1,721,018 research outputs found
ADHESION AND BIOFILM FORMATION BY PERIODONTOPATHOGENIC BACTERIA ON DIFFERENT COMMERCIAL BRACKETS
No full textObjective.
To compare early bacterial adhesion and biofilm formation in vitro by common and uncommon periodontal pathogens on a variety of commercial brackets.
Matherials and Methods
Adhesion and biofilm formation in vitro of 4 bacterial strains on 15 different commercial brackets, in standard culture mediums complemented or not with either serum or human saliva was evaluated by quantitative real time PCR after extraction of bacterial DNA.
Results.
Materials significantly influenced bacterial adhesiveness in a species specific way. Titanium and gold brackets constantly yielded the lowest values with all tested bacteria and in all tested conditions. Bracket materials and medium of growth significantly influenced biofilm formation.
Conclusions.
Materials and environmental conditions significantly influence biofilm formation by periodontal pathogens at the surface of brackets. Whenever possible brackets should be kept far from the gingival margin and if this is not possible, brackets made of gold, titanium, and ceramic should be preferentially used
Role of major glucan associated cell wall proteins of Candida albicans in sensitivity/resistance to antimycotic drugs
No full textIn the last two decades, the opportunistic fungus Candida albicans has been the centre of considerable morbidity and mortality in immunocompromised hosts, such as cancer patients, HIV-infected individuals or transplant recipients. Among Candida virulence factors, cell wall is a plastic and dynamic structure, that · is constantly changing in response to environmental signals. Several evidences demonstrated its role in the host-fungus interactions as well as in the response to antimicrobial drugs. Cell wall is mainly composed of three components interconnected by covalent bonds: B-1-3 and J.3 1-6 glucans, mannoproteins and chitin. The glucans and chitin form a microfibrillar ne~ork, in which several proteins referred to as glucan associated proteins (GAPsi1J are embedded, more or less tightly bound to the polysaccharides. The mayor GAPs are enolase ( 46 kDa), aldolase ( 40 kDa), two isoforms of phosphoglyceromutase (32 and 29kjpa) and two B 1-3 glucanases (44 and 34 kDa). Although most effective anticandidal drugs hchre direct or indirect activities on one or more steps of cell wall construction, it is not clear whether or to what extent the antimycotic efficacy and/or the emergence of drug resistance may involve modifications of cell wall GAP composition. Our studies have demonstrated that when different Candida strains were grown in the presence of effective antimycotic drugs, a substantial decrease in the expression of three enzymes of the glycolytic pathway ( enolase, aldolase and phosphoglyceromutase) occurred, which were apparently replaced by enhancement of the exoglucanase constituents (34 and 44 kDa). These changes were not found when the fungus was made resistant to the drugs and surprisingly, the drug-resistant strains were significantly more pathogenic than parent strains in a mouse systemic candidiasis model. [2J To further characterize the modification in GAP composition, the rate of cell wall mannosilation was studied by using fluorescent ConA as a marker of mannosilated residues in Candida strains èxposed to the drugs. Microscopie analysis showed a substantial increase in the fluorescent signals localized in the cell wall of sensitive-drugs treated cells. Since some exoglucanase constituents are mannosilated, these observations confirm the drug-induced increased expression of 34 kDa protein described above. Moreover, electron-microscopie analysis showed a strong modification in cell wall morphology in cells exposed to ef(ective doses of the drugs,'~rther suggesting that this cellular structure plays a key role in antimycotic response. In order to verify whether a stress mechanism was involved in the drug-induced modification of GAP composition, we tested intracellular levels of glutathi9ne (GSH) as a marker of redox .state in sensitive and resistant strains. We found that in s'ensitive cells GSH levels was significantly decreased in response to effective doses of antifungal drugs. On the contrary, in resistant cells GSH content was not modified also in the presence of drugs at high doses. The results clearly indicate that Candida response to antimicrobic drugs is related to specific alterations of GAP composition in cell wall. Detailed knowledge of these alterations and identification of the related mechanisms of induction could consti tute an useful tool to identify new therapeutic strategies for the cure of locai and systemic candidiasis
Use of a tetragonal structure composed of yttrium-stabilized zirconium oxide in dentistry: a study of the ceramic-zirconia interface.
No full textObjective
The introduction of yttrium-stabilized zirconia (Y-TZP) has opened new frontiers in the fields of dental-material esthetics and biocompatibility. In a previous report, we analyzed the capacity of Y-TZP to withstand maximum loading (static resistance) and the repeated application of loads lesser than those that provoke fracture (fatigue resistance). The aim of this study was to evaluate the adhesion between Y-TZP and its ceramic support (shear resistance).
Materials and methods
To assess this characteristic, we developed a new testing protocol to be used with specially designed cylindrical samples with ceramic covering on a zirconia base. The research was carried out in two phases: the aim of the first was to identify the approach that produced the best adhesion; the second phase aimed at identifying the mechanical and/or physical mechanisms responsible for the zirconia/ceramic adhesion.
Results
In the first phase, we found that the surface finish of the zirconia was the sole factor that influenced final adhesion. In the second phase, our findings showed that this adhesion is essentially due to micromechanical and physical interactions, which were not dependent on the contact pressure between the two materials or on the geometric characteristics of the ceramic covering.
Conclusions
On the whole, the best final result was obtained when the zirconia was subjected to surface finishing with a diamond rotary instrument, but even in this case adhesion was inferior to that achieved with a gold-alloy base
ADHESION AND BIOFILM FORMATION BY ORAL STREPTOCOCCI ON DIFFERENT COMMERCIAL BRACKETS
No full textObjective.
To compare early bacterial adhesion and biofilm formation in vitro by different oral streptococci on a variety of commercial brackets
Materials and Methods.
Adhesion and biofilm formation in vitro of 6 Streptococcus spp. on 15 different commercial brackets, in standard culture medium and in human saliva was evaluated by the MTT reduction assay.
Results.
Significant differences were evidenced in both early adhesion and biofilm formation among the studied brackets and between the two conditions of growth. Gold brackets resulted less prone to colonization, while composites brackets were the most prone ones. The rates of growth of the different tested species on the different tested materials were significantly different.
Conclusions.
The adopted experimental plan, dissecting the two phases of plaque formation on different brackets in different conditions, showed that composite brackets are more susceptible to adhesion and colonization by streptococci, while the remaining tested brackets do not show differences that could be clinically relevant. Data suggest that different personal behaviors affecting the oral environment could significantly affect colonization of brackets by cariogenic bacteria
Preparation and characterization of antimicrobial wound dressing based on silver, gellan, PVA and borax
No full textAttività di inibitori sintetici di istone deacetilasi sull'acquisizione di resistenza agli azolici in Candida albicans
No full text- …
