insertion of the second arch wire was similar to that of the first, no conditioning response being evident. Overall a diurnal variation was found with a tendency to an increase in pain in the evenings and nights, although this did not greatly affect sleep. The pain response was found to be highly and consistently subjective, not related to the dental arch, crowding, sex, or social class; however, a statistically significant association was found between the age and the pain experienced. (AMJ ORTHOD DENTOFACORTHOP 1992;102:373"81.)
P a i n and discomfort after the insertion of an initial arch wire are common experiences among orthodontic patients. It has been reported that fear of pain is a key factor in discouraging patients from seeking orthodontic treatment. ~ Further, another author2 has found that a small but significant proportion of patients (8%) discontinue treatment because of the pain experienced in the early stages of appliance therapy. It would appear that the problem is extensive, however, only a limited number of studies have specifically investigated the subject. Previously, one of the authors 3 has used a combination of"numerical pain scaling" and "recorded analgesic consumption" in an initial evalu-. ation of the frequency of pain response after insertion of the first arch wire in an edgewise appliance. A significant proportion of patients were found to score at least one session in a day as "experiencing severe or moderate discomfort." It was found that the majority of these positive responses occurred in the first 8 days after placement of the fixed appliance, whereas the most
From the University of Wales College of Medicine. *Senior Lecturer and Consultant in Orthodontics. **Registrar in Orthodontics. 811131349
severe scores were within the first 3 days. No significant difference in pain response was found between the sexes although age appeared to be an important factor: patients over 16 years of age scoring a consistently higher pain/discomfort response, which was also often more prolonged. More recently, another study4 has found that patients receiving orthodontic treatment (involving either placement of seperators or an initial arch wire) recorded a significantly higher degree of dental discomfort than those in a control group. In addition, those patients rating high scores after 4 hours showed a trend towards a similar response both after 24 and 168 hours. Burstone5 has classified the pain response into three different degrees: 1. First degree pain--produced by heavy pressure placed on the tooth with an instrument. This is usually elicited most easily by applying the force in the same direction as the fixed appliance. The patient is not aware of first degree pain unless the orthodontist manipulates the teeth being actively moved with the appliance. 2. Second degree pain--characterized by pain or discomfort during tooth clenching or heavy "biting." The patient maintains the ability to masticate a normal diet without difficulty.
373
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Jones and Cban
3. Third degree pain--present when the patient is suffering from spontaneous pain or is unable to masticate food of a normal consistency. However, the boundaries o f these various degrees o f pain are imprecise. Burstone 5 also identified an immediate and delayed pain response: the former being related to the initial compression of the periodontal ligament; and the latter, which commenced a few hours later, produced by a large range of force values and representing, as he termed it, hyperalgesia of the ligament. It is a traditional belief that there is a definite relationship between the force applied to a tooth and the pain experienced2 This theory being in line with the early classical histologic studies 6.7 which promoted the idea of light differential forces as being more efficient, biologic, and less painful. However, other authors 8~~ have failed to confirm a strong association between the force being applied and the subsequent pain. Over the last few years there have been rapid developments in the field of preformed alloy arch wires, these wires replacing, in many clinics, the more traditional light or braided steel arch wires in the role of initial tooth alignment. Beta titanium," it has been claimed, is likely to cause less discomfort by virtue of its low stiffness and high springback; delivering force values of less than half of that for stainless steel of the same dimension. More recently, "superelastic" archwires have become popular for tooth alignment. ~2 Again, similarly, since these wires deliver a constant force over an extended portion of the deactivation range, it has been claimed that "tooth movement occurred more effectively and patients did not experience discomfort". However, there has been only limited research into the clinical effectiveness of these types of arch wire. '3~50'Brien ~3"~ for example, in a randomized trial could not find any significant difference in initial alignment between two alloy arch wires. The present study is intended to test whether any significant difference in the pain/discomfort experience could be found between two types of initial aligning arch wires currently in use in an orthodontic clinic. These two archwires are a superelastic alloy, 0.014inch heavy Japanese Niti (GAC International Inc., Central Islip, N.Y.) and a multistrand steel, 0.015-inch Twistflex (Unitek Corp., Monrovia, Calif.) Further, it is also intended in this study to examine the general phenomenon of initial pain/discomfort in fixed appliance treatment.
METHOD A protocol was drawn up and approved by the Dental Ethics Panel of the University of Wales College of Medicine
Am. J. Orthod. Dentofac. Orthop. October 1992
and, as a part of this process the necessary sample size was selected on the basis of calculations from the results for a previous study by one of the authors2
Criteria for patient selection Forty-three consecutive patients attending the Orthodontic Clinic at the UWCM were admitted to the study on the basis that they were willing to participate and satisfied the following criteria: 1. The patient required extraction of at least one premolar tooth and the placement of a full arch edgewise fixed appliance, 0.018 • 0.030-inch standard (triple control) preadjusted bioprogressive brackets (Rocky Mountain Orthodontics, Denver, Colo.) 2. There was no relevant medical history to affect the dental extraction under local anesthesia. 3. No molar band, palatal arch, Nance button, or quadhelix present on entry to trial were either active or causing discomfort. 4. No extraoral traction was to be used over the period of the study. 5. Patients were to be under the age of 17 years. This was to avoid further complications in the study design since otherwise sampling adjustments would have been necessary to address an age related finding in a previous study2 6. Informed and witnessed consent was obtained from patients, parents/guardian and the general dental practitioner who originally referred each patient.
PROTOCOL The study was divided into three stages: Stage I: Investigation into the pain and discomfort after extraction (used as a control). Stage II: Investigation into the pain and discomfort after the insertion of the first arch wire in either upper or lower arches. Stage III: Investigation into the pain and discomfort after the insertion of the second arch wire in the opposing arch to stage II. All 43 patients participated in stage II of the study; 18 of these participated in stage I, and 22 participated in stage III. Tables IA and IB demonstrate the combinations of arch wires used in the study and their order of allocation. Further detail of the protocol is available elsewhere. '6 However, the same verbal instructions and questionnaires were given to each patient: 1. Daily record of painldiscomfort. This measured by means of 100 mm visual analogue scales (VAS) the pain at four periods during each 24 hours; at 0900, 1300, 1700, and 2100 hours over 15 days. 2. Your painl discomfort after24 hours. A questionnaire to detail the location and frequency of the pain and "back-up" the VAS section. 3. Tablet consumption. Since it was thought that patients would take analgesics when in severe pain in any event, it was considered prudent to standardize the drug. Paracetamol tablets (Arthur H. Cox & Co.,
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Table IA. To demonstrate the various
Table lB. To demonstrate the order in which the different wires were applied to the dental arches
combinations of arch wires used in this study
First arcll wire Niti Flex TOTAL
Second arch wire Niti
l
Flex
l
None
[ Total
5 6
6 5
1! 10
22 21
11
11
21
43
Niti, Niti alloy arch wire. Flex, Multiflex steel arch wire. London, England), were prescribed to every patient together with a record sheet. The patients in the study were instructed to take the tablets for the relief of pain to their own regimen. This provided a complementary measure of pain experience, as well as providing a means of identifying any times of day at which analgesics might have affected the reading.
Crowding assessment All initial study casts of the patients in the study were assessed for the degree of initial croffding by three-dimensional digitization with the Reflex Metrograph (Ross Instruments, Salisbury, Wiltshire, U.K.). This has been described previously'7'z8as has the error of the method? 8
Other variables Age, sex, and social class were recorded for every patient.
Statistical analysis All responses from the questionnaires were stored, coded, and analyzed with the Minitab package (Minitab, Inc., University Park, Pa.). Standard methods of analysis were used including the Mann-Whitney and Wilcoxon tests for quantitative variables and the Chi-square, unpaired, and paired (McNemar) tests for binary ones. Associations between continuous variables were evaluated by the Spearman rank correlations. Analyses took account of the fact that each person contributed a large number of values for the VAS scores, which were not to be treated as if independent; subject means were used in significance tests. The levels of statistical significance employed in all tests were p -< 0.05, statistically significant; p --< 0.01, statistically highly significant; p --< 0.001, statistically very highly significant.
RESULTS O f the 45 patients originally admitted to the study, two failed to return any questionnaires and therefore were excluded. Of the 43 remaining, one patient failed to return a stage II questionnaire and another a stage III questionnaire. Arranging the extractions (stage I) within the clinic for other dentists' patients was not without its difficulties, and therefore this was discontinued when a sufficient number of patients had been
First archwire
Second arch wire UpperlLowerlNone
I Total
Upper Lower
-10
12 --
9 1._22
2I 2._22
TOTAL
10
12
21
43
collected. Twenty-one patients later proceeded to stage III, where it was appropriate to place a wire in the opposing arch. On initial analysis of the data, the groups undergoing examination were found to be well matched for sex, age, social class, and degree of initial crowding, z6 For example, the median age for those receiving a Niti wire was 159.5 months, while for the Twistflex wire it was 158.0 months; the age range for the patients in the study was 113 to 202 months. The term time pohzt in the results refers to a single entry on the visual analogue scale at a certain time and day. Table IIA shows the mean and SD of scores per time point over the first 15 days of the study. This is recorded after extraction, after the first arch wire, and after the second arch wire. The visual analogue assessment of pain was supported by a record of sessional analgesic consumption. Table liB shows summary statistics for the number and pattern of occasions when analgesics were taken. An examination of the overall data in this way demonstrated a very large difference between the initial extraction group and the first and second arch wire groups, whichever the method of pain assessment examined (Tables IIA and B). In Table IV this is subsequently shown to be highly statistically significant. No significant difference was found between the means for the stage II and stage III arch wires. The range of values, however, were great (extraction, maximum 79; first and second arch wire, maximum 100), which encouraged further examination of the data in more detail. As part of the questionnaire the patients in the study were asked by means of a verbal assessment to describe their discomfort after 24 hours. Only 5 of 18 (28%) patients had pain 24 hours after extraction, compared with 34 of 42 (81%) and 17 of 21 (81%) after first and second arch wires (one result for each of the latter being unrecorded). A McNemar test comparing extraction with first arch wire shows a highly significant difference (p = 0.008). To examine the diurnal variation in pain response, Table III illustrates the mean pain recorded at each time
Am. J. Orthod.Denmfac.Orthop. October 1992
Jones and Chan
376
T a b l e IIA. Summary statistics for pain score per
T a b l e liB. Summary statistics for analgesic
time point over first 15 days of study for all patients
consumption per day over first 15 days of study
Extraction Number of pain score entries Missing entries Mean SD
First arch wire
1044
2436
0 1.5 6.3
I Second arch wire
Extraction Number of entries Missing entries Mean SD
1218
58 5.7 14.7
58 5.6 14.8
First arch wire
Second arch wire
270
630
315
0
15
15
0.07 0.34
0.12 0.45
0.11 0.45
T a b l e III. Mean pain score of the first 10 time points after first arch wire in 42 subjects (diurnal variation in
pain response)
Time of day (time point, hours)
]
17.00 21.00 9.00 13.00
Mean
[
Median
15.9 25.9 32.5 31.3 27.0 23.9 20.4 17.5 18.3 18.8
17.00
21.00 9.00 13.00 17.00 21.00
[
SD
4.5 12.0 37.0 27.0
]
Ma.titnum
24. l 28.4 25.8 27.8
94.0 100.0 76.0 84.0
17.5
27.1
85.0
19.0 16.0 7.0 16.5 14.0
25.9 23. I 21.5 18.6 18.9
89.0 87.0 87.0 56.0 60.0
Table IV. Comparison of mean daily pain scores (VAS) for stages I and I1 of the study
Extraction stage ! Number
Mean
Median
SD
7.5 0 0 0 0 0 0
12.16 6.99 4.13 3.14 2.25 1.61 1.62
1
17
I 1.79
2 3 4 5 6 7
17 17 17 17 17 17
3.76 1.75 1.35 0.91 0.68 0.65
All
17
! .65
First arch wire stage II Ma.~imum 37.75 19.75 15.75 10.50 8.00 6.25 5.00
Mean
[ Median l
SD
l
Ma~imum
23.84 20.31 14.93 7.57 1.93 0.59 0.53
19.25 4.0 3.75 1.0 0 0 0
23.42 28.10 20.03 13.23 4.22 2.43 2.06
88.00 87.00 72.50 41.50 15.25 10.00 8.50
5.43
17.98
Comparison over 14 days for e.ttractionlfirst arch wire groups 0.75
2.27
7.57
5.12
2.38
**Wileoxon test, p = 0.003.
point in the day (with the VAS). It was found that the highest score tended to be on the morning after the arch wire was inserted, with evenings or nights tending to score more highly thereafter. However, it is of note that only nine stage I and five stage II respondents of those completing the 24-hour assessment (n = 43) recorded the pain as disturbing their sleep; this amounted to a 22% positive response. Table IV shows the mean recorded pain per time point for each day, comparing the extraction with the
first arch wire group. The second arch wire data are very similar to that of the first arch wire and are excluded for the sake of brevity. A statistically very significant difference was found between the two groups, a much increased and longer recorded pain response being found in both of the arch wire groups. The same 17 patients are followed through in Table IV, In Table V the day-by-day pain scores are shown in a similar way to Table IV, but collected in this instance to compare Niti (Japanese niti alloy arch wire)
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Special article 377
3O
l i t AW
20 F-
i ~
8 z ~.
\\
I IO.
\ '.
2nd A W ~
la
,L.
I
9
2
3
II
5
6
7
$
9
10
TIME (IN DAYS}
Fig. 1. To demonstrate and compare mean pain score (VAS) versus time for each procedure. (Ext = postextraction group; 1st AW = first arch wire group; 2nd AW = second arch wire group).
Table V. Comparison of mean daily pain scores (VAS) for the two arch wires
NiTi arch wire (n = 21) Day
MeanlMedianlSO
l 2 3 4 5 6 7
29.0 19.6 12.6 5.5 4.1 2.9 1.2
23.0 17.5 11.5 1.3 0.5 0 0
All
5.7
3. I
Flex arch wire (n = 21) I
22.4 21.2 I 1.4 7.9 6.1 6.2 2.5
Range
Mean
3.7-88.0 0-67.2 0-37.7 0-24.7 0-22.2 0-21.5 0-8.5
23.7 25.0 20.6 11.0 2.6 1.2 0.5
MedianlSD
I
Range
20.7 12.0 16.7 6.2 0 0 0
20.7 24.4 21.0 13.1 4.8 " 3. ! 1.6
0-66.5 0-87.0 0-72.5 0-41.5 0-17.5 0-10.2 0-6.0
5.2
5.5
0-17.9
Comparison of two arch wire O'pes tested over 14 days 4.2
0.2-13.6
6. I
Mann-Whitney, p = 0.9 (NS).
with Flex (Twistflex, multistranded, steel arch wire). All of the mean values are shown up to day 7, together with summary statistics on the basis of averages for the first 15 days. No statistically significant differences were found between the two arch wires for the pain response over the first 2 weeks9 The data on analgesic consumption (reflecting the pain response), although more coarse, gave a similar result but are not included here, again for the sake of brevity. ~6 Eighteen of 21 patients with Niti recorded pain after 24 hours (86%), as did 16 of 21 patients with Flex (76%); the difference between these proportions does not approach statistical significance ( • 0.62; p > 0.05). Fig. 1 is a graph to contrast the different pain re-
sponses after extraction (stage I), after first arch wire (stage II), and after second arch wire (stage I11). Fig. 2 in a similar way plots the pain experience against time to contrast the pain experience for the two arch wires under test. Mann-Whitney tests were applied to thefirst arch wire data to test for differences between the dental arches ( u p p e r / l o w e r ) - p = 0.34 (NS); gender - p = 0.14 (NS); and social class (1 and 11 versus other) - p = 0.31 (NS). Spearman rank correlations were constructed to examine the association (if any) between pain, age, and initial crowding9 A statistically significant correlation was found between age and pain (+0.34), but no correlations of statistical significance were found either between anterior crowding and pain ( - 0 . 2 4 ) or overall
378 Jones attd Chan
Am. J. Orthod. Dentofac. Orthop. October 1992
\ ,o
.o..~.~ ".~176 %~ ""... T \ "-.
\
NiTI
flex
\
\
\\
"-... \
"-.
"..o...
,~.,~ 9. - . . . . . .
~. .
i
z
i
|
i
i
2
3
q
5
6
7
.
.
.
. i
8
9
TIME (IN DAYS)
Fig. 2. A comparison of mean pain experience (VAS) versus time for two aligning arch wires in study (Niti = Japanese Niti; T-flex = twistllex or multiflex steel).
crowding and pain ( - 0 . 1 2 ) . More information on these variables and the method of measurement for the crowding is available elsewhere. ~4"16~9 DISCUSSION
Three methods were used to assess the patients initial pain response after extraction of a premolar tooth, the placement of a first initial arch wire, and the placement of a second initial arch wire in the opposing dental arch. A daily record of the pain experienced over the first 15 days was recorded by means of marks made on a visual analogue scale at four time points during each 24 hours. These VAS measurements, unavoidably generated a considerable volume of data that is summarized in Table IIA. The patients in the study were surprisingly conscientious in completing these questionnaires with only a few "missing entries" being evident. As may be seen, there was a very large individual variation in pain response. This was as expected and has been found previously.3 Examining the trends indicated bythe mean values, it is apparent that the pain experiences after the placement of the first and second arch wires were very similar (no statistically significant difference), but that the postextraction pain tended to be very much less than the pain found after arch wire. All of the mean values in Table IIA appear quite small, but then it should be remembered that the majority of the pain experience occurred over the first 3 days, while the means are calculated over 15 days; more than 50% of e'fich'sei of results in Tables IIA and B are zeros. When the data are examined in individual detail, it was found that while some patients experienced very little pain, in
others, at least over the first few days, it was considerable. A separate questionnaire completed at 24 hours, was given to every subject in the study. This comprised of an unsophisticated "yes/no response" format, however, it does indicate that in the arch wire groups 81% of the patients were experiencing recordable discomfort at this point in time, whereas in the postextraction group only 28% were experiencing any discomfort. This difference after 24 hours was found to be of very high statistical significance. The third method of pain assessment used in this study was by analgesic consumption. Overall, this somewhat coarse measure of pain showed a similar pattern to the VAS scores (Table liB), however, it was apparently more affected by individual variation. Presumably this was often a matter of whether a person preferred to avoid taking medicines or was keen to take analgesics on a preventive basis (usually before going to bed). There are, of course, many other variables that may affect the consumption of drugs, when it is left to the person to decide on their use. The analgesic data for 17 patients who were followed through stages I, II, and III of the study were examined in more detail with the Spearman rank correlations. This suggested a positive statistically significant correlation (0.6) between the mean postextraction pain (VAS) and the analgesic consumption. However, there was no significant correlation between the analgesic consumption after extraction and after arch wire (0.3 NS). This finding would suggest that the degre e of pain had less effect on analgesic consumption postarch wire and would confirm that some patients were tending to take analgesics
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on a pain preventive basis perhaps before going to bed. A statistically significant correlation was found between the number of occasions analgesics were taken after extraction and after arch wire (0.5) implying that there were subjective variations in analgesic need. In other words, some patients took more analgesics than did others, regardless of the procedure performed. Such findings confirm the impression that the recording of analgesic consumption can only provide a fairly coarse assessment of pain response. Pain after extraction
In 18 subjects at 2100 hours on the day of the extraction, the mean pain rose to a peak (~ = 20.6). This subsequently fell away rapidly with less than half of the patients recording any pain the next morning (0900 hours per median = 0). Some suggestion of diurnal variation was found in these results, however, it is inconclusive since the data were dominated by the recordings from the first 24 hours (Table IV). To summarize, after extraction the prevalence and intensity of pain was low and appeared to be of short duration. Pain after the first arch wire
In 42 subjects the mean recorded pain score was found to rise to a peak at 0900 hours on the day after placement of the fixed appliance (mean = 32.5). As may be seen in Table III the results then show firmer evidenceof a diurnal variation with pain tending to be worse at 2100 > 1700 > 0900 > 1300 hours. The prevalence and intensity of pain in this group was considerably greater than in the postextraction group (Table IV). It was also of longer duration with half of the patients still experiencing pain 5 days later. However, usually the pain appeared to decrease quite rapidly after the third day (Fig. 1). This data broadly agrees with Wilson et a l . 4 who also found a peak in the orthodontic pain response about 24 hours after the placement of either separators or arch wires. Pain after the second arch wire
The pattern of the data for the pain experience of 21 subjects on the placement of a second initial arch wire in the opposing dental arch was broadly similar to that for the first arch wire (Table III, Fig. 1), and no statistically significant difference was found between the means. Comparison of the pain experience
In this part of the study the subjects acted as their own control, and the power of this section was therefore considerably enhanced by matched pairing. It has already been mentioned that the pain experience after
placing an arch wire (whether first or second) was significantly greater than that found after extraction (Table IV; p = 0.003). Similarly, the pain duration was also much lower after extraction than after the first arch wire (1 versus 4 days). When this part of the data was examined by means of a rank correlation matrix (Spearman), a highly significant correlation (p < 0.01) was found between the pain scores after extraction and after arch wire, which when examined further confirmed a consistent individual response. Thus a high individual postextraction score usually led to a high postarch wire score. In practice, this was probably related to a consistent individual pain threshold linked with a consistent recording being made on the VAS. Although this behavior might appear highly subjective, at the same time it is predictable and is easy to manage in the statistical analysis. This finding of a high level of intrarater reliability on the VAS across time for varying discomfort is similar to that of previous authorsJ The pain experience for those subjects receiving their first and then second arch wires (stages II and III) was very similar although the duration was slightly reduced on placement of the second arch wire. In addition, a questionnaire on pahz locality (described elsewhere ~6) suggested that pain of increased duration was less related to the teeth and more to the soft tissues (lip and cheeks). In the case of the second arch wire, soft tissue inflammation or ulceration might be expected to be less of a problem as the patient has become more accustomed to the appliance, with a reduced tendency to catch the cheeks with the brackets, for example, during chewing. Other than this, there appeared to be no conditioning effect of the first arch wire pain response on that for the second arch wire (p = 0.87). Comparison of pain experience with two different arch wires
As may be seen earlier in this article, the two arch wire groups were found to be well matched for all other variables that might affect the pain response. Early in the study it appeared that in some patients who had received the Niti wire there was an atypical pain response, the initial pain reducing over the first 2 to 3 days as normal but then increasing again 2 to 3 days later. This perhaps being related to the very different physical properties of this type of superelastic wire. However, once all the data had been collected, it became apparant that there was no difference of either clinical or statistical significance between the Twistflex and Niti wires in either the prevalence, the nature, or the duration of the pain experience (Table V). Further, no statistically significant differences could be found between the two sets of data by any method of analysis,
380
Jones and Chart
for example, Mann-Whitney testing of the produced means gave a value of p = 0.9. Fig. 2 demonstrates more graphically the similarity of the recorded pain with the two types of arch wires. In the patient questionnaire at 24 hours, no significant difference was found in those experiencing pain between the two arch wire types. Therefore, it would appear that in a multivariate phenomenon like pain, where there is great individual variation in its interpretation, the type of initial arch wire employed (however desirable its physical properties) might be expected to have little effect on the overall pain experience of a clinicians' caseload of patients. To check the comparability of initial crowding between the groups, measurements were taken from the pretreatment casts in every case. It might be expected that for a constant bracket size the more severe the degree of crowding, the more reduced the interbracket span and the greater the force being exerted. 2~ If the degree of initial crowding is any indicator of the force being exerted on the teeth, it would appear from this assessment with these light arch wires that force was not a consistent factor in the production of pain. This finding agreed with a previous but less sophisticated study by one of the authors '~ and is consistent with the beliefs of Gianelli and Goldman 2' and the current thinking at the biochemical level.:'Some studies 2325 have suggested that pain might be related to gender and social class. In the current study no differences were found for these two variables. Similarly, no differences of statistical significance could be detected between the dental arches, despite the consistent difference in interbracket width. This again suggests that force may not be an important factor in the initial orthodontic pain experience. It is of interest that other researchers 26 into pain have found it to be more common and lasts longer in "pain-prone families." In a previous study 3 it was found that patients over t6 years of age generally experienced greater pain than those below this age. It would appear that even below 17 years (as were all the patients in this study) that age is of some significance in the level of pain to be expected after placement of an arch wire (p < 0.05). To summarize, initial orthodontic pain is a multifactorial phenomenon, as indeed is any pain response. As has been observed before, t~psychologic, emotional, attentional, cognitive, and motivational factors all play their part. There is a tremendous individual variation with attendant differences in the pain threshold, however, these differences would appear to be consistent, in that in this study a patient with a relativel)71~igher recorded postextraction pain usually also reported a relatively higher postarch wire pain.
Am. J. Orthod. Dentofac. Orthop. October 1992
It would appear that the level and duration of pain experienced by a patient on placement of an arch wire (applying forces to the teeth for the first time) usually will be greater than that experienced after extraction. In some persons this pain response can be quite severe and last for several days, however, usually it tails-off within 2 to 3 days. Most patients will experience some pain after the placement of an arch wire, and this will tend to be worse at night. It may therefore be worth considering routine prescription of analgesics during the early stages of orthodontic treatment. It was found in the study ~6 that pain was usually reported to come from the teeth themselves (p = 0.004) with any other pain being reported as coming from the surrounding soft tissues as a result of irritation or inflammation (p = 0.03), no evidence was found of referred pain. The postarch wire pain response was not related to the type of wire used nor to the degree of initial crowding suggesting that with these lighter arch wires that force was not an important factor in causing pain or discomfort during the early stages of fixed appliance orthodontics. CONCLUSIONS
1. The prevalence, intensity, frequency, and duration of pain (and analgesic consumption) was much higher for patients after insertion of an arch wire than after a dental extraction. 2. The pain tended to peak the morning after the placement of the arch wire but thereafter showed a consistent diurnal variation, with evening and nights showing the highest scores. 3. The pain experience showed great individual variation, being severe and prolonged in some patients. Typically, however, most patients experienced some pain after receiving a fixed appliance. This pain was worst over the first 2 to 3 days and gradua.lly tailed-off toward the fifth or sixth day. 4. There was no evidence of conditioning by a previous painful experience (first arch wire) on the subsequent perception of pain (second arch wire). However, the pain tailed-off quicker in the second arch wire group, and this was probably related to there being fewer problems with soft tissue trauma (cheek ulceration). 5. The prevalence, intensity, and duration of pain (and analgesic consumption) after the insertion of a Niti arch wire was similar to that for the insertion of a Twistflex steel arch wire. 6. No difference in recorded pain was found between the dental arches.
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7. T h e d e g r e e o f initial c r o w d i n g did not h a v e an effect o n the s u b s e q u e n t d e g r e e o f pain. 8. G e n d e r a n d social class w e r e not f o u n d to b e statistically significant v a r i a b l e s in the p a i n response. 9. A s i g n i f i c a n t a s s o c i a t i o n w a s f o u n d b e t w e e n the a g e o f the patient a n d the s u b s e q u e n t postarch w i r e pain (the g r e a t e r the age, the w o r s e the pain). 10. T h e p e r c e p t i o n a n d i n t e r p r e t a t i o n o f the pain e x p e r i e n c e w a s h i g h l y s u b j e c t i v e but p r e d i c t able. P a t i e n t s that e x p e r i e n c e d m o r e p a i n a f t e r e x t r a c t i o n also e x p e r i e n c e d m o r e pain a f t e r a r c h wire. T h e r e f o r e p a t i e n t s s h o w e d a n indiv i d u a l c o n s i s t e n c y in b o t h t h e i r pain t h r e s h o l d a n d t h e i r pain r e s p o n s e to s t i m u l u s . We acknowledge the assistance of Dr. R. Newcombe (Department of Medical Computing/Statistics, UWCM) for his help in drawing up the protocol and performing the statistical analysis. We are also grateful to the audio-visual aids department, Mr. Mike Hill, and to Mrs. Lynette James for their help. Finally, our thanks to the elinicians who participated in this study.
REFERENCES I. Oliver RG, Knapman YM. Attitudes to orthodontic treatment. Br J Orthod 1985;12:!79-88. 2. Patel V. Non-completion of orthodontic treatment: a study of patient and parental factors contributing to discontinuation in the hospital service and specialist practice. [MScD dissertationl University of Wales, 1989 tteath Park. 3. Jones ML. An investigation into the initial discomfort caused by placement of an archwire. Eur J Orthod 1984;6:48-54. 4. Wilson S, Ngan P, Kess B. Time course of the discomfort in young patients undergoing orthodontic treatment. Paediatr Dent 1989;1 !:107-10. 5. Burstone CJ. Biomechanics of tooth movement. In: Krause BS. ed. Vistas in orthodontics. Philadelphia: Lea & Febiger, 1964. 6. Storey E, Smith R. Force in orthodontics and its relation to tooth movement. Aust J Dent 1952;56:11-8. 7. Reitan K. Selecting forces in orthodontics. Trans Eur Orthod Soc 1956;32:108-25. 8..Hixon EH. Optimal force, differential force and anchorage. AM J ORTtIOD 1969;55:437-57. 9. Boester KA, Johnston IE. A clinical investigation ofthe concepts of differential and optimal force in canine retraction. Angle Orthod 1974;44:113-9.
I0. Jones ML, Richmond S. Initial tooth movement: force application and pain--a relationship? AM J ORTtIOD 1985;88:i 1I-6. II. Burstone CJ, Goldberg AJ. Beta titanium: a new orthodontic alloy. A.,,t J ORTIIOD 1980;77:121-32. 12. Miura F, Masa Kuni M, Yoshiaki O. Hamanaka H. The superelastic property of the Japanese Niti alloy wire for use in orthodontics. AM J O~TIIOD DErrrorAc O~TnOP 1986;90:1-10. 13. O'Brien KD. A randomised controlled clinical trial of aligning archwires. BOC abstract. Br J Orthod 1987;14:315. 14. Jones ML, Staniford H, Chan C. Comparison of super-elastic Niti and multistranded stainless steel wires in initial alignment. J Clin Orthod 1990;XXIV:61 I-3. 15. O'Brien KD, Lewis D, Shaw W, Combe E. A clinical trial of aligning archwires. Eur J Orthod 1990;12:380-4. 16. Chan LSC. Pain and discomfort experienced during orthodontic treatment: a randomised controlled clinical trial of two initial aligning archwires. [MScD dissertation] Heath Park: University of Wales, 1990. 17. Richmond S. Recording the dental cast in three dimensions, AM J ORTnOD DENTOFACORTIIOP 1987;92:119-206. 18. Jones ML. A quantitative three dimensional assessment of treatment change in a consecutively referred sample of malocclusion from a Welsh town. [PhD thesis] Heath Park: University of Wales, 1987. 19. Jones ML. The Barry project - a further assessment of occlusal treatment change in a consecutive sample: crowding and arch dimensions. Br J Orthod 1990;17:269-85. 20. Creekmore TO. The importance of interbracket width in orthodontic tooth movement. J Clin Orthod 1976;X:530-534. 21. Gianelly AA, Goldman HM. Biologic basis of orthodontics. Philadelphia: Lea & Febiger, 1971:164-5. 22. Walker JA, Francis ST, Harris EF, Wakelyn C, Desiderio DM. The Enkephalin response in human tooth pulp to orthodontic force. AM J ORmOD DENTOFACORTIIOP 1987;92:9-16. 23. Feinmann C, Ong M, Harvey W, Harris M. Psychological factors influencing post-operative pain and analgesic consumption. Br J Oral Max Surg 1987;25:285-92. 24. Apley J. The child with abdominal pains. London: Blackwell Scientific, 1975. 25. Apley J, Naish N. Recurrent abdominal pain: a field survey of 1000 school children. Arch Dis Child 1958;33:165-70. 26. Apley J, Hale B. Children with recurrent abdominal pain: how do they grow up? Br Med J 1973;3:7-9. Reprint requests to: Dr. M . L Jones Department of Child Dental Health University of Wales College of Medicine Heath Park, Cardiff, CF4 4XY Wales, United Kingdom
P a i n and discomfort after the insertion of an initial arch wire are common experiences among orthodontic patients. It has been reported that fear of pain is a key factor in discouraging patients from seeking orthodontic treatment. ~ Further, another author2 has found that a small but significant proportion of patients (8%) discontinue treatment because of the pain experienced in the early stages of appliance therapy. It would appear that the problem is extensive, however, only a limited number of studies have specifically investigated the subject. Previously, one of the authors 3 has used a combination of"numerical pain scaling" and "recorded analgesic consumption" in an initial evalu-. ation of the frequency of pain response after insertion of the first arch wire in an edgewise appliance. A significant proportion of patients were found to score at least one session in a day as "experiencing severe or moderate discomfort." It was found that the majority of these positive responses occurred in the first 8 days after placement of the fixed appliance, whereas the most
From the University of Wales College of Medicine. *Senior Lecturer and Consultant in Orthodontics. **Registrar in Orthodontics. 811131349
severe scores were within the first 3 days. No significant difference in pain response was found between the sexes although age appeared to be an important factor: patients over 16 years of age scoring a consistently higher pain/discomfort response, which was also often more prolonged. More recently, another study4 has found that patients receiving orthodontic treatment (involving either placement of seperators or an initial arch wire) recorded a significantly higher degree of dental discomfort than those in a control group. In addition, those patients rating high scores after 4 hours showed a trend towards a similar response both after 24 and 168 hours. Burstone5 has classified the pain response into three different degrees: 1. First degree pain--produced by heavy pressure placed on the tooth with an instrument. This is usually elicited most easily by applying the force in the same direction as the fixed appliance. The patient is not aware of first degree pain unless the orthodontist manipulates the teeth being actively moved with the appliance. 2. Second degree pain--characterized by pain or discomfort during tooth clenching or heavy "biting." The patient maintains the ability to masticate a normal diet without difficulty.
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3. Third degree pain--present when the patient is suffering from spontaneous pain or is unable to masticate food of a normal consistency. However, the boundaries o f these various degrees o f pain are imprecise. Burstone 5 also identified an immediate and delayed pain response: the former being related to the initial compression of the periodontal ligament; and the latter, which commenced a few hours later, produced by a large range of force values and representing, as he termed it, hyperalgesia of the ligament. It is a traditional belief that there is a definite relationship between the force applied to a tooth and the pain experienced2 This theory being in line with the early classical histologic studies 6.7 which promoted the idea of light differential forces as being more efficient, biologic, and less painful. However, other authors 8~~ have failed to confirm a strong association between the force being applied and the subsequent pain. Over the last few years there have been rapid developments in the field of preformed alloy arch wires, these wires replacing, in many clinics, the more traditional light or braided steel arch wires in the role of initial tooth alignment. Beta titanium," it has been claimed, is likely to cause less discomfort by virtue of its low stiffness and high springback; delivering force values of less than half of that for stainless steel of the same dimension. More recently, "superelastic" archwires have become popular for tooth alignment. ~2 Again, similarly, since these wires deliver a constant force over an extended portion of the deactivation range, it has been claimed that "tooth movement occurred more effectively and patients did not experience discomfort". However, there has been only limited research into the clinical effectiveness of these types of arch wire. '3~50'Brien ~3"~ for example, in a randomized trial could not find any significant difference in initial alignment between two alloy arch wires. The present study is intended to test whether any significant difference in the pain/discomfort experience could be found between two types of initial aligning arch wires currently in use in an orthodontic clinic. These two archwires are a superelastic alloy, 0.014inch heavy Japanese Niti (GAC International Inc., Central Islip, N.Y.) and a multistrand steel, 0.015-inch Twistflex (Unitek Corp., Monrovia, Calif.) Further, it is also intended in this study to examine the general phenomenon of initial pain/discomfort in fixed appliance treatment.
METHOD A protocol was drawn up and approved by the Dental Ethics Panel of the University of Wales College of Medicine
Am. J. Orthod. Dentofac. Orthop. October 1992
and, as a part of this process the necessary sample size was selected on the basis of calculations from the results for a previous study by one of the authors2
Criteria for patient selection Forty-three consecutive patients attending the Orthodontic Clinic at the UWCM were admitted to the study on the basis that they were willing to participate and satisfied the following criteria: 1. The patient required extraction of at least one premolar tooth and the placement of a full arch edgewise fixed appliance, 0.018 • 0.030-inch standard (triple control) preadjusted bioprogressive brackets (Rocky Mountain Orthodontics, Denver, Colo.) 2. There was no relevant medical history to affect the dental extraction under local anesthesia. 3. No molar band, palatal arch, Nance button, or quadhelix present on entry to trial were either active or causing discomfort. 4. No extraoral traction was to be used over the period of the study. 5. Patients were to be under the age of 17 years. This was to avoid further complications in the study design since otherwise sampling adjustments would have been necessary to address an age related finding in a previous study2 6. Informed and witnessed consent was obtained from patients, parents/guardian and the general dental practitioner who originally referred each patient.
PROTOCOL The study was divided into three stages: Stage I: Investigation into the pain and discomfort after extraction (used as a control). Stage II: Investigation into the pain and discomfort after the insertion of the first arch wire in either upper or lower arches. Stage III: Investigation into the pain and discomfort after the insertion of the second arch wire in the opposing arch to stage II. All 43 patients participated in stage II of the study; 18 of these participated in stage I, and 22 participated in stage III. Tables IA and IB demonstrate the combinations of arch wires used in the study and their order of allocation. Further detail of the protocol is available elsewhere. '6 However, the same verbal instructions and questionnaires were given to each patient: 1. Daily record of painldiscomfort. This measured by means of 100 mm visual analogue scales (VAS) the pain at four periods during each 24 hours; at 0900, 1300, 1700, and 2100 hours over 15 days. 2. Your painl discomfort after24 hours. A questionnaire to detail the location and frequency of the pain and "back-up" the VAS section. 3. Tablet consumption. Since it was thought that patients would take analgesics when in severe pain in any event, it was considered prudent to standardize the drug. Paracetamol tablets (Arthur H. Cox & Co.,
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Table IA. To demonstrate the various
Table lB. To demonstrate the order in which the different wires were applied to the dental arches
combinations of arch wires used in this study
First arcll wire Niti Flex TOTAL
Second arch wire Niti
l
Flex
l
None
[ Total
5 6
6 5
1! 10
22 21
11
11
21
43
Niti, Niti alloy arch wire. Flex, Multiflex steel arch wire. London, England), were prescribed to every patient together with a record sheet. The patients in the study were instructed to take the tablets for the relief of pain to their own regimen. This provided a complementary measure of pain experience, as well as providing a means of identifying any times of day at which analgesics might have affected the reading.
Crowding assessment All initial study casts of the patients in the study were assessed for the degree of initial croffding by three-dimensional digitization with the Reflex Metrograph (Ross Instruments, Salisbury, Wiltshire, U.K.). This has been described previously'7'z8as has the error of the method? 8
Other variables Age, sex, and social class were recorded for every patient.
Statistical analysis All responses from the questionnaires were stored, coded, and analyzed with the Minitab package (Minitab, Inc., University Park, Pa.). Standard methods of analysis were used including the Mann-Whitney and Wilcoxon tests for quantitative variables and the Chi-square, unpaired, and paired (McNemar) tests for binary ones. Associations between continuous variables were evaluated by the Spearman rank correlations. Analyses took account of the fact that each person contributed a large number of values for the VAS scores, which were not to be treated as if independent; subject means were used in significance tests. The levels of statistical significance employed in all tests were p -< 0.05, statistically significant; p --< 0.01, statistically highly significant; p --< 0.001, statistically very highly significant.
RESULTS O f the 45 patients originally admitted to the study, two failed to return any questionnaires and therefore were excluded. Of the 43 remaining, one patient failed to return a stage II questionnaire and another a stage III questionnaire. Arranging the extractions (stage I) within the clinic for other dentists' patients was not without its difficulties, and therefore this was discontinued when a sufficient number of patients had been
First archwire
Second arch wire UpperlLowerlNone
I Total
Upper Lower
-10
12 --
9 1._22
2I 2._22
TOTAL
10
12
21
43
collected. Twenty-one patients later proceeded to stage III, where it was appropriate to place a wire in the opposing arch. On initial analysis of the data, the groups undergoing examination were found to be well matched for sex, age, social class, and degree of initial crowding, z6 For example, the median age for those receiving a Niti wire was 159.5 months, while for the Twistflex wire it was 158.0 months; the age range for the patients in the study was 113 to 202 months. The term time pohzt in the results refers to a single entry on the visual analogue scale at a certain time and day. Table IIA shows the mean and SD of scores per time point over the first 15 days of the study. This is recorded after extraction, after the first arch wire, and after the second arch wire. The visual analogue assessment of pain was supported by a record of sessional analgesic consumption. Table liB shows summary statistics for the number and pattern of occasions when analgesics were taken. An examination of the overall data in this way demonstrated a very large difference between the initial extraction group and the first and second arch wire groups, whichever the method of pain assessment examined (Tables IIA and B). In Table IV this is subsequently shown to be highly statistically significant. No significant difference was found between the means for the stage II and stage III arch wires. The range of values, however, were great (extraction, maximum 79; first and second arch wire, maximum 100), which encouraged further examination of the data in more detail. As part of the questionnaire the patients in the study were asked by means of a verbal assessment to describe their discomfort after 24 hours. Only 5 of 18 (28%) patients had pain 24 hours after extraction, compared with 34 of 42 (81%) and 17 of 21 (81%) after first and second arch wires (one result for each of the latter being unrecorded). A McNemar test comparing extraction with first arch wire shows a highly significant difference (p = 0.008). To examine the diurnal variation in pain response, Table III illustrates the mean pain recorded at each time
Am. J. Orthod.Denmfac.Orthop. October 1992
Jones and Chan
376
T a b l e IIA. Summary statistics for pain score per
T a b l e liB. Summary statistics for analgesic
time point over first 15 days of study for all patients
consumption per day over first 15 days of study
Extraction Number of pain score entries Missing entries Mean SD
First arch wire
1044
2436
0 1.5 6.3
I Second arch wire
Extraction Number of entries Missing entries Mean SD
1218
58 5.7 14.7
58 5.6 14.8
First arch wire
Second arch wire
270
630
315
0
15
15
0.07 0.34
0.12 0.45
0.11 0.45
T a b l e III. Mean pain score of the first 10 time points after first arch wire in 42 subjects (diurnal variation in
pain response)
Time of day (time point, hours)
]
17.00 21.00 9.00 13.00
Mean
[
Median
15.9 25.9 32.5 31.3 27.0 23.9 20.4 17.5 18.3 18.8
17.00
21.00 9.00 13.00 17.00 21.00
[
SD
4.5 12.0 37.0 27.0
]
Ma.titnum
24. l 28.4 25.8 27.8
94.0 100.0 76.0 84.0
17.5
27.1
85.0
19.0 16.0 7.0 16.5 14.0
25.9 23. I 21.5 18.6 18.9
89.0 87.0 87.0 56.0 60.0
Table IV. Comparison of mean daily pain scores (VAS) for stages I and I1 of the study
Extraction stage ! Number
Mean
Median
SD
7.5 0 0 0 0 0 0
12.16 6.99 4.13 3.14 2.25 1.61 1.62
1
17
I 1.79
2 3 4 5 6 7
17 17 17 17 17 17
3.76 1.75 1.35 0.91 0.68 0.65
All
17
! .65
First arch wire stage II Ma.~imum 37.75 19.75 15.75 10.50 8.00 6.25 5.00
Mean
[ Median l
SD
l
Ma~imum
23.84 20.31 14.93 7.57 1.93 0.59 0.53
19.25 4.0 3.75 1.0 0 0 0
23.42 28.10 20.03 13.23 4.22 2.43 2.06
88.00 87.00 72.50 41.50 15.25 10.00 8.50
5.43
17.98
Comparison over 14 days for e.ttractionlfirst arch wire groups 0.75
2.27
7.57
5.12
2.38
**Wileoxon test, p = 0.003.
point in the day (with the VAS). It was found that the highest score tended to be on the morning after the arch wire was inserted, with evenings or nights tending to score more highly thereafter. However, it is of note that only nine stage I and five stage II respondents of those completing the 24-hour assessment (n = 43) recorded the pain as disturbing their sleep; this amounted to a 22% positive response. Table IV shows the mean recorded pain per time point for each day, comparing the extraction with the
first arch wire group. The second arch wire data are very similar to that of the first arch wire and are excluded for the sake of brevity. A statistically very significant difference was found between the two groups, a much increased and longer recorded pain response being found in both of the arch wire groups. The same 17 patients are followed through in Table IV, In Table V the day-by-day pain scores are shown in a similar way to Table IV, but collected in this instance to compare Niti (Japanese niti alloy arch wire)
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Special article 377
3O
l i t AW
20 F-
i ~
8 z ~.
\\
I IO.
\ '.
2nd A W ~
la
,L.
I
9
2
3
II
5
6
7
$
9
10
TIME (IN DAYS}
Fig. 1. To demonstrate and compare mean pain score (VAS) versus time for each procedure. (Ext = postextraction group; 1st AW = first arch wire group; 2nd AW = second arch wire group).
Table V. Comparison of mean daily pain scores (VAS) for the two arch wires
NiTi arch wire (n = 21) Day
MeanlMedianlSO
l 2 3 4 5 6 7
29.0 19.6 12.6 5.5 4.1 2.9 1.2
23.0 17.5 11.5 1.3 0.5 0 0
All
5.7
3. I
Flex arch wire (n = 21) I
22.4 21.2 I 1.4 7.9 6.1 6.2 2.5
Range
Mean
3.7-88.0 0-67.2 0-37.7 0-24.7 0-22.2 0-21.5 0-8.5
23.7 25.0 20.6 11.0 2.6 1.2 0.5
MedianlSD
I
Range
20.7 12.0 16.7 6.2 0 0 0
20.7 24.4 21.0 13.1 4.8 " 3. ! 1.6
0-66.5 0-87.0 0-72.5 0-41.5 0-17.5 0-10.2 0-6.0
5.2
5.5
0-17.9
Comparison of two arch wire O'pes tested over 14 days 4.2
0.2-13.6
6. I
Mann-Whitney, p = 0.9 (NS).
with Flex (Twistflex, multistranded, steel arch wire). All of the mean values are shown up to day 7, together with summary statistics on the basis of averages for the first 15 days. No statistically significant differences were found between the two arch wires for the pain response over the first 2 weeks9 The data on analgesic consumption (reflecting the pain response), although more coarse, gave a similar result but are not included here, again for the sake of brevity. ~6 Eighteen of 21 patients with Niti recorded pain after 24 hours (86%), as did 16 of 21 patients with Flex (76%); the difference between these proportions does not approach statistical significance ( • 0.62; p > 0.05). Fig. 1 is a graph to contrast the different pain re-
sponses after extraction (stage I), after first arch wire (stage II), and after second arch wire (stage I11). Fig. 2 in a similar way plots the pain experience against time to contrast the pain experience for the two arch wires under test. Mann-Whitney tests were applied to thefirst arch wire data to test for differences between the dental arches ( u p p e r / l o w e r ) - p = 0.34 (NS); gender - p = 0.14 (NS); and social class (1 and 11 versus other) - p = 0.31 (NS). Spearman rank correlations were constructed to examine the association (if any) between pain, age, and initial crowding9 A statistically significant correlation was found between age and pain (+0.34), but no correlations of statistical significance were found either between anterior crowding and pain ( - 0 . 2 4 ) or overall
378 Jones attd Chan
Am. J. Orthod. Dentofac. Orthop. October 1992
\ ,o
.o..~.~ ".~176 %~ ""... T \ "-.
\
NiTI
flex
\
\
\\
"-... \
"-.
"..o...
,~.,~ 9. - . . . . . .
~. .
i
z
i
|
i
i
2
3
q
5
6
7
.
.
.
. i
8
9
TIME (IN DAYS)
Fig. 2. A comparison of mean pain experience (VAS) versus time for two aligning arch wires in study (Niti = Japanese Niti; T-flex = twistllex or multiflex steel).
crowding and pain ( - 0 . 1 2 ) . More information on these variables and the method of measurement for the crowding is available elsewhere. ~4"16~9 DISCUSSION
Three methods were used to assess the patients initial pain response after extraction of a premolar tooth, the placement of a first initial arch wire, and the placement of a second initial arch wire in the opposing dental arch. A daily record of the pain experienced over the first 15 days was recorded by means of marks made on a visual analogue scale at four time points during each 24 hours. These VAS measurements, unavoidably generated a considerable volume of data that is summarized in Table IIA. The patients in the study were surprisingly conscientious in completing these questionnaires with only a few "missing entries" being evident. As may be seen, there was a very large individual variation in pain response. This was as expected and has been found previously.3 Examining the trends indicated bythe mean values, it is apparent that the pain experiences after the placement of the first and second arch wires were very similar (no statistically significant difference), but that the postextraction pain tended to be very much less than the pain found after arch wire. All of the mean values in Table IIA appear quite small, but then it should be remembered that the majority of the pain experience occurred over the first 3 days, while the means are calculated over 15 days; more than 50% of e'fich'sei of results in Tables IIA and B are zeros. When the data are examined in individual detail, it was found that while some patients experienced very little pain, in
others, at least over the first few days, it was considerable. A separate questionnaire completed at 24 hours, was given to every subject in the study. This comprised of an unsophisticated "yes/no response" format, however, it does indicate that in the arch wire groups 81% of the patients were experiencing recordable discomfort at this point in time, whereas in the postextraction group only 28% were experiencing any discomfort. This difference after 24 hours was found to be of very high statistical significance. The third method of pain assessment used in this study was by analgesic consumption. Overall, this somewhat coarse measure of pain showed a similar pattern to the VAS scores (Table liB), however, it was apparently more affected by individual variation. Presumably this was often a matter of whether a person preferred to avoid taking medicines or was keen to take analgesics on a preventive basis (usually before going to bed). There are, of course, many other variables that may affect the consumption of drugs, when it is left to the person to decide on their use. The analgesic data for 17 patients who were followed through stages I, II, and III of the study were examined in more detail with the Spearman rank correlations. This suggested a positive statistically significant correlation (0.6) between the mean postextraction pain (VAS) and the analgesic consumption. However, there was no significant correlation between the analgesic consumption after extraction and after arch wire (0.3 NS). This finding would suggest that the degre e of pain had less effect on analgesic consumption postarch wire and would confirm that some patients were tending to take analgesics
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on a pain preventive basis perhaps before going to bed. A statistically significant correlation was found between the number of occasions analgesics were taken after extraction and after arch wire (0.5) implying that there were subjective variations in analgesic need. In other words, some patients took more analgesics than did others, regardless of the procedure performed. Such findings confirm the impression that the recording of analgesic consumption can only provide a fairly coarse assessment of pain response. Pain after extraction
In 18 subjects at 2100 hours on the day of the extraction, the mean pain rose to a peak (~ = 20.6). This subsequently fell away rapidly with less than half of the patients recording any pain the next morning (0900 hours per median = 0). Some suggestion of diurnal variation was found in these results, however, it is inconclusive since the data were dominated by the recordings from the first 24 hours (Table IV). To summarize, after extraction the prevalence and intensity of pain was low and appeared to be of short duration. Pain after the first arch wire
In 42 subjects the mean recorded pain score was found to rise to a peak at 0900 hours on the day after placement of the fixed appliance (mean = 32.5). As may be seen in Table III the results then show firmer evidenceof a diurnal variation with pain tending to be worse at 2100 > 1700 > 0900 > 1300 hours. The prevalence and intensity of pain in this group was considerably greater than in the postextraction group (Table IV). It was also of longer duration with half of the patients still experiencing pain 5 days later. However, usually the pain appeared to decrease quite rapidly after the third day (Fig. 1). This data broadly agrees with Wilson et a l . 4 who also found a peak in the orthodontic pain response about 24 hours after the placement of either separators or arch wires. Pain after the second arch wire
The pattern of the data for the pain experience of 21 subjects on the placement of a second initial arch wire in the opposing dental arch was broadly similar to that for the first arch wire (Table III, Fig. 1), and no statistically significant difference was found between the means. Comparison of the pain experience
In this part of the study the subjects acted as their own control, and the power of this section was therefore considerably enhanced by matched pairing. It has already been mentioned that the pain experience after
placing an arch wire (whether first or second) was significantly greater than that found after extraction (Table IV; p = 0.003). Similarly, the pain duration was also much lower after extraction than after the first arch wire (1 versus 4 days). When this part of the data was examined by means of a rank correlation matrix (Spearman), a highly significant correlation (p < 0.01) was found between the pain scores after extraction and after arch wire, which when examined further confirmed a consistent individual response. Thus a high individual postextraction score usually led to a high postarch wire score. In practice, this was probably related to a consistent individual pain threshold linked with a consistent recording being made on the VAS. Although this behavior might appear highly subjective, at the same time it is predictable and is easy to manage in the statistical analysis. This finding of a high level of intrarater reliability on the VAS across time for varying discomfort is similar to that of previous authorsJ The pain experience for those subjects receiving their first and then second arch wires (stages II and III) was very similar although the duration was slightly reduced on placement of the second arch wire. In addition, a questionnaire on pahz locality (described elsewhere ~6) suggested that pain of increased duration was less related to the teeth and more to the soft tissues (lip and cheeks). In the case of the second arch wire, soft tissue inflammation or ulceration might be expected to be less of a problem as the patient has become more accustomed to the appliance, with a reduced tendency to catch the cheeks with the brackets, for example, during chewing. Other than this, there appeared to be no conditioning effect of the first arch wire pain response on that for the second arch wire (p = 0.87). Comparison of pain experience with two different arch wires
As may be seen earlier in this article, the two arch wire groups were found to be well matched for all other variables that might affect the pain response. Early in the study it appeared that in some patients who had received the Niti wire there was an atypical pain response, the initial pain reducing over the first 2 to 3 days as normal but then increasing again 2 to 3 days later. This perhaps being related to the very different physical properties of this type of superelastic wire. However, once all the data had been collected, it became apparant that there was no difference of either clinical or statistical significance between the Twistflex and Niti wires in either the prevalence, the nature, or the duration of the pain experience (Table V). Further, no statistically significant differences could be found between the two sets of data by any method of analysis,
380
Jones and Chart
for example, Mann-Whitney testing of the produced means gave a value of p = 0.9. Fig. 2 demonstrates more graphically the similarity of the recorded pain with the two types of arch wires. In the patient questionnaire at 24 hours, no significant difference was found in those experiencing pain between the two arch wire types. Therefore, it would appear that in a multivariate phenomenon like pain, where there is great individual variation in its interpretation, the type of initial arch wire employed (however desirable its physical properties) might be expected to have little effect on the overall pain experience of a clinicians' caseload of patients. To check the comparability of initial crowding between the groups, measurements were taken from the pretreatment casts in every case. It might be expected that for a constant bracket size the more severe the degree of crowding, the more reduced the interbracket span and the greater the force being exerted. 2~ If the degree of initial crowding is any indicator of the force being exerted on the teeth, it would appear from this assessment with these light arch wires that force was not a consistent factor in the production of pain. This finding agreed with a previous but less sophisticated study by one of the authors '~ and is consistent with the beliefs of Gianelli and Goldman 2' and the current thinking at the biochemical level.:'Some studies 2325 have suggested that pain might be related to gender and social class. In the current study no differences were found for these two variables. Similarly, no differences of statistical significance could be detected between the dental arches, despite the consistent difference in interbracket width. This again suggests that force may not be an important factor in the initial orthodontic pain experience. It is of interest that other researchers 26 into pain have found it to be more common and lasts longer in "pain-prone families." In a previous study 3 it was found that patients over t6 years of age generally experienced greater pain than those below this age. It would appear that even below 17 years (as were all the patients in this study) that age is of some significance in the level of pain to be expected after placement of an arch wire (p < 0.05). To summarize, initial orthodontic pain is a multifactorial phenomenon, as indeed is any pain response. As has been observed before, t~psychologic, emotional, attentional, cognitive, and motivational factors all play their part. There is a tremendous individual variation with attendant differences in the pain threshold, however, these differences would appear to be consistent, in that in this study a patient with a relativel)71~igher recorded postextraction pain usually also reported a relatively higher postarch wire pain.
Am. J. Orthod. Dentofac. Orthop. October 1992
It would appear that the level and duration of pain experienced by a patient on placement of an arch wire (applying forces to the teeth for the first time) usually will be greater than that experienced after extraction. In some persons this pain response can be quite severe and last for several days, however, usually it tails-off within 2 to 3 days. Most patients will experience some pain after the placement of an arch wire, and this will tend to be worse at night. It may therefore be worth considering routine prescription of analgesics during the early stages of orthodontic treatment. It was found in the study ~6 that pain was usually reported to come from the teeth themselves (p = 0.004) with any other pain being reported as coming from the surrounding soft tissues as a result of irritation or inflammation (p = 0.03), no evidence was found of referred pain. The postarch wire pain response was not related to the type of wire used nor to the degree of initial crowding suggesting that with these lighter arch wires that force was not an important factor in causing pain or discomfort during the early stages of fixed appliance orthodontics. CONCLUSIONS
1. The prevalence, intensity, frequency, and duration of pain (and analgesic consumption) was much higher for patients after insertion of an arch wire than after a dental extraction. 2. The pain tended to peak the morning after the placement of the arch wire but thereafter showed a consistent diurnal variation, with evening and nights showing the highest scores. 3. The pain experience showed great individual variation, being severe and prolonged in some patients. Typically, however, most patients experienced some pain after receiving a fixed appliance. This pain was worst over the first 2 to 3 days and gradua.lly tailed-off toward the fifth or sixth day. 4. There was no evidence of conditioning by a previous painful experience (first arch wire) on the subsequent perception of pain (second arch wire). However, the pain tailed-off quicker in the second arch wire group, and this was probably related to there being fewer problems with soft tissue trauma (cheek ulceration). 5. The prevalence, intensity, and duration of pain (and analgesic consumption) after the insertion of a Niti arch wire was similar to that for the insertion of a Twistflex steel arch wire. 6. No difference in recorded pain was found between the dental arches.
Special article
Volume 102
381
Number 4
7. T h e d e g r e e o f initial c r o w d i n g did not h a v e an effect o n the s u b s e q u e n t d e g r e e o f pain. 8. G e n d e r a n d social class w e r e not f o u n d to b e statistically significant v a r i a b l e s in the p a i n response. 9. A s i g n i f i c a n t a s s o c i a t i o n w a s f o u n d b e t w e e n the a g e o f the patient a n d the s u b s e q u e n t postarch w i r e pain (the g r e a t e r the age, the w o r s e the pain). 10. T h e p e r c e p t i o n a n d i n t e r p r e t a t i o n o f the pain e x p e r i e n c e w a s h i g h l y s u b j e c t i v e but p r e d i c t able. P a t i e n t s that e x p e r i e n c e d m o r e p a i n a f t e r e x t r a c t i o n also e x p e r i e n c e d m o r e pain a f t e r a r c h wire. T h e r e f o r e p a t i e n t s s h o w e d a n indiv i d u a l c o n s i s t e n c y in b o t h t h e i r pain t h r e s h o l d a n d t h e i r pain r e s p o n s e to s t i m u l u s . We acknowledge the assistance of Dr. R. Newcombe (Department of Medical Computing/Statistics, UWCM) for his help in drawing up the protocol and performing the statistical analysis. We are also grateful to the audio-visual aids department, Mr. Mike Hill, and to Mrs. Lynette James for their help. Finally, our thanks to the elinicians who participated in this study.
REFERENCES I. Oliver RG, Knapman YM. Attitudes to orthodontic treatment. Br J Orthod 1985;12:!79-88. 2. Patel V. Non-completion of orthodontic treatment: a study of patient and parental factors contributing to discontinuation in the hospital service and specialist practice. [MScD dissertationl University of Wales, 1989 tteath Park. 3. Jones ML. An investigation into the initial discomfort caused by placement of an archwire. Eur J Orthod 1984;6:48-54. 4. Wilson S, Ngan P, Kess B. Time course of the discomfort in young patients undergoing orthodontic treatment. Paediatr Dent 1989;1 !:107-10. 5. Burstone CJ. Biomechanics of tooth movement. In: Krause BS. ed. Vistas in orthodontics. Philadelphia: Lea & Febiger, 1964. 6. Storey E, Smith R. Force in orthodontics and its relation to tooth movement. Aust J Dent 1952;56:11-8. 7. Reitan K. Selecting forces in orthodontics. Trans Eur Orthod Soc 1956;32:108-25. 8..Hixon EH. Optimal force, differential force and anchorage. AM J ORTtIOD 1969;55:437-57. 9. Boester KA, Johnston IE. A clinical investigation ofthe concepts of differential and optimal force in canine retraction. Angle Orthod 1974;44:113-9.
I0. Jones ML, Richmond S. Initial tooth movement: force application and pain--a relationship? AM J ORTtIOD 1985;88:i 1I-6. II. Burstone CJ, Goldberg AJ. Beta titanium: a new orthodontic alloy. A.,,t J ORTIIOD 1980;77:121-32. 12. Miura F, Masa Kuni M, Yoshiaki O. Hamanaka H. The superelastic property of the Japanese Niti alloy wire for use in orthodontics. AM J O~TIIOD DErrrorAc O~TnOP 1986;90:1-10. 13. O'Brien KD. A randomised controlled clinical trial of aligning archwires. BOC abstract. Br J Orthod 1987;14:315. 14. Jones ML, Staniford H, Chan C. Comparison of super-elastic Niti and multistranded stainless steel wires in initial alignment. J Clin Orthod 1990;XXIV:61 I-3. 15. O'Brien KD, Lewis D, Shaw W, Combe E. A clinical trial of aligning archwires. Eur J Orthod 1990;12:380-4. 16. Chan LSC. Pain and discomfort experienced during orthodontic treatment: a randomised controlled clinical trial of two initial aligning archwires. [MScD dissertation] Heath Park: University of Wales, 1990. 17. Richmond S. Recording the dental cast in three dimensions, AM J ORTnOD DENTOFACORTIIOP 1987;92:119-206. 18. Jones ML. A quantitative three dimensional assessment of treatment change in a consecutively referred sample of malocclusion from a Welsh town. [PhD thesis] Heath Park: University of Wales, 1987. 19. Jones ML. The Barry project - a further assessment of occlusal treatment change in a consecutive sample: crowding and arch dimensions. Br J Orthod 1990;17:269-85. 20. Creekmore TO. The importance of interbracket width in orthodontic tooth movement. J Clin Orthod 1976;X:530-534. 21. Gianelly AA, Goldman HM. Biologic basis of orthodontics. Philadelphia: Lea & Febiger, 1971:164-5. 22. Walker JA, Francis ST, Harris EF, Wakelyn C, Desiderio DM. The Enkephalin response in human tooth pulp to orthodontic force. AM J ORmOD DENTOFACORTIIOP 1987;92:9-16. 23. Feinmann C, Ong M, Harvey W, Harris M. Psychological factors influencing post-operative pain and analgesic consumption. Br J Oral Max Surg 1987;25:285-92. 24. Apley J. The child with abdominal pains. London: Blackwell Scientific, 1975. 25. Apley J, Naish N. Recurrent abdominal pain: a field survey of 1000 school children. Arch Dis Child 1958;33:165-70. 26. Apley J, Hale B. Children with recurrent abdominal pain: how do they grow up? Br Med J 1973;3:7-9. Reprint requests to: Dr. M . L Jones Department of Child Dental Health University of Wales College of Medicine Heath Park, Cardiff, CF4 4XY Wales, United Kingdom
