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Biomedical subjects

G Eliades

Publications and source records attributed to G Eliades.

49 records · Page 3Linked to original sources
PubMed1991

Porosity of pit and fissure sealants.

The aim of this study was to investigate the bulk porosity of a range of pit and fissure sealants. The following materials were included in the study: Concise White Sealant and Delton (chemically cured); Delton (visible light-cured); Helioseal, Visioseal and Prolite (visible light-cured with delivery from the bottle via cannule); Delton, Luma Seal and Prisma Shield (visible light-cured with syringe-type direct delivery systems). Five cylindrical samples, 7 mm in diameter and 1 mm in thickness, were prepared from each sealant and the following parameters were analysed in a computer-controlled mercury porosimeter: (i) total cumulative pore volume; (ii) specific surface area of pores; (iii) percentage total porosity (iv) bulk density; and (v) pore radius distribution. According to the results, the chemically cured sealants exhibited total cumulative pore volume, specific surface area of pores and total porosity. Significant differences were detected within the group of visible light-cured materials. The visible light-cured sealants with syringe-type delivery exhibited the lowest porosity.

Analysis of Variance↗
PubMed1990

Surface reactions of adhesives on dentin.

The purpose of this study was to characterize changes in the surface chemistry of dentin following various adhesive treatments. The coronal parts of sound freshly extracted third molars were cross-sectioned over the pulp chambers, each producing a pair of dentin samples which were polished to 600 grit and cleaned with 3% H2O2. The first sample of each pair was used as a control, while the second one was subjected to one of the following adhesive treatments: (a) Gluma Cleanser, (b) Tenure Conditioner, (c) Scotchprep, (d) Gluma Cleanser/Gluma Primer, (e) Tenure Conditioner/Tenure Solution A&B, or (f) Scotchprep/Scotchbond 2 Adhesive. The treated samples paired with their respective controls were studied by small-area ESCA spectroscopy. Three areas of 1.0 mm in diameter randomly chosen on each sample were analyzed by survey and C1s, O1s, N1s high-resolution spectra. The samples from groups d, e, and f were additionally subjected to argon-ion-depth profiling of the uppermost 2-nm layer at 0.5-nm intervals. According to the results, treatment modes a, b, and c caused the reduction of carbonates and increased the -NH/NH2 ratio. Treatments a and c increased the alcohol groups, while treatments b and c increased the carbonyl and ether groups. All these changes were in comparison to the reference dentin specimens. Dentin treatment with d, e, and f induced a complex in depth distribution of the C, N, O binding states. The energy shifts detected do not indicate primary bonding of the tested adhesives to the dental substrate.

Adhesives↗
PubMed1990

Etched glass ionomer liners: surface properties and interfacial profile with composite resins.

The purpose of this study was to assess the surface alterations induced by acid etching on two glass ionomer lining cements (Ketac Bond, G-C lining cement) and to evaluate their interface with a composite resin (Herculite XR) following various surface treatments. The changes in the surface composition and topography of the etched liners were studied by electron microprobe and ESCA analyses. The interfacial treatments performed on the ionomer surfaces were: (i) application of a bonding resin; (ii) 20-s acid etching and application of a bonding resin; (iii) application of a dental adhesive based on a chlorophosphate ester of BisGMA (Scotch-bond LC), without acid etching. The interfacial sealing efficiency of these treatments was studied by the silver nitrate microleakage technique combined with optical and electron microscopy. According to the results the etched surfaces of both the liners present excessive porosity with glass and matrix dissolution. Significant changes in the surface chemistry of the liners were detected indicating severe degradation. The microleakage study revealed interfacial gaps and fractures in the etched samples. The best results were obtained from the non-etched ionomer liners which were subjected to the adhesive treatment. The efficiency of acid etching as a necessary step in the 'layered' technique is seriously questioned.

Acid Etching, Dental↗
PubMed1990

[Evaluation of the critical surface tension (gc) of composite resins].

The purpose of this study was to assess the surface free energy of a series of composite resin restorative materials, utilizing the concept of critical surface tension (yc). Cylindrical samples of 20 mm diameter and 2 mm in thickness were prepared from 4 microfilled, 3 hybrid and 6 small particle composite resins. The critical surface tension was determined by contact angle measurements on 1000 grit ground surfaces. A Zisman series of homologous liquids was used (Water, Glycerol, Formamide, Thiodiglycol, Dilodormethane, I-Bromonapthalane). The recorded yc means were 30.000-42.600 dyn/cm for microfilled, 42.47-44.68 dyn/cm for hybrid and 42.19-49.20 dyn/cm for small particle composites. In all the cases the work of wetting was primary attributed to non polar and dispersion forces. The type and the concentration of the reinforcing fillers is the major factor influencing yc, especially in the presence of hydrophylic particles like Ba. Microfilled materials showed decreased wetting efficiency. Hydrophobic monomers do not provide any significant advantage on the wettability of polished composite surfaces.

Composite Resins↗
PubMed1990

[Interfacial strength and microleakage pattern of paired visible light cured composites].

The clinical build up of visible light cured restorations in many cases is performed by layering different types of composites to obtain enhanced characteristics. The purpose of this study was to evaluate the interfacial strength and microleakage pattern of paired light-cured restorations. Two small particle (SP), two pure hybrid (HB) and two microfilled materials (MF) were selected. Cylindrical molds were used to prepare double layer specimens for the groups SP-HB, SP-MF, HB-MF and the controls. The last group was comprised of double layer specimens respectively. All the samples were immersed in normal saline at 37 degrees C and divided in two series. The first series included samples immersed in normal saline for 24 h and accelerated aged for 1 h in saline at 37 degrees C plus 1000 times thermal cycling between 5 degrees-60 degrees C. These samples were sheared off at 0.005 inch/min cross-head speed. The second series was composed of the samples subjected to the some experimental conditions but tested for their interfacial microleakage pattern utilizing the silver nitrate technique. According to the results pairing SP-MF, SP-HB increases interfacial strength compared to MF-MF, and HB-HB. The combination of HB-MF results in no statistical significance from MF-MF or HB-HB. Minimal leakage was detected in some cases but did not correlate to bond strength values.

Composite Resins↗
PubMed1989

[Degree of double conversion in nine pit and fissure sealants].

The purpose of the study was to evaluate quantitatively the degree of double bond conversion in nine commercially available pit and fissure sealants. The materials selected for the study were a) Nuva-Seal and Nuva Coat-UV cured b) Delton, Helioseal, Pentra Seal, Prisma Shield, Visioseal-Visible light cured and c) Delton, Concise White-Chemically cured. Infrared spectroscopy of monomer and polymer films, was used for the quantitative analysis at 37 degrees C. Monomer spectra were obtained from liquid films enclosed between two KBr plates while polymer spectra 24h after storage from 0.2 mm thick cylindrical specimens of 10mm diameter exposed to the activating lights for 1 min or mixed according to manufacturers. The results indicate that UV-cured materials provide the highest degree of double bond conversion followed by visible light cured systems. The clinical failure of UV-cured systems, despite their higher conversion rates is probably attributed to stabilization and shelf life problems of the catalyst besides the harmful side effects of UV-radiation which limited the utilization of these systems.

Light↗
PubMed1988

[Analysis of the oxides and their adherence in precious, high palladium and non precious porcelain dental alloys].

The interfacial oxides formed during the oxidation stage of porcelain dental alloys are of primary importance. The purpose of this study was to identify the type of the oxides in three commercial alloys and to evaluate their adherence with the underlying alloy before and after porcelain application. X-ray diffraction analysis revealed the presence of PdO, Fe2O3, FeO, InO, In2O3 (precious alloy), Ga2O3, GaO, PdO, CuO, SnO2 (Hi-Pd) and NiO, Gr2O3, SiO2, MoO2, TiO2, Al2O3 (non precious) in the oxide layers removed from each alloy respectively with a 10% Br solution in methanol. The highest values of tensile strength were obtained from the non-precious alloy oxides which were further enhanced after porcelain fusion. The application of porcelain does not seem to influence metal ceramic bonding.

Adhesiveness↗
PubMedDate not supplied

[An analysis of the composition and evaluation of Pb impurities of four root canal sealers, Grossman's type, made in Greece].

The properties and the biocompatibility of root canal sealers, depend on the composition and the purity of their constituents. Four root canal sealers made in Greece are claimed to correspond to the formula proposed by Grossman. The lack of quality control on the production of these materials provided evidence for a systemic composition analysis and an evaluation of their Pb impurities. The analytical methods chosen were X-ray diffraction (XRD) and atomic absorption spectroscopy (AAS). According to the results of the study none of the tested root canal sealers agrees with Grossman formula, which was identified in the control sealer. The levels of the Pb were found significantly elevated (80-510 ppm) compared to the control (2 ppm). All these findings indicate the need for the establishment of quality control and the development of strict specifications for the manufacturing of root canal sealers.

Biocompatible Materials↗