Rosa M. Guerra

Analysis of citrates and benzoates used in poly(vinyl chloride) by supercritical fluid extraction and gas chromatography.

Supercritical fluid extraction (SFE) has been demonstrated to be a useful tool in the determination of additives in polymeric materials. This paper describes the determination of some citrates and benzoates in poly(vinyl chloride) blended with 33-34% of plasticizer using off-line SFE followed by gas chromatography. Experimental factors affecting SFE have been studied by gravimetric analysis, followed by analysis of the extracts using a gas chromatograph equipped with a flame ionization detector. The extraction process is governed by the solubility of the plasticizers in the supercritical fluid or by their diffusion through the polymer matrix, which depend on the pressure and temperature used. Maximum extraction (>99%) is obtained at pressures and temperatures higher than 40 MPa and 80 degrees C, respectively. Due to purge losses, the collection efficiency of plasticizers into a liquid solvent ranges from 85 to 90%. The applicability of the SFE method is demonstrated using real samples and comparing the results with those obtained by conventional Soxhlet extraction.

Effect of pressure, temperature and time on supercritical fluid extraction of citrate and benzoate plasticisers from poly (vinyl chloride)

Supercritical Fluid Extraction (SFE) has been demonstrated as a useful tool in the analysis of polymeric materials. This paper describes the off-line SFE followed by Gas Chromatography determination of some citrate and benzoate plasticisers used in poly (vinyl chloride) (PVC). Experimental factors affecting SFE with carbon dioxide have been studied by gravimetric analysis. Recoveries of analytes were calculated with the use of a Gas Chromatograph with a flame ionisation detector. The extraction process can be kinetically controlled by the solubility of plasticisers in the supercritical fluid or by their diffusion through the polymer depending on pressure and temperature conditions. Quantitative extractions (>99%) are obtained at 39.5 MPa, 100 °C and 20 min, while some losses in the collection of plasticisers in a liquid solvent (ranges from 85 to 95%) are observed.

Pre-prosthetic Remodeling of Alveolar Ridge Using Calcium Phosphate Biomaterials

Maxilla or mandible alveolar ridge defects are commonly a sequel to dental extractions when preventive treatment of atrophy of the maxillary bone (ABM) is not performed. In order to achieve bone reconstruction of the reabsorbed alveolar ridge, oral surgery is needed. The aim of this paper is to study the combine application in the alveolar ridge remodeling of dental biomaterials Biograft-G®, MEMBRACEL®-O and Tisuacryl®. Eleven patients affected by maxillary alveolar bone atrophy were treated. The evaluation was performed at 7 days and 6 months from surgery. At seven days, no cases of infection were observed, but the presence of edema was reported in two cases and granules exfoliation in one of them. No ARs were observed. At 6 months, 100% of patients achieving a Success in the reconstruction of atrophic alveolar ridge. It is concluded that the combine application of dental biomaterials is effective and safe for the pre-prosthetic alveolar ridge remodeling.

Comportamiento Óseo de Alveolos Dentarios Implantados con Biograft-G®. Evolución de Casos a los 6 meses

Resumen — The maxilla and mandible bones are structures that are part of the facial bones, which are continuous with the alveolar process where the alveolar openings. They keep their shape and size by the presence of dental structures, so that the loss of teeth produces incorrect remodeling called mandibular or maxillary alveolar atrophy. This study aims to determine the behavior and safety of treatment bone in alveolar ridge maintenance when performing dental extractions with a grain size of β-tricalcium phosphate called Biograft-G ®, researched and developed by the Centre of Biomaterials of the University of Havana. This is a research clinic, prospective, multicenter, uncontrolled extraction indicated patient, who underwent conventional treatment by adding fill material referred to and evaluated clinically and radiographically. For the evaluation of the response variables were taken evolves clinically and radio-graphically at seven days, one, three and six months. The radiographic appearance was evaluated in Good, Fair and Poor and the clinical appearance, on two levels Good and Evil The final assessment was revised to 6 months after treatment in the categories of success and failure. The results were shown in tables and figures It was determined that the sample was homogeneous for age and area to be treated, but not for the fe-male sex predominated. In the clinical and radiographic behaved with an increase in the repair and resorption of 7 days to 6 months, mostly degrades the Biograft-G ®. This coincides with what is planted by others that indicate similar materials when they lose their teeth. Demonstrated an adequate performance in the affected bone without any adverse material.