Investigation of the hydration process and biological activity of a novel nanosilver incorporated dicalcium silicate based retrograde filling material.

Background: Although several materials have been used for retrograde filling following apical surgeries, there is no consensus on a single best material. Tricalcium silicate-based types of cement have been developed as root-end filling materials mainly due to tricalcium silicate's hydraulic properties. However, its unfavorable setting characteristics and minimal antimicrobial properties have necessitated the introduction of new additives into the existing commercially available materials. To design an affordable product based on a dicalcium silicate with a shorter set time, minimal cytotoxic complications, and enhanced antibacterial activity, we developed a new endodontic cement from pure raw materials, intending to satisfy the prerequisites of ideal retrograde material. Methods: The composition of the experimental calcium silicate-based cement included the addition of calcium chloride and silver nanoparticles in varying concentrations. Structural characterization was carried out using energy dispersive analysis by X-rays using scanning electron microscope (EDAX SEM) and hydration characteristics were performed using an X-ray diffractometer (XRD). The experimental material was further evaluated for biocompatibility using MTT ([3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide)assay and antibacterial activity was evaluated using an agar diffusion test against Enterococcus faecalis. Results: The structural characterization and hydration characteristics revealed that the experimental cement was dicalcium silicate based with favorable biocompatibility and enhanced antibacterial activity. Tricalcium silicate based mineral trioxide aggregate (MTA) also had favourable biocompatibility, however, its antibacterial activity was significantly decreased when compared to the novel cement. Conclusion: All hydraulic cements that are available in the dental market are predominantly tricalcium silicate-based materials. There has been no evidence in the literature to date wherein it has been explored whether a dicalcium silicate-based hydraulic cement can solely be used in root-end cavities. The findings of the study revealed a dicalcium silicate based retrograde filling material with favourable biocompatibility exhibited immediately as well as in the set samples. Incorporation of silver nanoparticles boosted the antibacterial activity when compared to that of ProRoot MTA. This material could potentially reinstate the usual hype created with tricalcium silicate types of cement since dicalcium silicate cements also exhibit similar properties.

Oncogenic viruses as etiological risk factors for head and neck cancers: An overview on prevalence, mechanism of infection and clinical relevance.

OBJECTIVE: This review article aims to discuss the role of oncogenic viruses in the development of head and neck cancers including the prevalence, mode of infection and the clinical relevance of these viral infections associated with tumours. DESIGN: A detailed review of scientific literature was performed relevant to oncogenic viruses associated with head and neck cancers. RESULTS: The incidence of head and neck cancers associated with traditional risk factors such as smoking, chewing tobacco and alcohol consumption have reduced gradually. With the emergence of oncogenic viruses, the viral infection has become a major etiological contributor to the global cancer burden. Viral infection in the etiology of cancer opens up an opportunity for viral gene specific targets in diagnosis and biomarkers to evaluate prognosis. Infection with high-risk HPVs in the oropharynx is already proving to be beneficial as a subset of HPV-positive oropharyngeal cancer patients tend to have better prognosis in terms of treatment responses and overall survival. CONCLUSIONS: Large multi-center clinical trials exploring the implications of modifying viral infections in cancers are further warranted and the results hold the key to the management of patients suffering from cancers driven by viral infections.