Biomedical subjects

Yuriy Nekrashevych

Publications and source records attributed to Yuriy Nekrashevych.

5 recordsLinked to original sources

PubMed2004

Protective effect of the in situ formed short-term salivary pellicle.

Salivary pellicle, as previously investigated, protects the enamel surface after certain processes of maturation against the influence of acidic agents. The aim of the present study was to investigate the protective effect of the short-term salivary pellicle formed in situ over periods of 3, 60 and 120 min. Six human volunteers used intraoral acrylic splints with bovine enamel samples fixed at the buccal and palatal sites of the maxillary first molars and second premolars. Enamel specimens (n = 252) with and without pellicle were immersed for 60 s in 1.0% citric acid solution under agitation. Knoop surface hardness (KHN) of uneroded polished enamel was measured as a baseline and estimated immediately after erosive treatment reflecting the microhardness loss (DeltaKHN). The amounts of calcium dissolved from the eroded enamel surface were analysed by atomic absorption spectroscopy and scored in mg/l per 10 mm2 of enamel surface area. In addition, the scanning electron microscope was used for the micromorphological examination of the erosive alterations of the enamel surface. The average microhardness loss values after erosion of the enamel samples with buccally/palatally formed pellicle layers were measured as 139.1/144.9 DeltaKHN for 3 min pellicle, 145.9/146.9 DeltaKHN for 60 min pellicle and 141.7/138.6 DeltaKHN for 120 min pellicle. Calcium release values from the specimens with buccal/palatal pellicles were amounted to 15.0/14.9, 16.5/15.9 and 15.3/17.4 mg/l per 10 mm2 for 3, 60 and 120 min-old pellicles, respectively. No significant differences were related to the pellicle formation time and intraoral site (buccal or palatal) in all tested series (ANOVA, P < 0.05). However, significant protection of the enamel surface provided by the pellicle layer was observed on all pellicle-covered surfaces if compared to the non-covered enamel samples (calcium release: 25.6 mg/l per 10 mm2; microhardness loss 187.0 DeltaKHN). These data were in accordance with the morphologic alterations caused by citric acid on the pellicle-covered and pellicle non-covered specimens. It could be concluded that salivary pellicle formed in situ within a period of 3 min offers protection of enamel against citric acid. However, pellicle does not completely inhibit the erosive action of citric acid under the conditions of the present study.

Adult↗

PubMed2004

Supramolecular pellicle precursors.

Saliva contacting with solid surfaces in the oral cavity forms a coat termed the pellicle. However, its formation is not fully understood. Although indications for the existence of supramolecular pellicle precursors have been reported, the possible relationship between them and pellicle formation is unclear. This study investigates the ability of supramolecular precursors to form the pellicle via interaction with a solid surface. Fixed and unfixed salivary globes were spread onto a microscopic grid and examined by transmission electron microscopy. Biochemical pretreatment of saliva revealed that neither disulphide links nor transglutaminase-mediated crosslinking are responsible for maintaining the salivary globes, i.e. supramolecular pellicle precursors. However, the detergent, sodium dodecyl sulphate, caused dissociation of the salivary globes, indicating their micellar nature. Saliva contacting a formvar film for 10 s did not form a complete surface coating, but single supramolecular pellicle precursors were observed attached to the surface. After extension of the contact time to 60 s, a surface layer was formed by clustering and fusion of the supramolecular pellicle precursors. The supramolecular pellicle precursors are unstable and attain a thermodynamically more favourable state by adhesion to a solid surface. As a result, a layer of fused precursors covering the solid surface is formed -- the salivary pellicle.

Dental Pellicle↗

PubMed2004

Electron microscopic detection of salivary alpha-amylase in the pellicle formed in situ.

Immunological and biochemical analyses have shown that alpha-amylase is an essential component of the acquired pellicle. After adsorption, this enzyme might act as a receptor for bacterial adherence. However, data indicating that amylase is bound to the pellicle surface in vivo and thus available for adhering bacteria are rare. Therefore, the present study focused on alpha-amylase within the pellicle formed in situ, using gold-immunolabeling electron microscopic techniques. Pellicles were formed by intra-oral exposure of enamel specimens for 30 and 120 min in six subjects. The results obtained by transmission electron microscopy indicate that amylase was randomly distributed in the pellicle layer without any preferential localization within the pellicle. Thus, salivary alpha-amylase might be considered as an important structural component that is even involved in the early stages of pellicle formation. The findings of field emission in-lens scanning electron microscopy provided evidence that the enzyme is located on the pellicle surface. It could be concluded that alpha-amylase might act as a receptor for bacterial adherence to the pellicle in vivo.

Adsorption↗

PubMed2004

Assessment of enamel erosion and protective effect of salivary pellicle by surface roughness analysis and scanning electron microscopy.

PURPOSE: To assess dental erosion caused by 0.1% and 1.0% citric acid in vitro and to estimate the protective influence of experimentally formed salivary pellicle. MATERIALS AND METHODS: Bovine enamel slabs (n = 80) were polished and embedded in epoxy resin. For the formation of pellicle layer 40 specimens were immersed for 24 h in pooled human saliva. Erosion was caused by immersion in citric acid solution for 1, 5, 10 and 30 min. Erosive alterations on the pellicle-covered and non-covered enamel specimens were scored as a change (delta) of surface roughness parameters Ra, Rt and RzDIN using contact profilometer and observed in scanning electron microscope. RESULTS: Profilometric analysis of eroded enamel specimens emphasized the aggressiveness of even low concentrated citric acid with a short period of challenge. The change of roughness parameters after 1-min immersion in 0.1% citric acid were 16.4, 182.6 and 132.2 nm for deltaRa, deltaRt and deltaRzDIN, respectively, and 54.8, 516.6 and 258.2 nm after 1-min immersion in 1.0% citric acid. Changes of the surface roughness were dependent on the exposure time and concentration of acidic solution. Pellicle layer significantly reduced the extent of erosive destruction, which was additionally documented on SEM-micrographs. Residual pellicle-like structures were detected after 5 min of immersion in 0.1% citric acid. However, there were no significant differences in pellicle-covered and non-covered enamel slabs measured profilometrically for 1.0% citric acid with 10 min and 30 min exposure time. CONCLUSION: The findings confirm the property of pellicle layer to resist against erosive influence of organic acids, which is, however, limited by duration of acidic treatment and concentration of erosive agent.

Animals↗

PubMedDate not supplied

Protective influence of experimentally formed salivary pellicle on enamel erosion. An in vitro study.

The purpose of this study was to evaluate dental erosion in 0.1 and 1.0% citric acid in vitro by several different methods and to assess the protective potential of experimentally formed salivary pellicle (24 h in vitro). Bovine enamel slabs were embedded in epoxy resin and polished. Erosion was performed in citric acid for 1, 5 or 10 min and recorded as microhardness loss, as changes of surface roughness (R(a), R(t) and R(zDIN)) and as calcium release. Additionally, erosive alterations were observed with scanning electron microscopy. Significant microhardness loss on non-pellicle-covered specimens was measured after 1-min exposure to 0.1% citric acid. Microhardness loss was time- and concentration-dependent. Salivary pellicle significantly inhibited both microhardness loss, except after 10-min immersion in 1.0% citric acid, and significantly reduced the increase of surface roughness. There were, however, no significant differences in calcium release between pellicle-covered and non-covered enamel. The results support the general conclusion that salivary pellicle effectively protects enamel surface against short-term erosion in organic acids.

Analysis of Variance↗