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Aune Raustia - One of the best experts on this subject based on the ideXlab platform.
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flexural and surface properties of pmma Denture Base Material modified with thymoquinone as an antifungal agent
Journal of Prosthodontics, 2020Co-Authors: Ahmad M Althobity, Ritva Näpänkangas, Aune Raustia, Shaimaa M FoudaAbstract:PURPOSE: To evaluate the effect of addition of different concentrations of thymoquinone (TQ) on the flexural strength, elastic modulus, surface roughness, and hardness of PMMA Denture Base Material. MaterialS AND METHODS: A total of 160 rectangular specimens were prepared from heat-polymerized acrylic resin, with dimensions of 65 × 10 × 2.5 mm3 for flexural strength testing and 10 × 20 × 3 mm3 for surface property testing. The specimens were divided into eight groups of 20 specimens: one control group without addition of TQ and seven test groups prepared by adding TQ to acrylic powder in concentrations of 0.5, 1, 1.5, 2, 2.5, 3, and 5 wt%. The polymer was added to the monomer before being mixed, packed, and processed using the conventional water bath method. A universal testing machine was used to measure flexural strength and elastic modulus. A profilometer and a Vickers hardness tester were used to measure surface roughness and hardness, respectively. One-way ANOVA and the Tukey-Kramer multiple-comparison test were used for statistical analysis, with statistical significance at p ≤ 0.05. RESULTS: Addition of TQ to PMMA Denture Base Material significantly decreased flexural strength and elastic modulus at high concentrations (p < 0.01), while no significant differences were observed at low concentrations (0.5%, 1% TQ) in comparison with the control group. At high TQ concentrations, surface roughness increased while hardness decreased (p < 0.0001), and no significant differences were observed at low concentrations (0.5%, 1% TQ) in comparison with the control group. The most favorable addition values were 0.5% and 1% TQ in all TQ groups. CONCLUSIONS: Addition of TQ did not affect the flexural and surface properties of PMMA Denture Base Material at low concentrations (0.5%, 1% TQ) and could be incorporated into PMMA Denture Base Material as an antifungal agent.
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PMMA Denture Base Material enhancement: A review of fiber, filler, and nanofiller addition
International Journal of Nanomedicine, 2017Co-Authors: Mohammed M. Gad, Ritva Näpänkangas, Sameh M. Fouda, Fahad A. Al-harbi, Aune RaustiaAbstract:This paper reviews acrylic Denture Base resin enhancement during the past few decades. Specific attention is given to the effect of fiber, filler, and nanofiller addition on poly(methyl methacrylate) (PMMA) properties. The review is Based on scientific reviews, papers, and abstracts, as well as studies concerning the effect of additives, fibers, fillers, and reinforcement Materials on PMMA, published between 1974 and 2016. Many studies have reported improvement of PMMA Denture Base Material with the addition of fillers, fibers, nanofiller, and hybrid reinforcement. However, most of the studies were limited to in vitro investigations without bioactivity and clinical implications. Considering the findings of the review, there is no ideal Denture Base Material, but the properties of PMMA could be improved with some modifications, especially with silanized nanoparticle addition and a hybrid reinforcement system.
Mohammed M. Gad - One of the best experts on this subject based on the ideXlab platform.
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antifungal efficacy and physical properties of poly methylmethacrylate Denture Base Material reinforced with sio2 nanoparticles
Journal of Prosthodontics, 2020Co-Authors: Sara T Alzayyat, Sultan Akhtar, Ghadah A Almutiri, Jawhara K Aljandan, Raneem M Algarzai, Soban Q Khan, Asif Matin, Mohammed M. GadAbstract:Purpose To evaluate the effect of the addition of low concentration of silicon-dioxide nanoparticles (nano-SiO2 ) to poly(methylmethacrylate) (PMMA) Denture Base Material on Candida albicans adhesion, surface roughness, contact angle, hardness, and translucency. Materials and methods A total of 150 acrylic disks were fabricated from heat-polymerized acrylic resin and specimens were divided into 3 groups of 50 per test. They were further subdivided into 5 subgroups (n = 10) according to the concentration of nano-SiO2 : control (no addition) and four tested groups modified with 0.05, 0.25, 0.5, and 1.0 wt% nano-SiO2 of acrylic powder. Slide count and direct culture methods were used to measure C. albicans count (CFU/mL). The surface roughness values (Ra ; μm) were determined using a profilometer. The contact angle (o ) measurement was performed by a goniometer using the sessile drop method. Vickers hardness was used to analyze surface hardness. Translucency was measured using a spectrophotometer. Data analysis was conducted through analysis of variance and Tukey's post hoc tests (α = 0.05). Results Compared to the control group, direct culture and slide count methods illustrated a significant decrease in C. albicans count (p ˂ 0.001) with the addition of nano-SiO2 , and this decrease was correlated with the concentration of nano-SiO2 . The addition of nano-SiO2 significantly decreased the contact angle (p ˂ 0.001), whereas hardness and surface roughness significantly increased (p ˂ 0.001). The addition of nano-SiO2 significantly decreased translucency (p ˂ 0.001), and this decrease was concentration dependent. Conclusion Addition of low concentration of nano-SiO2 decreased C. albicans adhesion to PMMA Denture Base resin. Also, low additions of nano-SiO2 have positive effects on contact angle and hardness, whereas surface roughness and translucency were adversely affected at high concentrations.
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influence of addition of different nanoparticles on the surface properties of poly methylmethacrylate Denture Base Material
Journal of Prosthodontics, 2020Co-Authors: Mohammed M. Gad, Ahmad M Althobity, Reem Abualsaud, Nadim Z Baba, Fahad A AlharbiAbstract:PURPOSE To evaluate and compare the surface properties (roughness and hardness) of poly(methylmethacrylate) Denture Base Material modified with zirconium dioxide (ZNPs), silicon dioxide (SNPs), and diamond (DNPs) nanoparticles. MaterialS AND METHODS Two hundred sixty heat-polymerized acrylic resin disks (15 × 2 mm) were prepared. ZNPs, SNPs, and DNPs were added in concentrations of 0%, 0.5%, 1.0%, 2.5%, and 5.0% by weight of acrylic powder. This yielded a total of 13 groups for each test according to filler type and concentration (n = 10/group). The control group was made of pure acrylic. A mechanical polisher was used to standardize specimens' surfaces before testing. A profilometer and Vickers hardness indenter were used to test the surface roughness and hardness, respectively. ANOVA and Tukey post hoc tests were used for data analysis (α = 0.05). RESULTS In comparison to control, results showed a nonsignificant increase in surface roughness (Ra ) of acrylic Material after the addition of 0.5% nanoparticles (ZNPs p = 0.168, SNPs p = 0.166, and DNPs p = 0.177), while a significant increase was seen with all other concentrations (p ˂ 0.05). Ra values of ZNP and DNP groups were significantly higher than those of the SNPs group (p < 0.001). The addition of any of the fillers to acrylic Denture Base Materials significantly increased the hardness (p ˂ 0.05), with ZNPs and DNPs having values lower than those of the SNPs group (p < 0.001). CONCLUSIONS Although nanofiller addition increased the hardness of Denture Base Material, Ra was adversely affected when the concentration exceeded 0.5%. Therefore, 0.5% is suggested to be the most appropriate ratio to improve hardness with acceptable Ra .
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effect of henna addition on the surface roughness and hardness of polymethylmethacrylate Denture Base Material an in vitro study
The journal of contemporary dental practice, 2018Co-Authors: Amal Nawasrah, Mohammed M. Gad, Mai El ZayatAbstract:AIM This study aimed to evaluate the effect of the addition of various henna-which can have antifungal properties-on the surface roughness and hardness of polymethylmethacrylate (PMMA) Denture Base Material. MaterialS AND METHODS A total of 99 rectangular-shaped (10 × 20 × 3 mm3) specimens were prepared from heat-cured acrylic resin and divided into one control group without the addition of henna and five test groups, which were prepared by adding Yamanihenna powder to polymer at concentrations of 1, 2.5, 5, 7.5, and 10 wt%. The polymer was added to the monomer, mixed, packed, and processed using the conventional water bath method. After processing, specimens were finished and polished, then kept in distilled water for 48 ± 2 hours. A profilom-eter and Vickers hardness tester were used to measure surface roughness and hardness respectively. Statistical data analysis was conducted via Statistical Package for the Social Sciences (SPSS) version 20.0 (IBM, USA). The independent sample t-test was used and p ≤ 0.05 was considered statistically significant. RESULTS The addition of henna at varying concentrations significantly increased the surface roughness values (p ≤ 0.01) while decreasing hardness (p ≤ 0.0001). The most favorable addition value was 1% henna between all henna groups. CONCLUSION The addition of henna to the acrylic resin may negatively affect the surface properties of PMMA acrylic Denture Base. CLINICAL SIGNIFICANCE Antimicrobial Denture with minimum deterioration effects on its physical properties could be achieved with henna addition to Denture Base Material in low concentration. However, 1% henna showed the best results between the henna groups as regards roughness and hardness values.
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PMMA Denture Base Material enhancement: A review of fiber, filler, and nanofiller addition
International Journal of Nanomedicine, 2017Co-Authors: Mohammed M. Gad, Ritva Näpänkangas, Sameh M. Fouda, Fahad A. Al-harbi, Aune RaustiaAbstract:This paper reviews acrylic Denture Base resin enhancement during the past few decades. Specific attention is given to the effect of fiber, filler, and nanofiller addition on poly(methyl methacrylate) (PMMA) properties. The review is Based on scientific reviews, papers, and abstracts, as well as studies concerning the effect of additives, fibers, fillers, and reinforcement Materials on PMMA, published between 1974 and 2016. Many studies have reported improvement of PMMA Denture Base Material with the addition of fillers, fibers, nanofiller, and hybrid reinforcement. However, most of the studies were limited to in vitro investigations without bioactivity and clinical implications. Considering the findings of the review, there is no ideal Denture Base Material, but the properties of PMMA could be improved with some modifications, especially with silanized nanoparticle addition and a hybrid reinforcement system.
Ahmad M Althobity - One of the best experts on this subject based on the ideXlab platform.
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influence of addition of different nanoparticles on the surface properties of poly methylmethacrylate Denture Base Material
Journal of Prosthodontics, 2020Co-Authors: Mohammed M. Gad, Ahmad M Althobity, Reem Abualsaud, Nadim Z Baba, Fahad A AlharbiAbstract:PURPOSE To evaluate and compare the surface properties (roughness and hardness) of poly(methylmethacrylate) Denture Base Material modified with zirconium dioxide (ZNPs), silicon dioxide (SNPs), and diamond (DNPs) nanoparticles. MaterialS AND METHODS Two hundred sixty heat-polymerized acrylic resin disks (15 × 2 mm) were prepared. ZNPs, SNPs, and DNPs were added in concentrations of 0%, 0.5%, 1.0%, 2.5%, and 5.0% by weight of acrylic powder. This yielded a total of 13 groups for each test according to filler type and concentration (n = 10/group). The control group was made of pure acrylic. A mechanical polisher was used to standardize specimens' surfaces before testing. A profilometer and Vickers hardness indenter were used to test the surface roughness and hardness, respectively. ANOVA and Tukey post hoc tests were used for data analysis (α = 0.05). RESULTS In comparison to control, results showed a nonsignificant increase in surface roughness (Ra ) of acrylic Material after the addition of 0.5% nanoparticles (ZNPs p = 0.168, SNPs p = 0.166, and DNPs p = 0.177), while a significant increase was seen with all other concentrations (p ˂ 0.05). Ra values of ZNP and DNP groups were significantly higher than those of the SNPs group (p < 0.001). The addition of any of the fillers to acrylic Denture Base Materials significantly increased the hardness (p ˂ 0.05), with ZNPs and DNPs having values lower than those of the SNPs group (p < 0.001). CONCLUSIONS Although nanofiller addition increased the hardness of Denture Base Material, Ra was adversely affected when the concentration exceeded 0.5%. Therefore, 0.5% is suggested to be the most appropriate ratio to improve hardness with acceptable Ra .
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flexural and surface properties of pmma Denture Base Material modified with thymoquinone as an antifungal agent
Journal of Prosthodontics, 2020Co-Authors: Ahmad M Althobity, Ritva Näpänkangas, Aune Raustia, Shaimaa M FoudaAbstract:PURPOSE: To evaluate the effect of addition of different concentrations of thymoquinone (TQ) on the flexural strength, elastic modulus, surface roughness, and hardness of PMMA Denture Base Material. MaterialS AND METHODS: A total of 160 rectangular specimens were prepared from heat-polymerized acrylic resin, with dimensions of 65 × 10 × 2.5 mm3 for flexural strength testing and 10 × 20 × 3 mm3 for surface property testing. The specimens were divided into eight groups of 20 specimens: one control group without addition of TQ and seven test groups prepared by adding TQ to acrylic powder in concentrations of 0.5, 1, 1.5, 2, 2.5, 3, and 5 wt%. The polymer was added to the monomer before being mixed, packed, and processed using the conventional water bath method. A universal testing machine was used to measure flexural strength and elastic modulus. A profilometer and a Vickers hardness tester were used to measure surface roughness and hardness, respectively. One-way ANOVA and the Tukey-Kramer multiple-comparison test were used for statistical analysis, with statistical significance at p ≤ 0.05. RESULTS: Addition of TQ to PMMA Denture Base Material significantly decreased flexural strength and elastic modulus at high concentrations (p < 0.01), while no significant differences were observed at low concentrations (0.5%, 1% TQ) in comparison with the control group. At high TQ concentrations, surface roughness increased while hardness decreased (p < 0.0001), and no significant differences were observed at low concentrations (0.5%, 1% TQ) in comparison with the control group. The most favorable addition values were 0.5% and 1% TQ in all TQ groups. CONCLUSIONS: Addition of TQ did not affect the flexural and surface properties of PMMA Denture Base Material at low concentrations (0.5%, 1% TQ) and could be incorporated into PMMA Denture Base Material as an antifungal agent.
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the effect of nanodiamonds on candida albicans adhesion and surface characteristics of pmma Denture Base Material an in vitro study
Journal of Applied Oral Science, 2019Co-Authors: Shaimaa M Fouda, Ahmad M Althobity, Passent Ellakany, Fahad A Alharbi, Jorma I VirtanenAbstract:: Candida albicans is the main causative pathogen of Denture stomatitis, which affects many complete Denture patients. OBJECTIVE: To evaluate the effect of different concentrations of nanodiamonds (NDs) added to polymethyl methacrylate (PMMA) Denture Base Material on Candida albicans adhesion as well as on surface roughness and contact angle. METHODOLOGY: Acrylic resin specimens sized 10×10×3 mm3 were prepared and divided into four groups (n=30) according to ND concentration (0%, 0.5%, 1%, 1.5% by wt). Surface roughness was measured with a profilometer, and the contact angle with a goniometer. The effect of NDs on Candida albicans adhesion was evaluated using two methods: 1) slide count and 2) direct culture test. Analysis of variance (ANOVA) and Tukey's post hoc test were used in the statistical analyses. RESULTS: Addition of NDs decreased the Candida albicans count significantly more than in the control group (p<0.05), with a lowest of 1% NDs. Addition of NDs also significantly decreased the surface roughness (p<0.05), but the contact angle remained the same. Incorporation of NDs into the PMMA Denture Base Material effectively reduced Candida albicans adhesion and decreased surface roughness. CONCLUSION: PMMA/NDs composites could be valuable in the prevention of Denture stomatitis, which is considered one of the most common clinical problems among removable Denture wearers.
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effect of polymerization technique and glass fiber addition on the surface roughness and hardness of pmma Denture Base Material
Dental Materials Journal, 2018Co-Authors: Ahmed Rahoma, Ahmad M AlthobityAbstract:: The current study evaluated the effects of autoclave polymerization both with and without glass fiber (GF) reinforcement on the surface roughness and hardness of acrylic Denture Base Material. Ninety disc specimens (30×2.5 mm) were prepared from Vertex resin and divided according to polymerization techniques into a water bath, short and long autoclave polymerization groups. Tested groups were divided into three subgroups according to the GF concentration (0, 2.5, and 5 wt%). Profilometer and Vickers hardness tests were performed to measure surface roughness and hardness. ANOVA and Tukey-Kramer multiple comparison tests analyzed the results, and p≤0.05 was considered statistically significant. Autoclave polymerization significantly decreased the surface roughness and increased the hardness of acrylic resin without GF reinforcement (p<0.05). However, 5 wt% GF addition significantly increased surface roughness and decreased hardness of the autoclave polymerized Denture Base resin (p<0.05). Surface properties of Polymethyl methacrylate (PMMA) Denture Base Material improved with autoclave polymerization and negatively affected with GFs addition.
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effect of zirconium oxide nanoparticles addition on the optical and tensile properties of polymethyl methacrylate Denture Base Material
International Journal of Nanomedicine, 2018Co-Authors: Reem Abualsaud, Ahmad M Althobity, Ahmed Rahoma, Khalid S Alabidi, Sultan AkhtarAbstract:Background: Polymethyl methacrylate (PMMA) is widely used for the fabrication of removable prostheses. Recently, zirconium oxide nanoparticles (nano-ZrO2) have been added to improve some properties of PMMA, but their effect on the optical properties and tensile strength are neglected. Objective: The aim of this study was to investigate the effect of nano-ZrO2 addition on the translucency and tensile strength of the PMMA Denture Base Material. Materials and methods: Eighty specimens (40 dumbbell-shaped and 40 discs) were prepared out of heat-polymerized acrylic resin and divided into four groups per test (n=10). The control group for each test included unreinforced acrylic, while the test groups were reinforced with 2.5, 5, and 7.5 wt% nano-ZrO2. Acrylic resin was mixed according to manufacturer's instructions, packed, and processed by conventional method. After polymerization, all specimens were finished, polished, and stored in distilled water at 37°C for 48±2 hours. Tensile strength (MPa) was evaluated using the universal testing machine while the specimens' translucency was examined using a spectrophotometer. Statistical analysis was carried out by SPSS using the paired sample t-test (p≤0.05). A scanning electron microscope was used to analyze the morphological changes and topography of the fractured surfaces. Results: This study showed that the mean tensile strength of the PMMA in the test groups of 2.5%NZ, 5%NZ, and 7.5%NZ was significantly higher than the control group. The tensile strength increased significantly after nano-ZrO2 addition, and the maximum increase seen was in the 7.5%NZ group. The translucency values of the experimental groups were significantly lower than those of the control group. Within the reinforced groups, the 2.5%NZ group had significantly higher translucency values when compared to the 5%NZ and 7.5%NZ groups. Conclusion: The addition of nano-ZrO2 increased the tensile strength of the Denture Base acrylic. The increase was directly proportional to the nano-ZrO2 concentration. The translucency of the PMMA was reduced as the nano-ZrO2 increased. Clinical significance: Based on the results of the current study, the tensile strength was improved with different percentages of nano-ZrO2 additions. However, translucency was adversely affected. Therefore, it is important to determine the appropriate amount of reinforcing nano-ZrO2 that will create a balance between achieved properties - mechanical and optical.
Mieszko Wieckiewicz - One of the best experts on this subject based on the ideXlab platform.
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antifungal and surface properties of chitosan salts modified pmma Denture Base Material
Molecules, 2020Co-Authors: Katarzyna Walczak, Georg Schierz, Sabine Basche, Carola Petto, Klaus W Boening, Mieszko WieckiewiczAbstract:Chitosan (CS) and its derivatives show antimicrobial properties. This is of interest in preventing and treating Denture stomatitis, which can be caused by fungi. Therefore, the aim of this study was the development of a novel antifungal Denture Base Material by modifying polymethyl methacrylate (PMMA) with CS-salt and characterizing its antifungal and surface properties in vitro. For this purpose, the antifungal effect of chitosan-hydrochloride (CS-HCl) or chitosan-glutamate (CS-G) as solutions in different concentrations was determined. To obtain modified PMMA resin specimens, the CS-salts were added to the PMMA before polymerization. The roughness of these specimens was measured by contact profilometry. For the evaluation of the antifungal properties of the CS-salt modified resins, a C. albicans biofilm assay on the specimens was performed. As solutions, both the CS-G and CS-HCl-salt had an antifungal effect and inhibited C. albicans growth in a dose-dependent manner. In contrast, CS-salt modified PMMA resins showed no significant reduced C. albicans biofilm formation. Furthermore, the addition of CS-salts to PMMA significantly increased the surface roughness of the specimens. This study shows that despite the antifungal effect of CS-salts in solution, a modification of PMMA resin with these CS-salts does not improve the antifungal properties of PMMA Denture Base Material.
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physical properties of polyamide 12 versus pmma Denture Base Material
BioMed Research International, 2014Co-Authors: Mieszko Wieckiewicz, Volker Opitz, Gert Richter, Klaus W BoeningAbstract:Objectives. Polyamide-12 (PA) is a flexible Material suited for Denture Bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity. Methods. PA specimens (Valplast) of mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine were measured using the CIE color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles, ) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling . Results. Tukey’s HSD test revealed statistically significant color changes of PA in red wine ( after 12 days, after 12 days) and coffee ( after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845 MPa and not affected by thermocycling (Tukey's HSD test, ). Dry specimens showed significantly decreased elasticity . Mean surface roughness (PA 0.20 μm, PMMA 0.28 μm) did not change significantly after thermocycling or storage (Mann-Whitney -test, ). Significance. PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.
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physical properties of polyamide 12 versus pmma Denture Base Material
BioMed Research International, 2014Co-Authors: Mieszko Wieckiewicz, Volker Opitz, Gert Richter, Klaus W BoeningAbstract:Objectives. Polyamide-12 (PA) is a flexible Material suited for Denture Bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity. Methods. PA specimens (Valplast) of mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine were measured using the CIE color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles, ) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling . Results. Tukey’s HSD test revealed statistically significant color changes of PA in red wine ( after 12 days, after 12 days) and coffee ( after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845 MPa and not affected by thermocycling (Tukey's HSD test, ). Dry specimens showed significantly decreased elasticity . Mean surface roughness (PA 0.20 μm, PMMA 0.28 μm) did not change significantly after thermocycling or storage (Mann-Whitney -test, ). Significance. PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.
Pekka K Vallittu - One of the best experts on this subject based on the ideXlab platform.
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effect of cellulose nanofiber content on flexural properties of a model thermoplastic injection molded polymethyl methacrylate Denture Base Material
Journal of The Mechanical Behavior of Biomedical Materials, 2020Co-Authors: Lippo V J Lassila, Tomohiro Kawaguchi, Hirono Baba, Shu Tashiro, Ippei Hamanaka, Pekka K VallittuAbstract:Abstract Cellulose nanofiber (CNF) made from wood-derived fiber is considered as a potential alternative reinforcing Material to conventional fibers. The aim of this study was to investigate the effect of CNF on the flexural properties of CNF-reinforced, injection molded, polymethyl methacrylate (PMMA) Denture Base Material. Test specimens were fabricated from a model thermoplastic Denture Base resin using the injection molding technique. The resin pellets were mixed with CNF (to obtain different weight percentages 5, 10, 15, and 23 wt%). PMMA without CNF served as the control (0 wt%). Prior to the testing, the test specimens (n = 12/group) were water-immersed at 37 °C water for 50 h. The flexural strengths and moduli of the specimens were determined using three-point bending tests. Statistical evaluation included a one-way analysis of variance and the Student-Newman-Keuls test (α = 0.05). The mean and standard deviation of flexural strengths with the addition of 0, 5, 10, 15 and 23% CNF were 49.4 (±0.7), 56.4 (±1.3), 63.5 (±2.0), 72.0 (±4.7), and 96.8 (±4.0) MPa, respectively. The mean and standard deviation of flexural modulus with the addition of the same concentrations of CNF were 1.31 (±0.02), 1.56 (±0.05), 1.99 (±0.14), 2.40 (±0.15), and 3.96 (±0.08) GPa, respectively. The flexural strengths and moduli of the CNF-reinforced PMMA were significantly higher than those of pure PMMA (p
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effect of rigid rod polymer filler on mechanical properties of poly methyl methacrylate Denture Base Material
Dental Materials, 2008Co-Authors: Annemaria Vuorinen, Scott R Dyer, Lippo V J Lassila, Pekka K VallittuAbstract:Abstract Objectives The aim of this study was to evaluate the mechanical properties of Denture Base Material with rigid rod polymer (RRP) particulate fillers. Methods Specimens were fabricated from autopolymerized polymethylmethacrylate Denture Base resin (Palapress Heraus-Kulzer) and RRP particles were used as fillers (Parmax Mississippi Polymer Technologies, Inc.). Five groups were tested: 0 wt% RRP, 10 wt% RRP, 20 wt% RRP, 30 wt% RRP, and 100 wt% RRP. Specimens were stored dry at room temperature for 2 days or in water at 37 °C for 44 days before testing until failure at a three point bending test (ISO 1567) for measuring flexural properties. The surface microhardness, water sorption, and solubility were also measured. Existence of interpenetrating polymer network (IPN) between filler and Denture resin was examined using solvent treatment and scanning electron microscopy (SEM). Results Specimens with RRP filler revealed higher flexural modulus, but the flexural strength decreased. Specimens with 30% RRP filler showed flexural strength of 67.4 MPa, whereas specimens without fillers gave strength of 93.9 MPa. The 100% RRP group revealed the highest flexural strength (305 MPa). Flexural strength of water-stored test specimens decreased in most groups when compared to dry specimens. Microhardness increased as a function of RRP filler. SEM micrographs revealed no IPN-network on the surface of RRP fillers. Addition of RRP fillers decreased the water sorption, whereas solubility was not affected. Significance This study revealed that although RRP polymer has good mechanical properties, addition of RRP to Denture Base resin as fillers did not increase mechanical properties. This was explained by lack of IPN-formation between RRP fillers and polymer matrix.
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bonding of resin teeth to the polymethyl methacrylate Denture Base Material
Acta Odontologica Scandinavica, 1995Co-Authors: Pekka K VallittuAbstract:The objective of this study was to compare bonding of acrylic resin teeth treated in various ways to the polymethyl methacrylate (PMMA) Denture Base Material. The joint surface of each acrylic tooth cured to heat-cured or autopolymerizing PMMA was either untreated, ground, or adjusted with mechanical retention. The bond to the PMMA was tested with a three-point loading test. To determine whether the bond failure was adhesive or cohesive, the fracture surfaces were analyzed visually and by scanning electron microscopy. The highest bond strength to both the heat-cured and the autopolymerizing PMMA was obtained by grinding grooves on the joint surface of an acrylic resin tooth before it was cured to the PMMA (p 0.05).
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reinforcement of acrylic resin Denture Base Material with metal or fibre strengtheners
Journal of Oral Rehabilitation, 1992Co-Authors: Pekka K Vallittu, Veijo LassilaAbstract:The effect of different metal and fibre strengtheners on the fracture resistance of polymethylmethacrylate was tested. Different types of commonly used metal wire and glass fibre, as well as carbon and aramid fibres, were used as strengtheners in test specimens. There were 21 groups, and each group contained 12 test specimens. Each metal strengthener had a beneficial effect on the fracture resistance of the polymethylmethacrylate (P less than 0.001-0.01). Some fibres, which were silanized for better adhesion, also had strengthening properties.