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Journal of Functional Biomaterials Mar 2024Selective laser melting (SLM) technologies are becoming increasingly popular. The aim of the work is to compare the metallographic structure, hardness, and selected...
Selective laser melting (SLM) technologies are becoming increasingly popular. The aim of the work is to compare the metallographic structure, hardness, and selected strength properties of alloys obtained by casting and by SLM, with a particular emphasis on fatigue strength. Twenty Cr/Co alloy bars were made by casting or SLM, and samples of appropriate dimensions were prepared for individual tests. The microstructures of the samples were tested by metallography, and then tested for hardness, impact strength, tensile strength, bending strength, and fatigue strength; they were also subjected to fracture after bending, tensile, fatigue, and impact tests, with the resulting fractures examined by scanning electron microscopy (SEM). Primary dendrites and small amounts of gas bubbles were present in the cast samples ground lengthwise. The SEM samples were more finer grained and uniform. Compared to the casting samples, the SLM samples demonstrated higher hardness, lower mean impact strength and higher tensile strength. The casting samples also displayed lower mean elongation values. The casting samples demonstrated slightly higher fatigue strength. The fractures of the casting samples showed an interdendritic character with clearly visible dendrites at the fracture, while those of the SLM samples were also intergranular, but finer grained. SLM generally results in better strength properties, while casting obtains slightly greater fatigue strength.
PubMed: 38535254
DOI: 10.3390/jfb15030061 -
Biomimetics (Basel, Switzerland) Mar 2024Clinical indications for the newly released Ti-Zr (Roxolid) alloy mini-implants (MDIs) aimed for overdenture (OD) retention in subjects with narrow alveolar ridges are...
Clinical indications for the newly released Ti-Zr (Roxolid) alloy mini-implants (MDIs) aimed for overdenture (OD) retention in subjects with narrow alveolar ridges are not fully defined. The aim of this study was to analyze peri-implant and posterior edentulous area microstrains utilizing models of the mandible mimicking a "real" mouth situation with two (splinted with a bar or as single units) or four unsplinted Ti-Zr MDIs. The models were virtually designed from a cone beam computed tomography (CBCT) scan of a convenient patient and printed. The artificial mucosa was two millimeters thick. After MDI insertion, the strain gauges were bonded on the oral and vestibular peri-implant sites, and on distal edentulous areas under a denture. After attaching the ODs to MDIs, the ODs were loaded using a metal plate positioned on the first artificial molars (posterior loadings) bilaterally and unilaterally with 50, 100, and 150 N forces, respectively. During anterior loadings, the plate was positioned on the denture's incisors and loaded with 50 and 100 N forces. Each loading was repeated 15 times. The means with standard deviations, and the significance of the differences (two- and three-factor MANOVA) were calculated. Variations in the MDI number, location, and splinting status elicited different microstrains. Higher loading forces elicited higher microstrains. Unilateral loadings elicited higher microstrains than bilateral and anterior loadings, especially on the loading side. Peri-implant microstrains were lower in the four-MDI single-unit model than in both two-MDI models (unsplinted and splinted). Posterior implants showed higher peri-implant microstrains than anterior in the four-MDI model. The splinting of the two-MDI did not have a significant effect on peri-implant microstrains but elicited lower microstrains in the posterior edentulous area. The strains did not exceed the bone reparatory mechanisms, although precaution and additional study should be addressed when two Ti-Zr MDIs support mandibular ODs.
PubMed: 38534864
DOI: 10.3390/biomimetics9030178 -
Biosensors Mar 2024Accurate sample heating is vital for nucleic acid extraction and amplification, requiring a sophisticated thermal cycling process in nucleic acid detection. Traditional...
Accurate sample heating is vital for nucleic acid extraction and amplification, requiring a sophisticated thermal cycling process in nucleic acid detection. Traditional molecular detection systems with heating capability are bulky, expensive, and primarily designed for lab settings. Consequently, their use is limited where lab systems are unavailable. This study introduces a technique for performing the heating process required in molecular diagnostics applicable for point-of-care testing (POCT), by presenting a method for crafting customized heaters using freely patterned nichrome (NiCr) wire. This technique, fabricating heaters by arranging protrusions on a carbon black-polydimethylsiloxane (PDMS) cast and patterning NiCr wire, utilizes cost-effective materials and is not constrained by shape, thereby enabling customized fabrication in both two-dimensional (2D) and three-dimensional (3D). To illustrate its versatility and practicality, a 2D heater with three temperature zones was developed for a portable device capable of automatic thermocycling for polymerase chain reaction (PCR) to detect () O157:H7 pathogen DNA. Furthermore, the detection of the same pathogen was demonstrated using a customized 3D heater surrounding a microtube for loop-mediated isothermal amplification (LAMP). Successful DNA amplification using the proposed heater suggests that the heating technique introduced in this study can be effectively applied to POCT.
Topics: Pathology, Molecular; Nucleic Acid Amplification Techniques; Escherichia coli O157; DNA; Nucleic Acids; Molecular Diagnostic Techniques; Chromium Alloys
PubMed: 38534259
DOI: 10.3390/bios14030152 -
Nigerian Journal of Clinical Practice Mar 2024The evolution of restorative materials in prosthodontics has led to the emergence of indirect composite resins, including ceromers, as alternatives to traditional...
BACKROUND
The evolution of restorative materials in prosthodontics has led to the emergence of indirect composite resins, including ceromers, as alternatives to traditional metal-ceramic restorations. However, research gaps exist regarding the impact of ageing protocols on the bond strength of ceromer composites to different metal substructures, necessitating further investigation in this area.
AIM
This study aimed to determine the effect of five different ageing protocols on the shear bond strength (SBS) of ceromer indirect composites on two different substructures.
METHODS
In this in vitro study, 120 metallic discs (10 × 2 mm) were cast from cobalt-chromium (Co-Cr) alloy (n = 60) and spark erosion treated from grade V titanium (n = 60). Each sample was sandblasted. The M.L. primer (Shofu, Germany) and layers of opaque were applied to the surface following the manufacturer's instructions. A special jig (6 × 2 mm) was placed on each disc. The ceromer was condensed in it and light-cured separately for 90 s. Following polishing, specimens were separated into five ageing groups: distilled water (as a control), thermal cycling, tea, coffee, and gastric acid immersion. All samples were placed in 37°C incubation for 28 days for distilled water, coffee, and tea, and 7 days for gastric acid immersion and thermal cycling for 5000 cycles (5-55°C). A universal test machine was used to measure the SBS. The samples were evaluated for failure modes using stereomicroscopy. Data were analyzed using one-way analysis of variance (ANOVA) (P < 0.05).
RESULTS
According to one-way ANOVA, the mean SBS (MPa) between the two groups was compared in each ageing protocol, and there were no significant differences between the Co-Cr-C and Ti-C groups (P > 0.05). The most frequent mode of failure in all groups was mixed.
CONCLUSIONS
Applying the ageing protocols, the type of substructure material had no significant effect on the SBS of the ceromer indirect composite except for tea immersion.
Topics: Humans; Coffee; Surface Properties; Composite Resins; Ceramics; Chromium Alloys; Water; Tea; Materials Testing; Dental Bonding; Shear Strength; Dental Stress Analysis; Methacrylates
PubMed: 38528358
DOI: 10.4103/njcp.njcp_88_23 -
Journal of Orthodontic Science 2024The need to overcome the failure of orthodontic micro-implants which might reach to 30% has led to the development of different methods, one of which is nanoparticle...
OBJECTIVE
The need to overcome the failure of orthodontic micro-implants which might reach to 30% has led to the development of different methods, one of which is nanoparticle deposition.
AIM OF STUDY
To evaluate the anti-microbial efficiency of TiO and ZnO nanoparticles (NP) when used as a coating for orthodontic micro-implants.
METHODS
Thirty titanium alloy micro-implants were used in the presented study. They were divided into three groups according to the coating method and the coating materials used: the control group without surface coating; the titanium dioxide (TiO)-coated group, in which direct current (DC) spattering was used to coat the micro-implants with a TiO layer; and the TiO and zinc oxide (TiOZnO)-coated group, in which the micro-implants were coated with a TiO layer via direct current (DC) spattering and a zinc oxide (ZnO) layer via laser vacuum. The micro-implant surfaces were characterized using scanning electron microscopy (SEM) and an energy-dispersive spectrometer (EDS). The antibacterial susceptibility was assessed using gram-positive and gram-negative bacteria.
RESULTS
SEM and EDS tests confirmed the coating of the micro-implants in the TiO- and TiO2ZnO-coated groups. The micro-implants in the TiO- and TiOZnO-coated groups demonstrated higher antibacterial ability than the control group.
CONCLUSION
This study demonstrated the significance of improving the surface of orthodontic micro-implants by coating them with TiO and ZnO nanoparticles to improve osseointegration and prevent biofilm formation.
PubMed: 38516118
DOI: 10.4103/jos.jos_115_23 -
Progress in Orthodontics Mar 2024To analyze and compare the effects of a traditional laboratory-fabricated Hyrax expander (T-Hyrax) and two different 3D-printed Hyrax expander models relative to tension...
OBJECTIVE
To analyze and compare the effects of a traditional laboratory-fabricated Hyrax expander (T-Hyrax) and two different 3D-printed Hyrax expander models relative to tension points, force distribution, and areas of concentration in the craniofacial complex during maxillary expansion using finite element analysis.
MATERIALS AND METHODS
Three maxillary expanders with similar designs, but various alloys were modeled: a T-Hyrax, a fully printed Hyrax (F-Hyrax), and a hybrid printed Hyrax (H-Hyrax). The stress distributions and magnitude of displacements were assessed with a 5 mm expansion in a symmetrical finite element model. The areas of interest included the teeth, alveolar processes, midpalatal suture, nasal complex, circummaxillary sutures (CS), and the expanders themselves.
RESULTS
The highest stress value (29.2 MPa) was found at the midpalatal suture of the F-Hyrax, while the lowest stress (0.90 MPa) was found at the temporozygomatic suture in the T-Hyrax. On average, the F-Hyrax increased stress at the CS by 24.76% compared with the T-Hyrax and H-Hyrax. The largest displacements were found at the upper incisor (U1) and anterior nasal spine (ANS). The findings indicated an average increase of 12.80% displacement at the CS using the F-Hyrax compared to the T-Hyrax.
CONCLUSION
The F-Hyrax exerts more stress and displacement on the maxilla than both the T-Hyrax and H-Hyrax, where the weak link appears to be the solder joint.
Topics: Humans; Animals; Maxilla; Hyraxes; Finite Element Analysis; Incisor; Printing, Three-Dimensional
PubMed: 38494544
DOI: 10.1186/s40510-024-00510-w -
Iranian Biomedical Journal Jan 2024The surface properties of dental and orthopedic implants are directly related to their osseointegration rate. Coating and/or modifying the implant surface might reduce...
BACKGROUND
The surface properties of dental and orthopedic implants are directly related to their osseointegration rate. Coating and/or modifying the implant surface might reduce the time of healing. In this study, we aimed to examine the effects of a hybrid surface consisting of a brushite surface coating and cross-linked water-soluble eggshell membrane protein on the osseointegration of titanium (Ti) screws under in vivo conditions.
METHODS
Twenty Ti alloy screws were implanted monocortically in anteromedial regions of New Zealand rabbit tibiae. Ten screws were untreated and used as controls. The remaining 10 screws were coated with calcium phosphate and following cross-linked with ostrich eggshell membrane protein. All rabbits were sacrificed six weeks after the surgery. Peri-screw tissues were evaluated by micro-computed tomography (µ-CT), histological and histomorphometrical methods.
RESULTS
The μ-CT assessments indicated that the experimental group had significantly higher mean bone surface area (BSA) and trabeculae number (TbN) than those of the control group (p ˂ 0.05). Bone surface area (BV), trabecular separation (TbSp), trabecular thickness (TbTh), and bone mineral density (BMD) scores of the control and experimental groups were quite similar (p > 0.05). The vascularization score of the experimental group was significantly higher than the control group (4.29 vs. 0.92%). No sign of the graft-versus-host reaction was observed.
CONCLUSION
Our findings reveal that coating Ti alloy implants with calcium phosphate cross-linked with ostrich eggshell membrane protein increases the osseointegration of Ti alloy screws by increasing the bone surface area, number of trabeculae and vascularization in the implant site.
Topics: Rabbits; Animals; Osseointegration; Titanium; Water; Alloys; X-Ray Microtomography; Egg Shell; Coated Materials, Biocompatible; Calcium Phosphates; Membrane Proteins; Surface Properties
PubMed: 38477251
DOI: 10.61186/ibj.3939 -
Hua Xi Kou Qiang Yi Xue Za Zhi = Huaxi... Feb 2024This study aimed to compare the differences among four kinds of mechanical Ni-Ti files including T-Flex, Reciproc Blue (RB), ProTaper Gold (PTG), and ProTaper Universal...
OBJECTIVES
This study aimed to compare the differences among four kinds of mechanical Ni-Ti files including T-Flex, Reciproc Blue (RB), ProTaper Gold (PTG), and ProTaper Universal (PTU) in dentinal microcrack generation after root canal preparation by using micro-computed tomography (micro-CT) analysis.
METHODS
A total of 32 freshly extracted double-root-canal premolars with an angle not exceeding 10° were selected and established as root canal preparation models . Then, the specimens were randomly assigned to four experimental groups (=8) according to the different Ni-Ti systems used for root canal preparation: group T-Flex, group RB, group PTG, and group PTU. The voxel size of the micro-CT was set at 17.18 μm. Pre- and post-operative cross-sectional images of roots (=56 940) were scanned and analyzed to identify the presence of dentinal microcracks. The results of each group were expressed by the quantity and percentage of sectional images with microcracks. McNemar test was used to determine whether a significant difference existed in the existence of dentinal microcracks before and after instrumentation. The level of significance was set at <0.05.
RESULTS
Overall, 11.04% of the images presented dentinal defects (=6 288). Dentinal microcracks were observed in 9.82%, 10.79%, 12.27%, and 11.25% of the post-instrumentation images from groups T-Flex, RB, PTG, and PTU, respectively. However, all these dentinal microcracks were already present in the corresponding pre-operative images. No new microcrack of premolars were generated after the root canal preparation utilizing the aforementioned systems.
CONCLUSIONS
Denti-nal microcracks already existed in advance in extracted teeth before root canal preparation. Root canal preparation using the T-Flex, RB, PTG, and PTU systems did not induce the formation of new dentinal microcracks on the straight root canals of premolars.
Topics: Root Canal Preparation; Nickel; Titanium; X-Ray Microtomography; Dentin; Dental Pulp Cavity; Alloys
PubMed: 38475954
DOI: 10.7518/hxkq.2023.2023257 -
Polymers Feb 2024Ensuring a secure bond between a framework structure and layering composite resin veneer is essential for a long-lasting dental restoration. A variety of primer systems...
Ensuring a secure bond between a framework structure and layering composite resin veneer is essential for a long-lasting dental restoration. A variety of primer systems are available to facilitate the adhesive bonding. Nevertheless, the growing preference for efficiency and simplicity in dentistry has made the one-bottle universal primers a desirable option. This study aims to compare the effectiveness of universal primers on the shear bond strength (SBS) of base metal alloy (BMA) and zirconia to layering composite resin. Each 160 BMA and zirconia 20 × 10 × 5 mm test specimen was fabricated. Eight different primers (SunCera Metal Primer, Metal Primer Z, Reliance Metal Primer, Alloy Primer, MKZ Primer, Monobond Plus, ArtPrime Plus, and Clearfil Ceramic Primer Plus) were applied to 20 specimens in each group. Subsequently, a 5 × 2 mm composite resin build-up was applied. SBS tests were performed after 24 h of water storage and after thermocycling (25,000 cycles, 5-55 °C). On BMA, after water storage for 24 h, the bond strength values ranged from 26.53 ± 3.28 MPa (Metal Primer Z) to 29.72 ± 2.00 MPa (MKZ Primer), while after thermocycling, bond strength values ranged from 25.19 ± 1.73 MPa (MKZ Primer) to 27.69 ± 2.37 MPa (Clearfil Ceramic Primer Plus). On a zirconia base, after 24 h, the bond strengths values ranged from 22.63 ± 2.28 MPa (Reliance Primer) to 29.96 ± 2.37 MPa (MKZ Primer) and from 23.77 ± 3.86 MPa (Metal Primer Z) to 28.88 ± 3.09 MPa (Monobond Plus) after thermocycling. While no significant difference in bond strength was found between the primers on the BMA base, five primer combinations differed significantly from each other on zirconia ( = 0.002-0.043). All primers achieved a bond strength greater than 23 MPa on both framework materials after thermocycling. Thus, all primers tested can be applied to both framework materials with comparable results.
PubMed: 38475255
DOI: 10.3390/polym16050572 -
Journal of Conservative Dentistry and... Feb 2024Nickel-titanium (NiTi) instruments have become the backbone of endodontics due to their exceptional properties, superelasticity, and shape memory. However, challenges... (Review)
Review
Nickel-titanium (NiTi) instruments have become the backbone of endodontics due to their exceptional properties, superelasticity, and shape memory. However, challenges such as unexpected breakage, poor cutting efficiency, and corrosion have prompted researchers to explore innovative surface modifications to enhance their performance. This comprehensive review discusses the latest advancements in NiTi metallurgy and their impact on rotary NiTi file systems. Various surface treatment techniques, including ion implantation, cryogenic treatment (CT), thermal nitridation, electropolishing, and physical or chemical vapor deposition, have been investigated to minimize defects, boost surface hardness, and improve cyclic fatigue resistance. Ion implantation has shown promise by increasing wear resistance and cutting efficiency through nitrogen ion incorporation. Thermal nitridation has successfully formed titanium nitride (TiN) coatings, resulting in improved corrosion resistance and cutting efficiency. CT has demonstrated increased cutting efficiency and overall strength by creating a martensite transformation and finer carbide particles. Electropolishing has yielded mixed results, providing smoother surfaces but varying impacts on fatigue resistance. Physical or chemical vapor deposition has proven effective in forming TiN coatings, enhancing hardness and wear resistance. Furthermore, the concept of surface functionalization with silver ions for antibacterial properties has been explored. These advancements present an exciting future for endodontic procedures, offering the potential for enhanced NiTi instruments with improved performance, durability, and patient outcomes.
PubMed: 38463467
DOI: 10.4103/JCDE.JCDE_248_23