Comparison of shear bond strength of orthodontic brackets bonded with a universal adhesive using different etching methods

ABSTRACT Objective: The aim of this study was to compare the effects of three enamel etching modes - laser-etch, self-etch and acid-etch (5, 10 and 15 s) - on bracket bonding, using a universal adhesive. Methods: Eighty-four maxillary premolars were randomly divided into seven groups (n=12) based on the etching method and the adhesive used for bracket bonding. After water storage and thermocycling, shear bond strength was measured, and adhesive remnant index scores on debonded enamel were determined. Results: There were significant differences between the seven groups regarding bond strength values (p< 0.001). The highest values were observed in universal adhesive with laser etching group, while Transbond XT with acid or laser etching, and universal adhesive used in self-etch mode demonstrated the lowest bond strength. The universal adhesive with the three different etching times presented with statistically similar results, all showing an improvement in bond strength, compared with Scotchbond universal (SBU)/SE. Conclusions: The universal adhesive evaluated in the present study demonstrated statistically similar bond strengths to conventional orthodontic adhesive in self-etch mode. The bond strength can be improved by adding an initial acid etching or laser conditioning step, although enamel damage was observed in some cases.

RESUMO Objetivo: o objetivo desse estudo foi comparar os efeitos de três métodos de condicionamento do esmalte - condicionamento a laser, autocondicionamento e condicionamento ácido (5, 10 e 15 segundos) - sobre a colagem de braquetes com um adesivo universal. Métodos: oitenta e quatro pré-molares superiores foram divididos aleatoriamente em sete grupos (n=12) de acordo com o método de condicionamento e o adesivo utilizado para a colagem dos braquetes. Após armazenamento em água e termociclagem, a força de colagem foi medida e o índice de adesivo remanescente no esmalte após a descolagem foi determinado. Resultados: houve diferenças significativas entre os sete grupos com relação aos valores de força de colagem (p< 0,001). Os valores mais altos foram observados no grupo com adesivo universal e condicionamento a laser, enquanto o Transbond XP condicionado com ácido ou laser, e o adesivo universal autocondicionante demonstraram as menores forças de colagem. O adesivo universal apresentou resultados estatisticamente semelhantes para os três diferentes tempos de condicionamento ácido, todos mostrando um aumento na força de colagem, em comparação ao Scotchbond Universal. Conclusões: o adesivo universal avaliado no presente estudo demonstrou força de colagem estatisticamente semelhante aos adesivos ortodônticos convencionais do tipo autocondicionante. A força de colagem pode ser aumentada acrescentando-se uma etapa inicial de condicionamento ácido ou com laser, embora danos ao esmalte tenham sido observados em alguns casos.

Cytotoxic Effect of Thymus caramanicus Jalas on Human Oral Epidermoid Carcinoma KB Cells

Abstract Identifying new chemotherapeutic agents with fewer side effects is a major concern for scientists today. Thymus caramanicus Jalas (Lamiaceae family) is one of the species of Thymus that grows wild in different regions of Iran. Traditionally, leaves of this plant are used in the treatment of diabetes, arthritis and cancer. Here was investigated the cytotoxic property of Thymus caramanicus essential oil and extract in human oral epidermoid carcinoma KB cells. Cell viability was measured by MTT and neutral red assays. The cells were exposed to different concentrations of essential oil (0.05-1 µL/mL) and extract (25-150 µg/mL) for 24 h. Doxorubicin was used as anticancer control drug. The data showed that the essential oil (IC50=0.44 µL/mL) and extract (IC50=105 µg/mL) induce potent cytotoxic property. Surprisingly, cytotoxic effects of essential oil and extract of this plant on KB cancer cells were greater than those on normal gingival HGF1-PI1 cell line. In addition, Thymus caramanicus could potentiate the effect of doxorubicin in sub-effective concentrations. The results of the present study indicate that essential oils and extracts of Thymus caramanicus have potential anti-proliferative property on KB cells and can be used as pharmaceutical case study for oral cancer treatments.

Resumo A identificação de novos agentes quimioterápicos com menos efeitos colaterais é uma grande preocupação para os cientistas de hoje. Thymus caramanicus Jalas (família Lamiaceae) é uma das espécies de Thymus que cresce selvagem em diferentes regiões do Irã. Tradicionalmente, as folhas desta planta são utilizados no tratamento da diabetes, artrite e câncer. Aqui investigamos a propriedade citotóxica do óleo essencial e extrato de Thymus caramanicus em células da linhagem celular tumoral humana de carcinoma epidermóide de boca (KB). A viabilidade celular foi medida por ensaios MTT e vermelho neutro. As células foram expostas a diferentes concentrações de óleo essencial (0,05-1 μL/mL) e extrato (25-150 μg/mL) durante 24 h. A doxorrubicina foi utilizada como droga de controle anticâncer. Os dados mostraram que o óleo essencial (IC50 = 0,44 μL/mL) e o extrato (IC50 = 105 μg/mL) induzem uma potente propriedade citotóxica. Surpreendentemente, os efeitos citotóxicos de óleo essencial e extrato desta planta sobre células cancerígenas KB foram maiores que sobre a linhagem celular gengival normal HGF1-PI1. Além disso, Thymus caramanicus poderia potencializar o efeito da doxorrubicina em concentrações sub-efetivas. Os resultados do presente estudo indicam que óleos essenciais e extratos de Thymus caramanicus têm potenciais propriedades anti-proliferativas sobre células KB e podem ser usado como estudos de caso farmacêuticos para tratamentos de câncer bucal

The susceptibility of Streptococcus mutans to antibacterial photodynamic therapy: a comparison of two different photosensitizers and light sources

Streptococcus mutans is the main etiological agent for dental caries. Recently, photodynamic therapy (PDT) has been introduced as a new modality in bacterial decontamination. Objective: This in vitro study was carried out to evaluate the susceptibility of Streptococcus mutans to antibacterial PDT using two different photosensitizers and light sources. Material and Methods: Standard suspensions of S. mutans were exposed to laser light at 662 nm and Radachlorin® or LED 630 nm in combination with Toluidine blue O (TBO). Radiation-only groups, photosensitizer alone, and groups with no treatment were used as controls. Bacterial suspension from each treatment was subcultured onto the surface of Mueller-Hinton agar plates and bacterial growth was assessed. The results were analyzed by analysis of variance and Tukey test (p<0.05). Results: PDT with TBO and Radachlorin® significantly reduced S. mutans viability, whereas no difference was observed between two groups of PDT. In the groups treated just with the photosensitizer or irradiated alone, no significant reduction of S. mutans colonies was observed. Conclusion: S. mutans colonies were susceptible to either 662 nm laser or LED light in the presence of Radachlorin® and TBO respectively with no priority. .