Comprehensive fixed appliance orthodontic treatment is a lengthy procedure typically taking between 20-30 months to complete. In recent decades a number of surgical and non-surgical approaches have been advocated to speed tooth movement and reduce the duration of treatment. Surgical adjunctions have included corticotomy, laser-assisted flapless corticotomy (LAFC), micro-osteoperforations (MOPs), piezocision, and local injection of platelet-rich fibrin or plasma products, while non-surgical adjuncts have included variation in bracket design and force-delivery systems, low-level laser therapy (LLLT) (or photobiomodulation), vibration, pulsed electromagnetic fields, and low-intensity pulsed ultrasound.
The main aim of this review was to appraise randomised controlled trials (RCTs) assessing treatment duration to fully retract maxillary canines after maxillary first premolar extraction in adolescent and adult orthodontic patients using fixed appliances.
Methods
A protocol was registered on the PROSPERO database. Searches were conducted in the Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Cochrane Database of Abstracts of Reviews of Effects, Embase, Medline, Scopus, Web of Science, and Latin American and Caribbean Health Sciences Literature databases with no restrictions on language or date. This was supplemented with a search of the Directory of Open Access Journals, Digital Dissertations, meta- Register of Controlled Trials, and Google Scholar. RCTs assessing the duration and rate of maxillary canine retraction using fixed appliances with or without treatment adjuncts were considered. Two reviewers independently screen and selected studies, extracted data and assessed risk of bias using the Cochrane risk of bias 2.0 tool (RoB2). Random-effects meta-analyses of average rates or mean differences (MD) and 95% confidence intervals were undertaken. The certainty and quality of evidence were rated using the Grades of Recommendations, Assessment, Development, Evaluation (GRADE).
Results
- 50 RCTs (44 split-mouth, 6 parallel-group) involving a total of 811 patients were included.
- Trials were conducted in 17 countries, Australia, Brazil, China, Dominican Republic, Egypt, India, Iran, Japan, Jordan, Malaysia, Pakistan, Saudi Arabia, Switzerland, Syria, Thailand, Turkey, and the United States.
- Almost all the trials were conducted in university (74%) or hospital clinics (20%) with 48(96%) being single-centre studies.
- 14 studies were considered to be at high risk of bias and 14 at low risk of bias with 22 having some concerns.
- A majority of trials used adjuncts to orthodontic treatment, 18 involved surgically assisted orthodontics, 14 used low-level laser therapy (LLLT), 4 used vibration, and one low-intensity pulsed ultrasound with 3 using surgically assisted orthodontics and LLLT with one using surgically-assisted orthodontics and local injection of platelet-rich fibrin and 3 local injection of platelet-rich fibrin or platelet-rich plasma.
- A range of anchorage reinforcement methods were employed including, temporary anchorage devices (TADs) [18 studies], transpalatal arch (TPA, including Nance button [15 studies], both TADs and TPA[1 study], TPA and head- gear[1 study], vertical stopped loops[2 studies], ligation of second premolars and first molars together[4 studies], 2 included the second molar in the anchor unit, and 7 trials did not report on anchorage reinforcement methods.
- The pooled average time to achieve complete retraction of the maxillary canines = 4.98 months (95%CI; 2.92 to 12.88 months) [2 studies].
- Pooled cumulative average canine tooth movement from baseline (beginning of canine retraction) is shown in table below
| Time period | No. of studies | Canine movement from baseline (95%CI) |
| 1 month | 23 | 0.97 mm (0.79 to 1.16) |
| 2 months | 20 | 1.83 mm (1.52 to 2.14) |
| 3 months | 23 | 2.44 mm (2.10 to 2.79) |
| 4 months | 6 | 3.49 mm (1.81 to 5.17) |
| 5 months | 2 | 4.25 mm (0.36 to 8.14) |
- Surgically assisted orthodontics was associated with greater canine retraction at all time points.
| Time period | No. of studies | Mean difference (95%CI) |
| 0-1 month | 10 | 0.52 mm (0.21 to 0.84) |
| 0-2 months | 20 | 0.53 mm (0.06 to 0.97) |
| 0-3 months | 23 | 0.67 mm (0.20 to 1.13) |
| 0-4 months | 6 | 1.13 mm (0.60-1.66) |
Conclusions
The authors concluded: –
The average time to achieve complete retraction of the maxillary canine using fixed appliances was around 5.0 months. Most studies used split-mouth randomization to investigate canine retraction for around 1-3 months, with substantial heterogeneity across studies. At 3 months of treatment, high-quality evidence supported greater canine retraction with surgically assisted orthodontics.
Comments
The authors have taken a sound methodological approach to this review pre-registering a protocol and following guidance in the Cochrane handbook and PRISMA. An unrestricted search of a wide range of databases was undertaken with 50 RCTs being identified. As highlighted by the authors only 4 of the included studies addressed the reviews primary outcome of canine retraction duration suggesting an average duration of 4.98 months. While the review indicates that surgically assisted orthodontics results in shorter duration in is recommended that this should be interpreted cautiously because of the limited number of studies contributing to the analysis. Almost all of the included studies use a split-mouth model and while this is convenient it assumes equivalence of both sides of the arch and independence to different bilateral interventions and issue noted by the authors. The short-term nature of the studies is also highlighted and only two of the 50 trials followed up patients to the completion of retraction. The included trials also demonstrate a high degree of heterogeneity, related to clinical settings, patient demographics, type of malocclusion, appliance type, treatment adjuncts orthodontic mechanics and appointment intervals. The authors suggest that future studies should focus on the overall duration of treatment and make the suggestion that interventions should need to demonstrate a 2-month reduction in treatment duration to be clinically significant.
Links
Primary Paper
Wazwaz F, Seehra J, Carpenter GH, Papageorgiou SN, Cobourne MT. Duration of canine retraction with fixed appliances: A systematic review and meta-analysis. Am J Orthod Dentofacial Orthop. 2023 Feb;163(2):154-172. doi: 10.1016/j.ajodo.2022.08.009. Epub 2022 Dec 1. PMID: 36464569.
Other references
Dental Elf – 20th Apr 2020
Micro-osteoperforation and the rate of orthodontic tooth movement
Dental Elf – 24th Mar 2016
Corticotomy for facilitating orthodontic treatment – limited research available
Dental Elf – 6th Jul 2015
