Comparison of force loss due to friction of different wire sizes and materials in conventional and new self-ligating orthodontic brackets during simulated canine retraction.

AIMS: The aim of this study was to compare force loss due to friction (Fr) during simulated canine retraction using different archwire dimensions and materials between conventional and new self-ligating brackets. METHODS: The tested brackets were (1) conventional brackets (Victory series, GAC twin and FLI twin), (2) self-ligating brackets (Damon-Q, FLI-SL, new/improved FLI-SL (I FLI-SL), SPEED, GAC innovation (R) and Ortho Classic) and (3) a low-friction bracket (Synergy). All brackets had a 0.022″ slot size. The tested archwires were stainless steel (0.018″; 0.016″x0.022″; 0.017″x0.025″; 0.018″x0.025″ and 0.019″x0.025″); nickel titanium (NiTi; 0.016″x0.022″; 0.017″x0.025″; 0.018″x0.025″ and 0.019″x0.025″) and titanium molybdenum alloy (TMA; 0.016″x0.022″; 0.017″x0.025″; 0.018″x0.025″ and 0.019″x0.025″). Canine retraction was experimentally simulated in a biomechanical set-up using a NiTi coil spring that delivered a force of 1 N. The simulated retraction path was up to 4 mm. Force loss due to friction was compared between groups using the Welch t­test. RESULTS: Force loss due to friction increased with increasing archwire size. Also, TMA showed the highest and stainless steel the lowest force loss due to friction. FLI-SL brackets showed the lowest Fr (31%) and Ortho Classic showed the highest (67%). CONCLUSIONS: Increasing wire size generally showed increasing force loss due to friction. FLI-SL brackets showed the lowest, while Ortho Classic showed the highest friction.

Comparison of the efficacy of tooth alignment among lingual and labial brackets: an in vitro study.

Background/objective: The aim of this study was to evaluate the efficacy of tooth alignment with conventional and self-ligating labial and lingual orthodontic bracket systems. Materials/methods: We tested labial brackets (0.022″ slot size) and lingual brackets (0.018″ slot size). The labial brackets were: (i) regular twin brackets (GAC-Twin [Dentsply]), (ii) passive self-ligating brackets including (Damon-Q® [ORMCO]; Ortho classic H4™ [Orthoclassic]; FLI®SL [RMO]), and (iii) active self-ligating brackets (GAC In-Ovation®C [DENTSPLY] and SPEED™[Strite]). The lingual brackets included (i) twin bracket systems (Incognito [3M] and Joy™ [Adenta]), (ii) passive self-ligating bracket system (GAC In-Ovation®LM™ [Dentsply]), and (iii) active self-ligating bracket system (Evolution SLT [Adenta]). The tested wires were Thermalloy-NiTi 0.013″ and 0.014″ (RMO). The archwires were tied to the regular twin brackets with stainless steel ligatures 0.010″ (RMO). The malocclusion simulated a displaced maxillary central incisor in the x-axis (2 mm gingivally) and in the z-axis (2 mm labially). Results: The results showed that lingual brackets are less efficient in aligning teeth when compared with labial brackets in general. The vertical correction achieved by labial bracket systems ranged from 72 to 95 per cent with 13″ Thermalloy wires and from 70 to 87 per cent with 14″ Thermalloy wires. In contrast, the achieved corrections by lingual brackets with 13″ Thermalloy wires ranged between 25-44 per cent and 29-52 per cent for the 14" Thermalloy wires. The anteroposterior correction achieved by labial brackets ranged between 83 and 138 per cent for the 13″ Thermalloy and between 82 and 129 per cent for the 14″ Thermalloy wires. On the other hand, lingual brackets corrections ranged between 12 and 40 per cent for the 13″ Thermalloy wires and between 30 and 45 per cent for the 14″ Thermalloy wires. Limitation: This is a lab-based study with different labial and lingual bracket slot sizes (however they are the commonly used ones in clinical orthodontics) and study did not consider saliva, periodontal ligament, mastication and other oral functions. Conclusions: The effectiveness of lingual brackets in correcting vertical and anteroposterior displacement achieved during the initial alignment phase of orthodontic treatment is lower than that of the effectiveness of labial brackets.

Comparison of the force levels among labial and lingual self-ligating and conventional brackets in simulated misaligned teeth.

BACKGROUND/OBJECTIVE: The aim of this study was to evaluate force levels exerted by levelling arch wires with labial and lingual conventional and self-ligating brackets. MATERIALS/METHODS: The tested orthodontic brackets were of the 0.022-in slot size for labial and 0.018-in for lingual brackets and were as follows: 1. Labial brackets: (i) conventional bracket (GAC-Twin, Dentsply), (ii) passive self-ligating (SL) brackets (Damon-Q®, ORMCO; Ortho classic H4™, Orthoclassic; FLI®SL, Rocky Mountain Orthodontics) and (iii) active SL brackets (GAC In-Ovation®C, DENTSPLY and SPEED™, Strite). 2. Lingual brackets: (i) conventional brackets (Incognito, 3M and Joy™, Adenta); (ii) passive SL bracket (GAC In-Ovation®LM™, Dentsply and (iii) active SL bracket (Evolution SLT, Adenta). Thermalloy-NiTi 0.013-in and 0.014-in arch wires (Rocky Mountain Orthodontics) were used with all brackets. The simulated malocclusion represented a maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis). RESULTS: Lingual bracket systems showed higher force levels (2.4 ± 0.2 to 3.8 ± 0.2 N) compared to labial bracket systems (from 1.1 ± 0.1 to 2.2 ± 0.4 N). However, the differences between SL and conventional bracket systems were minor and not consistent (labial brackets: 1.2 ± 0.1 N for the GAC Twin and 1.1 ± 0.1 to 1.6 ± 0.1 N for the SL brackets with 0.013-in thermalloy; lingual brackets: 2.5 ± 0.2 to 3.5 ± 0.1 N for the conventional and 2.7 ± 0.3 to 3.4 ± 0.1 N for the SL brackets with 0.013-in Thermalloy). LIMITATIONS: This is an in vitro study with different slot sizes in the labial and lingual bracket systems, results should be interpreted with caution. CONCLUSIONS/IMPLICATIONS: Lingual bracket systems showed higher forces compared to labial bracket systems that might be of clinical concern. We recommend highly flexible nickel titanium arch wires lower than 0.013-in for the initial levelling and alignment especially with lingual appliances.

Mechanical properties of different esthetic and conventional orthodontic wires in bending tests : An in vitro study.

AIMS: The goal of this study was to determine the mechanical properties of different esthetic and conventional orthodontic wires in three-point and four-point bending tests, and in a biomechanical test employing three bracket systems. METHODS: The behavior of round wires with a diameter of 0.46 mm (0.018″) were investigated: uncoated nickel titanium (NiTi) wires, surface modified NiTi wires; FLI® Orthonol Wire® and glass fiber reinforced plastic wires. The biomechanical bending test was performed using the following bracket types: metal brackets (Discovery®, Dentaurum), ceramic brackets (Fascination®, Dentaurum), and plastic brackets (Elegance®, Dentaurum). All bending tests were performed in the orthodontic measurement and simulation system (OMSS) at a temperature of 37 °C. The classical three-point bending test was performed according to an ISO standard (DIN EN ISO 15841:2007) using the appropriate thrust die and supports with a predefined span of 10 mm. In the other tests the supports or interbracket distances were chosen such that the free wire length was also 10 mm (5 mm between adjacent brackets). All wires were loaded centrally to a maximum of 3.1 and 3.3 mm in the biomechanical test, respectively. The force was measured upon unloading with a loading velocity of 1 mm/min. Each specimen was loaded twice and a total of 10 specimens tested for each product. Weighted means and the error of the weighted mean were calculated for each product. RESULTS: Fiber reinforced wires displayed lowest forces in three-point bending with values of 0.4 N at a displacement of 1 mm and 0.7 N at a 2 mm displacement. In four-point bending the forces were 0.9 N and 1.4 N, respectively, at the same displacements. Almost all of the translucent wires showed fracture upon bending at displacements greater than 3 mm, independent of the bending test and bracket type. The different investigated NiTi wires, surface modified or conventional, only showed minor variation, e.g., 2.2 N for rematitan® Lite White and 2.0 N for rematitan®, 2.1 N for FLI® Coated Orthonol® and 1.7 N for Orthonol® in four-point bending. The rhodinized wire generated forces between these values (2.1 N). CONCLUSION: The translucent wires had the lowest forces in all three bending tests; however, displacements above 3 mm resulted in increased risk of fracture. Forces of investigated NiTi wires were very high and in part above clinically recommended values.

Study of force loss due to friction comparing two ceramic brackets during sliding tooth movement.

OBJECTIVE: To compare the percentage of force loss generated during canine sliding movements in newly introduced ceramic brackets with metal brackets. MATERIALS AND METHODS: Two types of ceramic brackets, namely polycrystalline alumina (PCA) ceramic brackets (Clarity Advanced) and monocrystalline alumina (MCA) ceramic brackets (Inspire Ice) were compared with stainless steel (SS) brackets (Victory Series). All bracket groups (n = 5 each) were for the maxillary canines and had a 0.018-inch slot size. The brackets were mounted on an Orthodontic Measurement and Simulation System (OMSS) to simulate the canine retraction movement into the first premolar extraction space. Using elastic ligatures, 0.016 × 0.022″ (0.40 × 0.56 mm) stainless steel archwires were ligated onto the brackets. Retraction force was applied via a nickel-titanium coil spring with a nearly constant force of approximately 1 N. The OMSS measured the percentage of force loss over the retraction path by referring to the difference between the applied retraction force and actual force acting on each bracket. Between group comparisons were done with one-way analysis of variance. RESULTS: The metal brackets revealed the lowest percentage of force loss due to friction, followed by the PCA and MCA ceramic bracket groups (67 ± 4, 68 ± 7, and 76 ± 3 %, respectively). There was no significant difference between SS and PCA brackets (p = 0.97), but we did observe significant differences between metal and MCA brackets (p = 0.03) and between PCA and MCA ceramic brackets (p = 0.04). CONCLUSION: PCA ceramic brackets, whose slot surface is covered with an yttria-stabilized zirconia-based coating exhibited frictional properties similar to those of metal brackets. Frictional resistance resulted in an over 60 % loss of the applied force due to the use of elastic ligatures.

Mechanical properties of cobalt-chromium wires compared to stainless steel and ß-titanium wires.

BACKGROUND: Previous studies have reported on mechanical properties of different orthodontic wires. However, there is a paucity of information that comparing the mechanical properties of Blue Elgiloy (BE) when compared to stainless steel and TMA, as finishing wires as received by different companies. AIMS: The aim of this study was to evaluate the mechanical properties of BE wires compared to stainless steel (SS) and titanium Molybdenum alloy (TMA) also known as ß titanium as provided by two companies. MATERIALS AND METHODS: Six 0.016 x 0.022-14mm-samples of each wire were fixed individually to Instron machine and were tested in loading and unloading for three times. The initial load was set for 500 Kg at a speed of 1mm/min and displacement was adjusted for (0.5, 1mm in loading and 0.5 mm unloading at 25°C). STATISTICS ANALYSIS: Variables were compared between groups by ANOVA test using SPSS statistical software. RESULTS: BE shows comparable forces to SS when loaded 0.5 and showed decreased forces in 1mm loading compared to SS, and higher than TMA. BE also showed no forces at unloading and high deformation. CONCLUSION: BE from the two companies showed comparable mechanical properties while SS and TMA were different. The deformation of BE and its decreased forces in unloading may limit its clinical use.