Vol. 9, no. 2 (S), 53-58 (2011) EUROPEAN JOURNAL OF INFLAMMATION EFFECTIVENESS OF SELF-LIGATING ORTHODONTIC TREATMENT G. E. MANCINI1, F. CARINCI2, I. ZOLLINO2, A AVANTAGGIATO2, P. PUGLISI3, G. CACCIANIGA3,G. BRUNELLI3 Consultant, Orthodontist, Department of Maxillo Facial Surgery Galeazzi Institute, Milan, Italy Department of D.M.C.C.C., Maxillofacial Surgery Section, University of Ferrara, Ferrara, Italy 3 Department of Dentistry and Maxillofacial Surgery, Don Orione Institute, Bergamo Italy 1 2 Self-ligating brackets (SLBs) was introduced by Stolzenberg in the early 1930s. Many SLBs systems have been patented since then, but few have been put on the market. Since SLBs have reduced friction and hence less force needed to produce tooth movement, they are proposed to have the potential advantages of producing more physiologically harmonious tooth movement. Here a case series of patients treated with SLBs is performed to verify the eficiency, effectiveness, and stability of treatment. Eighteen patients (8 females and 10 males, median age 19 ± 9.2 years, min 10, max 39 years) affected by malocclusion were enrolled in this retrospective study. There were 8 class 1, 5 class 2 and 5 class 3 malocclusion, 3 cross-bites and 2 open-bite. Orthodontic treatment was performed by using 3MUnitek Smart Clip Brackets. Lateral teleradiographic projections of the cranium were used. The cephalometric analysis was performed by using Dolphin Imaging System McLaughlin Cephalometric Analisys. Several variables related to teeth position were investigated. Pearson Chi Square was used to detect statistical differences among studied variables. In the present study we demonstrated that SLBs are effectiveness tools to reach good clinical results since all studied variables (i.e. teeth position) have statistically signiicant differences between pre and post-treatment control. Self-ligation brackets (SLBs) are not a new concept. It was introduced by Stolzenberg in the early 1930s in the form of the Russel attachment designed to reduce treatment time by as much as 50% (1). Many SLBs systems have been patented since then, but few have been put on the market (2). Perhaps because of skepticism in the orthodontic society at that time, or the lack of promotion, it did not gain much popularity. During the past several decades, interest in SLBs has been rekindled (3). Particularly, they have undergone a revival over the past 30 years with the introduction of various types of new SLBs systems and with a variety of new appliances being developed. These SLBs have been touted to possess many advantages over conventional legated brackets (CLBs) (4). SLBs can be divided into 2 main categories, active and passive, according to their mechanisms of closure. Active SLBs have a spring clip that stores energy to press against the archwire for rotation and torque control (e.g. the Speed bracket). On the other hand, passive SLBs usually have a slide that can be closed which does not encroach on the slot lumen, thus exerting no active force on the archwire (e.g. the Damon bracket.) (5). According to the manufacturers, SLBs should not only be easier to handle in the ligation process but also show lower frictional forces than CLBs (6). This occurs because the usual steel or elastomeric ligatures are not necessary, and it is claimed that passive designs generate even less friction than active ones (7). Friction is inluenced by the physical characteristics of the archwire and bracket materials, and the method of attachment between archwire and bracket. CLBs incur increased levels of frictional resistance via the elastomeric attachment between bracket and archwire (8). On the contrary, self-ligation eliminates the requirement for an elastomeric attachment and is associated with considerably reduced friction with different archwires (9). Moreover, SLBs may also offer more certain archwire engagement, a requirement for less chair-side assistance Key Words: Orthodontics, self-legating, stability, outcome, relapse. Corresponding author: Prof. Francesco Carinci MD, DDS Department of D.M.C.C.C. Section of Maxillofacial Surgery Corso Giovecca, 203 44100 (Italy) Phone: +39.0532.455874 Fax: +39.0532.455582 e-mail : crc@unife.it Web: www.carinci.org 0393-974X (2011) 53 Copyright © by BIOLIFE, s.a.s. This publication and/or article is for individual use only and may not be further reproduced without written permission from the copyright holder. Unauthorized reproduction may result in inancial and other penalties 54 (S) G.E. MANCINI ET AL. with longer treatment intervals and fewer appointments, possible anchorage conservation, faster archwire removal and wire ligation (10), better infection control with improved oral hygiene (11) and consequently, less patient discomfort (3). However, SLBs have some disadvantages, including higher cost, possible breakage of the clip or the slide, higher proile because of the complicated mechanical design, potentially more occlusal interferences and lip discomfort, and dificulty in inishing due to incomplete expression of the archwires (5). Although SLBs have no many biomechanical advantages, they can be just as highly recommended for clinical application as CLBs. With reduced friction and hence less force needed to produce tooth movement, SLBs are proposed to have the potential advantages of producing more physiologically harmonious tooth movement by not overpowering the musculature and interrupting the periodontal vascular supply. Therefore, more alveolar bone generation, greater amounts of expansion, less proclination of anterior teeth, and less need for extractions are claimed to be possible (5). As SLBs are naturally smaller they are, from the patient’s perspective, clearly more desirable and attractive. And since patient compliance during orthodontic treatment is so important, that is a factor well worth considering (12). The purposes of this retrospective study were to analyze a case series of patients treated with self legating technique and review the orthodontic literature with regard to the eficiency, effectiveness, and stability of treatment with SLBs. MATERIALS AND METHODS Study design/sample To address the research purpose, the investigators designed a cohort study. The study population was composed of 18 patients (8 females and 10 males, median age 19 ± 9.2 years, min 10, max 39 years) affected by malocclusion and admitted for orthodontic treatment between January 2006 and December 2007. The median active orthodontic treatment was 20 months and the median follow-up was 26.8 ± 11.8 months, min 11, max 54 months. There were 8 class 1, 5 class 2 and 5 class 3 malocclusion, 3 cross-bites and 2 open-bite. Lateral teleradiographic projections of the cranium were used, which had been taken from a distance of 1.52 meter. The head was ixed in a cephalostat and oriented in natural position. The cephalometric analysis was performed data by using Dolphin Imaging Mc Lauglin Cephalometric Analysis (9200 Eton Avenue, Chatsworth, CA 91311-5807, USA). The following anterior dental variables were investigated: - Upper Incisor Protrusion (U1-APo) mm (distance between upper incisor and line point A to Pogonion) norm: + 6 mm st dev: 2,2 H is the difference between UIP and the standard values; - Lower Incisor Protrusion (L1-APo) mm (distance between lower incisor and line point A to Pogonion) norm: + 2 mm st dev: 2,3 K is the difference between L1-APo and the standard values; - Upper Incisor – Palatal Plane (inclination of upper incisor to palata plane) norm: + 110° st dev 5 - Upper Incisor - Occlusal Plane (U1) (inclination of upper incisor to occlusal plane ) norm: + 55° st dev :7 Y is the difference between U1 and the standard values; - Lower Incisor - Occlusal Plane (L1) (inclination of lower incisor to occlusal plane ) norm: +72° st dev: 5 Z is the difference between UIP and the standard values; - IMPA (lower incisor to mandibular plane) norm: +95° st dev: 5 X is the difference between IMPA and the standard values; In all variables the value 1 is referred to the inal follow-up value. Orthodontic treatment was performed by using 3MUnitek self-ligating system (3M Unitek Orthodontic Products 2724 South Peck Road Monrovia, CA 91016 USA). Passive self ligating brackets. Data analysis Pearson Chi Square was used to detect statistical differences in each variable between inal treatment teleradiography and last follow-up radiographic control. RESULTS Table I reports the mean value, the standard deviation and the standard error of each investigated variable. Table II reports the output of T-test for each variable. In all cased the degree of freedom was 17. Statistical signiicant differences were detected between all single variables (i.e. difference between pretreatment and post treatment cephalometric values). In addition Y and Z have positive T-test. DISCUSSION Since the mid-1970s, the search for a bracket system with a low frictional resistance resulted in a renewed interest in the development of SLBs. The term selfligation in orthodontics implies that the orthodontic bracket has the ability to engage itself to the archwire and is therefore assumed to reduce friction by eliminating the ligation force. These SLBs have a mechanical device built into the bracket to close off the edgewise slot—usually a gate or clip securing the archwire (13). The incorporation of SLBs into routine clinical practice aimed at replacing existing conventional ligation methods with elastomeric and stainless steel ligatures in order to improve clinical eficacy (14). Consistent archwire engagement throughout orthodontic treatment and elimination of the need for frequent visits for the 55 (S) European Journal of Inlammation replacement of ligatures were the main advantages listed for the new ligation mode (15). Additionally, it has been proposed that due to the bracket – wire engagement, generation of light forces and reduced friction are attained with a desirable outcome on the rate of orthodontic tooth Table I. Mean values of each investigated variables Variable Mean Standard deviation Standard error UIP UIP-1 H H-1 LIP LIP-1 K K-1 UIO UIO-1 Y Y-1 LIO LIO-1 Z Z-1 IMPA IMPA-1 .X X-1 7.38 5.81 0.63 0.01 2.39 2.52 0.15 0.24 59.87 59.23 0.7 0.61 64.86 67.62 -1.18 -0.87 93.1 93.8 -0.27 -0.17 3.29 1.84 1.50 0.84 2.66 1.67 1.16 0.73 7.15 5.23 1.02 0.75 4.76 5.70 0.86 1.16 7.23 9.62 1.03 1.38 0.78 0.43 0.35 0.20 0.63 0.39 0.27 0.17 1.68 1.23 0.24 0.18 1.12 1.34 0.2 0.27 1.71 2.27 0.24 0.32 movement (16). For a given cross-section and modulus of archwire, the magnitude of force developed during engagement may vary depending on the inter-bracket span, ligation mode, and number of teeth legated in the proximal and distal segments of the arch. This effect arises from the increased stiffness of the wire but additional factors, which modulate force magnitude, may relate to the degree of crowding, which is associated with inter-bracket distance, the relaxation of ligatures and clip modulus of elasticity, and relaxation of self-legating bracket-engaging mechanism (17), which may alter or modify the load transmitted to the teeth. Although reduced friction has been reported to be one of the advantages of SLBs (10), the issue of friction and SLBs is still controversial (10), as some studies have reported the reduction in friction with SLBs to be signiicant while others claim that SLBs produce similar or higher friction compared with CLBs (12). Most claims of SLBs have been extrapolated from in-vitro studies. However, a recent systematic review highlighted the limitations of in-vitro studies (18). In particular, studies that demonstrate reduced friction in SLBs compared with CLBs have been coupled with small-diameter wires in well-aligned arches with no tip and torque (19). In vitro studies are limited because they cannot comprehensively simulate a clinical scenario. Many variables can inluence the amount of friction generated in a ixed appliance system: archwire dimension, archwire and bracket composition, bracket slot dimension and design, inter- Table II. Output of statistical analysis Variable t Sig. Mean difference UIP UIP-1 H H-1 LIP LIP-1 K K-1 UIO UIO-1 Y Y-1 LIO LIO-1 Z Z-1 IMPA IMPA-1 X X-1 9.5 13.36 1.8 -0.45 3.8 6.4 0.55 1.4 35.55 48.1 2.9 3.4 57.85 50.32 -5.8 -3.2 54.6 41.4 -1.12 -0.53 0.001 0.001 0.09 0.66 0.001 0.001 0.6 0.19 0.001 0.001 0.01 0.003 0.001 0.001 0.001 0.005 0.001 0.001 0.28 0.6 7.38 5.81 0.63 0.01 2.39 2.52 0.15 0.24 59.87 59.23 0.7 0.61 64.86 67.62 -1.18 -0.87 93.1 93.8 -0.27 -0.17 95% conidence interval of the difference Lower Upper 5.74 9.02 4.89 6.73 -0.11 1.38 -0.51 0.33 1.06 3.7 1.68 3.35 -0.43 0.73 -0.12 0.6 56.32 63.43 56.62 61.83 0.19 1.21 0.24 0.99 62.49 67.22 64.78 70.45 -1.61 -0.7 -1.45 -0.3 89.5 96.7 89.06 98.63 -0.79 0.24 -0.86 0.51 56 (S) G.E. MANCINI ET AL. Fig. 4. The occlusion at the end of the therapy Fig. 1. Teleradiography showing the cephalometric analyses Fig. 2. Intra-oral frontal view of patient with anterior open byte Fig. 3. Dental devices during the orthodontic treatment bracket distance, delection of the archwire, and biologic factors such as saliva and perturbations. Therefore, it is questionable whether the use of SLBs translates into clinical beneits such as decreased resistance to sliding, faster tooth movement, and increased treatment eficiency (20). Several in-vivo studies reported that friction increases as wire dimension increases (21) and that frictional force is generally greater with rectangular wires than with round wires (22). A reason why rectangular wires produced an increased friction even in SLBs is that, as the bracket slot is illed, the differences between SLBs and CLBs are minimized. This is related to less tipping allowed before teeth are straightened back by the wire resilience. This cycle occurs at a faster rate with more slot play (18). Regarding differences in friction between passive and active SLBs, some controversy exists. Six of the 11 studies reported that passive brackets generated a lower level of friction compared with the active group, while 2 studies reported no differences. The remaining 3 studies did not observe a consistent trend (18). The difference in friction between passive and active SLBs have been attributed to the fact that the former group of brackets studied form a rigid tube when closed, applying no direct force to the wire (23). Other possible explanations for the results could be differences in archwires tested and diverse brackets tested. Finally, data in vivo about the eficiency of SLBs and CLBs during various stages of treatment were pooled and were compared with conlicting results. These studies measured treatment eficiency in terms of total treatment times, numbers of appointments, and tooth movement during initial alignment and active space closure. Early retrospective studies reported considerable months’ reduction in total treatment time and fewer appointments with SLBs (24). In the present study we demonstrated that SLBs are effectiveness tools to reach good clinical results since all studied variables (i.e. teeth position) have statistically signiicant differences between pre and post-treatment control. European Journal of Inlammation ACKNOWLEDGMENT This work was partially supported by by Don Orione Service s.r.l., Bergamo, Italy. 13. REFERENCES 1. Stolzenberg J. The eficiency of the Russell attachment. Am J Orthod Oral Surg 1946; 32:572-82. 2. Fansa M, Keilig L, Reimann S, Jager A, Bourauel C. The leveling effectiveness of self-ligating and conventional brackets for complex tooth malalignments. J Orofac Orthop 2009; 70:285-96. 3. Berger JL. The SPEED system: an overview of the appliance and clinical performance. Semin Orthod 2008; 14:54-63. 4. Miles PG. 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