Pain and discomfort during the first week of maxillary expansion using two different expanders: patient-reported outcomes in a randomized controlled trial

Summary

Background

Quad Helix (QH) is the appliance most preferred by orthodontists to correct unilateral posterior crossbite in the early mixed dentition while other orthodontists suggest rapid maxillary expansion (RME) on deciduous teeth in these patients.

Objectives

To evaluate and compare perceived pain intensity, discomfort, functional jaw impairment, and analgesic consumption during the first week of treatment with either RME or QH appliances.

Trial design

Two-arm parallel group, two-centre, randomized controlled trial.

Material and methods

Seventy-two patients, mean age 9.5 (SD ±0.8) years, with unilateral posterior crossbite requiring maxillary expansion were randomly allocated to either the RME (22 boys, 14 girls) or QH (22 boys, 14 girls) group. Validated questionnaires were used to assess pain intensity, discomfort, jaw function impairment, and analgesic consumption, on the first, fourth, and seventh days after appliance insertion and activation.

Blinding

Due to clinical limitations, only the outcome assessors were blinded to the groups to which the patients were allocated.

Results

Seventy patients completed the questionnaires. Pain from the tongue and chafe from the appliance were significantly higher in the QH group on the first day of treatment (P = 0.003 and P = 0.000, respectively). On the fourth day, the chafe from the appliance was still significantly higher in the QH group (P = 0.007). Speech was affected in both groups on day 1; this impairment continued and was significantly higher in the RME group days 4 and 7. No significant difference in analgesic consumption was found between the groups at any time. The analgesic consumption was highest at day 1 of treatment.

Harms

No harm was observed in any patient.

Limitations

Double blinding was not possible due to the clinical limitations.

Conclusion

During the initial 4 days of treatment, pain from the tongue and chafe from the appliance caused the most reported inconvenience in the patients in the QH group. A majority of reported visual analogue scale values were in the lower mid-range, suggesting low to moderate pain and discomfort in both groups.

Clinical Trial Registration

NCT04458506

Introduction

Posterior crossbite is a common malocclusion with a prevalence of 11 per cent in European children (1, 2). Posterior crossbite is defined as a malocclusion in the canine, premolar, and molar regions, in which the maxillary buccal cusps occlude lingually to the buccal cusps of the corresponding mandibular teeth. The condition may be bilateral or unilateral, but unilateral crossbites predominate. Posterior crossbites can be treated with fixed or removable expanders, where the fixed expanders are more affective due to independence of cooperation (3). Fixed appliances can expand slow, such as Quad Helix (QH), or with rapid maxillary expansion (RME) such as Haas type or hyrax type expanders. Haas type and hyrax type are considered equally efficient (4).

What is considered the golden standard for correcting unilateral crossbites differs depending on the dental stage but also on the orthodontist’s preferences? In a survey made in Sweden, most orthodontics preferred QH for the treatment of unilateral crossbite, traditionally made with bands on the first permanent molar (5). However, many authors instead suggest RME anchored to the deciduous second molars to avoid undesirable effects on the permanent first molars in order to correct unilateral crossbites in the early mixed dentition (6–11).

When determining treatment for correcting unilateral crossbite, it is also important to take into account the patient perspective on how different treatments are experienced when choosing an appliance, especially when treating children. Children should be given as effective and painless treatment as possible to prevent the development of dental fear (12). In the early mixed dentition, it may be easier to expand the upper arch using less force than later in the early permanent dentition (13, 14) due to the facial sutural maturation and interdigitation in the older cohorts.

At the commencement of orthodontic treatment, patients often experience discomfort (15, 16). Pain and discomfort can occur during the insertion of the appliance and the first 3 days are most inconvenient for the patients. The pain and discomfort fade within 8 days in most cases (17, 18).

The perception of pain and discomfort in children with anterior crossbite treated with either fixed or removable appliances has been shown to cause low to moderate discomfort in both groups (19). Feldmann et al. also found almost the same level of pain and discomfort treating posterior crossbite with two different types of RME appliances in a randomized controlled trial (RCT) (20). However, there is still lack of research exploring perceived pain intensity and discomfort during posterior crossbite treatment. The need for more RCTs with different treatment modalities was confirmed by a recently published systematic review (21).

Thus, the aim of this RCT was to evaluate and compare the patients’ experience of perceived pain intensity and discomfort during the first week of treatment with either RME on the second deciduous molar or QH on the permanent first molar. The null hypothesis was that there are no significant differences between the two appliances.

Materials and methods

This study was a two-centre RCT, with two parallel arms and group allocation on a 1:1 ratio. The Regional Ethical Review Board in Uppsala, Sweden, which follows the guidelines of the Declaration of Helsinki, approved the study protocol (Dnr: 2018/308). The patients and caregivers also had to give their written consent to participate in the study.

Participants, eligibility criteria and setting

Seventy-two patients in the early mixed dentition with unilateral posterior crossbite were examined at the Postgraduate Dental Education Center, Region Orebro County, Sweden, and the Institute for Postgraduate Dental Education, Region Jönköping County, Sweden, from May 2019 to May 2021 (Figure 1).

Figure 1.

Flow diagram of the children and allocation to either rapid maxillary expansion—hyrax type (RME) or quad helix (QH) and bi-centre distribution.

The inclusion criteria were as follows:

• Unilateral posterior crossbite.

• Early mixed dentition: the maxillary first permanent molars had to be erupted and the maxillary deciduous canines and second deciduous molars had to be persisting.

• Class I or Class II molar relation with maximum 5-mm overjet.

• Ability of the patient to comprehend and answer a questionnaire.

Patients with previous or ongoing orthodontic treatment, craniofacial syndromes, or orofacial clefts were considered ineligible for the study.

Randomization and allocation

All 72 participants were randomly allocated in blocks of different sizes, using the concealed allocation principle in a 1:1 ratio. The randomization procedure was as follows: a computer-generated randomization list was created using SPSS software (version 25.0; IBM SPSS, Chicago, IL, USA) and stored with a research secretary. After receiving oral and written information about the clinical trial, the included patients and their parents/guardians signed the consent forms. Each time a patient gave his/her consent, the secretary was contacted to provide the information about which type of expander the patient should receive. Thus, the allocation was concealed.

Clinical interventions

One centre used intraoral scanning (Trios 3, 3Shape, Copenhagen Denmark) for impressions and the other centre used alginate impression (Cavex Orthotrace, Cavex, Haarlem, Holland). The QH (steel wire dimension 0.9 mm) was attached with bands on the first permanent molar (Figure 2a). The RME was a hyrax type with a palatal expander, 13 mm (Leone orthodontic products, Firenze, Italy), attached with bands on the deciduous second molar and bonded to the deciduous canine (Figure 2b). On the deciduous canines, a modest preparation was made on the palatal surface to create a rest seat; next, the anterior arm was bonded at the palatal surface (Tetric EvoFlow, Ivoclar Vivadent AG, Lichtenstein or Transbond PLUS Color Change, 3M, ST Paul, MN, USA). The bands on the QH and RME were cemented (Ketac Cem 3M, St. Paul, MN, USA). Both groups had bite blocks (Ultra Band-Lok, Reliance, IL, USA, or Transbond Plus Light Cure Band, 3M, St. Paul, MN, USA) placed on the maxillary second deciduous molar. The children’s parents/guardians were instructed on how to activate the RME appliance and the first activation was done chair-side by the parent under supervision. The RME was activated a quarter turn (0.2 mm) twice a day to normal transverse relations (the maxillary first molar’s palatal cusp touches the buccal cusp of the mandibular first molar). The QH was activated one molar width before cementation and controlled every 6–12 weeks until normal transverse relations were achieved. All appliances were checked 7–14 days after insertion. The patients were treated by three different experienced clinicians at two centres (SH, RL, EJ). All three clinicians installed both appliances.

Figure 2.

(a) Quad helix (QH) with band on first permanent molars. Bite blocks on the second deciduous molar. (b) Rapid maxillary expansion—hyrax type (RME) with bands on deciduous second molar. Bite blocks on the second deciduous molar.

Questionnaire

The questionnaires included self-reported questions regarding pain intensity, discomfort, analgesic consumption, and jaw function impairment on the first, fourth, and seventh days in treatment (Supplemental Material). The questionnaires have been used previously in several studies and are considered to have acceptable to good reliability and internal consistency (22). In this study, patients were asked to complete the questionnaires on their own but were allowed help from an adult to read the questions. The children received three questionnaires at the time of inserting the appliance. The first one was to be answered on day 1 (the next day within 24 hours after insertion), the second on day 4 and the third questionnaire 7 days after insertion. Children’s parents/guardians helped them to understand some questions when necessary. The first questionnaire included questions about the perception of the insertion (Supplemental Material, questions 1–3) which was not included in the second and third questionnaires. Approximately 10 minutes were needed to complete the questionnaires. Questions concerning pain and discomfort were graded using a visual analogue scale (VAS) with the end phrases ‘no pain’ and ‘worst pain imaginable’ or ‘no discomfort’ and ‘worst discomfort imaginable’. The VAS was measured to the nearest 0.5 mm using a standard 100-mm metric ruler. Questions 3, 10, 14, and 15 had a binary yes/no response with follow-up questions (with space provided for written responses). Questions about functional jaw impairment were assessed using a five-point verbal rating scale (VRS), with the alternatives ‘not at all,’ ‘slightly difficult,’ ‘difficult,’ ‘much difficult,’ and ‘extremely difficult’ (22).

Primary outcome

Patients’ perception of pain and discomfort during the first week of treatment.

Secondary outcome

Analgesic consumption between the groups and possible gender differences within and between the groups.

Sample size

The calculated sample size for each group was based on a significance level of 0.05 and 90 per cent power to detect a difference of 10 mm (SD ±12) in pain levels between the two groups on a VAS between the groups. The standard deviation was adapted from an earlier study (14). The sample size calculation indicated that 31 patients would be required in each group. To compensate for dropouts, we decided to include 36 patients in each group (an addition of 15 per cent per group).

Registration

This trial was registered at ClinicalTrials.gov, ID NCT04458506 and Researchweb.org project number 260581.

Blinding

Due to the nature of the intervention, it was not possible to blind the patients or the practitioners to the appliances; however, the outcome assessors were blinded to the groups to which the patients were allocated.

Statistical analysis

Mann–Whitney test was used to compare VAS- and VRS-scaled variables between study groups. Wilcoxon paired rank-sum test for VAS variables and marginal homogeneity test for VRS variables were used to compare changes within groups between days 1 and 7. Chi-2 test or Fischer exact test when appropriate was used to compare binary variables between groups. Because of many outcome variables evaluated, we use a significance level 0.01 for all statistical tests, to avoid type 1 error, in other words, to reduce the risk of false significant findings. SPSS version 27 (Armonk, NY: IBM Corp) was used for all statistical calculations.

Results

Of 72 randomized patients, one patient in the RME group declined to start any treatment due to family reasons, and one in the QH group did not hand in any questionnaires. Patient characteristics are displayed in Table 1. A total of 70 patients (97 per cent) replied and handed in the questionnaires.

Table 1.

Patient characteristics

	QH group (n = 35)	RME group (n = 35)
Age, mean (SD, min–max)	9.5 (0.7, 8.4–11.5)	9.5 (0.9, 8.5–12.1)
Girls, n (%)	37.1% (13 of 35)	37.1% (13 of 35)
Age among girls, mean (SD, min–max)	9.3 (0.7, 8.4–10.6)	9.4 (1.0, 8.5–12.1)
Age among boys, mean (SD, min–max)	9.6 (0.7, 8.5–11.5)	9.6 (0.8, 8.5–11.6)

Experience after insertion of the appliance (Supplemental Material, questions 1–3)

The patients’ experience of inserting the dental appliance was equal between groups, 40.3 per cent in total declared that they experienced discomfort during the insertion (Table 2). Free text comments were widely spread, but nine comments were related to trying out the appliance, four mentioned the minimal preparation on the deciduous canines as uncomfortable, some thought that the bite block was worst and two children wrote that the polishing paste was most unpleasant. There were no statistically significant differences between the three operators concerning pain and discomfort during the insertion of the appliances (P = 0.48).

Table 2.

Comparing experience at the first day after insertion of the appliance and pain, discomfort, daily activities variables at days 1, 4, and 7 between quad helix (QH) and rapid maxillary expansion—hyrax type (RME) groups.

	All (n = 70)		QH group (n = 35)		RME group (n = 35)		P 1
Experience the first day after insertion of the appliance	n	Median (IQR)	n	Median (IQR)	n	Median (IQR)
1. Did you experience pain during the insertion of the appliance?	69	14 (0–31)	35	6 (0–31)	34	21 (2–34)	0.13
2. Did you experience discomfort during the insertion of the appliance?	67	20 (4–50)	34	24 (2–52)	33	19 (4–50)	0.72
3. Did you experience any part of the insertion of the appliance as uncomfortable?	40.3% (27 of 67)		35.3% (12 of 34)		45.5% (15 of 33)		0.40
Pain and discomfort from mouth, teeth and jaws
10. Have you taken any analgesic today? (Day 1)	40.6% (28 of 69)		45.7% (16 of 35)		35.3% (12 of 34)		0.38
10. Have you taken any analgesic today? (Day 4)	15.7% (11 of 70)		17.1% (6 of 35)		14.3% (5 of 35)		0.74
10. Have you taken any analgesic today? (Day 7)	1.4% (1 of 69)		0.0% (0 of 34)		2.9% (1 of 35)		>0.99
Daily activities
14. Have you stayed home from school today due to pain from your appliance? (Day 1)	17.4% (12 of 69)		17.1% (6 of 35)		17.6% (6 of 34)		0.96
14. Have you stayed home from school today due to pain from your appliance? (Day 4)	1.4% (1 of 70)		2.9% (1 of 35)		0.0% (0 of 35)		>0.99
14. Have you stayed home from school today due to pain from your appliance? (Day 7)	0.0% (0 of 69)		0.0% (0 of 34)		0.0% (0 of 35)		N.A.
15. Have you refrained from leisure activities today because of pain from your appliance? (Day 1)	13.0% (9 of 69)		11.4% (4 of 35)		14.7% (5 of 34)		0.73
15. Have you refrained from leisure activities today because of pain from your appliance? (Day 4)	1.4% (1 of 70)		0.0% (0 of 35)		2.9% (1 of 35)		>0.99
15. Have you refrained from leisure activities today because of pain from your appliance? (Day 7)	1.4% (1 of 69)		0.0% (0 of 34)		2.9% (1 of 35)		>0.99

¹Mann–Whitney test for visual analogue scale (VAS) variables and chi-2 test or Fischer exact test if appropriate for binary variables.

N.A., not applicable.

Pain and discomfort from mouth, teeth, and jaws (Supplemental Material, questions 4–9, 11–13)

Pain and discomfort were most extensive on the first day after inserting the appliance in both groups and dropped to day 7 (Table 3). On day 1, the QH group had more pain from the tongue (P < 0.01), and more chafing from the appliance (P < 0.01) (Figure 3). On day 4, the QH group had still more chafe from the appliance than the RME group (P < 0.01). On day 7, no significant differences were found between the groups.

Table 3.

Comparing pain and discomfort and functional jaw impairment variables between days 1 and 7 for all and for quad helix (QH) and rapid maxillary expansion—hyrax type (RME) groups (data in figures).

	All (n = 70)		QH group (n = 35)		RME group (n = 35)
Pain and discomfort from mouth, teeth, and jaws (visual analogue scale [VAS])
	n	P 1	n	P 1	n	P 1
4. Pain due to alliance	69	<0.001	35	<0.001	34	0.008
5. Pain from molars	69	<0.001	35	<0.001	34	0.18
6. Pain from incisors	68	0.31	35	0.31	33	0.52
7. Pain from jaws	68	0.097	35	0.029	33	0.91
8. Pain from palate	68	0.023	35	<0.001	33	0.83
9. Pain from tongue	67	0.31	35	0.27	32	0.95
11. Tension from jaws	66	<0.001	33	0.009	33	0.015
12. Tension from teeth	66	<0.001	33	0.006	33	0.004
13. Chafe from appliance	65	<0.001	34	<0.001	31	0.16
Functional jaw impairment (verbal rating scale [VRS])
	n	P 1	n	P 1	n	P 2
16. Leisure activities	66	0.008	32	0.020	34	0.16
17. Speech	69	<0.001	35	<0.001	34	0.012
18. Ability to take a big bite	64	<0.001	31	0.004	33	0.047
19. Ability to chew hard food	63	<0.001	32	<0.001	31	<0.001
20. Ability to chew soft food	68	<0.001	35	<0.001	33	0.048
21. School work	62	0.003	31	0.071	31	0.011
22. Ability to drink	69	<0.001	35	0.007	34	0.001
23. Ability to laugh	67	0.011	33	0.18	34	0.025
24. Ability to yawn	69	0.039	35	0.083	34	0.26
25. Ability to swallow	69	<0.001	35	<0.001	34	<0.001
How difficult to eat
26. Crispbread	61	<0.001	32	<0.001	29	<0.001
27. Meat	61	<0.001	32	<0.001	29	0.008
28. Raw carrots	58	<0.001	30	<0.001	28	0.017
29. A French bread roll	59	<0.001	27	0.002	32	0.095
30. Peanuts	45	<0.001	22	0.003	23	0.016
31. An apple	58	<0.001	29	<0.001	29	0.007
32. A soft cake	61	<0.001	29	<0.001	32	0.083

¹Wilxocon paired rank-sum test.

²Marginal homogeneity test comparing the variables on the five categorical scale (from not at all to extremely difficult).

Figure 3.

Visual analogue scale (VAS) score 0–100 at days 1, 4, and 7 after inserting either quad helix (QH) or rapid maxillary expansion—hyrax type (RME).

Analgesic consumption (Supplemental Material, question 10)

On the question if they had taken any analgesics the first day, 46 per cent answered yes in the QH group compared to 35 per cent in the RME group (P = 0.38). On day 4, 17 per cent in the QH group answered that they had taken analgesics and 14 per cent in the RME group (P = 0.74). On day 7, no patient declared the use of analgesics (Table 2).

Daily activities (Supplemental Material, questions 14 and 15)

The first-day leisure activities were affected in 11 per cent (QH group) and 15 per cent (RME group), respectively (P = 0.73). Six children in each group answered that they had stayed home from school due to the pain from the appliance the first day. On day 4, one patient had stayed home from school due to pain from the appliance (QH group) and one had avoided leisure activities (RME group). On day 7, all children had been to school. One patient in the RME group still avoided leisure activities (ice hockey) due to the appliance (Table 2).

Functional jaw impairment (Supplemental Material, questions 16–25)

On day 1, no statistical differences were shown between the groups. On day 4, speech was more affected in the RME group than the QH group (P < 0.01) (Figure 4) as well as day 7 (P < 0.01) together with difficulties in taking a big bite (P < 0.01).

Figure 4.

Functional jaw impairment at days 1, 4, and 7 after inserting either quad helix (QH) or rapid maxillary expansion—hyrax type (RME).

Functional jaw impairment—eating (Supplemental Material, questions 26–32)

On day 1, the QH group had more trouble chewing raw carrots (P < 0.01) and a French bread roll (P < 0.01). On day 4 as well as day 7, no statistically significant differences were present between the groups (Figure 5).

Figure 5.

Functional jaw impairment and eating difficulties days 1, 4, and 7.

Gender differences

In regard to gender, no significant differences were found (Table 4).

Table 4.

Comparing pain and discomfort from mouth, teeth, and jaws and daily activities between boys and girls.

	Boys (n = 44)	Girls (n = 26)	P 1
Pain and discomfort from mouth, teeth and jaws
10. Have you taken any analgesic today? (Day 1)	40.9% (18 of 44)	40.0% (10 of 25)	0.94
10. Have you taken any analgesic today? (Day 4)	13.6% (6 of 44)	19.2% (5 of 26)	0.73
10. Have you taken any analgesic today? (Day 7)	2.3% (1 of 43)	0.0% (0 of 26)	>0.99
Daily activities
14. Have you stayed home from school today due to pain from your appliance? (Day 1)	20.5% (9 of 44)	12.0% (3 of 25)	0.51
14. Have you stayed home from school today due to pain from your appliance? (Day 4)	2.3% (1 of 44)	0.0% (0 of 26)	>0.99
14. Have you stayed home from school today due to pain from your appliance? (Day 7)	0.0% (0 of 43)	0.0% (0 of 26)	N.A.
15. Have you refrained from leisure activities today because of pain from your appliance? (Day 1)	15.9% (7 of 44)	8.0% (2 of 25)	0.47
15. Have you refrained from leisure activities today because of pain from your appliance? (Day 4)	2.3% (1 of 44)	0.0% (0 of 26)	>0.99
15. Have you refrained from leisure activities today because of pain from your appliance? (Day 7)	2.3% (1 of 43)	0.0% (0 of 26)	>0.99

¹Chi-2 test or Fischer exact test if appropriate for binary variables.

N.A., not applicable.

Discussion

This RCT has given us new knowledge about the patient perspective during the first week of posterior crossbite treatment, in children in the early mixed dentition. To our knowledge, this is the first RCT comparing pain intensity and discomfort during posterior crossbite treatment with an RME on deciduous molars versus QH appliance. The most important finding was that children in the QH group perceived more pain from the tongue and chafe on the first day than the RME group. The RME group experiences surprisingly low levels of pain throughout the whole week despite its orthopaedic effects (23). When planning orthodontic treatment, we should not only think about the objective outcome of treatment but also take into account the patient perception of a certain treatment, especially when treating children.

In both groups, the speech was considered at least slightly impaired the first day, in about 90 per cent of the patients. On days 4 and 7, however, the RME group still had difficulties with speech, significantly more than the QH group. One explanation could be due to the appliance design but also due to the diastema that the RME generates between the central incisors after a couple of days. Diastema has been correlated to have a negative effect on speech (24).

We could not find any difference in reported analgesic consumption during the first week. This finding is consistent with a recently published non-randomized trial that compared RME with slow maxillary expansion (25). Their study population was children in their permanent or late mixed dentition, about 3 years older than our patients; mean ages for the QH and RME were 12.9 (SD ±1.5) and 12.7 (SD ±1.4) years, respectively. The study had, unlike our population, a majority of girls in both groups (QH 74 per cent and RME 82 per cent). The researchers found more pain and discomfort with the hyrax RME at the commencement of the treatment, even though they concluded that the differences were minor. That they performed their study on older patients could be a reason why our results differ. Our results give us a reason to believe that RME treatment should not be delayed until the permanent dentition, and children should be treated in the early mixed dentition if possible. We can also speculate that the RME we used with anchorage on deciduous teeth generates less pain than the QH anchored on the permanent molars because nerves in deciduous teeth are less dense in distribution and fewer in number than those in permanent molars, and thereby experienced less sensitive (26).

In this present study, we used questionnaire with VAS and VRS to determine pain and discomfort during the first week of treatment. VAS is a long-recognized way to let patients grade their perception of pain and discomfort (27). The median level of pain on VAS was in the low to middle range on the first day and even lower on days 4 and 7. A study with children undergoing class II treatment with cervical headgear, the same age as our study population, experienced the same levels of pain on VAS as our QH group did on the first day. They also reported that elastic separators were slightly more painful than headgear, the first day, even though the difference was not statistically significant (28). Although the median values of pain intensity and discomfort during the first week of treatment were low in both groups, some patients described the pain and discomfort as the worst imaginable. Perception of pain intensity is subjective and influenced by many factors, such as anxiety levels and motivational attitude (29).

Strength and limitation

The strengths of this study were that the patients were homogenous in age and gender distribution and therefore representative of the most common age for RME and QH treatments, and that questionnaires with documented good reliability and validity were used. This study also has good generalizability due to its bi-centre nature. In addition, selection bias was avoided because consecutive patients were invited and randomized into two groups in which the treatments were standardized. This study has some limitations, however. Double blinding was not possible due to the clinical limitations. Children were allowed help from their parents to read the questions, although the children were requested to answer independently, the influence of the parents cannot be disregarded.

Generalizability

The result of this RCT can be generalized only in a similar population aged 9–10 years and in the case that the exclusion criteria are met.

Harm

No harm or adverse effects were recorded in the present study.

Clinical implications

From the point of view of pain and discomfort, it appears that the both appliances are tolerated quite well by our patients. However, the information about perceived discomfort from the tongue and chafe with the QH appliance, and slight speech impairment during the first week with both appliances, should be mentioned to our patients following initiation of treatment.

Conclusion

• - Patients with QH experienced more chafe and pain from tongue on the first days than the RME group.

• - Speech was more affected in patients with RME on days 4 and 7.

• - The levels of pain are to be considered as low to moderate in both groups the first week.

Funding

This study was supported by the Regional Research Council. The authors’ work was independent of the funders.

Conflict of interest

The authors declare no conflict of interest.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article or its supplementary materials.