BACKGROUND It has been demonstrated that fluoride prophylactic agents may cause hydrogen absorption in NiTi wires and degrade their mechanical properties. AIMS To investigate the effect of a fluoride mouthwash on load-deflection characteristics of three types of nickel-titanium-based orthodontic archwires. METHODS Twenty maxillary 0.016 inch round specimens from each of the single-strand NiTi (Rematitan 'Lite'), multi-strand NiTi (SPEED Supercable) and Copper NiTi (Damon Copper NiTi) wires were selected. The specimens were kept in either 0.2% NaF or artificial saliva solutions at 37 degrees C for 24 hours (N = 10). The wire load-deflection properties were measured by a Zwick testing machine, using a three-point bending test. An un-paired student's t-test, a one-way ANOVA and a Tukey post-hoc test were used to assess statistical significance. RESULTS Immersion in NaF solution affected the load-deflection properties of NiTi wires. The unloading forces at 0.5 and 1.0 mm deflections were significantly lower in fluoride-treated specimens compared with the control groups (p < 0.05). Unloading forces at 1.5, 2.0 and 2.5 mm deflections were not statistically different between fluoride- and saliva-treated specimens (p > 0.05). CONCLUSIONS The results suggested that subjecting NiTi wires to fluoride agents decreased associated unloading forces, especially at lower deflections, and may result in delayed tooth alignment.

Aim: Various alternatives to metal orthodontic archwires have produced varied successes over the years. This study sought to evaluate the bending properties of fiber-reinforced polymeric composite (FRC) archwires compared with similarly sized nickel-titanium (Ni-Ti) archwires. Methods: Two different 0.018-inch translucent FRC orthodontic wires (Translucent Archwire I and Translucent Archwire II) were tested against 0.014-, 0.016-, and 0.018-inch nonsuperelastic nickel titanium orthodontic wires. The wires in each group (n = 10) were evaluated with three-point bending using a universal testing machine. Wire segments were deflected at midspan to 3.1 mm at a rate of 2 mm/min. Loading and unloading slope and modulus were calculated, as were force values during activation and deactivation and elastic recovery. Results: It was found that the 0.018-inch Ni-Ti archwire demonstrated the highest force values at different deflection distances followed by Translucent Archwire II, 0.016-inch Ni-Ti, Translucent Archwire I, and finally 0.014-inch Ni-Ti. 0.016-inch Ni-Ti exhibited the highest modulus value, followed by 0.018-inch Ni-Ti, 0.014-inch Ni-Ti, Translucent Archwire II, and finally Translucent Archwire I. During deactivation, the elastic recovery of 0.014-inch Ni-Ti and 0.016-inch Ni-Ti was significantly greater than Translucent Archwire II. Conclusion: The bending properties of BioMer's FRC archwires were found to be comparable to Ni-Ti, as advertised by the manufacturer.

Aim: Although much imaging research has focused on the localization and management of the impacted canines, optimal biomechanics for successful recovery are not clear. The purpose of this research was to delineate the three-dimensional (3D) effects of a single force applied using a Kilroy spring on a palatally impacted maxillary canine positioned at different angulations (5 to 40 degrees) with respect to the line of force application. Methods: A dentoform cast was modified to simulate a palatally impacted canine. Load cells placed in the dentoform simultaneously measured the three forces (Fx, Fy, and Fz) and three moments (Mx, My, and Mz) on the canine. The activation range and force system attenuation were measured for eight different positions of a palatally impacted canine (5 to 40 degrees) as the canine moves toward the occlusal plane. The results were analyzed statistically. Results: The minimum activation range for the Kilroy spring was 11 mm, and the maximum was 14 mm. At all the different impacted canine positions, the Kilroy spring had a low load deflection rate and did not require reactivation for the successful management of a palatally impacted maxillary canine. Conclusion: A 3D force system at different bracket angulations (ie, different positions of the impacted maxillary canine) can be successfully quantified using the orthodontic force transducer. Quantification of the force system provides critical information for appropriate selection of an optimal appliance.

Abstract Objective: To compare the deflection load characteristics of homogeneous and heterogeneous joints made by laser welding using various types of orthodontic wires. Materials and Methods: Four kinds of straight orthodontic rectangular wires (0.017 inch × 0.025 inch) were used: stainless-steel (SS), cobalt-chromium-nickel (Co-Cr-Ni), beta-titanium alloy (β-Ti), and nickel-titanium (Ni-Ti). Homogeneous and heterogeneous end-to-end joints (12 mm long each) were made by Nd:YAG laser welding. Two types of welding methods were used: two-point welding and four-point welding. Nonwelded wires were also used as a control. Deflection load (N) was measured by conducting the three-point bending test. The data (n  =  5) were statistically analyzed using analysis of variance/Tukey test (P <.05). Results: The deflection loads for control wires measured were as follows: SS: 21.7 ± 0.8 N; Co-Cr-Ni: 20.0 ± 0.3 N; β-Ti: 13.9 ± 1.3 N; and Ni-Ti: 6.6 ± 0.4 N. All of the homogeneously welded specimens showed lower deflection loads compared to corresponding control wires and exhibited higher deflection loads compared to heterogeneously welded combinations. For homogeneous combinations, Co-Cr-Ni/Co-Cr-Ni showed a significantly (P <.05) higher deflection load than those of the remaining homogeneously welded groups. In heterogeneous combinations, SS/Co-Cr-Ni and β-Ti/Ni-Ti showed higher deflection loads than those of the remaining heterogeneously welded combinations (significantly higher for SS/Co-Cr-Ni). Significance (P <.01) was shown for the interaction between the two factors (materials combination and welding method). However, no significant difference in deflection load was found between four-point and two-point welding in each homogeneous or heterogeneous combination. Conclusion: Heterogeneously laser-welded SS/Co-Cr-Ni and β-Ti/Ni-Ti wires provide a deflection load that is comparable to that of homogeneously welded orthodontic wires.

The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel-titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A three-point bending test was carried out to evaluate the load-deflection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and deflections of 2 and 4 mm.Analysis of variance showed that thermal NiTi wires exerted significantly lower working forces than superelastic wires of the same size in all experimental tests (P < 0.05). Wire size had a significant effect on the forces produced: with an increase in archwire dimension, the released strength increased for both thermal and superelastic wires. Superelastic wires showed, at a deflection of 2 mm, narrow and steep hysteresis curves in comparison with the corresponding thermal wires, which presented a wide interval between loading and unloading forces. During unloading at 4 mm of deflection, all wires showed curves with a wider plateau when compared with 2 mm deflection. Such a difference for the superelastic wires was caused by the martensite stress induced at higher deformation levels.A comprehensive understanding of mechanical characteristics of orthodontic wires is essential and selection should be undertaken in accordance with the behaviour of the different wires. It is also necessary to take into account the biomechanics used. In low-friction mechanics, thermal NiTi wires are to be preferred to superelastic wires, during the alignment phase due to their lower working forces. In conventional straightwire mechanics, a low force archwire would be unable to overcome the resistance to sliding.

Abstract Objective: To clinically evaluate the alignment efficiency of 0.016-inch coaxial superelastic nickel-titanium (NiTi) and 0.016-inch superelastic NiTi in the lower anterior region over a period of 12 weeks. Materials and Methods: A sample of 24 patients requiring lower anterior alignment were included in this single-center, single-operator, double-blind clinical trial and were randomly allocated into two groups of 12 patients. The type of wire selected for each patient was not disclosed to the provider or to the patient. Comparison of pretreatment characteristics of the archwire groups revealed no discrimination between two samples, thus verifying the random allocation of the intervention. An initial alginate impression of the lower arch was followed by impressions at 4-, 8-, and 12-week intervals. Casts were measured using the coordinate measuring machine to denote the degree of alignment. Duplicate readings of the cast series were taken to assess measurement variation. Results: A statistically significant difference (P <.05) in the mean values of tooth movement demonstrated the superior aligning efficiency of coaxial superelastic NiTi over single-stranded superelastic NiTi in relieving lower anterior crowding. The measurement error recorded was within acceptable limits, with range values within 95% limits of agreement. Conclusion: Coaxial superelastic NiTi wire proved superior to single-stranded NiTi in its efficiency in relieving lower anterior crowding over a 12-week period.

Nickel-titanium (NiTi) shape-memory alloys (SMAs) have been used in the manufacture of orthodontic wires due to their shape memory properties, super-elasticity, high ductility, and resistance to corrosion. SMAs have greater strength and lower modulus of elasticity when compared with stainless steel alloys. The pseudoelastic behavior of NiTi wires means that on unloading they return to their original shape by delivering light continuous forces over a wider range of deformation which is claimed to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA.

Abstract Objectives: To investigate and compare the characteristics of commonly used types of traditional and heat-activated initial archwire by plotting their load/deflection graphs and quantifying three suitable parameters describing the discharge plateau phase. Materials and Methods: Forty-eight archwires (22 nickel titanium [NiTi] and 26 heat-activated) of cross-sectional diameter ranging from 0.010 to 0.016 inch were obtained from seven different manufacturers. A modified three-point wire-bending test was performed on three analogous samples of each type of archwire at a constant temperature (37.0°C). For each resulting load/deflection curve, the plateau section was isolated, along with the mean value of the average plateau force, the plateau length, and the plateau slope for each type of wire obtained. Results: Statistically significant differences were found between almost all wires for the three parameters considered. Statistically significant differences were also found between traditional and heat-activated archwires, the latter of which generated longer plateaus and lighter average forces. The increase in average force seen with increasing diameter tended to be rather stable, although some differences were noted between traditional and heat-activated wires. Conclusions: Although great variation was seen in the plateau behavior, heat-activated versions appear to generate lighter forces over greater deflection plateaus. On average, the increase in plateau force was roughly 50% when the diameter was increased by 0.002 inch (from 0.012 to 0.014 and from 0.014 to 0.016 inch) and about 150% when the diameter was increased by 0.004 inch (from 0.012 to 0.016), with differences between traditional and heat-activated wires noted in this case.

OBJECTIVE To experimentally quantify the effects of the loop design on three-dimensional orthodontic load systems of two types of commercial closing loop archwires: Teardrop and Keyhole. MATERIALS AND METHODS An orthodontic force tester and custom-made dentoform were used to measure the load systems produced on two teeth during simulated space closure. The system included three force components along and three moment components about three clinically defined axes on two target teeth: the left maxillary canine and the lateral incisor. The archwires were attached to the dentoform and were activated following a standard clinical procedure. RESULTS The resulting six load components produced by the two archwires were reported and compared. The results were also compared with those of the T-loop archwire published previously. CONCLUSIONS The three designs deliver similar loading patterns; however, the component magnitudes are dependent on the design. All of the designs result in lingual tipping of the teeth, canine lingual-mesial displacement, canine crown-mesial-in rotation, and incisor crown-distal-in rotation.

The purpose of this study was to evaluate and compare the force levels of aesthetic Ni-Ti wires to regular Ni-Ti wires of the same dimension and evaluate their mechanical properties. Aesthetic and regular maxillary superelastic Ni-Ti wires (0.016 × 0.022) from four different manufacturers (G&H Wire Company, TP Orthodontics, GAC International, and Ortho Organizers) were selected and grouped I-IV. The loading and unloading values were compared using a three-point bending test. The unloading end values were also recorded to evaluate the recovery of archwires after each deflection. The unloading values were recorded at 0.5, 1.5, and 2.5 mm after loading deflections of 1, 2, and 3 mm, respectively. Cross-sectional scanning electron microscopy was used to assess the coating thickness of aesthetic wires. The results, statistically analysed, showed a significant decrease in force values for the aesthetic wires in groups I, III, and IV (P < 0.001) as compared to regular Ni-Ti wires of the same dimension from the same manufacturer. There was no significant difference in force values for group II wires. A statistically significant decrease in force values of epoxy-coated wires was observed in groups I, III, and IV only. This is of obvious clinical significance during wire selection. The group II coated wires, however, exhibited forces comparable to their regular Ni-ti wires with a difference that was statistically insignificant. The end values of aesthetic wires showed almost complete recovery for groups I, II, and III after 2 and 3 mm deflections.

In the mid 1970s, Schudy and Schudy developed and described an edgewise bimetric system in which there were brackets with 0.016-inch slots on the incisors and canines and brackets with 0.022-inch slots on the premolars and molars. Modeling after Schudy and Schudy, Gianelly devised a similar, preadjusted system called the bidimensional system, in which the incisor brackets have 0.018-inch slots while the remaining teeth have brackets with 0.022-inch slots. We have further modified the bidimensional system and developed a dual-slot system. Hence, this article compares the bidimensional and dual-slot systems and provides justification for both. The main concerns regarding the bidimensional and dual-slot systems are posterior "play" and lack of three-dimensional control. We rationalize both as well as the self-ligating hybrid and dual-slot system. Orthodontics (Chic);12:10-21.

OBJECTIVE To better understand the mechanics of bracket/archwire interaction through analysis of force and couple distribution along the maxillary arch. MATERIALS AND METHODS An orthodontic simulator was utilized to study high canine malocclusion. Force/couple distributions, referenced to the center of resistance (CR) of each tooth, produced by passive ligation brackets and round wire were measured. Tests were repeated for 12 bracket sets with 12 wires per set. RESULTS Propagation of the force/couple systems around the arch was minimal. Binding was observed only on the teeth adjacent to the displaced canine. For most of the teeth, reduced resistance to sliding of the passive ligation bracket yielded minimal tangential and normal forces at the bracket and contributed to lower moments at CR. CONCLUSIONS Some potential mechanical advantages of passive ligation systems are suggested for the case studied. In particular, limited propagation around the arch reduces the occurrence of unwanted force/couple systems.

OBJECTIVE To better understand the mechanics of bracket/archwire interaction through analysis of force and couple distribution along the maxillary arch using elastic ligation and to compare these results with passive ligation. MATERIALS AND METHODS An orthodontic simulator was used to study a high canine malocclusion. Force and couple distributions produced by elastic ligation and round wire were measured. Forces and couples were referenced to the center of resistance of each tooth. Tests were repeated for 12 bracket sets with 12 wires per set. Data were compared with those derived from similar tests for passive ligation. RESULTS Propagation of the force/couple systems around the arch using elastic ligation was extensive. Elastic ligation produced significantly more resistance to sliding, contributing to higher forces and couples at the center of resistance than were observed for passive ligation. CONCLUSIONS The results of this study suggest some potential mechanical advantages of passive over elastic ligation. In particular, limited propagation around the arch in passive ligation reduces the occurrence of unwanted force/couple systems compared with elastic ligation. These advantages may not transfer to a clinical setting because of the conditions of the tests; additional testing would be required to determine whether these advantages can be generalized.

Measuring the three-dimensional (3D) force-moment (F/M) systems applied for correcting tooth malposition is highly desirable for accurate spatial control of tooth movement and for reducing traumatic side effects such as irreversible root resorption. To date, suitable tools for monitoring the applied F/M system during therapy are lacking. We have previously introduced a true-scale orthodontic bracket with an integrated microelectronic stress sensor system for 3D F/M measurements on individual teeth with a perspective for clinical application. The underlying theoretical concept assumes a linear correlation between externally applied F/M systems and mechanical stresses induced within the smart bracket. However, in combined applications of F/M components the actual wire-bracket contacts may differ from those caused by separate applications of corresponding individual F/M components, thus violating the principle of linear superposition of mechanical stresses. This study systematically evaluates this aspect using finite element (FE) simulations and measurements with a real smart bracket. The FE analysis indicated that variability in the wire-bracket contacts is a major source for measurement errors. By taking the critical F/M combinations into account in the calibration of the real smart bracket, we were able to reduce the mean measurement error in five of the six F/M components to values <0.12 N and <0.04 N cm. Bucco-lingually directed forces still showed mean errors up to 0.21 N. Improving the force measurement accuracy and integrating components for telemetric energy and data transfer are the next steps towards clinical application of intelligent orthodontic appliances based on smart brackets.

This study used an experimental dental arch model to examine the orthodontic forces generated by a quadhelix appliance in terms of parallel expansion, fan expansion, or a combination of the two. Strain gauges were attached to experimental brass rods that represented the teeth arranged in the shape of an average dental arch to detect forces in the buccal, lingual, mesial, and distal directions. Orthodontic forces generated by different types of activation were compared by Scheffe's multiple test. The largest orthodontic force generated during parallel expansion was observed at the first molar in the buccal direction. When fan expansion was applied, significant orthodontic force was observed at the canine in the mesial and labial directions, whereas force in the mesial and lingual directions was noted at the first molar. When a combination of 3 mm parallel and 5 mm fan expansion was used, the forces generated at the canine and first and second premolar, and first molar were nearly equivalent. Depending on the type of malocclusion, the most appropriate expansion technique may be parallel or fan expansion or a combination of the two. When expanding the entire dental arch simultaneously, a combination of 3 mm parallel and 5 mm fan expansion may be the most suitable.

The aim of this study was to assess the effect of bracket type on the labiopalatal forces and moments generated in the sagittal plane. Incognito™ lingual brackets (3M Unitek), STb™ lingual brackets (Light Lingual System; ORMCO), and conventional 0.018 inch slot brackets (Gemini; 3M Unitek) were bonded on three identical maxillary acrylic resin models, with a palatally displaced right lateral incisor. The transfer trays for the indirect bonding of the lingual brackets were constructed in certified laboratories. Each model was mounted on the orthodontic measurement and simulation system and ten 0.013 inch CuNiTi wires were used for each bracket type. The wire was ligated with elastomerics and each measurement was repeated once after re-ligation. The labiopalatal forces and the moments in the sagittal plane were recorded on the right lateral incisor. One-way analysis of variance and post hoc Scheffe pairwise comparisons were used to assess the effect on bracket type on the generated forces and moments. The magnitude of forces ranged from 1.62, 1.27, and 1.81 N for the STb, conventional, and Incognito brackets, respectively; the corresponding moments were 2.01, 1.45, and 2.19 N mm, respectively. Bracket type was a significant predictor of the generated forces (P < 0.001) and moments (P < 0.001). The produced forces were different among all three bracket types, whereas the generated moments differed between conventional and lingual brackets but not between lingual brackets.

Aim: To study the effects of a prophylactic fluoride regimen on the mechanical properties of nickel-titanium (Ni-Ti) archwires under clinical conditions. Method: The unloading properties of 100 Ni-Ti wires were tested using a three-point bending test at five deflections (0.5 mm, 1.0 mm, 2.0 mm. 3.0 mm, and 3.1 mm). Sixty-six 0.016 3 0.022-inch Ni-Ti wires were tested after being used intraorally for 6 weeks using two protocols. Thirty-three wires were evaluated after the use of fluoride-containing Crest toothpaste (sodium fluoride 0.243%, 0.15% w/v fluoride ion) and Equate fluoride rinse (sodium fluoride 0.05%, fluoride ion 0.0226%). Another 33 wires were examined after a nonfluoridated natural toothpaste (Tom's of Maine; calcium carbonate, xylitol, myrrh, propolis, sodium lauryl sulfate, carrageenan, spearmint and peppermint oils, glycerin, and water) was used. Another 34 Ni-Ti wires served as a control; they were tested as received. Statistical analyses were carried out with a linear-mixed model (analysis of variance [ANOVA]). Results: Force degradation occurred within both groups of intraorally used wires but not in the unused archwires. When compared to unexposed wires, those with fluoride exposure exhibited slightly higher force degradation at 3.1 and 3.0 mm deflection, but they displayed less force degradation at 0.5 and 1.0 mm deflection. Conclusions: Topical fluoride regimens decreased the unloading property of Ni-Ti wires at higher deflections but increased it at lower deflections. World J Orthod 2010;11:135-141.

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INTRODUCTION: This systematic review evaluated root resorption as an outcome for patients who had orthodontic tooth movement. The results could provide the best available evidence for clinical decisions to minimize the risks and severity of root resorption. METHODS: Electronic databases were searched, nonelectronic journals were hand searched, and experts in the field were consulted with no language restrictions. Study selection criteria included randomized clinical trials involving human subjects for orthodontic tooth movement, with fixed appliances, and root resorption recorded during or after treatment. Two authors independently reviewed and extracted data from the selected studies on a standardized form. RESULTS: The searches retrieved 921 unique citations. Titles and abstracts identified 144 full articles from which 13 remained after the inclusion criteria were applied. Differences in the methodologic approaches and reporting results made quantitative statistical comparisons impossible. Evidence suggests that comprehensive orthodontic treatment causes increased incidence and severity of root resorption, and heavy forces might be particularly harmful. Orthodontically induced inflammatory root resorption is unaffected by archwire sequencing, bracket prescription, and self-ligation. Previous trauma and tooth morphology are unlikely causative factors. There is some evidence that a 2 to 3 month pause in treatment decreases total root resorption. CONCLUSIONS: The results were inconclusive in the clinical management of root resorption, but there is evidence to support the use of light forces, especially with incisor intrusion.