A modified porous titanium sheet prepared by plasma activated sintering for biomedical applications

This study aimed to develop a contamination free porous titanium scaffold by a plasma activated sintering within an originally developed TiN coated graphite mold. The surface of porous titanium sheet with or without a coated graphite mold was characterized. The cell adhesion property of porous titanium sheet was also evaluated in this study. The peak of TiC was detected on the titanium sheet processed with the graphite mold without a TiN coating. Since the titanium fiber elements were directly in contact with the carbon graphite mold during processing, surface contamination was unavoidable event in this condition. The TiC peak was not detectable on the titanium sheet processed within the TiN coated carbon graphite mold. This modified plasma activated sintering with the TiN coated graphite mold would be useful to fabricate a contamination free titanium sheet. The number of adherent cells on the modified titanium sheet was greater than that of the bare titanium plate. Stress fiber formation and the extension of the cells were observed on the titanium sheets. This modified titanium sheet is expected to be a new tissue engineering material in orthopedic bone repair.Comment: 5 pages, 4 figure

Micro-CT Based Quantitative Evaluation of In Vivo Bone Regeneration with Collagen-based Biomaterials

Increase of biological stability primarily determines the bone regeneration potential of the collagenbased biomaterials. Addition of calcium phosphates has been an option in reinforcement of the collagen-based biomaterials. Nano-scale β-TCP allows higher self assembly and cross-linking with collagen molecules whereas the hydroxyapatite is not suitable starting material to create bone-like collagen composite without toxic cross-linking agents. The present study investigates in vivo bone regeneration potential of two collagen-based biomaterials, namely, β-TCP/collagen composite and collagen alone. The collagen alone did not show sufficient scaffold properties. Since β-TCP/collagen composite showed better scaffold property in comparison with collagen alone, biological stability is an important determinant of collagen-based biomaterials

Experimental Paste-paste Type Phosphate-bonded Investment with Colloidal Silica Solution

Although silica is the most popular refractory material, it is known that inhaled silica powder can induce lung or respiratory diseases, potentially leading to cancer. The purpose of this study was to develop experimental paste-type phosphate-bonded investments fabricated with colloidal silica solutions. Paste 1 was prepared by mixing cristobalite powder of 80 g with 30 cc monomagnesium phosphate solution. To investigate the effects of colloidal silica solution within paste 2, three volumes (A: 20 cc, B: 25 cc, C: 30 cc) were prepared with 15 g of MgO each. Basic properties and fit of the casting were compared to commercial phosphate-bonded investment and evaluated. The setting times for A, B and C were statistically different. The quickest setting time was measured from U. The fired strength of U was remarkably greater than those of others. The setting expansion of U was obviously greater than those of the experimental investments. The average value of A was statistically higher than that for B. C expanded minimally while setting. The expansion percentages at 850ºC were no significant differences among experimental investments. In addition, that of U during the entire heating was remarkably low. The degree of the fit differed significantly between U and A because setting expansion of A was insufficient. Although the results are not optimal, the newly developed paste-paste type phosphate-bonded investments produced in this study still offer potential as alternative investment systems due to their excellent fluidity, manipulation and reasonable basic properties

Investigation of the Sol-Gel Process with Experimental Paste-Type Dental Phosphate-bonded Investments

Casting investments are used by mixing a powder and liquid, and there is a risk of fine powder inhalation causing respiratory disease. Previously, we investigated paste-paste type phosphate-bonded investment with oils. The objective of the present study was to produce paste-paste type phosphate-bonded investments with colloidal silica. Two pastes (PA and PB) were formed before the test. PA was an acidic mixture of cristobalite and magnesium dihydrogenphosphate solution, and PB was an alkaline mixture of MgO in colloidal silica solution. Five experimental investments (PB5, PB10, PB15, PB20, PB25) containing 5, 10, 15, 20, and 25 ml, respectively, of colloidal silica in PB were evaluated. Commercial phosphate-bonded investment was used as a control. PB5 took a long time to set (12 h or more), had no setting expansion, and its compressive strength was very small. Its thermal expansion and XRD analysis results were almost the same as those from the other experimental investments. The setting expansions of PB20 and PB25 were 0.40% and 0.62%, respectively, and they took approximately 16 min to set. These values were close to those of control. Full coverage cast crowns obtained from the experimental investments had a loose fit compared with the control. The gap with the crowns cast from PB20 was smaller than those of other experimental investments, and it showed no significant difference compared to that of the control. These results suggest that it is possible to produce pastepaste type investments using colloidal silica. This limited study suggests that the experimental investment with PB20 is suitable for clinical use

CAD/CAM All Ceramic Dental Restorations on Implants: A Panacea or a Challenge?

The aim of the present study was to evaluate whether all-ceramic restorations fabricated by computer-aided design and manufacturing (CAD/CAM) are a panacea for the application to conventional prostheses and implant prostheses or if there exist challenges that must be overcome first. Fracture tests of CAD/CAM milled porcelain single crowns adhered to a master abutment model were performed to evaluate mechanical durability. The fits of CAD/CAM-milled and post-sintered zirconia angled frameworks for bridge restorations (APAPA, A: abutment, P: pontic) were evaluated by measuring the cement space at the margin of the sectioned surface of the framework and abutment. The bonding strengths of porcelain (a machinable glassy ceramic) and zirconia were evaluated by measuring the bending strength of porcelain adhering to zirconia specimens and porcelain fused to zirconia specimens. A CAD/CAM-fabricated porcelain single crown seemed promising, but adhering treatment was mandatory to guarantee its durability. The fits of CAD/CAM-fabricated and post-sintered zirconia frameworks were excellent and satisfied criteria for clinical acceptance of cement-retained superstructures of implants. However, fusing porcelain to a zirconia framework in the conventional manner has several disadvantages. Therefore, we propose a new hybrid all-ceramic restoration system of CAD/CAM porcelain veneering adhering to CAD/CAM zirconia frameworks. In conclusion, CAD/CAM all-ceramic restoration alone is not yet a panacea but already a very useful tool even for implant prostheses