Evaluation of the force generated by gradual deflection of orthodontic wires in conventional metallic, esthetic, and self-ligating brackets

ABSTRACT Objective: The purpose of this study was to evaluate the deflection forces of Nitinol orthodontic wires placed in different types of brackets: metallic, reinforced polycarbonate with metallic slots, sapphire, passive and active self-ligating, by assessing strength values variation according to gradual increase in wire diameter and deflection and comparing different combinations in the different deflections. Material and Methods: Specimens were set in a clinical simulation model and evaluated in a Universal Testing Machine (INSTRON 3342), using the ISO 15841 protocol. Data were subjected to One-way ANOVA, followed by Tukey tests (p<0.05). Results: Self-ligating brackets presented the most similar behavior to each other. For conventional brackets there was no consistent behavior for any of the deflections studied. Conclusions: Self-ligating brackets presented the most consistent and predictable results while conventional brackets, as esthetic brackets, showed very different patterns of forces. Self-ligating brackets showed higher strength in all deflections when compared with the others, in 0.020-inch wires.

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements

OBJECTIVE: The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resinmodified glass ionomer cements (RMGICs). MATERIAL AND METHODS: Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. RESULTS: Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. CONCLUSIONS: Except for Ionoseal, all cements provided satisfactory bond strength values. .

The influence of protective varnish on the integrity of orthodontic cements

OBJECTIVE: The aim of the present study was to assess the influence of saliva contamination over the structural strength and integrity of conventional glass-ionomer cements used for cementing orthodontic bands in the absence and presence of a surface-protecting varnish. METHOD: 48 samples were prepared by inserting 3 types of glass-ionomer cements into standardized metallic matrixes of 10 mm of diameter and 2 mm of depth. The cements used were: Meron (VOCO), Ketac-Cem (3M ESPE) and Vidrion C (DFL), all of which comprised groups A, B and C, respectively. Subgroups A1, B1 and C1 comprised samples with no surface protection, whereas subgroups A2, B2 and C2 comprised samples of which surface was coated with Cavitine varnish (SS White), after cement manipulation and application, in order to protect the cement applied. All samples were stored in artificial saliva for 24 hours at 37ºC. A Vickers diamond micro-durometer was used to produce indentations on the non-treated group (non-varnished) and the treated group (varnished). RESULTS: Varnished materials had significantly higher microhardness values in comparison to non-varnished materials. Ketac-Cem had the highest microhardness value among the varnished materials. CONCLUSION: Varnish application is necessary to preserve the cement and avoid enamel decalcification. Glass-ionomer cements should be protected in order to fully keep their properties, thus, contributing to dental health during orthodontic treatment.

OBJETIVO: avaliar a influência da contaminação salivar na resistência estrutural e integridade de cimentos de ionômero de vidro convencionais utilizados para cimentação de bandas ortodônticas na ausência e na presença de um verniz protetor de superfície. MÉTODOS: quarenta e oito corpos de prova foram confeccionados a partir de três cimentos ortodônticos, com auxílio de matrizes metálicas padronizadas com 10mm de diâmetro e 2mm de altura. Os cimentos utilizados foram: Meron (Voco), Ketac-Cem (3M ESPE) e Vidrion C (DFL), compondo os grupos A, B e C, respectivamente. Metade dessas amostras não recebeu nenhum tipo de proteção superficial, constituindo os subgrupos A1, B1 e C1, enquanto, os subgrupos A2, B2 e C2 tiveram suas superfícies isoladas com verniz Cavitine (SS White) após manipulação e aplicação do cimento, com intuito de proteger a superfície do cimento. As amostras foram armazenadas em saliva artificial por 24 horas a 37ºC. Foi realizado um ensaio de microdureza (Vickers) para avaliação da dureza de superfície do grupo não-tratado (sem isolamento) e do grupo tratado (agente protetor). RESULTADOS: os materiais previamente isolados com o verniz obtiveram valores de microdureza significativamente maiores que os não-isolados. O cimento Ketac-Cem apresentou, estatisticamente, a maior microdureza entre os materiais protegidos. CONCLUSÃO: o isolamento com verniz mostrou-se necessário para preservação do cimento e, consequentemente, de sua capacidade de evitar possíveis desmineralizações dentárias. Os cimentos de ionômero de vidro devem ser protegidos para manutenção de sua integridade, contribuindo para saúde dental durante o tratamento ortodôntico.

Evaluation of mechanical properties of five cements for orthodontic band cementation

The aim of this in vitro study was to compare the flexural, compressive and diametral tensile strengths of five cements used in orthodontics for band cementation. Twelve specimens of each cement were tested: 1 - GC Fuji Ortho Band (FJ), GC America Inc.; 2 - Meron (MR), Voco; 3 - Multi-Cure Glass Ionomer Band Cement (MC), 3M Unitek; 4 - Band-Lok (BL), Reliance Orthodontic Products; and 5 - Ketac Cem (KC), 3M ESPE. The results (mean) for diametral tensile strength were: 10.51 MPa (FJ), 9.60 MPa (MR), 20.04 MPa (MC), 42.80 MPa (BL), and 4.08 MPa (KC). The results for compressive strength were (in the same order): 64.50 MPa, 77.71 MPa, 94.21 MPa, 193.88 MPa, and 81.93 MPa. The results for flexural strength were (in the same order): 20.72 MPa, 25.84 MPa, 53.41 MPa, 137.41 MPa, and 20.50 MPa. The statistical analysis was performed by two-way ANOVA and Tukey tests with p-value £ 0.05. In terms of diametral tensile strength, BL showed the highest strength statistically, and MC, the second highest. In terms of compressive tensile strength, BL showed the highest strength statistically, and FJ did not attain the minimum recommended strength. In terms of flexural tensile strength, BL cement was superior to MC, and MR, FJ and KC were equivalent and inferior to BL and MC.

Effect of cement type and water storage time on the push-out bond strength of a glass fiber post

This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers’ instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (α=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage, decreasing thereafter.

Este estudo investigou os efeitos do tipo de cimento e do tempo de armazenamento em água na resistência adesiva ao cisalhamento de pinos de fibra. Pinos de fibra de vidro (Fibrekor, JenericPentron) foram cimentados aos condutos radiculares usando o cimento resinoso autopolimerizável (C&B Cement [CB]), o cimento de ionômero de vidro (Ketac Cem [KC]) ou o cimento de ionômero de vidro modificado por resina (GC FujiCEM [FC]) de acordo com as instruções dos fabricantes. Para cada cimento, os espécimes foram expostos a um dos seguintes tempos de armazenamento em água (n=5): 1 dia (T1), 7 dias (T7), 90 dias (T90) e 180 dias (T180). Os testes de resistência adesiva ao cisalhamento foram realizados após os períodos de armazenamento. Os espécimes controles não foram expostos ao armazenamento em água, mas submetidos ao teste de resistência adesiva ao cisalhamento 10 min após a cimentação do pino. Os dados (MPa) foram analisados usando Kruskal-Wallis e teste de Dunn (α=0,05). O tipo de cimento e o tempo de armazenamento em água afetaram significantemente a resistência adesiva ao cisalhamento (p<0,05). CB apresentou valores de retenção significantemente superiores a KC e FC, independentemente do tempo de armazenamento em água. Esse, por sua vez, aumentou significantemente a resistência adesiva ao cisalhamento em T7 e T90, independentemente do tipo de cimento (p<0,05). Os resultados indicaram que os pinos de fibra cimentados aos condutos radiculares com o cimento resinoso autopolimerizável apresentou a melhor performance adesiva durante todo o período de armazenamento em água de 180 dias. Todos os cimentos apresentaram uma tendência a aumentar a resistência adesiva ao cisalhamento após 7 e 90 dias de armazenamento em água, diminuindo posteriormente.

Evaluation of different sterilization and disinfection methods on commercially made preformed crowns.

The aim of this study was to evaluate the changes caused by different sterilization or disinfection methods on the vestibular surface of four commercially made preformed crowns using stereomicroscopy and scanning electron microscopy (SEM). Preformed crowns (NuSmile Primary Anterior Crown (NSC), Kinder Krowns (KK), Pedo Pearls (PP) and polycarbonate crowns (PC)) were sterilized and/or disinfected by one of the following techniques: no sterilization or disinfection (G1 control group); steam autoclaving at 134 degrees C (30 psi) for 4 min (G2); steam autoclaving at 134 degrees C (30 psi) for 12 min (G3); steam autoclaving at 121 degrees C (15 psi) for 30 min (G4); and ultrasonication in a bath containing 4% Lysetol AF for 5 min at room temperature (chemical disinfection) (G5). Scanning electron micrographs of the crowns were taken before and after their sterilization or disinfection. The changes on the vestibular surface were then scored for the presence or absence of crazing, contour alteration, fracturing, and vestibular surface changes. The data were analyzed statistically using the chi-square test. No changes were observed before and after sterilization or disinfection in the stereomicroscopic evaluation of the vestibular surface of the crowns. However, all methods in which steam autoclaving was used to sterilize the crowns caused significant (P < 0.05) crazing and contour alterations of the vestibular surface of the crowns when they were examined by SEM. Chemical disinfection using an aldehyde-free disinfectant is the preferred method of disinfection for crowns that have been used previously in other dental patients.

Implante endodóntico intraóseo, un recurso a tener en cuenta: biomateriales - biocompatibilidad / Intraosseous endodontic implantation, a resource to be taken into account: biomaterials - biocompatibility

Se ha tratado de utilizar una técnica preconizada hace 50 años atrás que ha sido dejada en desuso por diversas razones. Con el advenimiento de nuevos materiales, estudios más profundos de la biocompatibilidad de los mismos justifican ser tenidos en cuenta en el arsenal terapéutico bucal. Destacamos su uso en aquellos casos de pérdida de tejido dentario ya sea por: alteraciones paradenciales, procesos apicales o la pérdida de la longitud de la raíz por traumatismos, o en casos de estabilización por traumatismos sin fracturas. También justificamos su empleo en forma transitoria o definitiva como complemento durante el período de oseointegración de otros implantes

A comparative study of retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements with stainless steel crowns--an in vitro study.

This study was conducted on 30 extracted human primary molars to assess the retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements. The teeth were embedded in resin blocks and were randomly divided into 3 groups of 10 each. The occlusal surfaces of all teeth were reduced uniformly by 1.0 to 1.5 mm. All mesial, distal undercuts were removed and sharp angles rounded. This was followed by cementing pretrimmed and precontoured stainless steel crowns on each tooth with hand pressure and storing in artificial saliva at 37 degrees C for 24 hours. Retentive strength was tested using Instron Universal Testing Machine. The load was applied starting from a zero reading and gradually increased until the cemented stainless steel crowns showed signs of movement and then the readings were recorded. It was found that retentive strengths of zinc phosphate and glass ionomer cements were statistically better (P < 0.05) when compared to the polycarboxylate cement. Negligible difference (0. 59 kg/cm2) was however observed between zinc phosphate and glass ionomer cements.

Cementado y adhesión en ortodoncia / Cementation and bonding in orthodontics

Hemos desarrollado extensamente lo referido a los ionómeros vítreos porque pensamos que, en su forma tradicional o en las de más reciente desarrollo, es un excelente material que ha mejorado la performance clínica de los antiguos cementos utilizados para el cementado de bandas de ortodoncia