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Biomedical subjects

J C Knowles

Publications and source records attributed to J C Knowles.

78 records · Page 5Linked to original sources
PubMedDate not supplied

Effects of therapeutic ultrasound on osteoblast gene expression.

Ultrasound (US) is commonly used as a physiotherapy aid for a number of types of injury to soft connective tissues and for fracture healing. However, the precise effects of therapeutic US on tissue healing processes are not clearly understood, although they are likely to involve changes in key cellular functions. The present study has therefore examined the effects of several US intensity levels on the activity of two bone-associated proteins, alkaline phosphatase (ALP) and osteopontin (OP) in a human cell line, MG63, using RT-PCR. ALP showed progressively higher expression with increasing US intensities, whereas OP responded differently, showing down-regulation at 120 mW/cm2, the lowest US exposure. OP expression was considerably less affected overall compared with the relative response of ALP to the same US doses. The results show that there is a differential response to therapeutic levels of US, since ALP and OP clearly exhibited gene-specific response profiles. These findings suggest that modifying the parameters of US exposure could be used to improve repair and regeneration processes and enhance the clinical efficacy of implanted biomaterials for tissue engineering.

Journal Article↗
PubMedDate not supplied

Development of a natural degradable polymer for orthopaedic use.

Currently, there are a large variety of degradable polymers available for use in surgery, which are generally based on blends and copolymers of poly(L-lactide) (PLLA) and poly(L-glycolide) (PGA). The major demand for these materials is for suturing of wounds, but the materials are also being developed for use in orthopaedic surgery for fracture reduction. The development of these materials is on two fronts, the first involving conventional fracture fixation design of plates. The second is to produce simple devices such as rods and to use the degradable materials for treatment of specific fracture types such as fractures of the olecranon. These materials have the advantage of possessing initially enhanced mechanical properties, although their relatively quick degradation profile diminishes these properties. As an alternative we are developing polyhydroxybutyrate (PHB) and its copolymers with polyhydroxyvalerate (PHV). This range of polymers mab be easily thermally processed, are very cheap and easily available. The polymer also has the significant advantage of being piezoelectric. This is discussed.

Animals↗
PubMedDate not supplied

Investigation of the dry and wet fatigue properties of three all-ceramic crown systems.

PURPOSE: The aim of this study was to investigate the influence of fatigue on the fracture strength of In-Ceram (Vita Zahnfabrik), Optimal Pressable Ceramic (Opc, Jeneric Pentron), and IPS Empress (Ivoclar-Vivadent) in both wet and dry environments. MATERIALS AND METHODS: Twenty-six crown shapes measuring 8.0 mm in diameter and 8.5 mm in height were fabricated for each ceramic system. For each ceramic system, 10 specimens were tested for fracture strength without fatiguing. A second group (8 specimens) was submitted to a fatigue and fracture test in dry conditions, and a third group (8 specimens) was fatigued and fractured in a wet environment using a mechanical testing machine (Instron). The results were statistically analyzed using a Mann-Whitney test. RESULTS: The results indicated that: (1) The facture strength for In-Ceram was significantly stronger than IPS Empress. No difference was found between In-Ceram and Opc, and Opc and IPS Empress. (2) The strength of the three ceramic systems decreased significantly after fatiguing in both dry and wet environments compared with the nonfatigued specimens. No difference was found between fatiguing in dry and wet environments. (3) For the three systems fatigued in a dry environment and then fracture tested, In-Ceram and Opc were significantly stronger than IPS Empress, but no difference was found between the three systems fatigued in a wet environment. CONCLUSION: Significant differences in the fracture strengths of the different systems investigated may be seen that result from both the nature of the system and the environment in which the specimens were fatigued.

Aluminum Oxide↗