Can a special archwire shorten treatment?
This is a guest post by Peter Miles who is a Specialist Orthodontist in Australia. It is clinician’s viewpoint about recent claims being made about a special archwire increasing the speed of tooth movement.
What are the claims?
Claims of accelerated treatment are certainly not new to orthodontics. The approaches to accelerated treatment range from;
- a mechanics perspective. For example self-ligating brackets claiming to reduce friction and more efficiently move teeth.
- to procedures claiming to alter the patient’s biological response. For example, vibration, micro-osteo perforations.
This Blog generally covers the literature published in the mainstream orthodontic journals. However, we live in the era of the internet, social media, blogs (such as this one) and e-journals. All of these allow rapid dissemination of information without the ‘impediment’ of peer review. This latest claim about archwires resulting in faster treatment prompted me to write this post.
ACHIEVING NEW STANDARDS OF CARE WHEN TECHNOLOGY MEETS BIOLOGY
The article discusses how the authors have changed to a wire sequence (0.016” SmartArch, 0.018”x0.025” SmartArch, 0.019”x0.025″ ss). They find this more efficient in terms of both numbers of appointments and treatment time compared with what they did previously.
Furthermore, they state this eliminates multiple appointments and 3 to 4 months of initial levelling and aligning to reach their working wire. I feel that these claims are not correct. I will address them by considering the science and art of wire properties and their sequence.
The wire sequence
If we examine the literature, we can see that this archwire sequence is not new. For example, fourteen years ago Nicky Mandall and her team examined three-wire sequences in the 0.022” slot system. They found that the most efficient wire sequence was a three-wire sequence (0.016″ NiTi, 0.018”x0.025” NiTi, 0.019”x0.025”ss). David Tidy also recommended this back in 1989 when the working archwire was achieved in only 4 months with two archwire changes in 0.018” slot system.
So it would seem the improved efficiency noted in this article is more likely to be caused by the change in the decisions they made on their wire sequence and appointment intervals.
The wire
We all know that Nickel-titanium archwires have an unloading plateau that allows them to remain active over an extended period without retying or reactivation. In clinical practice, this means that we can increase the time between appointments from 5-6 weeks to 8, 10 or 12 weeks (depending upon the initial alignment and type of movements). This has been my clinical experience for the past 25 years using this method. I have written about efficient wire sequences and appointment intervals when writing about the claims made regarding self-ligation back almost ten years ago.
Efficiency vs claims of speed
I propose that many of the claims of faster treatment are actually changes in practice ‘efficiency’. We are not moving the teeth any faster. We are simply making better decisions about which wire sequence to use and the appropriate appointment interval for them to work. Obviously, this varies depending upon the indications for an individual case. But as pointed out in previous research, one of the main factors in treatment efficiency are the decisions we as the Orthodontist make.
Emeritus Professor of Orthodontics, University of Manchester, UK.
One of the things that I have noticed following lockdown was that, as we had to leave the archwires in place for a long time, we actually allowed them to work. Sometimes we just need to stop interfering too soon and let the wires do their job.
Entirely agree. We have all had that patient that disappeared for several months following bond up with 014 niti wires in, and then turn up almost completed!! I think patience is definitely a virtue and not ‘ 6 month smile’ mindset!
Absolutely. Clinically there is really no standard archwire sequence, you just choose the wire to progress the teeth to the next stage. Sometimes you can put a 19×25 niti in straight away, shock horror, sometimes you need an 014 or 012 niti. The whole idea of an archwire sequence is a bit old hat.
I think the best comment I read lately comes from the conclusion of an article by Dr. Bhavna Shroff in the latest issue of Seminars in Orthodontics: « Perhaps the best and most predictable approach to shortening the lenght of orthodontic treatment is to diagnose the malocclusion properly and plan the treatment carefully so the mechanics used during therapy minimizes undesirable side effects ».
I think the thing that shortens treatment time the most is a well educated and engaged patient.
One of the interesting things about SmartArch is that it is a shape memory copper NiTi multiforce arch wire with seven zones of force according to the root surface area of the teeth and the interbracket span. Teeth with small root surface areas have less force than those with large root surface areas. The orthodontic basis for the design of the archwire is based on Viecilli RF and Burstone CJ Ideal orthodontic alignment load relationships based on periodontal ligament stress Orthod Craniofac Res 2015; 18 (Suppl.1): 180–186 and the metallurgical design based on Khan MI, Pequegnat A, Zhou YN 2013 Multiple Memory Shape Memory Alloys Advanced Engineering Materials 15(5); 386-393. The force levels in SmartArch are approximately proportional to the root surface areas determined by Freeman DC (1965) Root surface area related to anchorage in the Begg technique MS Thesis The University of Tennessee; this principle has been a core principle of anchorage/differential management for many years. The concept of an archwire in which the force is tailored to the root surface area of individual teeth, moderated by interbracket span, would seem to be a Good Thing (Sellar WC and Yeatman RJ 1930) and offers a level of sophistication previously denied to the orthodontist (notwithstanding that several manufacturers have produced triple force archwires with higher forces in the posterior region and lower forces in the anterior region of the archwire). A key question therefore is whether there are advantages to matching archwire force to the root surface area of individual teeth and how this might influence the process of treatment and the outcome of treatment.