Artifact expression of polylactic acid/hydroxyapatite/graphene oxide nanocomposite in CBCT: a promising dental material.

OBJECTIVE: To evaluate the artifact expression of a new material-polylactic acid (PLA)/hydroxyapatite (HA)/graphene oxide (GO) nanocomposite-and compare it with that of commonly used dental materials, using cone-beam computed tomography. MATERIALS AND METHODS: Cylinders of amalgam alloy, metal alloy, titanium, gutta-percha, and PLA/HA/GO were individually placed in the center of an acrylic phantom. Three images of each phantom + cylinder set were acquired using a Picasso Trio unit (Vatech, Hwaseong, South Korea) set at 90 kVp, 3.7 mA, 0.2 mm3 voxel size, and 12 × 8.5 cm FOV. Three images of a control group (sound phantom) were also obtained. Eight ROIs were established in each image to evaluate the standard deviation (S.D.) of gray values in the ImageJ Software. The Kruskal-Wallis test with the Student-Newman-Keuls post hoc was employed, considering a significance level of 5%. RESULTS: There were no significant differences in S.D. between the control and PLA/HA/GO images (p = 0.712). Both control and PLA/HA/GO showed fewer image artifacts than the other materials (p < 0.05). The images of the amalgam alloy did not differ from the metal alloy images (p = 0.691), showing more artifacts than the gutta-percha (p = 0.028) and titanium (p = 0.051). CONCLUSIONS: The PLA/HA/GO produced fewer artifacts and a better-quality image than the other tested materials. CLINICAL RELEVANCE: The PLA/HA/GO has physical and biological properties similar to those of dental materials. Since it has produced fewer image artifacts, this new nanocomposite may be employed in the near future, enhancing the diagnosis in CBCT.

Effect of lubricant on mechanical and rheological properties of compatibilized PP/sawdust composites.

An investigation was performed regarding the effect of compatibilizer and lubricant concentrations on the mechanical and rheological properties of polypropylene/sawdust composites using two-level factorial central composite design. Maleic anhydride grafted PP (PP-g-MA) was used as compatibilizer and the lubricant used was Struktol TPW 113. Composites without these additives were also prepared. Processing was carried out in a co-rotating twin-screw extruder coupled to a Haake rheometer. Mechanical properties were assessed from tensile tests and rheological properties were evaluated by oscillatory measurements and melt flow index (MFI) test. Tensile strength improved with increasing compatibilizer concentration in the composites and reached a maximum value in the absence of lubricant. When both additives were present tensile strength decreased, suggesting a possible interaction between lubricant and compatibilizer, reducing efficiency of the latter. The general trend observed for rheological results was a decrease in complex viscosity, storage modulus and MFI when both additives were present.