β-TCP can stimulate bone formation;however, its molecular mechanism is unclear. In this study, an implant drill was used to make bone defects in Beagle dog mandible, and β-TCP was filled into the bone defects. After isolation of mRNA, gene expression levels were monitored by dog DNA microarray. The gene expression of decorin was enhanced by β-TCP, and decorin gene expression was increased through TGF-β by β-TCP. An immunohistochemical study demonstrated that the decorin protein was also increased by β-TCP, since decorin binds with TGF-β and plays a role in osteoblast maturation. Taken together, the stimulation of decorin expression by β-TCP might be a part of the mechanism in accelerating bone formation.
We developed a hypothesis that dissoluble absorption and giant cellular absorption are indispensable for bio- ceramics harmonized with bone remodeling. The aim of this study was to investigate the characteristics of porous and modified ceramics and the number of giant cells in subcutaneous tissue. Commercial products of b-tricalcium phosphate (β-TCP (porosity:75%)) were easily modified to functionally graded calcium phosphate ceramics by the partial dissolution–precipitation (PDP) technique, which involved a stirring of 300 rpm in 2% HNO3 solutions (50 cm3) containing Ca2＋ and PO43- ions and a supersonic treatment at 120 W and 38 kHz in the same solutions. The dissolution efficiency of porous bTCP block by the supersonic treatment drastically increased with time, depending on the porosity of ceramics. For even dense β-TCP block, enhancement of micro-pores and propagation of nano-cracks were recognized by the supersonic treatment for 7 min.
After the specific PDP technique, Nano-crystals of HAp were successfully precipitated on all over the pore wall surface in the macro- and micro-pores of the ceramics. The PDP-TCP (Partial Dissolution-Precipitation technique-TCP) ceramics were implanted into the back subcutis in 4 week-old Wistar rats. At 3 weeks after the implantation, the PDP-TCP exhibited a significant increase in the number of osteoclast-like giant cells and better affinity for body fluid than original β-TCP products. The results suggested that our PDP treated β-TCP could have a potential for a bioactive scaffold with good giant cell-absorption.
In this work, the authors investigated the process of bone regeneration with the aid of woven cloth made of bioactive glass fibers, BGF-1. Bone defects made in the tibial bones of Wistar rats were covered either with BGF-1 glass cloth or industrial E-glass cloth for 2 to 3 weeks, and then histological observations were made. As for the results, bone formation was recognized in the bone defects covered with the BGF-1 glass cloth, while it was not recognized in the defects covered with the Eglass cloth. From the results of the implantation of the fibers into the hypodermal tissue, BGF-1 fibers were considered to be slowly resorbed in the living body since the fibers were subjected to phagocytosis by giant cells. BGF-1 fibers were shown to be capable of ion exchange with oxonium ions to give off sodium and calcium ions, which is an essential characteristic for bioactive glass. From the E-glass cloth, on the other hand, the extent of the ion exchange was very small. The controlled release of sodium and calcium ions from BGF-1 was considered to be sufficient for the emergence of bioactivity.
Atmospheric-pressure plasma (AP plasma) treatment is a low-temperature plasma treatment, and can create super-hydrophilicity on a titanium surface by decomposing hydrocarbon and introducing the hydroxyl group. AP plasma has unique features, including that this treatment can be performed while being exposed to the air, and create super-hydrophilicity on a titanium surface within an extremely short time due to its high energy compared to UV treatment. Accordingly, this treatment is expected to be used for clinical applications. This study aimed to investigate the effect of AP plasma treatment on surface properties of commercial titanium implants that have different surface morphology and physicochemistry, and to verify the availability of this treatment for clinical use.
The surfaces of 17 commercially available titanium implants were observed using an optical microscope and a scanning electron microscope, and were analyzed by Xray photoelectron spectroscopy (XPS). These implants were subjected to AP plasma treatment and evaluated the change in surface chemical compositions including carbon contents and surface wettability with contact angle measurements. The AP plasma treatment was carried out for 5 s along the sides of the implants that were retained at a location 10 mm from the exhaust nozzle of AP plasma.
The surfaces of the 17 commercial implants have various surface morphologies and chemical compositions, and were classified into machining with lathe, blast＋ acid etching (SLA), SLA＋ hydrophilization, spark anodic-oxidation and HA/Blast treatment under microscopic observation, XPS analyses and contact angle measurement.
The carbon contents were decreased with AP plasma treatment. In addition, the surfaces of commercial implants with all classifications reach super-hydrophilicity that has almost zero contact angles by AP plasma treatment.
In conclusion, the results in the present study showed that the AP plasma treatment can create super-hydro-philicity on almost all the commercial implants within an extremely short time, such as 5 s, while being exposed to air, and may be utilized in the operating room immediately prior to implant placement under atmospheric conditions.
The aim of this study was to examine the possibility of repeated heat-pressing of pressable glass-ceramic by evaluating the influence of repeated heat-pressing on mechanical properties, surface characteristics and dimensional accuracy.
A commercially available pressable glass-ceramic system (IPS e.max Press, Ivoclar Vivadent, Liechtenstein) was selected in this study. Disc samples with 12.5 mm in diameter and 1.3 mm in thickness were heat-pressed and used as the first heat-pressing specimens. Sprue and button parts of the first heat-pressed specimens were retrieved, and they were used to construct the second heat-pressed specimens. The third heat-pressing groups were constructed in just the same way as the second heat-pressing groups. All the heat-pressing procedures were performed according to the manufacturers' instructions. After the arithmetic mean surface roughness (Ra) of pressed specimens was measured, a biaxial flexural strength (BFS) of disc specimens was measured using a universal testing machine. Surface hardness, optical microscopic and scanning electron microscopic observations were carried out. Surface characteristics were examined with X-ray diffractometry (XRD) and electron probe microanalysis (EPMA). The dimensional accuracy of a heat-pressed full crown was also evaluated.
The Ra values ranged from 4.0-4.3 μm of all heat-pressing groups. The BFS values obtained were 346±29 MPa, 312±24 MPa and 305±20 MPa for the first, second and third heat-pressing group, respectively. The third heatpressing group showed a lower BFS mean than the first heat-pressing group (p=0.038). Surface hardness showed around 540 Hv in all heat-pressing groups. Microscopic observations revealed that small amounts of porosity were observed in all heat-pressing groups with no differences among the number of heat-pressings, and that the apparent lithium disilicate crystals were confirmed by XRD. A compositional change was not recognized in all heatpressing specimens by EPMA. The dimensional change of all heat-pressed full crowns ranged from ＋0.16-0.19% with no differences among the number of heat-pressings.
These results demonstrated that the repeated heatpressing of pressable glass-ceramics used in this study was available with a slight decrease in strength and no differences in surface characteristics and dimensional accuracy.