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Biomedical subjects

A K Aydin

Publications and source records attributed to A K Aydin.

15 recordsLinked to original sources
PubMed1999

Bond strength and failure analysis of lining materials to denture resin.

OBJECTIVES: This study was conducted to investigate the bonding properties of five lining materials to a denture base resin. Two hard (chemical-cured resin: Kooliner "Coe Labs, USA" and light-cured VLC resin: Triad "Dentsply, USA") and three soft (chemical-cured resin: Express "Alcos,-USA", heat-temperature vulcanized 'HTV' silicone material: Molloplast-B "Regneri GmbH, Germany" and room-temperature vulcanized 'RTV' silicone material:Ufi Gel-P "Voco, Germany") liners were used. METHODS: Paladent 20 "Heraeus Kulzer GmbH, Germany", a conventional heat-cured polymethylmethacrylate (PMMA), was used as the denture base resin and as the control material. Bonding strength and adhesion properties of the liners to PMMA were compared by tensile test and scanning electron microscope (SEM) analysis. After curing, an aging process was applied and the samples were immersed and stored in distilled water at 37 +/- 1 degrees C and taken out at certain aging intervals (at 0, 15, 30 and 90 days) for examination. Specimens (168) were processed for tensile tests and other specimens (24) for fracture tests. The mean and standard deviation values were calculated. Changes in the mechanical properties and the SEM findings of the adhered surfaces were evaluated. RESULTS: Triad (a hard liner) has the closest tensile strength to the control, indicating the strongest bonding between the base and the liner. Also, during the aging process, formation of better adhesion was observed in SEM micrographs. From the SEM analysis it was found that, Molloplast-B (a soft liner) also has a very good filling capacity. SIGNIFICANCE: Among the hard lining materials, VLC resin to chemical-cured resin; and among the soft lining materials, HTV resin to RTV and chemical-cured ones should be preferred for relining procedures. Molloplast-B and Express as resilient liners were found to have adequate adhesive values for clinical use.

Adhesiveness↗
PubMed1996

Evaluation of the biocompatibility of various dental alloys: Part I--Toxic potentials.

The biocompatibility of a high-gold alloy (Iropal W), two low-gold alloys (Argenco 9 and Gold EWL-G), one palladium alloy (Argipal), two palladium-silver alloys (Argenco 23 and EWL-G), one chrome-nickel alloy (Wiron-88), two chrome-cobalt alloys (Wironium and Wirocast) and a 22 carat gold alloy were evaluated histopathologically with the subcutaneous implantation technique. Cast discs of the materials were implanted for 15, 30 or 60 days in 111 rats. Mildest responses occurred to 22 carat gold alloy. The most vigorous responses were observed in the chrome-nickel alloy samples. The high-gold alloy and the palladium groups showed reactions quite similar to those of the 22 carat gold. However, the low-gold group and the palladium-silver alloys ranked between the basic metal alloy and the precious metal alloy groups.

Animals↗
PubMed1996

Evaluation of the biocompatibility of various dental alloys: Part 2--Allergenical potentials.

The metal alloys which were investigated histopathologically in the first part of this study, were examined with respect to their allergic potentials using the patch test. Results from 60 subjects (aged 17-23) were evaluated following exposure to nickel sulphate, potassium dichromate, silver nitrate, cobalt nitrate, copper sulphate, palladium chloride, platinum chloride and gold chloride. Nickel sulphate produced the most vigorous allergic response whereas gold chloride showed the least of all. The remaining solutions were ranked in decreasing order of severity as follows: potassium dichromate, cobalt nitrate, silver nitrate, copper sulphate, palladium chloride and platinum chloride. Patch testing is indicated in any patient with a history of allergy or sensitivity to a metal. The use of nickel containing alloys in such patients should also be avoided.

Adolescent↗
PubMed1996

Relationship between various functional impression techniques and different operators.

The purpose of the present investigation was to determine the relationship between the reproducibility of soft tissue contours by three different functional impression techniques and four dentists for mandibular distal-extension removable partial dentures. The selected functional impression methods were Lejoyeux, Rouot and McLean techniques. A mucostatic impression technique was used for the control group. To compare and measure the degree of tissue displacement, a three-dimensional coordinate measuring system was used. The differences in vertical displacement of soft tissue among the operators were statistically determined for each impression technique used. Lejoyeux technique produced the least variation in tissue displacement followed respectively by McLean, mucostatic and Rouot methods.

Computing Methodologies↗
PubMed1992

An evaluation of smear layer with various desensitizing agents after tooth preparation.

According to hydrodynamics, any agent blocking the dentinal tubules reduces the flow of fluids and diminishes hypersensitivity. The properties of the desensitizing agents that sponsor tubular occlusion and the barrier efficiency resulting from the interaction of the smear layer with test materials were examined with the scanning electron microscope and energy-dispersive x-ray microanalysis. Selected dentinal desensitizing was accomplished with burnishing procedures, cavity varnish, calcium hydroxide, and topical fluoride. Subjective evaluations were also recorded clinically after tooth preparation. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of the smear plugs. The smear layer and plugs were basically composed of calcium and phosphorus, the major ingredients of dentin.

Adult↗
PubMed1992

Stresses induced by different loadings around weak abutments.

Stresses and deflections of abutments induced by various loadings were analyzed with a two-dimensional finite element model. The biomechanic system consisted of the mandibular posterior three-unit fixed partial denture (FPD). Four different loading types were analyzed: (1) a distributed force of 600 N; (2) concentrated nonaxial and (3) axial 300 N forces at the marginal ridge of the molar; and (4) a concentrated vertical 300 N force at the center of the pontic. All computations were conducted for three different alveolar bone levels. The premolar exerted a greater pressure during occlusal loadings (except axially) on the alveolar bone than the molar. According to the stresses induced in the alveolar bone, the most critical loading was the distributed force. With diminishing periodontal support, stresses elevated in the biomechanic system and critical increases were noted for the concentrated nonaxial load on the molar.

Alveolar Bone Loss↗
PubMed1991

Evaluation of finishing and polishing techniques on surface roughness of chromium-cobalt castings.

The effect of finishing and polishing techniques on surface roughness of a chromium-cobalt alloy was evaluated by means of a stylus profile instrumentation and scanning electron microscopy. Scanning electron micrographs, surface profile tracings, surface roughness recordings, and statistical analysis of data support the finding that the best surface finish is obtained when sandblasting, hard stone, medium abrasive disk, second sandblasting, electropolishing, hard rubber point, hard felt disk with pumice slurry, and felt disk and soft brush with polishing paste are used progressively. The results of this study indicate that the finishing procedure should be carried out in a logical, systematic sequence of steps.

Chromium Alloys↗
PubMed1989

[Torque effect of the forces on the terminal abutment in Kennedy Class II cases].

In this research we have compared the properties of force distribution of some retainers which are used in Kennedy Class II modification 1 cases by using photoelastic stress analysis technique. This research has shown that different retainers vary in their ability to reduce stress to abutments. The results showed that the stressbreaker reduced torque to the abutment teeth induced by the denture and contributed to the preservation of the teeth and their supporting structures. When rigid retainers are used, splinting of the distal abutments on the free-end side and restoring of the abutments on the tooth supported side are usually indicated.

Dental Abutments↗
PubMedDate not supplied

Comparison of deformation by stereophotogrammetry of various kinds of major connectors in maxillary Kennedy Class I removable partial dentures.

PURPOSE: Major connectors must be rigid to perform their functions with maximum efficacy. This study investigated the deformation of four major connectors for maxillary Kennedy Class I removable partial dentures. MATERIALS AND METHODS: The designs were palatal plate, U-shaped plate, palatal strap, and anteroposterior bar. The deformation properties of major connectors were comparatively analyzed by two methods. In the photogrammetric part, a stereometric camera, Avipan-100 glass films, and an analytic apparatus were used. A computerized hydraulic machine was programmed to load the eight test dentures at 4-Hz frequency under a vertical load of 100 kg and a maximum of 300,000 cycles. The fluorescence penetrant liquid inspection test was used to detect the surface microcracks. RESULTS: The anteroposterior bar showed the least deformation. The other connectors, ranked in increasing order for the amount of deformation, were the U-shaped plate, the palatal strap, and the palatal plate. There were no microcracks in the U-shaped plate and the anteroposterior bar designs. CONCLUSION: Anteroposterior bar major connectors showed the least deformation among the maxillary major connector types tested. Microscopic cracks were seen in major connectors showing the highest degree of deformation and located at the depth of the hard palate.

Acrylic Resins↗
PubMedDate not supplied

Wetting properties of saliva substitutes on acrylic resin.

The good wetting of the acrylic resin by saliva substitutes is of clinical importance in xerostomic patients. This study evaluated the wetting properties of different artificial saliva formulations that were mucin-based, carboxymethylcellulose-based, and concentrated ion-based on poly(methyl methacrylate) denture base resin, and compared these properties with natural saliva. The wetting properties of the test materials were examined by contact angle measurements. Ninety-six samples that measured 30 x 30 x 3 mm were examined. The wetting properties of mucin-containing and carboxymethylcellulose-containing substitutes on poly(methyl methacrylate) were significantly better than those of human saliva. Mucin-containing artificial salivas had the best wetting properties on the acrylic resin for the materials tested.

Acrylic Resins↗