Mechanical Characteristics of (TiO2-ZnO)/PMMA Nanocomposites for Dentures

Mechanical properties (impact strength, compressive strength and flexural strength) have been studied for (Polymethyl-methacrylate (PMMA)) polymer reinforced with nano (TiO2+ZnO) (0 v%, 1 v%, 2 v%, 3 v%, 4 v% and 5 v%). Ultrasonic dispersion technique was used to prepare the nanocomposites samples, follow with cold casting technique using Teflon molds standard conditions. Charpy impact instrument was used to measure the impact strength, the compressive strength of each sample which was tested in newton units using digital compression tester (TinusOlsen: H50KT, England), while flexural strength can be found from mathematical formulas which depend on the impact strength, compressive strength and flexural strength. Results show that values increase in 1 v%, then decrease alternately by (2 v%, 3 v%, 4 v%, and 5 v%), while 0 v% is the less value of volume fraction of fillers. Young modules values increase alternately by the volume fraction of fillers until 2 v%, while if it is higher and lower than 2 v% it decreases the modulus of elasticity.

Silver nanoparticle incorporation effect on mechanical and thermal properties of denture base acrylic resins

ABSTRACT Objective The aim of the present study was to evaluate the mechanical and thermal characteristics of two denture base acrylic resins containing silver nanoparticles (AgNPs). Material and Methods Two different acrylic denture base resins (heat-polymerized and microwave polymerized) containing 0.3, 0.8 and 1.6 wt% AgNPs were evaluated for flexural strength, elastic modulus and impact strength. The glass transition temperature (Tg) and relative heat capacity (Cp) of the samples were determined from the Differential Scanning Calorimetry (DSC) results. For statistical analysis, two-way ANOVA and Tukey-HSD tests were performed. Results Addition of 0.8% and 1.6% AgNPs in microwave-polymerized resin significantly decreased the transverse strength and elastic modulus. In terms of impact strength, the addition of AgNPs has no effect on both resin groups. Glass transition temperature (Tg) was decreased with the addition of AgNPs for both denture base resins. Conclusions The incorporation of AgNPs, generally used for antimicrobial efficiency, affected the transverse strength of the denture base acrylic resins depending on the concentration of nanoparticles. Tg was decreased with the addition of AgNPs for both denture base resins.

Evaluation and comparison of transverse and impact strength of different high strength denture base resins.

Aim: The present study was undertaken to evaluate and compare the impact strength and transverse strength of the high‑impact denture base materials. A conventional heat polymerized acrylic resin was used as a control. Materials and Methods: The entire experiment was divided into four main groups with twenty specimens each according to denture base material selected Trevalon, Trevalon Hi, DPI Tuff and Metrocryl Hi. These groups were further subgrouped into the two parameters selected, impact strength and flexural strength with ten specimens each. These specimens were then subjected to transverse bend tests with the help of Lloyds instrument using a three point bend principle. Impact tests were undertaken using an Izod–Charpy digital impact tester. Results: This study was analyzed with one‑way analysis of variance using Fisher f‑test and Bonferroni t‑test. There was a significant improvement in the impact strength of high‑impact denture base resins as compared to control (Trevalon). However, in terms of transverse bend tests, only DPI Tuff showed higher transverse strength in comparison to control. Trevalon Hi and Metrocryl Hi showed a decrease in transverse strength. Conclusions: Within the limits of this in vitro study, (1) There is a definite increase in impact strength due to the incorporation of butadiene styrene rubber in this high strength denture base materials as compared to Trevalon used as a control. (2) Further investigations are required to prevent the unduly decrease of transverse strength. (3) It was the limitation of the study that the exact composition of the high‑impact resins was not disclosed by the manufacturer that would have helped in better understanding of their behavior.

Quality Testing and Analysis of Manual Wheelchairs: Based on ISO 7176-8 / 中国康复理论与实践

@#Objective To measure the quality of manual wheelchairs made in China. Methods 20 wheelchairs was tested with ISO 7176-8, focused on the static strength, impact strength and fatigue strength. Results 8 (40%) wheelchairs passed the test. Conclusion The fatigue strength is the key factor of the wheelchair quality.

Quality Testing and Analysis of Manual Wheelchairs:Based on ISO 7176-8 / 中国康复理论与实践

Objective To measure the quality of manual wheelchairs made in China. Methods 20 wheelchairs was tested with ISO 7176-8, focused on the static strength, impact strength and fatigue strength. Results 8 (40%) wheelchairs passed the test. Conclusion The fa-tigue strength is the key factor of the wheelchair quality.

Assessment of the impact strength of the denture base resin polymerized by various processing techniques.

Aim : To measure the impact strength of denture base resins polymerized using short and long curing cycles by water bath, pressure cooker and microwave techniques. Materials and Methods: For impact strength testing, 60 samples were made. The sample dimensions were 60 mm × 12 mm × 3 mm, as standardized by the American Standards for Testing and Materials (ASTM). A digital caliper was used to locate the midpoint of sample. The impact strength was measured in IZOD type of impact tester using CEAST Impact tester. The pendulum struck the sample and it broke. The energy required to break the sample was measured in Joules. Data were analyzed using Student's " t" test. Results: There was statistically significant difference in the impact strength of denture base resins polymerized by long curing cycle and short curing cycle in each technique, with the long curing processing being the best. Conclusion: The polymerization technique plays an important role in the influence of impact strength in the denture base resin. This research demonstrates that the denture base resin polymerized by microwave processing technique possessed the highest impact strength.

Effect of Glass Fiber And Silane Treated Glass Fiber Reinforcement On Impact Strength Of Maxillary Complete Denture.

Background and objectives : The fracture of acrylic maxillary complete dentures is a commonly seen clinical problem which usually occurs due to heavy occlusal forces or accidental damage.The objectives of the study were to measure the impact strength of maxillary complete dentures fabricated with high impact acrylic resin and to evaluate the effect of woven E-glass fiber and silane treated glass fiber reinforcement on the impact strength of the Maxillary complete dentures. Methods :One commercially available heat cured acrylic resin (Trevalon HI) was selected. Preimpregnated woven E-glass fibers (Stick Net) and Silane treated glass fibers were used to reinforce ten maxillary complete dentures each. Ten unreinforced complete dentures served as the control group. The impact strength in Joules of the dentures were measured with a falling-weight impact test. Results : The mean impact strength of the control dentures was 75.22+/ - 10.392 J at crack initiation, and 84.62+/- 11.495 J at complete fracture. The mean impact strength of dentures reinforced with preimpregnated woven E-glass fibers was 165.91+/- 12.929 J at crack initiation, and 187.06+/- 17.972 J at complete fracture. The mean impact strength of dentures reinforced with silane treated glass fibers was 112.30+/- 8.709 J at crack initiation, and at complete fracture was 126.43 +/- 8.709 J. Interpretation and Conclusion :The impact strength of maxillary complete dentures fabricated with high impact acrylic resin increased significantly after reinforcement with preimpregnated woven Eglass fibers and silane treated glass fibers. The best improvement, however , was obtained by preimpregnated woven Eglass fibers.

The Effect of Chemical (Glutaraldehyde ) And Microwave Sterilization On Impact Strength of Autopolymerizing ( PMMA ) Resins.

This study evaluated the effect of sterilization methods on the Impact strength of a self cured resins. A 10 hours immersion in 2 % alkaline glutaraldehyde, 15 minute exposure to microwaves energy was employed as a sterilization procedure. Storage in water for 10 hours was used as control. For each procedure 10 specimens were used. Results indicated that impact strength of the two groups did not change significantly as compared to control. Microwave sterilization can be opted as effective method and time saving procedure than immersion in chemical solution.

Impact strength of denture base and reline acrylic resins subjected to long-term water immersion

Water may influence the mechanical properties of the acrylic resins. Thus, the effect of water storage on the impact strength (IS) of one denture base (Lucitone 550 - L) and four reline resins (Tokuyama Rebase II - T; UfiGel Hard - U; Kooliner - K; New Truliner - NT) was evaluated. Bars of L were made (60 x 6 x 2 mm) and relined (2 mm) with T, U, K, NT and L. Intact specimens of each material (60 x 6 x 4 mm) were also fabricated for comparative purposes. Specimens were submitted to Charpy impact tests without water storage (control) and after immersion in water for 7, 90 and 180 days. Data (kJ/m²) analyzed by two-way ANOVA and Tukey's test (p=0.05) revealed that after 90 days, U exhibited an increase in the IS (0.93) compared to 7 days (0.58). K (1.48) and L/K (7.21) exhibited a decrease at the 7-day period (1.01 and 3.23, respectively). NT (0.60) showed an increase in the IS after 180 days (1.52), whereas L/NT (7.70) showed a decrease (3.17). Water immersion improved the IS of U and NT, and decreased the IS of K, L/K, and L/NT. Water may affect differently the IS of acrylic resins and, consequently, the resistance to fracture of relined denture bases.

A água pode influenciar as propriedades mecânicas das resinas acrílicas. Assim, o efeito do armazenamento em água na resistência ao impacto (RI) de uma resina para base de prótese (Lucitone 550-L) e quatro materiais reembasadores (Tokuyama Rebase II-T; UfiGel Hard-U; Kooliner-K; New Truliner-NT) foi avaliado. Barras da resina L foram confeccionadas (60 x 6 x 2 mm) e reembasadas (2 mm) com T, U, K, NT e L. Amostras não reembasadas de cada material também foram confeccionadas (60 x 6 x 4 mm) para fins comparativos. As amostras foram submetidas aos testes de impacto tipo Charpy sem armazenamento (controle) e após imersão em água por 7, 90 e 180 dias. Os resultados (kJ/m²) analisados por meio de ANOVA dois fatores e teste de Tukey (p=0,05) revelaram que, após 90 dias, U exibiu aumento na RI (0,93) comparado com 7 dias (0,58). K (1,48) e L/K (7,21) exibiram diminuição no período de 7 dias (1,01 e 3,23, respectivamente). NT (0,60) apresentou aumento na RI após 180 dias (1,52), enquanto L/NT (7,70) apresentou redução (3,17). A imersão em água melhorou a RI de U e NT e diminuiu a RI de K, L/K, e L/NT. A água pode afetar de maneira diversa a RI das resinas acrílicas e, consequentemente, a resistência à fratura das bases de próteses reembasadas.

Study on disinfection effectiveness and properties of acrylic resin via microwave irradiation sterilization / 中国实用护理杂志

Objective The purpose of this study was to evaluate the disinfection effectiveness and properties of acrylic resin via microwave irradiation. Methods Forty acrylic resin base dentures fabricated in a standardized procedure were chosen and divided into Group A,B,C and D randomly. Group A,B and C were immersed in 200ml distilled water and submitted to microwave irradiation at 700W for 3,4,5 minutes individually. Group D was used as positive control. Bacteria specimens from each group were got for culture and numbers were calculated. Then the four groups were tested for the flexural strength and impact strength by universal test machine before and after microwave irradiation sterilization. Results The germicidal ratio of Group B was more than 90% ,while the ratio of group C was 100%. There was no significant difference in flexural strength and impact strength between group C and group D. Conclusions Microwave irradiation for 5 minutes at 700W produced sterilization of dentures contaminated with all bacteria whereas the denture strength is not affected. Microwave irradiation at 700W solution for 5 minutes was effective to sterilize acrylic resin base dentures.

Polytetrafluorethylene added to acrylic resins: mechanical properties

The addition of different polymers, such as polytetrafluorethylene (PTFE), to denture base resins could be an option to modify acrylic resin mechanical properties. This study evaluated the surface hardness, impact and flexural strength, flexural modulus and peak load of 2 acrylic resins, one subjected to a long and another subjected to a short polymerization cycle, which were prepared with or without the addition of 2 percent PTFE. Four groups were formed according to the polymerization cycle and addition or not of PTFE. Forty specimens were prepared for each test (10 per group) with the following dimensions: hardness (30 mm diameter x 5 mm thick), impact strength (50 x 6 x 4 mm) and flexural strength (64 x 10 x 3.3 mm) test. The results of the flexural strength test allowed calculating flexural modulus and peak of load values. All tests were performed in accordance with the ISO 1567:1999 standard. Data were analyzed statistically by ANOVA and Tukey's test with the level of significance set at 5 percent. No statistically significant differences (p>0.05) were found for surface hardness. Flexural strength, impact strength and peak load were significantly higher (p<0.05) for resins without added PTFE. The flexural modulus of the acrylic resin with incorporated 2 percent PTFE polymerized by long cycle was significantly higher (p<0.05) than that of the other resins. Within the limits of this study, it may be concluded that the addition of PTFE did not improve the mechanical properties of the evaluated acrylic resins.

A adição de diferentes polímeros como o politetrafluoretileno (PTFE) às resinas para base de próteses removíveis pode ser uma opção para modificar as propriedades mecânicas das resinas acrílicas. Este estudo avaliou a dureza de superfície, a resistência ao impacto e à flexão, o módulo flexural e a carga de ruptura de duas resinas acrílicas, uma submetida ao ciclo longo e a outra ao ciclo curto de polimerização, as quais foram preparadas com ou sem a adição de PTFE a 2 por cento. Quatro grupos foram formados de acordo com os ciclos de polimerização e a adição ou não de PTFE. Quarenta espécimes foram preparados para cada teste (10 espécimes por grupo) com as seguintes dimensões: dureza de superfície (30 mm diametro x 5 mm espessura), resistência ao impacto (50 x 6 x 4 mm), resistência à flexão (64 x 10 x 3,3 mm). O módulo flexural e a carga de ruptura foram calculados a partir dos valores obtidos no teste de resistência à flexão. Todos os testes foram realizados em conformidade com a Norma ISO 1567:1999. Os dados foram submetidos à análise de variância e teste de Tukey com nível de significância de 5 por cento. Não foram encontradas diferenças estatisticamente significantes (p>0,05) para dureza de superfície. Os valores de resistência à flexão, resistência ao impacto e carga de ruptura foram maiores para as resinas sem a adição de PTFE (p<0,05). O valor do módulo flexural da resina acrílica com adição de PTFE a 2 por cento, polimerizada por ciclo longo, foi maior do que as outras resinas (p<0,05). Dentro das limitações deste estudo, pode-se concluir que a adição de politetrafluoretileno não melhorou as propriedades mecânicas das resinas acrílicas avaliadas.

Comparison of the properties of three denture base materials treated and untreated by hydraulic pressure cooker / 实用口腔医学杂志

Objective:To compare the properties of three kinds of denture base materials treated and untreated by hydraulic pressure cooker. Methods: The impact strength, flexural strength, flexural elastic modulus and color difference roughness of three denture base materials, Kunshan Rijin(KR),GC UNIFAST Trad(GC), Shanghai Zhangjiang(SZ), were measured in vitro. All results were statistically analyzed with SPSS software to have ANOVA and Tamhane's T2 tests, α=0.05. Results: Comparison of the same materials between the treated materials and the untreated materials by hydraulic pressure cooker: there were significant statistical differences of impact strength for all the materials. There were significant statistical differences of color difference for KR and SZ. Comparison of the three materials: impact strength, GC>SZ>KR;flexural strength, KR>SZ>GC;flexural elastic modulus, KR>SZ>GC;roughness, GC>KR>SZ. Conclusion: The properties of denture base materials treated by hydraulic pressure cooker are good.