Pertti Viitaniemi

The effect of heat treatment of wood on osteoconductivity.

Wood is a natural porous fibre composite, which has some structural similarities to bone. Recently, it has been used as a modelling material in developing synthetic fibre-reinforced composite to be used as load-bearing non-metallic artificial bone material. In this study, the behaviour of wood implanted into bone was studied in vivo in the femur bone of the rabbit. Wood was pre-treated by heat, which altered its chemical composition and structure, as well as the biomechanical properties. In the heat treatment, woods dimensional stability is enhanced, equilibrium moisture content reduces and the biological durability increases. Cone-shaped implants were manufactured from heat-treated (at 200 and 140 degrees C) birch wood (Betula pubescens) and from untreated birch. A total of 62 implants were placed in the distal femur of 50 white New Zealand rabbits. The behaviour of the implants was studied at 4, 8 and 20 weeks with histological and histometrical analysis. Osteoconductive contact line and the presence of fibrous tissue and foreign body reaction were determined. The amount of fibrous tissue diminished with time, and the absence of foreign body reaction was found to be in correlation to the amount of heat treatment. Histologically found contact between the implant and the host bone at the interface was significantly more abundant in the 200 degrees C group (avg. 12.8%) vs. the 140 degrees C (avg. 2.7%) and the untreated groups (avg. 0.6%). It was observed that the heat treatment significantly modified the biological behaviour of the implanted wood. The changes of the wood by heat treatment showed a positive outcome concerning osteoconductivity of the material.

Pine heartwood and glass surfaces: easy method to test the fate of bacterial contamination

The survival of two bacteria, Escherichia coli and Listeria monocytogenes was observed on pine heartwood and glass surfaces by using a simple test method. The development of the number of bacterial cells was evaluated by titration after vortexing the samples in BHI broth and culturing the resulting broth on agar plates. The bacterial count decreased clearly faster on pine heartwood than on glass surfaces. This result was confirmed by studying the wooden samples also one day after to exclude possible adherence of the bacterial cells on the porous surface. This study confirms the results of several other studies that suggest wood to have antibacterial properties.ZusammenfassungDas Überleben von zwei Bakterienarten, Escherichia coli und Listeria monocytogenes, auf Kiefernkernholz und Glasoberflächen wurde mit einer einfachen Prüfmethode untersucht. Mittels Titrierung wurde die Entwicklung der Anzahl der Bakterienzellen untersucht, nachdem die Proben in einer BHI-Nährlösung gevortext wurden, die anschließend auf Agarplatten kultiviert wurde. Die Keimzahl nahm auf Kiefernkernholz deutlich schneller ab als auf Glasoberflächen.Dieses Ergebnis konnte auch durch Untersuchungen der Holzproben am darauf folgenden Tag bestätigt werden, um ein mögliches Anhaften der Bakterienzellen auf der porösen Oberfläche auszuschließen. Mit dieser Studie konnten die Ergebnisse früherer Untersuchungen bestätigt werden, die Holz antibakterielle Eigenschaften zuschreiben.