Let’s look at some evidence….
Twin V Passive Self Ligation.
Title: Systematic review of self-ligating brackets
Purpose: To identify and review the ortho literature regarding the efficiency (chair time, treatment time), effectiveness (occlusal indices, arch dimensions), and stability of tx with self-ligating brackets compared with conventional brackets.
Self-ligating brackets are divided into active and passive, according to their mechanisms of closure. Active self-ligating brackets have a spring clip that stores energy to press against the arch wire for rotation and torque control (ex. In-Ovation, SPEED and Time). Passive self-ligating brackets usually have a slide that can be closed which does not encroach on the slot lumen, thus exerting no active force on the archwire (ex. Damon and SmartClip).
Materials and Methods: Study Type: Systematic review
Population: An electronic search of 4 data bases was performed from 1966 to 2009 + supplemental hand searching.
Inclusion Criteria: (1) clinical studies that compared self-ligating with conventional appliances regarding efficiency, effectiveness, or stability; (2) all ages and sexes; and (3) all languages.
Exclusion Criteria: (1) in-vitro, ex-vivo, or animal studies; (2) studies with no comparison group; and (3) editorials, opinions, or philosophy articles with no subjects or analytical design.
Methods: Quality assessment of the included articles was performed. Data were extracted by using custom forms,
Weighted mean differences were used to construct forest plots of continuous data. Odds ratios were used for dichotomous data. Heterogeneity was assessed and publication bias was assessed with funnel plots, if possible.
- 16 studies met the inclusion criteria: 2 RCTs with low risk of bias, 10 cohort studies with moderate risk of bias, and 4 cross-sectional studies with moderate to high risk of bias.
- Total treatment time and occlusal indices: No stat significant difference
- Rate of alignment and space closure: No stat significant difference
- Chair time: Results showed a mean savings of 20 seconds/arch for opening the slides of Damon brackets compared with removing the ligatures of conventional brackets. However, there was no signif difference between the time needed for closing the slides of Damon brackets and replacing the ligatures of conventional brackets.
- Arch dimension and lower incisor inclination: For intercanine and intermolar widths, there was no signif difference between the 2 groups.
- For incisor proclination: self-ligating brackets resulted in slightly less incisor proclination (1.5°).
- Bracket failure rate: No stat significant difference
- Stability: Some claim that lower forces produced by self-ligating bracket systems might result in more physiologic tooth movement and more stable treatment results. However, studies on stability after treatment with self-ligating brackets are lacking at this time.
- Despite claims regarding clinical superiority of self-ligating brackets, evidence is lacking.
- Self-ligation does appear to have a signif advantage with regards to chair time, based on several cross-sectional studies.
- Analyses also showed a small, but stat significant, difference in mandibular incisor proclination (1.5° less proclination with self-ligating brackets compared with conventional brackets).
- No other signif differences in treatment time or occlusal characteristics after tx were found.
- Although 20 sec may be statistically sig, they may not be clinically significant and confounding factors may include the expertise of the operator.
- Similarly, although 1.5° less proclination with self-ligating brackets may be stat signif, it is within the range of measurement error.
- Claims that self-ligating brackets facilitate greater and more physiologic arch expansion and, therefore, allow more non-extraction treatment require more evidence.
Randomized clinical trial of orthodontic treatment efficiency with self-ligating and conventional fixed orthodontic appliances
Padhraig S.Fleming et al 2010
The purpose of this prospective study was to compare the efficiency of orthodontic treatment with Smart Clip self-ligating brackets and Victory conventional twin brackets (both, 3M Unitek, Monrovia, Calif).
Study Type: RCT
Population: Orthodontic patients at the Royal London Dental Inst
Sample: 66 conseq treated patients 33 twin/ 33 PSL. Pt age 11-21.
Inclusion: Non ex , perm dent, mild mand crowding
Exclusion: previous ortho, complex MH, Craniofacial anomalies, FTA appts, appliance breakages x3, hypodontia and surg pts
Data: two operators treating sample. Reference dental models taken before and after Rx and scored by independent tech. Analysis: ANCOVA analysis of covariance to compare the treatment effects of both appliances while accounting for differing pre-treatment variables. P<0.05
• 81% of subjects completed treatment (n=-54)
• Mean duration of treatment 19.92 months overall- mean time = 18.32 twin/ 21.41 PSL
• Mean number of visits 15.7
There was NO significant difference between the two systems on
- Treatment duration
- Number of visits
- The PAR score reduction during treatment
Marshall, SD., et al., Am J Orthod Dentofacial Orthop 2010; 138:128-131
Purpose: Readers’ Forum re: self-ligating bracket claims, AAO’s Council on Scientific Affairs (COSA) researching “what is the strength of research evidence to support claims that SL systems are superior to conventional brackets?”
Does lateral expansion of dental arch by SL brackets “grow” buccal alveolar bone?
Weakly supported by low-level evidence, still needs to be confirmed independently
Is lateral expansion of dental arch by SL brackets comparable to RME followed by FEA?
Weakly supported by low-level evidence (thesis), no peer-reviewed evidence, still needs to be confirmed independently
Is lateral expansion of dental arch by SL brackets stable in the long-term?
Weakly supported by low-level evidence (case reports), no peer-reviewed evidence, needs independent confirmation
Long-term stability of RME has been evaluated by systematic review
Are SL bracket systems more efficient and/or more effective than conventional FEA in treating malocclusions?
Current evidence does not support that SL systems are more effective or efficient than conventional FEA (only significant differences: time and final lower incisor alignment: 20 seconds less/arch and final LI inclination is 1.5 degrees less with SL systems)
Current evidence: no significant difference in tx time, alignment rate, space closure rate, final arch dimensions, occlusal outcomes between SL vs. conventional Fixed Edgewise Appliances.
Systematic review comparing SL vs. conventional FEA: no difference in total tx time, mandibular incisor alignment rate, rate of en-masse space closure, bracket failure rate, occlusal indices, arch dimensions
Do SL systems provide less friction at AW-bracket interface?
In vitro evidence that SL provide less friction, but uncertain re: reduced friction in in vivo AW-SL bracket system
Many in vivo factors cannot be replicated in vitro: forces of mastication, PDL response, bracket slot angulation and dimension, interbracket distance, moisture, temperature
Reduced friction system is needed for physiologically suitable forces (less hyalinization, also less patient discomfort) and to promote alveolar bone generation, lateral expansion of dental arch (helps to minimize incisor proclination in non-exo tx) important for reduced treatment time
Do SL bracket systems provide lower clinical forces vs. conventional FEA?
Only in vitro studies have been performed – conclude that SL systems have larger forces on buccally or lingually displaced teeth vs. conventional brackets
Do patients treated with SL brackets experience less pain during Tx?
3 clinical trials: variation in subjective pain experience within 1st 8 days of 0.014 CuNiTi AW (SL significantly less painful, no significant tendency to be less painful, no pain difference compared with conventional brackets – split mouth design), patients with SL brackets experiences more pain vs. conventional FEA when used 0.016x0.025 CuNiTi
Interpret results with caution due to risk of bias of prospective cohort and randomized trial studies
Are conventional brackets less hygienic than SL brackets?
No evidence supports this claim (some studies report elastomerics associated with increased plaque retention, perio aggravation)
Studies comparing periodontal parameters (PD, BOP) with SL vs. conventional FEA – no significant differences in PD or BOP, plaque accumulation greater on teeth with SL brackets and plaque had more aerobic bacteria (7 days an 18 months)
Pellegrini et al., - Split mouth design (n=14) of conventional vs. SL brackets measuring total bacterial counts and total oral streptococci at 1 and 5 weeks post-bonding – elevated oral streptococci levels around conventional brackets at 5 weeks, Pandis et al. (n=32): no difference between total bacterial levels at 12 weeks post-bonding
Systematic review: insufficient evidence that SL brackets are more hygienic vs.. conventional
Evidence supports SL brackets reduce chairtime
No significant differences in friction levels, force levels, tx time, alignment time, space closure time, arch dimensions, alignment and occlusal outcomes, patient discomfort levels, hygiene levels
No peer-reviewed evidence that SL bracket systems “grows buccal alveolar bone”, comparable to RME + FEA, long-term stability of lateral expansion