Comparative study of the radiopacity of resin cements used in aesthetic dentistry

Evaluation of radiopacity of cements used in implant-supported prosthesis by indirect digital radiography: an in-vitro study

In order to help dentists in choosing the right type of cement for implant-based prostheses, the radiopacity of commonly used cements available in the market was investigated by digital radiography with PSP sensor. In the present study, temporary cements of TempBond (Kerr, Germany), TempBond clear (Kerr, Germany), Dycal (Dentsply, USA) and permanent cements of Multilink N (Ivoclar, Brazil), Panavia F 2.0 (Kurrary, Japan), Fuji plus (GC, Japan), RelyX (3M, USA), Durelon (3M, USA) were used. Four pill-like samples with 0.5 mm and 1 mm thickness and 5 mm in diameter inside the silicon index as recommended by the manufacturer were prepared for each cement. Aluminum step wedge (99% aluminum alloy) was used as control. Using digital radiography, cement and aluminum step wedge samples were radiographed. The images of cement tablets were measured by digital radiography using DFW software to check their radiopacity values. Bonferroni test and Mann-Whitney U test were used for comparison of cements. The highest radiopacity between the group of 1 and 0.5 mm thickness was related to Glass ionomer Fujiplus GC (2407±45.99) and TempBond (137.21±22.46) cement, respectively. Whereas, the lowest radiopacity among the groups was related to Clear cement. The difference between the mean radiopacities among the studied groups was statistically significant (p<0.001). Based on the results, among the available cements, Glass ionomer Fujiplus GC and TempBond cement are the most efficient for 1 and 0.5 mm thickness, respectively, and Clear cement is the least efficient cement in both groups in terms of radiopacity.

Comparative evaluation of net setting time and radiopacity in Fuji II (GC-Japan) restorative glass ionomer and Iranian glass ionomer

Background

Comparing the net setting time and radiopacity of an Iranian glass ionomer cement (GIC) and Fuji II (GC, Japan) according to ISO 9917-1:2007 standard.

Materials and Methods

In this experimental/in vitro study, for both tests, we prepared 20 samples of Fuji II glass ionomer (self-cure restorative glass ionomer, batch number: 1608031, GC Corporation, Tokyo, Japan) and Iranian glass ionomer (Ava Tajhiz Dandan-Iran) at P/L of 2/7:1. Then, to determine the net setting time, we prepared a metal mold with dimensions of 10 mm in length, 8 mm in width, and 5 mm in height. Ninety seconds after mixing, the surface of the sample was subjected to the indenter, and the net setting time was recorded as the time elapsed between the end of the mixing and the time needle stopped making a complete circular indentation. To determine radiopacity, the specimens were poured into a mold with a diameter of 15 mm and thickness of 1 mm. Samples and a step wedge were irradiated with X-rays. Particle size analysis and Energy-dispersive X-ray spectroscopy (EDS) analysis were also done for both cements. Test results were investigated with SPSS and through independent t-test (P < 0.05).

Results

The mean value of net setting time for Fuji II was 4.83 min and for the Iranian Glass ionomer was 3.83 min (P < 0.05). The mean value of radiopacity for Fuji II was 2.3 mmAL and for Iranian Glass ionomer was 1.9 mmAl (P < 0.05).

Conclusion

Net setting time and radiopacity of the glass ionomers were within the range of ISO 9917-1:2007. If all properties of the Iranian cement are set appropriately in future investigations, we propose to use it instead of Fuji II GIC. This has the additional benefit of being cost-efficient as Iranian cement costs less than Fuji II cement.

Hybrid fiber optic-fMRI for multimodal cell-specific recording and manipulation of neural activity in rodents

Significance: Multiscale imaging holds particular relevance to neuroscience, where it helps integrate the cellular and molecular biological scale, which is most accessible to interventions, with holistic organ-level evaluations, most relevant with respect to function. Being inextricably interdisciplinary, multiscale imaging benefits substantially from incremental technology adoption, and a detailed overview of the state-of-the-art is vital to an informed application of imaging methods. Aim: In this article, we lay out the background and methodological aspects of multimodal approaches combining functional magnetic resonance imaging (fMRI) with simultaneous optical measurement or stimulation. Approach: We focus on optical techniques as these allow, in conjunction with genetically encoded proteins (e.g. calcium indicators or optical signal transducers), unprecedented read-out and control specificity for individual cell-types during fMRI experiments, while leveraging non-interfering modalities. Results: A variety of different solutions for optical/fMRI methods has been reported ranging from bulk fluorescence recordings via fiber photometry to high resolution microscopy. In particular, the plethora of optogenetic tools has enabled the transformation of stimulus-evoked fMRI into a cell biological interrogation method. We discuss the capabilities and limitations of these genetically encoded molecular tools in the study of brain phenomena of great methodological and neuropsychiatric interest-such as neurovascular coupling (NVC) and neuronal network mapping. We provide a methodological description of this interdisciplinary field of study, and focus in particular on the limitations of the widely used blood oxygen level dependent (BOLD) signal and how multimodal readouts can shed light on the contributions arising from neurons, astrocytes, or the vasculature. Conclusion: We conclude that information from multiple signaling pathways must be incorporated in future forward models of the BOLD response to prevent erroneous conclusions when using fMRI as a surrogate measure for neural activity. Further, we highlight the potential of direct neuronal stimulation via genetically defined brain networks towards advancing neurophysiological understanding and better estimating effective connectivity.