Ion release and surface roughness of silver soldered bands with two different polishing methods: An in-vitro study.

OBJECTIVE: To evaluate the surface roughness and ion release of silver-soldered joints by using two polishing methods. METHODS: 174 orthodontic bands with and without silver-soldered joints were evaluated and divided into three groups: two experimental, with different polishing methods (SP1 and SP2), and one control (SS) composed of bands without silver solder. For ionic release, 50 bands of each group were immersed in saline solution and submitted to atomic absorption spectrophotometry to quantify the amount of Fe, Ni, Cr (in all the three groups), Ag, Cu, Cd, and Zn (in the two experimental groups). A rugosimeter was employed to verify the surface roughness. RESULTS: Ni and Cr were released in higher amounts after soldering. Cd, Ag, Zn, and Cu may be released from silver-soldered bands independently of the polishing method employed. Ag was released in higher amounts from the soldered bands that presented higher surface roughness. CONCLUSIONS: Differences exist in relation to the surface roughness of silver-soldered bands when distinct polishing methods are used. Toxic ions may be released from silver soldered joints and higher surface roughness may cause higher ionic release.

In vivo evaluation of the genotoxic effects of Hyrax auxiliary orthodontic appliances containing silver-soldered joints.

Auxiliary appliances consisting of silver-soldered joints may be present in the patient's oral cavity for a long time. The aim of this study was to investigate, in vivo, the potential genotoxic effects of Hyrax-type maxillary expanders containing silver-soldered joints on the cells of the buccal mucosa. Buccal cells were collected from 20 patients and processed to perform the buccal comet assay (BCA) and the buccal micronucleus cytome (BMCyt) assay, to investigate DNA and chromosomal damage, respectively. For the BCA, patients were evaluated before and 14 days after the appliances were installed. For the BMCyt assay, the patients were evaluated longitudinally; before the insertion of the appliance and after one, six, and twelve months. The BCA showed significant increases in damage frequency and damage index in exfoliated buccal cells, following insertion of the appliance. For the BMCyt assay, the endpoints related to cell proliferation, cell death, and chromosomal damage (micronuclei and nuclear buds) resulted in no significant differences over the 12-month study period. In conclusion, the use of orthodontic appliances containing silver-soldered joints can significantly increase DNA damage as measured by the BCA.

Differences of cytotoxicity of orthodontic bands assessed by survival tests in Saccharomyces cerevisiae.

The aim of this study was to evaluate the cytotoxicity induced by orthodontic bands through survival tests on Saccharomyces cerevisiae, a microorganism that presents several genetic and biochemical characteristics similar to human cells. Three groups of bands were evaluated: silver soldered (SSB), laser soldered (LSB), and bands without any solder (WSB). Yeast cells were directly exposed to the bands and indirectly, when a previous elution of the metals in artificial saliva was performed. The negative control was composed of yeast cells or artificial saliva not exposed to any kind of metal. In the direct exposure experiments, all tested groups of bands induced a slight reduction in yeast viability compared to the control. This effect was more intense for the SSB, although not statistically significant. For the indirect exposure experiments, the SSB induced a statistically significant decrease in cell viability compared to the LSB. There were no significant differences between the survival rates of the negative control and the LSB group in both direct and saliva tests. SSBs were cytotoxic, whilst LSBs were not, confirming that laser soldering may be a more biocompatible alternative for use in connecting wires to orthodontic appliances.

Cytotoxicity and genotoxicity of orthodontic bands with or without silver soldered joints.

Stainless steel bands, with or without silver soldered joints, are routinely used in orthodontics. However, little is known about the toxic biological effects of these appliances. The aims of this study were to evaluate the cytotoxic, cytostatic, genotoxic and DNA damage-inducing effects of non-soldered bands (NSB) and silver soldered bands (SSB) on the HepG2 and HOK cell lines and to quantify the amount of ions released by the bands. The 24-h metallic eluates of NSBs and SSBs were quantified by atomic absorption spectrophotometry. An MTT reduction assay was performed to evaluate the cytotoxicity, alkaline and modified comet assays were employed to measure genotoxicity and oxidative DNA damage effects, and cytokinesis-block micronucleus cytome (CBMN-Cyt) assays were used to verify DNA damage, cytostasis and cytotoxicity. Ag, Cd, Cr, Cu and Zn were detected in SSB medium samples, and Fe and Ni were detected in both the SSB and NSB medium samples. The SSB group induced stronger cytotoxic effects than the NSB group in both evaluated cell lines. NSB and SSB induced genotoxicity as evaluated by comet assays; stronger effects were observed in the SSB group. Both groups induced similar increases in the number of oxidative DNA lesions, as detected by the FPG and Endo III enzymes. Nucleoplasmic bridges, biomarkers of DNA misrepair and/or telomere end fusions, were significantly elevated in the SSB group. The SSB eluates showed higher amounts of Ni and Fe than NSB, and all the quantified ions were detected in SSB eluates, including Cd. The SSB eluates were more cytotoxic and genotoxic than the NSB samples. Based on these results, we propose that other brands, materials and techniques should be further investigated for the future manufacture of orthodontic appliances.

Influência de variáveis metodológicas na resistência de união ao cisalhamento / The influence of the methodological variables on the shear bond strength

OBJETIVO: avaliar a influência de diferentes variáveis metodológicas sobre a resistência de união ao cisalhamento em estudos in vitro. MÉTODOS: foram utilizados 105 incisivos permanentes bovinos, seccionados ao nível do colo dentário. A porção coronária foi inclusa em tubos de PVC, com resina acrílica autopolimerizável, e com face vestibular voltada para cima. Todos os corpos de prova foram preparados para a colagem com profilaxia e condicionamento ácido na região central das coroas, onde foram posicionados braquetes Morelli® de incisivos centrais superiores, com resina Concise® Ortodôntico (3M/Unitek). Foram determinados três grupos de acordo com a variável estudada: (Grupo 1) - meio de armazenamento dos dentes, previamente à inclusão e à colagem, com solução de timol 0,1 por cento (a), água destilada (b) e congelamento (c); (Grupo 2) - velocidade da célula de carga da máquina de ensaio de 0,5 (a), 1,0 (b) e 2,0mm/min (c) e (Grupo 3) - diferentes marcas comerciais de ácidos fosfóricos a 37 por cento, 3M/Unitek (a), AcidGel (b) e Attack Tek (c). Os corpos de prova foram submetidos ao ensaio mecânico de resistência ao cisalhamento através da máquina Emic DL2000®. Os dados foram analisados estatisticamente por meio do Teste t Student para amostras independentes. RESULTADOS: os resultados demonstraram que no Grupo 1 o subgrupo de congelamento apresentou maiores valores em relação aos outros dois subgrupos, porém sem diferença estatisticamente significativa (p > 0,05). No Grupo 2, a força no momento da ruptura foi menor à medida que era aumentada a velocidade da célula de carga, porém sem diferença significativa entre os subgrupos. No Grupo 3, o ácido da 3M/Unitek apresentou a maior média em MPa, no entanto, também sem diferença significativa entre os subgrupos. CONCLUSÕES: conclui-se, portanto, que as variáveis analisadas neste trabalho não apresentaram influência suficiente para determinação de diferenças estatisticamente significativas...

AIM: Evaluate the influence of several methodological variables on the shear bond strength of in vitro studies. METHODS: 105 bovine incisors were sectioned at the cervical level. The coronary portion was included in PVC rings, fulfilled with auto polymerized acrylic resin, with its labial faces turned to the top. All the samples were prepared for bonding, cleaned and acid etched on the central area of the crowns. In this area, central incisors' MorelliÕ brackets were bonded with ConciseÕ (3M/Unitek). Three testing groups were established, according to the studied variable: Group 1 - storage previous to bonding (a-Thymol 0,1 percent; b- distilled water; c- freezing); Group 2 - crosshead speed of the universal testing machine (a- 0,5mm/min; b- 1,0mm/min; c- 2,00mm/min) and Group 3 - commercial brand of 37 percent phosphoric acid (a- 3M/Unitek; b- Acid Gel; c- Attack Tek). The shear bond strength test was performed at the Emic DL2000Õ universal testing machine. Data was analyzed through the Student's t test for independent samples. RESULTS: In Group 1, the freezing group showed the higher values of shear bond strength when compared to the others, although no statistical difference was observed (p>0,05). For Group 2, the higher the crosshead speed, the lower the shear bond strength, with no statistical difference. In Group 3, the 3M/Unitek brand showed the highest average of shear bond strength in MPa, but also no statistical difference was shown. CONCLUSIONS: The variable analyzed in this research had not presented enough influence to determine significant differences between the results.

Biocompatibilidade dos materiais em ortodontia: mito ou realidade? / Biocompatibility of orthodontic materials: myth or reality?

O objetivo deste trabalho é apresentar uma revisão sobre os conceitos relacionados à biocompatibilidade dos materiais empregados em Ortodontia. Fatos relacionados às reações de hipersensibilidade aos diversos materiais ortodônticos são discutidos, sendo apresentadas as condutas recomendáveis nestas situações.

The aim of this paper is to present a review on the biocompatibility of orthodontic materials. Hypersensitivity reactions to these materials are discussed and the recommended conduct in this kind of situation are presented.

Residual monomer of autopolymerized acrylic resin according to different manipulation and polishing methods. An in situ evaluation.

OBJECTIVE: To test the hypothesis that no difference exists in the in situ levels of residual monomer of an autopolymerized acrylic resin, irrespective of the method of manipulation and polishing. MATERIALS AND METHODS: Forty volunteers received the test specimens. The residual monomer was evaluated by means of gas chromatography using methylethylketone as extraction solvent. The samples of autopolymerized acrylic resin were submitted to two methods of manipulation--mass and addition--as well as to two types of polishing-mechanical and chemical. Four test groups were determined according to manipulation and polishing techniques: mass-mechanical; mass-chemical; addition-mechanical; addition-chemical. The data obtained were analyzed by the Student's t-test for paired samples as well as by analysis of variance. RESULTS: Residual methylmethacrylate was verified in high concentrations in the beginning of the testing as well as 24 hours after the test specimens had been worn. Mechanical polishing was associated with lower levels of residual monomer. The mass-mechanical group showed the lowest values. Mechanical polishing was associated with the lowest levels of residual monomer, and the lowest level of all occurred in mass-mechanical group. CONCLUSIONS: The hypothesis is rejected. Variations of residual polymer were associated with variations in the manipulation and polishing, but high concentrations of residual monomer were present in all groups. These concentrations were reduced after 24 hours.

Surface roughness of auto polymerized acrylic resin according to different manipulation and polishing methods: an in situ evaluation.

OBJECTIVE: To test the hypothesis that no differences exists in the in situ level of surface roughness of an auto polymerized acrylic resin irrespective of the method of manipulation and polishing. MATERIALS AND METHODS: Forty volunteers received the test specimens. Surface roughness was evaluated using a rugosimeter. Samples of auto polymerized acrylic resin were submitted to two methods of manipulation--mass and addition--as well as to two types of polishing--mechanical and chemical. Four test groups were designated according to manipulation and polishing techniques: mass-mechanical, mass-chemical, addition-mechanical, and addition-chemical. Five measures of surface roughness were taken from each sample and average surface roughness (Ra) was determined before and 20 days after the samples were worn by the volunteers. The data obtained were analyzed by the Student's t-test for paired samples as well as by analysis of variance. RESULTS: Significant differences in Ra were found between mechanical and chemical polishing. Surface roughness was not influenced by manipulation techniques. Mechanical polishing presented the lowest values of Ra. There was a significant increase in surface roughness after volunteers wore the specimens for 20 days. CONCLUSIONS: The hypothesis is rejected. There were differences on the surface roughness according to the different methods of manipulation and polishing used, but high values of surface roughness were found for all groups. Mechanical polishing showed the lowest values of surface roughness and thus should be preferred.

Formaldeído na odontologia: aspectos antimicrobianos, carcinogênicos e mutagênicos. Um estudo da sua viabilidade na clínica odontológica / Formaldehyde in dentistry: antimicrobial, carcinogenic, and mutagenic aspects. A study of its viability in dentistry

O formaldeído é um medicamento usado na prática odontológica desde o século XVIII. Ele foi um dos agentes medicamentosos mais usados na Odontologia, ao se tratar de terapêutica pulpar. Porém, apesar de apresentar alto índice de sucesso clínico e radiográfico, têm-se dado atenção especial para as propriedades tóxicas deste material. O presente artigo visa revisar a ação do formaldeído sobre os tecidos dentários, enfatizando os aspectos citotóxicos e antimicrobianos, considerando sua ação sobre cultura de células e de bactérias, em diferentes concentrações, e seus efeitos mutagênicos e carcinogênicos. Pode-se concluir que, apesar de ser um eficiente antimicrobiano, o formaldeído apresenta numerosos efeitos citopatológicos, além de ser mutagênico e carcinogênico.

Allergy to auto-polymerized acrylic resin in an orthodontic patient.

This article reports on a 60-year-old woman who had an allergic reaction to methylmethacrylate self-curing acrylic resin during orthodontic treatment. A localized hypersensitive reaction appeared on the palate after an orthodontic retainer was placed. Samples of the acrylic were removed and analyzed with gas chromatography to evaluate the residual monomer level. The residual monomer content was between 0.745% and 0.78%, which did not exceed international standards for this material. Patch tests were performed with several methylmethacrylate resin samples and processed with various techniques; they showed positive reactions. Despite the many alternative products available, self-curing acrylic resin remains widely used because of its low cost, ease of use, and diversity of indications. Orthodontists should be aware that allergic reactions can occur.

Mordida cruzada posterior funcional: uma alternativa de tratamento / Posterior functional crossbite: an alternative of treatment

O objetivo deste trabalho é apresentar uma revisão da literatura sobre mordida cruzada posterior funcional e seu tratamento interceptador, mostrando, a seguir, dois casos clínicos de pacientes tratados na clínica de Graduação de Ortodontia da Faculdade de Odontologia da Universidade Federal do Rio Grande do Sul no período de 2001 a 2003. Nesses pacientes corrigiram-se as inclinações dentárias através de placa ortodôntica superior removível em acrílico com parafuso expansor, adequando as dimensões transversais dos arcos. Entretanto, em função do componente muscular, ambos persistiram desviando a mandíbula durante o fechamento. Houve, então, a necessidade da utilização de outro aparelho ortodôntico removível com uma extensão vertical como guia para o fechamento e, conseqüentemente, para a desprogramação da musculatura. Foi observado que, após a utilização deste aparelho, os pacientes não mais apresentavam um padrão de fechamento mandíbular com desvio. Considerando que as correções das mordidas cruzadas, após o período de tratamento e contenção, são estáveis, está indicada a intervenção o quanto antes, pois, além de permitir o crescimento e o desenvolvimento normais, melhora a mastigação e evita desgastes dentários

Abordagem da lesão de cárie secundária em restaurações adesivas / An approach regarding secondary caries lesion in adhesive restorations

A lesão de cárie secundária é uma das maiores causas associadas à substituição de restaurações adesivas. Entretanto, questiona-se a sua real ocorrência diante da grande dificuldade diagnóstica. Assim o objetivo deste estudo foi analisar na literatura, como a lesão cariosa secundária tem sido abordada. Sugere-se que a lesão seja submetida à mesma avaliação direcionada a uma lesão primária, devendo ser considerado o perfil do paciente com relação à doença cárie

Avaliação das propriedades do cimento de óxido de zinco e isoeugenol / Evaluation of zinc oxide-isoeugenol cement properties

O objetivo deste trabalho foi avaliar o efeito da substituição do eugenol pelo isoeugenol na formulação do cimento de óxido de zinco e eugenol, em relação às propriedades de tempo de presa e espessura de película, devido à comprovada genotoxicidade apresentada pelo eugenol. Utilizou-se o pó do cimento de óxido de zinco e eugenol (Endofil - Dentsply Herpo) e o isoeugenol (98 por cento). Com base na especificação número 57 da Associação Dentária Americana (A.D.A.) foram avaliados o tempo de presa e a espessura de película. Para determinação do tempo de presa, foram confeccionados corpos de prova de diâmetro interno de 10 mm e espessura de 2 mm, que foram levados à estufa a 37ºC. Com o auxílio de uma agulha de Gilmore com 100 g e diâmetro de 2 mm, foi determinado o tempo de presa do material. Foram determinados os seguintes tempos de presa: A - 1h e 8min; B -1h e 10min; C - 1h e 13min. Para determinação da espessura de película, utilizou-se a proporção de 330 mg de óxido de zinco e 110 mg de isoeugenol colocada entre duas placas de vidro que tiveram a sua espessura medida por um micrômetro. O material espatulado foi colocado sobre uma das placas e coberto com a outra. Sbre as placas foi aplicada uma carga de 147 N por 10 minutos. Após este período, as placas com o cimento interposto foram retiradas e novamente foi medida a sua espessura. A diferença entre a primeira e a segunda medida resultou na espessura de película: A - 30 m; B - 26 m; C - 28 m. Com base nos resultados concluiu-se que, quanto à espessura de película, o material foi aprovado pela especificação que exige a espessura máxima de 50 um. Já quanto ao tempo de presa, este foi além dos 10 por cento em relação ao proposto pelo fabricante, no entanto, como nas obturações de canal este tempo não é crítico, seria viável sugerir a substituição proposta considerando as propriedades analisadas