Another trial on surgical methods of speeding up tooth movement….I’m not convinced..
Another trial on speeding up tooth movement
Over the past couple of years several investigators have done randomised trials into methods of speeding up tooth movement. Earlier this year I managed to miss this study into the effects of corticotomy and piezocision. I am going to discuss this now.
One of the most interesting areas of orthodontic research is attempting to make tooth movement faster. There is no doubt that this would be a major development in orthodontic treatment. The authors of this study did a trial of different methods of increasing the rate of tooth movement.
Noha Hussein Abbas et al
Am J Orthod Dentofacial Orthop 2016;149:473-80 http://dx.doi.org/10.1016/j.ajodo.2015.09.029
What did they ask?
They investigated the effect of corticotomy and piezocision on the rate of canine retraction.
What did they do?
20 patients who were aged 15 to 25 years with Class II Division 1 malocclusion took part in the study. They randomly divided the patients into two groups.
Group 1: Corticotomy was randomly assigned to one side of the maxillary arch and the other had no intervention
Group 2: Piezocision was randomly assigned to one side of the arch and the other side had no intervention.
The randomisation was performed by tossing a coin. They did not provide any details on concealment or sample size calculation.
They then fitted 0.022 slot fixed appliances and extracted the first maxillary premolar teeth when they had completed initial alignment and levelling. At this point they also carried out the corticotomy or piezocision.
They then fitted 016 x 022 stainless steel wire and started retraction using nickel titanium coil springs (150g force on each side). They saw the patient every two weeks and reactivated the springs. At these appointments they took impressions for measurement of the tooth movementThey scanned the study casts using a flatbed scanner and measured the tooth movement, using the palatal rugae as a reference point. They did not mention how they actually made the measurements and they did not carry out an error analysis. They also took CBCT scans at the start and at the end of retraction to measure root resorption. I will not discuss these findings.
What did they find?
They showed that the rate of canine crown tip was greater in the piezocision and corticotomy sides of the mouth.
They presented the data in a table that showed the amount of tooth movement every two weeks to 2 months.
I thought that data tables we unclear. Consequently, I calculated the amount of tooth movement over the 12 week period and put this in this table.
|Time in days
At the end of their paper they concluded that
“Corticotomy facilitated orthodontics and piezocision are effective treatment alternatives that decrease the time required for canine retraction”.
They also suggested that corticotomy facilitated orthodontics was 1.5/2 times faster than conventional orthodontics. Piezocision was 1.5 times faster than conventional orthodontics.
What did I think?
This paper was similar to other studies which have evaluated the effect of these new techniques. Unfortunately, there is a tendency for authors to measure tooth movement for just one phase of treatment. For example, in this paper they measured canine retraction. While this may show that the new techniques increase tooth movement in this phase. We must be careful that we do not extrapolate these result to suggest that these new techniques will result in a reduction in total treatment time. I have not read any study that follows treatment to completion.
The other important characteristic of the studies is that the authors make claims such as “1.5 times faster”, yet they do not consider the effect size. You will see from my table that the difference in tooth movement between the interventions and control was 2.2mm for corticotomy and 1.5mm for piezocision over a 12 week period. I am not convinced that these are clinically significant differences and I cannot help wondering if this additional “gain” is worth the traumatic and invasive procedures.
Another important point on their methodology was that I could not find any data on the error analysis. This is essential in tooth movement studies, as we are measuring small distances.
Finally, I would like to point out that in the introduction to the paper the authors stated that the average rate of canine retraction was 0.5 to 1mm per month. Yet in their study neither the control or the intervention rate of tooth movement was not too different from this amount.
In summary, while these results are interesting they do not convince me that these rather invasive methods increase the rate of tooth movement. I would have problems consenting my patients to have this type of surgery for such limited benefits. I wonder how other people manage?
Emeritus Professor of Orthodontics, University of Manchester, UK.