Is Corticotomy-Assisted RME Protraction Effective in Late Adolescence?

We all know that treating developing Class III malocclusion is complex. While there is increasing evidence of the effectiveness of protraction in treating developing malocclusions in the mixed dentition. We are unsure about the effectiveness of this treatment for adolescents. At this point, we tend to be left with the choice of attempting orthodontic treatment, attempting dental alveolar camouflage, or delaying and waiting for orthognathic surgery. 

This new study looked at the effectiveness of corticotomy-assisted RME and protection in late adolescence.  

A team from Turkey did the study. The American Journal of Orthodontics published the paper. 

What did they ask?

This study was conducted to find out protraction.

“The short-term effects of corticotomy-assisted RME and face mask therapy in late adolescent patients with skeletal Class 3 malocclusion compared with no treatment” 

What did they do? 

They did a prospective single-centre, non-randomised, controlled clinical study. 

The sample in this study was formed of orthodontic patients aged 13 to 16 years with a true skeletal Class 3 malocclusion with maxillary deficiency and an anterior crossbite. The investigators allocated them to two groups:

16 patients received corticotomy-assisted rapid maxillary expansion followed by face mask treatment.

16 received no treatment during a comparable observation period.

The patients underwent bilateral maxillary corticotomies under general anaesthesia. The surgeons raised mucoperiosteal flaps and made cortical cuts extending from the piriform aperture towards the pterygomaxillary region.

After expansion, the patients wore a facemask for 14–18 hours per day, applying 750–1000 g of force on each side. Treatment continued until they achieved a Class I occlusion and a positive overjet. The mean treatment duration was approximately 8 months.

Outcomes

The investigators collected lateral cephalograms and 3D facial photographs before and immediately after treatment. Their primary outcome was the position of Point A relative to the nasion perpendicular. They also measured numerous skeletal, dental, airway and facial soft-tissue variables.

Importantly, they sought to address the large number of statistical comparisons by applying a false-discovery-rate correction to the secondary outcomes. They also performed adjusted analyses that accounted for baseline measurements, age, sex, treatment duration, and skeletal maturity.

What did they find?

They presented an incredible amount of data on the cephalometric airway and facial scan changes. This created a wall of confusing “white noise”.  I have never seen so much data in a single paper.

I do not have the space to go into most of these here; however, they reported that the  principal changes in the treated patients compared with the control group were  

• 2.35 mm greater forward change at Point A;
• 4° improvement in ANB;
• 6 mm improvement in overjet;
• 3.4° increase in the mandibular-plane angle;
• 4.3° retroclination of the lower incisors; and
• 3.3 mm relative posterior change in pogonion on the cephalometric measurement.

The 3D facial analysis showed changes consistent with increased facial convexity and forward movement around the base of the nose. Nasal alar width increased by 1.57 mm and alar-base width by 1.97 mm.

There were no clinically or statistically significant differences in the airway between the groups. However, this was measured from the cephalograams, so I doubt that this data was useful.

Their final conclusion was

“Despite reduced growth potential, corticotomy-assisted RME and face mask therapy produce short-term skeletal and soft tissue improvements in patients with true skeletal Class 3 malocclusion. However, long-term stability and randomised comparative data are required.” 

What did I think?

This was an interesting paper that gave us some important, clinically relevant information on treatment effects, which are logical.

The study was well done, and I have no doubt that it was difficult to carry out. They reported many outcomes, which led to the inclusion of numerous cephalometric and other tables. As a result, I found it impossible to assess all the variables. This paper would certainly have benefited from a more focused analysis.

However, we need to consider carefully whether the nature of the study influences our interpretation of the results. In this respect, I feel there are many reasons for us to be cautious. Importantly, the authors have highlighted nine shortcomings in their study. This is possibly the largest number of shortcomings that I have seen authors acknowledge in a paper in the American Journal of Orthodontics.

I feel that there are several major areas of concern. Firstly, this was not a randomised trial. The control group was self-selecting, as they declined treatment because of school or family obligations. This means that the study has considerable selection bias. This is because patients willing to undergo this rather invasive treatment may differ from those who decline it. While I do agree that the statistical analysis this team used may correct some of the unknown measurable differences, this is also unlikely given the small sample size. 

I was also confused, as it appeared that the cephalometric and scan data were not blinded. Therefore, we cannot exclude examiner bias in this study. 

My last major concern was that poor cooperation was an exclusion criterion. This was identified by parent reports, the absence of signs of wear on the appliances, and, most importantly, a lack of change in overjet during the first three or four months. This means that the sample analysed may have been biased towards those who respond well, which could exaggerate the apparent effectiveness of the treatment.  I could not find any information on the number of patients who were excluded because of poor co-operation.

Final comment. 

We need to bear in mind these methodological deficiencies when we consider these findings. There is no doubt that the clinical changes are interesting and large enough to be clinically valuable. However, the problems with selection bias, proficiency bias, and data bias are substantial. As a result, we should be very cautious in interpreting these findings for our clinical treatment. There is certainly a need for randomised trials in this very interesting area.