RESUMEN
Objective: To evaluate the change of diameter of different injection-molded thermoplastic materials. Material and Methods: Four thermoplastic injection-molded materials were analyzed (Bre.flex 2nd edition, Vertex ThermoSens, Perflex Biosens and Polyan IC). A total of 432 test samples were made in the form of an "hourglass". All samples were divided into three groups: Group I (Control) - consisting of 36 test samples for each type of material, that was not exposed to artificial aging or a wet environment; Group II - consisting of 36 test samples for each type of material, that were artificially aged through dehydration; Group III - specimen were subjected to artificial aging without dehydration. The diameter of each specimen was measured with a digital caliper. Data were analysed using the Student's t-test. Results: Regarding to shrinkage, the samples from the Bf Control group have a mean value of 1.56 mm and was observed a shrinkage of the injection-molded polyamide material within 0.25%. The comparison between the samples from Group II and Group III showed statistically significant differences (p<0.001). There were no significant differences between groups for Thermosens and Biosens (p>0.05). The comparison between Group II and Group III for Polyan IC samples shows that Group III has a higher arithmetic mean value (p<0.01). Conclusion: Shrinkage of the polymers during the injection process is present in all materials. The thermocycling and the storage in a dry or in a wet environment of the samples results in a change of the diameter in almost every single type of material.
Asunto(s)
Prótesis Dental , Materiales de Impresión Dental , Bases para Dentadura , Ciencia de los Materiales , Bulgaria , Interpretación Estadística de DatosRESUMEN
The objective of the present study was to characterize chemically the essential oils of two distinct propolis types: Brazilian red and Taiwanese green. Unlike the non-volatile chemical composition of these types of propolis, which has been extensively studied, the knowledge of the essential oils is scarce or even not investigated. The essential oils were obtained by hydrodistillation of raw propolis samples using a Likens-Nickerson type apparatus and then analyzed by GC/MS. The main volatile components of Brazilian red propolis were the phenylpropanoids: elemicin (26.1-27.5%), methyl eugenol (16.3-23.8%), trans- methyl isoeugenol (9.2-11.6%), isoelemicin (6.1-7.1%) and trans-anethole (4.4-7.1%), while the major constituents of Taiwanese green propolis essential oil were: ß-eudesmol (13.9%), 6-methyl-3,5-heptadiene-2-one (12.2%), y-eudesmol (4.4%), geranial (4.1%) and 6-methyl-5-heptene-2-one (3.7%).