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Wettability, water sorption and water solubility of seven silicone elastomers used for maxillofacial prostheses
Umeå University, Faculty of Medicine, Department of Odontology, Dental Technology/Dental Materials Science.
Umeå University, Faculty of Medicine, Department of Odontology, Dental Technology/Dental Materials Science.
2008 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 19, no 1, 225-231 p.Article in journal (Refereed) Published
Abstract [en]

The wettability, water sorption and solubility of silicone elastomers used for maxillofacial prostheses were studied. The hypothesis was, that a material that has absorbed water would show an increase in the wettability and thus also the surface free energy of the material.

Seven silicone elastomers, both addition- and condensation type polymers, were included. Five specimens of each material were subjected to treatment according to ISO standards 1567:1999 and 10477: 2004 for water sorption and solubility. The volumes of the specimens were measured according to Archimedes principle. The contact angle was measured with a contact angle goniometer at various stages of the sorption/solubility test.

Wettability changed over the test period, but not according to theory. The addition type silicones showed little or no sorption and solubility, but two of the condensation type polymers tested had a significant sorption and solubility. This study showed that condensation type polymers may show too large volumetric changes when exposed to fluids, and therefore should no longer be used in prosthetic devices. The results of this study also suggests that it might be of interest to test sorption and solubility of materials that are to be implanted, since most of the materials had some solubility.

Place, publisher, year, edition, pages
2008. Vol. 19, no 1, 225-231 p.
National Category
Dentistry
Identifiers
URN: urn:nbn:se:umu:diva-10958PubMedID: 17597370OAI: oai:DiVA.org:umu-10958DiVA: diva2:150629
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Silicone obturators and the bacterial flora in symptomatic nasal septal perforations
Open this publication in new window or tab >>Silicone obturators and the bacterial flora in symptomatic nasal septal perforations
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background A perforation in the nasal septum can cause symptoms such as bleeding, obstruction, crusts and pain, and can be a challenge to treat. Surgery is the treatment of choice, but disease, size of the perforation, or the patient’s wish may contradict surgery. A custom-made silicone obturator is a successful treatment option, but little is known how this treatment affects the microbial flora. The purposes of this thesis were (i) to investigate the microbial flora around symptomatic nasal septal perforations before treatment, (ii) during and after a 12-month treatment period with a custom-made obturator, (iii) to compare the microbial flora around symptomatic perforations with the flora from the same area of the septum in healthy individuals, (iv) to investigate the microbial colonization of the silicone obturator, and (v) also to investigate the water sorption, solubility and if the wettability of silicones are affected by water. The hypotheses were (i) that the bacterial flora around symptomatic perforations would not differ from that found in healthy individuals, apart from a possible presence of Helicobacter pylori; (ii) the bacterial flora would change in composition during the course of treatment and that microorganisms and proteins could be seen on the surface of the silicone obturators; (iii) a material that has adsorbed water would also show an increase in wettability and the surface free energy of the material.

 Methods Twenty-seven patients and 101 healthy individuals volunteered. Swabs were made around the rim of the perforation, or on the septum in the locus Kisselbachi area in the healthy individuals. Bacteria and fungi were isolated and identified with standard laboratory techniques. A biopsy of the granulated tissue at the perforation was taken and cultivated for Helicobacter pylori. Swabs were also taken three, six and twelve months after inserting the obturator. The obturator was analysed after being used twelve months in the nose.  Seven silicones were tested for water sorption and solubility according to ISO standards 1567:1999 and ISO 10477:2004. The change in wettability was examined by measuring the contact angle with a contact goniometer at various stages of the sorption/solubility test.

Results Staphylococcus aureus was present in 88% of the untreated patients. With treatment a significant reduction of S. aureus occurred to 54.5% (p<0.05). In the healthy group S. aureus was present in 13% of the subjects. No Helicobacter pylori could be cultivated from the biopsies taken of the granulated tissue at the perforation. The flora round the untreated perforation was dominated by S. aureus with few other bacterial species detected. In the healthy group there was a diversified flora with both aerobic and anaerobic bacteria. SEM revealed a rough surface on the silicone obturator and crazing of the silicone surrounding the pigment granules. Both bacteria and proteins could be seen on the obturators in SEM. Candida albicans was detected in one obturator, but not in the mucosal swab at the corresponding time. That patient had, however, been treated for Candida in the nose six months prior to the last visit in the study. Wettability was affected but did not increase with amount of adsorbed water. Some materials showed an increase and some a decrease in the surface-free energy. The tested addition silicones showed little sorption and solubility.

Conclusions The patients with symptomatic perforations of the nasal septum had a bacterial flora totally dominated by S. aureus. The massive presence of S. aureus around symptomatic perforations may have an impact on the persistence of the granulated and inflamed tissue present in symptomatic perforations, thus forming a vicious circle with bleeding and crustation.

S. aureus dominance in the mucosa surrounding symptomatic perforations was diminished by using a custom-made obturator. The microbial flora became more diversified with the treatment, although not resembling the flora in healthy individuals. The microbial flora of the obturators was similar, but not the same as the corresponding mucosal flora. The discovery of Candida in the obturator of a patient who had been treated for Candida in the nose six months earlier suggests that obturators need to be exchanged when fungal infections are being treated to prevent the fungus from re-infecting the patient at a later stage.

The silicone had a rough surface and a poor wettability, both aspects favours colonization of microorganisms. The silicone was negatively affected by the colouring pigments, this should be considered when colouring is not necessary. The slight, but existing solubility of silicones emphasises the importance of using medical grade silicones that are more purified than industrial silicones. 

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2012. 36 p.
Series
Umeå University odontological dissertations, ISSN 0345-7532 ; 124
Keyword
Nasal mucosa, perforation, symptomatic, inflammation, Staphylococcus aureus, obturator treatment, medical silicone, wettability
National Category
Dentistry
Identifiers
urn:nbn:se:umu:diva-60831 (URN)978-91-7459-494-2 (ISBN)
Public defence
2012-11-23, Biomedicinhuset, sal E04, byggnad 6E, Norrlands universitetssjukhus, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2012-10-31 Created: 2012-10-30 Last updated: 2012-11-08Bibliographically approved

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