Effect of Polymerization Cycles on Gloss, Roughness, Hardness and Impact Strength of Acrylic Resins

Abstract

The aim of this study was to evaluate the conventional and boiled polymerization cycles on gloss, roughness, hardness and impact strength of acrylic resins. Samples were made for each Classico and QC-20 materials (n=10) in dental stone molds obtained from rectangular metallic matrices embedded in metallic flasks. The powder-liquid ratio and manipulation of the acrylic resins' were accomplished according to manufacturers' instructions and the resins were conventionally packed in metallic flasks. After polymerization by (1) conventional: 74 °C for 9 h (Classico) and (2) boiled: 20 min (QC-20) cycles, the samples were deflasked after cooling at room temperature and conventionally finished and polished. The properties were evaluated after storage in water at 37 °C for 24 h. Gloss was verified with Multi Gloss 268 meter (Konica Minolta), surface roughness was measured with Surfcorder SE 1700 rugosimeter (Kosaka), Knoop hardness number was obtained with HMV-200 microdurometer, and impact strength was measured in an Otto Wolpert-Werke device by Charpy system (40 kpcm). Data were subjected to Student's t-test (at α=0.05). The results were: Gloss: 67.7 and 62.2 for Classico and QC-20 resins, respectively; Surface roughness: 0.874 and 1.469 Ra-µm for Classico and QC-20, respectively; Knoop hardness: 27.4 and 26.9 for Classico and QC-20, respectively; and Impact strength: 37.6 and 33.6 kgf/cm2 for Classico and QC-20, respectively. No statistically significant difference (p>0.05)were found between the resins for the evaluated properties. In conclusion, conventional and boiled polymerization cycles had similar effects on gloss, roughness, hardness and impact strength of both Classico and QC-20 resins.

Effect of Different Simulated Microwave Disinfection Cycles on Hardness, Roughness and Gloss of Acrylic Resins

“…It is difficult to understand and explain because resins fabricated by the same manufacturer (microwaved Onda Crylx conventional Classico, and conventional Vipi Cril Plus x microwaved Vipi Wave x conventional Vipi Characterized) showed different results when submitted to the same disinfection cycles by microwave irradiation, and also when each resin was evaluated among different microwave cycles. Differently from the current results, the literaturs has shown that conventional and boiled polymerization methods promoted similar roughnesses on the QC-20 and Classico acrylic resins; however, the roughness levels for both resins were higher [24].…”

“…This result is in agreement with the previous study that reported hardness decrease for acrylic resins after microwave irradiation, but no effect was observed on the impact and flexural strength [16]. Moreover, conventional and boiled polymerization cycles promoted similar roughness and surface hardness for QC-20 and Classico resins [24]; however, the hardness levels for both resins were lesser than those seen in the current study. Based on these results, it is possible to presume smaller rigidity of the resins with the increase of the microwave cycles, which seems to confirm the decrease of the Knoop hardness after repeated microwave disinfections [17], after thermal cycling and disinfection procedures [28], and under effect of different polymerization cycles and water storage [29].…”

Effect of Henna Addition on the Surface Roughness and Hardness of Polymethylmethacrylate Denture Base Material: An In-vitro Study

“…It has been reported that resins with high Ra values displayed higher numbers of Candida albicans specimens in comparison to highly polished smooth surfaces, possibly due to the increased hills and peaks of the rougher surfaces, which provide a wide surface area and are more accessible active sites for microbial adhesion (Verran and Maryan, 1997;Radford et al, 1998). Lower surface roughness is important to prevent stain catching (Consani et al, 2016).…”

“…Hardness is important in preventing abrasion and wearing of the PMMA denture base (Consani et al, 2016).…”

Effect of Different Concentration of Disinfectant Incorporated on Hardness of Heat Cured Acrylic Denture Base

“…Wax plate (65 mm long, 5 mm wide and 2 mm high in dimensions) (10) were prepared and fixed into flask. Plaster slurry was prepared and poured in the lower half of flask.…”