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Case Report Leveling effects of conventional and self-ligating brackets -cases report CHIA-TZE KAO Institute of Oral Material Science and Orthodontic Department, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC. Many kinds of self-ligating brackets (SLBs) have been introduced to the market. Manufacturers claim that SLBs have many benefits, such as being fast, convenient, and frictionless. The aim of this report was to compare the teeth leveling effects of a conventional bracket (CB) and various SLBs combined with a copper-nickel-titanium wire. Each malocclusion case was bonded with 1 of the following 4 types of bracket: an Ormco Damon III bracket, a Tomy Clippy bracket, a 3K composite bracket, and a Unitek Clarity ceramic bracket. A 0.36mm (0.014-in) copper-nickel-titanium wire was initially used in all cases. The observation period was 4 months, and photographs were taken at each visit for treatment. At the end point of the observation time, the teeth of all patients which were initially crowded, malaligned, or malpositioned teeth were well aligned, and similar treatment outcomes were seen. We concluded that appliances with either the conventional or self-ligating brackets coupled with copper-nickel-titanium wire can achieve good alignment and leveling of crowded, malaligned, and malpositioned teeth in a relatively short interval of 12 weeks. (J Dent Sci, 2(2):110-126, 2007) Key words: self ligating bracket, leveling stage, conventional bracket. In recent years as orthodontic materials have improved, many hot appliances have been introduced for clinical use. Hot appliances such as application of thermal nickel-titanium (NiTi) or copper NiTi (with a low load / deflection rate) and self-ligating brackets (with low friction) are frequently used in routine orthodontic therapy. All of these products emphasize reductions in chair time and creation of high efficiency. Therefore, orthodontists may be interested in whether wires or brackets play important roles in orthodontic treatment. Self-ligating brackets were introduced in the mid-1930s in the form of the Russell attachment, which was intended to reduce ligation time and improve operator efficiency1,2. Two types of selfligating brackets have been developed: an active form Received: February 12, 2007 Accepted: April 20, 2007 Reprint requests to: Dr. Chia-Tze Kao, Orthodontic Department, College of Oral Medicine, Chung Shan Medical University, No. 110, Chien-Kuo North Road, Taichung, Taiwan 40201, ROC. 110 in which a wire is compressed in a bracket slot and a passive form in which the wire is not compressed in a bracket slot. There are many advantages with self-ligating brackets. From the patient’s perspective, self-ligating brackets are generally smoother, more comfortable, and easier to clean because of the absence of wire ligatures3. Several studies have demonstrated a significant decrease in friction with self-ligating brackets compared with conventional bracket designs4-8. Reduced chair time is another significant advantage9. However, one defect of self-ligating brackets is the high cost. In addition, by using these appliances, manufacturers claim that orthodontists can increase patient appointment intervals and increase patient loads. Stainless steel and cobalt-chromium alloys were available in the 1940s and were extensively used in orthodontics for many years. The introduction of NiTi and multistranded stainless steel wires in the 1970s, of titanium-molybdenum and superelastic NiTi in the 1980s, and of temperature-activated superelastic wires in the 1990s has provided a wider range of choices. The newest materials enable clinicians to use light J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets continuous forces to move the teeth with less discomfort to patients and less stress on the supporting tissues. Friction acts at the surface between 2 bodies when 1 body slides or tends to slide in contact with another body11,12. Friction in fixed orthodontic appliance systems is recognized by most clinicians to be very harmful to tooth movement13,14. Various factors such as the archwire and bracket materials, their sizes and shapes, the slot dimensions, the surface composition, roughness, and cleanliness affect the friction resistance process of orthodontic bracket-wire combinations. Previous studies have shown that bracket friction resistance levels from high to low are in the order of conventional ceramic brackets, conventional metal brackets, metal brackets, and self-ligating brackets15. Wire friction resistance levels from high to low are in the order of TMA wire, NiTi wire, and stainless steel wire16,17. An ideal archwire should be able to move teeth with a light, continuous force. This force should be designed to minimize patient discomfort, tissue hyalinization, and root resorption. When a force is applied, the archwire should maintain its elasticity over a period of weeks to months. A light force delivered at a constant level provides the optimal condition for tooth movement. This can best be achieved with wires that exhibit large elastic deformations before breakage and thus have a large working range. An important consideration in selecting an archwire for initial leveling in orthodontic treatment is its stiffness, i.e., the force delivered per unit of deactivation. Low-stiffness wires can be produced using conventional NiTi because the modulus of elasticity of NiTi is approximately 20% that of stainless steel18. The orthodontic force must overcome the frictional resistance (and the resistance of the biologic milieu), and minimizing friction will result in reduced levels of the required clinically applied force to move the teeth. The relationship between the bracket and wire is intimate, and a force system is the outcome. Determining how to create the best force system is a critical aspect of the entire orthodontic process. To achieve a high efficiency of orthodontic treatment, it should be determined whether it is necessary to change traditional brackets to new self-ligating brackets in all orthodontic cases. The following malocclusion cases were treated using different J Dent Sci 2007‧Vol 2‧No 2 bracket types with wires which generate similar light forces. The treatment results showed similar effects of the leveling or alignment of malpositioned teeth. CASE PRESENTATION Case 1. A non-extraction case with a selfligating bracket A 13-year-old male patient had a class III malocclusion. The maxillary dentition showed a blocking-in of the lateral incisors, canine supraversion, and midline deviation, and the mandibular dentition revealed minor incisor crowding. No tooth extraction was performed in this case. The appliance used consisted of a 0.022×0.028 inch slot Clippy metal self-ligating bracket (Tomy, Tokyo, Japan) and 0.014inch Sentalloy wire (NiTi superelastic wire, Tomy) (Figure 1A). Progressive photographs of the frontal and buccal views were taken during each visit at 4-week intervals. The leveling of the teeth was complete by the third visit (Figure 1B). Progressive photographs of the occlusal view were also taken during each visit. On the third visit, decrowding of the teeth had been achieved (Figure 1C). Case 2. An extraction case with a self-ligating bracket This 22-year-old female patient had a class I malocclusion and an anterior openbite of 3 mm. The maxillary dentition exhibited minor crowding of the anterior teeth and a deep curve of Spee, and the mandibular dentition demonstrated minor crowding of the anterior teeth. The treatment plan for this case included extraction of the 4 first premolars. The appliance used consisted of a 0.022×0.028 inch slot Clippy metal self-ligating bracket and a 0.014 inch Sentalloy wire (Figure 2A). Progressive photographs of the frontal and buccal views were taken at each visit at 4-week intervals. On the third visit, the alignment of teeth was complete, and the amount of openbite had decreased (Figure 2B). Progressive photographs of the occlusal view were also taken during each visit. On the third visit, the arch form had changed from square to rounded ovoid (Figure 2C). 111 C.T. Kao Case 3. A non-extraction case with a selfligating bracket Case 5. A non-extraction case with a composite metal slot bracket treatment This 23-year-old female patient had a class III malocclusion. The occlusion of the dentition showed blocking-in of the right upper lateral incisor, a midline shift to the right, an anterior crossbite, and minor crowding of the lower teeth. No tooth extraction was performed in this case. The appliance used consisted of a 0.022 × 0.028 inch slot Damon III metal self-ligating bracket (Ormco, Glandora, CA, USA) and a 0.014 inch copper NiTi wire (Ormco) (Figure 3A). Progressive photographs of the frontal and buccal views were taken during each visit at 4-week intervals. The right upper lateral incisor did not bond with the bracket until the third visit. At that stage, the anterior crossbite was corrected, and the midline showed a little shift (Figure 3B). On the sixth visit, the blocked-in right upper lateral incisor had been pulled out and was aligned in the correct position (Figure 3C). Progressive photographs of the occlusal view were also taken at each visit. On the third visit, the lower arch alignment was complete, but the right upper lateral incisor was still in a blocked-in position (Figure 3D). The lower arch alignment was the same as that of the third visit, but the right upper lateral incisor had been pulled out at the sixth visit (Figure 3E). This 21-year-old female patient had a class I malocclusion. The maxillary incisors were rotated and mandibular incisors were crowded. No tooth extraction was performed in this case. The appliance used consisted of a 0.022×0.028 inch slot composite metal slot bracket (3K Dentsply, New York, NY, USA) and a 0.014 inch Sentalloy wire (Figure 5A). Progressive photographs of the frontal and buccal views were taken at each visit at 4-week intervals. In the frontal view, the crowding of the lower incisors had been relieved by the third visit, and the gingival recession had been auto-corrected (Figure 5B). Progressive photographs of the occlusal view were also taken at each visit. On the third visit, both the maxillary and mandible arch alignments were good (Figure 5C). Case 4. An extraction case with a self-ligating bracket This 21-year-old female patient had a class I malocclusion. The right and left maxillary lateral incisors were blocked-in. Both maxillary and mandibular arches showed tooth crowding with a deep curve of Spee. Four first premolars were extracted. The appliance used consisted of a 0.022×0.028 inch slot Damon III metal self-ligating bracket and 0.014 inch copper NiTi wire. On the third visit, the blocked-in lateral incisors had been pulled out, and the tooth alignment was complete (Figure 4A). Progressive photographs of the occlusal view were taken at each visit. On the third visit, the maxillary arch form had changed from a V shape to a rounded ovoid one, and the transverse width of the premolar area had increased. By the third visit, the tooth crowding was relieved (Figure 4B). 112 Case 6. An extraction case with composite metal slot bracket treatment This 25-year-old female patient had a class III malocclusion. The maxillary dentition showed an anterior crossbite with blocking-in of the lateral incisors and a midline deviation. The left maxillary first premolar and the right and left mandibular first premolars were extracted. The appliance used consisted of a 0.022 × 0.028 inch slot composite metal slot bracket and a 0.014-inch Sentalloy wire (Figure 6A). Progressive photographs of the frontal and buccal views were taken at each visit at 4-week intervals. In the frontal view, the blocked-in upper lateral incisors had been pulled out. In the buccal view, the canine had been pulled down to the occlusal plane. The anterior teeth had achieved an edge-to-edge relationship(Figure 6B). Progressive photographs of the occlusal view were also taken at each visit. On the third visit, the maxillary arch form exhibited good alignment, and the extraction space had been reduced (Figure 6C). Case 7. A non-extraction case with ceramic metal slot bracket treatment This 23-year-old female patient had a class I malocclusion. The right maxillary central and lateral J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets incisors exhibited a crossbite with minor crowding. The patient asked for alignment and leveling of the maxillary teeth only. No tooth was extracted. The appliance used consisted of a 0.022×0.028 inch slot ceramic metal slot bracket (Clarity, 3M Unitek, Monrovia, CA, USA) and a 0.014-inch Sentalloy wire (Figure 7A). Progressive photographs of the frontal and buccal views were taken at each visit at 4-week intervals. On the first visit, the right maxillary central and lateral incisors were well aligned. The teeth alignment was improving through the third visit (Figure 7B). Progressive photographs of the occlusal view were also taken at each visit. By the third visit, the arch form had changed to a more-rounded ovoid shape (Figure 7C). Case 8. An extraction case with ceramic metal slot bracket treatment This 25-year-old female patient had class I malocclusion. The maxillary lateral incisors were blocked-out, and the central incisors showed a lingual tip. No tooth extraction was done in this case. The appliance used consisted of a 0.022×0.028 inch slot ceramic metal slot bracket and a 0.014 inch Sentalloy wire (Figure 8A). Progressive photographs of the frontal, buccal, and occlusal views were taken at each visit at 4-week intervals. On the third visit, the maxillary incisors were well aligned, but the buccal occlusion was a little disoriented. On the occlusal view, the arch form had changed to a more-rounded shape (Figure 8B). DISCUSSION Many factors can influence orthodontic frictional resistance, including the relative resistance between the bracket and wire, the archwire size, the archwire section, the torque at the bracket wire interface, the surface condition of the archwire and bracket slot, and the type and force of the liagtion19-21. Friction force is known to be an important factor that might affect the treatment efficiency. It is more common to use the self-ligating bracket in the clinic because many manufacturers offer different types of self-ligating brackets. According to the manufacturer’s description of the J Dent Sci 2007‧Vol 2‧No 2 self-ligating bracket, elimination of the ligatures reduces friction and allows for better sliding mechanics22. These reports support a view of clinically significant improvements in treatment efficiency when using passive self-ligating brackets22. In Eberting’s study22, it is not clear as to what kinds of technique were used or which variables were controlled. However, in the present reported 8 cases, one can observe that the treatment time did not decrease in the initial stage of treatment when using the self-ligating brackets. Appliances with either conventional or self-ligating brackets can achieve good alignment of the teeth after 4 months of treatment. On the contrary, different wires might have different efficiencies for teeth movement. Miles’s study showed that the Smart Clip bracket was not more effective at reducing irregularities during the initial stage of treatment than a conventional bracket ligated with elastomeric modules or stainless steel ligatures23. This result is comparable with the results from the present case reports. The efficiencies of self-ligating brackets need to be surveyed or studied in an evidence-based clinical study. One may question whether the high efficiency of tooth movement that is time-saving and exists with self-ligating brackets occurs in the space closure stage. Unfortunately, there is a lack of clinical data to demonstrate this. However, different extraction rates may simply reflect different approaches to treatment. Eberting showed that the treatment time was not reduced when using a Damon self-ligating bracket22. This supports the concept that the reduction in treatment time may be due to a change to moreefficient treatment systems rather than solely to the choice of a bracket. The orthodontist’s concepts still play a most important role in tooth movement. Although this is not a clinical study, the treatment outcomes of our 8 cases showed that all crowded, malaligned, and malpositioned teeth could be well aligned or leveled in a relatively short interval of 12 weeks. Although the frictional resistance of the self-ligating bracket is lower than that of the traditional bracket, no significant difference in the clinical outcomes was found when using either type of bracket. The teeth movement efficiency was also similar. It is also believed that the wire creating a light force should be used when performing tooth movement. 113 C.T. Kao Figure 1. Case 1, a non-extraction case with a self-ligating bracket. 114 J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets Fig. 1C. Figure 1.(continued) Figure 2. Case 2, an extraction case with a self-ligating bracket. J Dent Sci 2007‧Vol 2‧No 2 115 C.T. Kao Fig. 2C. Figure 2. (continued) 116 J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets Fig. 3A. Figure 3. Case 3, a non-extraction case with a self-ligating bracket. J Dent Sci 2007‧Vol 2‧No 2 117 C.T. Kao Fig. 3D. Figure 3. (continued) 118 J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets Fig. 3E. Figure 3. (continued) Figure 4. Case 4, an extraction case with a self-ligating bracket. J Dent Sci 2007‧Vol 2‧No 2 119 C.T. Kao Figure 4. (continued) Figure 5. 120 Case 5, a non-extraction case with composite metal slot bracket treatment. J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets Figure 5. (continued) J Dent Sci 2007‧Vol 2‧No 2 121 C.T. Kao Fig. 6A. Figure 6. Case 6, an extraction case with composite metal slot bracket treatment. 122 J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets Fig. 6C. Figure 6. (continued) Figure 7. Case 7, a non-extraction case with ceramic metal slot bracket treatment. J Dent Sci 2007‧Vol 2‧No 2 123 C.T. Kao Figure 7. (continued) 124 J Dent Sci 2007‧Vol 2‧No 2 Ligating brackets Figure 8. J Dent Sci 2007‧Vol 2‧No 2 Case 8, an extraction case with ceramic metal slot bracket treatment. 125 C.T. Kao REFERENCES 1. Stolzenberg J. The Russell attachment and its improved advantages. Int J Orthod Dent Child, 21: 837-840, 1935 2. Stolzenberg J. The efficiency of the Russell attachment. Am J Orthod Oral Surg, 32: 572-582, 1946. 3. Shivapuja PK, Berger JL. A comparative study of conventional ligation and self-ligation bracket systems. Am J Orthod Dentofacial Orthop, 106: 472-480, 1994. 4. Read-Ward GE, Jones SP, Davies EH. A comparison of selfligating and conventional orthodontic bracket systems. Br J Orthod, 24: 309-317, 1997. 5. Thomas S, Sherriff M, Birnie D. A comparative in vitro study of the frictional characteristics of two types of self-ligating brackets and two types of pre-adjusted edgewise brackets tied with elastomeric ligatures. Eur J Orthod, 20: 589-596, 1998. 6. Thorstenson GA, Kusy RP. 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Angle Orthod, 66: 215-222, 1996. 22. Eberting JJ, Straja SR, Tuncay OC. Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets. Clin Orhtod Res, 4: 228-234, 2001. 23. Miles PG. SmartClip versus conventional twin brackets for initial alignment: is there a difference. Aust Orthod, 21: 123-127, 2005. J Dent Sci 2007‧Vol 2‧No 2