In this study, they examined the effect of sequencing slow rapid maxillary expansion (SRME) and adenotonsillectomy (TA) in paediatric obstructive sleep apnoea. A team from Australia and Hungary conducted the study. The Journal of Clinical Medicine published the paper.

Maxillary Arch Expansion and Adenotonsillectomy in Prepubertal Children Diagnosed with Paediatric Obstructive Sleep Apnoea: An Interventional Study

Derek Mahony Niroj Bhattarai and Peter Petocz

Journal of Clinical Medicine. On line https://doi.org/10.3390/jcm15082981

The paper is open access so anyone can read it.  The Journal of Clinical Medicine is listed as a predatory journal on the Predatory Journals website. 

What did they ask?

They did this study to ask the following question. 

” What are the combined effects of adenotonsillectomy and maxillary arch expansion in pre-pubertal children with OSA, and is there an effect of the sequence of treatment? 

What did they do? 

This was a retrospective cohort study using a subsample of patients from a larger cohort that I have previously posted about. 

They selected 80 sets of patient records from an original sample of 3,671 children aged 7-9 years who underwent polysomnography at their first orthodontic consultation, representing 2% of the original sample.

The main inclusion criteria were the availability of complete PSG records at three times:

• Baseline (pre-treatment)
• After the first intervention
• After both interventions

They had to complete slow rapid maxillary expansion and adenotonsillectomy, regardless of the sequence. 

They had no history of prior orthodontic treatment or diagnosed sleep disordered breathing at baseline. 

Exclusion criteria were incomplete records and the absence of level one hospital-based PSGs. 

They then divided this sub-sample into two groups. This was “based on a treatment sequence that was determined by the patient and parental preference and logistical factors rather than randomisation”. As a result, they suggested this reflected the “real world” of decision making.

Group one was designated TA first, comprising patients who underwent tonsillectomy as the initial intervention, followed by SRME. 

The second group had SRME as the initial intervention. This was due to delays in accessing publicly funded ENT appointments or waiting periods for private insurance cover. 

They collected demographic details, cephalometric classifications, and BEARS questionnaire scores greater than 5, indicating an SDB risk. 

Accredited sleep laboraties did the polysomnography measurements.

The primary outcome for this study was the respiratory disturbance index (RDI). This is the average number of apnoeas, hypopnoeas, and respiratory effort-related arousals per hour of sleep. 

Statistical analysis was based on a repeated-measures analysis of variance over time. The authors did explain the method clearly, and I couldn’t really work out the statistical plan.

What did they find? 

The mean age of the participants was 8.3 years, and 43% were male. At the start of treatment, the mean RDI was 18.99, indicating moderate severity.

At the start of treatment, there were no differences between the groups in most measured variables; however, there was a marked difference in BMI. The TA first group had 87% of the sample classified as overweight or obese, whereas the SRME group had 45% of participants in this classification. This is important because it represents a marked imbalance between the groups. 

I have extracted some of the data into this table. This illustrates the RDI for the combined BMI groups. I also calculated the 95% confidence intervals for this data.

When you look at the 95% confidence intervals, you can see that they overlap for the interventions’ effects. This means that the effects may not be statistically significant. Furthermore, they do not overlap at the start of treatment.

I looked closely at their statistical analysis, and the tables outlining it were rather brief, which made it difficult to interpret the findings.

They also presented a table showing RDI reduction. However, I felt we could be more focused in this blog post by simply comparing the values between the two groups.

The conclusions were 

“Both TA and SRMA significantly improved the RDI in pre-pubertal children with OSA and maxillary constriction. The greatest benefit was seen when these were combined. The SRMA first, followed by TA, was somewhat more effective by about 1.5 events per hour overall.” 

What did I think?

This study used the Respiratory Distress Index (RDI). I was unfamiliar with the RDI and sought further information on this measure. The RDI is similar to the Apnoea-Hypoxia Index (AHI) but includes Respiratory Effort-Related Arousals (RERAs). This makes it useful for assessing milder forms of sleep-disordered breathing. It is highly sensitive to treatment and, importantly, more sensitive than the AHI.

The RDI values can be classified as

• Normal: RDI < 1 event per hour.
• Mild OSA: RDI between 1 and 5 events per hour.
• Moderate OSA: RDI between 5 and 10 events per hour.
• Severe OSA: RDI > 10 events per hour. 

Problems with the study

Importantly, we may need to consider the accuracy of diagnosing sleep disorders from a single night’s readings. A systematic review has examined this and concluded that this variation may lead to misdiagnosis in single-night studies. We need to consider this when we interpret the results of this study, which used a single-night recording.

Bias

There is also considerable risk of further selection bias in the study, given that the authors analysed only 80 sets of records from a total sample of 3971 (2%). This risk is further compounded by the inclusion criteria, which require completion of treatment and full records. As a result, the study is at risk of being biased towards favourable outcomes.

When I looked at the data they presented, it was clear that the groups were unbalanced for BMI at the start of treatment. It appears that the clinicians had a preference for TA in obese children, which could lead to selection bias in the study. Furthermore, the treatment allocation order was determined by delays in access to ENT care. It appears that if a patient’s ENT treatment was delayed, they received SRME. This design is subject to systematic confounding, and we must account for differences between the groups. For example, they may be children from low socioeconomic groups.

Control group and effect size

In addition, there was no untreated control group. This is crucial for this form of study because the CHAT study estimated that 50% of 5- to 9-year-old children with OSA who were randomised to watchful waiting achieved OSA remission, as defined by PSG findings, after 7 months.

When we look at a paper, it is important to consider the differences in effect sizes. Even a cursory examination shows that there is limited difference between the two intervention sequences. I also could not really understand the statistics they used because of a lack of data, particularly the p-values. They also presented the percentage change in RDI as an outcome. It is more important to look at the group differences.

It is also relevant to point out that they did the in 9 private orthodontic practices with an interest in airway treatment. As a result, the findings may not be relevant to the general population.

We must also consider whether Dr Mahoney has an undeclared conflict of interest, given that he is the CEO of a company that operates several orthodontic practices specialising in “airway-focused” care.

Final comments

I may be criticised for being so blunt about a study. However, I felt it was necessary to point out the deficiencies in this paper.  This study provides very low-level evidence. However, its data may be used for planning randomised trials in this important area.

Now that you have read this blog post.

Last year, I requested donations to support my blog, and thankfully, I received an overwhelming response. With your help, I was able to raise sufficient funds to keep my blog going for another year. 

Now, I’m seeking your support again to help me cover the blog’s running expenses for the upcoming year. The funds will cover web hosting, software upgrades, email lists and general running costs. 

I believe that if every reader contributes a small amount, I can cover the yearly running costs. Your help will be much appreciated.

To make a donation, just use the form below. You can use the set-amount buttons or the free-field button to enter other amounts.

Then the easiest way to pay is to tap the Apple Pay button. If you want to use another payment method, click the “next” button and enter your details. This will take you to credit cards, PayPal, and other payment methods.

       

Comments

• Prof, Thanks for your erudite analysis which is so valuable to ... by Geoffrey Wexler
• There is a small randomized clinical trial conducted to address ... by Steve Marshall
• I was surprised to read that you were “unfamiliar with the ... by Prof Dave Singh
• In reply to Trevor Baret. I wonder if I did not make myself ... by Kevin O'Brien
• i have never before seen a study being accused of bias because ... by Trevor Baret

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We are all familiar with the use of clear aligners in adults; however, new research is now being published on their effectiveness in adolescent patients. 

The authors of this study pointed out that little is known about the effectiveness of treating Class II malocclusion with clear aligners. This study should add to our knowledge. 

A team from Adelaide, Australia, did this study. The American Journal of Orthodontics published the paper.  It is open access.

Efficacy of Class II correction with clear aligner therapy and intermaxillary elastics in adolescent patients: A retrospective study

Maurice Meade, Bariah Rans and Tony Weir

AJO-DDO advanced access:  https://doi.org/10.1016/j.ajodo.2026.02.014

What did they ask? 

They did this study to 

“Assess the changes in overjet and the intermaxillary sagittal first permanent molar relationship in adolescent patients after treatment with an initial set of Invisalign aligners and Class II elastics.” 

What did they do? 

They obtained the sample for this study from the Australian Aligner Research Database. This database contains data on approximately 17,500 patients treated by 18 experienced orthodontists. 

I have previously done blog posts about papers from this study team that use this database. It certainly seems to be a valuable source of information. 

The inclusion criteria for patients to take part in this study were that they were under 18 years old with a Class II malocclusion, defined by the molar relationship. The orthodontists treated them with Invisalign only. They had to have full records.  

The source of information was the STL models. They obtained the files for (1) pre-treatment, (2) planned movements, and (3) achieved outcomes after wear of the initial aligners.

The primary outcome measures were overjet and intermaxillary sagittal relationship. 

They conducted a sample size calculation, which indicated they needed 64 patients. However, they decided to base their sample size on eligibility for inclusion in this study. As a result, they included information on 199 participants. 

They performed standard univariate analyses to examine their data. 

What did they find? 

They included 199 patients in their final sample. 65.8% of these were female, and the mean age of the sample was 13.66 years. 

I have extracted the mean and 95% CI data for overjet and first molar (FPM) variables (mm) into this table.

At the end of treatment, 45.2% had an overjet greater than 4.1 mm. Importantly, only 33.6% of the planned overjet reduction was achieved. Interestingly, 31% of patients showed an increase in overjet, despite a planned reduction.

The greater the pre-treatment overjet, the larger the discrepancy between the planned and achieved changes. When assessing sagittal change, the overall accuracy of the planned sagittal change was 45.9%.  

The final conclusions were 

“Almost half of the participants had an overjet greater than 4.1 mm at the end of the initial series of aligners. Importantly, 31% showed an increase in overjet despite a reduction in overjet being planned.”

What did I think? 

Regular readers of this blog will know that over several years, we have made a plea for increased research into the effectiveness of clear aligners. Ideally, this should be done with prospective cohort studies or randomised trials. Unfortunately, investigations of this nature are lacking. As a result, we have to rely on retrospective studies for information. 

This team has conducted extensive research and published numerous papers using the Australian aligner database. This is a large database and appears to be a good source of information, albeit retrospective. When we consider the nature of this research, we must assume there is some selection bias in the sample; however, we do not know its direction. This is, to a degree, offset by the fact that the database is large and that all orthodontists are obliged to include their patients treated with clear aligners in it. 

As a result, I think we can conclude that this is the best information we have on the use of clear aligners. 

The results of this study are similar to those reported in previous papers by this group. It appears that there is a disparity between planned and achieved tooth movements with clear aligners. In this respect, the results suggest that aligners used in this way are not an effective method of class 2 correction. It certainly appears that functional appliances achieve better results. However, we also need to remember that there is a relatively high discontinuation rate with removable functional appliances. Unfortunately, there does not seem to be information on the discontinuation rate in this sample of patients. Therefore, this information is lacking. 

Final thoughts. 

I used and studied removable functional appliances for many years during my clinical practice. The results of this study would not persuade me to switch this group of patients to clear aligner treatment. However, some people may be excellent operators with better results than those reported in this paper. It would be good to hear their comments on this paper. 

Now that you have read this blog post.

Last year, I requested donations to support my blog, and thankfully, I received an overwhelming response. With your help, I was able to raise sufficient funds to keep my blog going for another year. 

Now, I’m seeking your support again to help me cover the blog’s running expenses for the upcoming year. The funds will cover web hosting, software upgrades, email lists and general running costs. 

I believe that if every reader contributes a small amount, I can cover the yearly running costs. Your help will be much appreciated.

To make a donation, just use the form below. You can use the set-amount buttons or the free-field button to enter other amounts.

Then the easiest way to pay is to tap the Apple Pay button. If you want to use another payment method, click the “next” button and enter your details. This will take you to credit cards, PayPal, and other payment methods.

       

Comments

• Interesting study, unsurprising findings, but a waste of time ... by Vishnu Raj
• In reply to Kevin O'Brien. Thank you, Kevin. I agree that ... by Tommaso Castroflorio
• In reply to Kevin O'Brien. Thanks for your comment. I am not ... by Vicki Vlaskalic
• Kevin, Thanks for posting this study. As you and others here ... by Art Sonneborn
• In reply to vicki vlaskalic. Thanks for declaring your ... by Kevin O'Brien
• Plus 5 more...

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This new pilot study looked at the effects of dental arch constriction on SDB. I found the results interesting. They provide an argument against some of the nonsense circulating about the effects of orthodontics.

A team from Canada, did this study. The Angle Orthodontist published the paper. 

Effects of simulated arch constriction on upper airway function during sleep

Da In Kim; Manuel O. Lagravère; Fernanda Almeida; Benjamin T. Pliska

Angle Orthodontist: On line. DOI: 10.2319/051925-396.1

What did they ask? 

The aim of this study was 

“To characterise the presence of functional changes of the airway with level three polysomnography while using an appliance simulating airway constriction” 

What did they do? 

They conducted a single-blind, prospective, randomised crossover study in healthy adults. 

The PIC0 was 

Participants 

Healthy adults were recruited from the student and staff population of the Faculty of Dentistry. 

They had standardised demographic and anthropometric data collected and orthodontic records. This included a lateral cephalogram and an intraoral scan of the dentition. 

Intervention

This was a vacuum-formed retainer designed to constrict the arches. Constriction was simulated by adding a 5 mm thickness to the lingual and palatal aspects of all the teeth in both upper and lower arches. This resulted in a 1cm constriction overall.

Control 

A vacuum-formed retainer. 

Outcomes. 

The primary outcomes were Respiratory Events Index (ROI) This was derived from data obtained from a portable sleep monitor at home. 

Other outcomes were oxygen desaturation index (ODI), SpO2 measured with a pulse oximeter. The Epworth Sleepiness Scale and morphological data. 

Each participant underwent three sleep studies. The initial study was conducted at baseline, before any appliances were fitted. Patients were then randomly assigned by computer-generated randomisation to an intervention sequence arm, and they wore either the control appliance or the constricting appliance for six days. After this period, a second home sleep study was conducted. 

The participants then crossed over and used the other appliance for another six days. This was followed by a third sleep study. 

They analysed their data with a relevant univariate statistical test. 

They conducted a sample size calculation for a pilot study, which suggested they needed 12 participants per group. As a result, they attempted to recruit 24 participants, with an additional 11 to account for potential dropouts. 

What did they find? 

They recruited 35 healthy participants with an average age of 28.5 years for the study. By the end of the study, 34 participants had completed all required data collection. When analysing their data, there were no statistically significant differences in REI at any stage of the study. 

Similarly, when they examined ODI, they did not find any statistically or clinically significant differences. There did not find any differences in the Epworth sleepiness scores. 

The overall conclusion was 

“Simulated severe constriction of the dental arches does not affect respiratory function during sleep as measured by at-home polysomnography.” 

What did I think? 

This was a good, ambitious study that employed quite novel techniques. They used an interesting and relevant method to simulate dental arch constriction. We might think that this does not fully represent the gradual arch constriction that can occur with “retractive orthodontics”. Nevertheless, I believe this was a reasonable approach.

I have considered whether the rather sudden constriction might have influenced the results. I cannot help feeling that rapid constriction would have a greater impact than a slow constriction resulting from any orthodontic treatment. This is because the airway is given sufficient time to adapt to the constriction. However, I am not an expert on this matter, and my thoughts are purely conjecture.

We also need to acknowledge that this study is a pilot with a relatively small sample size; however, given the small effect sizes detected, we would argue that they are unlikely to change substantially with a larger sample. Still, I would prefer to see a larger study before drawing any firm conclusions.

The authors also mention that they relied on participants’ cooperation and did not measure the duration of appliance wear. This factor could, of course, influence the results. 

Final thoughts. 

We need to consider whether we can generalise these findings to real-world clinical care. I believe they offer some evidence that the constriction of arches does not impact breathing.

Nonetheless, we should interpret the results of this study with caution, but they provide useful preliminary data to guide further research and enhance our understanding of this important issue. 

Now that you have read this blog post.

Last year, I requested donations to support my blog, and thankfully, I received an overwhelming response. With your help, I was able to raise sufficient funds to keep my blog going for another year. 

Now, I’m seeking your support again to help me cover the blog’s running expenses for the upcoming year. The funds will cover web hosting, software upgrades, email lists and general running costs. 

I believe that if every reader contributes a small amount, I can cover the yearly running costs. Your help will be much appreciated.

To make a donation, just use the form below. You can use the set-amount buttons or the free-field button to enter other amounts.

Then the easiest way to pay is to tap the Apple Pay button. If you want to use another payment method, click the “next” button and enter your details. This will take you to credit cards, PayPal, and other payment methods.

       

Comments

• It is 3PM on the west coast of the US and so far ... by John L. McDonald

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A team from Wuhan, China did this review. Sleep and Breathing published their paper.

The effect of rapid maxillary expansion on children with obstructive sleep apnea: a systematic review and meta-analysis

Yu et al. 

Sleep and Breathing, Advance access. DOI: https://doi.org/10.1007/s11325-026-03606-1

What did they ask? 

“The primary object of this systematic review was to evaluate the efficacy of RME in treating pediatric OSA.”

What did they do? 

They did a systematic review using standardised methodology.  

The PICO was 

Population. 

Children with maxillary transverse deficiency who are diagnosed with OSA via overnight PSG 

Intervention. 

Treatment with rapid maxillary expansion appliances. 

Comparison 

Baseline pre-RME treatment or Watchful waiting. 

Outcome. 

Respiratory Outcomes and Radiological Outcomes 

Study Design 

They included cohort studies, cross sectional, retrospective studies, case controlled studies with a comparison or control group, and randomised controlled trials.

They carried out an electronic search, followed by identification of studies, filtering of studies, data extraction, risk of bias assessment and outcome assessment.

The primary outcome was the apnea-hypopnea index (AHI). Secondary outcomes were, sleep efficiency, peripheral capillary oxygen saturation and other patient-related outcomes

They conducted a meta-analysis using a random-effects model. 

They assessed the risk of bias in all studies using the Risk of Bias in Non-Randomised Studies (ROBINS-I) tool. This was not relevant for the randomised trials they found. Finally, they appraised the quality of evidence with the GRADE tool. 

What did they find? 

After filtering the studies, they identified 14 suitable for data analysis. Seven of these were before-and-after studies. Five were non-randomised controlled trials, and three were randomised controlled trials. 

When they performed their risk of bias analysis and found that ten studies had a serious risk of bias. They assessed four studies as having a moderate risk of bias. 

Ten studies examined changes in AHI within 6 months after completing RME (mean difference: -4.04, 95% CI: -6.39 to -1.7, p = 0.0007). Heterogeneity was 93%. 

Seven studies examined changes within 12 months of the intervention. These showed that the mean difference was -6.15 (95% CI, -11.66 to -0.64), p = 0.03. Heterogeneity was 97%. 

They reported significant improvements in most of their other outcome measures. 

The discussion was insightful because they noted a significant reduction in the apnea-hypopnea index at both 6- and 12-month follow-up. However, they highlighted that the RME did not consistently bring AHI values below 1 to normal levels. 

They also highlighted that heterogeneity was very high. This diminishes confidence in their findings. Significantly, the quality of the evidence, as assessed by GRADE, was rated low or very low. They further noted that the number of high-quality RCTs was very limited, with many studies having small sample sizes and methodological flaws. Consequently, we need to be cautious when interpreting the results. 

Their final conclusion was: 

“These findings indicate that RME can effectively enhance the transverse width of the maxilla and improve polysomnographic parameters in pediatric patients with OSA.” 

I took this from their abstract, as it is likely to be more widely read than the paper itself. 

What did I think? 

A relatively well-known team conducted this review. They followed standard systematic review methodology. When I read the abstract, I thought that this review could significantly contribute to our knowledge because of its very positive conclusion. However, upon reading the paper, I concluded that this was an excellent example of an abstract that does not necessarily reflect the quality of the research and content of the paper. We must remember that the overall quality of the evidence was rated low or very low.

Systematic reviews can be quite challenging to interpret due to the vast amount of information they contain. However, I have several main concerns with this review. 

Firstly, they merely reported the results before and after treatment for the studies they included. They did not compare any changes to an untreated control group. As a result, it is impossible to conclude that the RME influenced AHI. This is because the results do not account for the possible effects of growth. For example, in the classic CHAT study, they found that “46% of children in a watchful wait group had some resolution of polysomnographic abnormalities.” I am not endorsing watchful waiting based on this study; I am simply highlighting that AHI can reduce spontaneously.

Secondly, they identified several included studies as being at high risk of bias. As a result, they stated that the strength of evidence was very low. Furthermore, most of these studies were cohort and retrospective studies. Again, this further diminishes the strength of evidence.  

Finally, the heterogeneity in the meta-analysis was very high. They removed outlier studies to reduce heterogeneity; however, they did not publish the meta-analysis results after this removal. I have contacted the authors to clarify the situation, but I have not received a reply. 

Final comments. 

Over the past six months, I have been accused of being overly critical of several studies concerning orthodontics and breathing disorders. I would like to emphasise that I genuinely want to see strong evidence demonstrating that we can improve the health of this group of children with a disorder that may lead to long-term problems.

However, I have critically appraised these studies and found that many lack robust methodology and do not meaningfully address the questions we have about orthodontics and breathing disorders. I am sorry to say that this is yet another study that fails to illuminate this complex issue. 

       

Comments

• Dear Professor O’Brien, I agree with your excellent ... by James patrick murphy dmd
• In reply to Prof Dave Singh. Thanks for your comments and I ... by Kevin O'Brien
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The study team tested a modified open exposure technique that they have used for over 40 years (GOPEX). This involved, instead of surgical packing, applying glass ionomer cement to the canine. The glass ionomer remains on the tooth until it has spontaneously erupted above the gingiva. This certainly seems to be a better method than the one I used when I practised, where we placed a periodontal dressing over the open exposure and removed it after 10 days. Unfortunately, it tended to detach, and the tooth happily covered up again.

The well-known trial team from Gothenburg, Sweden, conducted this study. The European Journal of Orthodontics published the paper. Since it is open access, anyone can read it. 

Glass ionomer open exposure and closed exposure of palatally displaced canines: a randomised controlled trial comparing postoperative pain perception and complications

Anna Dahlén et al

EJO Advance access: https://doi.org/10.1093/ejo/cjag011

What did they ask? 

They did this study too.

“Compare glass ionomer open exposure (GOPEX) with closed exposure (CE) in terms of patient-reported outcomes, surgical duration, and complications.” 

What did they do? 

They did a single-centre randomised controlled trial with a one-to-one allocation of two parallel groups. The PICO was:

Participants 

Children and adolescents under 18 years old with a palatally displaced canine were referred for treatment between March 2017 and April 2024. The main inclusion criteria were that they had a unilateral PDC and were planned for surgical exposure and orthodontic treatment. Importantly, the canine had to be positioned within sectors 2-5 on the panoramic radiograph. 

Intervention one. 

GOPEX. This was an open exposure in which glass ionomer cement was applied to the cusp tip of the exposed PDC. 

Intervention two. 

The paediatric dentist exposed the tooth, and then bonded an eyelet and chain with light-cured composite. They then sutured the flap back to its original position. 

Outcomes 

The study reported on several outcomes. The primary outcome was the amount of pain recorded by the patients. They also included information on the children’s fear of their procedure, as well as the duration of surgery and any complications. 

They used a pre-prepared randomisation scheme. Allocation concealment was stored securely at the clinic and was not accessible to the recruiting orthodontists. The allocation was carried out after obtaining the patients’ written consent. 

One of three experienced paediatric dentists performed the surgical procedures. 

They did a clear sample size calculation. Based on the amount of pain the patients could report. This revealed that 40 patients per group were required. They increased the target sample to 92 participants to compensate for dropouts. 

They conducted relevant multivariate and univariate statistical tests, and clearly outlined them in their paper. 

What did they find? 

They randomised 92 patients to the interventions: 43 to the GOPEX group and 40 to the closed exposure group. All of these patients completed the study.

During the first fourteen post-operative days, there were no significant differences between the groups in pain levels; however, after seven days of cooperation, pain scores were substantially higher in the GOPEX group than in the CE group. There were no differences in the percentage of pain-free patients, analgesic use, or chewing difficulty. 

Their overall conclusions were: 

“The GOPEX group had more pain in the first post-operative week, but no difference was seen in pain scores or any other outcome measures over the whole 14-day post-operative period.” 

What did I think? 

This was a very well-executed and well-presented trial and publication. They followed the CONSORT guidelines in their write-up; all aspects of a good trial were achieved. This is a high-quality research paper. 

When I reviewed their results, I found them to be clinically useful. Importantly, they found no difference between the two interventions in any of the outcomes they assessed. This provides us with valuable information we can share with our patients when they choose their preferred treatment.

However, while this information is useful, I could not find any details in this paper about the relative success rates of the two interventions. I contacted the authors to ask when this information will be available. They told me they are writing a paper on this and hope to publish it in early 2027. Once they have published this research, we will have the information needed to make clinical decisions with our patients. 

       

Comments

• Dr.Michael Weber April. 1. 2026 In my practice I prefered the ... by Dr.Michael Weber
• Thank you for sharing this nice comparison. I have a question ... by Nagwan Elfadil
• An interesting study. I found that often, in the closed ... by Danny Radnzic
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A team from Mansoura, Egypt conducted this research. The angle orthodontist published the paper. 

Dento-facial changes and oral health-related quality of life assessment in management of anterior crossbite in mixed dentition: a randomized clinical trial.

Asmaa S. Salem et al

Angle Orthodontist On line advance access. DOI: 10.2319/020325-109.1

What did they ask?

The authors did this study to

“Evaluate the dental-facial changes and the improvement in oral health-related quality of life between clear aligners and inclined plane appliances for managing anterior functional crossbite in the mixed dentition.” 

What did they do? 

They conducted a single-centre, randomised clinical trial with a parallel design, allocating participants in a 1:1 ratio. The PICO was: 

Participants 

24 children aged 8 to 12 years who had an anterior functional crossbite involving more than two teeth 

Intervention one. 

In-house clear aligners. They asked the patients to wear their aligners for 22 hours a day and change the aligner every 10 days. 

Intervention 2. 

A removable inclined plane which fitted the lower arch. This was made of transparent sulfur-cured acrylic resin, which was applied to a PETG sheet. The operator saw the patients every two weeks, and the operator relieved the inclined plane. After the completed treatment, they asked the patients to wear their appliance for a further four weeks. 

Outcomes 

The primary outcomes were cephalometric measurements; however, they based their standard sample size calculation on the upper incisor to SN angle, and I’ve assumed that this is the primary outcome. Secondary outcomes were oral health-related quality of life, and they measured this using the CPQ 8-10 questionnaire. 

The team performed a clear sample size calculation that suggested they needed 12 patients per group. 

The same postgraduate student treated all the patients at a single centre.

They used a pre-prepared randomisation sequence, and the allocation was performed by drawing a card from a box containing 24 cards, with 12 cards assigned to each group. It was not possible to treat the patients blindly; however, all data was analysed blind. 

They analysed the data using univariate statistics to evaluate any differences between the groups. 

What did they find? 

24 of the patients completed the trial. I could not find any information about whether they corrected all the crossbites, but I assume that this was the case. 

At the start of treatment, there were no differences between the two groups. 

They then supplied a large amount of cephalometric data with multiple comparisons. As you know, I find this kind of data presentation rather confusing and unclear. This is especially due to the risk of false positives when measuring many related variables and performing simple statistical tests. 

As a result, I have just concentrated on the straightforward outcomes of upper incisor and lower incisor angulation.

When they looked at U1-SN. In the clear aligner group, after treatment, the upper incisor position was 114.44mm (6.03).  Whereas for the inclined plane appliance, this was 108.1 mm (4.31). The mean change in this measurement was 11.65mm (3.95) for the clear aligner and 6.73mm (2.94) for the inclined plane group.  This difference was statistically significant.

When they evaluated the L1-NB (mm). For the clear aligner group, the mean was 4.01mm (1.73), and for the inclined plane group, it was 3.93mm (2.34). When they evaluated the change in this measurement, this was 0.77mm (1.42) for the clear aligner and -2.03mm (2.21) for the inclined plane group. This was statistically significant.

Finally, there were no differences in the oral health-related quality of life measurement between the groups; however, both groups showed an increase in this measurement, indicating an improvement in oral health-related quality of life for all participants.

The final conclusions were;

“The clear aligner group experienced more proclination of the upper incisors, whereas the inclined plane group showed that upper incisor proclination and lower incisor retrusion resulted in the correction of the anterior crossbite”.

What did I think?

Firstly, I thought it was positive to see more studies exploring the effectiveness of clear aligners. Importantly, this study demonstrated that clear aligners are an effective treatment for anterior cross-bite with a functional shift. However, it was also notable that there were no significant differences in the final treatment outcomes between the clear aligners and the simpler inclined plane appliance. This finding is important because, as the authors suggested, the inclined plane appliance offers a cheaper alternative to using clear aligners. 

When I examined the design of the two interventions before reading this paper, I expected to see different cooperation rates, as the inclined plane seems to be a much more challenging device for participants to tolerate. It was interesting that this was not the case, as there were no significant differences in cooperation rates between participants in either group.

In summary, this was another well-conducted small study on the effectiveness of clear aligners. This leads us to the conclusion that this study provides important information that may guide our patients’ decisions when they are giving consent for treatment.

       

Comments

• Yes, clear aligners can effectively correct anterior crossbites ... by Aligner House
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This post is rather long, but I want to cover a lot of information. I will not be posting much about this subject in the next few months, unless a useful research paper is published.

Introduction

First, I would like to examine the definition of a white paper. This varies between countries. The definition for the USA is:

“An authoritative, in-depth report that analyses a specific health issue to educate stakeholders, propose solutions, or influence decision making. They are positioned between peer-reviewed research and marketing.”

Importantly, it is not a high-level research paper or systematic review. It is worth noting that the authors do not adhere to systematic review methodology.

Therefore, we should remember that a white paper presents a series of conclusions based on our best available research. It is important to recognise that these are recommendations, not mandatory requirements, and are therefore not compulsory. Nonetheless, this paper offers guidance for the future, as it contains solid clinical advice. 

Is this important?

I also wonder how significant an issue sleep-disordered breathing and orthodontics are worldwide. As with many aspects of orthodontics, the push for “new” treatments and changes seems to originate from the USA. This is probably due to the greater number of orthodontists in the USA compared to other parts of the world.

I am also aware that some of the most vocal social media outputs and groups are USA-based. Subjectively, when I have seen comments from other countries, they tend to be more conservative, traditional, and possibly more grounded in science.

Therefore, we must keep in mind that the content and focus of this white paper are likely more relevant to the United States than to other parts of the world. Certainly, when I consider the UK, there doesn’t seem to be a strong drive to implement airway-focused orthodontics, apart from a few of the “usual suspects” who adhere to the mantra of orthotropics and other fringe treatments.

As a result, we need to be careful not to become dominated by USA-based orthodontics, as there is a risk of wasting a considerable amount of time.

In this context, I have decided to review this white paper. 

The panel

It is evident from the information on the panel members that this is a carefully assembled group of experts. The panel comprises a mix of practitioners, representatives of the AAO, and research academics.

The Introduction

This was well written and clear. I was particularly impressed by the way they described the somewhat confusing situation of sleep-disordered breathing (SDB), its medical and surgical treatments, and the role of orthodontics. Importantly, they pointed out that sleep-disordered breathing is a continuum, ranging from snoring to obstructive sleep apnoea (OSA).

They also emphasised that SDB is a medical condition. Consequently, only a physician can diagnose SDB in the USA and Canada (and in the UK). This means that the diagnosis would fall outside an orthodontist’s scope of practice.

Nevertheless, orthodontics does have a role in the interdisciplinary management of SDB, particularly in children. This includes conventional orthodontic treatment, screening, referral, and some interventions.

When we consider the nature of the disease, SDB is a heterogeneous condition with variable treatment responses. It is influenced by both anatomical and non-anatomical factors. The former include soft-tissue volumes, such as enlarged adenoids or palatal tonsils, fat infiltration, and potentially reduced skeletal volume. Non-anatomical factors include the neuromuscular function of the pharyngeal musculature.

Importantly, prepubertal OSA tends to resolve naturally during the transition to adolescence. This, of course, coincides with orthodontic treatment. As a result, we believe that orthodontics can help treat SDB.

Now I would like to review what I consider the most important recommendations and the underpinning research.

Craniofacial form and OSA.

Traditionally, we think that OSA is associated with certain craniofacial features, such as increased facial height, mandibular retrusion and craniofacial disharmony.  It is often stated that these are aetiologic factors in OSA. As a result, some suggest that correcting these skeletal problems will cure SDB.

The panel pointed out that there is limited evidence for these concepts.  The source of their evidence was 2 systematic reviews. 

One of these studies was published in the AJO-DDO in 2013. This review incorporated data from nine trials, of which eight were prospective case-control studies. The authors highlighted a potential association between craniofacial disharmony and paediatric sleep-disordered breathing. However, any differences were unlikely to be clinically significant. 

The Journal of Clinical Sleep Medicine published the other study in 2022. The authors identified nine studies. Four were cross-sectional, four were case-control studies, and one was a prospective cohort study. Both reviews were conducted with sound methodology. Nevertheless, they were limited by a small number of studies and high levels of uncertainty in the data. As a result, the AAO panel concluded that there was limited evidence for a connection between OSA and certain craniofacial features.

Their overall conclusion was that, due to the very low to moderate certainty level, ‘an association or lack thereof, between craniofacial morphology and paediatric OSA, cannot be supported by the data.’

Use of imaging in SDB

The panel concluded that imaging of the upper airway using CBCT or lateral cephalograms has no diagnostic value for SDB risk assessment or diagnosis. Furthermore, using changes in upper airway dimensions to suggest the efficacy of orthodontic treatment is scientifically flawed.

They based these conclusions on an International Consensus Statement on Obstructive Sleep Apnoea, published in July 2023. This was a large consensus meeting that evaluated OSA in great detail. The paper included 176 pages with just over 2000 references. I did not have time to read it in detail. However, in addition to the section on imaging, there was a section on the treatment of paediatric OSA. The authors pointed out that the first-line treatment was adenotonsillectomy. Importantly, I did not find a mention of orthodontic treatment.

I thought this paper was very important because it addressed one criticism that the AAO viewpoint was not based on medical research. I wonder if our collection of airway-focused orthodontics has read this paper?

Palatal expansion

The panel concluded that orthodontists should only provide palatal expansion for sleep disordered breathing management in patients with a clear orthodontic indication alongside a confirmed SDB diagnosis. I found this somewhat vague, and I interpreted it to mean that expansion should only be performed if a crossbite with a potential skeletal discrepancy is present.

They based this recommendation on two publications, one of which was a 2023 meta-analysis that found that RPE alone did not significantly reduce the apnea-hypopnea index. This included data from five randomised controlled trials and four non-randomised controlled trials, which together provided information on 595 patients. Most of the trials were rated as high risk of bias due to issues with blinding participants. The meta-analysis revealed limited evidence of a positive effect of rapid maxillary expansion.

The other study was a crossover randomised controlled trial examining the use of adenotonsillectomy and palatal expansion on AHI. I have written a blog post about this trial. I found it well-conducted. Its overall conclusion was that adenotonsillectomy is the primary treatment for OSA, and RPE may not provide benefits.

Again, these were good sources of evidence.

Functional appliances and growth modification

The panel concluded that there was no evidence to support the prophylactic use of functional appliances as a preventive measure for sleep disordered breathing. This is a logical conclusion because there are no studies showing that functional appliances can meaningfully change or alter the skeletal pattern.

Can we help in the treatment of sleep-disordered breathing? 

A key message from this research and discussion is that treating sleep-disordered breathing primarily falls to our medical colleagues. We clearly have a role in screening for sleep disordered breathing and referring patients. Once the physician has made an accurate diagnosis, we can contribute to relevant treatment, but we must collaborate closely with sleep specialists and other experts.

We can also offer care with maxillary expansion, but only in a few carefully selected cases. This is when there is a clear skeletal discrepancy, most often accompanied by a crossbite. It is absurd to expand maxillae simply because “we feel they are not wide enough” or that we need to increase the width by 3 to 5 mm to some hypothetical ideal imagined by an advocate who does not understand the existing research in this area.

What did I think?

I did not have the space or time to explore all aspects of this white paper, so I decided to focus on perhaps the four most controversial areas. I believe the evidence they used to support their recommendations was entirely relevant. The studies they selected were generally of good quality. The most striking finding, in my view, was that there were very few studies they could include. This is because there appears to be a lack of high-quality research.

This reinforces my opinion that, across this entire field, there is a surprising lack of evidence. This is a significant finding because, if evidence of benefit is absent, we cannot ethically promote or provide treatment that claims to address a disorder.

FInal thoughts 

This is an extremely useful and valuable source of information for all orthodontists. The recommendations are very clear. Importantly, they provide straightforward guidance on what we should and shouldn’t do. This means that if we perform treatment that disregards these recommendations, we may be acting unethically.

The response by some to the white paper has been unbelievably arrogant. Some detractors even suggest that their personal viewpoint or that of their ENT colleagues is more important than anything included in this document. Alternatively, some suggest the White Paper is flawed but do not specify where these flaws lie. Others have claimed that the AAO is protecting organised orthodontics. I don’t even understand what this means.

I have been an orthodontist for 40 years. Over this time, I have witnessed several “waves of nonsense”. These include orthodontic TMD treatment, non-extraction approaches for everyone, orthodontic vibrators, localised trauma to speed up tooth movement, orthotropics, and self-ligation. All have gained momentum, generated profit, and preyed on vulnerable patients. However, when science and the truth catch up with these claims, the new treatments vanish and we return to conventional, sensible orthodontics. This paper by the AAO is a significant step in the right direction.

If we accept and adhere to the recommendations of the White Paper, we can deliver a valuable service to our patients. This should also keep us sufficiently occupied.

What are your thoughts? Would you be interested in discussing this further in the comments?

       

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This new study is a population-based investigation into the effectiveness of interceptive orthodontics. A team from the well-known orthodontic department in Gothenburg, Sweden, conducted the study. The European Journal of Orthodontics published the paper. 

Interceptive orthodontics in practice: a 5-year population-based study

Anna Westerlund et al. 

EJO advanced access: https://doi.org/10.1093/ejo/cjaf113

The authors provided a clear introduction that outlined the rationale for the study. The aim of their study was to examine the delivery of orthodontic care within one district of the Swedish public dental healthcare system. In his region, interceptive care is delivered by general dentists in close consultation with orthodontists. Importantly, fixed appliance treatment is carried out exclusively by specialists. A total of 125 general dental clinics, staffed by 600 dentists, provide care to more than 380,000 children. 

The authors outlined that this publicly funded system does not aim for optimal outcomes in a small, highly selected group of patients from interceptive treatment. In effect, the aim of early treatment is to provide a brief intervention during the mixed dentition to reduce the need for treatment and eliminate the need for a second phase. This may be considered a successful outcome. They do not aim for ideal occlusion in all their patients at this point.  

When eligible patients are older, specialist practitioners provide fixed appliance treatment to achieve an ideal occlusion.

What did they ask? 

They did this study to

“Evaluate the scope of interceptive orthodontic care, specifically involving the use of activator, removable plate, quad helix and EOT appliances. This care was delivered by general dental practitioners under the supervision of orthodontic specialists”.

What did they do? 

They collected their data through a retrospective review of patient records from the electronic dental record system used in the public dental service in Västra Götaland, Sweden. 

The study population included all children and adolescents aged 0-18 years who were eligible for free interceptive orthodontic treatment. They were particularly interested in patients who had been treated with the following:

• Activator
• EOT
• Quad helix for posterior crossbites
• Removable plate for anterior crossbites

For each treatment, they defined it as successful, partially successful, or a failure.

They set out clear definitions for these; for example, for the treatment of an increased overjet with an activator:

• A successful treatment was an overjet of less than 5 mm
• A partial success was some improvement, but with an overjet remaining of >5 mm
• A failure was negligible or minimum effect

 They collected data from the medical record system for the period 2020-2024  

What did they find?

21,946 interceptive orthodontic treatments were carried out during the 5-year study period. 

Of these, 10511 involved removable plates. 6455 were treated with activator appliances. 3164 were quad helix appliance treatments, and 1816 were involving extra-orval traction. 

They then examined the patient records from 2020. These showed that 4,745 patients received interceptive treatment. They analysed the data more closely for 4,013 of these patients.

Activator Group. 

1,327 patients had received treatment with the Activator. Their mean age was 10 years. The mean treatment duration was 1.7 years (SD 0.6), with a mean of 11 (SD 5.2) visits per patient. The success rate was 56%. 

EOT  

The mean age of this group of patients was 11.2 years, and 101 patients received treatment. The average treatment duration was 1.1 years, with a mean of 11.2 visits. The overall success rate was 57 per cent. Most treatment failures were due to lack of compliance. 

Removable plate,

This group comprised 1,913 patients. The mean age was 11.0 and the mean treatment duration was 1.1 years, with a mean of 12.1 visits. The treatment success rate was 65%.

Quad Helix

672 patients received treatment with the quad helix appliance. The mean age at treatment start was 10.2 years, with treatment lasting 0.9 years. The treatment success rate was 82%. 

They also noted that appliances that rely heavily on patient cooperation achieved a fairly high success rate of just over 50%.

Their overall conclusion was 

“Interceptive orthodontic treatment in general dental practice can yield reliable, effective results when delivered with appropriate planning and follow-up”.

What did I think?

This is a very interesting study that was both ambitious and well executed. Studies of this nature are very difficult to carry out, and this team should be congratulated on the ambition and execution of their study.  

When we consider the results, we need to remember that the aims of the interceptive treatment they provided were not to achieve a perfect occlusion. The main objective of the treatment is to reach the eligibility threshold for cost-free care, thereby reducing the need for treatment and eliminating the need for a second phase. 

I emailed the lead author about some aspects of this study, and she also informed me. that if a treatment fails or there is a relapse resulting in IOTN grades 4 and 5, the patient is given a new opportunity for treatment with fixed appliances. 

We need to consider whether the findings of this study may not be fully relevant to the delivery of care in other countries. For example, in the USA, 2-phase treatment is likely to be more frequently used than in other countries. It could be argued that the final aim of treatment is always an ideal occlusion. Nevertheless, we know little about the effectiveness of phase I treatment, and it may not differ from the findings in this study.

Final thoughts

We need to consider whether this form of interceptive treatment is effective. From an individual patient’s perspective, one could argue that it is not, because treatment is not “ideal” at the end of the interceptive phase. However, from a public health perspective, the success rates are relatively high, indicating that interceptive treatment reduced the degree of malocclusion in this sample of patients. One could then argue that this is a good public health measure.  

However, in the long term, it is crucial that investigators thoroughly evaluate the treatment after the child has had the opportunity to receive Phase II intervention. Studies of this nature are essential for accurately assessing the true effectiveness of interceptive orthodontic care. This type of research, which evaluates the effectiveness of orthodontic intervention at a population level, is invaluable.

       

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Introduction

The American Association of Orthodontists published a white paper in 2019 on obstructive sleep apnea (OSA) and orthodontics, which provided an evidence-based, pragmatic guide for orthodontists on how best to manage these patients in an orthodontic environment. This new publication updates these guidelines, and we have summarised the main findings relevant to the management of children. The good news is that this article is Open Access: 

Sleep-disordered breathing and orthodontics: An American Association of Orthodontists white paper update

Juan Martin Palomoa, Julia Cohen-Levy,  Carlos Flores-Mirc,∙Rooz Khosravie, Mitchell Levine, Michael Pickard,Jackie Hittner, John Callahan, Steven M. Siegeli

AJO-DDO on line: DOI: 10.1016/j.ajodo.2026.01.014

These are the main findings of the group;

What did I think?

There have been controversies in orthodontics over the history of our specialty and in many respects, the role of the orthodontist in management of sleep disordered breathing is the 21st century controversy. Like most of these subjects, marginal and unsubstantiated views often dominate the narrative. These guidelines represent a pragmatic and balanced view based upon the best available evidence (and we would all agree that the current evidence base is lacking) written by a wide-ranging panel of experts. They are a very sensible set of recommendations and should be read by both generalists and specialists alike.

Orthodontists and other oral healthcare professionals are well-placed to play a role in the management of sleep-disordered breathing, but it must be evidence-based.

       

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Over the past 20 years, many studies have evaluated the effectiveness of the Twin Block compared with other functional appliances. Most of these have shown that, while the appliance is effective, the cooperation rate is not as high as we would hope. One recent development designed to improve cooperation is the modified clear Twin Block. Instead of being constructed from acrylic, this appliance is made from thermoplastic materials and cold-cure acrylic bite blocks. The aim of this design is to reduce bulk and weakness, improve aesthetics and comfort, and hopefully increase patient compliance. 

It has also been suggested that capping the appliance may reduce the side effect of extruding maxillary posterior teeth and proclining the lower incisors. The effectiveness of this appliance was examined in this new study. 

A team from Baghdad, Iraq, did this study. The European Journal of Orthodontics published the paper. 

A modified clear twin block appliance for treatment of class II malocclusion: a randomized clinical trial

Anosh A Haik et a

EJO advance access,  https://doi.org/10.1093/ejo/cjaf103

What did they ask? 

They did this study to answer the following question: 

“What is the effectiveness of a modified clear twin block compared to a conventional Twin Block “?

What did they do? 

They carried out a multi-centre, single-blinded, randomised clinical trial with two-arm parallel groups. 

The PICO was 

Participants 

Orthodontic patients who were rapidly growing with a skeletal Class 2 malocclusion with an OVA jet greater than or equal to 8 mm 

Intervention 

A modified clear Twin Block made from thermoplastic material. With ramps made from cold cure ccrylic. An expansion screw is installed in the upper component of the appliance.

Comparison. 

Standard acrylic Twin Block. 

Outcome 

The primary outcome was a cephalometric evaluation using many cephalometric measurements. Secondary outcomes. 

These were linear measurements of the teeth made from scanned maxillary models aligned and superimposed on palatal rugae. In addition, the patients completed a questionnaire on their perceptions of the appliance, including pain and discomfort. 

They asked the patients to wear their appliances for 24 hours a day. The operator monitored patients’ compliance every 2 weeks and evaluated expansion progress and overjet changes every 4 weeks. The final record was taken after the overbite correction, and the buccal segment occlusal relationship was fully corrected. 

They conducted a clear sample size calculation to detect a 1.5 mm difference in overjet reduction between the two appliances. This indicated that they required 21 patients in each arm of the trial. To account for a potential dropout of 15%, they recruited a total of 48 patients. 

They used a pre-prepared randomisation, generated remotely by an independent person. Concealment was achieved using sealed envelopes.

 All data collection and measurement were done blind. The statistical analysis was rather simplistic, using univariate statistics across many variables. As a result, there is a risk of false positives due to the multiple related measurements. We need to bear this in mind when we look at the results.   

They conducted the study across several government-specialised dental centres and a private dental clinic. Although they did not specify the number of centres or operators involved in the study 

What did they find? 

They randomised 25 patients to each intervention, and all patients completed the study without any dropouts. The study began in September 2022 and was completed in June 2024. 

The mean age of patients at the start of treatment for the Twin Block group was 12.16 years, and for the modified Twin Block group, 11.76 years.

The active treatment duration was 9.14 ± 2.9 months for the Twin Block group and 8.8 ± 2.1 months for the modified Twin Block group.

 At the start of treatment, there were generally no differences between the two groups. However, there were statistically significant differences for SNA, SNB, and SN-Pog. They addressed this imbalance by carrying out an analysis of Covariance to adjust for these differences. However, they did not report this in any detail.

The team produced a large amount of data at the end of the treatment. Most of this concerned cephalometric measurements. As with most studies of this nature, we need to bear in mind the difference between statistical and clinical significance. In this respect, most of the differences were in the order of 1-2 degrees. Although they were statistically significant, I felt they were not clinically significant. However, the upper incisors were retroclined an additional 6 degrees with the conventional Twin Block. This suggests that the treatment may make many small changes that contribute to the overall treatment effect. This is similar to the results of many other studies into the effects of functional appliances and the results do not really add to our knowledge.

 There were no differences in treatment duration. The active treatment duration was 9.14 ± 2.9 months for the Twin Block group and 8.8 ± 2.1 months for the modified Twin Block group.

 When they evaluated patient perceptions of their appliances, however, they found several differences between the two treatments. The results showed that the modified twin block group of patients had a better treatment experience. This was particularly relevant when considering factors such as appliance breakage, difficulty in keeping the appliance clean, changes in speech during appliance wear, and improvement in teasing or bullying. The modified twin block group also had a less pronounced effect on their quality of life with respect to embarrassment, speech, and general appearance.  

 Their overall conclusion was 

“The modified Twin Block was effective in treating patients with Class II mandibular protrusion. It is comparable with slightly advantageous results to the standard Twin Block Appliance”.

What did I think?

This was another study that provides us with some useful information on the Twin Block appliance.  The trial was conducted well and reported in accordance with the CONSORT guidelines.  

One major strength of this study was that it was carried out in the real-world setting of government-run clinics with multiple operators. This is in contrast to many other studies conducted in university dental schools with resident operators. As a result, its findings are generalizable. However, I was unsure on the number of treatment centres and operators. This information was important and it should have been included in the paper.

The authors drew attention to several shortcomings in their study. The most important of these was that they only followed the patients until the completion of the functional appliance phase of treatment. As a result, they did not take into account the effect of any follow-up fixed appliance treatment or potential relapse. This is particularly important and is characteristic of many functional appliance trials. I hope the authors continue this study and report their end-of-treatment data.

 My other criticism is a favourite bugbear of mine. This was because they led on cephalometrics as their primary outcome measure. We know from many cephalometric studies that these measurements are only relevant to orthodontists and are clinically insignificant, yet statistically significant. In fact, in several parts of the discussion the authors mentioned that the MTB resulted in better treatment effects than the CTB. However, this was not supported by the data.

Nevertheless, it was great to see that they used a patient-based outcome measure that reflected their patients’ values. While I was not familiar with this measure, it certainly seemed to indicate considerable advantages of the modified Twin Block appliance. In general, patients appeared happier with the modified Twin Block than with the acrylic Twin Block. However, it was important to note that this was not reflected in the cooperation rates, as all patients completed the study. 

Final comments 

With all papers, we need to consider whether the findings would persuade us to change our practice. I certainly found this paper very interesting, and I would use this appliance on a few selected patients, as I believe it may have value in the future. 

I would like to congratulate the authors on this very useful and clinically relevant research project. Nevertheless, I think that this paper would have been improved by better refereeing, as there were several areas that were not entirely clear.

       

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