Pain experience in adults undergoing treatment: A longitudinal evaluation

Pain is a near pervasive unpleasant experience encountered during orthodontics, which can impair compliance and lead to avoidance or discontinuation of treatment and failed appointments.¹  Patients are often apprehensive in relation to both orthodontic extractions and pain attached to treatment, with potential impacts on quality of life and compliance.²  Most studies investigating the pain experience in orthodontics have focused on preadolescents and adolescents, with relatively little known in relation to the duration and severity of orthodontic pain among adults.^3,4  It is therefore surprising, particularly as treatment continues to become more accepted in adult populations and better informed patients demonstrate a more positive attitude toward treatment.^3,5–8  Moreover, the literature concerning the initial pain experience has typically focused on the first week following appliance placement,^9–12  with relatively few studies evaluating more prolonged effects.^3,13 

Orthodontic pain has been related to a range of factors, such as the degree of malalignment, analgesic use, and the type of appliance used.^2,9,12  A recent Cochrane review¹⁴  concluded that there was no significant difference in the type of initial aligning archwire with the pain experienced. Furthermore, bracket type has not been linked to variation in pain experience.¹⁵  Given that these mechanical factors seem to have little association with pain experience, detailed epidemiological data that may better allow prediction of the timing and severity of pain experience among adult populations would be welcomed.

Thus, the present study aimed to address these shortcomings in the literature and primarily evaluated the longitudinal pain experience in adults undergoing orthodontic treatment. Secondary outcomes assessed the relationship between pain experience and analgesic consumption, dental irregularity, gender, and age.

Ethical approval was obtained for a prospective longitudinal cohort study (Ref QMREC2013/82). Adults (older than 18 years) were recruited by five specialist orthodontists, undertaking adult orthodontic treatment in the South East of England. Subjects who were due to receive fixed orthodontic treatment alone, in the absence of any supplementary arch expansion or anchorage reinforcement, were included. Subjects requiring separation for band placement; demonstrating periodontal disease, temporomandibular joint dysfunction, or craniofacial syndrome; or who were prescribed analgesics or antidepressants for chronic medical conditions or psychiatric disease were excluded.

Training and calibration were organized for all clinicians involved in treating the potential adult participants, emphasizing the nature of the study, method of standardizing occlusal photographs, appliance placement, ligation method, and archwire sequencing for the three subsequent appointments. Following written informed consent, standardized occlusal photographs were obtained at baseline (T0). All patients received a bonded preadjusted Edgewise fixed appliance (0.022 × 0.028-inch slot size), in either the upper arch only or both arches. The initial archwire following bracket placement was a standardized 0.014-inch super-elastic nickel-titanium, to be relegated at the first (T1) and replaced with a standardized 0.016-inch super-elastic nickel-titanium at the second (T2) routine follow-up adjustment appointment, with each appointment being 6 (±1) weeks apart. Archwires were engaged using elastomeric ligatures only, avoiding full engagement at the bond-up appointment for notably displaced teeth. After placement of the orthodontic appliance (T0), subjects were asked to record their pain experience, using a visual analogue scale (VAS), at 4 hours, 1 day, and then each consecutive day for a total of 7 days and any analgesic use, in terms of the type of medication, dosage, and frequency. This was repeated after T1 and T2 routine follow-up adjustment appointments. The VAS had an unmarked horizontal 100-mm line, with no pain and extreme pain at either end. Subjects were asked to mark a vertical line along the VAS, which best represented their pain intensity, at the given time points. For the purpose of data analysis, the VAS scores were reduced to four time points: 4 hours, 24 hours, 2 and 3 days, and 4–7 days after the adjustment.

Questionnaires were returned using a prepaid self-addressed envelope to the host institute. With regard to protocol deviations, all subjects who failed an appointment were sent a further appointment and telephoned to confirm attendance. Any patients wishing to withdraw from the study were free to do so at any point with the assurance that it would not affect their continuing care.

Baseline data included demographic characteristics. Little's irregularity index (LI; 29) was used to assess the degree of dental irregularity, from the sum of the linear distances between adjacent contact points from the mesial of the right canine to the mesial of the left canine.¹⁶  This was calculated for each dental arch at baseline (T0) using a digital caliper (150 mm DIN 862, ABSOLUTE Digimatic Calliper, Mitutoyo Standard Model No. 500-191U, Mitutoyo Ltd, Hampshire, UK) with a resolution of ±0.01 mm.

Descriptive statistics were calculated for pain (VAS) scores and analgesic consumption per appointment (T0, T1, and T2) and time point. Consumption of analgesics was aggregated into four time points: 4 hours, 24 hours, 3 days, and 7 days after the adjustment.

Univariable and multivariable random effects linear regression was implemented to evaluate the effect of the irregularity index, appointment, time point, age, and gender on both the VAS score and analgesic consumption counts. Predictors that were not significant at P = .10 in the univariable analysis were excluded from the multivariable analysis. Possible interaction between appointment and time point was also assessed. All analyses were conducted using Stata 15 statistical package (Stata Corp, College Station, Tex).

Between March 2014 and June 2015, a total of 70 subjects who met the study criteria were consecutively recruited. Fifty-eight subjects completed all the questionnaires. Eleven (16%) subjects failed to complete the questionnaires and were lost from the study. Both the demographic and clinical characteristics (dental irregularity) of these 11 patients were examined, and their loss was not found be at risk of introducing bias. One subject was removed because of protocol deviation by use of a different-size initial archwire.

A slightly greater proportion of women (57%) was recruited, with a mean age 34.69 (SD 12.11). The mean baseline (T0) incisor irregularity index score was 7.5 mm (SD 3.9). Only six patients (10%) underwent extraction therapy.

For the second (24 hours) and third (3 days) time points, the VAS scores increased compared with the first (4 hours) time point by 7.69 and 2.75 units, respectively, after adjusting for irregularity and appointment, whereas for the last (7 days) time point, the VAS score decreased by 4.23 units compared with the first time point. The interaction between appointment and time point was not significant (Figure 1; Table 1).

From the univariable unadjusted analysis, it can be seen that only the appointment and time point were significant pain (VAS) score predictors at the P ≤ .10 level of significance. In the multivariable model, no meaningful changes were observed compared with the unadjusted model, with appointment and time point maintaining their strong association with VAS scores. For the second (T1) and third (T2) appointments, the VAS scores decreased compared with the first (T0) appointment by 8.32 and 5.94 units, respectively, after adjusting for dental irregularity and time point (Table 2; Figure 2).

For the second (T1) and third (T2) appointments, there was a decrease in analgesic consumption by 55% and 46% compared with the first appointment, respectively, after adjusting for VAS score, irregularity, age, and time point (Figure 3; Table 3). For the second and third time points, the analgesic consumption increased compared with the first (4 hours) time point, by 84% and 23%, respectively, after adjusting for VAS score, irregularity, age, and appointment. For the last time point (7 days), the analgesic consumption decreased by 48% compared with the first time point. The interaction between appointment and time point was not significant.

From the univariable analysis, it can be seen that pain (VAS) score, dental irregularity, age, appointment (T0, T1, and T2), and time point (4 hours, 24 hours, 3 days, and 7 days after the adjustment) were significant analgesic consumption predictors at the P ≤ .10 level of significance (Figure 3; Table 3). In the multivariable model, only pain (VAS) score, appointment, and time point remained significant predictors of analgesic consumption. For every unit increase in VAS score, there was a 3% increase in total analgesic consumption, after adjusting for dental irregularity, age, appointment, and time point.

This longitudinal study demonstrated that varying levels of pain are experienced during the first week after each appointment, over the first 3 months of treatment. This mirrors the findings from adolescents and is in keeping with limited research evaluating adults.^1,17  This may in turn have a negative impact on quality of life and offers further insight into the findings from a recent prospective study in adolescents, in which a significant reduction in oral health–related quality of life was observed during the first 3 months of treatment, with pain proposed as one of the contributory domains.⁸ 

Pain scores reported over the three appointment intervals were consistent with other studies, in which an equally large individual variation in pain response was observed and can be explained by the subjective nature of pain.^9,10  Arbitrarily, previous investigators have equated a score greater than 54 mm as severe.¹⁸  In the present study, the mean recorded pain score peaked between 24 hours and 3 days in all appointment intervals. Again, these data were consistent with other studies in which the level of discomfort tended to peak at 24 hours and subsequently decreased.^9,19,20  These patterns reflect biochemical changes, with cytokines known to be involved in inflammatory-induced sensitization, which are related to the development of hyperalgesia and known to peak approximately 24 hours following appliance manipulation.²¹  Furthermore, prostaglandins and IL-1, both inflammatory mediators of pain, are also found to peak at 24 hours and to reduce to baseline levels after a period of 1 week to 1 month.²² 

In comparing all three appointments, pain was greatest following the initial bond-up appointment (T0), followed by the second adjustment (T2), with the first adjustment (T1) associated with the lowest pain score. At T0, the heightened pain levels may also be compounded by additional soft-tissue inflammation and ulceration. Soft-tissue discomfort is likely to dissipate over time with adaptation.^23,24  However, an interesting finding was the observed increase in mean pain scores at T2. This may relate to the archwire protocol, with the change to a larger dimension; an increase in diameter from 0.014 to 0.016 inches can raise the force level by 50%. Alternatively, at T2, teeth may be more completely ligated, resulting in higher force. Luppanapornlap et al.²²  concluded that the application of heavy force produced substantially greater pain, which peaked at 24 hours after application.

In the present study, analgesic consumption was similar to that reported in other recent prospective clinical trials based on adolescents, confirming that most adult patients found orthodontic pain to be moderate, resulting in the use of analgesics.^18,20,25  Furthermore, and perhaps not surprisingly, pain scores, appointment type (T0, T1, or T2), and time point (4 hours, 24 hours, 3 days, and 7 days) all predicted analgesic consumption. This confirms that recording analgesic consumption can provide a reliable, if not indirect, assessment of pain response.

In terms of identifying predictors of pain and, in turn, analgesic consumption, multivariate modeling was applied. The current study did not identify the level of dental irregularity as having an influence on pain levels or analgesic use. The evidence of a link among adolescents remains unclear in the literature, with evidence suggesting no correlation^10,16,26  or, indeed, the greater the degree of initial crowding, the higher the level of discomfort reported.⁹  Theoretically, as the amount of dental irregularity increases, the interbracket span reduces and a greater force is exerted.²⁷  However, if elastic ligatures are used, as in the present study, full engagement is not always achieved in cases of severe crowding, translating into reduced pressure, lighter forces and, hence, less pain. This may help to explain the lack of predictability between the level of dental irregularity and pain.

The present study could not identify gender or age as a predictor of pain experience or analgesic use and is consistent with studies in adolescents.^4,9,11  In relation to age, it was difficult to compare the findings from the present study with previous studies, as most of the latter studies combined adolescent and adult patients.

Patient-centered care is a concept that has been introduced recently in health care systems. Among the main elements are a need to understand the patient's treatment needs, experiences, satisfaction, and the perceived overall quality of the health care system.²⁸  With an increasing number of adult patients now seeking orthodontic treatment, there is a growing need for such research in orthodontics. Thus, the current body of work evaluating pain experiences and analgesic use in adults undergoing fixed appliance treatment. Better informing patients of the likely resultant pain experience following appliance placement and subsequent adjustment visits could significantly help manage their expectations and treatment compliance.

The present study was not without its limitations, with subjects recruited from five practices, introducing the potential for inconsistency. However, such inconsistency was limited, with all practitioners undergoing calibration in relation to the study protocol. Moreover, it was felt that recruitment of patients in a specialist practice setting would enhance the generalizability of the findings and better reflect the range and complexity of malocclusion within the adult subpopulation. A further potential limitation was a possibility that patients who had undergone extractions prior to orthodontic treatment may score higher pain levels compared with patients who do not require any extractions for orthodontic treatment.²⁸  However, these represented only 10% of the sample, and to limit any such risk, a minimum hiatus of 2 weeks was adopted between extractions and appliance placement. Fortunately, no patient experienced problems in relation to the extraction site healing.

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  Adults undergoing fixed orthodontic therapy should be advised that they are most likely to experience increased levels of pain for 1 to 3 days following placement of their appliance and subsequent adjustment visits for which analgesic use could be considered.