Orthodontic Measurement Research Articles

An in vitro study into the efficacy of complex tooth alignment with conventional and self-ligating brackets.

To evaluate the efficacy of tooth alignment achieved by various small cross-section archwire/bracket combinations using the orthodontic measurement and simulation system. The study comprised three types of orthodontic brackets 1) conventional ligating (Victory Series and Mini-Taurus), 2) self-ligating (SmartClip a passive self-ligating bracket and Time3 an active self-ligating bracket), and 3) a conventional low-friction bracket (Synergy). All brackets had a nominal 0.022″ slot size. Brackets were combined with 1) 0.012″ stainless steel, 2) 0.012″ Orthonol, 3) 0.012″ Thermalloy, and 4) 0.0155″ coaxial archwires. Archwires were tied to the conventional brackets with stainless steel ligatures and elastomeric rings. The malocclusion simulated represented a central upper incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis). The inciso-gingival correction achieved by the different archwire/bracket combinations ranged from 15 to 95%, while the labio-lingual correction ranged from 10 to 95%. The smallest correction was achieved by coaxial, Orthonol, and thermally archwires when ligated with the elastomeric rings to conventional brackets. Stainless steel archwires achieved from 65 to 90% of inciso-gingival correction and from 60 to 90% of labio-lingual correction. The resultant tooth alignment was the product of interaction between the archwire type, bracket type, and bracket design including ligature type. Small cross-sectional archwires might produce up to 95% correction if combined properly with the bracket system. Elastomeric rings when used with conventional brackets limit the efficacy of malalignment correction.

Torque efficiency of different archwires in 0.018- and 0.022-inch conventional brackets

To compare the archwires inserted during the final stages of the orthodontic treatment with the generated moments at 0.018- and 0.022-inch brackets. The same bracket type, in terms of prescription, was evaluated in both slot dimensions. The brackets were bonded on two identical maxillary acrylic resin models, and each model was mounted on the orthodontic measurement and simulation system. Ten 0.017 × 0.025-inch TMA and ten 0.017 × 0.025-inch stainless steel archwires were evaluated in the 0.018-inch brackets. In the 0.022-inch brackets, ten 0.019 × 0.025-inch TMA and ten 0.019 × 0.025-inch stainless steel archwires were measured. A 15° buccal root torque (+15°) and then a 15° palatal root torque (-15°) were gradually applied to the right central incisor bracket, and the moments were recorded at these positions. A t-test was conducted to compare the generated moments between wires within the 0.018- and 0.022-inch bracket groups separately. The 0.017 × 0.025-inch archwire in the 0.018-inch brackets generated mean moments of 9.25 Nmm and 14.2 Nmm for the TMA and stainless steel archwires, respectively. The measured moments in the 0.022-inch brackets with the 0.019 × 0.025-inch TMA and stainless steel archwires were 6.6 Nmm and 9.3 Nmm, respectively. The 0.017 × 0.025-inch stainless steel and β-Ti archwires in the 0.018-inch slot generated higher moments than the 0.019 × 0.025-inch archwires because of lower torque play. This difference is exaggerated in steel archwires, in comparison with the β-Ti, because of differences in stiffness. The differences of maximum moments between the archwires of the same cross-section but different alloys were statistically significant at both slot dimensions.

Review on Biomechanical Simulation, Measurement and Control of Orthodontic Force

The forces and moments supplied by braces determine the movement of tooth in orthodontic treatment, so clearly quantifying the force value is very important to formulate precise treatment plan. In recent decades, scholars have presented many articles about biomechanical research on orthodontic force. Based on investigations of these papers, techniques on orthodontic force stimulation including oral model (bone, PDL and teeth included) reconstruction and constitute model construction, methods in orthodontic force measurement including physical oral model fabrication and device architectures, and techniques on orthodontic force control such as the use of shape memory alloy and shape memory polymer as the wire material, are reviewed. At the end, the conclusions and future works are given.

Removed at authors request

The forces and moments supplied by braces determine the movement of tooth in orthodontic treatment, so clearly quantifying the force value is very important to formulate precise treatment plan. In recent decades, scholars have presented many articles about biomechanical research on orthodontic force. Based on investigations of these papers, techniques on orthodontic force stimulation including oral model (bone, PDL and teeth included) reconstruction and constitute model construction, methods in orthodontic force measurement including physical oral model fabrication and device architectures, and techniques on orthodontic force control such as the use of shape memory alloy and shape memory polymer as the wire material, are reviewed. At the end, the conclusions and future works are given.

Material testing of reconditioned orthodontic brackets

While all manufacturers of orthodontic brackets label these products for single use, there are commercial providers offering bracket reconditioning (or "recycling"). We conducted this study to investigate the effects of different recycling techniques on material-related parameters in orthodontic brackets, aiming to derive indications for clinical use and conclusions about the biocompatibility, longevity, and application of recycled brackets. New metal brackets (equilibrium(®); Dentaurum, Ispringen, Germany) were compared to brackets recycled by different techniques, including direct flaming with a Bunsen burner, chemical reconditioning in an acid bath, a commercial unit (Big Jane; Esmadent, IL, USA), and outsourcing to a company (Ortho Clean, Dellstedt, Germany). Material-related examinations included the following: (1) corrosion behavior by static immersion testing and use of a mass spectrometer to determine nickel-ion concentrations in the corrosive medium, (2) surface features in scanning electron micrographs before and after corrosion testing, (3) Vickers hardness using a hardness testing machine, (4) shear bond strength as defined in DIN 13990-1, (5) dimensional stability of the bracket slots by light microscopy, and (6) frictional loss as assessed by an orthodontic measurement and simulation system (OMSS). Each examination was performed on ten brackets. Student's t-test was used for statistical analysis. Compared to the new brackets, those recycled in an acid bath or by a commercial provider revealed significant dimensional changes (p<0.05). Corrosion on the recycled brackets varied according to the recycling techniques employed. The group of brackets recycled by one company revealed hardness values that differed from those of all the other groups. No significant differences were observed in nickel-ion release, frictional loss, and shear bond strength. Recycling was found to significantly reduce the corrosion resistance and dimensional stability of orthodontic brackets. As the savings generated by recycling do not justify the risks involved, the practice of labeling orthodontic brackets for single use remains a responsible precaution that safeguards patients and orthodontists against definite risks.

Torque expression of 0.018 and 0.022 inch conventional brackets

The aim of this study was to assess the effect of the moments generated with low- and high-torque brackets. Four different bracket prescription-slot combinations of the same bracket type (Mini Diamond® Twin) were evaluated: high-torque 0.018 and 0.022 inch and low-torque 0.018 and 0.022 inch. These brackets were bonded on identical maxillary acrylic resin models with levelled and aligned teeth and each model was mounted on the orthodontic measurement and simulation system (OMSS). Ten specimens of 0.017 × 0.025 inch and ten 0.019 × 0.025 inch stainless steel archwires (ORMCO) were evaluated in the low- and high-torque 0.018 inch and 0.022 inch brackets, respectively. The wires were ligated with elastomerics into the brackets and each measurement was repeated once after religation. Two-way analysis of variance and t-test were conducted to compare the generated moments between wires at low- and high-torque brackets separately. The maximum moment generated by the 0.017 × 0.025 inch stainless steel archwire in the 0.018 inch brackets at +15 degrees ranged from 14.33 and 12.95 Nmm for the high- and low-torque brackets, respectively. The measured torque in the 0.022 inch brackets with the 0.019 × 0.025 inch stainless steel archwire was 9.32 and 6.48 Nmm, respectively. The recorded differences of maximum moments between the high- and low-torque series were statistically significant. High-torque brackets produced higher moments compared with low-torque brackets. Additionally, in both high- and low-torque configurations, the thicker 0.019 × 0.025 inch steel archwire in the 0.022 inch slot system generated lower moments in comparison with the 0.017 × 0.025 inch steel archwire in the 0.018 inch slot system.

A comparative assessment of torque generated by lingual and conventional brackets

The aim of this study was to assess the effect of bracket type on the labiopalatal moments generated by lingual and conventional brackets. Incognito™ lingual brackets (3M Unitek), STb™ lingual brackets (Light Lingual System; ORMCO), In-Ovation L lingual brackets (DENTSPLY GAC), and conventional 0.018 inch slot brackets (Gemini; 3M Unitek) were bonded on identical maxillary acrylic resin models with levelled and aligned teeth. Each model was mounted on the orthodontic measurement and simulation system and 10 0.0175 × 0.0175 TMA wires were used for each bracket type. The wire was ligated with elastomerics into the Incognito, STb, and conventional brackets and each measurement was repeated once after religation. A 15 degrees buccal root torque (+15 degrees) and then a 15 degrees palatal root torque (-15 degrees) were gradually applied to the right central incisor bracket. After each activation, the bracket returned to its initial position and the moments in the sagittal plane were recorded during these rotations of the bracket. One-way analysis of variance with post hoc multiple comparisons (Tukey test at 0.05 error rate) was conducted to assess the effect on bracket type on the generated moments. The magnitude of maximum moment at +15 degrees ranged 8.8, 8.2, 7.1, and 5.8 Nmm for the Incognito, STb, conventional Gemini, and the In-Ovation L brackets, respectively; similar values were recorded at -15 degrees: 8.6, 8.1, 7.0, and 5.7 Nmm, respectively. The recorded differences of maximum moments were statistically significant, except between the Incognito and STb brackets. Additionally, the torque angles were evaluated at which the crown torque fell well below the minimum levels of 5.0 Nmm, as well as the moment/torque ratio at the last part of the activation/deactivation curve, between 10 and 15 degrees. The lowest torque expression was observed at the self-ligating lingual brackets, followed by the conventional brackets. The Incognito and STb lingual brackets generated the highest moments.

A Comparison of Three-Dimensional and Two-Dimensional Cephalometric Evaluations of Children with Cleft Lip and Palate

The aim of this retrospective study was to compare the consistency of orthodontic measurement performed on cephalometric films and 3D CT images of cleft lip and palate (CLP) patients. The study was conducted with 2D radiographs and 3D CT images of 9 boys and 6 girls aged 7-12 with CLP. 3D reconstructions were performed using MIMICS software. Frontal analysis found statistical differences for all parameters except occlusal plane tilt (OcP-tilt) and McNamara analysis found statistical differences in 2D and 3D measurements for all parameters except ANS-Me and Co-Gn; Steiner analysis found statistical differences for all parameters except SND, SNB and Max1-SN. Intra-group variability in measurements was also very low for all parameters for both 2D and 3D images. Study results indicate significant differences between measurements taken from 2D and 3D images in patients with cleft lip and palate.

A comparative assessment of forces and moments generated by lingual and conventional brackets

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.

In-vitro assessment of the forces generated by lingual fixed retainers

The aim of this article was to assess the effect of wire adaptation on the lingual surfaces of mandibular anterior teeth with 3 types of lingual retainers on the development of vertical and labiolingual forces. Ten retainers (canine to canine) were constructed from each of the following wires: Wildcat 0.0195-in heat-treated 3-strand twist-flex wire (GAC, Bohemia, NY); Penta-one 0.0215-in 6-strand as received; and Penta-one 0.0215-in 6-strand after heat treatment at 350°C for 4 minutes (both, Masel Orthodontics, Carlsbad, Calif). The retainers were bonded on each tooth of an acrylic resin model, and the model was installed in the Orthodontic Measurement and Simulation System. The vertical and labiolingual forces generated were measured for wire displacements up to 0.2 mm in 0.02-mm increments. Wire displacement of 0.2 mm exerted forces as high as 1 N on the teeth. In the vertical direction, the highest force levels were recorded for the as-received Penta-one 0.0215-in and the lowest from its heat-treated counterpart. In the horizontal plane, the as-received Penta-one 0.0215-in exerted the highest forces. The forces recorded from the lingual retainer wires during 0.2-mm simulated intrusion-extrusion and buccal-lingual movements might generate high forces that exceed 1 N and be large enough to produce unwanted tooth movement during retention. The only significant determinant of the generated forces was the amount of wire displacement and not the type of wire used in this study.

A comparative assessment of the forces and moments generated at the maxillary incisors between conventional and self-ligating brackets using a reverse curve of Spee NiTi archwire

Abstract Objectives To compare the intrusive forces and labio-palatal moments generated at the maxillary incisors by a 0.017 x 0.025 inch reverse curve NiTi wire using self-ligating and conventional brackets. Methods Ten 0.017 x 0.025 inch reverse curve NiTi archwires were used with each of the following 0.022 inch bracket systems: Titanium Ortho (Ormco/Sybron, CA, USA), In-Ovation R (GAC International, NY, USA) and Damon System 3MX (Ormco/Sybron, CA, USA). The wires were inserted on bracketed maxillary Frasaco models, with segmented maxillary incisors. Simulated intrusion from 0.0-1.0 mm was performed on the Orthodontic Measurement and Simulation System, which recorded the intrusive forces and the labio-palatal moments at 0.05 mm increments. The data were analysed with the ANOVA and Scheffe tests. Results The intrusive forces were significantly different between all bracket types. The highest force was recorded with the conventional Titanium Orthos brackets (8.2 N), followed by the Damon 3MX brackets (6.3 N) and the In-Ovation R brackets (5.5 N). The moments were found to be significantly different between the conventional and the self-ligating brackets, but not between the two types of self-ligating brackets. The highest moments were recorded with the self-ligating brackets (16.6-16.9 N/mm), followed by the conventional brackets (10.8 N/mm). Conclusions The intrusive forces exerted on the maxillary incisors by a 0.017 x 0.025 inch reverse curve NiTi archwire during the final 1 mm of levelling are very high and beyond the necessary intrusive force level for these teeth. Lower intrusive forces, but higher labio-palatal moments, were recorded with the self-ligating brackets.

Automated Landmark Extraction for Orthodontic Measurement of Faces Using the 3-Camera Photogrammetry Methodology

To set up a three-dimensional photogrammetric scanning system for precise landmark measurements, without any physical contact, using a low-cost and noninvasive digital photogrammetric solution, for supporting several necessity in clinical orthodontics and/or surgery diagnosis. Thirty coded targets were directly applied onto the subject's face on the soft tissue landmarks, and then, 3 simultaneous photos were acquired using photogrammetry, at room light conditions. For comparison, a dummy head was digitized both with a photogrammetric technique and with the laser scanner Minolta Vivid 910i (Konica Minolta, Tokyo, Japan). The precise measurement of the landmarks is ranged between 0.017 and 0.029 mm. The system automatically measures spatial position of face landmarks, from which distances and angles can be obtained. The facial measurements were compared with those done using laser scanning and manual caliper. The adopted method gives higher precision than the others (0.022-mm mean value on points and 0.038-mm mean value on linear distances on a dummy head), is simple, and can be used easily as a standard routine. The study demonstrated the validity of photogrammetry for accurate digitization of human face landmarks. This research points out the potential of this low-cost photogrammetry approach for medical digitization.

Forces and moments on posterior teeth generated by incisor intrusion biomechanics

To comparatively evaluate the extrusive forces and torquing moments on the posterior dentition generated during anterior intrusion with different intrusion techniques in the maxillary and mandibular dental arch. Seven wire specimens were used for each of the following intrusive arches: Utility arch 0.016 x 0.016' Blue Elgiloy, Utility arch 0.017 x 0.025' TMA and Burstone Intrusion arch 0.017 x 0.025' TMA. The wires were inserted on bracketed dental arches constructed on maxillary Frasaco models, segmented mesially to the maxillary canines. Simulated intrusion from 0.0-3.0 mm was performed on the Orthodontic Measurement and Simulation System (OMSS). The forces and moments were recorded in all three planes of space at 0.1 mm increments and the values at 3.0 mm for all wires were used for all statistical evaluations. The data were analyzed, separately for the forces and moments, by means of two-way analysis of variance (ANOVA) with forces and moments serving as the dependent variables and intrusion technique and jaw (maxilla or mandible) as the independent variable. Post hoc multiple comparisons were performed using the Tukey test at .05 error rate. The 0.016 x 0.016' Blue Elgiloy utility arch exerted the highest posterior extrusive forces, 15% higher than the 0.017 x 0.025' TMA utility and 40% higher in comparison with the 0.017 x 0.025' TMA Burstone intrusion arch.The lowest posterior moment in the sagittal plane was generated by the 0.017 x 0.025' TMA Burstone intrusion arch. The 0.016 x 0.016' Blue Elgiloy utility arch exerted 15% higher posterior moments and the 0.017 x 0.025' TMA utility 25% higher. Forces and moments were consistently larger for the mandible compared to the maxilla for the same intrusion technique. The upper Burstone 0.017 x 0.025' TMA intrusion arch exerted the lowest forces/moments on posterior teeth. The highest forces were generated by the 0.016 x 0.016-inch Blue Elgiloy utility arch and the highest moments by the lower 0.017 x 0.025-inch TMA utility arch.

A comparative assessment of the forces and moments generated with various maxillary incisor intrusion biomechanics

The aim of this study was to comparatively evaluate the intrusive forces and buccolingual torquing moments generated during anterior maxillary intrusion using different maxillary incisor intrusion mechanics. Five wire specimens were used for each of the following intrusive arches: blue Elgiloy utility arch 0.016 x 0.016 inch, TMA utility arch 0.017 x 0.025 inch, Burstone TMA intrusion arch 0.017 x 0.025 inch, and reverse curve of Spee NiTi 0.016 x 0.022 inch. The wires were inserted on bracketed dental arches constructed on maxillary Frasaco models, segmented mesially to the maxillary canines. Simulated intrusion from 0.0 to 3 mm was performed using the orthodontic measurement and simulation system (OMSS), and forces and moments were recorded in the sagittal plane at 0.1 mm vertical displacement increments. All measurements were repeated five times for each specimen and values recorded at 1.5 mm for all wires were used for statistical evaluations. The results were analysed with one-way analysis of variance with forces and moments serving as the dependent variables and wire type as the independent variable. Post hoc multiple comparisons were performed using the Tukey test (0.05 error rate). Comparison of the two major intrusion techniques for the maxillary anterior teeth, segmented and bioprogressive, revealed that the Burstone TMA 0.017 x 0.025 inch intrusion arch exerted the lowest force on the incisors (0.99 N), followed by the TMA utility 0.017 x 0.025 inch (1.33 N) and the blue Elgiloy 0.016 x 0.016 inch utility (1.43 N). The highest force was recorded for the reverse curve of Spee NiTi and exceeded the value of 9 N. The lowest buccolingual moments were recorded with the Burstone intrusion arch (2.47 Nmm), whereas the highest was registered for the utility arch constructed with a 0.017 x 0.025 inch TMA wire (7.31 Nmm).

Forces and Moments Generated with Various Incisor Intrusion Systems on Maxillary and Mandibular Anterior Teeth

To evaluate the comparative intrusive forces and torquing moments in the sagittal plane generated during anterior intrusion using different incisor intrusion mechanics in the maxillary and mandibular anterior teeth. Five wire specimens were used for each of the following intrusive arches: non-heat-treated, 0.016 x 0.016-inch blue Elgiloy utility arch, 0.017 x 0.025-inch TMA utility arch, and 0.017 x 0.025-inch TMA Burstone intrusion arch. The wires were constructed according to the specifications given by their inventors and were inserted on bracketed dental arches on Frasaco models, segmented mesial to the canines. Simulated intrusion from 0.0-1.5 mm was performed on the Orthodontic Measurement and Simulation System (OMSS), and forces and moments were recorded at 0.1 mm vertical displacement increments. All measurements were repeated five times for each specimen, and maximum values recorded at 1.5 mm for all wires were used for all statistical evaluations. The data were analyzed with two-way analysis of variance (ANOVA) with forces and moments serving as the dependent variables, separately, and wire type and jaw as the independent variables. Post hoc multiple comparisons were performed using the Tukey test (.05 error rate). The 0.017 x 0.025-inch TMA Burstone intrusion arch exerted the lowest intrusive forces, followed by the 0.017 x 0.025-inch TMA utility and the 0.016 x 0.016-inch blue Elgiloy utility arch. The lowest anterior moment in the sagittal plane in this experiment was generated from the 0.017 x 0.025-inch TMA Burstone intrusion arch. The intrusive forces, as well as the generated moments, were always higher in the mandible, where significant differences were observed among the configurations tested.

The Leveling Effectiveness of Self-ligating and Conventional Brackets for Complex Tooth Malalignments

The transfer of forces and moments between the bracket and archwire is decisive in the multi-band/bracket technique. New developments in bracket design and ligation method aim to optimize the transfer of forces and moments and improve leveling effectiveness. We thus aimed in this study to investigate whether leveling behavior is influenced by different bracket systems, or by the ligation method. The baseline situation for this examination was a complex tooth malalignment. Using the orthodontic measurement and simulation system (OMSS), we tested the leveling effectiveness of nine self-ligating bracket systems made by various manufacturers (Forestadent-Quick, in active and passive variants, Dentsply GAC In-Ovation, adenta TIME, Ormco Damon 2 and Damon 3MX, UP-Dental Opal-M and Opal-2, Strite SPEED) in the 0.022 inch slot system. A conventional bracket system (Dentaurum discovery) was used for reference purposes. We also used a multistranded steel archwire (Ormco Tripleflex, 0.44 mm round) and four nickel-titanium archwires of various diameters (Forestadent BioStarter 0.30 mm round, BioStarter 0.40 mm round, Titanol Low Force 0.40 x 0.40 mm(2) and Titanol Low Force 0.40 x 0.56 mm(2)). The leveling task consisted of correcting a complex malalignment (infraocclusion and vestibular displacement, each of 2 mm) of tooth 21. We analyzed the forces and torque movements that arose during the leveling phase. The test of the ten bracket systems revealed no significant difference in terms of their leveling effectiveness. Both selfligating brackets and conventional brackets behaved similarly, and we observed roughly 80% of the infraocclusions to have been corrected. Vestibular displacement was corrected with all the bracket systems by as much as 100% or even more due to a developing torque movement. The influence of wire material and wire diameter became apparent in relation to existing forces durconvening the leveling stage; those factors' influence was clearly greater than that of the ligation method. This study's results demonstrate that bracket selection has a negligible influence on leveling effectiveness. Although self-ligating brackets are easier for the orthodontist to manipulate and provide patients with esthetic and wearing comfort advantages, they are not superior to conventional brackets in terms of their biomechanical characteristics.

Comparative assessment of forces generated during simulated alignment with self-ligating and conventional brackets

The objectives of this study were to comparatively assess the magnitude and direction of forces and moments generated from different bracket systems, during the initial levelling and alignment stage of orthodontic treatment. Three types of brackets were used: Orthos2 (Ormco), Damon2 (Ormco), and In-Ovation R (GAC). The brackets were bonded on resin replicas models of a patient's crowded mandibular arch, and a 0.014 inch Damon archform CuNiTi (Ormco) wire was inserted. The model was mounted on the Orthodontic Measurement and Simulation System (OMSS) and six static measurements were taken at the initial crowded state per bracket for the lateral incisor, canine, and first premolar. A total of 10 repetitions were performed for each measurement, with new brackets and archwires used for each trial. The forces and moments generated were registered directly on the OMSS software and were statistically analyzed using a one-way analysis of variance separately for each dental arch location and force component. Group differences were further analyzed with Tukey's post hoc comparisons test at the 0.05 significance level. The lingually inclined, crowded lateral incisor presented an extrusive and buccal movement and showed the lowest force in the vertical direction, whereas the self-ligating group of brackets generated the highest force in the buccolingual direction. The moments applied by the three bracket systems followed the general trend shown for forces; in the vertical axis, the self-ligating brackets exerted lower forces than their conventional counterpart. This was modified in the buccolingual direction where, in most instances, the self-ligating appliances applied higher moments compared with the conventional bracket. In most cases, the magnitude of forces and moments ranged between 30-70 cN and 2-6 N mm, respectively. However, maximum forces and moments developed at the lateral incisor were almost four times higher than the average.

Moments Generated during Simulated Rotational Correction with Self-Ligating and Conventional Brackets

To assess comparatively the magnitude of moments generated during rotational correction from different bracket systems during the late leveling and alignment stage of orthodontic treatment. The three types of brackets assessed were Orthos2 (ORMCO, Glendora, CA), Damon2 (ORMCO), and In Ovation-R (GAC, Bohemia, NY). The brackets were bonded on replicas made of resin from models constructed from an aligned patient's mandibular arch, and a 0.014- x 0.025-inch CuNiTi (ORMCO) wire was inserted. Orthodontic rotational correction was simulated on the Orthodontic Measurement and Simulation System from -5 degrees to +5 degrees rotation in 0.25 degrees increments on the distal and mesial direction. The moments generated at each increment of rotation throughout the full rotation path were statistically analyzed using a two-way analysis of variance and Tukey test at the .05 level of significance. Both bracket type and direction of rotation showed an effect on moment magnitude. The highest moment (27.2 Nmm) was observed for the Damon2 bracket assigned to its noncompliant slot wall door. Higher moments were found during distal premolar rotation. The In Ovation-R showed a magnitude of moment in the range of 9.0 Nmm in the same direction, whereas conventional brackets presented the lowest moments (5.0 Nmm). A wide variation in magnitude of moments exerted by self-ligating and conventional brackets is noted in the simulated rotational correction of teeth, which relates to the geometry of the dental arch, the tooth position, and the rigidity of the closing component of the bracket slot.

Torque expression of self-ligating brackets compared with conventional metallic, ceramic, and plastic brackets

The purpose of this research was to investigate the torque capacity of active and passive self-ligating brackets compared with metallic, ceramic, and polycarbonate edgewise brackets. Six types of orthodontic brackets were included in the study: the self-ligating Speed and Damon2, the stainless steel (SS), Ultratrimm and Discovery, the ceramic bracket, Fascination 2, and the polycarbonate bracket, Brillant. All brackets had a 0.022-inch slot size and were torqued with 0.019 x 0.025-inch SS archwires. For this purpose, the labial crown torque of an upper central incisor was measured in a simulated intraoral clinical situation using the orthodontic measurement and simulation system (OMSS). A torque of 20 degrees was applied and the correction of the misalignement was simulated experimentally with the OMSS. Each bracket/wire combination was measured five times. Maximum torquing moments and torque loss were determined. The results were analysed with one-way analysis of variance, with the bracket serving as the sole discriminating variable, and the Tukey test at the 0.05 level of significance. The ceramic bracket (Fascination 2) presented the highest torquing moment (35 Nmm) and, together with a SS bracket, the lowest torque loss (4.6 degrees). Self-ligating, polycarbonate, and selective metallic brackets demonstrated almost a 7-fold decreased moment developed during insertion of a 0.019 x 0.022-inch SS wire into a 0.022-inch slot and a 100 per cent increase in loss.

Forces exerted by conventional and self-ligating brackets during simulated first- and second-order corrections

Our aim in this study was to comparatively assess the forces generated from conventional and self-ligating bracket systems during the late leveling and alignment stage, specifically for first- and second-order movement. Three types of brackets were selected: Orthos2 (Ormco, Glendora, Calif), Damon2 (Ormco), and In Ovation-R (GAC, Bohemia, NY). The brackets were bonded on resin replicas constructed from a model of an aligned mandibular arch, and a 0.014 x 0.025-in copper-nickel-titanium wire (Ormco) was placed. First- and second-order corrections-buccolingual and intrusion-extrusion movements-were simulated on the orthodontic measurement and simulation system. A 2-mm displacement was applied on the x-axis and a 1-mm displacement on the z-axis, both in 0.1-mm intervals; 5 repetitions were performed for each wire-bracket-interval combination, and new brackets and archwires were used for each trial. The forces generated by manipulation of the bracket in the 2 directions were recorded directly with the orthodontic measurement and simulation system software and were statistically analyzed with 2-way ANOVA, with bracket and displacement as the discriminating variables. Group differences were further analyzed with the Tukey post-hoc comparisons test with the family error rate set at the 0.05 level. In the first-order correction, the direction showed a significant effect on force magnitude, with inward (lingual) movement having lower force levels for the In Ovation-R. No significant difference was found between the Damon2 and the conventional appliance for this movement. In the second-order model, no difference was noted between the 2 self-ligating brackets in magnitude of force, but the conventional bracket showed higher force levels, which accounted for 20%, or 1 N, of the increase in magnitude. The effect of the direction of displacement (intrusion vs extrusion) on force variation did not produce a significant effect. The forces generated by first- and second-order corrections in self-ligating appliances do not show a consistent pattern and depend on the wire, the direction of movement, and the design of the ligating component.