The aim of this randomized trial was to investigate the effect of the use of a sugar-free chewing gum vs ibuprofen on reported pain in orthodontic patients.
This was a 2-arm parallel design randomized controlled trial in 9 sites in the southwest of England. Patients about to undergo orthodontic treatment with maxillary and mandibular fixed appliances were recruited and randomly allocated to an experimental chewing gum group or a control ibuprofen group. Eligibility criteria included patients undergoing fixed maxillary and mandibular appliance therapy, aged 11 to 17 years, and able to use ibuprofen and chewing gum. The primary outcome measure was pain experienced after appliance placement using a mean of 3 recordings on a scale of 0 to 10. Secondary outcome measures were pain experienced in the subsequent 3 days, pain after the first archwire change, ibuprofen use, and appliance breakages. Pain scores were recorded with a questionnaire and posted to a collection center by each patient. Randomization was by means of a central telephone service and comprised computer-generated random numbers used to generate a sequential allocation list, with permuted blocks of variable size (2 and 4) and stratified by center. Neither the clinicians nor the patients were blinded to the intervention. Patients in the control group were permitted to use ibuprofen only, and patients in the experimental group were allowed to use ibuprofen if they did not get sufficient analgesia from the chewing gum. Data were analyzed using the principle of intention to treat with multilevel modeling to reflect the structured nature of the data (scores within patient within site).
One thousand patients were recruited and randomized in a ratio of 1:1 to the chewing gum and ibuprofen (control) groups. The male-to-female ratios were similar in the groups. The pain questionnaire response rates were good at approximately 84% and 83% after appliance placement (chewing gum group, 419; ibuprofen group, 407) and 70% and 71% after the first archwire change (chewing gum group, 343; ibuprofen group, 341). The primary outcomes were similar for the 2 groups: mean pain scores, 4.31 in the chewing gum group and 4.17 in the ibuprofen group; difference, 0.14 (95% CI, −0.13 to 0.41). There was a suggestion that the relative pain scores for the 2 groups changed over time, with the chewing gum group experiencing slightly more pain on the day of bond-up and less on the subsequent 3 days; however, the differences had no clinical importance. There were no significant differences for the period after archwire change. The reported use of ibuprofen was less in the chewing gum group than in the ibuprofen group; after appliance placement, the mean numbers of occasions that ibuprofen was used were 2.1 in the chewing gum group and 3.0 in the ibuprofen group (adjusted difference, −0.96 [95% CI, −0.75 to −1.17; P <0.001]); after archwire change, the figures were 0.8 and 1.5 occasions (difference, −0.65 [−0.44 to −0.86; P <0.001]). After appliance placement and the first archwire change, there was no clinically or statistically significant difference in appliance breakages between the chewing gum and ibuprofen groups after either bond-up (7% and 8.8%, respectively) or the first archwire change (4.2% and 5.5%, respectively). No adverse events were reported.
The use of a sugar-free chewing gum may reduce the level of ibuprofen usage but has no clinically or statistically significant effect on bond failures.
International Standard Randomised Controlled Trial Number (79884739) and National Institute of Health Research (6631) portfolios.
This research was supported by an award by the British Orthodontic Society Foundation.
Chewing sugar-free gum might help orthodontic patients to use less ibuprofen.
Chewing sugar-free gum had no statistically significant effect on bond failures.
It is well recognized that one of the most frequent side effects of orthodontic treatment involving fixed or removable appliances is pain as a result of tooth movement. Pain has been reported to affect between 70% and 95% of children undergoing treatment, and its intensity and duration vary from patient to patient, typically beginning 2 to 3 hours after appliance fitting and lasting up to 7 days, with maximum intensity at 2 days. Throughout an average 18- to 24-month course of orthodontic treatment, pain is not a 1-time event and may be reported after each adjustment, particularly if an archwire is changed. For most patients, this pain affects eating; for some, it may also affect sleep. Pain experienced as a result of orthodontic treatment has been cited as a major barrier to treatment acceptance and the principal reason for its discontinuation, which in 1 study was as high as 8%. This has economic implications not only for patients and their families, but also for any publicly funded health service.
Why orthodontic pain occurs is still unknown, but it has been described in a review by Krishnan as possibly caused by the pressure, ischemia, and inflammation induced in the periodontal ligament during tooth movement. This leads to changes in blood flow, the release of mediators such as prostaglandins, and resultant hyperalgesia. This is most likely an oversimplification, because the neural pathways involved in pain are complex and are also known to be intimately related to the patient’s emotional state, including fear, anxiety, and mood.
Analgesics such as ibuprofen or paracetamol are often used to alleviate orthodontic pain. Sometimes they are taken preemptively, before a fitting or an adjustment appointment, but more often are taken as the teeth become painful after such an appointment. Both drugs, although effective in reducing pain, can cause adverse reactions. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) whose analgesic action is thought to occur peripherally through its ability to inhibit the synthesis of prostaglandins at a site of tissue injury. It has been suggested that prostaglandin inhibition may cause slowing of orthodontic tooth movement, leading some to question whether orthodontic patients should use NSAIDs for pain relief, as that could prolong the treatment. However, at present the clinical significance of NSAIDs on orthodontic tooth movement is unclear, particularly if they are taken for only short times, at the beginning and at intervals during treatment.
To date, largely anecdotal evidence has suggested that chewing gum may provide some pain relief and either eliminate or reduce the need for other forms of analgesics. However, the effectiveness of chewing gum has not been widely investigated, probably because of fear that gum chewing might increase the frequency of appliance breakages. A small randomized controlled trial (57 patients aged 11-18 years) on the effect of chewing gum on the impact of fixed appliance therapy, including its effect on pain, suggested that chewing gum not only lessens the impact, but also reduces the level of pain experienced. Both the gum and no-gum groups were permitted to take analgesics if required. However, how much and which analgesics were taken were not recorded, merely whether any were taken. Although it was reported that there was no statistically significant difference in whether analgesics were used by the 2 groups, it is not possible to determine whether the effect of chewing gum for pain relief was additive or whether 1 group took more analgesics than the other.
Specific objectives and hypotheses
The primary objective of this trial was to investigate the effect of the use of a sugar-free chewing gum on reported pain after the fitting of full maxillary and mandibular fixed appliances. The secondary objectives were to investigate the effect of a sugar-free chewing gum on reported pain in the subsequent 3 days and after the first archwire change, on ibuprofen use, and on the number of appliance breakages.
Material and methods
Trial design and any changes after trial commencement
The investigation comprised a prospective 2-arm parallel design multicenter randomized controlled trial in 9 hospital orthodontic departments in the southwest of England with a 1:1 allocation ratio. Ethics committee (08/H0106/139), Research and Development, and Medicines and Healthcare Products Regulatory Agency (Eudract 2008-005522-36) approvals were obtained, and the trial was registered on the International Standard Randomised Controlled Trial Number (79884739) and National Institute for Health Research (6631) portfolios. The primary outcome measure was pain experienced on the day of appliance placement. The secondary outcome measures were pain experienced in the subsequent 3 days, pain experienced after the first archwire change, the use of chewing gum or ibuprofen at each time period, and the number of appliance breakages.
There were no changes to the trial after its commencement.
Participants, eligibility criteria, and settings
One thousand consecutive patients aged between 11 and 17 years who were about to have maxillary and mandibular fixed appliances fitted were recruited for the study. Because this was a pragmatic clinical-effectiveness trial to determine whether there was any difference between chewing gum and ibuprofen in the management of orthodontic pain, it was designed to reflect the real world across 9 trial centers. There was therefore no stipulation as to the types of fixed appliances, aligning wires, ligation methods, malocclusions, numbers of teeth to be extracted or not before commencement, or the seniority of the orthodontists recruiting and treating the patients. There were specific exclusion criteria: patients with a history of (1) hypersensitivity to ibuprofen or any of the other ingredients; (2) hypersensitivity reactions to aspirin or other NSAIDs including asthma, rhinitis, or urticaria; (3) current or previous peptic ulceration or bleeding of the stomach; and (4) severe heart failure.
Information leaflets explaining the proposed study were given to the patients and their parents; then they were invited to complete a written consent form.
Immediately after the fitting of the appliances, each patient was randomly allocated to either the experimental group (chewing gum) or the control group (ibuprofen).
Once recruited, patients in the intervention group were given sugar-free chewing gum (Orbit; Wrigley, Thame, United Kingdom) and ibuprofen (250-mg tablets; Wockhardt UK, Wrexham, United Kingdom). They were instructed to use the chewing gum for pain relief if required after the fitting of their maxillary and mandibular fixed appliances but were also told that they could take the ibuprofen for pain relief if the chewing gum was not effective. Information on maximum dosage and frequency of use were provided. The patients also received a pain questionnaire to complete, detailing their pain experience and what they took to deal with the pain over the 3 days after appliance placement. The pain questionnaire comprised a series of identical numeric pain rating scales. Each rating scale contained 11 points and ranged from no pain (0) to worst pain imaginable (10). The patients were instructed to record the degree of discomfort when biting and chewing at 2 hours after appliance placement, 6 hours after placement, at bedtime on the day of the appointment, at bedtime the next day, at bedtime 2 days after the appointment, and at bedtime 3 days after the appointment, according to the protocol of Bradley et al. If the 6-hour reading coincided with bedtime, only 1 reading was used. They were also asked to record at each time what was taken and when during the first 3 days after appliance placement.
The patients in the control group were given ibuprofen (250-mg tablets; Wockhardt UK) and were instructed to use it for pain relief if required after the fitting of their maxillary and mandibular fixed appliances. As per normal practice, the patients were told not to chew gum while wearing their fixed appliances. Information on maximum dosage and frequency of ibuprofen use were also provided. As in the intervention group, the patients were asked to complete the questionnaire detailing their pain experiences and what they took to deal with the pain over the 3 days after appliance placement.
Follow-up appointment, first archwire change
At the next routine adjustment appointment at which the archwires were changed, the patients were given the same analgesic regimen (intervention group, chewing gum and ibuprofen; control group, ibuprofen) and instructions and asked to complete another pain questionnaire on their experiences and usage over the next 3 days. The patients received postage-paid reply envelopes for returning the questionnaires to the coordinating center for the trial.
At each of the 2 appointments after the fitting of the appliances, any appliance breakage was also recorded. At this point, the treating orthodontist was blinded to the group allocation.
Sample size calculation
The primary outcome measure was the mean pain experienced after appliance placement or adjustment. The results of a much smaller study, with a continuous visual analog scale (VAS), were initially used to perform a sample size calculation assuming a standard deviation of 20 mm on a 100-mm VAS pain scale. This indicated that complete data on 394 patients per trial arm would give power of 80% to detect a difference of 4 mm in the means of the readings with a 2-tailed t test. Allowing for a 20% loss to follow-up required 493 subjects per trial arm; we therefore aimed to recruit and randomize a total of 1000 patients. However, with 6 time intervals for each intervention period (appliance placement and then initial archwire change), this would have required the reproduction and measurement of 14,000 10-cm VAS lines. Therefore, we decided to record pain experience using a categorical scale from 0 (no pain) to 10 (worst pain imaginable) at 2 hours, 6 hours, and bedtime up to 3 days. Not only would a categorical scale, rather than a continuous VAS, aid in data collection and database entry, but it would also reduce the chances of bias in the reproduction of the scale on photocopying and subsequent measurements.
The randomization strategy comprised computer-generated random numbers used to generate a sequential allocation list, with permuted blocks of variable size (2 and 4) and stratified by center. This list was generated by the Research Design Service Co-ordinating Centre in Taunton and remained secure from the recruiting clinicians. Allocation to a trial arm was determined by central telephone randomization once a patient was recruited.
Neither the clinicians nor the patients were blinded to the intervention. However, the person performing the data entry and the statistician were blinded to the intervention.
All statistical analyses were conducted on the basis of the intention-to-treat principle as far as possible. For the primary outcome of pain on the day of bond-up, the characteristics of patients with missing data were considered. Age was weakly predictive of missing information, but sex was not predictive. Multiple imputations of the missing data using age and treatment group were performed, and the results were similar to those obtained from complete questionnaires; for simplicity, only the latter results are presented. The primary outcome was compared between groups using mixed-effects linear models, with treatment group as a fixed effect and center as a random effect.
Further analyses of pain scores were conducted using multilevel modeling. Measurements were taken at 6 time points after bond-up and similarly at 6 time points after archwire changes. Mixed-effects linear models included treatment group, visit (bond-up or archwire change), and time point as fixed factor effects (with inclusion of interactions as necessary, determined by likelihood ratio tests comparing models with and without each interaction), with center as a random effect and individual (nested within center) also as a random effect. With this structure, a linear mixed-effects model was fitted for pain scores and the number of times that ibuprofen was used, whereas a logistic mixed-effects model was used for whether ibuprofen was used at all.
The data were analyzed using Stata software (version 14.0, Stata; StataCorp, College Station, Tex).