The effect of Ti anodized nano-foveolae structure on preosteoblast growth and osteogenic gene expression.

The TiO2 nanotubes by anodization have been extensively studied for medical implant and orthopedic applications because of enhancing bone development. In the present study, a new nano-foveolae structure verified by SEM and AFM was prepared by simulating the nanotubes exfoliation from anodized Ti. MC3T3-E1 preosteoblasts were used to investigate the effects of new nanoscale surface on cell spreading, proliferation, and osteogenic gene expression. The new nano-foveolae structure supported preosteoblast better spreading, more filopodiaes shown by SEM (4 h), and lower proliferation (72 h) than the smooth Ti. By two weeks, the new nanoscale surface induced higher expression of osteogenic markers alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN), and collagen I (COL I) with real-time RT-PCR compared to the control group. The results of this study suggest that the new nano-foveolae structure provides a favorable surface for functions of bone cells.

Corrosion behavior of pure titanium in the presence of Actinomyces naeslundii.

It is well known that some microorganisms affect the corrosion of dental metal. Oral bacteria such as Actinomyces naeslundii may alter the corrosion behavior and stability of titanium. In this study, the corrosion behavior of titanium was studied in a nutrient-rich medium both in the presence and the absence of A. naeslundii using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). A. naeslundii was able to colonize the surface of titanium and then form a dense biofilm. The SEM images revealed the occurrence of micropitting corrosion on the metal surface after removal of the biofilm. The electrochemical corrosion results from EIS showed a significant decrease in the corrosion resistant (R(p)) value after immersing the metal in A. naeslundii culture for 3 days. Correspondingly, XPS revealed a reduction in the relative levels of titanium and oxygen and an obvious reduction of dominant titanium dioxide (TiO2) in the surface oxides after immersion of the metal in A. naeslundii culture. These results suggest that the metabolites produced by A. naeslundii can weaken the integrity and stability of the protective TiO2 in the surface oxides, which in turn decreases the corrosion resistance of titanium, resulting in increased corrosion of titanium immersed in A. naeslundii solution as a function of time.

RGD peptide immobilized on TiO2 nanotubes for increased bone marrow stromal cells adhesion and osteogenic gene expression.

Recently, TiO(2) nanotube layers are widely used in orthopedics and dental applications because of their good promotion effect on bone cells. Furthermore, peptide sequences such as arginine-glycine-aspartic acid are used to modify Ti implant for binding to cell surface integrins through motif. In this study, a cellular adhesive peptide of arginine-glycine-aspartic acid-cysteine (RGDC) was immobilized onto anodized TiO(2) nanotubes on Ti to examine its in vitro responses on rat bone marrow stromal cells (BMSCs). Materials were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy techniques. High-resolution C1s scans suggested the presence of RGDC on the surface and SEM images confirmed the nanotubes were not destroyed after modification. BMSCs adhesion and osteogenic gene expression were detected in TiO(2) nanotube layers with and without RGDC modification by fluorescence microscopy, confocal laser scanning microscopy, SEM, and realtime polymerase chain reaction (Real-time PCR). Results showed that the TiO(2) nanotube layers immobilized with RGDC increased BMSCs adhesion compared to nonfunctionalized nanotubes after 4 h of cultivation. Furthermore, the osteogenic gene expression of BMSCs was dramatically enhanced on the TiO(2) nanotube layers immobilized with RGDC (10 mM) compared to the TiO(2) nanotube layers immobilized with RGDC (1 mM) and non-functionalized anodized Ti. Our results from in vitro study provided evidence that Ti anodized to possess nanotubes and then further functionalized with RGDC should be further studied for the design of better biomedical implant surfaces.

The application of rapid prototyping in prosthodontics.

Dentists have used rapid prototyping (RP) techniques in the fields of oral maxillofacial surgery simulation and implantology. With new research emerging for molding materials and the forming process of RP techniques, this method is becoming more attractive in dental prosthesis fabrication; however, few researchers have published material on the RP technology of prosthesis pattern fabrication. This article reviews and discusses the application of RP techniques for prosthodontics including: (1) fabrication of wax pattern for the dental prosthesis, (2) dental (facial) prosthesis mold (shell) fabrication, (3) dental metal prosthesis fabrication, and (4) zirconia prosthesis fabrication. Many people could benefit from this new technology through various forms of dental prosthesis production. Traditional prosthodontic practices could also be changed by RP techniques in the near future.

Corrosion behaviour and surface analysis of a Co-Cr and two Ni-Cr dental alloys before and after simulated porcelain firing.

This study evaluated the corrosion behaviour and surface properties of a commercial cobalt-chromium (Co-Cr) alloy and two nickel-chromium (Ni-Cr) alloys [beryllium (Be)-free and Be-containing] before and after a simulated porcelain-firing process. Before porcelain firing, the microstructure, surface composition and hardness, electrochemical corrosion properties, and metal-ion release of as-cast alloy specimens were examined. After firing, similar alloy specimens were examined for the same properties. In both as-cast and fired conditions, the Co-Cr alloy (Wirobond C) showed significantly more resistance to corrosion than the two Ni-Cr alloys. After firing, the corrosion rate of the Be-free Ni-Cr alloy (Stellite N9) increased significantly, which corresponded to a reduction in the levels of Cr, molybdenum (Mo), and Ni in the surface oxides and to a reduction in the thickness of the surface oxide film. The corrosion properties of the Co-Cr alloy and the Be-containing Ni-Cr alloy (ChangPing) were not significantly affected by the firing process. Porcelain firing also changed the microstructure and microhardness values of the alloys, and there were increases in the release of Co and Ni ions, especially for Ni from the Be-free Ni-Cr alloy. Thus, the corrosion rate of the Be-free Ni-Cr alloy increased significantly after porcelain firing, whereas the firing process had little effect on the corrosion susceptibility of the Co-Cr alloy and the Be-containing Ni-Cr alloy.

Evidence for calcifying nanoparticles in gingival crevicular fluid and dental calculus in periodontitis.

BACKGROUND: Calcifying nanoparticles (CNPs), also known as nanobacteria, can produce carbonate apatite on their cell walls and initiate pathologic calcification. The objective of this study was to determine whether CNPs are present in the gingival crevicular fluid (GCF) from subjects with periodontal disease and whether they can induce the pathologic calcification of primary cultured human gingival epithelial cells. METHODS: GCF and dental calculus samples were collected from 10 subjects with gingivitis and 10 subjects with chronic periodontitis. CNPs in GCF and calculus filtrates were detected with nanocapture enzyme-linked immunosorbent assay kits. The CNPs in cultures of dental calculus filtrates were also identified using immunofluorescence staining, transmission electron microscopy (TEM), and chemical analysis. Pathologic changes in the CNP-treated gingival epithelial cells were observed with TEM, alizarin red staining, and disk-scanning confocal microscopy. RESULTS: CNPs were found in GCF samples from two subjects with chronic periodontitis. Based on chemical analysis, the surface-associated material from CNPs isolated and cultured from calculus has a composition similar to dental calculus. The pathologic calcification of CNP-treated gingival epithelial cells was also observed. CONCLUSIONS: Self-replicating calcifying nanoparticles can be cultured and identified from dental calculus. This raises the issue of whether CNPs contribute to the pathogenesis of periodontitis.

Magnetic fields of 10mT and 120mT change cell shape and structure of F-actins of periodontal ligament cells.

Dental magnetic attachments, usually applied locally to oral cavities, produce stray fields (flux leakage) spreading in adjacent tissues. It has been found that human periodontal ligament (PDL) cells change their geometry and the structure of their cytoskeleton F-actins when the cell cultures are exposed to B-field strengths of B = 10mT and 120mT, respectively, which are similar to those generated by dental magnetic attachments. Analytically, after long-time exposures to B-fields for 12h, 36 h and 60 h, respectively, cytoskeleton F-actins are labeled with a fluorescent dye and observed under a laser scanning confocal microscope. The geometrical cell parameters of cell length and cell width and the fluorescence emission of labeled F-actins, respectively, were determined and subjected to an automatic image analysis using a special software. The results on cell shrinkage and filament reorganizations were statistically analyzed by the program ANOVA (P < 0.05). It was found that only long-time (hours) exposure to high fields in the order of 0.1T may produce tissue irritations during long-time medical treatments using open- and closed-field dental magnetic attachments.

[Influence of tribochemical silica coating on shear bond strength of a dental zirconia ceramic to resin cements].

PURPOSE: To evaluate the effect of tribochemical silica coating for zirconia bonding. METHODS: Sixty cut and fully sintered Lava frame zirconia blocks were randomly divided into 6 groups and subjected to 3 different surface treatments and 2 kinds of resin cement.The surface treatments were airborne-particle abrasion/silane, airborne-particle abrasion/CoJet Sand (tribochemical silica coating) /silane and no treatment(control), resin cements were RelyX Unicem and Panavia F2.0. Half of the specimens in each group were randomly chosen and stored in 37℃ distilled water for 24h, the others were thermocycled (5℃ and 55℃) for 5000 cycles. All specimens were subjected to shear bond strength(SBS) testing. SBS values were analyzed by two-way ANOVA and t test, and multiple pairwise comparisons were then completed with post hoc Tukey test. Statistical analysis was performed using SPSS23.0 software package for Windows. RESULTS: Airborne-particle abrasion/CoJet sand/silane group resulted in a significantly higher SBS than those in other groups (P<0.001). After thermocycling, the bond strengths in the airborne-particle abrasion/CoJet Sand/silane groups bonded with RelyX Unicem showed no significantly decrease while marked drop appeared in all other groups. CONCLUSIONS: Combination of tribochemical silica coating with silane coupling can effectively enforce the bond strengths of zirconia (Y-TZP). Attention should be paid to the interaction between surface treatments and resin cements.

[Changes of oral bacteria flora after wearing complete denture].

PURPOSE: This study investigateed the influence of complete denture on oral bacteria flora. METHODS: Bateria plaque samples in oral mucosa, saliva and denture surfaces in 11 edentulous patients were collected, then the 16S rRNA gene clone libraries were constructed. Pyrosequencing was used to analyze the 16S rRNA gene V3~V4 regions, oral bacteria flora were classified and identified. RESULTS: There were 64800 sequences in complete denture-wearing subjects, Streptococcus mitis, Gemella haemolysans, Rothia mucilaginosa, Porphyromonas sp, Neisseria zoodegmatis, Granulicatella elegans, Acinetobacter baumannii, Pseudomonas citrinum, Granulicatella adiacens and Fusobacterium canifelinum were the predominant species (37416 sequences). The species of denture tissue surface were similar to these of buccal vestibule after wearing denture, and the species of denture smooth surface were similar to these of tongue ventrum and the floor of mouth. CONCLUSIONS: The effect of complete denture on oral flora is still limited, and the composition of oral flora is influenced by many other factors.

[The research for magnetic attachments producing static magnetic fields to influence on cytoskeletons of human periodontal ligament cells].

OBJECTIVE: The present research aimed to investigate that the static magnetic field (SMF) generated by dental magnetic attachments influenced on the cytoskeletons of human periodontal ligament cells (HPDLCs). METHODS: In vitro cultured HPDLCs were exposed to 10 mT and 120 mT SMF which simulated those of from the closed-field and open-field magnetic attachments respectively for 12-60 hours in a cellular SMF exposure system. The control group cells were cultured outside the SMF exposure system and were only exposed to geomagnetic field of about 0.03-0.07 mT. After finishing the SMF exposure, the cytoskeletons were observed under a laser scanning confocal microscope (LSCM). The image analysis software was utilized to measure and analyze the cell area, length/width ratios and the contents of F-actin of cells. RESULTS: There were certain changes observed in the cytoskeletons after HPDLCs exposed to 10 mT and 120 mT SMF for 12-60 hours. With the SMF strength increasing and the loading time extending, the cell microfilaments got ashorened change and a disordered arrangement inside cells, and the length/width ratios of cells decreased (P < 0.05). The areas of cells decreased after SMF loading for 60 hours (P < 0.05). The cell F-actin contents decreased after SMF loading for 12 hours (P < 0.05), but in the meantime there was no significant difference happening between the 36 or 60 hours SMF loading group and the control group (P > 0.05). CONCLUSION: In this study the SMF of magnetic attachments can lead the certain changes to the cytoskeletons in HPDLCs.

[Sintering behavior of tooth-like yttria-stabilized tetragonal zirconia polycrystal by adding rare-earth oxide].

PURPOSE: To investigate the influence on the sintering densification, microstructure and transformation behavior of tooth-like yttria-stabilized tetragonal zirconia polycrystal by adding rare-earth oxide as colorants. METHODS: Six kinds(S1,S2,S3,S4,S5,S6) of tooth-like yttria stabilized tetragonal zirconia polycrystal(Y-TZP)were made by introducing internal colorating technology, the relative density of sintered specimens was determined by the Archimedes method. Scanning electron microscope (SEM) was used to examine the surface morphology and determine the grain size. The phase identification of sintered samples was carried out by X-ray diffractometer. RESULTS: The relative density of the six kinds of tooth-like yttria stabilized tetragonal zirconia polycrystal were over 98%, through SEM images of the cross-sectional surfaces, the grain size of the six kinds of sintered composites were observed in a wide range from 100 nm to 300 nm, a second phase was not detected in the grain boundaries. The diffraction peaks of the main phase were observed as tetragonal phase. CONCLUSIONS: Tooth-like yttria-stabilized tetragonal zirconia polycrystal was acquired with better mechanical property by adding rare-earth oxide as colorants, and was available for clinical application.

[Research progress of bonding strength between porcelain veneer and enamel].

Porcelain veneer had gained more and more attention in dental clinical applications due to its advantages such as good esthetic effects and minor invasiveness. The reliable and consistent adhesive bonding were the key to success. The enamel which featured high mineralization and low moisture would be the ideal bonding part for porcelain veneer. This article was aimed to summarize the research progress regarding to those factors that might had effect on the bonding strength between the porcelain veneer and the enamel including the restoration types of resin adhesives and bonding surface preparations.

Dental fiber-post resin base material: a review.

Teeth that have short clinical crown, which are not alone enough to support the definitive restoration can be best treated using the post and core system. The advantages of fiber post over conventional metallic post materials have led to its wide acceptance. In addition to that the combination of aesthetic and mechanical benefits of fiber post has provided it with a rise in the field of dentistry. Also the results obtained from some clinical trials have encouraged the clinicians to use the fiber posts confidently. Fiber posts are manufactured from pre-stretched fibers impregnated within a resin matrix. The fibers could that be of carbon, glass/silica, and quartz, whereas Epoxy and bis-GMA are the most widely used resin bases. But recently studies are also found to be going on for polyimide as possible material for the fiber post resin base as a substitute for the conventional materials.

[An in vitro comparison of the influence of different surface treatment on shear bond strength between zirconia and enamel].

PURPOSE: To compare the shear bond strength of zirconia to enamel using different surface treatments, in order to provide evidence for clinical practice. METHODS: Forty cut and fully sintered Lava frame zirconia blocks (2.7 mm × 2.7 mm × 5 mm) were randomly divided into 4 groups and subjected to 4 different surface treatments: no treatment (control), airborne-particle abrasion; airborne-particle abrasion and silane; airborne-particle abrasion and CoJet sand (silica coating with 30 µm silica-modified alumina particles) and silane. After surface treatment, the zirconia blocks were bonded to acid-etched enamel with self-adhesive resin cement (RelyX Unicem). Half of the specimens in each group were stored in 37 degrees centigrade distilled water for 24 h and the others were thermocycled (5 degrees centigrade and 55 degrees centigrade) for 5000 cycles. All specimens were subjected to shear bond strength (SBS) test. The data was analyzed with SPSS 20.0 software package for two-way ANOVA and t test. Failure mode was observed and analyzed by scanning electron microscope (SEM). RESULTS: Airborne-particle abrasion and CoJet Sand and silane group resulted in a significantly higher SBS than those in other groups (P<0.001), while no significant difference existed between the specimens which were submerged in 37 degrees centigrade water stored and thermocycled (P=0.595) within this group. No adhesive failures were observed by SEM in this group. CONCLUSIONS: The combination of tribo-chemical silica coating with silane coupling can improve the bond of zirconia when self-adhesive resin cement is used and it is recommended as a pre-treatment to increase zirconia retention.

[The evaluation of intercuspal occlusion of healthy people with T-Scan II system].

PURPOSE: To observe the occluding movement from mandibular postural position to intercuspal position in healthy people. METHODS: The occluding movement in 30 healthy people from mandibular postural position to intercuspal position was recorded by T-Scan II system. The distribution of occlusal force, the center of force, the percentage of intercuspal position occlusal force in Max force and the occlusion time was analyzed by T-Scan II system and SAS 9.0 software package. RESULTS: The results showed that there was no significant difference between the occlusal force of the two sides under the intercuspal position mode(P=0.3242). The average percentage of intercuspal position occlusal force in Max force was 96.89%. The confidence interval (CI) was 90.88%-100%. The average occlusion time was (0.2015 ± 0.0861)s. There was no correlation between the occlusion time and the percentage of intercuspal position occlusal force in Max force. CONCLUSIONS: We could introduce the position of the center of force, the percentage of intercuspal position occlusal force in Max force and the occlusion time to estimate the occlusal condition, and to judge the effect of occlusal therapy. ).

Application of a custom-made inlay structure to a sectional maxillary complete denture for a patient with microstomia: a clinical report.

Prosthodontic treatment for edentulous patients with microstomia is a challenge because of the constricted opening of the oral cavity. This clinical report presents the prosthetic management of an edentulous maxilla in a patient with burn-induced microstomia. A sectional maxillary complete denture was fabricated. With the use of a custom-made inlay structure at the overlapping metal base along the palatal midline, the sectional prosthesis was successfully and easily inserted and provided adequate function in the patient's mouth.

In vitro corrosion study of different TiO2 nanotube layers on titanium in solution with serum proteins.

Titanium oxide nanotubes prepared by anodization have received considerable attention in the biomaterials domain. The objective of this study was to demonstrate the electrochemical behavior of different diameter TiO(2) nanotube layers on titanium in phosphate buffered saline (PBS) and Dulbecco's minimum essential medium+10% fetal calf serum (D-FCS) using open circuit potentials (OCP), electrical impedance spectroscopy (EIS), and a potentiodynamic polarization test. The results showed that the nanotubes had higher OCP, higher resistance of the inter barrier layer (R(b)), and lower I(pass) in the two test solutions compared to the smooth Ti, especially the 30 nm diameter nanotubes. The corrosion resistance of the nanotubes in D-FCS was higher than in PBS because of protein adsorption from the D-FCS solution as suggested by scanning electron microscope (SEM) images. In addition, protein aggregates of 30 nm diameter nanotubes caused the model of EIS spectra to transform from two-layer to three-layer. The corrosion behavior of the nanotubes for use as a dental implant material is discussed.

[Effects of TiSi coating on corrosion resistance of dental Co-Cr alloy].

PURPOSE: To investigate the effect of titanium-silicon(TiSi) coating on corrosion resistance of dental CoCr alloy. METHODS: The commonly used CoCr alloy was cast into 10mm×10mm×3mm specimen in size. Then the specimen was coated with TiSi on the surface by sol-gel method. The specimens were immersed in artificial saliva. Weight loss method was used to analyze corrosion rate. Element analysis using Auger Electron Spectroscopy (AES) was performed to compare the content of element before and after coating of TiSi in artificial saliva. SAS8.0 software package was used for statistical analysis. RESULTS: By weight lost method, before and after coating TiSi, the corrosive rate was 0.163 g·m(-2)·h(-1) and 0.138 g·m(-2)·h(-1) respectively. With AES, in Co-Cr alloy not coating TiSi, atomic concentration (g·m(-2)) of Ni, Co, Cr and Si was 7.728582657,0.008801153,0.306195965 and 0.194851978,respectively. After coating Ti-Si,the content of Ni, Co, Cr and Si and 4.745189808,0.004718889, 0.153195362 and 0.778406136, respectively. The release rate of the Ni,Co,cr were decreased after coating. CONCLUSION: TiSi coating can improve corrosion resistance of CoCr alloy.

[Interface compatibility between tooth-like yttria-stabilized tetragonal zirconia polycrystal by adding rare-earth oxide and Vita VM9 veneering porcelain].

PURPOSE: To evaluate the interface compatibility between tooth-like yttria-stabilized tetragonal zirconia polycrystal(Y-TZP) by adding rare-earth oxide and Vita VM9 veneering porcelain. METHODS: Six kinds(S1,S2,S3,S4,S5,S6) of tooth-like yttria stabilized tetragonal zirconia polycrystal were made by introducing internal colorating technology to detect the thermal shock resistance and interface bonding strength with Vita VM9 Bsaedentin. Statistical analysis was performed using SAS6.12 software package. RESULTS: There was no gap between the layers via hot shocking test.The shear bonding strength between Y-TZP and VitaVM9 was higher and the value was (36.03±3.82) to (37.98±4.89) MPa. CONCLUSIONS: By adding rare-earth oxide to yttria-stabilized tetragonal zirconia polycrystal ,better compatibility between the layer (TZP and Vita VM9) can be formed which is of better interface integrate and available for clinical applications.

[A new method of fabricating photoelastic model by rapid prototyping].

PURPOSE: To explore a novel method of fabricating the photoelastic model using rapid prototyping technique. METHODS: A mandible model was made by rapid prototyping with computerized three-dimensional reconstruction, then the photoelastic model with teeth was fabricated by traditional impression duplicating and mould casting. RESULTS: The photoelastic model of mandible with teeth, which was fabricated indirectly by rapid prototyping, was very similar to the prototype in geometry and physical parameters. The model was of high optical sensibility and met the experimental requirements. CONCLUSION: Photoelastic model of mandible with teeth indirectly fabricated by rapid prototyping meets the photoelastic experimental requirements well.