Dental materials journal最新文献

Additive-manufactured (AMed) Co-Cr and Ti alloy clasps were made with five surface treatments. Either one of a conventional freehand finishing or barrel finishing as a medium finishing process or one of a freehand, dry electrolytic, or magnetic polishings was selected as the final polishing process. After each surface treatment, the polishing efficiencies of the AMed clasps were evaluated as to surface roughness, fitness accuracy, and retentive forces. By surface treatments without using magnetic polishing, sufficient surface smoothness was observed for both alloys. Under all five treatment conditions, better fitness accuracies and sufficient retentive forces were obtained in all Co-Cr and Ti alloy clasps for clinically acceptable results. A combination of barrel finishing and dry electro-polishing can be recommended as the automatic finishing technology, replacing the freehand polishing process by dental technicians. The findings of this study will significantly reduce the workload of dental technicians.

This study evaluated the cusp tip deflection of aluminium tooth models with a mesial-occlusal-distal (MOD) cavity filled with three bulk-fill resin-based composites (RBCs), Aura Ultra Universal (Aura), Admira Fusion x-tra Universal (Admira), and Filtek One shade A2 (Filtek One), to assess the level of shrinkage stress they could produce. The models were prepared using a primer, adhesive and a single RBC increment photo-cured for 20 s at a radiance exitance 1.25 W/cm². The RBC axial shrinkage strain (ε) and stress (S) were also measured. Micro-computed tomography in combination with silver nitrate infiltration showed no interfacial debonding. The mean cusp tip deflection for Admira was found to be smaller than those for the other two RBCs. Although ε and S for Aura were higher than those for Filtek One, their mean cusp tip deflections were not significantly different. These results could be explained by the temporal behavior of their elastic modulus.

People with osteoporosis, common among middle-aged and elderly individuals, often need dental implants. Titanium implants, though generally safe, can cause problems due to their stiffness, especially in osteoporotic bone, leading to fractures. This study aims to identify gradient types that offer improved biological adaptation. This was achieved by comparing the mechanical properties of four new two-dimensional functional gradient materials (FGMs) implants to those of conventional and one-dimensional FGM implants in healthy and osteoporotic bone models. The new FGM implants, with reduced stiffness at the bottom and outer parts, kept strain on cancellous bone within safe limits, reducing fracture risk. Notably, the FGM RA L-H implant maintained strain levels within the optimal range (1,500-3,000 µɛ), promoting bone healing and remodeling. By evaluating the stresses and strains, it was concluded that the FGM RA L-H implant is well adapted to significantly reduce stresses and improve bone recovery in healthy and osteoporotic bones.

A block-type of three-dimensional carbonate apatite bone graft (3D-CO₃Ap) is demanded for applying large bone defects. Although we fabricated the 3D-CO₃Ap with high mechanical strength by fusing polymer-bound spherical precursor, the optimized condition has not yet been found. In this study, we indicated the optimized condition for 3D-CO₃Ap by controlling granular packing ratio (i.e., different compression ratios of the mold volume from 100% to 140%). 3D-CO₃Ap was obtained in the condition from 110% to 130%, even though the block was collapsed in 100% and complete conversion to CO₃Ap was not achieved in 140%. The highest compressive strength was achieved with 130% 3D-CO₃Ap because the intergranular connection area was the most enhanced. Furthermore, when reconstructing bone defects, 130% 3D-CO₃Ap prevented soft tissue penetration and showed good osteoconductivity because of their controlled intergranular pore size. The 130% compression was optimal for achieving both high mechanical strength and osteoconductivity.

In clinical applications, computer-aided design/computer-aided manufacturing (CAD-CAM) blocks must exhibit behavior similar to that of deciduous teeth. The purpose of this study was to evaluate the material properties and suitability of CAD-CAM as deciduous teeth. Experimental fiber-reinforced CAD-CAM composites (FRC) and various CAD-CAM (lithium disilicate ceramic: IPS, hybrid ceramic: VEM, five composite resins, and PMMA) and enamels (deciduous and permanent teeth) were subjected to nanoindentation to evaluate material properties, including nanohardness and nano-reduced elastic modulus. Energy dispersive X-ray spectrometry was conducted in combination with SEM to evaluate the elemental and microstructural properties. FRC-fiber (2.94 GPa), VEM-ceramic (3.20 GPa), and IPS (3.63 GPa) showed no statistically significant differences compared to deciduous enamel (3.37 GPa). Various CAD-CAM materials were confirmed to exhibit sufficient nanohardness and nano-reduced elastic modulus and a strong microstructure, indicating their potential for application in the restorative treatment of full crowns of deciduous teeth.

The primary aim of this study was to determine whether there is a difference in degree of conversion (DC) between resin cements polymerized with an adhesive and those without an adhesive. The secondary aim was to compare interfacial gap of zirconia restoration when resin cements are self-cured. The DC of resin cement was measured without adhesive treatment continuously for 15 min and at 24 h. The DC was measured again after light-curing or self-curing adhesive treatment. For interfacial gap evaluation, inlay cavities were prepared on extracted third molars. Zirconia restorations were fabricated and cemented with the resin cement. After thermo-cycling, interfacial gap at the restoration-tooth interface was investigated using swept-source optical coherence tomography (SS-OCT) imaging. The DC of resin cement with adhesive treatment differed depending on the adhesive, cement, and polymerization method (p<0.05). Interfacial gap was different depending on the adhesive and cement (p<0.05).

Mineral trioxide aggregate cement is an excellent pulp-capping material; however, its base Portland cement contains highly toxic elements and is expensive. This study aimed to explore the possibility of using calcium silicate cement without Portland cement. Synthesis was attempted via firing using calcium silicate (CS), as the base material, and calcium oxide (CA). According to the chemical reaction, they were weighed and sintered in an electric furnace at a sintering temperature of 1,300ºC based on the results of thermogravimetric differential thermal analysis. The powder composition after firing was examined by X-ray diffraction analyses. Compressive tests were performed using a universal testing machine. The sintered powders were confirmed as dicalcium silicate (CS2) and tricalcium silicate (CS3); however, some peaks were detected and their compressive strengths were lower than that of CS. These results suggest that CS2 and CS3 were successfully synthesized from a mixture of CA and CS.

Bioactive fillers in dental adhesives are designed to release beneficial ions, such as calcium and phosphate, to help in remineralization process, and preventing secondary caries. Their incorporation also aims to improve the longevity of dental restorations. Herein, CaP nanoparticles were synthesized through a water-in-oil emulsion method using Tween80 as a surfactant and methacrylic acid (MAA). MAA officiated as a co-surfactant and reduced the size of CaP nanoparticle, including improved compatibility with the components of dental adhesive. The incorporation of 2% T80/CaP/MAA nanofillers into dental adhesive demonstrated increased efficiency, as evidenced by a higher degree of conversion (%DC) and greater micro-tensile bond strength (μTBS). More importantly, T80/CaP/MAA nanofillers were able to induce remineralization process in the dental structure, which was confirmed by EDX mapping and IR imaging. Finally, a cytotoxicity assessment of the dental adhesive containing T80/CaP/MAA showed no significant adverse effects on human fibroblast cells.

The purpose of this study was to investigate the wear behavior of pure titanium when opposed to six different crown restorative materials. Abrader specimens were prepared by casting pure titanium and these were paired with substrates including pure titanium, resin composite, lithium disilicate, zirconia, silver-palladium-copper (Ag-Pd-Cu) alloy, and bovine enamel. The wear volume of each abrader and substrate specimen was measured using the two-body wear test, and factors affecting wear behavior, such as microstructures and hardness, were evaluated. Results indicated that titanium-to-titanium abrasion caused significant wear in both the abrader and the substrate. In contrast, no significant wear was observed for the zirconia and Ag-Pd-Cu alloy against titanium. SEM images showed linear wear marks in most specimens other than zirconia and resin composite, microcracks in enamel, and filler fall in resin composite. A strong correlation between the wear volume and Vickers hardness was found for ceramics, resin composites, and enamel. However, due to the small slope of the approximate straight line in this correlation suggests that the wear behavior of materials when abraded by titanium is only partially influenced by the microstructure and hardness of the material.

The purpose of this study is to investigate the effects of surface treatment methods using polyetheretherketone (PEEK) (with or without a functional monomer-containing primer following treatment with alumina blasting or concentrated sulfuric acid) on the shear bond strength (SBS) of resin luting material after artificial aging. The PEEK specimens were classified into five groups according to their treatment methods: untreated, alumina blasting (AB), concentrated sulfuric acid (SA), alumina blasting+primer (ABP), and concentrated SA+primer (SAP). The SBS score of each group was determined experimentally using a universal testing machine. The SBS tests revealed that the initial bond strengths of ABP and SAP were significantly higher than those of AB and SA. In addition, both SBS after 20,000 thermal cycles remained high (>15 MPa). These results suggest that the ABP and SAP groups are the best predictive methods for evaluating SBS with PEEK and resin cement.