An alternative approach for the surgical correction of unilateral crossbite.

This case report aims to describe a modified surgically assisted rapid palatal expansion technique to treat an asymmetrical posterior crossbite with no mandibular shift without causing an interincisal diastema. A clinical patient with an asymmetrical crossbite, large tooth-size-arch length, and Bolton discrepancy is used to illustrate the modified technique. Instead of traditional osteotomies, in this technique, the osteotomy is done between the maxillary right canine and lateral incisor (connecting the piriform aperture to the alveolar process) along with a unilateral LeFort I osteotomy. The expansion forces are produced by the activation of a conventional hyrax appliance. The skeletal unilateral crossbite was corrected without major changes to the opposite side and without causing an anesthetic diastema between the maxillary central incisors. A mandibular incisor extraction produced the space needed to treat the tooth size-arch length and corrected the Bolton discrepancy. This allowed a successful treatment of the problems initially presented by the patient.

Loads of continuous mechanics for uprighting the second molar on the second molar and premolar.

INTRODUCTION: This paper aims to evaluate the effect of tube height on uprighting a mandibular second molar with a continuous arch, specifically the main effects on the molar tube and the side effects on the second premolar bracket. METHODS: Slot brackets (0.18-in) and tubes were passively bonded from the left second molar to the right second premolar of the patient's cast and fixed to an orthodontic force tester. A mesially tipped second molar along with its tube was positioned at 5 different heights in relation to the bracket slots of the remaining appliance: 2 mm below (group -2), 1 mm below (group -1), leveled (group 0), 1 mm above (group 1) and 2 mm above (group 2). Each group had 10 different 0.016 × 0.022-in superelastic nickel-titanium wires tied one at a time to the appliance to register the vertical forces (Fz) and tipping moments (Mx) produced at the molar tube and the premolar bracket, statistically. Analysis of variance was used to identify differences of load among the groups for wire response to the position of the tube in relation to the other brackets' slots. RESULTS: As the molar tube was positioned more occlusally, Fz and Mx decreased at the molar tube from 1.31 N to 0.75 N and 13.98 N.mm to 11.84 N.mm, respectively, whereas at the premolar bracket, Fz and Mx decreased from 1.52 N to 0.88 N and 8.77 N.mm to 1.05 N.mm, respectively. CONCLUSIONS: In all groups, the load system at the molar tube (the main effects) registered a distal tipping moment and an extrusive force, whereas at the premolar bracket, the load system (side effects) included a distal tipping moment and an intrusive force. As the tube moved occlusally, the extrusive force and the uprighting moment decreased, along with the side effects at the premolar bracket. Attempting to bond the molar tube more occlusally (within reasonable intraoral dimensions) when trying to upright a molar does not appear to be sufficient to keep a molar from extruding.

Can we expect similar behavior among CuNiTi 35°C wires?

OBJECTIVE: This paper aims to verify the thermodynamic, mechanical and chemical properties of CuNiTi 35ºC commercial wires. METHODS: Forty pre-contoured copper-nickel-titanium thermodynamic 0.017 x 0.025-in archwires with an Af temperature of 35°C were used. Eight wires from five different manufacturers (American Orthodontics® [G1], Eurodonto® [G2], Morelli® [G3], Ormco® [G4] and Orthometric® [G5]) underwent cross-sectional dimension measurements, tensile tests, SEM-EDS and differential scanning calorimetry (DSC) tests. Parametric tests (One-way ANOVA and Tukey post-test) were used, with a significance level of 5%, and Pearson's correlation coefficient test was performed between the Af and chemical elements of the wires. All sample tests and statistical analyses were double-blinded. RESULTS: All wires presented standard dimensions (0.017 x 0.025-in) and superelastic behavior, with mean plateau forces of: G1 = 36.49N; G2 = 27.34N; G3 = 19.24 N; G4 = 37.54 N; and G5 = 17.87N. The Af means were: G1 = 29.40°C, G2 = 29.13°C and G3 = 31.43°C, with p>0.05 relative to each other. G4 (32.77°C) and G5 (35.17°C) presented statistically significant differences between each other and among the other groups. All samples presented Ni, Ti, Cu and Al in different concentrations. CONCLUSIONS: The chemical concentration of the elements that compose the alloy significantly influenced the thermodynamic and mechanical properties.

Can we expect similar behavior among CuNiTi 35°C wires?

ABSTRACT Objective: This paper aims to verify the thermodynamic, mechanical and chemical properties of CuNiTi 35ºC commercial wires. Methods: Forty pre-contoured copper-nickel-titanium thermodynamic 0.017 x 0.025-in archwires with an Af temperature of 35°C were used. Eight wires from five different manufacturers (American Orthodontics® [G1], Eurodonto® [G2], Morelli® [G3], Ormco® [G4] and Orthometric® [G5]) underwent cross-sectional dimension measurements, tensile tests, SEM-EDS and differential scanning calorimetry (DSC) tests. Parametric tests (One-way ANOVA and Tukey post-test) were used, with a significance level of 5%, and Pearson's correlation coefficient test was performed between the Af and chemical elements of the wires. All sample tests and statistical analyses were double-blinded. Results: All wires presented standard dimensions (0.017 x 0.025-in) and superelastic behavior, with mean plateau forces of: G1 = 36.49N; G2 = 27.34N; G3 = 19.24 N; G4 = 37.54 N; and G5 = 17.87N. The Af means were: G1 = 29.40°C, G2 = 29.13°C and G3 = 31.43°C, with p>0.05 relative to each other. G4 (32.77°C) and G5 (35.17°C) presented statistically significant differences between each other and among the other groups. All samples presented Ni, Ti, Cu and Al in different concentrations. Conclusions: The chemical concentration of the elements that compose the alloy significantly influenced the thermodynamic and mechanical properties.

RESUMO Objetivo: O presente artigo teve como objetivo verificar as propriedades termodinâmicas, mecânicas e químicas de fios CuNiTi 35°C comerciais. Métodos: Foram utilizados 40 arcos termodinâmicos pré-contornados de cobre-níquel-titânio de 0,017" x 0,025" e temperatura Af de 35°C. Oito fios de cinco fabricantes diferentes (American Orthodontics® [G1], Eurodonto® [G2], Morelli® [G3], Ormco® [G4] e Orthometric® [G5]) foram submetidos a medições de suas secções transversais, testes de tração, MEV-EDS e calorimetria diferencial (DSC). Foram utilizados testes paramétricos (One-way ANOVA e pós-teste de Tukey), com nível de significância de 5%, e foi realizado o teste do coeficiente de correlação de Pearson entre a temperatura Af e os elementos químicos dos fios. Todos os testes das amostras e análises estatísticas foram duplo-cegos. Resultados: Todos os fios apresentavam dimensões padronizadas (0,017" x 0,025") e comportamento superelástico, com forças médias de platô de G1 = 36,49 N; G2 = 27,34 N; G3 = 19,24 N; G4 = 37,54 N; e G5 = 17,87 N. As médias de Af foram: G1 = 29,40°C, G2 = 29,13°C e G3 = 31,43°C, com p> 0,05 entre si. G4 (32,77°C) e G5 (35,17°C) apresentaram diferenças estatisticamente significativas entre si e entre os demais grupos. Todas as amostras apresentaram Ni, Ti, Cu e Al em diferentes concentrações. Conclusões: A concentração química dos elementos que compõem a liga influenciou significativamente as propriedades termodinâmicas e mecânicas.

Effects of orthodontic tooth extrusion produced by different techniques, on the periodontal tissues: a histological study in dogs.

OBJECTIVE: The aim of this study was to compare the periodontal tissue changes resulting from different methods of orthodontic tooth extrusion in dogs. MATERIALS AND METHODS: Notches were surgically prepared in the root surface at the bone crest level of the first premolars of mongrel dogs. After 37 days, extrusion of the first lower and upper premolars was randomly performed by 3 different methods: conventional orthodontic extrusion (OE); open flap debridement performed immediately before orthodontic extrusion (OF); and orthodontic extrusion associated with weekly fiberotomy and scaling (FS). For all groups, extrusion was performed for 21 days followed by one-month retention and sacrifice. Periodontal parameters, descriptive histology, and histomorphometric analyses were performed at the end of the experimental period. RESULTS: The median extrusion was 2.25 in the fiberotomy group, 2.0 mm in the open flap group and 1.0 mm in the orthodontic extrusion group with no significant differences between groups. The highest distance between reference notch and bone crest was observed in the fiberotomy group (p < 0.05). Histologically, radicular resorption repaired with cellular cementum was detected in all groups. CONCLUSIONS: Tooth extrusion was successfully achieved with all of the different methods of orthodontic tooth extrusion with no statistical significance between techniques. The fiberotomy approach was effective in avoiding coronal displacement of periodontal tissues. Fiberotomy associated with scaling should be indicated if the objective of the treatment is extrusion without periodontal tissue displacement.

Expansion with transpalatal arch or continuous arch mechanics.

INTRODUCTION: This study aimed to compare the 3-dimensional force system produced by transpalatal arch (TPA) mechanics with that produced by a continuous arch (CA) on the expansion of maxillary first molars. METHODS: A patient's model with 2 molars in 4-mm crossbite had orthodontic appliances bonded to all teeth. The first and the second molars were connected to two 3-dimensional load cells to compare the forces in the transverse and anteroposterior planes (Fx and Fy) and the rotational moments (Mz) produced in both molars by the expanded TPA and by 0.016-in nickel-titanium CA. The data were evaluated using 6 independent t tests, and the net moment at the molar's center of resistance was also calculated. RESULTS: All forces and moments were different at both molars. At the first molar, CA produced Fx of 2.60 N, Fy of -0.08 N, Mz of -5.16 N·mm, and Net Mz of -5.68 N·mm, whereas the TPA produced Fx of 2.87 N, Fy of -0.60 N, Mz of -22.08 N·mm, and Net Mz of -25.09 N·mm. At the second molar, the TPA did not produce significant forces and moments, whereas the CA produced Fx of -1.00 N, Mz of 3.95 N·mm, Fy of -0.84 N, and Net Mz of -0.67 N·mm. CONCLUSIONS: Based on our findings in a clinical set up with the specific horseshoe TPA and archwire tested, with the TPA used only on the first molars and the CA used from one second molar to the other, the mechanics produced different expansion forces at the first molar. The TPA produced a larger rotational side effect on the first molar, whereas the CA produced side effects on the second molar.

Concomitant permanent maxillary canine agenesis and transposition treated with extractions and lingual brackets.

This case report describes the successful orthodontic treatment for a healthy woman with maxillary canine-premolar transposition associated with rare hypodontia of the contralateral canine. The treatment included extraction of the transposed maxillary right and deciduous maxillary left canines and 2 mandibular second premolars. The objectives of the treatment were to (1) correct the upper midline deviation and the occlusal plane cant, (2) move the maxillary first premolars into the canine position, (3) retract the mandibular incisors to improve the facial profile, and (4) reduce the labial protrusion. Orthodontic treatment was carried out with the lingual technique in the maxillary arch and esthetic ceramic brackets in the mandibular arch. The segmented mechanics were effective, fast, and consistently promoted the necessary movement without side effects. The smile line was improved, resulting in an ideal and esthetic gingival exposition, with the borders of the maxillary teeth following the lower lip smile curvature. The patient achieved ideal dentofacial esthetics, achieved better dental and functional occlusion, was pleased with her improved facial contour, and as a result, showed an improved self-image.

Protocolo clínico de desgastes interproximais no tratamento com alinhadores ortodônticos / Clinical protocol for interproximal reduction in treatment with orthodontic aligners

Resumo O tratamento com alinhadores ortodônticos já uma realidade na prática ortodôntica, em especial para casos de baixa complexidade. Em muitos desses casos, a falta de espaço, caracterizada pelo apinhamento, faz parte do problema. Assim, com intuito de prover espaços, dentre inúmeros recursos existentes, pode-se também considerar o desgaste interproximal, a depender de cada caso. Com a finalidade de reduzir o diâmetro mesiodistal dos dentes, os desgastes interproximais precisam ser feitos de forma criteriosa. O objetivo desse artigo é apresentar um protocolo seguro de desgastes interproximais considerando diferentes situações cínicas. (AU)

Abstract Treatment with orthodontic aligners is already a reality in orthodontic practice, especially for low complexity cases. In many of these patients, the lack of space, characterized by crowding, is part of the problem. Thus, in order to provide spaces, among numerous available resources, interproximal reduction may be considered, depending on each case. In order to shorten mesiodistal teeth width, interproximal reduction should be done carefully. This paper aims to present a reliable protocol for interproximal reduction considering different clinical situations. (AU)

Low-level laser therapy (830 nm) on orthodontic pain: blinded randomized clinical trial.

The objective of this research was to compare the effect single low-level laser therapy (LLLT) irradiation on pain perception in patients having fixed appliance treatment in the clinic of orthodontics. Sixty-two patients were recruited to participate in this randomized, double-blinded, placebo-controlled study. The patients were assigned to four groups: group I-laser on the right side; group II-placebo on the right side; group III-laser on the left side; group IV-placebo on the left. The laser or placebo was applied before separation, 24 and 48 h after separation of their first permanent molars in the lower arch. Just after the separation, the average of the pain for the placebo group was 1.6, significantly greater than the average of 1.1 registered for the laser group (p = 0.013). After 24 h and before the new irradiation, the values registered among the different groups did not show any differences. In relation to the gender, only after the first irradiation in placebo group, the female had a level of pain (0.1) significantly higher (p = 0.04) compared to male, and after 48 h, the group where the laser was applied had a difference (p = 0.04) among the gender with a value of lower pain for men (0.6) than for women (1.6).The laser irradiation to minimize the pain was only effective when applied immediately after treatment and separation. In general way, there were no differences between the genders, except after the first placebo group irradiation in which the female had a significantly higher level of pain compared to male and after 48 h. The pain cycle observed in this study had its peak in 24 h, both for laser's and placebo's group.

Confecção digitalizada 3D de placas oclusais / Occlusal splints 3D digitized preparation

Os distúrbios da articulação temporomandibular (DTMs), bruxismo, apertamento dental, problemas oclusais e estresse são as principais causas que motivam o cirurgião-dentista a indicar a utilização terapêutica de placas oclusais. A confecção dessas placas no modo tradicional é amplamente divulgada na literatura mundial, porém devido a diferentes filosofias e técnicas de confecção, bem como falta de comunicação precisa com o protético, diversos dentistas apresentam dificuldade na perfeita indicação e instalação das placas oclusais. Assim o objetivo desse artigo é apresentar de maneira simplificada as etapas de desenvolvimento das placas oclusais com tecnologia digital, desde o escaneamento intrabucal até a impressão 3D e instalação no paciente. As principais vantagens que estimulam cada vez mais o desenvolvimento da técnica digital estão relacionadas à diminuição de possíveis erros de confecção, juntamente com maior precisão nas etapas aliadas ao custo similar dos procedimentos tradicionais, integrando ainda um menor tempo de execução.(AU)

Temporomandibular joint disturbances (TMD), bruxism, dental tightening, occlusal problems and stress are the main causes that lead the dentist to indicate therapeutic occlusal splints. The manufacturing of these splints in the traditional way is widely spread in the worldwide literature, however due to different manufacturing philosophies and techniques, as well as lack of precise communication with the prosthodontist, it is difficult for several dentists the perfect indication and installation of the occlusal splints. So the objective of this article is to present in a simplified way the stages of the occlusal splints development with digital technology, from the intraoral scanning to the 3D printing, and installation in the patient. The main advantages that stimulate more and more the development of the digital technique are related to the reduction of possible manufacturing errors, together with bigger precision in the stages combined to the similar cost of traditional proceedings, also integrating a shorter execution time (AU)

Protocolo clínico para instalação de attachments em casos tratados com alinhadores ortodônticos ­ descrição da técnica / Clinical protocol for attachments bonding in cases treated with aligners ­ Technique Description

Resumo O tratamento ortodôntico com alinhadores é algo desejado cada vez mais pelos pacientes. Sabe-se que esses dispositivos carregam consigo vantagens e desvantagens quando comparados ao aparelho fixo convencional. Em uma tentativa de potencializar os movimentos planejados virtualmente, na grande maioria dos casos attachments são necessários. Nesse sentido, é de suma importância um protocolo seguro de instalação dos attachments, conferindo assim uma maior estabilidade e estética desses. O objetivo deste artigo é descrever o momento de instalação dos attachments em uma paciente, destacando os materiais utilizados (AU)

Abstract Today, many patients demand orthodontic treatment using aligners. It is widely known that that these devices have both advantages and disadvantages compared to conventional brackets. In order to produce better results attachments are generally needed to accomplish most dental movements. Thus, it is of upmost importance to have a safe and sound protocol to install attachments. This allows greater stability to their bonding and adequate esthetics to the patient. The aim of this clinical report is to describe how to add attachments to a patient, depicting all the materials needed for that purpose (AU)

Colagem indireta virtual com o software Ortho Analyzer / Virtual Indirect bonding with Ortho Analyzer software

O correto posicionamento dos acessórios ortodônticos é de suma importância para uma boa finalização. Com o uso da tecnologia CAD-CAM na Ortodontia, hoje é possível posicionar os acessórios virtualmente e avaliar a repercussão desse posicionamento após o alinhamento e nivelamento dos dentes. Com os acessórios colados na posição desejada, é confeccionada uma guia de transferência virtual e, em seguida, impressa por meio de uma impressora 3D. Dessa forma, é possível minimizar erros, o que demandaria maior necessidade de confecção de dobras nos fios e maior tempo de tratamento. A proposta desse artigo é, por meio de um caso clínico, apresentar um protocolo laboratorial e clínico de colagem indireta virtual. (AU)

Correct brackets positioning is very important for appropriate finishing. The use of CAD/CAM technology in Dentistry today allows brackets virtual positioning and assessment of this position after teeth alignment and leveling. Brackets can therefore be positioned according to their final estimated position. When brackets are bonded in the desired position, a virtual transfer guide is created, and 3D printed. Thus, it is possible to minimize errors, which would require bends in the wires and possibly increase treatment time. The aim of this paper is to describe a clinical case, presenting laboratorial and clinical protocol of a virtual indirect bonding. (AU)

Second molar intrusion: Continuous arch or loop mechanics?

INTRODUCTION: Our aim was to compare the load systems produced by rectangular loops and continuous arch mechanics on intrusion of a maxillary second molar. METHODS: An orthodontic appliance was passively bonded from second molar to second molar on a patient's model fixed to an orthodontic force tester. The second molars were extruded by 3 mm, and 2 mechanics systems were compared: beta-titanium rectangular loops and super-elastic nickel-titanium continuous arch. Vertical (Fz) and mesial (Fy) forces, and tipping moments around the buccal axis (Mx) at the tubes were collected at every 0.5 mm of deactivation. Repeated measures analysis of variance was used to detect differences between mechanics. The net Mx was also estimated at the center of resistance of each molar. RESULTS: Significant differences were found between the mechanics at the tubes, except for the Mx in the first molar, and more importantly, at the centers of resistance of the molars: Fz forces were greater in the continuous arch than in the rectangular loops, which, on the other hand, produced lower Fy forces than the continuous arch. In the second molar, net Mx was low initially and changed with deactivation. In the continuous arch, net Mx decreased from -3.6 N.mm of mesial crown tipping to clinically insignificant levels after 2 mm of deactivation. In the first molar, net Mx was lower on the rectangular loop than on the continuous arch during the first 2 mm of deactivation and became similar in the last millimeter of deactivation. Additionally, the net Mx decreased with deactivation with both mechanics. CONCLUSIONS: Both mechanics can intrude the second molars. Although the rectangular loop produced less tipping in large deflections, the continuous arch was a better approach when less intrusion was required.

Welding strength of NiTi wires.

OBJECTIVE: To identify the appropriate power level for electric welding of three commercial brands of nickel-titanium (NiTi) wires. METHODS: Ninety pairs of 0.018-in and 0.017 × 0.025-in NiTi wires were divided into three groups according to their manufacturers - GI (Orthometric, Marília, Brazil), GII (3M OralCare, St. Paul, CA) and GIII (GAC,York, PA) - and welded by electrical resistance. Each group was divided into subgroups of 5 pairs of wires, in which welding was done with different power levels. In GI and GII, power levels of 2.5, 3, 3.5, 4, 4.5 and 5 were used, while in GIII 2.5, 3, 3.5 and 4 were used (each unit of power of the welding machine representing 500W). The pairs of welded wires underwent a tensile strength test on an universal testing machine until rupture and the maximum forces were recorded. Analysis of variance (ANOVA) and post-hoc tests were conducted to determine which subgroup within each brand group had the greatest resistance to rupture. RESULTS: The 2.5 power exhibited the lowest resistance to rupture in all groups (43.75N for GI, 28.41N for GII and 47.57N for GIII) while the 4.0 power provided the highest resistance in GI and GII (97.90N and 99.61N, respectively), while in GIII (79.28N) the highest resistance was achieved with a 3.5 power welding. CONCLUSIONS: The most appropriate power for welding varied for each brand, being 4.0 for Orthometric and 3M, and 3.5 for GAC NiTi wires.

Effects of reducing light-curing time of a high-power LED device on shear bond strength of brackets.

PURPOSE: To assess the effects of reducing the curing time of a high-power light-emitting diode (LED) unit (Valo, Ultradent, South Jordan, UT, USA) on shear bond strength (SBS) of metal brackets and on the amount of adhesive remnant of two orthodontic composites. METHODS: Eighty human premolars were divided into four groups (G1-4) according to curing time and composite: G1 (Transbond XT, 6 s), G2 (Opal Bond MV, 6 s), G3 (Transbond XT, 3 s), and G4 (Opal Bond MV, 3 s). Twenty-four hours after bonding, brackets were subject to a SBS test performed with a universal testing machine. Enamel surface was analyzed by SEM and the amount of adhesive remnant was assessed by the Image J software area calculation tool. Two-way analysis of variance was used for statistical analysis of SBS data, while Friedman and Mann-Whitney post hoc tests were used to analyze data on the amount of adhesive remnant. RESULTS: Time and composite significantly affected SBS (p < 0.001). The 6 s curing showed a higher SBS value (21.56 MPa) in comparison to 3 s curing (15.79 MPa). Transbond XT composite showed a significantly higher SBS value (21.06 MPa) compared to Opal Bond MV (16.29 MPa). After the SBS test, Opal Bond MV showed a significantly greater amount of composite adhered to enamel (p < 0.001). CONCLUSION: Reducing exposure time from 6 to 3 s significantly decreased mean values of SBS, even with the use of a high-power LED unit. Reduction in time did not affect the amount of adhesive remnant.

Evaluation of the load system produced by a single intrusion bend in a maxillary lateral incisor bracket with different alloys.

OBJECTIVES: To evaluate if a 0.5-mm vertical bend applied on an incisor bracket produces movements in other planes and if different wires influence these effects. MATERIALS AND METHODS: An acrylic model of a treated patient with brackets passively bonded was attached to an Orthodontic Force Tester, and a load cell was attached to the left lateral incisor. Thirty 0.019 × 0.025-inch archwires were divided into three groups according to their alloy: SS (stainless steel), B-Ti (beta-titanium), and MF (beta-titanium wire coated with nickel-titanium). Step-bends of 0.5 mm high were placed on the lateral incisor bracket using a universal plier, and the forces and moments in three dimensions were statistically analyzed by analysis of variance and Tukey post hoc test. RESULTS: SS produced a larger force (3.4 N) than the B-Ti (1.41 N) and the MF (0.53 N; P < .001). Lingual forces were produced by the SS (0.82 N) and B-Ti (0.31 N) groups, while in the MF group, the force was insignificant. SS produced a mesial force of 0.24 N, while the B-Ti force was insignificant and MF produced 0.09 N. Groups produced different crown-distal tipping moments (SS = 31.48 N-mm, B-Ti = 11.7 N-mm, and MF = 4.55 N-mm) and different crown-buccal tipping moments. SS produced larger moments (3.63 N-mm) than B-Ti (1.02 N-mm) and MF (0.36 N-mm) wires. A mesial-out rotational moment was observed in all groups (SS = 7.17 N-mm, B-Ti = 3.46 N-mm, and MF = 0.86 N-mm). CONCLUSIONS: A 0.5-mm intrusion bend produced lingual and mesial side effects. In addition to the distal and buccal crown-tipping moments, there was a mesial-out moment. Compared with SS, B-Ti and MF wires produced lower forces. These more flexible wires showed side effects with lesser intensity.

Continuous arch and rectangular loops for the correction of consistent and inconsistent load systems in extruded and tipped maxillary second molars.

INTRODUCTION: The aim of this research was to compare the load systems produced by rectangular loops and continuous arches for the correction of extruded second molars with a mesial inclination (inconsistent system) and a distal inclination (consistent system). METHODS: The maxillary first molar of an acrylic model of a patient, with passive brackets and tubes bonded, was connected to a 3-dimensional load cell of an orthodontic force tester, and the second molar was replaced by its respective tube bonded to a second load cell. The second molar tube was moved 2.5 mm occlusally and tipped 20° mesially and distally, creating an inconsistent force system and a consistent force system. For each situation, ten 0.017 × 0.025-in beta-titanium, 8 × 10-mm rectangular loops were compared with 10 0.014-in nickel-titanium continuous arches. The vertical forces-F(z)-and tipping moments-M(x)-were compared using 4 t tests, at 5%. RESULTS: In the inconsistent group, the rectangular loop produced a larger M(x) in both molars: 2.11 N.mm in the second molar compared with the -0.15 N.mm of the continuous arches. On the first molar, the rectangular loops produced -5.58 N.mm against -2.08 N.mm produced by the continuous arches. The F(z) values produced at the second molar with each system were similar, whereas on the first molar they were different; the rectangular loops produced 0.41N, and continuous arches produced 0.53N. In the consistent group, the rectangular loops produced smaller M(x) values at the second molar (-3.06 N.mm) than did the continuous arch (-4.25 N.mm) (P = 0.01), as well as a smaller F(z) value (-0.52 vs -0.92 N, respectively). At the first molar, the rectangular loops produced smaller M(x) values (-2.32 N.mm) than did the continuous arch (-4.18 N.mm), as well as a smaller F(z) value (0.59 vs 1.10 N). CONCLUSIONS: In the inconsistent group, only the rectangular loop produced a system of force that could correct the second molar. In the consistent system, both group mechanics produced a system of force compatible with the correction of the second molar, but the continuous wire produced larger moments. Both groups showed a tendency for mesial crown tipping of the first molar.

Stability of beta-titanium T-loop springs preactivated by gradual curvature

ABSTRACT Objective: Evaluate changes in the force system of T-Loop Springs (TLS) preactivated by curvature, due to stress relaxation. Methods: Ninety TLSs measuring 6 x 10 mm, produced out with 0.017 x 0.025-in TMA® wire and preactived by gradual curvature, were randomly distributed into nine groups according to time point of evaluation. Group 1 was tested immediately after spring preactivation and stress relief, by trial activation. The other eight groups were tested after 24, 48 and 72 hours, 1, 2, 4, 8 and 12 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment and moment-to-force ratios were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation, in an interbracket distance of 23 mm. Results: The horizontal forces decreased gradually among the groups (p< 0.001) and the moments showed a significant and slow decrease over time among the groups (p< 0.001). All groups produced similar M/F ratios (p= 0.532), with no influence of time. Conclusions: The TLSs preactivated by curvature suffered a gradual deformation over time, which affected the force system, specifically the moments, which affected the horizontal forces produced.

RESUMO Objetivo: avaliar as mudanças no sistema de forças das molas T pré-ativadas por curvatura, devido ao alívio de tensão estrutural. Métodos: noventa molas em forma de "T", medindo 6 mm x 10 mm, confeccionadas com fio de beta-titânio TMA® de 0,017" x 0,025" e pré-ativadas por curvatura gradual, foram distribuídas aleatoriamente em nove grupos, de acordo com o momento de avaliação. O Grupo 1 foi testado imediatamente após a pré-ativação da mola e liberação do estresse, por meio de simulação da ativação. Os outros oito grupos foram divididos conforme o intervalo de tempo testado: após 24, 48 e 72 horas; 1, 2, 4, 8 e 12 semanas. Usando um transdutor de momentos acoplado a um indicador digital para extensometria e adaptado a uma máquina universal de ensaios, as magnitudes da força horizontal, do momento e da proporção momento/força (M/F) foram registradas a cada 0,5 mm de desativação a partir da ativação inicial de 5 mm, utilizando-se uma distância interbraquetes de 23 mm. Resultados: as forças horizontais reduziram-se gradualmente nos grupos (p< 0,001) e o momento apresentou uma queda lenta e significativa ao longo do tempo (p< 0,001). Todos os grupos tiveram proporções M/F semelhantes (p= 0,532), não influenciadas pelo período de tempo. Conclusões: as molas pré-ativadas por curvatura gradual sofreram deformação progressiva ao longo do tempo, o que afetou o sistema de forças - especificamente o momento -, alterando as forças horizontais produzidas.