Comparing image qualities of dental cone-beam computed tomography with different scanning parameters for detecting root canals.

BACKGROUND/PURPOSE: Cone-beam computed tomography (CBCT) is a useful device in creating 3-dimensional images in the examining area of dentistry and is one of the most common clinical methods in detecting second mesiobuccal (MB2) canals in maxillary molars. The aim of this in vitro study was to compare the image quality of the small field of view (FOV) CBCT with different rotation arcs and scanning speeds in the use of detecting root canals. METHODS: A dentate human skull was scanned in Morita 3D Accuitomo 170 with 4 × 4 cm FOV under 5 mA and 90 kVp. Two different rotation arcs (360° and 180°) and three different scanning modes (slow-speed mode, standard mode and high-speed mode) combined into six different groups. Five different levels of axial sections were selected from each group. Five endodontic specialists rated the image quality by focusing on the sharpness of the MB2 canal of the upper right first molar and the surrounding structures. RESULTS: Despite the rotation arcs, all the observers gave excellent ratings to images taken with slow-speed mode. The high-speed mode taken with 360° and 180° got the second lowest and the lowest ratings, respectively. Under the same scanning speed, the rotation arc did not have a significant difference in image quality. CONCLUSION: Slow-speed mode is inevitable in maintaining adequate image quality during taking CBCT. However, endodontists can use the half rotation mode to significantly reduce radiation dose, exposure time, and still maintain sufficient image quality for root canal anatomy assessment.

Effect of different zinc concentrations on partially-stabilized cement for vital pulp therapy.

BACKGROUND/PURPOSE: We have developed and investigated the partially-stabilized cements (PSC) with Zn for vital pulp therapy due to their short setting time and high cell biocompatibility. However, the effect of PSC with different concentrations of Zn on setting time and biocompatibility remained unknown. Therefore, the purpose of this study was to determine the optimal concentration of Zn to be synthesized with PSC for vital pulp therapy. METHODS: PSC with different weight percentages of Zn (5%, 7%, 10%) were synthesized to attain 5%Zn-PSC, 7%Zn-PSC, and 10%Zn-PSC. The initial and final setting times were measured using the Gillmore needles method, and the compressive strength tests were conducted using a universal testing machine. The phases of Zn-PSC powders were observed using an X-ray diffractometer (XRD). Human dental pulp stem cells (hDPSCs) were used to evaluate the biocompatibility and cytotoxicity of the materials via Alamar blue and LDH assays. Mineral trioxide aggregate (MTA) was used to be compared with Zn-PSC samples. RESULTS: The initial and final setting times of PSC with different concentrations of Zn were reduced considerably compared to those of MTA. The results also indicated that the initial and final setting times decreased as the weight % of Zn increased. 5%Zn-PSC had the highest compressive strength among all tested materials. 5%Zn-PSC samples also displayed comparatively higher cell biocompatibility than 7% and 10% Zn-PSC samples. However, there was no significant difference between the 5%Zn-PSC and MTA in cell biocompatibility. In addition, the results of the LDH release assay indicated a low level of cytotoxicity among all the test samples. CONCLUSION: 5%Zn-PSC has a shorter setting time, better mechanical properties, and good biocompatibility and thus it has great potential for vital pulp therapy.

Evaluation of Carbon Dioxide-Based Urethane Acrylate Composites for Sealers of Root Canal Obturation.

A new root canal sealer was developed based on urethane acrylates using polycarbonate polyol (PCPO), a macrodiol prepared in the consumption of carbon dioxide as feedstock. The superior mechanical properties and biostability nature of PCPO-based urethane acrylates were then co-crosslinked with a difunctional monomer of tripropylene glycol diarylate (TPGDA) as sealers for resin matrix. Moreover, nanoscale silicate platelets (NSPs) immobilized with silver nanoparticles (AgNPs) and/or zinc oxide nanoparticles (ZnONPs) were introduced to enhance the antibacterial effect for the sealers. The biocompatibility and the antibacterial effect were investigated by Alamar blue assay and LDH assay. In addition, the antibacterial efficiency was performed by using Enterococcus faecalis (E. faecalis) as microbial response evaluation. These results demonstrate that the PCPO-based urethane acrylates with 50 ppm of both AgNP and ZnONP immobilized on silicate platelets, i.e., Ag/ZnO@NSP, exhibited great potential as an antibacterial composite for the sealer of root canal obturation.