Review question
Do additional non-surgical procedures that claim to accelerate orthodontic tooth movement reduce the overall length of orthodontic treatment?
Background
Throughout the world, orthodontic treatment is used to correct the position of teeth in adolescents and adults when they experience problems with their teeth and bite. Orthodontic appliances can vary in type, and include fixed braces (made up of brackets glued to the teeth and then connected by wires) and removable appliances, e.g. clear aligners, which are a set of clear plastic removable gum shields that fit closely over the teeth. Depending on the tooth and bite problem, the length of time for orthodontic treatment may range from several months to several years. However, most full orthodontic treatments take typically around 20 months. Orthodontic treatment is known to improve how a smile looks, which in turn has a positive impact on patients; however, orthodontic treatment can carry some unwanted risks, such as tooth decay and shortening of tooth roots. Accelerating the rate of tooth movement may help to reduce the length of time needed for a course of treatment and may reduce the unwanted effects of orthodontic treatment that can sometimes occur. Several methods, including surgical and non-surgical treatments, have been suggested to accelerate orthodontic tooth movement. The evidence relating to non-surgical treatments to accelerate orthodontic tooth movement is assessed in this review.
Authors for Cochrane Oral Health carried out this update of the systematic review of existing studies. The evidence on which it is based is current up to September 2022.
Study characteristics
We included 23 studies involving a total of 1027 participants, both males and females, and children and adults. These investigated light vibrational force appliances, low level laser therapy and light-emitting diode (LED) therapy as extras to orthodontic treatment in both private practice and university hospital settings. The trials evaluated different aspects of orthodontic tooth movement and side effects. In the studies, participants were being treated either with fixed orthodontic appliances or orthodontic removable aligners. The participants in all studies had dental (tooth) crowding in one or both arches. Some studies included participants requiring tooth extractions for relief of dental crowding and correction of their bite with space closure, while other studies included participants who did not require dental extractions. The percentage of participants lost to follow-up in the studies included in this review ranged from 0% to 27% of the original samples.
The studies evaluated seven outcomes: duration of orthodontic treatment; number of appointments required to adjust orthodontic appliance, the rate of orthodontic tooth movement at different stages, patient perception of pain and discomfort, patient reported need for painkillers, and unwanted side effects. There were substantial differences between some of the studies; however, it was possible to combine the results of some studies for the light vibrational forces and low level laser therapy.
Key results
There is low-certainty evidence to suggest that applying light vibrational forces during orthodontic treatment (fixed or removable appliances) has no significant advantage for any of the outcomes assessed.
There is very low-certainty evidence to suggest that applying low level laser and LED therapy can reduce the duration of the early stage of orthodontic fixed brace treatment (alignment), but it is difficult to estimate the impact of this outcome on the full comprehensive orthodontic treatment duration.
Conclusion
From the limited evidence available, we did not find a benefit from the use of light vibrational forces or photobiomodulation for the reduction of orthodontic treatment duration. However, there could be a potential benefit from photobiomodulation to reduce the length of the early stage of orthodontic treatment only and increase the speed of orthodontic tooth movement; it is important to realise that the results from discrete phases do not necessarily have similar impact on the full orthodontic treatment duration. Further well-designed studies with longer follow-up are needed.
Certainty of the evidence
Our certainty about the evidence is low to very low.
The evidence from randomised controlled trials concerning the effectiveness of non-surgical interventions to accelerate orthodontic treatment is of low to very low certainty. It suggests that there is no additional benefit of light vibrational forces or photobiomodulation for reducing the duration of orthodontic treatment. Although there may be a limited benefit from photobiomodulation application for accelerating discrete treatment phases, these results have to be interpreted with caution due to their questionable clinical significance. Further well-designed, rigorous RCTs with longer follow-up periods spanning from start to completion of orthodontic treatment are required to determine whether non-surgical interventions may reduce the duration of orthodontic treatment by a clinically significant amount, with minimal adverse effects.
Deviation from a normal bite can be defined as malocclusion. Orthodontic treatment takes 20 months on average to correct malocclusion. Accelerating the rate of tooth movement may help to reduce the duration of orthodontic treatment and associated unwanted effects including orthodontically induced inflammatory root resorption (OIIRR), demineralisation and reduced patient motivation and compliance. Several non-surgical adjuncts have been advocated with the aim of accelerating the rate of orthodontic tooth movement (OTM).
To assess the effect of non-surgical adjunctive interventions on the rate of orthodontic tooth movement and the overall duration of treatment.
An information specialist searched five bibliographic databases up to 6 September 2022 and used additional search methods to identify published, unpublished and ongoing studies.
We included randomised controlled trials (RCTs) of people receiving orthodontic treatment using fixed or removable appliances along with non-surgical adjunctive interventions to accelerate tooth movement. We excluded split-mouth studies and studies that involved people who were treated with orthognathic surgery, or who had cleft lip or palate, or other craniofacial syndromes or deformities.
Two review authors were responsible for study selection, risk of bias assessment and data extraction; they carried out these tasks independently. Disagreements were resolved by discussion amongst the review team to reach consensus.
We included 23 studies, none of which were rated as low risk of bias overall. We categorised the included studies as testing light vibrational forces or photobiomodulation, the latter including low level laser therapy and light emitting diode. The studies assessed non-surgical interventions added to fixed or removable orthodontic appliances compared to treatment without the adjunct. A total of 1027 participants (children and adults) were recruited with loss to follow-up ranging from 0% to 27% of the original samples.
Certainty of the evidence
For all comparisons and outcomes presented below, the certainty of the evidence is low to very low.
Light vibrational forces
Eleven studies assessed how applying light vibrational forces (LVF) affected orthodontic tooth movement (OTM). There was no evidence of a difference between the intervention and control groups for duration of orthodontic treatment (MD -0.61 months, 95% confidence interval (CI) -2.44 to 1.22; 2 studies, 77 participants); total number of orthodontic appliance adjustment visits (MD -0.32 visits, 95% CI -1.69 to 1.05; 2 studies, 77 participants); orthodontic tooth movement during the early alignment stage (reduction of lower incisor irregularity (LII)) at 4-6 weeks (MD 0.12 mm, 95% CI -1.77 to 2.01; 3 studies, 144 participants), or 10-16 weeks (MD -0.18 mm, 95% CI -1.20 to 0.83; 4 studies, 175 participants); rate of canine distalisation (MD -0.01 mm/month, 95% CI -0.20 to 0.18; 2 studies, 40 participants); or rate of OTM during en masse space closure (MD 0.10 mm per month, 95% CI -0.08 to 0.29; 2 studies, 81 participants). No evidence of a difference was found between LVF and control groups in rate of OTM when using removable orthodontic aligners. Nor did the studies show evidence of a difference between groups for our secondary outcomes, including patient perception of pain, patient-reported need for analgesics at different stages of treatment and harms or side effects.
Photobiomodulation
Ten studies assessed the effect of applying low level laser therapy (LLLT) on rate of OTM. We found that participants in the LLLT group had a statistically significantly shorter length of time for the teeth to align in the early stages of treatment (MD -50 days, 95% CI -58 to -42; 2 studies, 62 participants) and required fewer appointments (-2.3, 95% CI -2.5 to -2.0; 2 studies, 125 participants). There was no evidence of a difference between the LLLT and control groups in OTM when assessed as percentage reduction in LII in the first month of alignment (1.63%, 95% CI -2.60 to 5.86; 2 studies, 56 participants) or in the second month (percentage reduction MD 3.75%, 95% CI -1.74 to 9.24; 2 studies, 56 participants). However, LLLT resulted in an increase in OTM during the space closure stage in the maxillary arch (MD 0.18 mm/month, 95% CI 0.05 to 0.33; 1 study; 65 participants; very low level of certainty) and the mandibular arch (right side MD 0.16 mm/month, 95% CI 0.12 to 0.19; 1 study; 65 participants). In addition, LLLT resulted in an increased rate of OTM during maxillary canine retraction (MD 0.01 mm/month, 95% CI 0 to 0.02; 1 study, 37 participants). These findings were not clinically significant. The studies showed no evidence of a difference between groups for our secondary outcomes, including OIIRR, periodontal health and patient perception of pain at early stages of treatment.
Two studies assessed the influence of applying light-emitting diode (LED) on OTM. Participants in the LED group required a significantly shorter time to align the mandibular arch compared to the control group (MD -24.50 days, 95% CI -42.45 to -6.55, 1 study, 34 participants). There is no evidence that LED application increased the rate of OTM during maxillary canine retraction (MD 0.01 mm/month, 95% CI 0 to 0.02; P = 0.28; 1 study, 39 participants ). In terms of secondary outcomes, one study assessed patient perception of pain and found no evidence of a difference between groups.