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In this study, retentive forces were compared between telescopic crowns (TSC) made with poly(ether ether ketone) (PEEK) using computer-aided design and manufacturing and type 4 gold alloy using the conventional method. The retentive forces of TSCs were evaluated by performing a pull-out test with primary and secondary crowns. Initial retentive force was approximately 12 N for both PEEK and gold alloy TSCs. The retentive force of PEEK TSC was approximately 6.5 N after 10,000 cycles of insertion and removal. The reduction rate in retentive force was smaller for gold alloy TSC. PEEK TSC displayed greater surface roughness on the primary crown compared to the gold alloy TSC. Surface roughness slightly increased at the cervical margin after repetitive insertion and removal. The retentive force of PEEK TSC was smaller than gold alloy TSC, however the retentive force of PEEK TSC was adequate for stabilizing dental prostheses even after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Zirconia have been applied to dental implants as well as fixed dental prostheses due to their mechanical, esthetic and biocompatible performance. Moreover, they offer an advantage over titanium (Ti) implants, in that there is no risk of discoloration or hypersensitive reaction with allergy. In this review, the durability and tissue-compatibility of zirconia for the oral implants was mainly discussed. Hot isostatic pressing of Y-TZP had higher cyclic fatigue strength than Cp-Ti (Grade-2), leading the sufficient durability. Tissuecompatibility of zirconia; 1) Blast and acid-etching was effective for bone formation with synergetic effect of micro- and nanotopography. 2) Super-hydrophilic treatment, cold plasma in particular, enhanced initial attachment of osteoblast-like cells and oral keratinocytes. 3) Adherence of the periodontopathic bacteria on zirconia was similar to that on Cp-Ti, leading the necessity of surface modification. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the suitability of monolithic zirconia crowns (MZC) as abutment teeth of Akers clasps on removable partial dentures (RPD) by determining the change in retentive force after repetitive insertion/removal test. MZC and silver palladium copper alloy (Ag–Pd) full-metal crowns (FMC) for the mandibular second premolar were fabricated. Resin patterns of Akers clasps made with a 3D printer were casted with Ag–Pd or cobalt chromium alloy (Co–Cr). Clasp retentive force was measured with combinations of the crown and clasp materials. After measuring the initial retentive force of the clasp, repetitive insertion/removal test was carried out. The surface of the crown before and after the test was observed with an optical microscope and a scanning electron microscope; some specimens were subjected to element analysis by an electron probe microanalyzer. The initial retentive force of the Co–Cr clasp was greater than the Ag–Pd clasp for both MZC and FMC. Clasp retentive force decreased with increasing number of insertion/removal cycles, and least reduction in force was observed for the Ag–Pd clasp on MZC. Wear marks were detected where FMC contacted the clasp. Discoloration of MZC due to wear of the Co–Cr clasp was observed. When repetitive insertion/removal of the clasp was performed on MZC, retentive force decreased depending on clasp materials. However, the amount of decrease in retentive force was comparable or small compared to conventional FMC. As a result, it was suggested that MZC could be used on abutment tooth for RPD. [ABSTRACT FROM AUTHOR]

Abstract Purpose The aim of the present study was to compare the accuracy and retentive force of an experimental denture base fabricated using additive manufacturing and heat curing. Methods A maxillary edentulous jaw model made of silicon was used. The shape data for the working cast and wax pattern of the experimental denture base were obtained using a dental laboratory scanner. Fabrication of the experimental denture bases was performed using heat curing and additive manufacturing. The shape data for the experimental denture bases was captured using an optical scanner. The shapes of the two experimental denture bases were compared with the shape of the working cast. A digital force gauge was used to measure the traction force. Pulling was maintained until the experimental denture base separated from the elastic model. Retention was set as the maximum value for the traction force. In order to compare the retentive force of the two experimental denture bases. Results The experimental denture base fabricated using additive manufacturing was more accurate than the experimental denture base fabricated using heat curing. The experimental denture base fabricated using additive manufacturing demonstrated greater retentive force than the experimental denture base fabricated using heat curing. Conclusions In this study, the experimental denture base fabricated using additive manufacturing was more accurate and obtained greater retentive force than the experimental denture base fabricated using heat curing. [ABSTRACT FROM AUTHOR]

Purpose The aim of this in vitro study was to evaluate tensile bond strengths and corrosion resistance of CoCr alloys joined with gold cylinder by a soldering system in comparison with the conventional cast-joining system. Methods CoCr alloys joined with gold cylinder by a soldering system using a high-fusing gold solder (CoCr/Solder/Gold cylinder), gold alloy joined with gold cylinder by a cast joining system (Gold alloy/Gold cylinder) and CoCr castings were fabricated. The tensile bond strength and corrosion resistance in 0.9% NaCl solution (pH 7.4 and pH 2.3) were evaluated. Scanning electron microscopy (SEM) of the fractured surface and electron probe microanalysis (EPMA) of the joined interfaces were also performed. Results The tensile bond strengths of the CoCr/Solder/Gold cylinder specimens showed similar values as the Gold alloy/Gold cylinder specimens. SEM observation and EPMA analyses suggested firm bonding between the CoCr alloy and gold cylinder. The released elements from the CoCr/Solder/Gold cylinder specimens were similar to ones from CoCr castings. Conclusions Results showed that superstructures made of CoCr alloys joined with the gold cylinder using a high-fusing gold solder had sufficient bond strength and high corrosion resistance. These hybrid frameworks with cobalt–chromium alloy and gold cylinder are promising prosthesis for implant superstructures with the low cost and favorable mechanical properties instead of conventional high-gold alloys. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop and evaluate a dental implant surgery simulator that allows learners to experience the drilling forces necessary to perform an osteotomy in the posterior mandibular bone. The simulator contains a force-sensing device that receives input and counteracts this force, which is felt as resistance by the user. The device consists of an actuator, a load cell, and a control unit. A mandibular bone model was fabricated in which the predicted forces necessary to drill the cortical and trabecular bone were determined via micro CT image-based 3D finite element analysis. The simulator was evaluated by five dentists from the Department of Implantology at Tokyo Dental College. The ability of the evaluators to distinguish the drilling resistance through different regions of the mandibular bone was investigated. Of the five dentists, four sensed the change in resistance when the drill perforated the upper cortical bone. All five dentists were able to detect when the drill made contact with lingual cortical bone and when the lingual bone was perforated. This project successfully developed a dental implant surgery simulator that allows users to experience the forces necessary to drill through types of bone encountered during osteotomy. Furthermore, the researchers were able to build a device by which excessive drilling simulates a situation in which the lingual cortical bone is perforated--a situation that could lead to negative repercussions in a clinical setting. The simulator was found to be useful to train users to recognize the differences in resistance when drilling through the mandibular bone. [ABSTRACT FROM AUTHOR]

Initial attachment of human oral keratinocytes cultured on yttria-stabilized tetragonal zirconia polycrystal (TZP) surfaces that were subjected to UV or oxygen plasma (02-plasma) treatment was investigated. The viability of the attached cells, mRNA expression of laminin y2 and integrin β4, distribution of laminin y2 and integrin β4, cell area, and cell morphology were assessed. The results showed that no differences in the viability of attached cells were recognized among the conditions. However, expression of laminin y2 and integrin β4 as well as cell morphology were promoted only in 02-plasma specimens even though superhydrophilicity was obtained in both the UV and 02-plasma specimens compared with the untreated control specimen. The photocatalytic activity was believed to be closely involved in the above-mentioned differences. The results of this study suggest that TZP surface treated with oxygen plasma promotes the initial attachment capability of human oral keratinocytes with enhancing the extracellular matrix such as laminin y2. [ABSTRACT FROM AUTHOR]

The influence of a thin carbonate-containing hydroxyapatite (CA) coating to tetragonal zirconia polycrystal (TZP) on osteoblastlike cell response was investigated. TZP disks were subjected to blasting and acid etching. Thin CA coatings were deposited by the molecular precursor method (TZP-CA). Initial cell adhesion of mouse osteoblast-like cells MC3T3-E1 was enhanced, and marked progress of actin filaments was observed on TZP-CA compared to on TZP. After 3, 5 or 7 days, cell proliferation on TZP-CA was significantly higher than that on TZP. Alkaline phosphatase activity was slightly lower on TZP-CA than on TZP at 7 days, and no difference was observed at 14 or 21 days. At 28 days incubation, collagenous fibers with mineral precipitants accompanied by phosphorous and amino groups were observed. These results indicate that thin CA coating with molecular precursor method offers promise as a means of enhancing cell response, particularly initial adhesion and proliferation of MC3T3-E1 cells. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the retention of fiber-reinforced composite (FRC) posts luted with either conventional or self-adhesive resin cement. The FRC posts and core resin were built up in bovine teeth. The posts were luted with standard etch-and- rinse cement, self-etch cement, or one of two self-adhesive cements. The samples were stored in water for 1 or 14 days or subjected to thermal cycling (TC). Retention value was measured with the pull-out test using a universal testing machine. Conventional adhesive resin cement yielded significantly greater retention than self-adhesive resin cement at 1 day. No significant difference was observed in retention among the adhesive systems tested at 14 days or after TC. During the early luting stage, self-adhesive resin cement yielded lower retention value than conventional resin cement. After 14 days storage or TC, retention was comparable to that with conventional resin cement. [ABSTRACT FROM AUTHOR]

The aim of this study was to elucidate the association between the bone structure at implant insertion sites and stress distribution around the mandibular canal by means of three-dimensional finite element (3D FE) analysis. Four FE models were created with slice data using micro-computed tomography (micro-CT), and 3D FE analysis was performed. Mechanical analysis showed that the load reached the mandibular canal via the trabecular structure in all FE models. High levels of stress were generated around the mandibular canal when the distance between the mandibular canal and the implant decreased. High stress levels were also observed when cortical bone thickness and bone volume/total volume (BV/TV) were low. Our findings suggest that load is transmitted to the mandibular canal regardless of differences in the thickness of cortical bone or cancellous bone structure, but excessive load may be generated in bone with thin cortical and coarse cancellous structures. [ABSTRACT FROM AUTHOR]

Hot isostatic pressing processed yttria-stabilized tetragonal zirconia polycrystal (HIP Y-TZP) has the potential for application to implants due to its high mechanical performance. The aim of this study was to investigate the influence of surface treatment of HIP Y-TZP on cyclic fatigue strength. HIP Y-TZP specimens were subjected to different surface treatments. Biaxial flexural strength was determined by both static and cyclic fatigue testing. In the cyclic fatigue test, the load was applied at a frequency of 10 Hz for 10S cycles in distilled water at 37°C. The surface morphology, roughness, and crystal phase of the surfaces were also evaluated. The cyclic fatigue strength (888 MPa) of HIP Y-TZP with sandblssting and acid-etching was more than twice that of Y-TZP as specified in ISO 13356 for surgical implants (320 MPa), indicating the clinical potential of this material. [ABSTRACT FROM AUTHOR]

The objective of this study was to clarify the effect of surface topography on osteoblast-like cell behavior on yttria stabilized tetragonal zirconia polycrystals (TZP). Mirror-polished; blasted with 50- or 150-μm alumina (SB50 and SB150); and SB150 acid-etched with hydrofluoric acid (SB150E) were prepared on TZP. Initial attachment, proliferation and differentiation of MC3T3-E1 were evaluated. The scanning electron microscopy and Sdr (developed interfacial area ratio) values indicated that both micro- and nano-topographies produced on the SB150E surfaces. Although no clear differences were observed in initial cell attachment among specimens, the proliferation rate and expression of ALP activity on the SB150E specimens was significantly higher than that on the other specimens. These results indicate that the creation of micro- and nano-topographies on TZP by surface treatment offers a promising method of enhancing the proliferation and differentiation of MC3T3-E1 cells. [ABSTRACT FROM AUTHOR]

Tetragonal zirconia polycrystals (TZP) has drawn attention as a potential alternative to titanium (Ti) in dental implant treatment, as it minimizes both allergic reactions and esthetic problems. It is also important for dental implants to maintain plaque-free surfaces to prevent peri-implantitis. The purpose of this study was to investigate in vitro adherence of periodontopathic bacteria to TZP comparing with Ti. Periodontopathic bacteria were cultured on polished discs of two kinds of TZP, and Ti as a control. After incubation, the numbers of adherent bacteria were estimated. No significant differences among specimens were observed in the initial attachment, although a decrease was observed in initial attachment to saliva-coated specimens. In the bacterial colonization, no significant differences were recognized among specimens. The adherence of the periodontopathic bacteria on TZP was similar to that on Ti. These results suggest that a strategy is required for inhibition of the bacterial adherence to TZP. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare corrosion behavior in several titanium alloys with immersion in acidulated saline solutions containing hydrogen peroxide. Seven types of titanium alloy were immersed in saline solutions with varying levels of pH and hydrogen peroxide content, and resulting differences in color and release of metallic elements determined in each alloy. Some alloys were characterized using Auger electron spectroscopy. Ti-55Ni alloy showed a high level of dissolution and difference in color. With immersion in solution containing hydrogen peroxide at pH 4, the other alloys showed a marked difference in color but a low level of dissolution. The formation of a thick oxide film was observed in commercially pure titanium showing discoloration. The results suggest that discoloration in titanium alloys immersed in hydrogen peroxide-containing acidulated solutions is caused by an increase in the thickness of this oxide film, whereas discoloration of Ti-55Ni is caused by corrosion. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the bone regeneration properties of titanium fibre mesh as a tissue engineering material. A thin hydroxyapatite (HA) coating on the titanium fibre web was created using the developed molecular precursor method without losing the complex interior structure. HA-coated titanium fibre mesh showed apatite crystal formation in vitro in a human osteoblast culture. Titanium fibre mesh discs with or without a thin HA coating were implanted into rat cranial bone defects, and the animals were killed at 2 and 4 weeks. The in vivo experience revealed that the amount of newly formed bone was significantly higher in the HA-coated titanium fibre mesh than in the non-coated titanium fibre mesh 2 weeks after implantation. These results suggest that thin HA coating enhances osteoblast activity and bone regeneration in the titanium fibre mesh scaffold. Thin HA-coating improved the ability of titanium fibre mesh to act as a bone regeneration scaffold. [Copyright &y& Elsevier]

The objectives of this study were to characterize change in surface properties of tetragonal zirconia polycrystals (TZP) after hydrophilic treatment, and to determine the effect of such changes on initial attachment of osteoblast-like cells. Roughened surfaces were produced by alumina-blasting and acid-etching. Hydrophilic treatment comprised application of immediately after blasting and acid-etching (Blast/Etch), oxygen plasma (O2-Plasma), ultraviolet light (UV). Specimens stored in air were used as a control. The water contact angle was determined and surface analysis was performed using an X-ray photoelectron spectroscopy. Blast/Etch, O2-Plasma and UV specimens showed superhydrophilicity, and these hydrophilic treatments to TZP elicited a marked decrease in carbon content and an increase in hydroxyl groups. Hydrophilic treatments enhanced initial attachment of osteoblast-like cells and a change in cell morphologies. These results indicate that Blast/Etch, O2-Plasma, or UV treatment has potential in the creation and maintenance of superhydrophilic surfaces and enhancing initial attachment of osteoblast-like cells. [ABSTRACT FROM AUTHOR]

The aim was to investigate the local osteogenic effect of fluvastatin incorporated into a biodegradable gelatin-hydrogel (GH) scaffold. The GH scaffolds were prepared through crosslinking by ultraviolet irradiation followed by freeze-drying. Two circular defects were surgically created on fifteen-week-old male rats calvaria. All defects of each rat were randomly filled with two of three treatments, specifically: fluvastatin incorporated into a GH disk (Flu-GH), distilled water incorporated into a GH disk, and no treatment. New bone formation was quantitatively analyzed after 7, 14, and 28 days using a micro-computed tomography (micro-CT) system, and histologically observed. Evaluation by micro-CT revealed a significant difference in new bone formation among the three kinds of defect. A highly osteogenic effect was observed in the Flu-GH group. The results showed that the fluvastatin incorporated into a biodegradable GH scaffold promoted osteogenesis in rat calvarial bone, indicating its potential for bone regeneration. [ABSTRACT FROM AUTHOR]

Initial attachment of human oral keratinocytes (HOKs) cultured on mirror-surfaced commercially pure titanium (Ti) or yttria-stabilized tetragonal zirconia polycrystals (TZP) was investigated. Numbers of viable attached HOKs, their mRNAs and proteins expression of laminin y2 and integrin β4 were evaluated using the WST-1 assay, quantitative real-time PCR and enzyme-linked immunosorbent assay, respectively. Localization of laminin y2 and integrin β4 was observed using immunofluorescent staining. Cell spreading was evaluated by measuring the perimeter of actin on fluorescent stained images, and cell morphology was examined using scanning electron microscopy. At 1 h TZP elicited less of initial attachment than Ti in terms of mRNAs expression and proteins expression of laminin y2 and integrin β4 (p<0.05). However, at 48 h TZP was showed similar initial attachment in comparison to Ti. Therefore, it was suggested that TZP has a potential to form epithelial attachment like Ti. [ABSTRACT FROM AUTHOR]

In all-ceramic restorations involving a zirconia framework, surface treatment of the zirconia surface is required to enhance bonding strength with the veneering ceramics and thus prevent chipping. The purpose of the present study was to investigate the influence of surface roughness and heat treatment of the zirconia and use of liner porcelain on bond strength between veneering ceramics and a zirconia framework. Debonding/crack-initiation strength (tb) was determined according to ISO 9693. No significant difference was observed among conditions, except with use of a liner under heat treatment, which yielded a tb of 26.0±2.9-28.9±1.7 MPa. Electron probe microanalysis revealed that components of the veneering ceramics remained on the zirconia surface after debonding, suggesting that fractures occur in the veneering ceramics and that improving the strength of the veneering ceramics themselves might increase bond strength. [ABSTRACT FROM AUTHOR]

The aim of this study was to quantitatively clarify the c-axis alignment of biological apatite (BAp) crystallites (hereafter referred to as BAp alignment) in the cortical bone of the human mandible first molar. Six mandible specimens were collected from the cadavers of six dentulous Japanese adults (mean age, 63.0+12.1 years) held at the Department of Anatomy, Tokyo Dental College. A microbeam x-ray diffraction system was used to determine BAp alignment in the mesiodistal direction. Bone mineral density (BMD) was also measured using 3-dimensional trabecular structure measurement software. The results showed that the degree of BAp alignment in the mesiodistal direction was low in the alveolar area and high at the base of the mandible, suggesting that BAp alignment in the alveolar area is affected by occlusal force. Moreover, it was observed that the correlation between BAp alignment and BMD was small, indicating that BAp alignment and BMD could be independent factors. Therefore, determining BAp alignment was important in the evaluation of bone quality, including bone strength. [ABSTRACT FROM AUTHOR]

A zirconia-binding peptide motif was identified using a peptide phage display system. Yttria stabilized zirconia beads and discs were used as the target. Quartz crystal microbalance was used to monitor the binding of phages to zirconia. Starting from a library of phages displaying random sequences of 12-mer peptides, we repeated cycles of biopanning against zirconia beads. After four cycles of biopanning, we isolated a phage clone Φ#17. DNA sequencing of the corresponding portion of Φ#17 unexpectedly revealed that it displayed a 58-mer peptide (amino acid sequence: WMPSDVDINDPQGGGSRPNLHQPKPAAEAASKKKSENRKVPFYSHSWYSSMSEDKRGW). We found that Φ#17 had a 300-fold, significantly higher binding affinity for zirconia discs than phages displaying no peptide. In quartz crystal microbalance assay, a rapid increase in energy dissipation was observed from Φ#17 but not from the control phages, indicating that Φ#17 binds to the surface of zirconia via its displayed peptide. We successfully identified a peptide motif that binds zirconia. [ABSTRACT FROM AUTHOR]

Summary: Since biomaterials contact many different tissues, those materials must have optimum surface compatibility with the host bone tissue and soft tissue, as well as anti-microbial properties on an exposed region of the mucosa. Such materials can be created under well-controlled conditions by modifying the surfaces of materials that contact those tissues. This paper is focused on the surface modification of biomaterials for developing “Bio-functional dental implants”, which are compatible with all host tissues, using a cold-plasma technique. At the bone tissue/implant interface, a thin calcium phosphate coating and rapid heating with infrared radiation were effective in controlling the dissolution without cracking the coating. These thin calcium phosphate coatings may directly promote osteogenisis, but also enable immobilization and subsequent drug delivery system (DDS) of bisphosphonates. Simvastatin is also an effective candidate that is reported to increase the expression of BMP-2. The thin-film of hexamethyldisiloxane (HMDSO) was plasma-polymerized onto titanium, and then HMDSO surface was activated by O2-plasma treatment. A quartz crystal microbalance (QCM-D) technique demonstrated that simvastatin was immobilized on the plasma-treated surfaces due to introduction of O2-functional groups. At the soft tissue/implant interface, multi-grooved surface topographies and utilizing the adhesive proteins such as fibronectin or laminin-5 may help in providing a biological seal around the implant. At the oral fluid/implant interface, an alumina coating, F+-implantation and immobilization of anti-microbial peptides were responsible for inhibiting the biofilm accumulation. [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the flexural properties of three kinds of experimental fiber-reinforced composite (FRC) posts and to evaluate their potential use as posts. Experimental FRC posts were fabricated with glass, aramid, and UHMWP fibers. Commercial FRC posts were used for comparison. A three-point bending test was performed at a crosshead speed of 1 mm/min. Experimental glass fiber posts showed significantly higher flexural strengths and moduli than aramid and UHMWP posts. Experimental UHMWP posts demonstrated superior toughness to the commercial posts. The glass fiber posts displayed stiff, strong and brittle features, while the UHMWP posts were flexible, weak and ductile. The flexural properties of the aramid posts fell between those of the glass and UHMWP posts. In conclusion, the glass fiber posts proved excellent in flexural strengths and moduli. However, the superior toughness of UHMWP fibers suggests the possibility of their use as posts in combination with glass fibers. [ABSTRACT FROM AUTHOR]

The mechanical properties of a series of binary Ti-Cr alloys were investigated. Chromium content ranged from 5 to 20 mass%. Dumbbell- and disk-shaped specimens of each alloy were obtained by casting for mechanical testing and microstructural observation. Yield strength (YS) at 0.2%, tensile strength (TS), elongation (EL) and Vickers hardness (Hv) were determined. The TS and YS of Ti-l5Cr were similar to those of Ti-20Cr at approximately 880 or 900 MPa and higher than those of cp-Ti by nearly 55%. Among all Ti-Cr alloys, Ti-l0Cr showed the lowest EL. At 50 μm below the surface, Hv ranged from 370 to 420. Addition of 15 or 20 mass% chromium to titanium yielded sufficient strength and relatively high elongation values. Judging from the results of the mechanical properties, the suitability of Ti-Cr alloys with 15 or 20 mass% chromium for use in dental prostheses. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the durability of unidirectional and bidirectional fiber-reinforced post systems under static and cyclic loading. Three prefabricated fiber posts with one of two core composite resins each or a post resin were used. Each specimen was subjected to a three-point bending test after cyclic loading (1000 times) by 0.1, 0.2 or 0.3 mm deflection. Under cyclic loading, flexure strength and elastic modulus tended to show a decrease with increase in deflection in the unidirectional fiber post specimens. No such tendency, however, was observed in the bidirectional fiber post specimen. In conclusion, use of a prefabricated fiber post in a post-and-core complex improved the flexural properties of the core composite resin, regardless of fiber direction. Although deterioration in flexural properties was observed with cyclic loading in the unidirectional fiber post specimens, no significant difference was observed in the bidirectional fiber post specimen. [ABSTRACT FROM AUTHOR]

This study examined the mechanical properties of roots combined with prefabricated fiber post. Three types of specimens were evaluated: (1) prefabricated fiber post alone (FP); (2) core composite resin with FP (CFP); and (3) root with CFP (RCFP). The volume fractions of the prefabricated fiber post in the core composite resin (FP/CFP ratio) were set to 0, 0.16, 0.22, 0.28, and 0.48. Bending test for FP and CFP, and diametral compression test for FP, CFP, and RCFP were carried out. The FP/CFP ratio showed no effect on the diametral tensile strength (DTS) of RCFP; and there were no significant differences in DTS with/without FP. The flexural strength of CFP increased with increase in FP/CFP ratio. The DTS of CFP declined in comparison with that of core composite resin only. [ABSTRACT FROM AUTHOR]

Enhanced adhesion and migration of osteoblastic cells on titanium (Ti) surface is believed to increase the success rate of implant therapy. A GRGDSP peptide derived from fibronectin was coated on Ti surfaces using a tresyl chloride activation technique, and then MC3T3-E1 osteoblastic cells were cultured on the Ti surfaces. After 15 days, total RNA was isolated from the cells and gene expression level were analyzed by Affymetrix GeneChip system. The expression levels of many genes in MC3T3-E1 cells cultured on GRGDSP-coated Ti surface were altered when compared to uncoated Ti. In particular, the elevated mRNA levels of bone sialoprotein (BSP) and osteocalcin (OC) were successfully confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. In light of the results obtained, GRGDSP-coated Ti presented the potential of evolving into a useful biomaterial for successful implant therapy. [ABSTRACT FROM AUTHOR]

Abstract: Dental pulp has various characteristics in the pulp chamber, but only a few biological evaluations about the effect of age on dental pulp tissue have been reported. The purpose of this study was to compare dental pulp from young and adult rats to characterize the homeostatic mechanism. Dental pulp cells (DPCs) were obtained from the first molar of rats, weighing 150 g each for the young group and 350 g each for the adult group. The expression of core-binding factor alpha-1 (Cbfa-1), vascular endothelial growth factor (VEGF), or heat shock protein (HSP) 27 messenger RNAs (mRNAs) by cultured pulp cells was determined by using a quantitative real-time PCR system after 3, 7, or 14 days. The expression of Cbfa-1 mRNA in the young group was higher than in the adult group. Expression of VEGF and HSP27 mRNAs in the adult group was higher than in the young group. The self-defense system in young DPCs is undertaken by calcification, but in adult DPCs it is carried out by the expression of self-defense proteins and the regeneration of vessels. [Copyright &y& Elsevier]

This study compared differences in discoloration and dissolution in several titanium alloys with immersion in peroxide- or fluoride-containing solution. Commercially pure titanium (CP-Ti) and six titanium-based alloys were used: Ti-0.15Pd, Ti-6Al-4V, Ti-7Nb-6Al, Ti-55Ni, Ti-10Cu, and Ti-20Cr. Two test solutions were prepared for immersion of polished titanium and titanium alloys: one consisting of 0.2% NaF + 0.9% NaCl (pH 3.8 with lactic acid) and the other of 0.1 mol/l H2O2 + 0.9% NaCl (pH 5.5). Following immersion, color changes were determined with a color meter and released elements were measured using ICP-OES. Discoloration and dissolution rates differed between the two solutions. In the hydrogen peroxide-containing solution, color difference was higher in Ti-55Ni and Ti-6Al-4V than in any of the other alloys, and that Ti-55Ni showed the highest degree of dissolution. In the acidulated fluoride-containing solution, CP-Ti, Ti-0.15Pd, Ti-6Al-4V, Ti-7Nb-6Al, and Ti-10Cu alloys showed remarkable discoloration and dissolution with immersion. On the contrary, Ti-20Cr alloy showed very little discoloration and dissolution in either solution. [ABSTRACT FROM AUTHOR]

Fibronectin (FN) can be immobilized directly on titanium surfaces using tresyl chloride activation technique. The key advantage of tresyl chloride activation technique lies in its simplicity. In this study, we examined the cell attachment and gene expression of MC3T3-E1 cells on FN-immobilized titanium using GeneChip. Cells attached on FN-immobilized titanium at a higher rate than untreated titanium. FN altered the gene expression profile, whereby 62 genes were found to be up-regulated, while 56 genes were found to down-regulate to over twice the level on day 14. FN not only enhanced the expression levels of IBSP and OMD, but also decreased SULF1 mRNA level. Taken together, the immobilization of FN on tresylated titanium promoted early matrix mineralization and bone formation. [ABSTRACT FROM AUTHOR]

Simvastatin acid (SVA) has been reported to stimulate bone formation by increasing expression of BMP-2 in osteoblasts. Due to their multi-functional characteristics and bioadaptability, cyclodextrins (CDs) are capable of forming inclusion complexes with many drugs by including a whole drug molecule inside their cavity. In the present study, we prepared SVA/CD inclusion complex solutions with different pH values. These were then used to determine their SVA release behavior after coating on titanium substrates, as well as to clarify the characteristics of SVA/CD complexes per se. Results showed that the lower the pH value of the solution, the lower the release kinetics of SVA. Besides, the amount of crystalline complexes in the coatings increased with decrease in pH. These results suggested that the release rate of SVA depended on two factors: pH of the solution and concomitant crystallinity of the coating. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the retention force of FRC posts which were built up using direct and direct-indirect fabrication techniques with two fiber-reinforced core build-up systems (FibreKor and i-TFC). Posts were cemented in endodontically treated bovine single roots with resin cement using either direct or direct-indirect technique. Following which, the retention force of post-and-cores and fracture sites were examined. It was found that both the retention force and fracture site depended on the fabrication technique and resin cements. Post-and-cores built up with direct-indirect technique had greater retention force than those fabricated using direct technique. Fracture modes most frequently observed were adhesive failure at Resin/Dentin interface, a mixture of adhesive failures at Post/Resin and Resin/Dentin interfaces as well as cohesive failure of resin cements. Based on the results of this study, we concluded that when it comes to post-and-core build-up for endodontically treated tooth, the direct-indirect technique is more effective than the direct technique on the retention force of FRC posts. [ABSTRACT FROM AUTHOR]

Background: The seal between an implant and the oral epithelium is an important factor for successful implant therapy. The purpose of this study was to evaluate the initial attachment and subsequent behavior of rat oral epithelial (OE) cells on pure titanium (Ti) used for dental implants. Methods: OE cells derived from 4-day-old rats were cultured on Ti, polystyrene culture dishes, and glass coverslips. The number of attached cells, cell areas, number of colonies, and proliferation rates were measured. Additionally, immunostaining of vinculin and laminin-5 (LN5) was performed, and LN5-immunoreactive areas were measured. Results: After 24 hours of culture, there were fewer cells attached to the Ti than to the polystyrene dishes or glass coverslips, and the area of cells was greater on the polystyrene than on the Ti or glass. OE cells reached their maximum proliferation rate after 45 hours of culture on the polystyrene and glass, and after 72 hours on Ti. LN5 was deposited behind cells as they migrated, and the LN5-immunoreactive area was smaller on Ti than on polystyrene after 96 hours of culture. Conclusions: The initial attachment of OE cells to Ti was inferior to that on polystyrene or glass, and the OE cell migration area indicated by the deposition of LN5 was smaller on Ti than on the other materials. Therefore, this study suggests that further improvement of Ti surface properties is needed for rapid attachment and spreading of oral epithelium to dental implants. [ABSTRACT FROM AUTHOR]

Background: The role played by the internal basal lamina (IBL} and hemidesmosomes between an implant and the peri-implant epithelium (PIE) in the adherence of the epithelium to the implant is controversial. This study used rat maxilla implantation models to clarify the ultrastructure of the PIE-implant interface. Methods: Ti-6AI-4V implants were inserted either immediately or 2 weeks after the extraction of the upper left first molar of 6- or 4-week-old rats, respectively. The junctional epithelium (JE) of the upper right molars in the same animals was used as a control. Four weeks after implantation, the animals are sacrificed to prepare specimens for light and immunoelectron microscopy. Results: Under light microscopy, the PIE appeared to attach to the implant surface. Ultrastructurally, IBL, consisting of the lamina densa and lamina lucida, and hemidesmosomes were formed only in the lower region, and rarely in the middle region, of the PIE-implant interface. In control teeth, the IBL and hemidesmosomes formed throughout the dento-JE interface. Laminin-1 was found in the IBL and also in the vesicles and vacuoles of the PIE and JE cells. Statistical analysis showed that there was also a significant difference in the amount of IBL between the PIE-implant and dento-JE interfaces. Conclusions: PIE attached to the implant via hemidesmosomes and IBL in the lower region of the PIE-implant interface. Although PIE cells may secrete laminin-1, which contributes to epidermal cell adhesion, the PIE which attaches to implants only in the lower region of the interface is considered to be the poorly adhered epithelium. [ABSTRACT FROM AUTHOR]