Subjects and Study Design

In all, 64 patients from the Department of Orthodontics, Faculty of Odontology, Malmö University, Malmö, Sweden, and from one Public Dental Health Service Clinic in Malmö, Skane County Council, Sweden, were consecutively recruited between 2004 and 2009. Sixty-two consented to participate in the study (Figure 1). All patients met the following inclusion criteria: early to late mixed dentition, anterior crossbite with functional shift (at least one maxillary incisor causing functional shift), no cleft lip/palate or syndrome patients, moderate space deficiency in the maxilla (ie, up to 4 mm), a no-extraction treatment plan, an ANB angle >0° (to avoid skeletal Class III patients), and no previous orthodontic treatment.

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The ethics committee of Lund University, Lund, Sweden (Dnr: 3334/2004), approved the protocol, and all patients at the clinic who met the inclusion criteria were invited to enter the study.

After the patients and parents received written information about the study and written consent was obtained by the parents, the 62 participants were randomized by an independent person in blocks of 10 for treatment by removable (RA) or fixed (FA) appliances. Seven opaque envelopes were prepared with 10 sealed notes in each (5 notes for each group). Thus, for every new patient in the study, a note was randomly extracted from the open envelope.

Treatment Methods

Two orthodontists and one postgraduate student in orthodontics, under supervision of an orthodontist, treated all patients according to a preset concept.

In group FA, the fixed appliance consisted of stainless-steel brackets (Victory, slot 0.022 inches, APC PLUS adhesive coated bracket system, 3M Unitek, City, St). Usually, eight brackets were bonded to the maxillary incisors, deciduous canines, and either to the first deciduous molars or the first premolars. All patients were treated according to a standard straight-wire concept designed for light forces.¹³ Archwire sequence was 0.016-inch heat-activated nickel-titanium (HANT), 0.019 × 0.025-inch HANT, and finally 0.019 × 0.025-inch stainless-steel wire. To avoid vertical interlock between incisors, composite was bonded to the occlusal surfaces of both mandibular second deciduous molars. Progress was evaluated every 4 weeks, until anterior crossbite was corrected.

In group RA, the removable appliance comprised an acrylic plate, with a protrusion spring for each incisor in anterior crossbite, bilateral occlusal coverage of the posterior teeth, an expansion screw, and stainless-steel clasps on either the first deciduous molars or first premolars and the permanent molars. The protrusion springs were activated once a month until normal incisor overjet was achieved. The patient was firmly instructed to wear the appliance day and night, except for meals and toothbrushing (ie the appliance was to be worn at least 22 hours a day). Progress was evaluated every 4 weeks, until anterior crossbite was corrected.

Outcome measures were sourced from questionnaires that have previously been shown to be valid and reliable.¹⁴ Two new questions were included (“Do you have pain in your lip?”; “Do you think your orthodontic appliance disturbs your appearance?”).

The patients in both groups completed the questionnaires at a number of time points: before insertion of the appliance (baseline), later on the day of insertion and every day/evening for the following seven days, at the first scheduled appointment after 4 weeks and finally at the second scheduled appointment, 8 weeks after insertion of the appliance (Figure 1). The patients were given instructions on how to complete the questionnaire. About 10 minutes were needed to complete the questionnaire. At baseline and at the first and second scheduled appointments, the patients filled in the questionnaires at the clinic. During the first 7 days of treatment, the patients filled in the questionnaires daily at home. The evaluations of the questionnaires were blinded (ie, the assessor was unaware of the group to which the patient belonged).

Pain and Discomfort

All questions are presented in Table 1. Questions 1 to 7, on pain and discomfort, were graded on a visual analogue scale (VAS) with the end phrases “no pain” and “worst pain imaginable” or “no tension” and “worst tension imaginable.”¹⁴ Question 8 had a binary response (yes/no). For questions 9 and 10, there were multiple-choice responses, whereby one answer was to be selected from the 3 presented (Table 1).

Table 1. Self-reported Questions on Pain and Discomfort From the Teeth, Jaws, Face, and Headache Pain

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Impairment of Jaw Function

There were 15 questions on jaw function: 3 on mandibular function, 5 on psychosocial activities, and 7 on eating specific foods (Table 2). Each item was assessed on a 4-point scale, with the options “not at all,” “slightly,” “very difficult,” or “extremely difficult.”¹⁴

Table 2. Self-reported Questions on Impairment of Jaw Function

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Self-estimated Disturbance to Appearance

One question related to the patient’s perception of the influence of the appliance on personal appearance: “Do you think your orthodontic appliance disturbs your appearance?” and was graded on a VAS with the end phrases “not at all” and “very much.” The question was answered 8 weeks after insertion of the appliance.

Statistical Analysis

Median values and interquartile ranges were calculated for each pain and discomfort assessment variable and the variable for self-estimated disturbance to appearance. Because the normality test with Kolmogorov-Smirnov indicated that a nonparametric test should be used, intergroup differences for these variables were tested with the nonparametric Mann-Whitney test.

For categorical variables, Pearson chi-square tests were used to determine intergroup differences in impairment of jaw function, headache, and affected daily activities. Fisher exact test was used when the expected cell value in a 2 × 2 table was less than 5. Differences with a P value less than 5% (P < .05) were considered statistically significant.

Pain Intensity

The general intensity of pain was low to moderate in both groups, although on day 2, a few children, primarily in the FA group, reported high pain levels. Also, the intensity of pain was significantly higher for fixed appliances on day 1 when maxillary incisors were not in contact (P = .040). Furthermore, on day 2, when maxillary incisors were in contact, the fixed appliance revealed significant higher pain intensity than the removable appliance (Table 3). Overall, the pain intensity peaked after 2 days of treatment in both groups. After 2 days of treatment, no significant difference was found in pain intensity between the groups.

Table 3. Pain Intensity on a Visual Analogue Scale (0–100) From Baseline on Day of Insertion and up to 8 Weeks of Orthodontic Treatment With Fixed or Removable Appliances (Groups FA and RA)^a

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Although the intensity of pain was low, the patients in group RA experienced more pain in their palate (P = .021) after 6 days of treatment. After 7 days, group RA also reported more pain from the lips than the FA group (P = .040).

The difference in pain intensity between group RA and group FA was nonsignificant for any pain-related question at both rescheduled appointments, after 4 and 8 weeks of treatment. Very low levels of pain were experienced in the tongue at any time for both appliances.

Overall, none of the patients reported any use of analgesics during the trial period.

Discomfort

The general self-perceived tension or discomfort revealed low to moderate levels of discomfort for both groups and peaked for both appliances on day 2. On days 2 (P = .015) and 3 (P = .036), patients in group FA experienced more tension in their teeth than patients in group RA (Table 4). On the other hand, patients in group RA experienced slightly more tension in their teeth after 6 (P = .007) and 7 days of treatment (P = .001; Table 4). At no time during treatment was there any significant intergroup difference with respect to tension in the jaws.

Table 4. Discomfort on a Visual Analogue Scale (0–100) From Baseline on Day of Insertion and up to 8 Weeks of Orthodontic Treatment With Fixed or Removable Appliances (Groups FA and RA)^a

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Headache

Before treatment, 5 patients in group RA reported headache 1 to 3 times a month, and in group FA, 5 patients suffered from headache 1 to 3 times a month and 2 patients once or twice a week. After 8 weeks of treatment, 3 of the patients in group RA and 2 in group FA declared that they suffered from headache 1 to 3 times a month. No significant difference between the groups was found at any time.

Impairment of Jaw Function

Daily activities. Seven patients in group RA and three in group FA reported that schoolwork was adversely affected 1 day after the appliance was inserted, with no significant intergroup difference. After 3 days of treatment, schoolwork was reported to be adversely affected by five children in group RA but none in group FA (P = .022). After 4 or more days of treatment, two to five patients in the RA group reported that treatment adversely affected their schoolwork.

After 1 day of treatment, leisure activities were reported to be affected in five of the patients in group RA and six patients in group FA. In group RA, the effect on leisure activities persisted to the final evaluation, while in group FA, none reported effects after 5 days of treatment. Thus, leisure activities were significantly more affected in group RA than FA after 6 days (P = .010) and 4 weeks of treatment (P = .004).

Speech and laughter. Speech was mostly affected after 2 days of treatment, and difficulties were reported significantly more frequently in group RA (22 patients affected) than in group FA (1 patient affected; P = .001). After 3 days of treatment, none of the patients in group FA reported affected speech, while in group RA, 10 patients reported a persistent effect on speech after 8 weeks of treatment (P = .001).

Only a few patients reported difficulty laughing during treatment, but on the day of insertion, patients in group FA experienced significantly more difficulty laughing than those in group RA (P = .040).

Chewing, eating, and drinking. During the first 3 days of treatment, patients in group FA experienced significantly more difficulty biting and chewing hard and soft food than those in group RA (P values between .000 and .031). Eating a carrot or apple was reported to be the most difficult, and patients in group FA still perceived these as significantly more difficult to eat at the 4- and 8-week appointments (P values between .019 and .003). The ability to drink was little affected, with no significant difference between the groups.

Self-estimation of Disturbance to Appearance

No significant intergroup difference was found for self-estimated disturbance of appearance because of the appliances.