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Background: In this study, we investigated the effects of differences in scanning pathways during optical impression on the trueness and precision of full-arch impressions., Methods: Reference data were obtained using a laboratory scanner. All optical impressions were measured across the dental arch using TRIOS® 3 in four different pathways. The reference and optical impression data were superimposed using the best-fit method. The criteria for superimposition were based on the starting side of the dental arch (partial arch best-fit method, PB) and based on the full arch (full arch best-fit method, FB). The data were compared between the left and right molars (starting and ending sides). The scan deviations for trueness (n = 5) and precision (n = 10) were obtained for each group by calculating the root mean square (RMS) of the deviation at each measurement point. Visual observations using superimposed color map images revealed variations in trueness., Results: There were no significant differences in scanning time or amount of scan data between the four scanning pathways. Trueness did not differ significantly among the four pathways with respect to the starting and ending sides, regardless of the superimposition criteria. Precision with PB was significantly different between scanning pathways A and B, and pathways B and C for the starting sides, and between scanning pathways A and B, and pathways A and D for the ending sides. In contrast, there was no significant difference between the starting and ending side in pathways for FB. Regarding PB, color map images showed a large error range in the direction toward the molar radius for the occlusal surface and cervical regions on the ending sides., Conclusion: Differences in the scanning pathways did not affect trueness, regardless of the superimposition criteria. On the other hand, differences in the scanning pathways affected the precision of the starting and ending sides with PB. Scanning pathways B and D were more precise on the starting and ending sides, respectively., (© 2023. The Author(s).)

The purpose of this study was to evaluate whether change in cuspal inclination influences the fracture load values of composite resin computer-aided design/computer-aided manufacturing (CAD/CAM) crowns. Abutment teeth and CAD/CAM crowns were prepared as they would be for treating a mandibular first premolar with two cusps. The CAD/CAM crowns were designed so that 1) the principal stress lines would be radially distributed from the two points of contact with the indenter to the occlusal area of the abutment (Type I), or 2) the principal stress lines would pass outside the occlusal area of the abutment (Types II and III). The CAD/CAM crowns were mounted on the abutments using one of two types of resin or polycarboxylate cement. Fracture load values were measured using a universal tester. The Type I CAD/CAM crowns exhibited the highest mean fracture load value, followed by the Type II crowns and then the Type III crowns, with significant differences seen between all types (p<0.05). The luting agent used (resin or polycarboxylate cement) showed no effect on the fracture load value. With the Type II and Type III crowns, significant differences in the fracture load value were observed between the Super-Bond and Hy-Bond polycarboxylate cement groups (p<0.05).

Layered-type zirconia disks, which offer color gradation from enamel to cervical shade, have been employed in recent years to replicate the shades of natural teeth. The layered structure is effective at replicating colors and has helped popularize monolithic zirconia restorations. However, the sintering shrinkage of zirconia is very large; thus, controlling the sintering distortion is very important. Thus, the objective of this study was to determine the influence exerted by the layered structure of the zirconia disk and the vertical milling area on the sintering distortion. An experimental fixed partial denture (FPD) was designed based on a 4-unit monolithic zirconia FPD. A single-composition (SC)-type disk with no shade and a single-composition-layered (SCL)-type disk with shade gradation were selected for this study. In particular, three milling areas, the top end of the disk (area I), vertical center (area II), and bottom end of the disk (area III), were investigated. Moreover, the sintering distortions generated by the experimental FPDs were measured. Results showed that sintering distortion in 4-unit monolithic zirconia FPDs occurred in all SC and SCL areas. Additionally, the sintering distortions were affected by the layered structure of the zirconia disks, the degree of which depended on the milling area (area I > area II > area III). Thus, when fabricating dental prosthesis using SCL zirconia disks, the milling area must be selected considering both the color adjustment and sintering distortion., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The objective of this study was to determine the influence of height and thickness of the one wall remaining coronal tooth structure on the fracture resistance of an endodontically treated root with resin abutment build-up using resin composite and fiber-reinforced resin composite post. Static and dynamic fracture tests were performed by placing the remaining tooth wall on the tensile side and applying loads at an angle of 30° from the tooth axis. Superior static fracture resistance was observed when the wall remaining on the tooth had a height and thickness greater than 1.0 mm. The dynamic fatigue test showed high loading capacity or fracture resistance in specimens with large height and thickness. The dynamic fatigue test showed the influence of the remaining tooth structure on fracture resistance clearly. In conclusion, the static and dynamic fracture resistances increased with the height and thickness of the one wall remaining tooth structure.

Background/objectives: Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical immunoregulatory molecule expressed on T cells. CTLA-4 also binds to the surfaces of monocytes and macrophages, precursors of osteoclasts. Research on rheumatoid arthritis demonstrated that CTLA-4 suppresses inflammation and bone resorption. However, its effects on alveolar bone have yet to be understood. The purpose of this study was to investigate the role and potential mechanism of CTLA-4 in bone resorption in periodontitis., Materials and Methods: In vivo, the effects of systemic administration of CTLA-4 immunoglobulin fusion protein (CTLA-4-Ig) on alveolar bone resorption were investigated using a periodontitis mouse model. A total of 20 C57BL/6J mice were randomly assigned to two groups according to the administration modes. Periodontitis was induced by placing a ligature around the left maxillary second molar. The contralateral tooth was left un-ligated. In the CTLA-4-Ig (+) group, CTLA-4-Ig was administered by intraperitoneal injection at 1 and 3 days after ligature placement. Animals in the CTLA-4-Ig (-) group were given only phosphate-buffered saline each time. At 5 days after ligature placement, bone resorption was assessed by micro-computed tomography and histological examination, and the prevalence of osteoclast-like cells was assessed by tartrate-resistant acid phosphatase (TRAP) staining. In vitro, the effects of CTLA-4-Ig on osteoclasts were evaluated. Viability of RAW 264.7 cells treated with receptor activator of nuclear factor-κB ligand (RANKL) and CTLA-4-Ig was tested by WST-1 assay. Osteoclast-like cells were enumerated by TRAP staining, and osteoclast activity was evaluated by resorption pit assay. Gene expression levels of osteoclast differentiation markers (macrophage-colony stimulating factor receptor, carbonic anhydrase II, cathepsin K, and Trap) and protein phosphatase 2A (PP2A), a major serine-threonine phosphatase, were assessed by quantitative real-time polymerase chain reaction. The effect of CTLA-4-Ig on the nuclear factor-κB (NF-κB) activation was assessed by enzyme-linked immunosorbent assay., Results: In vivo, ligature-induced bone resorption and the numbers of osteoclast-like cells were significantly decreased by the administration of CTLA-4-Ig. In vitro, treatment with RANKL and CTLA-4-Ig had no significant effect on cell viability. CTLA-4-Ig significantly reduced the prevalence and activation of osteoclast-like cells and decreased the expressions of osteoclast differentiation markers, compared with the RANKL-treated control. CTLA-4-Ig significantly suppressed RANKL-induced phosphorylation of NF-κB p65 but increased PP2A expression., Conclusion: These results suggest that CTLA-4-Ig abrogates bone resorption in induced periodontitis, possibly via inhibition of osteoclast differentiation and activation. The regulation of the NF-κB pathway and PP2A expression may be one mechanism by which CTLA-4-Ig suppresses osteoclast behavior., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Many types of interdental instrument, such as dental floss and interdental brushes, can be purchased easily and sell in large numbers. Many studies have compared the effects of such instruments. Few studies have investigated their relationship with regions of residual plaque, however. The purpose of this study was to compare rates of plaque removal from the mesial and distal surfaces of the bilateral maxillary and mandibular premolars and molars among 3 types of interdental instrument: finger-winding-dental floss, holder-type dental floss, and an interdental brush. Prior to the experiment, the artificial teeth in a jaw model were removed for application of artificial plaque. The teeth were then replaced and the model attached to a phantom. An operator brushed the teeth in a posture close to that adopted in actual tooth brushing with each type of instrument, after which the plaque removal rate was compared among them. The rate of plaque removal using finger-winding floss was the highest, although this type of instrument is less easy to hold than the others. The rate with a handle-equipped interdental instrument showed a decrease in some regions, although it is easy to hold. The results of this study suggest that the type of interdental instrument used should differ depending on the region to be cleaned.

This study investigated the optical properties and flexural strength of translucent TZP layered with high-translucent PSZ using resin cement of various shades. Zirconia specimens (translucent TZP; Zpex and high-translucent PSZ; ZpexSmile) were 13 mm in diameter, layered at thickness ratios of 0.3/0.7, 0.5/0.5, and 0.7/0.3 mm (ZpexSmile/Zpex), and then luted using resin cement of 3 shades. Monolithic specimens of both were used as controls. CIE L*a*b* color coordinates and translucency parameter (TP) were evaluated as optical properties. Biaxial flexural strength was also determined as a mechanical evaluation. The a* and b* values of layered specimens varied depending on the shade of cement. TP values were not affected by shade of cement and thickness ratio. The biaxial flexural strength was intermediate value between both monolithic specimens. The layering method of zirconia with various translucencies using resin cement of different shades can improve color expression while maintaining clinically sufficient flexural strength.

The technology of physicochemical surface modification is available for enhancing the bioactivity and osseointegration capability of tetragonal zirconia polycrystal (TZP). Hydrophobicity index and electrical charge play important roles in protein adsorption. We previously studied the mechanism underlying the adsorption of bovine serum albumin (BSA) on the surfaces of dental materials and hydroxyapatite in vitro. The aim of the present study was to clarify the correlation among the adsorption of BSA to TZP and physicochemically modified TZP surfaces and the zeta potential of BSA and TZP. We used TZP that was sintered at 1350°C for 2 h in air because this kind of TZP is widely applied in the field of dentistry. Surface physicochemistry was modified with ultraviolet light (UV) and atmospheric-pressure plasma treatment. The zeta potentials were measured with ELSZ-1000 and ELSZ-2000 analyzers (Otsuka Electronics, Hirakata, Japan). All experiments were conducted in 10 mM NaCl (pH 7.0). The zeta potentials of as-received TZP and BSA were negative, but those of UV- and plasma-treated TZP were positive. The reason the zeta potentials of TZP changed positive by physicochemical modification is due to an increase in the amount of basic hydroxyl groups. The zeta potentials of UV- and plasma-treated TZP after BSA adsorption were negative. These results suggested that electrostatic interactions play an important role in BSA adsorption to TZP and modified TZP surfaces, so that this modified surface may control the adsorption of protein.

Human mesenchymal stem cells (hMSCs) are multipotent cells, and have been expanded and differentiated into several kinds of mesodermal tissue in vitro. In order to promote bone repair, enhancement of the proliferation and differentiation of hMSCs into osteoblasts in vitro is recommended prior to therapeutic delivery. However, for clinical applications, it is still unclear which method is more advanced for tissue engineering: to transplant undifferentiated cells or partially differentiated stem cells. Therefore, the present study aimed to investigate how osteogenic differentiation medium (ODM) affects hMSCs cultured in a 3D scaffold using a radial-flow bioreactor (RFB) besides cell growth medium (GM). To produce precultured sheets, the hMSCs were first seeded onto type 1 collagen sheets and incubated for 12 h, after which they were placed in the RFB for scaffold fabrication. The culture medium was circulated at 3 mL/min and the cells dynamically cultured for 1 week at 37 °C. Static cultivation in a culture dish was also carried out. Cell proliferations were evaluated by histological analysis and DNA-based cell count. Alkaline phosphatase (ALP) activity, immunocytochemical analysis with BMP-2, and osteopontin on the hMSCs in the collagen scaffold were performed. After 14 days of ODM culture, a significant increase in cell number and a higher density of cell distribution in the scaffold were observed after both static and dynamic cultivation compared to GM culture. A significant increase in ALP activity after 14 days of ODM was recognized in dynamic cultivation compared with that of static cultivation. Cells that BMP-2 expressed were frequently observed after 14 days in dynamic culture compared with other conditions, and the expression of osteopontin was confirmed in dynamic cultivation after both 7 days and 14 days. The results of this study revealed that both the proliferation and bone differentiation of hMSCs in 3D culture by RFB were accelerated by culture in osteogenic differentiation medium, suggesting an advantageous future clinical applications for RFB cell culture and cell transplantation for tissue engineering.