Dental materials journal最新文献

Dentin cavity wall pretreatments to improve the bond strength of direct and computer-aided design/computer-aided manufacturing (CAD/CAM) restorations using resin composite were examined. Experiment 1 divided 18 standardized MOD cavities into three conditions: no pretreatment (Group N, control); chemical pretreatment with EDTA solution (Group C); and mechanical pretreatment with glycine air-powder polishing (Group M). Specimens were restored using direct resin composites. Micro-tensile bond strength (μ-TBS) was measured after cyclic loading. The μ-TBS was significantly higher for Groups C and M than for Group N. Group M showed the best bonding reliability. In Experiment 2, cavity preparation, dentin pretreatment, cyclic loading, and μ-TBS testing were performed using the same methods applied in Experiment 1. Specimens were restored using CAD/CAM resin composite inlays. The μ-TBS was significantly higher for Groups C and M than for Group N. No significant difference in bonding reliability was apparent among all groups.

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.

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.

A tongue-controlled intraoral pointing device for operating information and communication terminals, such as computers, which allows the wearer to perform oral training while typing, was developed. Its effectiveness was evaluated in healthy participants. There were no differences in typing speed for the same input between computers with any operating system/display combination. Typing with the developed device was performed at 80% of the speed compared to using a stylus pen held in the mouth, the conventional method used by persons with upper limb disabilities. Electromyography signals increased concomitantly by 1.8-fold in the buccal and 2.0-fold in the submandibular area. There was a 2.5-fold increase in saliva secretion and a decrease in salivary α-amylase activity to 40%, indicative of stress. The computerized operation of this device is expected to contribute to the prevention of oral frailty by maintaining and strengthening oral functions and hygiene.

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.

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.

This study investigated the effect of vacuum plasma treatment on the shear bond strength (SBS) of three-dimensional (3D)-printed resin and resin cement. Specimens were categorized based on airborne-particle abrasion (APA), plasma, and bonding agent treatments. Long-term adhesive stability was examined by comparing their SBSs before and after thermocycling. The group with the bonding agent applied after plasma treatment and before thermocycling exhibited the highest SBS of 23.9±2.2 MPa. No significant SBS difference was observed among the remaining groups, except for that subjected only to plasma treatment after thermocycling. The wettability of distilled water improved in the groups treated with plasma, whereas that of the bonding agent decreased in the group treated only with APA. Surface analysis revealed a roughened surface on the plasma-treated 3D-printed resin. Therefore, vacuum-plasma treatment before thermocycling can enhance the SBS of 3D-printed resin without compromising its properties.

This study investigated the thermal stability and top-to-bottom hardness ratio of six bulk-fill composites (STARK^® Bulk Fill Composite, Filtek™ One Bulk Fill Restorative, SDR^® Plus Bulk Fill Flowable, Tetric^® N-Ceram Bulk Fill, X-tra fil, and Beautifil-Bulk Restorative) following acidic softening. Discs-shaped specimens were fabricated and photo-cured for 20 s. Vickers hardness was sequentially measured, immediately after irradiation (VH₀), after 24 h of dry storage (VH_dry) and after 24 h of acidic storage (VH_acidic) at 37°C. Network integrity was assessed by comparing the relative hardness decrease (VH_RD) after acidic softening with the initial maximum rate temperature (IRT) of mass loss. Compared to VH₀, VH_dry significantly increased, whereas VH_acidic significantly decreased. The VH_RD of top surface ranged from 16.62% for FBF to 62.84% for SDR. IRT primarily reflects resin composition and residue is a filler-based value. Relative network integrity estimated by IRT revealed a negative correlation with VH_RD. Consequently, acidic erosion hardness development can be indirectly employed to assess network integrity in bulk-fill composites.

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 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.