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A G Dias

Publications and source records attributed to A G Dias.

7 recordsLinked to original sources
PubMed2006

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system.

The aim of this work was to evaluate the in vitro degradation behaviour of a 45CaO-37P(2)O(5)-5MgO-13TiO(2) (mol.%) glass ceramic, under two different simulated physiological conditions: normal physiological pH 7.4, and pH 3.0, which was designed to simulate the acidic conditions produced by osteoclast cells. The in vitro testing was carried out at 37 degrees C for up to 42 days for the pH 7.4 solution and for up to 1 day for the pH 3.0 solution. The incorporation of TiO(2) into the glass structure leads to the precipitation of specific crystalline phases in the glass matrix, namely alpha- and beta-Ca(2)P(2)O(7), TiP(2)O(7) and CaTi(4)(PO(4))(6). The degradation testing at pH 3.0 showed a higher weight loss compared with degradation testing at pH 7.4; the weight loss under the acidic condition after 1 day (24 h) was about 10 times higher than the weight loss after 42 days of immersion at pH 7.4. The ionic release profile of Ca(2+), PO(4)(3-), Mg(2+) and Ti(4+) showed a continuous increase in concentration over all immersion times for both testing solutions. After 1 day of immersion at pH 3.0, the concentration levels of Mg(2+), Ca(2+), PO(4)(3-) were about six times higher than the levels achieved after 42 days of immersion at pH 7.4. The glass ceramic showed similar degradation to hydroxyapatite, and therefore has potential to be used in certain clinical applications where relatively slow resorption of the implant and replacement by bone is required, e.g. cranioplasty.

Biocompatible Materials↗
PubMed2006

In vivo performance of biodegradable calcium phosphate glass ceramics using the rabbit model: histological and SEM observation.

Two MK5 (45CaO-45P(2)O(5)-5MgO-5K(2)O, in mol%) and MT13 (45CaO-37P(2)O(5)-5MgO-13TiO(2), in mol%) glasses are prepared in the meta- and pyrophosphate regions and crystallized to obtain MK5B and MT13B, respectively. MK5B was obtained by controlled crystallization, and MT13B by powder sintering. As a result of these heat treatment processes, the crystalline phases precipitated in the glassy matrix are KCa(PO(3))(3), beta-Ca(PO(3))(2), beta-Ca(2)P(2)O(7) and Ca(4)P(6)O(19) phases for MK5B and CaTi(4)(PO(4))(6), TiP(2)O(7), alpha- and beta-Ca(2)P(2)O(7) phases for MT13B. To assess the in vivo biological behavior of these glass ceramics, a mixed granulometry in the range 250-355 mum and 355-425 mum with a ratio of 1/1 was implanted for 2, 4, and 12 weeks in the tibiae of Japanese white rabbits. The results showed that the in vivo behavior was strongly affected by their solubility. All implanted materials, MK5B and MT13B, and beta-tricalcium phosphate (beta-TCP) as control material, showed signs of degradation in vivo. However, the levels of degradation were quite different throughout the implantation periods. The highest degradation was observed for MK5B glass ceramic and the lowest for MT13B with beta-TCP in-between. All implanted materials allow for new bone formation in the bone defect area. At the longest implantation period (12 weeks), the MT13B and beta-TCP materials were almost completely surrounded by new bone tissue, whereas MK5B showed some unfilled spaces. This behavior is discussed in terms of the high degradation observed in previous studies.

Absorbable Implants↗
PubMed2005

In vitro studies of calcium phosphate glass ceramics with different solubility with the use of human bone marrow cells.

Two glass ceramics in the CaO--P2O5--MgO system with the incorporation of K2O or TiO2 oxides were prepared with the goal of using them as potential bone graft substitutes. The incorporation of TiO2 and K2O led to the preparation of specific crystalline phases in the structure of the glass ceramics, which show different degrees of biodegradation. In fact, the 45CaO--45P2O5--5MgO--5K2O has been previously demonstrated to be much more soluble in aqueous solutions than the 45CaO--37P2O5--5MgO--13TiO2 glass ceramic. The in vitro biological activity of the two calcium phosphate glass ceramics was studied with the use of human bone marrow osteoblast cell cultures maintained for 28 days, and seeded materials were assessed for cell proliferation and function. The Ti-containing glass ceramic showed a stable surface throughout the culture time, on macroscopic and SEM observation. Osteoblast cells proliferated gradually, especially during the third week, with a high alkaline phosphatase activity and formation of a mineralized matrix. On SEM observation, attached cells appeared with a spread-polygonal morphology typical of the osteoblast cells, with extensive cell-to-cell contact. Cell behavior on the seeded material was similar to that found on cultures performed on tissue-culture-grade polystyrene; except for the presence of lower cell numbers during the first 2 weeks. By contrast, the K-containing glass ceramic showed a highly instable surface with dissolution/precipitation processes occurring throughout the culture time. Few cells adhered to the material surface, and subsequent proliferation was also hindered, especially from the first week onwards. Cell numbers were significantly lower than those observed in the Ti-containing glass ceramic during most of the incubation time. Results suggest that the different in vitro biological behavior of these two glass ceramics is mainly due to the significant differences in the surface degradation rate, which is directly correlated to the chemical composition of the mother glass.

Alkaline Phosphatase↗
PubMed1995

[Knowledge and use of alternative medicine among elementary school students and teachers].

The knowledge and use of popular cures was investigated as part of health education project in such a way as to develop and expand the existing possibilities for critical and constructive discussion in the school within the health program. It was hoped that this would result in the retrieval and in an increase in the value attributed to information concerning this nonsystematized knowledge present in a controversial and poorly accepted form in the practices of the population. One hundred and five teachers and 162 students of the 1st to 4th grades of the four primary schools on the outskirts of Belo Horizonte were interviewed. One hundred and five of the teachers answered the questions put. Twenty-three (32.4%) of the teachers said they believed in special cures, 69 (65.7%) thought that certain diseases could be treated with homemade remedies for these, 54 (78.3%) were able to associate a particular disease with a particular medicinal plant and 15 (21.7%) prescribed a treatment without any association with a particular disease, 36 (34.3%) cited a disease without relating this to a particular herb. One hundred and one (62.3%) of the students believed that homemade remedies are effective for certain diseases. Amongst the teachers and students various diseases were mentioned as well as different symptoms and organs that can be cured by medicinal plants, roots or traditional healers. A little more than 50% of the two groups of students (1st and 2nd grade, 3rd and 4th grade) live in families who make use of traditional healers to provide alternative cures.(ABSTRACT TRUNCATED AT 250 WORDS)

Brazil↗
PubMedDate not supplied

[Health education in 1st grade public schools at the periphery of Belo Horizonte, MG, Brazil. I. Evaluation of the program relative to schistosomiasis].

A project has been developed with the objective of implanting and testing new materials and methodologies related to health education in first level schools. The present study is being performed in 4 public schools of a periferic area of Belo Horizonte, in two regions, one of high and another of low prevalence of schistosomiasis. The experimental design includes 2 experimental schools and 2 of control. The procedure involves interviews with teachers and students before and after the experimental test of the new materials; stool surveys and treatment of the sample of students. The results of the first interviews demonstrated that the knowledge of schistosomiasis is almost absent among teachers and students, although the prevalence of this disease has been maintained for a long time (70 years) in one of the regions studied (Gorduras). Out of 3131 students of the 4 schools, 67.5% were examined and 235 (11.0%) were tested positively. When the new students of 1989 were not included the prevalence decrease to 9.0% demonstrating a significative difference (X2 - 5%) in relation to 1988, showing the consequence of the treatment performed. Comparing the 2 schools of high prevalence, the decrease of prevalence of the experimental one is higher than the control. Therefore, in relation to the schools of low prevalence, the same has not happened. Thus, it is only possible to suggest an initial effect of the educative strategy and the decreases of the prevalence in the schools of high prevalence. In relation to the knowledge about the disease transmission, the students from the experimental schools presented a significative increase of correct answers in 1989 than the control ones.

Brazil↗