Bio-Medical Materials and Engineering - Volume 20, issue 5

Authors: Chandran, Deepa T. | Jagger, Daryll C. | Jagger, Robert G. | Barbour, Michele E.

Article Type: Research Article

Abstract: Dental impression materials are used to create an inverse replica of the dental hard and soft tissues, and are used in processes such as the fabrication of crowns and bridges. The accuracy and dimensional stability of impression materials are of paramount importance to the accuracy of fit of the resultant prosthesis. Conventional methods for assessing the dimensional stability of impression materials are two-dimensional (2D), and assess shrinkage or expansion between selected fixed points on the impression. In this study, dimensional changes in four impression materials were assessed using an established 2D and an experimental three-dimensional (3D) technique. The former involved …measurement of the distance between reference points on the impression; the latter a contact scanning method for producing a computer map of the impression surface showing localised expansion, contraction and warpage. Dimensional changes were assessed as a function of storage times and moisture contamination comparable to that found in clinical situations. It was evident that dimensional changes observed using the 3D technique were not always apparent using the 2D technique, and that the former offers certain advantages in terms of assessing dimensional accuracy and predictability of impression methods. There are, however, drawbacks associated with 3D techniques such as the more time-consuming nature of the data acquisition and difficulty in statistically analysing the data. Show more

DOI: 10.3233/BME-2010-0638

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 5, pp. 243-249, 2010

Authors: Cheng, Fang-Hsin | Shih, Shih-Liang | Chou, Wen-Kai | Liu, Chien-Lin | Sung, Wen-Hsu | Chen, Chen-Sheng

Article Type: Research Article

Abstract: The role of the vertebral body's rotation and the loading conditions of the brace has not been clearly identified in adolescent idiopathic scoliosis. This study aimed to implement a finite element (FE) model of C-type scoliotic spines to investigate the influence of different loading conditions on variations of Cobb's angle and the vertebral rotation. The scoliotic FE model was constructed from C7 to L5, and its geometry was the right thoracic type (37.4°) with an apex over T7. Three loading conditions included a medial–lateral (ML) and anteroposterior (AP) force with a magnitudes of 100–0, 80–20 and 60–40 N. Those …forces were respectively applied over the 6th, 7th and 8th ribs. According to an analysis of Cobb's angle, the 100 N ML force that was applied over the 8th rib could achieve the best correction effect. Furthermore, the ML force was dominant in alterations of Cobb's angle, whereas the AP force was dominant in alterations of the axial vertebral rotation. Additionally, the level below the apex was the most appropriate level to apply the force to correct C-type scoliosis. Show more

Keywords: Scoliosis, loading condition, Cobb's angle, finite element analysis

DOI: 10.3233/BME-2010-0639

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 5, pp. 251-259, 2010

Authors: Afshari, Elnaz | Najarian, Siamak | Simforoosh, Nasser

Article Type: Research Article

Abstract: Artificial tactile sensing is a novel method for obtaining different characteristics of a hard object embedded in a soft tissue. In this regard, artificial palpation is one of the most valuable achievements of artificial tactile sensing that can be used in various fields of medicine and more specifically in surgery. In this study, considering the present problems and limitations in kidney-stone-removal laparoscopy, a new application will be presented for artificial tactile sensing approach. Having imitated surgeon's palpation during open surgery and modeled it conceptually, indications of stone existence that appear on the surface of kidney (due to exerting mechanical …load) were determined. A number of different cases were created and solved by the software. Using stress distribution contours and stress graphs, it is illustrated that the created stress patterns on the surface of kidney not only show the existence of stone inside, but also its exact location. In fact, the reliability and accuracy of artificial tactile sensing method in detection of kidney stone during laparoscopy is demonstrated by means of finite element analysis. Also, in this paper, the functional principles of tactile system capable of determining the exact location of stone during laparoscopy will be presented. Show more

Keywords: Artificial tactile sensing, artificial palpation, kidney stone, laparoscopic surgery

DOI: 10.3233/BME-2010-0640

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 5, pp. 261-267, 2010

Authors: Sivak, Wesley N. | Zhang, Jianying | Petoud, Stéphane | Beckman, Eric J.

Article Type: Research Article

Abstract: Naphthalene analogs with differing hydroxyl and amine functionality were incorporated into degradable polyurethane foams synthesized from lysine diisocyanate and glycerol to determine if chemical structure can be used in controlled release systems. Excitation and emission spectra of the various naphthalene analogs in aqueous solution were collected to ensure they were capable of being quantitatively detected in aqueous solution at low concentrations. The fluorescence stability of the compounds was assessed over a 2-week period at 70°C; the analogs were all found to exhibit signal decay to varying degrees. Polyurethane foam materials containing the naphthalene analogs were synthesized and examined via scanning …electron microscopy; incorporating naphthalene ligands did not grossly alter the polyurethane morphology. The analog distribution was then assessed via fluorescence microscopy, and the naphthalene analogs were found evenly dispersed throughout the polyurethane materials. Foam samples containing various analogs were then incubated in PBS buffer solution (pH 7.4) at 4, 22, 37 and 70°C for 11-weeks. Temperature dependent release of naphthalene analogs from the polyurethane foams was found to depend upon the functional groups present on the naphthalene analog. These results suggest that the chemical structure of a drug plays a unique role in controlling release from hydrolytically degradable drug delivery systems. Show more

Keywords: Drug delivery, controlled release, naphthalene, polyurethane, lysine diisocyanate

DOI: 10.3233/BME-2010-0641

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 5, pp. 269-281, 2010

Authors: Nakamura, Yoshiharu | Sato, Hideaki | Ohtsuka, Masaki | Hojo, Satoru

Article Type: Research Article

Abstract: Polycrystalline diamond (PCD) exhibits excellent abrasive characteristics and is commonly used as loose grains for precision machining of hard ceramics and other materials that are difficult to grind and polish. In the present study, we investigated using bonded PCD for polishing dental porcelain, for which a lustrous surface is difficult to obtain by polishing. We compared the surface texture and characteristics of dental porcelain after polishing with bonded PCD with that obtained using bonded monocrystalline diamond (MCD), which is commonly used for this purpose. Polishing was performed at various pressures and rotational speeds on a custom-built polishing apparatus using bonded …PCD or MCD with grain sizes of 3.92 μm on specimens consisting of VITA Omega 900 dentin porcelain after firing and then glazing to a specified surface roughness. The surface roughness of the polished porcelain and the abrasion quantity in terms of its polishing depth were measured, and its surface texture and characteristics were investigated. At low polishing pressures, PCD yielded a finer polished surface than MCD. The polishing depth after polishing for 20–30 min was approximately 2–3 μm with PCD and 1–2 μm with MCD. The polished surface was more uniform and smooth with PCD than with MCD. Show more

Keywords: Polycrystalline diamond, monocrystalline diamond, dental porcelain, polishing, surface roughness

DOI: 10.3233/BME-2010-0642

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 5, pp. 283-293, 2010

Authors: Guan, Guoping | Bai, Lun | Zuo, Baoqi | Li, Mingzhong | Wu, Zhengyu | Li, Yonglin | Wang, Lu

Article Type: Research Article

Abstract: Studies on skin substitutes and dermal scaffolds have been extensively carried out in the past several decades and some commercial products derived from collagen and polymers have been in marketing. Yet little research on silk fibroin based dermal scaffolds and products has been reported so far. In the present study, therefore, porous silk fibroin scaffolds (PSFSs) have been prepared by freeze drying method. The effects of PSFSs on skin recovery from full thickness defect have been examined by histological evaluation with respect to neovascularization, dermal regeneration and infiltration of inflammatory cells. In addition, tissue compatibility between PSFSs and polyvinyl alcohol …(PVA) sponges (as control) has been semiquantitatively compared by scoring method. The results showed that at day 18 after implantation, new tissues formed in PSFSs whose structure was almost equal to normal skin structure where proportional distribution of functional blood vessels could be found. Furthermore, infiltration of inflammatory cells in PSFSs disappeared within 7 days. By contrast, a variety of interstices, fibrous encapsulization and moderate infiltration of inflammatory cells could be found in PVA sponges at day18 after implantation. In summary, PSFSs has significantly promoted the skin recovery from full thickness defect, showing fibroin's outstanding tissue compatibility. Show more

Keywords: Silk fibroin, dermal scaffolds, neovascularization, skin defect, wound healing, tissue engineering

DOI: 10.3233/BME-2010-0643

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 5, pp. 295-308, 2010