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An Evaluation of Some Mechanical Properties of Autopolymerizing Acrylic Resin with the Modified One after Changing the Curing Environment: (In vitro Study)

Author: Intisar J. Ismail
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2015 Volume: 27 Issue: 4 Pages: 62-71
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Studying and investigating the transverse strength(Ts), impact strength(Is), hardness (Hr) and surfaceroughness(Ra) of conventional and modified autopolymerizing acrylic resin with different weight percentages ofbiopolymer kraftlignin, after curing in different water temperatures; 40°C and 80°C.Material and Methods: Standard acrylic specimens were fabricated according to ADA specification No.12 fortransverse strength, ISO 179 was used for impact testing, Shore D for hardness and profilometerfor surface roughness.The material lignin first dispersed in the monomer, then the powder PMMA is immediately added. Lignin added indifferent weight percentages. Then cured using pressure pot (Ivomet) in two temperatures;40°C and 80°C under 2bar pressure, for 30 minutes.Atotal of 144samples were prepared for this study. Ts, Is, Ra, and Hr were tested, by usingInstron universal testing machine, charpy impact tester, shore D tester, and profilometer respectively.Results: The transverse strength increased in both the conventional and modified onewhen compared with thatcured in air. The addition of 0.5wt% lignin gave the higher effect (78.0017MPa) with highly significant difference foundbetween groups at 40°C polymerizing temperature. While the impact strength in both temperatures in the modifiedresin revealed increased results than conventional one, 1.25wt% of kraft lignin gave the highest value (12.7355KJ/m2)with highly significant differences found between groups at 80°C polymerizing temperature. Hardness and surfaceroughness showed also highly significant differences found between groups at 40°C polymerizing temperature, allthe groups had increased Hr. than the control one (78.95), while the Ra. decreased for 1.0% ,1.25,1.50 and 1.75 wt%lignin content to (0.26,0.10,0.063, 0.12μm) respectively in 40°C polymerizing temperature, the lowest value present in1.75 wt% lignin (0.05 μm) at 80°Cpolymerizing temperature.Conclusions: It seems that increasing the polymerizing temperature to 40°C had a positive effect on the mechanicalproperties of autopolymerizing acrylic resin and the one enforced by kraft lignin biopolymer in low percentages.Increasing the polymerizing temperature to 80°C will doesn’t have much positive effect but it doesn’t deteriorate themechanical properties. However, when submitted to increasing the temperature to 80°C, specimens showed asignificantincrease in impact strength


Article
Effect of the addition of bio-polymer lignin on the Transverse and Impact strength of the autopolymerizing acrylic resin.

Authors: Basima M.A. Hussein باسمة محمد --- Thikra I. Hamad ذكرى حمد --- Intisar J. Ismail انتصار جاسم
Journal: Journal of the Faculty of Medicine مجلة كلية الطب ISSN: 00419419 Year: 2010 Volume: 52 Issue: 3 Pages: 359-363
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Acrylic resin dentures are susceptible to fracture; it is unresolved problem in prosthodontics. The repair procedure should be simple, strong, and accurate. This study evaluated the transverse and impact strength of autopolymerizing acrylic resin, the repair material was modified with kraft lignin as a new enforcement material and compared with the commercially available self cured acrylic resin. Materials and Methods: The addition of kraft lignin to the acrylic resin were done in percentages of 0.25%, 0.5%, 0.75%, 1.0%, 1.25%, and 1.5% (wt%). Seventy specimens were made according to the ADA specification No 12 for transverse strength using three point bending test and Impact strength test was conducted following the procedure given by the ISO 179 with Charpy Type Impact testing instrument.Results: Mean transverse strength of experimental specimens where increased only in 0.25wt% addition of lignin (61.3400 Mpa) then results tend to decrease, and no statistical differences found between the control and any one of the modified groups. The impact strength increased more than the control in the groups 0.25, 0.50, 0.75,and 1.0wt%,13.9700, 15.5900, 35.2100, 33.6900 Kj/m2 respectively, then has been decreased at 1.50wt% until reach value of the control (9.2525 Kj/m2).Highly significant difference was found at 0.5, 0.75 and 1.0wt% (p<0.05).Conclusions: The autopolymerizing acrylic resin exhibited significantly higher impact strength as a result of addition the biopolymer lignin. The transverse strength of the modified specimens was decreased after increasing the weight percent addition of lignin.Key words: Autopolymerizing acrylic resin, KL (kraft lignin), transverse strength, impact strength

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