Effect of TiO2 nanoparticles incorporation on antibacterial properties and shear bond strength of dental composite used in Orthodontics

ABSTRACT Introduction: Plaque accumulation and bond failure are drawbacks of orthodontic treatment, which requires composite for bonding of brackets. As the antimicrobial properties of TiO2 nanoparticles (NPs) have been proven, the aim of this study was to evaluate the antimicrobial and mechanical properties of composite resins modified by the addition of TiO2 NPs. Methods: Orthodontics composite containing 0%, 1%, 5% and 10% NPs were prepared. 180 composite disks were prepared for elution test, disk agar diffusion test and biofilm inhibition test to collect the counts of microorganisms on three days, measure the inhibition diameter and quantify the viable counts of colonies consequently. For shear bond strength (SBS) test, 48 intact bovine incisors were divided into four groups. Composites containing 0%, 1%, 5% and 10% NPs were used for bonding of bracket. The bracket/tooth SBS was measured by using an universal testing machine. Results: All concentration of TiO2 NPs had a significant effect on creation and extension of inhibition zone. For S. mutans and S. sanguinis, all concentration of TiO2 NPs caused reduction of the colony counts. Composite containing 10% TiO2 NPs had significant effect on reduction of colony counts for S. mutans and S. sanguinis in all three days. The highest mean shear bond strength belonged to the control group, while the lowest value was seen in 10% NPs composite. Conclusions: Incorporating TiO2 nanoparticles into composite resins confer antibacterial properties to adhesives, while the mean shear bond of composite containing 1% and 5% NPs still in an acceptable range.

RESUMO Introdução: o acúmulo de placa e as descolagens de braquetes são algumas desvantagens presentes no tratamento ortodôntico, no qual se requer o uso de materiais compósitos para a colagem dos braquetes. Objetivo: tendo em vista que as propriedades antimicrobianas das nanopartículas (NPs) de TiO2 já foram confirmadas, o objetivo do presente estudo foi avaliar as propriedades antimicrobianas e mecânicas de resinas compostas modificadas pela adição de NPs de TiO2. Métodos: compósitos ortodônticos contendo 0%, 1%, 5% e 10% de NPs foram preparados. Cento e oitenta discos de compósito foram preparados para o teste de eluição, o ensaio de difusão em ágar por disco, e o ensaio de inibição da formação de biofilme, para se calcular as contagens de microrganismos ao longo de três dias, medir o diâmetro da inibição e, consequentemente, quantificar as contagens de colônias viáveis. Para o teste de resistência da colagem ao cisalhamento (SBS), 48 incisivos bovinos intactos foram divididos em quatro grupos, nos quais os compósitos contendo 0%, 1%, 5% e 10% de NPs foram utilizados para colagem dos braquetes. A SBS da interface braquete/dente foi medida em uma máquina universal de ensaios. Resultados: todas as concentrações de NPs de TiO2 apresentaram efeito significativo na formação e na extensão da zona de inibição. Para o S. mutans e o S. sanguinis, todas as concentrações de NPs de TiO2 causaram redução na contagem das colônias. O compósito contendo 10% de NPs de TiO2 apresentou uma diminuição significativa na contagem de colônias de S. mutans e S. sanguinis durante os três dias. A média mais alta da SBS foi observada no grupo controle, enquanto o valor mais baixo foi observado para o compósito com 10% de NPs. Conclusões: a incorporação de nanopartículas de TiO2 nas resinas compostas lhes conferiu propriedades antibacterianas, e o valor médio da SBS das resinas contendo 1% e 5% de NPs apresentou-se dentro de uma faixa aceitável.

Culture-dependent approaches to explore the prevalence of root canal pathogens from endodontic infections

Abstract: Endodontic infections are considered to be caused by the presence of various microorganisms within the root canal system. Recognition of this microbiota contributes to the successful treatment of infected root canals. This study investigated the microorganisms associated with primary and secondary endodontic infections via culture methods, biochemical tests, and molecular approaches in an Iranian population. Microbial specimens were collected from 36 patients with primary endodontic infection and 14 patients with a history of root canal therapy. Advanced microbiological culture techniques were used to isolate microbiota; subsequently, biochemical tests and 16S ribosomal RNA gene sequencing were performed to identify the microorganisms. Within the total 218 cultivable isolates, Veillonella parvula (20.6%) was found to occur with the highest frequency in primary endodontic infection, followed by Porphyromonas gingivalis (14.1%), and Aggregatibacter actinomycetemcomitans (9.2%). Enterococcus faecalis (36.6%) was the most predominant microorganism in secondary endodontic infections, followed by Candida albicans, Propionibacterium acnes, and V. parvula with frequencies of 20%, 2%, and 2%, respectively. It was concluded that V. parvula and E. faecalis was most frequently found in primary and secondary endodontic infections, respectively.

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. .