Márta Radnai

Surface modifications induced by ns and sub-ps excimer laser pulses on titanium implant material.

Medical implants used in oral and orthopaedic surgery are mainly produced from titanium. Their biological behaviour, e.g. osseointegration, essentially depends on both the chemical composition and the morphology of the surface. Modifications achieved by excimer laser irradiation of titanium samples were investigated in order to improve their surface characteristics so as to facilitate biointegration. To enlarge the effective interfacial area of bone-implant contact, holes were ablated by laser pulses of ns or sub-ps length. During ns ablation, crown-like projecting rims formed around the borders of the holes. Ultra-short (0.5ps) KrF excimer laser pulses were successfully applied to avoid these undesirable formations. Since a smooth dental implant surface is necessary to maintain a healthy connection with the soft tissues, laser polishing of samples was investigated, too. Irradiation with a series of ns laser pulses resulted in effective smoothing, as measured with atomic force microscope. X-ray photoelectron spectroscopy analysis of the laser-polished titanium surface revealed that laser treatment led to a decrease of the surface contamination and in thickening of the oxide layer. X-ray diffraction measurements demonstrated that the original alpha-titanium crystal structure was preserved.

Benefits of Periodontal Therapy When Preterm Birth Threatens

There is growing evidence that chronic periodontitis may be a risk factor for pre-term birth. The goal of this intervention study was to determine the effect of periodontal treatment on the pregnancy outcome in women with threatening pre-term birth and initial localized chronic periodontitis. Forty-one women with a singleton pregnancy were enrolled in the study. For this treatment group, oral hygiene instruction and periodontal therapy were provided in the third trimester, while those in the control group (42 persons) did not receive any periodontal treatment. In the treatment group, the mean weight of newborns was 3079.0 g, compared with the control group mean of 2602.4 g. The incidence of pre-term birth and low birthweight in the treatment group was significantly less than in the control group (p = 0.015). Periodontal treatment completed before the 35th week appeared to have a beneficial effect on birth weight and time of delivery.

Effects on titanium implant surfaces of chemical agents used for the treatment of peri-implantitis

The treatment of peri-implantitis, which causes tissue deterioration surrounding osseointegrated implants, involves surface decontamination and cleaning. However, chemical cleaning agents may alter the structure of implant surfaces. We investigated three such cleaning solutions. Commercially pure (grade 4) machined titanium discs (CAMLOG Biotechnologies AG, Switzerland) were treated with 3% H(2)O(2) (5 min), saturated citric acid (pH = 1) (1 min) or chlorhexidine gel (5 min), and their surface properties were examined by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Human epithelial cell attachment (24-h observation) and proliferation (72-h observation) were investigated via dimethylthiazolyl-diphenyltetrazolium bromide (MTT) and bicinchoninic acid (BCA) protein content assays. AFM revealed no significant difference in roughness of the three treated surfaces. XPS confirmed the constant presence of typical surface elements and an intact TiO(2) layer on each surface. The XPS peaks after chlorhexidine gel treatment demonstrated C-O and/or C=O bond formation, due to chlorhexidine digluconate infiltrating the surface. MTT and BCA assays indicated similar epithelial cell attachments in the three groups; epithelial cell proliferation being significantly higher after H(2)O(2) than after chlorhexidine gel treatment (not shown by BCA assays). These agents do not harm the Ti surface. Cleaning with H(2)O(2) slightly enhances human epithelial cell growth, in contrast to chlorhexidine gel.

Corrosive effects of fluoride on titanium: Investigation by X-ray photoelectron spectroscopy, atomic force microscopy, and human epithelial cell culturing

High fluoride (F(-)) concentrations and acidic pH impair the corrosion resistance of titanium (Ti). Effects of F(-)-containing caries-preventive prophylactic rinses, and gels on Ti were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Human epithelial cell attachment and proliferation were investigated by dimethylthiazol-diphenyl tetrazolium bromide (MTT) and protein content assays. Aqueous 1% NaF solution (3800 ppm F(-), pH 4.5) or high (12,500 ppm) F(-) content gel (pH 4.8) strongly corroded the surface and modified its composition. XPS revealed formation of a strongly bound F(-)-containing complex (Na(2)TiF(6)). AFM indicated an increase in roughness (R(a)) of the surfaces: 10-fold for the NaF solution and smaller for the gel or a mouthwash (250 ppm F(-), pH 4.4). MTT revealed that cell attachment was significantly increased by the gel, but was not disturbed by either the mouthwash or the NaF. Cell proliferation determined by MTT decreased significantly only for the NaF-treated samples; protein content assay experiments showed no such effect. This study indicates that epithelial cell culturing results can depend on the method used, and the adverse effects of a high F(-) concentration and low pH should be considered when prophylactic gels are applied by patients with Ti implants or other dental devices.

Detection of periodontopathogenic bacteria in pregnant women by traditional anaerobic culture method and by a commercial molecular genetic method.

To culture facultative and strict anaerobic bacteria is a well-established method for analyzing subgingival plaque samples. Micro-IDent and micro-IDent Plus (HAIN Lifescience GmbH, Nehren, Germany) tests are two commercially available rapid PCR-based methods for the identification and quantification of putative periodontopathogen bacteria. In this study, we compared these commercial PCR-based hybridization methods with conventional anaerobic culture technique. A total of 36 subgingival plaque samples were collected from periodontal pockets of pregnant women with chronic localized periodontitis. Aliquots of these samples were evaluated with species-specific probes provided by micro-IDent and micro-IDent Plus tests simultaneously, and from the same samples anaerobic and capnophylic bacteria were cultured on selective media. The overall agreement between both methods was excellent for Eubacterium nodatum, Tannerella forsythia and Porphyromonas gingivalis (97-92%), fair for Capnocytophaga sp, Eikenella corrodens, Actinobacillus actinomycetemcomitans, and Prevotella intermedia (91-89%) and poor for Fusobacterium nucleatum, Parvimonas micra (Micromonas micros), and Campylobacter rectus (86-78%). Discrepancies in the results may be explained by inability of culture method to distinguish between closely related taxa (e.i P. intermedia/Prevotella. nigrescens), and problems of keeping periodontopathogen bacteria viable, which is required for successful detection by standard culture method. Nucleic acid-based methods may replace cultivation method as frequently used methods in microbiological diagnosis of progressive periodontitis, thus micro-IDent and micro-IDent Plus tests can be recommended where culture of periodontopathogenic bacteria is not performed in routine microbiology laboratories to analyze subgingival plaque samples.

Effect of antifungal gels incorporated into a tissue conditioning material on the growth of Candida albicans.

OBJECTIVE The aim of this study was to examine the effectiveness of antifungal gels incorporated into a tissue conditioner which inhibits the growth of Candida albicans in vitro. BACKGROUND The release of drugs from relining materials has been demonstrated earlier. However, the incorporation of antifungal agents in gel form has not yet been studied. MATERIALS AND METHODS Visco-gel(®) tissue conditioner was prepared with chlorhexidine digluconate and miconazole in gel form in a concentration of 5, 10, 15, 20 and 25% by volume. Sample discs were prepared and placed on Sabouraud Dextrose Agar (SDA) plates which had been previously inoculated with C. albicans, and incubated aerobically at 37 °C. To investigate antifungal activity over time, Visco-gel discs containing 20%v/v miconazole were prepared and immersed in water for different time periods before being placed on SDA plates inoculated with C. albicans. RESULTS Chlorhexidine digluconate gel added to tissue conditioner had no inhibition effect on the growth of C. albicans. Incorporation of miconazole gave a dose-related inhibitory effect on candidal growth. Immersion of the discs in water showed an inverse relationship between time of immersion and degree of inhibition. CONCLUSION Miconazole added in gel form to Visco-gel(®) had an inhibitory effect on the growth of C. albicans in vitro.

Staff recruitment, development and global mobility

This paper considers issues that relate to staff recruitment, staff development and global mobility of dental academics. Published literature, which has a North American bias, is reviewed. Recommendations, which may be applicable world-wide, are made to address evident and pertinent areas of concern in terms of the availability of quality dental teaching staff in dental teaching institutions so as to sustain the global dental academic enterprise at appropriately high levels of achievement.

Prevention of preterm delivery with periodontal treatment

Objective: To demonstrate the role of periodontal treatment (PT) in the prevention of preterm delivery (PD). Methods: A comparative prospective study of two groups of pregnant women with threatening PD was carried out at the Department of Obstetrics and Gynaecology of the University of Szeged: group A (n = 39) comprised patients who were merely examined dentally for periodontitis, and group B (n = 44) consisted of patients who received periodontal treatment during pregnancy. Results: Periodontitis was identified in 19 cases (48.7%) in group A and in 18 cases (40.9%) in group B. The mean birth weight of the newborns was significantly higher in group B (3,009.1 g) than in group A (2,580.8 g; p = 0.007). The rate of premature birth was significantly lower in the group who received PT (p = 0.012, odds ratio = 3.5, 95% confidence interval = 1.38–8.86). Conclusions: The PT of pregnant women can decrease the rate of premature birth and consequently lead to a better neonatal health outcome.

Proposed requirements for a European doctorate in dentistry: a discussion document prepared by a special interest group under the auspices of the Association for Dental Education in Europe

In the Bologna process a third cycle is distinguished at the doctoral level. In documents on the Bologna process it is advocated to harmonise the structure and requirements of the doctorate, which in Europe are characterised by a wide variety. Differences exist in all possible requirements between countries, and even between schools within one country differences can be seen. In this paper an inventory is made of these differences in the dental doctorate between European countries. Moreover, the need for necessary harmonisation of requirements for a European dental doctorate is strongly advocated and a proposal is presented.

Effect of caries preventive products on the growth of bacterial biofilm on titanium surface.

Fluorides may affect the oxide layer on titanium surface. Caries preventive mouthwashes or gels contain fluorides and are applied at low pH. The aim of the present work was to study whether various concentrations of fluoride at acidic pH cause changes in the surface structure on the polished region of Ti implants, and alter the adherence and colonization of bacteria. Commercially pure Ti grade 4 discs with a polished surface were treated with a mouthwash containing 0.025% fluoride, a gel containing 1.25% fluoride or a 1% aqueous solution of NaF (pH 4.5). The change of surface roughness of the samples and the colonization of Porphyromonas gingivalis strains were studied by scanning electron microscopy after 5 days of anaerobic incubation. The quantity of the bacterial protein was determined by protein assay analysis. Agents with high fluoride concentration at acidic pH increased the roughness of the Ti surface. A slight increase in the amount of bacteria was found on the surfaces treated with 1% NaF and gel in comparison with the control surface. This study suggested that a high fluoride concentration at acidic pH may hinder the development of a healthy transgingival epithelial junction on Ti implants, due to bacterial colonization.