Hacer frente a una desfiguración facial.

.

Effects of chemical disinfectants on surface hardness of heat -cured acrylic resins. In vitro study

Introduction: Acrylic resins (i.e., heat cured acrylic resins) are the most common materials used to manufacture removable dental prostheses involving maxillofacial prostheses such as obturators. Their mechanical and physical properties must be adequate for their use and durability. It is therefore vital to assess how their properties are affected by different disinfectants. Aims: The purpose of this research was to evaluate the effect of chemical disinfectants on surface hardness of the acrylic resins. Material and Methods: Forty specimens (65 mm in length, 10 mm in width and 2.5 mm thick) were manufactured from heat cured acrylic resins for hardness testing according to ISO 1567:1999. The study consisted of four main sets according to the disinfectants applied (control, 1% hypochlorite, 4 % chlorhexidine, and Efferdent®) and each set contained ten specimens. All specimens were placed in saline solution at 37°C and incubated for 60 days. Acrylic specimens were then tested by using a hardness tester three times and the average reading was recorded. All data were analyzed using SPSS version 16. The results were analyzed at a significant level (p≤0.05). The ANOVA (analysis of variance) test was used to assess whether there were any significant differences among all groups. The comparisons between means were obtained by using a Tukey test. Results: There was a slight decrease in the mean values of surface hardness after immersing in chemical disinfectants. The chlorhexidine-assigned specimens had the lowest value of mean surface hardness. On the other hand, the control group had the highest mean value. However, there were no significant differences regarding surface hardness among all groups (p>0.05). Conclusion: The use of chemical disinfectants slightly decreases the surface hardness of heat-cured acrylic resins

Evaluation of the Effect of Nano and Micro Hydroxyapatite Particles on the Impact Strength of Acrylic Resin: In Vitro Study

Poly (methylmethacrylate) is considered the basis material for a denture base. However, such substance has some drawbacks such as poor impact resistance, which is thought to be the primary cause of fracture of denture base resins. The purpose of the study was to determine how Nano and Micro hydroxyapatite particles affected the impact strength of acrylic resin. Thirty specimens were constructed of heat-cured acrylic resin and were divided into three groups: Ten specimens for the control, 10 for 1%nano hydroxyapatite, and 10 for micro hydroxyapatite. Acrylic samples were subjected to an impact strength test via a Charpy-type. Data were then analysed using SPSS v20. The ANOVA test was used for comparison among the groups. Highly statistically significant differences among all studied groups (P-value <0.0001). Both 5% Micro hydroxyapatite and 1% Nano hydroxyapatite had a higher mean value than the control. Incorporating Nano and Micro hydroxyapatite into PMMA improved the impact strength of acrylic resins

Effect of the incorporation of zinc oxide nanoparticles on the flexural strength of auto- polymerized acrylic resins.

Las resinas acrílicas autopolimerizadas se usan comúnmente en muchas aplicaciones en odontología, incluyendo la rehabilitación maxilofacial, en prótesis provisionales, reparación de prótesis, revestimientos, en aparatos de ortodoncia, bases de registro, entre otros. Estas sustancias, sin embargo, tienen algunos aspectos negativos tales como propiedades mecánicas deficientes. Objetivo: el objetivo del presente estudio fue evaluar el efecto de la incorporación de nanopartículas de óxido de zinc en la resistencia a la flexión de resinas acrílicas autopolimerizadas. Materiales y métodos: Treinta muestras de resinas acrílicas autopolimerizadas fueron hechas, divididas en tres grupos principales (un grupo control y dos experimentales), cada grupo con diez especímenes. Se incorporó polvo de óxido de zinc en los dos grupos experimentales, en concentraciones de 1% y 2%, respectivamente. Las muestras de acrílico se fabricaron con una dimensión de 65mm de longitud, 10mm de ancho y 2,5mm de espesor según la especificación ISO 1567 1999. Cada muestra se sometió a la prueba de resistencia a la flexión mediante una máquina de prueba universal. La velocidad de la cruceta para la prueba de resistencia a la flexión fue de 5mm/min hasta que se produjo la fractura. Se utilizó la versión SPSS 16 para el análisis estadístico. El ANOVA y Tukey se utilizaron para la comparación entre todos los grupos. Resultados: Se observó un aumento significativo (p<0.001) en la resistencia a la flexión de las resinas acrílicas luego de la adición de partículas de óxido de zinc (grupo de control: 133,27 SD 1,73 MPa, ZnO 1%: 154,28 SD 2,90 MPa, ZnO 2%: 176,45 SD 0,94 MPa). Conclusiones: La incorporación de nanopartículas de óxido de zinc tiene un efecto significativo en la resistencia a la flexión de las resinas acrílicas autopolimerizadas.Background: Auto-polymerized acrylic resins are commonly used in many applications in dentistry including in maxillofacial rehabilitation such as interim prostheses, denture repair, reline, orthodontic appliances, record base, among others. These substances, however, have some negative aspects such as poor mechanical properties. Aim: The objective of the current study was to evaluate the effect of incorporating zinc oxide nanoparticles to auto-polymerized acrylic resins on their flexural strength. Materials and methods: Thirty specimens were made from auto-polymerized acrylic resins, divided into three main groups (1 control and 2 experimental). Each group had ten specimens. The two experimental groups comprised the zinc oxide powder at 1% and 2% concentrations, respectively. Acrylic specimens were fabricated with the dimension of 65mm length, 10mm width and 2.5mm thickness according to ISO 1567 specification 1999. Each specimen was subjected to the flexural strength test by a universal testing machine. The crosshead speed for the flexural strength test was 5mm/min until fracture occurred. The SPSS version 16 was utilized for the statistical analysis. The ANOVA and Tukey were used for the comparison among all groups. Results: there was a significant increase (p<0.001) in the flexural strength of the acrylic resins following the addition of zinc oxide particles (control group: 133.27 SD 1.73, ZnO 1%: 154.28 SD 2.90, ZnO 2%: 176.45 SD 0.94). Conclusions: The incorporation of zinc oxide nanoparticles has a significant effect on the flexural strength of auto-polymerized acrylic resins

Evaluation of the impact of nano and micro-hydroxyapatite particles on the transverse strength and hardness of PMMA material

Poly (methyl methacrylate) is considered as the basis material for a denture base. However, such substance has some drawbacks such as poor impact resistance, which is thought to be the primary cause of fracture of denture base resins. The purpose of the study was to determine how Nano and Micro hydroxyapatite particles affected the transverse strength and surface hardness of Poly methyl methacrylate. sixty samples were prepared in total and divided into 2 main sets according to the test used (surface hardness and transverse). For each test, there were 3 groups (control, 1% HA nanofiller and 5% HA microfiller) and each group had 10 samples. All samples were subjected to transverse strength and Hardness test. Data were then analyzed using SPSS v20. The ANOVA test used for comparison among the groups. The addition of Nano and Micro hydroxyapatite to polymethyl methacrylate (PMMA) decreased the transverse strength of the heat-polymerized acrylic resins. Furthermore, the incorporation of Nano and Micro hydroxyapatite improved the surface hardness of the heat-polymerized acrylic resins. Incorporating Nano and Micro hydroxyapatite to PMMA improved the sur-face hardness and decreased the transverse strength of acrylic resins