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Biomedical subjects

A Patyk

Publications and source records attributed to A Patyk.

11 recordsLinked to original sources
PubMed2005

[Influence of different mixing fluids on mechanical and micromorphological in vitro qualities of hydroxyapatite cement].

AIM: In reconstructive craniofacial surgery a new synthetic hydroxyapatite cement has been used in the last few years. Tetra- and dicalcium phosphates react with either slow setting aqua bidest. or with faster setting sodium monophosphate solution to hydroxyapatite. The aim of this study was to investigate the two mixing fluids of hydroxyapatite for resulting micromorphology, pressure strength, and interactions with fibroblasts. MATERIAL AND METHODS: Pressure strength tests of hydroxyapatite cement test samples (n=80) were performed after a setting time of 3 and 24 h. The micromorphology of surfaces of the resulting particles was assessed under an electron microscope. In cell cultures L-929 and HEp2 cells were incubated with test samples and cell growth was assessed by light and electron microscopy. RESULTS: The test samples mixed with sodium monophosphate solution showed statistically significantly higher values of pressure strength. The resulting pressure strength depended on respective mixing fluids, setting time, and pressure of application. In general, test samples mixed with sodium monophosphate solution showed a more load-stable, homogeneous anorganic matrix whereas test samples mixed with aqua bidest. had a porous microarchitecture which was more fragile. In cell culture the porous structure showed disintegration in cell culture medium. CONCLUSION: To what extent the two mixing liquids of hydroxyapatite cement influence the resorption and bony substitution has to be shown in further studies.

Animals↗
PubMed2003

[Memory effect of resorbable polymers].

BACKGROUND: The present study analyzed the memory effect of resorbable polymers. Depending on temperature, this effect describes the ability of different materials to "remember" their original form after mechanical deformation. Resorbable polymers serve as materials to stabilize and fix bone fractures. Compared to metal transplants, resorbable polymers are able to undergo thermoplastic deformation. The precise adaptation of the transplant to the surrounding bone guarantees an exact anatomical reconstruction. However, during normal applications, it was observed that these biodegradable plastic materials tend to revert to their original form at body temperature. This "memory effect" could result in negative consequences for the medical treatment. METHODS: By the process of compression molding, geometrically formed specimens (lattice, rod, plate) consisting of different polyglycolides and polylactides were prepared. After warming up the specimens to 50 degrees C (water bath) they were deformed into definite angles. Following this procedure, the specimens were put in a water bath at 37 degrees C to mimic the adaptation of the transplant at body temperature. The retroflexion of the material (memory effect) was measured using an XY-measuring desk. RESULTS: The present study clearly reveals that highly deformed specimens react with stronger retroflexions. In addition, the results indicate that the memory effect depends on geometrical design as well as on chemical composition. All tested polymers showed a strong initial memory effect that decreased with time.

Absorbable Implants↗
PubMed1998

Study on the surface of resins that burn without residues in the lost-wax procedure.

STATEMENT OF PROBLEM: When compared with waxes and prefabricated components made of dental alloys, processing resins is difficult and often results in a less accurate fit. The exact linear dimension is hard to realize, as the materials required for a dental casting are adjusted to dental waxes, and usually there are no special processing instructions for these resins. PURPOSE: The surface structure of 16 residue-free burning resins was determined to find which could enlarge the range of application for waxes in the dental casting technique. MATERIAL AND METHODS: A total of 480 specimens (30 castings for each of 16 resins) were marked with an individually cut pyramid, which left an impression in the resin. This was distinctly visible in the metal after casting in "the lost form." The surfaces of these 480 specimens were measured in three dimensions with a positioning aid "before casting in resin" and "after casting in metal" by the Perthometer micrometer. All specimens were treated identically by the lost-wax process by using the rotation symmetry of the muffle. The differences in the surface data before casting in resin and after casting in metal characterize the quality of the particular resin. RESULTS: Surface roughness differed between the 16 resins in the range of micrometer. CONCLUSIONS: With the dental casting technique, it is recommended that some resins replace waxes or wax-resin compositions.

Dental Alloys↗
PubMed1991

[Contribution of vibration supported cementation on reconstructions].

A laboratory study was undertaken to investigate the influence of different types of cement and cementation techniques on the enlargement of the marginal gap of crowns. The crowns and preparations in the study were standardized; preparation forms were shoulder, chamfer and shoulderless. The cement brands were Harvard, Durelon and AquaCem. The enlargement of the marginal gap was measured for two different cementation methods: 1. Crowns were manually seated onto metal dies and subsequently loaded with 50 N constantly for 10 minutes 2. Crowns were manually seated on the dies and exposed to mechanical vibration from a Bergendal amalgam-condenser, subsequently loaded with 50 N constantly for 10 minutes. The comparison of both methods showed a 12-31% smaller vertical cementation gap enlargement of the samples that were treated with vibration. We recommend the clinical use of this method. Best results were achieved with AquaCem; Harvard showed the greatest difference when changing between the methods.

Crowns↗
PubMed1990

[Economic aspects of use of alternative dental alloys].

A cost calculation for different types of dental alloys was carried through all stages of production. Recycling and scrap material values were included. Results showed that over an estimated 20 years of usage, the higher annual cost for bridges cast with a high gold alloy in relation to those with lower gold content alloys is not that significant that from the patients point of view the lower alloys should the choice. Due to the system of health insurance, this cost calculation from the production point of view looks different for the organizations that are reimbursing the patient for his expenses, as these organizations are not entitled to the scrap value of old restorations.

Cost-Benefit Analysis↗
PubMed1989

[Bactericidal effects of antiseptic gypsum].

In tests with plaster models we inspected the antibacterial effect of the dental plasters Dento-rock and Dento-dur. The results show, that models consisting of plaster that contains Chloramin T 80 were free of bacteria, even when produced from bacterial contaminated alginate impressions. After separation of the plaster models from the alginate impressions, a bactericide effect could be traced to a layer of 220 microns below the surface of the alginate. By using dental plaster of the tested types, it is therefore possible to eliminate the risk of a bacterial infection through plaster models, without any extra investing in time or labor. There is no sign of a negative influence of chloramin on physical parameters of the tested plasters.

Alginates↗
PubMed1989

[Is the T-scan system a relevant diagnostic method for occlusal control?].

The T-Scan system has recently been introduced to the market as a computer-aided device for direct monitoring and documentation of individual occlusal patterns. To receive first assessments of diagnostic relevance of this method, sensitivity and planar resolution capacities of the T-Scan system was tested in an in-vitro study, that showed a lack in the resolution capacity and an excessive variation in sensor sensitivity. Therefore the clinical use of the system is very limited.

Dental Occlusion, Balanced↗
PubMed1989

[Comparative analytic occlusal study of clinical use of T-scan systems].

Occlusal corrections are dependent on a precise registration. The T-Scan system has recently been presented to the market as an innovative, computer-aided device, capable of providing exact information regarding position, strength and frequency of occlusal contacts. The diagnostic validity of this technique was tested in a comparing study on 16 patients. The occlusal situation of these patients was analyzed by use of the T-Scan system and the markings compared with those obtained from UV-sensitive articulation foil. The results show that the diagnostic possibilities of the T-Scan system are very much limited. The use oft he T-Scan system as the only means of occlusal analysis cannot be recommended. The main reason for this is an often misleading reproduction of occlusal contacts, caused by the T-Scan-sensor-foil being too thick and too inflexible and therefore creating an uncontrollable shift of the mandibula when closing the bite. However, the T-Scan system seems to be a valuable tool for education of both students and patients, as the on-screen coulour display of occlusal mechanisms are really impressive.

Dental Occlusion, Balanced↗
PubMedDate not supplied

Influence of different bleaching systems on fracture toughness and hardness of enamel.

This study evaluated the influence of different bleaching procedures on the fracture toughness and microhardness of enamel. The labial aspects of 72 bovine incisors were prepared for microhardness determination. At baseline, Knoop hardness (KH) determination was conducted on each specimen. Moreover, the fracture toughness (FT) of enamel was assessed using Vickers hardness indentations with a load of 9.8 N. The length of both indentations and enamel cracks were recorded and used for calculation of FT. The samples were divided among six (A-F) groups (n = 12) and sectioned, resulting in a control and an experimental half. The samples were stored in artificial saliva for 10 days. The experimental halves were removed from the saliva and subjected to bleaching according to manufacturers' instructions (A: Opalescence Xtra, B: Opalescence Quick, C: Rapid White, D: Whitestrips, E: Opalescence 10%, F: Opalescence PF 15%). Bleaching with C-F was conducted daily (C: twice per day for 10 minutes, D: twice per day for 30 minutes, E: 8 hours, F: 4 hours), systems A-B were applied on the first and fifth day (A: twice for 10 minutes, B: 1 hour). Finally, Knoop hardness and FT were assessed and statistically compared to baseline values using Wilcoxon-tests (p < 0.05). KH and FT of the controls remained stable during storage in saliva. All bleaching regimens resulted in a statistically significant percentage loss of KH (mean + standard error of means): A: 17.3 +/- 2.8%, B: 8.6 +/- 3.3%; C: 83.5 +/- 0.61%, D: 29.0 +/- 1.9%, E: 9.0 +/- 2.91%, F: 5.4 +/- 2.2%. The percentage changes (mean + standard error of means) of FT in the experimental specimens were as follows: A: 3.9 +/- 9.5%, B: 0.1 +/- 4.7%; D: -8.2 +/- 7.1%, E: -18.9 +/- 4.7%, F: -12.0 +/- 4.7%. Due to severe surface softening, FT could not be determined for the samples in Group C. Applying Opalescence 10% resulted in a significant reduction in FT compared to baseline. In the remaining groups, changes in FT were not statistically significant.

Animals↗