Braquetes cerâmicos impressos em 3D: ensaio mecânico de coeficiente de atrito / Ceramic brackets printed on 3D: mechanical essay on the friction coefficient

Objetivo: Avaliar e comparar o atrito entre braquetes ortodônticos (convencional e impressos) e fio de aço. A hipótese nula (H0) é que a média de forças de atrito sejam iguais entre os grupos. Material e Método: O ensaio mecânico foi realizado com 3 grupos de braquetes distintos. Sendo eles: Grupo de braquetes convencional como referência o ClarityTM Advanced (3M Unitek), comparado com dois grupos de braquetes impressos em impressora 3D o Lightforce White (Lightforce Orthodontics) e Lightforce Translucent (Lightforce Orthodontics). As amostras de cada grupo possuem um N=10; os braquetes usados são referentes ao dente 23 (U23) com slot 0.022 e prescrição MBT. O fio ortodôntico foi o de aço inoxidável (CrNi) com calibre de 0.019"x 0.025". O conjunto braquete/fio, unido por ligadura elastomérica, foi colado ao dispositivo de teste, desenvolvido em CAD e impresso em 3D com resina sensível a luz UV, totalizando 30 amostras. Cada amostra foi adaptada a máquina universal de ensaio (EMIC DL ­ 2000) com deslocamento de 2,0mm e velocidade de 1,0mm/min, para mensurar o atrito causado pelo deslize. A força (N) representada pelo pico de cada amostra e, então, realizados a média e o desvio padrão. A comparação foi realizada em nível de significância α = 0,05. A análise de variância ANOVA foi usada para determinar se houve diferenças entre as amostras e o teste post-hoc Tukey. Resultados: µ=0,121N para o Clarity, µ=0,173N para o Lightforce White e µ=0,189N para o Lightforce Translucent. Conclusão: Os braquetes impressos não apresentaram diferença significativa entre eles, porém houve uma pequena diferença para os braquetes do grupo controle que apresentaram uma resistência menor ao deslize do arco (AU)

Purpose: To evaluate and compare the friction between orthodontic brackets (conventional and imprinted) and steel wire. The null hypothesis (H0) is that the average friction forces between the groups are equal. Material and method: The mechanical test was performed with 3 different groups of brackets. These are: Conventional bracket group as reference, ClarityTM Advanced (3M Unitek), compared to two groups of 3D printer printed brackets, Lightforce White (Lightforce Orthodontics) and Lightforce Translucent (Lightforce Orthodontics). The samples from each group have an N=10, and the brackets used are for tooth 23 (U23) with slot 0.022 and MBT prescription. The orthodontic wire was stainless steel (CrNi) with a thickness of 0.019" x 0.025". The bracket/wire set, connected by an elastic ligature, was bonded to the test fixture, which was designed in CAD and 3D printed with UV light-sensitive resin. A total of 30 specimens were fabricated. Each specimen was mounted on a universal testing machine (EMIC DL - 2000) with a displacement of 2.0 mm and a speed of 1.0 mm/min to measure the friction caused by the slide. The force (N) represented by the peak value of each sample, mean and standard deviation were calculated. The comparison was performed with a significance level of α = 0.05. The ANOVA analysis of variance was used to determine if there were differences between samples, and the Tukey test was performed post hoc. Results: µ=0.121N for Clarity, µ=0.173N for Lightforce White, and µ=0.189N for Lightforce Translucent. Conclusion: The printed brackets did not show significant differences. However, there was a small difference in the brackets of the control group, which showed less resistance to arch wire slippage (AU)

Producción científica sobre el abordaje de la fricción en ortodoncia. Estudio de revisión con indicadores bibliométricos / Scientific production on friction in orthodontics. Review study with bibliometric indicators

Objetivo: analizar la producción de literatura científica respecto a la fricción en ortodoncia en los últimos 10 años, a través del estudio de indicadores bibliométricos, tales como: producción anual de artículos, revistas; autores, cooperación entre autores, países que cooperan, instituciones asociadas a las investigaciones, análisis de citas y co-ocurrencia. Métodos: se realizó un estudio bibliométrico descriptivo, retrospectivo de las bases de datos Web of Science y Pubmed, con una ventana de tiempo de 2010 a 2019. Luego de identificar todos los artículos sobre fricción en ortodoncia, se revisaron las variables de producción anual de artículos, revistas, autores, cooperación, países, instituciones, análisis de citas y co-ocurrencia. Para el análisis se utilizó Excel 2013 y VOSviewer 1.6.15, este último es un software gratuito para el análisis de datos bibliométricos. Resultados: para ambas bases de datos, el año de mayor producción en el tema fue 2015; la revista identificada con mayor cantidad de artículos fue Angle Orthodontics; Bourauel Christoph es el principal autor. Brasil fue el país con más publicaciones asociadas a este tema. Las instituciones que más publicaron para Web of Science y Pubmed fueron la Universidad de Bonn y la Universidad Nacional de Seoul. Respecto al análisis de co-ocurrencia, en ambas bases se encontró como variable común el bracket de autoligado, movimiento, tratamiento, sistema, y superficie. Conclusión: la actual producción de publicaciones sobre la fricción en ortodoncia indica una pobre producción de publicaciones en la temática. De esta manera, se destaca que la investigación en fricción sigue en desarrollo gracias a un grupo mínimo de científicos productivos que abordan aspectos que podrían ser de interés para otros investigadores.

Objective: To analyze with some bibliometric indicators (annual production of articles, journals, authors, cooperation, countries, institutions, citation analysis and co-concurrency) production in the scientific literature on the subject of friction in orthodontics over the past 10 years. Methods: A descriptive, retrospective bibliometric study of two databases Web of Science and PubMed with time window 2010 to 2019 was performed. All articles on friction in orthodontics were identified and the variables of annual article production, journals, authors, cooperation, countries, institutions, citation analysis and co-occurrence were reviewed. Excel 2013, VOSviewer 1.6.15 which is a free software for bibliometric data analysis was used for the analysis. Results: The year of the highest production on the subject since the period studied was 2015 and the magazine with the most articles is the Angle Orthodontics for both databases. Bourauel Christoph is the main author. Brazil is the country with the most publications. Among the institutions that publish the most for Web of Science is the University of Bonn and Seoul National University for Pubmed. In co-occurrence analysis, it was found in common for both self-ligating bracket, movement, treatment, system, and surface databases. Conclusion: There is an output of publications on friction in orthodontics that indicates little relevance to the current topic. In this way it is emphasized that frictional research is still in development with a minimal group of productive scientists in aspects that may be of interest to other researchers.

Sibilant Fricative Merging in Taiwan Mandarin: An Investigation of Tongue Postures using Ultrasound Imaging.

In Taiwan Mandarin, retroflex [ʂ] is allegedly merging with dental [s], reducing the traditional three-way contrast between sibilant fricatives (i.e., dental [s]-retroflex [ʂ]-alveopalatal [ɕ]) to a two-way contrast. Most of the literature on the observed merging focuses on the acoustic properties and perceptual identification of the sibilants, whereas much less attention has been drawn to the articulatory evidence accounting for the aforementioned sibilant merging. The current study employed ultrasound imaging techniques to uncover the tongue postures for the three sibilant fricatives [s, ʂ, ɕ] in Taiwan Mandarin occurring before vowels [a], [ɨ], and [o]. Results revealed varying classes of the [s-ʂ] merger: complete merging (overlap), no merging (non-overlap), and context-dependent merging (context-dependent overlap, which only occurred before [a]). The observed [s-ʂ] merger was also confirmed by the perceptual identification by trained phoneticians. Center of gravity (CoG), a reliable spectral moment of identifying different sibilant fricatives, was also measured to reflect the articulatory-acoustic correspondence. Results showed that the [s-ʂ] merger varies across speakers and may also be conditioned by vowel contexts and that articulatory mergers may not be entirely reflected in CoG values, suggesting that auxiliary articulatory gestures may be employed to maintain the acoustic contrast.

Pain Perception and Rate of Canine Retraction Through Self-Ligating Brackets and Conventional Elastomeric Ligation System: A Split Mouth Study

Abstract Objective: To evaluate the rate of tooth movement and the pain perception via self-ligating (SL) and conventional elastomeric ligation brackets (CB) system. Material and Methods: This study has been conducted at the Orthodontic Department of Baqai Dental College, Baqai Medical University. The sample size of this study comprised 40 patients, falling between the age of 12-30 years without any sex discrimination. Shapiro-Wilk was used to check the distribution of data. Non-parametric Mann Whitney U test was applied to evaluate the pain associated with SL and CB brackets system. To analysis the canine retraction Wilcoxon test was applied for the comparison of CB and SL brackets system. For all statistical analyses, the p-value of <0.05 was considered significant. Results: Pain level associated with retraction via CB and SL shows significant differences. However, the rate of canine retraction via CB and SL shows no significant differences at stages T0-T1 and T1-T2. However, stage T2-T3 shows a significant difference. Conclusion: As pain during orthodontic treatment is mostly associated with the level of compression of the periodontal ligament, it may be hypothesized that lower frictional forces generate less compression of the periodontal ligament and blood vessels, and so alter the type of pain experienced.

Evaluation of friction on self-ligating and conventional brackets associated with different types of archwires submitted to sliding mechanics

Aim: The aim of this study was to verify the frictional force during sliding mechanics in orthodontic tooth movement, using conventional metal brackets of the active and passive self-ligating types with stainless steel and copper nickel titanium archwires. Methods: This experimental in vitro study was conducted with conventional metal (Morelli, Sorocaba, SP, Brazil) brackets, active self-ligated (SLI Morelli, Sorocaba, SP, Brazil) and passive self-ligated (SLP Morelli, Sorocaba, SP, Brazil), with slot 0.022 x 0.028 inches and Roth prescription. The brackets were tested with rectangular section 0.019 x 0.025 inch copper nickel titanium and stainless steel archwires. For each type of bracket, 10 sets of plate/bracket/archwire segment (n=10) were fabricated. Non-parametric Kruskal Wallis and Dunn tests were used for comparison between types of brackets and Wilcoxon tests for comparison between types of archwires. Results: The results showed that the frictional force values were higher with copper nickel titanium than with stainless steel archwires (p<0.05). When copper nickel titanium archwires were used, the active self-ligating brackets showed higher frictional force values than the other types, followed by the conventional brackets. Lower frictional force values were observed with passive self-ligating brackets. For stainless steel archwires, no difference was observed between conventional and active self-ligating brackets, the passive self-ligating type presented lower frictional force values than the others. Conclusion: It was concluded that the higher frictional force was observed when active self-ligating brackets were associated with copper nickel titanium archwires. Lower frictional force was verified between passive self-ligating brackets combined with stainless steel archwires

Avaliação in vitro da força de atrito em bráquetes metálicos de aço inoxidável / In vitro stainless steel metal brackets frictional force assessment

O objetivo do estudo foi comparar a força de atrito de três diferentes marcas de bráquetes convencionais (prescrição Roth) com fio de aço inoxidável 0.019" x 0.025". Num total de 60 bráquetes metálicos de segundos pré-molares superiores com prescrição Roth, sendo 20 bráquetes do modelo Standart (Morelli, São Paulo, Brasil), 20 bráquetes do modelo Agile (Abzil, São Paulo, Brasil) e 20 bráquetes do modelo Synergy (Rock Mountain Orthodontics, Colorado, EUA), slot 0.022" x 0.028", foram colados em um cilindro metálico e posteriormente tracionado por uma máquina Universal Instron DL 100KN para tração (EMIC, Paraná, Brasil), com velocidade de 10 mm/min a uma distância de 10 mm. A análise estatística empregou o teste de Kruskal-Wallis com nível de significância de 5%. Os bráquetes da marca Abzil demostraram o maior valor médio de força de atrito (1,5N) em relação aos bráquetes das outras marcas testadas. Os bráquetes da marca Morelli demostraram um valor intermediário, significativamente diferente, em relação às demais marcas (1,15N), e os bráquetes da marca Rock Mountain Orthodontics, o menor valor médio (0,90N). Os bráquetes da marca Rock Mountain Orthodontics apresentaram o menor valor de força de atrito em relação às outras duas marcas testadas, e os bráquetes da marca Abzil o maior valor. Contudo, não foi observada diferença estatisticamente significativa entre as marcas Morelli e Rock Mountain Orthodontics, no que se refere à força de atrito.(AU)

The objective of this study was to compare frictional force of three different brands of standard brackets with 0.019" x 0.025" stainless steel wire (Roth prescription). A total of 60 conventional upper premolar standard brackets with Roth prescription, 20 Standard brackets (Morelli, São Paulo, Brasil), 20 Agile brackets (Abzil, São Paulo, Brasil), and 20 Synergy brackets (Rock Mountain Orthodontics, Colorado, USA), slot 0.022" x 0.028" were bonded to a metallic cylinder and sequentially tractioned tested for frictional resistance by a Universal Instron DL 100KN machine (EMIC, Paraná, Brasil) for traction, with 10 mm/min speed and 10 mm distance. Statistical analysis employed Kruskal-Wallis test with 5% level of confidence. Abzil brackets demonstrated the highest average frictional force (1,5N) when related to other brands tested. Morelli brackets demonstrated an intermediate value, significantly different (1,5N) in relation to other brands. Rock Mountain Orthodontic brackets demonstrated the smallest mean value (0,90N). Rock Mountain Orthodontics brackets presented the smallest frictional force when compared to the two other brands tested in the study, and Abzil brackets presented the highest value. However, there was no statistical difference between Morelli and Rock Mountain Orthodontics regarding to frictional force.(AU)

Comparison of Frictional Resistance in Conventional Brackets with Different Stainless Steel Wires.

AIM: The aim of the study was to evaluate and compare static and kinetic friction of round (0.018") and rectangular (0.019 × 0.025") stainless steel (SS) wires of different brands with conventional preadjusted edgewise brackets. MATERIALS AND METHODS: Maxillary canine and two bicuspids of 0.022 × 0.028" slot sized MBT prescription (Gemini, 3M Unitek, Monrovia, California) brackets were chosen. The wires selected were 0.018" SS (3M Unitek); 0.018" Australian wire (AJ Wilcock, UK), and 0.019 × 0.025" SS (3M Unitek). The testing was done on Instron 3382. A total of 30 test combinations with three wires were repeated 10 times. The static and kinetic friction was recorded in Newton. The kinetic friction was also recorded in Newton at 3, 5, 7, and 9 mm of movement. One-way analysis of variance (ANOVA) and descriptive statistics were used for comparing the friction. To test the level of significance, multiple comparisons were used within wire in bracket by using post hoc test. RESULTS: Static friction was found to be greater than kinetic in all wires; 0.018" SS (3M) wire exhibited minimum static and kinetic friction; while 0.019 × 0.025" SS (3M) exhibited maximum static friction. Kinetic friction was similar in both 0.018" AJ Wilcock and 0.019 × 0.025" SS but greater than 0.018" SS (3M). CONCLUSION: Least static and kinetic friction was exhibited by 0.018" SS (3M). Kinetic friction was similar in both 0.018" AJ Wilcock and 0.019 × 0.025" SS. CLINICAL SIGNIFICANCE: The study concluded that 0.018" SS (3M) is better for individual canine retraction than the other wires used in the study because it has the least frictional resistance; 0.019 × 0.025" SS (3M) is a better wire for canine retraction than 0.018" AJ Wilcock as we can have a three-dimensional control over tooth movement. When torque control is not a prime requisite, then 0.018" SS (3M) can be used for retraction of incisors instead of 0.018" AJ Wilcock in severely proclined incisor cases.

A biomechanical case study on the optimal orthodontic force on the maxillary canine tooth based on finite element analysis.

Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament (PDL) as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g (100 g=0.98 N) were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 kPa (capillary pressure) and 12.8 kPa (80% of human systolic blood pressure) was considered to be optimal, whereas an absolute strain exceeding 0.24% (80% of peak strain during canine maximal moving velocity) was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces (40-44 g for distal-direction and 28-32 g for labial-direction) were smaller than the translation forces (130-137 g for distal-direction and 110-124 g for labial-direction). In addition, the optimal forces for labial-direction motion (110-124 g for translation and 28-32 g for tipping) were smaller than those for distal-direction motion (130-137 g for translation and 40-44 g for tipping). Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.

Tratamiento de Clase II con Ortodoncia Sistema Damon y gomas intermaxilares en etapas tempranas de tratamiento / Treatment of Class II with Orthodontics Damon System and elastics in early stages of treatment

La técnica ortodóncica de baja fricción utiliza brackets pasivos de autoligado con una serie de arcos superelásticos que mantienen las fuerzas aplicadas sobre las piezas dentarias a nivel de la "biozona o zona fuerza óptima". La utilización de gomas intermaxilares ligeras (2 onzas o 56,68 g) en estos tratamientos, desde etapas iniciales, sobre todo en pacientes en crecimiento, permite obtener resultados muy favorables en cuanto a la resolución de la maloclusión de Clase II. Objetivo: evaluar el tratamiento de Ortodoncia de un paciente Clase II esqueletal con sobremordida, sin realizar exodoncias de premolares y utilizando elásticos intermaxilares en fases iniciales de tratamiento. Materiales y método: se presenta el caso clínico de un paciente de sexo masculino de 11 años, de Clase II esqueletal con sobremordida y apiñamiento dentario anterior superior e inferior moderado, con su diagnóstico y evaluación completos pre y post tratamiento y control y seguimiento al año. El tratamiento se realiza con brackets autoligantes (técnica de Damon). Resultados: se obtiene la corrección completa de la Clase II y la sobremordida, alcanzando los objetivos deseados de estética facial y función, en oclusión y desoclusiones, con buen desarrollo de las basales y conservación de la altura de las corticales alveolares a nivel de los caninos. Conclusión: Mediante los recursos terapéuticos disponibles en la actualidad y evaluando al niño en etapas tempranas, podremos combinar diferentes tratamientos para alcanzar los objetivos propuestos en menor tiempo y con óptimos resultados en una maloclusión de Clase II con sobremordida con biotipo mesofacial (AU)

The low friction orthodontic technique uses passive self-ligating brackets with a series of superelastic arches that maintain the forces applied to the dental pieces at the "Biozone or Optimal Force Zone". The use of inter maxillary light elastics (2 ounces or 56.68 yr.) from the initial stages in growing patients, yields very favorable results in terms of correction of Class II malocclusion. Objective: To assess the orthodontic treatment of a skeletal Class II patient with overbite, without extraction of premolars and using elastic in the early stages of treatment. Materials and methods: an 11 year old male skeletal Class II patient with overbite and moderate crowding in upper and lower anterior teeth, with complete diagnostic and evaluation before and after treatment and with annual control. For the treatment, self-ligating brackets (Damon technique) were employed. The results: Total correction of Class II condition and overbite was obtained. The desired goals of facial aesthetics and correct function were attained in occlusion and desocclusion, as well as development of the osseous basis and conservation of the canine alveolar cortical height. Conclusion: Through the employment of therapeutic resources available at present and following up the child through his developmental stages, it is possible to combine different treatments to achieve the proposed objectives in a shorter time with excellent results in mesofacial type patients with Class II malocclusion and deep overbite (AU)

Estudio en el microscopio electrónico de barrido de los brackets zafiro / Scanning electron microscopic study of the sapphire brackets

El movimiento ortodóncico es el resultado de la aplicación de fuerzas a las piezas dentarias a través de dispositivos diseñados para almacenar energía y devolverla y, así, producir el efecto deseado. El profesional actuante puede confeccionar un diagnóstico e implementar una técnica para concretar un plan de tratamiento y cumplir las satisfacciones estéticas del paciente eligiendo el zafiro como material de innovación. Sin embargo, si el bracket de zafiro no mantiene su integridad estructural en el slot donde se encuentra la información para el movimiento de la pieza dentaria, el ortodoncista debe hacer maniobras compensatorias en busca del movimiento dental óptimo para alcanzar el éxito deseado. El objetivo de este trabajo fue comparar la angulación de las paredes del slot de los brackets de zafiro y el desgaste en la superficie estructural del material en brackets sin uso clínico y utilizados luego de concluir un tratamiento. Para esto, se eligieron brackets de zafiro de todas las piezas dentarias de la arcada del maxilar superior y del inferior con uso y sin uso clínico y fueron observados al microscopio electrónico de barrido ambiental (MEB) FEI ESEM Quanta 200. Las muestras fueron lavadas con alcohol absoluto de 96 % de volumen, cepilladas de manera mecánica y secadas antes de ser introducidas en la cámara del MEB. En la etapa de observación se procedió a la construcción de medidas lineales en la imagen de la ranura del bracket desde una vista sagital. Se obtuvieron una medida interna, una media y una externa, cuyos resultados se analizaron mediante el test de normalidad de Shapiro-Wilk. En conclusión, mediante este estudio se observó que algunos brackets mantuvieron su estructura al inicio y al final de su utilización clínica, y otros presentaron una diferenciación en la medida inicial del grupo de brackets no usados clínicamente, que lleva a determinar un desgaste del ángulo interno del slot producto del deslizamiento del alambre durante el uso clínico.

The orthodontic movement is the result of the application of forces to the dental pieces through devices designed to store energy and return it and so to produce the desired effect. The acting professional can make a diagnosis and implement a technique to carry out a treatment plan and meet the aesthetic satisfactions of the patient choosing sapphire as an innovation material. However, if the sapphire bracket does not maintain its structural integrity in the slot where the information for the movement of the tooth is located, the orthodontist must make compensatory maneuvers in search of optimal dental movement to achieve the wanted success. The objective of this work was to compare the angulation of the sapphire brackets slot walls and the wear on the structural surface of the brackets material without clinical use and used after completing a treatment. For this, sapphire brackets were selected from all teeth of the upper and lower jaw arches with use and without clinical use and were observed under the environmental scanning electron microscope (ESEM) FEI ESEM Quanta 200. Samples were washed with absolute alcohol at 96% vol, mechanically brushed and dried before being introduced into the MEB chamber. In the observation phase it was carried out the construction of linear measurements in the image of the bracket slot from a sagittal view. They were obtained an internal, an average and an external measurements which results were analyzed by the Shapiro-Wilk Normality Test. In conclusion, through this study it was observed that some brackets maintained their structure at the beginning and end of their clinical use and others presented a differentiation in the initial measurement of the group of not used clinically brackets that leads to determine a wear of the internal angle of the slot owing to the sliding of the wire during clinical use.

The Role of Oral Cavity Biofilm on Metallic Biomaterial Surface Destruction-Corrosion and Friction Aspects.

Metallic biomaterials in the oral cavity are exposed to many factors such as saliva, bacterial microflora, food, temperature fluctuations, and mechanical forces. Extreme conditions present in the oral cavity affect biomaterial exploitation and significantly reduce its biofunctionality, limiting the time of exploitation stability. We mainly refer to friction, corrosion, and biocorrosion processes. Saliva plays an important role and is responsible for lubrication and biofilm formation as a transporter of nutrients for microorganisms. The presence of metallic elements in the oral cavity may lead to the formation of electro-galvanic cells and, as a result, may induce corrosion. Transitional microorganisms such as sulfate-reducing bacteria may also be present among the metabolic microflora in the oral cavity, which can induce biological corrosion. Microorganisms that form a biofilm locally change the conditions on the surface of biomaterials and contribute to the intensification of the biocorrosion processes. These processes may enhance allergy to metals, inflammation, or cancer development. On the other hand, the presence of saliva and biofilm may significantly reduce friction and wear on enamel as well as on biomaterials. This work summarizes data on the influence of saliva and oral biofilms on the destruction of metallic biomaterials.

A biomechanical case study on the optimal orthodontic force on the maxillary canine tooth based on finite element analysis / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament (PDL) as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g (100 g=0.98 N) were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 kPa (capillary pressure) and 12.8 kPa (80% of human systolic blood pressure) was considered to be optimal, whereas an absolute strain exceeding 0.24% (80% of peak strain during canine maximal moving velocity) was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces (40-44 g for distal-direction and 28-32 g for labial-direction) were smaller than the translation forces (130-137 g for distal-direction and 110-124 g for labial-direction). In addition, the optimal forces for labial-direction motion (110-124 g for translation and 28-32 g for tipping) were smaller than those for distal-direction motion (130-137 g for translation and 40-44 g for tipping). Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.

Sliding resistance of rectangular vs. beveled archwires in two self-ligating brackets: a finite element study

The aim of this study was to use a 3D finite element method (FEM) to compare the sliding resistance of 0.019"x0.025" stainless steel conventional archwires versus 0.019"x0.025" stainless steel beveled archwires in active (InOvation ® Dentsply) and passive (SmartClip®, 3M) selfligating brackets with 0.022" x 0.028" slots . A model was designed for each kind of bracket archwire system and the following parameters were introduced in the models: friction coefficient calculated for stainless steel bracketwire: 0.7 µm; Poisson ratio for stainless steel wire: 0.3, and elastic module: 205 GPa for bracket and 190 GPa for archwire. Static structural analysis was applied for homogeneous, linear and isotropic properties considering contacts between wire and bracket as frictional. The results indicate that the beveled archwire generates less stress than the rectangular wire in SmartClip® and InOvation ® brackets. Comparing brackets, SmartClip® generated less stress than InOvation ®. It is concluded that beveled rectangular arch wires provide the advantage of reduced sliding resistance, which is better in some clinical situations to improve orthodontic mechanics (AU)

El objetivo de este artículo fue comparar con el método tridimensional de elementos finitos (MEF) el comportamiento de la resistencia al deslizamiento expresado en esfuerzos de arcos de acero inoxidable 0.019"x0.025" convencionales y arcos de acero inoxidable con bisel de 0.019"x0.025" en brackets de autoligado slot 0.022" x 0.028" activo (InOvation ® "R" Dentsply) y pasivo (SmartClip® 3M). Se diseñó un modelo de los brackets de autoligado InOvation® "R" Dentsply, SmartClip® 3M y de los arcos de acero inoxidable convencionales y arcos de acero inoxidable con bisel, el análisis se calculó con el coeficiente de fricción para el bracket de acero inoxidable con el del arco de acero inoxidable: µ 0.7. La relación de Poisson 0.3 para el arco de acero inoxidable. El módulo de elasticidad del bracket: 205 GPa y del arco: 190 GPa. La aplicación del método se realizó para un análisis estructural estático con condiciones de material homogéneas, lineales e isotrópicas y con contactos de tipo fricción entre el arco y el bracket. Se observó que el arco biselado generó menos esfuerzo que el arco rectangular en el bracket SmartClip® y en el bracket InOvation ® "R", siendo el SmartClip® en el que se generó menor esfuerzo. Se encontró que existe una ventaja en el uso de los arcos rectangulares con bisel ya que presentan menor resistencia al deslizamiento optimizando en algunas situaciones clínicas las mecánicas ortodónticas (AU)

Comparison of friction forces between stainless orthodontic steel brackets and TiNi wires in wet and dry conditions.

In sliding mechanics, frictional force is an important counter-balancing element to orthodontic tooth movement, which must be controlled in order to allow application of light continuous forces. The purpose of this study was to compare the frictional forces between a stainless steel bracket and five different wire alloys under dry and wet (artificial saliva) conditions. TiNi, TiNiCu, TiNiCo, commercial wires A and commercial wires B with equal dimensions of 0.016×0.022'' were tested in this experiment. The stainless steel bracket was chosen with a slot dimension of 0.022''. Micro-hardness of the wires was measured by the Vickers micro-hardness test. Surface topography of wires was measured by an optical microscope and quantified using surface roughness testing. Static and kinetic friction forces were measured using a custom-designed apparatus, with a 3-mm stretch of wire alloy at a crosshead speed of 1mm/min. The static and dynamic frictions in the wet condition tended to decrease more slowly than those in the dry condition. Therefore, the friction of TiNiCu and commercial wires B would increase. Moreover, these results were associated with scarred surfaces, i.e. the increase in friction would result in a larger bracket microfracture. From the results, it is seen that copper addition resulted in an increase in friction under both wet and dry conditions. However, the friction in the wet condition was less than that in dry condition due to the lubricating effect of artificial saliva.

Characterization of the coatings covering esthetic orthodontic archwires and their influence on the bending and frictional properties.

OBJECTIVE: To analyze the coatings covering esthetic orthodontic wires and the influence of such coatings on bending and frictional properties. MATERIALS AND METHODS: Four commercially available, coated esthetic archwires were evaluated for their cross-sectional dimensions, surface roughness (Ra), nanomechanical properties (nanohardness, nanoelastic modulus), three-point bending, and static frictional force. Matched, noncoated control wires were also assessed. RESULTS: One of the coated wires had a similar inner core dimension and elasticity compared to the noncoated control wire, and no significant differences between their static frictional forces were observed. The other coated wires had significantly smaller inner cores and lower elasticity compared to the noncoated wires, and one of them showed less static frictional force than the noncoated wire, while the other two coated wires had greater static frictional force compared to their noncoated controls. The dimension and elastic modulus of the inner cores were positively correlated (r = 0.640), as were frictional force and total cross-sectional (r = 0.761) or inner core (r = 0.709) dimension, elastic modulus (r = 0.777), nanohardness (r = 0.802), and nanoelastic modulus (r = 0.926). The external surfaces of the coated wires were rougher than those of their matched controls, and the Ra and frictional force were negatively correlated (r = -0.333). CONCLUSIONS: Orthodontic coated wires with small inner alloy cores withstand less force than expected and may be unsuitable for establishing sufficient tooth movement. The frictional force of coated wires is influenced by total cross-section diameter, inner core diameter, nanohardness, nanoelastic modulus, and elastic modulus.

Evaluation of frictional resistance and surface characteristics after immersion of orthodontic brackets and wire in different chemical solutions: A comparative in vitrostudy.

AIM: To evaluate the changes of static and kinetic frictional forces between the brackets and wires following exposure to a soft drink, acidic food ingredient, and acidulated fluoride prophylactic agents. MATERIALS AND METHODS: Two types of Roth prescription mandibular incisor brackets were used: 3M Unitek Victory stainless steel (SS) brackets (n = 40) and Transcend 6000 polycrystalline alumina (PCA) brackets (n = 40) as well as eighty 0.019 × 0.025" dimension ortho technology SS wires of 50 mm length each. Subsequently, brackets tied with SS wires divided into eight subgroups (n = 10) and were immersed in vinegar (pH = 3.5 ± 0.5), Pepsi ® (pH = 2.46), Colgate Phos-Flur mouth rinse (pH = 5.1), and artificial saliva (control group pH = 7) for 24 h. Changes in surface morphology under scanning electron microscope ×1000, surface roughness (Ra) with surface profilometer (single bracket and single wire from each subgroup), and frictional resistance using universal testing machine were evaluated. RESULTS: Highest mean (standard deviation) static frictional force of 2.65 (0.25) N was recorded in Pepsi ® followed by 2.57 (0.25) N, 2.40 (0.22) N, and 2.36 (0.17) N for Vinegar, Colgate Phos-Flur mouth rinse, and artificial saliva groups, respectively. In a similar order, lesser mean kinetic frictional forces obtained. PCA brackets revealed more surface deterioration and higher frictional force values than SS brackets. A significant positive correlation was observed between frictional forces and bracket slot roughness (r = 0.861 and 0.802, respectively, for static and kinetic frictional forces, p < 0.001 for both) and wire roughness (r = 0.243 and 0.242, respectively, for static and kinetic frictional forces, p < 0.05 for both). CONCLUSIONS: Findings may have long-term implications when acidic food substances are used during fixed orthodontic treatment. Further, in vivo studies are required to analyze the clinical effect of acidic mediums in the oral environment during orthodontic treatment.

Fricción en ortodoncia / Friction in orthodontic

La mecánica de deslizamiento es muy utilizada durante el tratamiento ortodóntico. Una de las desventajas de esta mecánica es l a fricción generada entre la interfaz del bracket y del arco, lo que puede reducir la cantidad de movimiento deseado. Debido a la aplicación y la gran aceptación de este tipo de mecanismos, la fricción en ortodoncia es de interés tanto para los ortodoncistas e investigadores en ortodoncia. El objetivo del presente trabajo fue, realizar una revisión de la literatura científica sobre "Fricción", y explicar cómo la fricción afecta al movimiento ortodóntico de los dientes, con una aproximación a sus implicancias clínicas, así como la evolución de los materiales dentales y sus propiedades en cuanto a la resistencia al deslizamiento. Describimos las propiedades físicas de fricción, los tipos de fricción, los factores biológicos, elementos que influyen en la fricción: material de ligadura, alambres y tipos de brackets. También describimos la fricción en las diferentes etapas del tratamiento ortodóntico: alineación y nivelación (fase inicial), cierre de espacios (fase intermedia), y finalización (fase final). La fricción en ortodoncia, representa un reto clínico para los ortodoncistas, porque los altos niveles de fricción pueden reducir la eficacia de la mecánica, disminuir la eficiencia delos dientes y complicar aún más el control de anclaje. La presente revisión de literatura busca aclarar los conceptos de fricción, buscando las condiciones ideales para realizar el movimiento dentario en la práctica diaria de la ortodoncia, seleccionando los materiales y aparatos adecuados, para aplicarlos en forma eficiente, eficaz y efectiva en la búsqueda de las condiciones ideales para el éxito del tratamiento ortodóntico. (AU)

The sliding mechanics is used during orthodontic treatment. A disadvantage of this mechanical friction is generated in the bra cket and interfacez of arc, which can reduce the amount of desired movement. Due to the wide acceptance and implementation of these mechanisms, friction in orthodontics has been of interest to both clinicians and scientists. The aim of this paper is a review of the scientific literature on "Friction" and explains how friction affects the orthodontic movement of teeth, with an approach to its clinical implications, and the evolution of dental materials and their properties regarding the resistance to sliding. Describes the physical properties of friction, friction rate, biological factors, and elements influencing the friction: ligature material, wires and brackets types. We also describe the friction in the different stages of orthodontic treatment: alignment and leveling (initial phase), space closure (intermediate phase), and end (final phase). The friction in orthodontics represents a clinical challenge for orthodontists, because high levels of friction can reduce the effectiveness of mechanical efficiency decrease teeth and further complicate anchorage control. This paper seeks to clarify the concepts of friction, looking for the ideal conditions for tooth movement in daily practice oforthodontics, selecting materials and equipment suitable for application in an efficien t, effective and efficient in finding the ideal conditions for orthodontic treatment success. (AU)

Comparison of frictional resistance among conventional, active and passive selfligating brackets with different combinations of arch wires: a finite elements study.

The aim of this study was to compare frictional resistance among conventional, passive and active selfligating brackets using Finite Elements Analysis (FEA). Seventynine (79) slide tests were performed by combining an upper first bicuspid conventional bracket, 0.018" stainless steel wires and 0.010" ligature by means of an INSTRON 3345 load system to obtain average maximum static frictional resistance (MSFR). This value was compared to the FR (frictional resistance) obtained by simulation of a slide of the same combination by FEA following conventional bracket modeling by means of Computer Aided Design (CAD). Once the FEA was validated, bracket CADs were designed (upper right first bicuspid conventional, active and passive selfligating bracket) and bracket properties calculated. MSFR was compared among conventional, active and passive selfligating brackets with different alloys and archwire cross sections such as 0.018", 0.019" x 0.025"and 0.020" x 0.020". Passive selfligating brackets had the lowest MSFR, followed by conventional brackets and active selfligating brackets. In conventional brackets, a 0.018" archwire produced a linear pattern of stress with maximum concentration at the center. Conversely, stress in 0.020 x 0.020" and 0.019 x 0.025" archwires was distributed across the width of the slot. The highest normal forces were 1.53 N for the 0.018" archwire, 4.85 N for the 0.020 x 0.020" archwire and 8.18 N for the 0.019 x 0.025" archwire. Passive selfligating brackets presented less frictional resistance than conventional and active selfligating brackets. Regardless of bracket type, greater contact area between the slot and the archwire and the spring clip increased frictional resistance.

El objetivo de este estudio fue comparar la resistencia friccional entre brackets convencionales, de autoligado pasivo y activo por medio del método de elementos finitos (MEF). Se realizaron setenta y nueve (79) deslizamientos combinando brackets convencionales de primer bicúspide superior con arcos de acero de 0,018" y ligadura metálica de 0,010" en una máquina INSTRON 3345, obteniendo el promedio de la resistencia estática máxima (REM). Este valor fue comparado con la resistencia friccional obtenida por simulación de un deslizamiento de la misma combinación por medio de MEF previo diseño asistido por computador (CAD) del bracket convencional. Una vez se validó MEF, se realizaron diseños CAD de los brackets (convencional, autoligado activo y pasivo de primer bicúspide superior derecho) y cálculos de sus propiedades. Se realizó una comparación entre brackets convencionales, brackets de autoligado activo y pasivo con diferentes aleaciones y secciones cruzadas de alambre 0.018", 0.019" x 0.025" y 0.020" x 0.020". Los brackets de autoligado pasivo mostraron la menor REM, seguidos de los brackets convencionales y finalmente los brackets de autoligado activo. En los brackets convencionales, el arco de 0,018" produjo un patrón lineal de stress en el fondo de la ranura, con su máxima concentración en el centro. Por el contrario, los arcos de 0.020" x 0.020" y 0.019 x 0.025" tuvieron una distribución de esfuerzos a través del ancho de la ranura. La mayor fuerza normal en los brackets convencionales fue para el arco 0.019"x 0.025" (8.18N), seguido por el arco 0.020 x 0.020" (4.85N) y finalmente el arco 0.018" (1.53N). Los brackets de autoligado pasivo presentaron menos resistencia friccional que los brackets convencionales y autoligado activo respectivamente. Independiente del tipo de bracket, una mayor área de contacto entre la ranura del bracket y el arco, y el spring clip aumentaron la resistencia friccional.

Understanding the basis of space closure in Orthodontics for a more efficient orthodontic treatment.

INTRODUCTION: Space closure is one of the most challenging processes in Orthodontics and requires a solid comprehension of biomechanics in order to avoid undesirable side effects. Understanding the biomechanical basis of space closure better enables clinicians to determine anchorage and treatment options. In spite of the variety of appliance designs, space closure can be performed by means of friction or frictionless mechanics, and each technique has its advantages and disadvantages. Friction mechanics or sliding mechanics is attractive because of its simplicity; the space site is closed by means of elastics or coil springs to provide force, and the brackets slide on the orthodontic archwire. On the other hand, frictionless mechanics uses loop bends to generate force to close the space site, allowing differential moments in the active and reactive units, leading to a less or more anchorage control, depending on the situation. OBJECTIVE: This article will discuss various theoretical aspects and methods of space closure based on biomechanical concepts.

Understanding the basis of space closure in Orthodontics for a more efficient orthodontic treatment

ABSTRACT Introduction: Space closure is one of the most challenging processes in Orthodontics and requires a solid comprehension of biomechanics in order to avoid undesirable side effects. Understanding the biomechanical basis of space closure better enables clinicians to determine anchorage and treatment options. In spite of the variety of appliance designs, space closure can be performed by means of friction or frictionless mechanics, and each technique has its advantages and disadvantages. Friction mechanics or sliding mechanics is attractive because of its simplicity; the space site is closed by means of elastics or coil springs to provide force, and the brackets slide on the orthodontic archwire. On the other hand, frictionless mechanics uses loop bends to generate force to close the space site, allowing differential moments in the active and reactive units, leading to a less or more anchorage control, depending on the situation. Objective: This article will discuss various theoretical aspects and methods of space closure based on biomechanical concepts.

RESUMO Introdução: O fechamento de espaços é um dos processos mais desafiadores na Ortodontia e requer uma compreensão sólida de conceitos biomecânicos, a fim de se evitar efeitos colaterais indesejáveis. Compreender o fundamento biomecânico do fechamento de espaços possibilita uma melhor definição das opções de ancoragem e tratamento, por parte dos clínicos. Apesar de haver uma variedade de desenhos de aparelhos ortodônticos, o fechamento de espaços pode ser realizado por meio da mecânica com atrito ou sem atrito, e cada técnica apresenta vantagens e desvantagens. A mecânica com atrito, ou mecânica de deslizamento, é atraente em virtude de sua facilidade, o espaço é fechado por meio do uso de elásticos ou molas helicoidais, que produzem força, fazendo com que os braquetes deslizem no arco ortodôntico. Por outro lado, a mecânica sem atrito se utiliza de dobras em alças para gerar força para fechar o espaço, possibilitando momentos diferenciais nas unidades ativa e reativa, induzindo a uma ancoragem mais ou menos controlada, dependendo da situação. Objetivo: o presente artigo discutirá vários aspectos teóricos e métodos de fechamento de espaços, baseando-se em conceitos biomecânicos.