Bio-Medical Materials and Engineering - Volume 6, issue 1

Authors: Fung, K.S.M. | Chan, F.H.Y. | Lam, F.K. | Liu, J.G. | Poon, P.W.F.

Article Type: Research Article

Abstract: The application of an artificial neural network filter (ANNF) to estimate the visual evoked potential (VEP) is presented. VEP is the gross electrical response of the brain to visual stimuli. Due to the low SNR, it is difficult to extract response from individual stimulus trials. The ANNF we used estimates the deterministic component of the signal and removes the noise uncorrelated with the stimulus, even when the noise is colored. The ANNF is trained through back-error propagation with a data set consisting of a training signal and a target signal. The training signal is the raw VEP from a single …trial having a SNR of about −5 dB, while the target signal has a higher SNR which is achieved by ensemble averaging 100 stimulus trials. Simulated signals were generated to test the performance of the ANNF. Results show that the ANNF could greatly enhance the SNR of the VEP to single visual stimulus. Thus the total number of ensembles is reduced. In clinical applications, the traditional ensemble averaging method requires a hundred ensembles to determine the VEP. When ANNF is used, about 20 ensembles are sufficient for the same purpose. Show more

Keywords: Visual evoked potential (VEP), artificial neural network filter (ANNF), multi-layer perception (MLP), ensemble average (EA), latency corrected average (LCA)

DOI: 10.3233/BME-1996-6101

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 1, pp. 1-13, 1996

Authors: Miyazaki, Masashi | Oshida, Yoshiki | Xirouchaki, Loretta

Article Type: Research Article

Abstract: Currently, clinicians face choices of restorations including amalgams (mercury-based, gallium-based alloys, or mercury-free silver-based substitutes), composite resins, ceramics, and gold alloy. In order to choose an appropriate restorative material, many parameters are involved; they include preparation time requirements, finishing and polishing, marginal integrity, anatomy and contours, chipping and fracture, sensitivity, microleakage, wear resistance, and corrosion resistance. It is generally believed that amalgams are still evaluated as the best of all restorative materials as far as the aforementioned parameters are concerned. It is claimed that the amalgams exhibit in the range of 10 to 25 service years, while the composite resin …exhibits ranging between 7 and 11 service years. When a composite resin requires a mass large enough for indirect fabrication, a bonding system is demanded with which this restoration should form an instantaneous, impervious, and stable bond to the tooth structure. Roughly a quarter century has passed since the research and development of a promising dentin bonding system was initiated. We are now in the fifth generation of the dentin bonding system, during the research and development of which various types of bonding agents as well as bonding models have been introduced. In this article, the history of development of the bonding agents and the understanding of the bonding mechanism will be reviewed. Show more

Keywords: Dentin bonding agent, dentin bond strength, surface treatment, acid-etching, bonding mechanism, hybrid layer

DOI: 10.3233/BME-1996-6102

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 1, pp. 15-31, 1996

Authors: Lewis, Gladius | Manickam, Saravanakumar | Smart, Foch M.

Article Type: Research Article

Abstract: The finite element analysis method and a two-dimensional idealization were used to conduct a detailed parametric study of the stresses in and displacement of models of bonded edgewise “combination-materials” type of orthodontic brackets when subjected to loading and constraint conditions that are deemed to be the same as those that exist in vivo. A “combination-materials” type bracket is herein defined as one in which different materials are used in fabricating the main body and the archwire slot. The present study was conducted in three parts. In Part 1, 16 model cases were analyzed, involving 4 different combinations of materials (for …the main body of the bracket and its archwire slot) and 4 different overall bracket configurations (comprising main body, base and slot). The focus of Part 2 was the model bracket configuration that was, on the basis of Part 1 results, deemed to show the “optimum performance”. In this part, the parameter investigated was the value of the modulus of elasticity of the adhesive, Eadh . In Part 3, the concept of an efficiency index of the bonded bracket-archwire system, η, was introduced and explained. The dependence of η on stated characteristics of a rectangular archwire, for the “optimum performance” model, was explored. Part 1 results led to the conclusion that the “optimum performance” model has equally angulated buccal and lingual edges and the main body and archwire slot are fabricated from glass fiber-reinforced polycarbonate and stainless steel, respectively. Part 2 results showed that, for the aforementioned “optimum performance” model, the longitudinal displacement of the archwire slot is fairly insensitive to Eadh . Part 3 results showed that η is intimately related to each of the wire characteristics studied (namely cross-sectional dimensions, “interbracket distance” and modulus of rigidity of the material). Show more

Keywords: Orthodontic bracket, finite element analysis, von Mises stress

DOI: 10.3233/BME-1996-6103

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 1, pp. 33-45, 1996

Authors: Khang, Gilson | Park, Joon B. | Lee, Hai Bang

Article Type: Research Article

Abstract: A new technique for the prevention of platelet adhesion on the polysulfone (PSf) porous catheter system by means of saline perfusion was investigated. Commercially available ultrafiltration PSf hollow fibers were used as porous catheter tubes. Sixty milliliter of citrated canine blood was circulated for 20 min through the annular catheter flow cell system in vitro. Platelet adhesion onto the PSf porous catheter tube decreased sharply with increased saline solution perfusion rate. From the semilogarithmic relationship between the number of adhered platelets and perfusion rate, the critical perfusion rate for preventing adhesion of platelets could be about 0.3 ml min−1 …cm−2 . After the surface of PSf porous tubes was modified by non-ionic surfactant coating and air plasma treatment for 20 seconds without saline perfusion, the number of adhered platelets was lower than that of the control tube. These modification methods may be more effective in the prevention of initial platelet adhesion if combined with saline perfusion. Show more

Keywords: Platelet adhesion, blood compatibility, polysulfone porous catheter tube, saline perfusion, surface modification

DOI: 10.3233/BME-1996-6104

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 1, pp. 47-66, 1996

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 1, pp. 67-72, 1996